Edited by
Kendall Preston. Jr. Carnegje-Mellon University Pittsburgh, Pennsylvania
Kenneth J. W. Taylor Yale University School of Medicine New Haven, Connecticut
Steven A. Johnson Mayo Foundation Rochester, Minnesota
and
William R. Ayers Georgetown University School of Medicine Washington, D. C.
Plenum Press· New York and London
Library of Congress Cataloging in Publication Data
Main entry under title:
Medical imaging techniques.
"Based on the proceedings of the Engineering Foundation Conference held in Henniker, New Hampshire, August 15-20, 1976."
Includes indexes. 1. Diagnosis, Radioscopie - Congresses. 2. Imaging systems in medicine­
Congresses. I. Preston, Kendall, 1927- H. United Engineering Trustees, inc., New York. [DNLM. 1. Radionuclide imaging - Methods - Congresses. 2. Tomog­ raphy, Computerized axial - Congresses. WN445 M489 1976] RC78.M34 616.07'57 79-4424 ISBN-13: 978-1-4684-3488-0 e-ISBN-13: 978-1-4684-3486-6 DOI: 10.1007/978-1-4684-3486-6
Based on the proceedings of the Engineering Foundation Conference held in Henniker, New Hampshire, August 15-20, 1976.
This book was prepared with the support of NSF Grant APR 76-24161. However, any opinions, findings, conclusions and/or recommendations herein are those of the authors and do not necessarily reflect the views of NSF.
© 1979 United Engineering Trustees
Plenum Press, New Y ork A Division of Plenum Publishing Corporation 227 West 17th Street, New York, N.Y. 10011
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, e1ectronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission
Preface
The need for a book on medica1 imaging techniques became evi­ dent to the editors of this vo1ume at the 1976 Engineering Founda­ tion Conference on Non-Invasive Medica1 Diagnosis. This conference treated imaging of the thorax, abdomen, brain, and extremities using ultrasound, radiology, computed tomography, and nuc1ear medi­ cine. During 1976 and 1977 the editors solicited participants in the conference for contributions to this vo1ume. Other sources were also sought in special areas of interest in medical imaging beyond those individua1s who had been conference participants. Most of the writing and editing was done in late 1977 and in 1978 resu1ting in this 25-chapter book which is organized into sections on (1) Systems Considerations, (2) C1inical Results, (3) Research Topics, and (4) Tutorials. A short survey of the book is contained in the Introduction.
The editors wish to acknowledge the United States National Science Foundation, particularly J. C. Aller, Program Manager, for partial financia1 support of the conference and of the publication of this book under Grant APR76-24161. The exce11ent typing services of Caroline Wadhams's organization (Report Production Associates, Cambridge, Massachusetts) and her staff, particu1ar1y Susan Dunham, are acknowledged as weIl as the efforts of Meg Grant and Winnie Garcia (Tucson, Arizona) who assisted with the subject index. The splendid cooperation of the staff of Plenum Press, in particular Stephen Dyer (Assistant Managing Editor) and Derrick Mancini (Editor), has been inva1uab1e.
K. Preston, Jr. K. J. W. Taylor S. A. Johnson W. R. Ayers
v
Contents
Introduction .......•.........•.....•. xvii
SYSTEMS CONSIDERATIONS
Health Planning for a New Technology: Computerized Tomography Planning Issues in 1975 and 1976
Patricia A. Gempel
l. 2. 3.
4.
5.
6.
Introduction . Information Needs of Health Planners Effect of CT on Alternative Diagnostic Neurologie Procedures .• .: .• . Health Planning Issues . ... 4.1 Equipment Selection Criteria 4.2 Early Instrument Obsolescence 4.3 Diffusion of CT Scanning Systems 4.4 Geographie Location . . Planning Approach. '" 5.1 Areawide Planning for CT Scanning Systems 5.2 Assessment of Areawide Need . • 5.3 Guidelines for Procurement of Initial CT Scanner 5.4 Guidelines of Procurement of Additional Scanners 5.5 Body Scanner Applications References. .
vii
3 5 5 6 6 6 7 7 7 8
10 10 11
viii CONTENTS
An Overview of Government Regulation of the Use of Computed Tomography through 1978
Patricia A. Gempel and Jane B. Hetzger
l. 2.
3. The Social Security
Standards - The Food and Drug
5. 6. 7.
Hultiple Endpoints in the Assessment of Non-Invasive Technology
W. R. Ayers
Diseases . . . . . . 1.2 Assessment of Hedical Technology
2. Levels of Technology . . . . . . 3. Health Services Delivery Systems 4. Conclusion 5. References. . . . .
The Evaluation of Diagnostic Tests S. N. Rasmussen
l. 2.
3. 4. 5. 6. 7.
Introduction . . . . . . . . . . . . . . . . . . Hethods of Procedure . . . . . . . . . . . . . . 2.1 The Diagnostic Information Obtained by the
Investigation .............. . 2.2 The Therapeutic Consequence of Establishing
Excluding a Diagnosis . . . . . . . 2.3 Discomfort and Risk to the Patient 2.4 Economic Cost ........ . Evaluation of Diagnostic Information The Direct Hethod The Indirect Hethod Summary References .
or
37 38
CONTENTS
The Impact of Technology on Health Care Productivity G. B. Devey
l. 2. 3.
Introduction . . . . . . . . . . Pitfalls of Inflexible Policies Impact of Current Technology 3.1 Ultrasound 3.2 Nuclear Medicine 3.3 New Skills
4. 5.
CLINICAL RESULTS
Scintigraphy, Ultrasound, and CT Scanning of the Liver K. J. W. Taylor, D. Sullivan, J. Simeone, A. T. Rosenfield
1. Introduction . 1.1 Nuclear Medicine Imaging 1.2 Ultrasound Imaging and Computed Tomography
2. Comparison . . 2.1 Metastases 2.2 Diffuse Abnorrnalities 2.3 Ascites 2.4 Biliary Tree 2.5 Gallstones
3. Discussion 4. References
W. F. SampIe
1. Introduction ..... 2. Materials and Methods 3. Results 4. Discussion .. . 5. Conclusion .. . 6. Acknowledgements 7. References.
A Preliminary Report on Computed Tomography of the Thorax and Abdomen
R. J. Alfidi
47 48 49 50 50 50 51 52
55 55 56 56 61 67 69 69 70 73 76
79 81 82 85 87 87 88
91 91
x
3. Results 3.1 Liver . · 3.2 Effusions 3.3 Pancreas 3.4 Kidneys · 3.5 Aorta . · 3.6 Ga11bladder and Bile Ducts 3.7 Retroperitoneal Abnormalities 3.8 Mediastinal Masses 3.9 Bony Abnormalities 3.10 Breast
4. Discussion
1. 2.
3. 4. 5.
Introduction • • • • • • • • • . • • • • Accepted Uses of Ultrasound in Detection 2.1 Gynecological Tumors 2.2 Abdominal Lymph Nodes • 2.3 Retroperitoneal Masses 2.4 Tumors of the Pancreas 2.5 Other Gastrointestinal Tumors 2.6 Liver Metastases 2.7 Neoplasms of the Kidney ••• 2.8 The Thyroid Gland ••.••. Analysis of Ultrasound Patterns of Tumors Diagnostic Ultrasound in the Management of Refer ences • •• .
Computed Tomography of the Liver and Biliary Tract S. Sagel and R. J. Stanley
1. Introduction.. •••• • •.•• 2. The Normal Liver and Biliary Tract • 3. The Abnormal Liver and Biliary Tract
3.1 Space-Occupying Hepatic Lesions 3.2 Jaundice •••.. 3.3 Gallbladder Disease
4. Discussion 5. References. •
3.1 Normal Liver
100 100 101 101 103
105 105 106 107 107 108 110 110 110 111 112 113 114
117 117 118 118 119 120 120 122
123 123 124 124
CONTENTS
3.2 Tumors 3.3 Cysts. 3.4 Cirrhosis 3.5 Abcess 3.6 Obstructive Jaundice
xi
124 126 126 126 126 131 131 132 132 133
4.1 Contrast Agents .. . 4.2 CT Biopsy ..... . 4.3 Transhepatic Cho1angiography
5. References ........... .
Echographie Diagnosis of Lesions of the Abdominal Aorta and Lyrnph Nodes
A. K. Freimanis
2.1 Modern Echographie Procedure 136 2.2 Echographie Measurement 138 2.3 Echographie Measurernents in the Management of
Aneurysms 138 2.4 Method of Examination 138 2.5 Diagnostic Procedure 141 2.6 A Few Pitfa11s 142 2.7 Differential Diagnosis of Large Abdominal
Lyrnph Nodes ... 142 2.8 Indications for Procedure 142 2.9 Reliability . ... 143 2.10 Thoraeie Aortic Aneurysms 143 2.11 Inferior Vena Cava 144
3. Retroperitonea1 Lyrnph Node En1argement 144 3.1 Deve10pment of Examination Procedure 145 3.2 Acoustic Nature of Lyrnph Nodes 145 3.3 Distribution . . . . . . . . 147 3.4 Out1ining of Radiation Ports 148 3.5 Indications. . . . . 150 3.6 Differential Diagnosis 152
4. Summary . . . . 152 5. Acknow1edgements 152 6. References 153
xii CONTENTS
RESEARCH TOPICS
The Use of Computerized Tomography in the Diagnosis of Pu1monary Nodu1es
W. R. Ayers and H. K. Huang
1. Introduetion . . . . . • . • . . . . .• 155 2. Standard Management of the Solitary Pu1monary Nodu1e 156 3. The Use of CT - Material and Methods . • . . • . • 157
3.1 Read a CT Sean from Magnetie Tape or Disk . •. 159 3.2 Iso1ate a Patho1ogiea1 Region in the CT Sean 159 3.3 Generate the Frequeney Distribution and Histogram 159 3.4 Determine Patho1ogiea1 Boundaries 160 3.5 Estimate Vo1ume . . . . • . 160 3.6 Produee Subtraetion Images 160
4. Resu1ts • . • . . • . . . . . . 160 4.1 An Illustrative Case Study 161 4.2 Comment 163
5. Summary 163 6. Referenees. 164
Image Proeessing of Computerized Tomographie Seans J. A. Horton, C. W. Kerber, and J. M. Herron
1. Introduetion . . . . . 1.1 Limitations of CT Seanning 1.2 Lirnitations of Human Visua1
2. Materials and Methods 3. The Sigma Sean Image 4. Speeifie Case Studies 5. Diseussion . . 6. Aeknow1edgements 7. Referenees .
Determination of Organ Volume S. N. Rasmussen
1. 2. 3.
. .
175 177 179 181 181 182 183
CONTEtl"TS
Three-Dimensiona1 Dynamic Imaging of the Heart, Lungs, and Circulation by Roentgen-Video Computed Tomography
R. A. Robb
1. Introduction 2. Methods 3. Resu1ts 4. Discussion 5. Summary 6. Acknow1edgements 7. References ...
A Digital Moving Target Indicator System for Detection of Intracrania1 Arterial Echoes
R. W. Barnes
1. Introduction 2. System Description 3. Resu1ts 4. Conclusions 5. References.
Relationship of Images of Acoustic Refractive Index and Attenuation to Tissue Types within Excised Fema1e Breast
J. F. Green1eaf and S. A. Johnson
1. Introduction 2. Method of Procedure 3. Conclusion. • . 4. Acknow1edgements. .
Feasibi1ity of NMR Zeugmatographic Imaging of the Heart and Lungs
P. C. Lauterbur
l. 2. 3.
4. 5. 6.
Introduction Potential App1ications in Medica1 Diagnostic Preliminary Experiments . . . . . • . . 3.1 NMR Properties of Lung Tissue ... 3.2 NMR Properties of Myocardia1 Tissue Physica1 Lirnitations Acknowledgements References . . . . .
Imaging
xiii
199 200 201 203 204
205 206 207 207
xiv CONTENTS
Otto H. Schmitt
TUTORIALS
1. 2.
3. 4.
Introduction Basic Princip1es. •• 2.1 Frequencies Emp10yed 2.2 Production of Ultrasound 2.3 Intensity of Ultrasound • 2.4 The Ref1ection Process 2.5 Resolution of Ultrasound Systems 2.6 Tissue Attenuation and TGC 2.7 Types of Reflectors •••• 2.8 Gray-sca1e Systems • . .• . 2.9 Scanning Techniques in Gray-sca1e U1trasonography 2.10 Recording Systems •••. 2.11 Real-Time Ultrasound Systems Conc1usion References • •
Nuclear Medicine Imaging L. Kaufman
1. Introduction . . . . . 1.1 lmaging Moda1ities 1.2 Detection Systems
2. The Imaging Problem 2.1 Resolution . . . . 2.2 Imaging Performance
219 220 222 223 224 225 226 227 228
231 232 232 232 234 235 238 240 241 244 247 248 251 259 260
263 263 264 267 267 268
CONTENTS xv
3. Imaging Concepts • . . . . . . . . . . . . . . . .. 269 3.1 Sources of Noise in the Nuclear Medicine Image 270
4. The High Purity Germanium (HPGe) Camera 274 4.1 Comparative Sensitivity 276 4.2 Contrast Resolution 277 4.3 Comparative Imaging 279
5. Tracers 279 6. Discussion 283 7. References 284
Algorithms in Computerized Tomography J. M. S. Prewitt
1. Introduction. . . • . . . . . . 1.1 The Reconstruction Problem 1.2 The Reconstruction Paradigm
2. Reconstruction Algorithms 2.1 Transform Methods - Parallel Geometry 2.2 Transform Methods - Divergent Geometry 2.3 Series Expansion Methods
3. Comparison of A1gorithms 4. Impact on Medicine 5. Summary 6. References.
Scanning Methods and Reconstruction A1gorithms for Computerized Tomography
H. K. Huang and R. S. Led1ey
1. Introduction 2. Scanning Modes . . .
.
. . 2.1 Translation and Rotation Mode Using a Pencil
Thin Co11imated X-ray Beam . 2.2 Translation and Rotation Mode Using a Fan-Beam
X-ray Technique . . . . . . . 2.3 Rotation Mode Using a Larger Fan Beam
3. Picture Reconstruction A1gorithm .. 3.1 Parallel A1gorithm: A1gebraic, Convo1ution
and Fast Fourier Transformer 3.2 Fan Algorithm
4. Conc1usion 5. References.
K. Preston, Jr.
2.1 Investigations by Mountford and We11s
287 288 289 290 294 296 297 303 306 308 311
313 314
xvi
3. Signal Analysis Theory and Methods 3.1 Signal Regimes 3.2 Tissue Signatures
4. Experimental Data 4.1 Materials and Methods 4.2 Transducer Calibration 4.3 In Vivo Recording . 4.4 Case Study (Human) 4.5 Case Study (Animal)
5. Acknowledgements 6. References
CONTENTS
333 333 334 337 337 339 340 349 351 353 354
355
359
363
Inkoduction
This book presents recent advances in the major medical imaging modalities: (1) traditional radiography, (2) computed x-ray tomography, (3) ultrasonography, and (4) nuclear medicine imaging using radionuclides. Chapters have been written by both practi­ tioners and researchers in radiology as weIl as by authors covering the engineering aspects of medical image generation, processing, and display. The book also provides five tutorial chapters on the fundamentals of ultrasound, computed tomography, nuclear medicine imaging, and electronic signal and image analysis.
Medical imaging is a rapidly evolving field, especially in those aspects influenced by advances in digital computer technology. Thus no book on this subject can be entirely up-to-date. The emphasis in this volume is on classic advances in the field which have taken place during the decade of the 1970s. This decade has seen the rapid adoption in the hospital, clinic, and health center of new imaging instrumentation in ultrasound, x-ray tomography, and nuclear medicine. The major advance in ultrasound is in gray-scale display (Figure 1). Display techniques have also rapidly advanced in computed radiography and x-ray tomography as has resolution and sensitivity (Figures 2-6). Nuclear medicine imaging has also ad­ vanced with the introduction of computerized displays, more sensi­ tive detectors, and computed emission tomography (see, for example, the chapter by L. Kaufman). Finally, we have just seen the intro­ duction by industry of the entirely new technique of nuclear mag­ netic resonance imaging (Figure 7).
We feel indeed fortunate to have obtained outstanding chapters illustrating clinical applications of these new imaging techniques and instruments. These chapters have been provided by K. J. W.
xvii
Fig. 1. Gray-level displays of sixteen sequentia1 ultrasound B-scans of the breast taken at approximate1y l-second intervals at different longitudinal positions. (Courtesy G. Baum, Albert Einstein College of Medicine, New York.)
INTRODUCTION xix
Fig. 2. Computed radiogram of the head. (Courtesy General Electric Co., Milwaukee.)
(A) (B)
Fig. 3. Two different displays of the same computed x-ray tomogram using different level and window settings. (A) Structure of the spine, ribs, heart, and musculature (level: 0, window: 300). (B) Structure of the lungs (level: -523, window: 1000). (Courtesy General Electric Co., Milwaukee.)
xx INTRODUCTION
(A) (B)
Fig. 4. (A) Gomputed radiogram display permitting seleetion of angulated sean through seleeted vertebra. ( E ) Magnified view of seleeted angulated sean with level 191 and window 1000 to permit examination of bone strueture. (Courtesy General Eleetrie Co., Milwaukee. )
(A) (B)
Fig. 5. Computer eonstruetion and display of both lateral seetion (A) and longitudinal seetion (E ) from 21 previously eomputed trans­ verse tomographie seetions taken axially at lOrnrn intervals. (Courtesy General Eleetrie Co., Milwaukee.)
INTRODUCTION xxi
(A) CB)
Fig. 6. Demonstration of spatial and contrast resolution in com­ puted x -ray tomography using the General Electric gray-white phantom (model 3 ). Two different displays of the same tomogram show (A) contrast resolution to 0.2% for large ( ~ lcm) structures displayed with level 0 and window 40 and (E) spatial resolution of 1.5mm structures at 3.0% contrast displayed with level -15 and window 40. The small wedge-shaped struc ture is water density. (Courtesy General Electric Co., Milwaukee.)
Fig. 7. Nuclear magnetic resonance ima ge of the human head. (Courtesy EMI Medical, Ltd., Great Britain.)
xxii INTRODUCTION
Taylor, W. F. Sample, R. J. Alfidi, A. K. Freimanis, and S. Sagel.* These authors have emphasized the comparative aspects of these imaging modalities. Some have furnished flow-charts of their multi-modality imaging protocols for both examination and diag­ nosis.
Besides these chapters on clinical results there are also chapters by the biomedical engineering community on current research. It is hoped that these research chapters will ass ist the reader in evaluating future trends which are clearly pointing towards further sophistication in diagnostic sensitivity, specificity, and produc­ tivity for the decade of the 1980s. In this section of the book the chapter by W. R. Ayers and H. K. Huang and the chapter by J. A. Horton, C. W. Kerber, and J. M. Herron provide some of the first evidence that computer generated (or displayed) tissue signatures may be used in the determination of pathology. (Horton has received the 1978 Cornelius G. Dyke prize of the Arnerican Society of Neuro­ radiology for his work.) R. W. Barnes illustrates methods of em­ ploying ultrasound for the purpose of determining blood flow in the cerebral arteries and S. N. Rasmussen discusses its use in cal­ culating organ volume. J. F. Greenleaf and S. A. Johnson report on progress in computed ultrasound tomography particularly as regards imaging of the breast. o. H. Schrnitt predicts tomographie imaging using the spatial variations in the electrical impedance of tissue. R. A. Robb describes progress in the Mayo Foundation DSSR project in real-time tomographie imaging of the thorax. Finally, the basics of nuclear magnetic resonance imaging in determining the properties of lung and myocardial tissue are reported by P. C. Lauterbur along with initial results in nuclear magnetic resonance imaging.
The tutorial chapters have been added so as to provide basic reference material which not only elucidates the basic physical principles of medical imaging modalities but also surveys funda­ mental physical progress in each modality with a broad perspective. K. J. W. Taylor discusses the generation of ultrasonic pulses, methods of ultrasound image formation from pulse echoes, ultra­ sound image display and interpretation. His chapter also reviews some of the new real-time scanning mechanisms which use phased arrays and sec tor scanners. L. Kaufman presents the basic principles of nuclear medicine imaging, reviews the use and selec­ tion of radionuclides, discusses the meaning of both spatial and spectral resolution, and introduces new results obtained using his high purity germanium camera. The tutorial chapters on computed tomography by J. M. S. Prewitt and also by H. K. Huang and R. S.
*Full addresses are given for all authors in the Appendix.
INTRODUCTION xxiii
Ledley catalog and discuss a multiplicity of reconstruction algo­ rithms using illustrations obtained from mathematical phantoms as weIl as reviewing tomographic scanning modes and beam geometries, respectively. Finally, K. Preston describes the fundamentals of electronic signal processing with respect to the generation of tissue signatures in ultrasound imaging.
As a counterbalance to the enthusiasm generated for the advances in diagnostic capability provided by modern medical imaging, we cannot disregard the quest ions of both medical ad­ ministrators and the user community concerning the cost-effective­ ness of the new (and often very expensive) instrumentation which has proliferated in the 1970s. Thus at the very outset of this book there are five chapters concerned with the medical systems problems faced in the procurement and use of medical imaging in­ strumentation and the impact of this procurement and use on health care and health management. The chapters by P. A. Gempel and J. B. Metzger review the impact of such government regulations as the National Health Planning and Resources Development Act, the Radia­ tion Control for Health and Safety Act of 1968, and the Medical Device Amendments of 1976 especially as regards the development of national guidelines for the procurement, installation, and use of CT scanners. The references in these chapters are an invaluable chronicle of the effect of government regulation on the use of modern imaging instrumentation. The chapters by W. R. Ayers and G. B. Devey discuss types of new medical technology and methods of assessing costs, benefits, and productivity, respectively. Finally, S. N. Rasmussen presents an analytical treatment, based upon prob­ ability theory, of the evaluation of diagnostic tests. He provides specific illustrations of performance evaluation using both in­ direct and direct methods of assessment as regards the detection of pancreatic cancer using images generated by ultrasound.
In summary, it is our hope that this book is sufficiently catholic to satisfy the need of the reader who desires a broad treatment of modern medical imaging and sufficiently comprehensive and analytical to satisfy the specialist. Assembling the chapters which are presented in the following pages and participating in the Engineering Foundation Conference on Non-Invasive Medical Diagnosis wherein some of this material was originally presented was a most worthwhile learning experience for all of the editors. It is our hope that the reader will benefit likewise.
19 February 1979 Kendall Preston, Jr. New Haven, Connecticut Senior Editor
HEALTH PLANNING FOR A NEW TECHNOLOGY: COMPUTERIZED TOMOGRAPHY
PLANNING ISSUES IN 1975 and 1976
Patricia A. Gempel
Cambridge, Massachusetts
1. INTRODUCTION
Public Law 93-641 divided the United States into just over 200 Health System Agencies (HSA's) with several irnportant and broad­ based charges. Arnong these are limiting duplication of services, preventing unnecessary proliferation of expensive equipment, and ensuring equal access to necessary health services for the entire population. The responsibility for health planning resides within these HSA's and is indeed at the local level. Although they are unique, their needs for information relating to emerging new tech­ nologies are generically similar.
In July 1975, Arthur D. Little, Inc. (ADL) , under contract to the Health Resources Administration (HRA), began to develop several health planning documents for the purpose of assisting local plan­ ners in planning for emerging medical technologies. One of these documents dealing with the subject of computerized tomography (CT) was completed in November 1975. The outline of the CT case study is surnrnarized in Table 1. Other case studies include multi-phasic screening, electron radiography, thermography, automated white blood cell counters, laminar air flow, miniature centrifuge analyzers, anesthesia gas scavengers, computerized patient monitoring, and automated hospital information systems. These case studies have cornrnon elements in that each technology is rela­ tively new, controversial, or for some other reason of intense interest to local planners.
1
2
TECHNICAL CHARACTERISTICS
• Equipment Selection Criteria
• Early Instrument Obsolescence
PLANNING APPROACH
• Areawide Planning
GEMPEL
2. INFORMATION NEEDS OF HEALTH PLANNERS
To ensure focusing on the information needs of local health planners, the ADL team developed the information for each study through a combined interview and expert reviewer process. The quest ions which needed answering were first defined by the local HSA's themselves. Estimates of need were thus obtained from the clinical community and documentation on currently available equip­ ment was directly from equipment manufacturers. The ADL team also developed additional insights on likely future developments from researchers and funding agencies. The team assimilated new data with existing information in ADL's files and these findings, tempered by the case team's and reviewers' judgement, were sum­ marized into a single "technical assistance and planning document."
One of the mandates of the National Health Planning and Resources Development Act is that, for all institutional capital equipment purehases of more than $150,000, a certificate-of-need (CON) application must be filed by the institution and approved by the HSA. States have the right to enact separate CON laws dropping this ceiling to as low as $1,000. For purehases of equipment utilizing evolving new technologies, analysis of a CON application can present a problem. For example, a local agency's information needs on CT scanning are relatively straightforward, but the avail­ able data are confusing, usually not designed for their purposes, and often developed by groups with vested interests in the tech­ nology.
The technical and clinical characteristics of CT head and body scanners are discussed elsewhere in this book and will not be re­ peated here, except when there is particular significance to planning and estimating medical need for CT scanners.
3. EFFECT OF CT ON ALTERNATIVE DIAGNOSTIC NEUROLOGIC* PROCEDURES
To health planners interested in analyzing the institutional "need" for various equipment necessary to service a given popula­ tion adequately, an estimation of the effect on established neuro­ logie practice is vital. Several procedures are used, in various proportions, in diagnostic neurologie work-ups: clinical examina­ tions, skull x-rays, echoencephalography, nuclear medicine brain scans, pneumoencephalography, and cerebral angiograms. Table 2
*An estimate of the effect of CT on diagnostic medicine in addition to neurology had not been done at this writing since few instruments capable of body scanning in less than 20 seconds/slice were avail­ able.
4 GEHPEL
eompares the risk and patient hospitalization eharaeteristies of CT brain seanning vs. other neurologie proeedures.
Table 2 - Proeedures Used in Neurologie Diagnosis*
PROCEDURE RISK HOSPITALIZATION
Pneumoeneephalograph X 4 - 6
Nuelear medieine brain sean X X
- Skull X-ray X X
*Souree: Arthur D. Little, Ine.
Sinee the CT scanner is primarily a soft tissue imaging deviee, its primary impact is on other soft tissue imaging deviees proeedures. Partieipants in the National Cancer Institute (NCI) CT neurologie evaluation projeet (Mayo, Massaehusetts General Hospital, Columbia, Cornell and George Washington) had examined enough patients to see emerging ehanges in praetiee. ADL aeeumulated their estimates of approximate percent reduetions in established neurologie soft tissue diagnosis proeedures due to replaeement by CT seanning as a basis for assessing CT impact (see Table 3).
CT PLANNING ISSUES IN 1975 AND 1976
Table 3 - Effect of Use of CT Scanning on Established Neurologic Diagnostic Soft Tissue Imaging Procedures*
PROCEDURE PERCENT REDUCTION IN 3-5 YEARS
Pneumoencephalograph 65 - 75%
Nuclear medicine "brain scan" 25 - 35%
*Source: Arthur D. Little, Inc. (estimates based on experience of early users), 1976.
4. HEALTH PLANNING ISSUES
The major issues affecting health planning, as defined by planners at ADL, were:
• equipment selection criteria,
Each of these is summarized briefly.
4.1 Equipment Selection Criteria
Equipment selection criteria do not differ substantially for head and whole-body scanners. Radiologists and physicists make a series of informed judgments relating to instrument capability and cost, patient population, and manufacturer's reliability, service, and reputation. There is no strict correlation between the need for head or body scanning capability and the cost and even the type of equipment purchased. Everyone prefers faster scanners; the fast body scanners produce better brain images than do slow brain scanners; and thus, body scanners are often purchased for brain­ scanning applications.
6 GEMPEL
There is adefinite need for more clinical experience with body scanners in extraneurologic applications. Medical benefits for brain scanners are established for all practical purposes, but it will take time to develop similar data for body scanners. Early reports indicate usefulness in at least liver, kidney, and pancreas tumor detection; radiation treatment planning; and needle biopsy guidance. With many CT body scanners now operational, more defini­ tive information should be accumulated rapidly and guidelines for diffusion of body scanners for use in total body applications should be possible.
4.2 Early Instrument Obsolescence
Early instrument obsolescence is not a serious problem since retrofit packages are available. Institutions are budgeting about $25,000 per year for these packages. ADL feels that it will be 3-5 years before equipment with scan times of substantially less than 5 seconds and equivalent improvement in diagnostic detail will be developed so as to make current models obsolete.
Justification of system purchase for brain scanning is based on the primary objective of providing better medical care. CT equipment is, however, a major capital expense for any health care institution and thus economic considerations are important. Recent cost/benefit calculations based on in-patient days and representative patient charges indicate that a reduction in pneumoencephalograms of about 15 per month can cost-justify a CT system (amortized over 5 years) on the basis of reduced hospital charges alone. The pure economics of CT scanning demonstrate that hospitals with CT systems utilized at a rate of 10 patients per day do not lose money at patient charge rates of ~$150. The potential for overutilization of CT scanning is now limited by the small number of CT units in use.
4.3 Diffusion of CT Scanning Systems
The diffusion of CT scanning systems has so far been described by a substantial equipment shortage due to limits on manufacturers' production capacity. These equipment shortages are not likely to be eliminated until 1977. By that time, the uses of CT extraneuro­ logic scanning will also be more clearly defined. Thus, when and if national guidelines are developed, the potential for overutiliza­ tion should be seriously evaluated.
4.4 Geographic Location
The geographic location of CT scanning systems is also an issue. CT scanners should be geographically distributed as widely
CT PLANNING ISSUES IN 1975 AND 1976 7
as possible to ensure patient access, but this cannot be done with­ out considering the diagnostic and therapeutic neurologie caseloads and the capabilities of various hospitals. This issue is discussed further below.
5. PLANNING APPROACH
5.1 Areawide Planning for CT Scanning Systems
Areawide planning for CT scanners is based on the assumption that all patients who could benefit should have access to scanning capability but that scanners should be placed where there is suf­ ficient patient load for full time clinical use. Thus, planning for computerized tomography (or any other new technology) involves two distinct activities:
• assessment of the area's need for the equipment on the basis of overall regional need based on population; demand for CT scanning as indicated by utilization of specific diagnostic procedures;
• selection of those facilities which offer access to appropriate medical specialists and other related facilities as weIl as geographie location to facilitate patient access.
Ideally, areawide planning for CT scanning should begin before the first application for CON approval is submitted. Until more definitive information about the extraneurologie applications for CT scanning becomes available, areawide planning will be concerned with CT brain scanning.
5.2 Assessment of Areawide Need
One proposed measure for approximating the number of systems required to meet the need for CT in neurology is based on population. The area population is divided by the estimated national average need--one CT brain scanner for each 250,000-300,000 population. However, because of the uneven geographie distribution of neuro­ logical services in the United States, one area may serve as a referral center for a large multi-state region for sophisticated neurological procedures. In such cases, a need assessment based solelyon local population would result in an underassessment of the size of the referral area and overassessment of the need in other areas in the region with limited local neurological services. Therefore, area population can be used only to give a general assessment of need.
8 GEMPEL
Another proposed measure of the systems required is based on existing neurological procedures. The experience of early users of CT brain scanners has demonstrated a correlation between the level of a hospital's neurological diagnostic and surgical activity and the adequate utilization of each CT brain scanner purchased. This correlation can be used in assessing total areawide need for CT brain scanners.
On the basis of current usage of existing systems, hospitals with the neurologie activity characteristics shown in Table 4 have been found to perform at least 1,500 CT scans per year. Therefore, division of the areawide neurologie activity totals by these levels of minimum activity can provide a measure for estimating the area­ wide requirements for CT scanners for neurologie use. These characteristics should be surveyed for all area hospitals. Each activity total for the whole area should be then divided by the appropriate minimum level.
These formulas provide a conservative areawide estimate based on initial experience with CT scanning. As further experience with the technology is accumulated, methods and bases for areawide planning will have to be modified accordingly.
5.3 Guidelines for Procurement of Initial CT Scanner
Once areawide need for scanners has been established, a de­ cis ion has to be made concerning where scanners should be located and, hence, which applications for scanners shoulrl be approved. Obviously those hospitals with the largest neurology services should be selected as the most suitable location for CT brain scanners in the area. Othei smaller hospitals, which individually have less than the minimum activity in the neurological services required to utilize adequately a CT brain scanner, should be en­ couraged to share CT facilities. Insofar as possible, CT brain scanners should also be geographically distributed throughout the area.
At the present time, CT scanners are most cost-effective when located in hospitals with specialized neurological and neuro­ surgical services. Therefore, site selection should be based mainly on availability of appropriate medical specialists and an existing active specialty service and, to a lesser degree, on geo­ graphie distribution in order to provide efficient patient access to the facilities. (See Table 4 for minimum staffing requirements.)
CT PLANNING ISSUES IN 1975 AND 1976
Table 4 - Minimum Requirements for Approval of Certifieate-of-Need Applieation for CT Scanners
Justified on the Basis of Neurologie Use Only (for institutions without a CT scanner)
SERVICES AND SPECIAL1STS
• radiology teeh. *Board Certified (1-2 per shift)
NEUROLOGIC ACTIVITY
• intraeranial proeedures > 50 per year
• eerebral arterio/angiograms > 200 per year
• pneumoeneephalograms > 25 per year
ACCESS CONSIDERATIONS
• geographie distribution
• scanners regionally available (1/300,000 indigenous population)
Source: Arthur D. Little, Ine. estimates based on review of 1975 planning guidelines, 1976.
9
5.4 Guide1ines of Procurement of Additional Scanners
A1though in the mid 1970's on1y three hospitals in the United States (Mayo C1inic, l1a11inckrodt Institute, and C1eve1and C1inic) had more than one scanner, other 1arge hospitals and hea1th center comp1exes now have multiple systems. The primary consideration in reviewing such requests for additional scanners is, of course, the experience with the first CT system, specifica11y the uti1ization rate and patient backlog. However, before approving a second scanner with on1y neuro1ogica1 capabi1ity, the c1inica1 potential for extraneuro1ogic app1ications shou1d be eva1uated and the advisabi1ity of adding who1e-body scanning capabi1ity shou1d be considered. There is concern among hea1th p1anners that more CT scanners than necessary to service a given patient population will be purchased and that, in order to cost-justify this equipment, patients will be scanned unnecessari1y.
One way of monitoring need is to gather positive and negative diagnostic data. The current rate of positive diagnosis with traditiona1 radiographs is approximate1y 20% as compared with posi­ tive diagnosis with CT scans of 70%.
5.5 Body Scanner App1ications
The evaluation of CT scanning of other regions of the body than the brain is moving rapid1y ahead as is reported in other chapters of this book. However, estimates of c1inica1 uti1ity are difficu1t, a1though there is c1ear1y considerab1e promise for use of the technique in the diagnosis of tumors, aneurysms, and simi1ar soft tissue patho1ogy. Purchase of equipment for body scanning shou1d present1y be 1imited to those institut ions which have de­ ve10ped adequate research and c1inica1 trial protoco1s and in which medica1 discip1ines appropriate to the proposed c1inica1 app1ica­ tion are represented. Thus, installation of such CT systems shou1d probab1y be restricted to major research centers and teaching hos­ pitals.
Specific requests for purchase approva1 for extraneuro1ogic app1ications shou1d be eva1uated for consistency with areawide plans and in accordance with the fo11owing criteria.
• experience and reputation of princip1e investigators, • adequacy of supporting faci1ities, • pertinence and imp1ications of research protocol, • sufficient patient load in proposed discip1ine for
satisfactory clinica1 trials, and • coordination of research in severa1 c1inical areas.
CT PLANNING ISSUES IN 1975 AND 1976
6. REFERENCES
Ambrose, J., "Computerized Traverse Axial Scanning (Tomography): Part 2 C1inica1 App1ication," Brit. J. Radiol. 46:1023-1047 (1974).
11
A1fidi, R. J., et al. , "Computer Tomography of the Thorax and Abdomen: A Pre1iminary Report," Radio1ogy 11.:257-264 (1975).
Baker, L., et al., "Computer Assisted Tomography of the Head. An Ear1y Evaluation," Mayo C1inic Proceedings 49:24-27 (1974).
Baker, H. L., "The Impact of Computed Tomography on Neuroradio­ logic Practice," Radio1ogy 116:637-645 (1975).
Bu11, "Editorial. The Changing Face of Neuroradio1ogy Over Near1y Forty Years," Neuroradio1ogy 2.:111-115 (1975).
Comprehensive Hea1th P1anning Counci1, Inc., "Interim P1anning Guide1ines for Computerized Transaxial Tomography (CTT)," Philadelphia, Pa., September 25, 1974.
Davis, D. 0., et al., "Computerized Tomography of the Brain, " Radio1. C1in. N. Amer. 12:297-313 (1974).
"Editorial: Computer-assisted Tomography of the Brain," Lancet 2: 1052-1054 (1974).
"Editorial: Image Reconstruction: Computerized X-ray Scanners," Science 190:542 (1975).
Genessee Regional Hea1th P1anning Counci1, Rochester, N.Y., "A Methodo1ogy Out1ine for Deve10pment of a Computer Tomography (CT) Plan."
Gunn, W. V., et al. , "Image Generation and Display Techniques for CT Scan Data," Invest. Radiol. 10:403-416 (1975).
Hea1th Resources Administration, Bureau of Hea1th Resources Deve1opment, "Technica1 Assistance Memorandum #16. Compu­ terized Axial Tomograph Scanners," Rockvi11e, MD (June 6, 1974).
Hea1th Resources Administration, Bureau of Hea1th Resources Deve1opment, "Technica1 Assistance Memorandum 1133. Additional Information on Computerized Axial Tomography (Now ca11ed "Computed Tomography or CT")," Rockvi11e, MD (December 3, 1974).
12 GEMPEL
"Hospitals Race to Buy Scanners as P1anning Groups Try to Hold Line," Medica1 Wor1d News, September ~:28-29 (1975).
Hounsfie1d, G. N., "Computerized Transverse Axial Scanning (Tomography). Part 1. Description of System," Brit. J. Radio1. 46:1016-1022 (1973).
Led1ey, R. S., et al. , "Computerized Transaxial X-ray Tomography of the Human Body," Science 186:207-212 (1974).
Led1ey, R. S., et al. , "The ACTA-Scanner: The Who1e Body Com­ puterized Transaxial Tomography," Computers Bio1. Med. 4: 133-136 (1974).
Levins, H. L., "How Many Scanners are Anough?" Modern Hea1th Care ~: 62-64 (1975).
Litt1e, Arthur D., Inc., A Hea1th P1anning Document: Computerized Tomographie Scanning Systems, contract HRA 230-75-0063, Hea1th Resources Administration, Hyattsvi11e, MD (November, 1975).
McCu11ough, E. C., et al. , "An Evaluation of the Quantitative and Radiation Features of a Scanning X-ray Transverse Axial Tomography: The EMI Scanner," Radio1ogy 111:709-715 (1974).
New, P. F. J., Scott., W. R., Schnur, J. A., Davis, K. R., and Taveras, J. M., "Computerized Axial Tomography with the EMI Scanner," Radio1ogy 110:109-123 (1974).
Paxton, R. and Ambrose, J., "The EMI-Scanner: A Brief Review of the First 650 Patients," Brit. J. Radiol. Q: 330-365 (1974).
Perry, B. J. and Bridges, C., "Computerized Transverse Axial Scanning (Tomography, Part 3. Radiation Dose Considerations)," Brit. J. Radio1. 46:1048-1051 (1974).
Report of the Joint Committee for Stroke Faci1ities XII, "Computed Tomography in the Management of Cerebrovascu1ar Disease," Stroke ~:103-107 (1975).
Sche11inger, D., et a1., "Ear1y C1inica1 Experience with the ACTA Scanner," Radio1ogy 114:257-261 (1975).
Scott, W. R., New, P. F. J., Davis, K. R., and Schnur, J. A., "New Computerized Axial Tomography of Intracerebra1 and Intraventricu1ar Hemorrhage," Radio1ogy 112:73-80 (1974).
Shapiro, S. H. and Wymore, S. M., "CAT Fever," New England Journal of Medicine 294:954-956 (1976).
CT PLANNING ISSUES IN 1975 AND 1976
Smith, P. R., Peters, T. M., Muller, H. R., and E1ke, M., "Towards the Assessment of the Limitations on Computerized Axial Tomography," Neuroradio1ogy 2.:1-8 (1975).
13
Wortzman, G., Holgate, R. C., and Morgan, P. P., "Crania1 Computed Tomography: An Evaluation of Cost Effectiveness," Radio1ogy 117:75-77 (1975).
Ze1ch, J. V" Ducheneau, P. M., Meaney, T. F., LaIli, A. F., A1fidi, R. J., and Ze1ch, M. G., "The EMI Scanner and Its App1ication to C1inica1 Diagnosis," C1eve1and C1inic Quarter1y 41:79-91 (1974).
AN OVERVIEW OF GOVERNMENT REGULATION OF THE USE OF COMPUTED
TOMOGRAPHY THROUGH 1978
Arthur D. Litt1e, Inc.
1. INTRODUCTION
Since its introduction to the hea1th care system of the United States about five years ago, computed tomography (CT) has become wide1y adopted. The rapidity with which c1inica1 experience has accumu1ated and the diagnostic usefu1ness recognized at major research centers is ana1ogous to the experience with x-ray fo11owing Roentgen's discovery in the 19th century. However, because of the high initial capita1 cost of CT and its introduction at a time when hea1th care costs are under c10se scrutiny, government agencies have worked to ensure appropriate uti1ization and distribution of the techno1ogy. Figure 1 summarizes the factors that have inf1uenced this process.
This chapter summarizes the status of three areas of government po1icy that has inf1uenced the uti1ization and diffusion of CT: hea1th p1anning, reimbursement, and performance and safety. Fina11y, major groups are described that have no exp1icit po1icy-making authority but have inf1uenced decision makers in other government agencies.
2. HEALTH PLANNING - THE HEALTH RESOURCES ADMINISTRATION
The National Hea1th P1anning and Resources Deve10pment Act (P.L. 93-641) is a comp1ex 1aw with far-reaching imp1ications. Of all the pertinent statutes in force today, it is the one most 1ike1y to have a significant long-term effect on the uti1ization of CT in the United States.
15
16
COST / BENEFIT ANALYSIS
ACTUAL MARKET DEMAND FOR CT
SSA
GOVERNMENT REGULATION OF CT THROUGH 1978
Very generally, the goals of the law are to improve the delivery of health care in its broadest sense, to maintain some restraints on the cost of health care, and to improve the health status of previously under-served groups in the population.
17
To accomplish these tasks, a multilevel health planning net­ work is being developed, which has more II c l out ,1I is subject to more explicit performance standards, and is better financed than its forerunners.
The Health Resources Administration (HRA) of the Department of Health, Education and Welfare (DHEW) has been charged with developing lI a national health planning capability geared to promoting equal access to quality health care at a reasonable cost. 1I The HRA Bureau of Health Planning and Resource Development (BHPRD) oversees the designation and funding of Health Systems Agencies (HSA's) and State Health Planning and Development Agencies (SHPDA's) and provides policy direction and technical assistance to the designated agencies. According to the recently proposed reorganization of the Administra­ tion these functions will continue to be performed by the BHPRD.
2.1 The Certificate-of-Need Process (CON)
One of the requirements of the National Health Planning and Resources Development Act with the most immediate implications for CT is the provision that every state require CON application and approval for the addition of new services and for capital expendi­ tures that exceed $150,000. (This process has been described in the previous chapter.)
During 1975 and 1976, local health planning agencies (IIBII agencies that were in many cases reorganized into HSA's under P.L. 93-641) were beseiged with applications by hospitals for approval of CT purchases. Because of the high cost of CT and the fact that CT's unprecedented rapid diffusion coincided with the per iod of implementation of more stringent health planning controls, CT became a focal point for cost-containment efforts and a paradigm for medical technology planning as a whole.
Local planners sought to decide where CT services should be offered and how many CT units were needed in the absence of either generally accepted methods for determining need or conclusive information concerning the efficacy of the technology. Most resorted to one or more of five general methods of determining need or allocating CT resources:
18 GEMPEL AND METZGER
• Size of population to be served (see Health Services Management, Inc., 1976; Alabama Department of Public Health, 1976),
• Distribution of installed units within area to be served (see Ohio Department of Health, 1975).
• Number of diagnostic procedures to be performed or patients with CT-detectable disorders being admitted to hospitals (see Health Planning Council, Inc., 1976),
• Incidence of CT-detectable disorders (cancer and neurologic disease) in the population (see Compre­ hensive Health Planning Council of Kentucky, 1975),
• Characteristics of provider institutions, such as availability of specialized medical staff and diag­ nostic and therapeutic services offered (see New York Department of Public Health, 1977).
Needs as measured by the methods developed varied widely. As part of a policy study on CT, the Hassachusetts Department of Public Health (1976) applied eleven different need formulae to Massachu­ setts; the resulting estimates of need for CT in the State ranged from 5 to 52.
By 1976, the influence of the health planning process on dif­ fusion of CT in the United States was apparent in terms of both the numbers of units acquired and the distribution nationwide. By mid- 1976, 18 states and many local planning agencies had developed CT guidelines as reported by the Arnerican Hospital Association (1977). Moratoriums on additional CT units had been declared by five state planning agencies to allow more time for the development of stan­ dards and criteria or to await the development of more definitive information concerning the clinical benefits of CT. According to the Arnerican Hospital Association survey in July of 1976, 34 CT applications had been denied.
One aspect of CT diffusion that has concerned health planners and third-party reimbursers alike was the installation of CT systems in physicians' offices and private clinics (not under health plan­ ning jurisdiction in most states). By mid-1976, 45 (of about 300 operational) units were located in neurology practices. These units were dedicated head scanners. In response to this concern, planning authority has been extended to cover CT purchases for private physician offices in two states, and similar legislation is under consideration in several others.
GOVERNMENT REGULATION OF CT THROUGH 1978 19
Paradoxically, the early trend for physicians in private prac­ tice to purchase CT units was in some part the result of the attempts by health planners to contain the proliferation of CT as pointed out by Shapiro and Wyman (1976). Welling (1976) notes that the planning process may also have intensified the purchases of CT by hospitals and doctors fearful of more restrictive requirements in the future. Lack of uniform guidelines and differing health planning mechanisms contributed to an uneven distribution of CT units nationwide in 1974-1975. By mid-1976 (placements reflecting 1974-1975 sales), one CT scanner was in use for every 800,000 Uni ted States inhabitants. The scanner-to-population ratio for in­ dividual states, however, ranged from 1:665,000 (New Jersey) to 1:300,000 (Florida) according to the American Hospital Association survey of 1976. By mid-1977, however, an analysis of state-by­ state placements of CT* indicated a relatively uniform distribution of CT scanners with one scanner per 400,000 population operational and one scanner per 180,000 population sold (including those units ordered but not installed).
According to the survey of Fineberg et al. (1977), every state but Missouri had some regulatory control over purchases of CT scan­ ners and four-fifths had CT guidelines in effect or under develop­ ment. More than 80 applications for CT had been denied, not in­ cluding the important and often not counted group of applications withdrawn before the final action of the planning authority (e.g., five such cases in Massachusetts alone). The ratio of denied appli­ cations had risen from 1:16 in 1976 to approximately 1:10.
2.2 National Guidelines for CT
Section 1501 of the Public Health Service Act, as amended by P.L. 93-641, required that the Secretary of DHEW develop and promul­ gate National Guidelines for Health Planning, including:
• Standards respecting the appropriate supply, dis­ tribution, and organization of health resources,
• A statement of national health planning goals developed under consideration of the national he health priorities set forth in Section 1502 of the Act.
*Arthur D. Little, Inc. survey of all state and local planning agencies (unpublished).
20 GEMPEL AND METZGER
The complete set of Guidelines will include a wide range of issues including cost containment, access to care, availability and distribution of health care resources, quality of care, and health status.
In its first set of guidelines, the Health Resources Adminis­ tration chose to "focus on a limited number of issues relating to hospital resources that present important short-term opportunities for the containment of costs and the enhancement of the quality of care" (see Federal Register, 1978A). Significantly, CT was in­ cluded as the only device among the eleven issues, which were pre­ dominantly services (such as obstetrical services or supply/occu­ pancy of general hospital beds).
The proposed guidelines were published (Federal Register, September 1977) for review and comment. The means for preventing duplication of CT services and containing cost was to ensure full and appropriate utilization of existing units. Minimum utilization was defined as 2,500 procedures per year. It was also proposed that: "There should be no CT scanners approved unless every ex­ isting or approved CT scanner in the service area is performing at a rate greater than 4,000 patient procedures." If actually promul­ gated, this requirement would certainly have slowed the rate of CT acquisitions in the Uni ted States. Although the American Hos­ pital Association survey (1977) did indicate that some CT units were examining as many as 25 patients per day, the mean was 13 per day. A survey by Evens and Jost (1976) of 98 installations showed that weekly patient volume averaged 50-55 or 10-12 patients per day. These data suggest that a significant number of CT units already in use would not have met the proposed guideline for maxi­ mum utilization.
Hearings were held in Washington, D.C. on November 16, 1977. Numerous issues were raised concerning the validity and appropriate­ ness of establishing guidelines at all. A great deal of concern was expressed regarding the apparent inflexibility of the guide­ lines applied to differing local conditions. Finally a number of respondents feIt that the proposed "maximum level" of 4,000 CT procedures was virtually unattainable.
The revised proposed standards published in the Federal Regis­ ter (1978A) had been changed substantially. Perhaps most signifi­ cant for the future utilization of CT was the lowering of the "maximum utilization" figure from 4,000 to 2,500. Final guide­ lines were issued on March 28, 1978 (see Federal Register, 1978B).
The presently constituted guidelines are reasonably consistent with utilization requirements and other priorities being used by many state and local planning agencies. A national standard
GOVERNMENT REGULATION OF CT TRROUGR 1978
obviously will facilitate more uniform distribution of CT units nationwide.
21
The guidelines are to be reviewed periodically, at least every 2 years. Significant new information establishing more clearly the efficacy of CT (including patient outcome measures) or its cost­ effectiveness will probably be required before the present CT guidelines are significantly revised or refined.
3. REIMBURSEMENT POLICY - TRE SOCIAL SECURITY ADMINISTRATION
Through the Social Security Administration (SSA) , which ad­ ministers Medicare and Medicaid, the federal government exerts a strong influence on use patterns of medical technology by its re­ imbursement mechanisms and policies. The Social Security Act (which was amended by the Social Security Amendments of 1972, P.L. 92-603) required Federal health programs to withhold reimbursement to hospitals for depreciation, interest, and return on equity capi­ tal relating to unwarranted capital expenditures. Operationally stated, this means that reimbursement for procedures performed on Medicare or Medicaid patients will not be reimbursed unless CON approval has been received. Additionally, other third-party payors, such as Blue Cross/Blue Shield are influenced by current positions of the SSA.
As reported by the National Academy of Sciences (1977), since October of 1976, the SSA policy concerning Medicare coverage for CT diagnostic services has specifically excluded body scans (i.e., scans other than the head). The policies of private reimbursers with regard to CT services vary on a state-to-state basis. As a result of the National Academy of Sciences, most states are now re­ imbursing for those body procedures listed as efficacious in that study.
4. PERFORMANCE AND SAFETY STANDARDS - TRE FOOD AND DRUG ADMINIS­ TRATION
The authority of the federal government over the performance and safety of medical equipment is derived from two statutes. One, the Medical Device Amendments of 1976 (P.L. 94-295), which greatly expanded the provisions of the Food, Drug, and Cosmetic Act of 1938. Under the amendments, all medical equipment and devices are grouped into one of three classes. General controls over good manufacturing practices are to be developed for all medical de­ vices (Class 1), performance standards are to be developed for many product classes (Class 2), and pre-market review and approval will be required for new life-sustaining products (Class 3).
22 GEHPEL AND HETZ GER
The other statute, the Radiation Control for Health and Safety Act of 1968 (P.L. 90-602) calls for the development and enforcement of standards for x-ray equipment performance. The Bureau of Radio­ logical Health (BRH) of the FDA does not concern itself with equip­ ment design per se; however, the performance criteria have a direct impact on design and fabrication methods.
In addition, the BRH has direct authority over the maintenance and assembly of x-ray equipment and, in cooperation with state and local agencies, inspects and tests products being manufactured and in the field. Finally, the BRH concerns itself with evaluation of x-ray techniques and practices. In this respect, compliance with Bureau Guidelines is not compulsory but these recommendations carry heavy de facto weight in court under circumstances of a malpractice suit.
The BRH has allowed for aperiod from August 1, 1974 to August 1, 1979 in which x-ray components which do not meet the federal standard may still be used, allowing for depletion of in­ ventories. No specific regulations for CT units are contained in the law or its amendments; however, performance standards for CT equipment are currently being drafted and are expected to be adopted by 1979. Performance standards can be expected to be modi­ fied as device technology evolves.
5. LEGISLATIVE ASSISTANCE GROUPS
Legislative assistance groups advise policymakers on compli­ cated issues, such as the degree and type of regulation of the health care system needed. The implicit power of these groups is extensive. Information gathering groups such as these ultimately influence the formulating of such legislation as the Medical De­ vices Law and the National Health Planning and Resources Develop­ ment Act and the establishment of new agencies such as the Office of Health Technology (legislation pending). Several such groups have been actively studying CT.
In June of 1976, the Congressional Office of Technology Assess­ ment published a draft memorandum concerning CT and the health planning problems posed by its introduction and use (see Banta and Sanes, 1976). This report pointed out the high costs of CT, emphasizing the inconclusiveness of available evidence concerning the benefits to be derived.
In August of 1976, the Health Research Group, a Nader-affili­ ated consumer organization, urged public and private thirty-party payors not to reimburse health care providers for CT examinations and health planners not to approve further purchases of CT "until there is objective evidence that the cost of buying and maintaining
GOVERNMENT REGULATION OF CT THROUGH 1978
such machines is off set by cost savings or medical benefits to patients." (See Bogue and Wolfe, 1976.) Largely based on the
23
draft memorandum by the Congressional Office of Technology Assess­ ment the study warned that CT was in danger of becoming "yet another case of medical technology which increases health care costs with­ out providing commensurate benefits to consumers of health care." These sentiments were also presented by the group at the CT National Guidelines Hearings in November and December of 1977.
Under the sponsorship of the Blue Cross Association, the National Institute of Medicine of the National Academy of Sciences convened a special committee to review what was known about CT efficacy, cost and level of reimbursement, placement, and policy implementation and to develop recommendations for both third-party reimbursers and health planners (see National Academy of Sciences, 1977). The recommendations with the greatest significance for the future diffusion of CT concerned reimbursement and control of CT in non-institutional settings. Efficacious clinical applications (including body examinations) were identified, and third-party reimbursers were urged to cover CT diagnostic services for these specified uses. In order to close the loophole in the health planning regulations that had resulted in installation of CT units in physicians' offices, or in clinics, the report recommended three actions:
• "Congress should amend the National Health Planning and Resources Development Act of 1974 to include the review of proposals for large capital equipment expenditures in free standing ambulatory care settings,"
• "Third-party payors should reimburse only for services provided by CT installations approved under a Certificate-of-Need program,"
• "Certificate-of-Need laws in each state should require the review and approval of the acquisition of major capital equipment whether by an indi­ vidual, group, or institution."
Although no specific estimates of the need for CT were given, the report recommended that no new units be approved until, "there is full and appropriate use of existing scanners."
At the request of the Chairman, House Committee on Appropria­ tions, the General Accounting Office reviewed the plans for the Department of Defense, the Veterans Administration, and the Depart­ ment of Health, Education, and Welfare for planning and using CT units in federal institut ions. The report (see General Accounting Office, 1978) released in January of 1978, concluded that a
24 GEMPEL AND METZGER
coordinated Federal approach was required, coordinated with the civilian sector.
All of these major legislative assistance groups have urged increasing controls on the acquisition and use of CT, through con­ trol of purchases and of distribution. This control has been exerted through the reimbursement mechanisms.
Although it is difficult to isolate the specific influence of such groups on health policy decision makers, their combined in­ fluence is visible. For example, the Office of Technology Assess­ ment study was influential in the setting of reimbursement policies by the Social Security Administration. Further, in several states the private third-party reimbursers now only reimburse for CT services in approved installations, and in some states the CON process has jurisdiction over all health-care providing institu­ tions (and hence clinics and physician offices).
6. CONCLUSION
The use of Computed Tomography, though widely hailed by the medical community as representing an advance in the capability of clinicians to diagnose disease, remains a controversial issue in the medical community in 1978. Several groups are involved in the regulation of CT (summarized in Table 1). The efforts of those groups over the past five years signal the beginning of a new era of governmental influence on the United States health care system: more rigorous clinical trials and cost justification of new modalities will probably replace the previous process of limited use in a few research hospitals, random trials, and eventual dif­ fusion of efficacious techniques.
GOVERNMENT REGULATION OF CT THROUGH 1978 25
Table 1 - Government Regulation of CT
Health Resources Administration (HRA)
Health Systems Agency (HSA)
Social Security Administration (SSA)
Health Research Group (Nader)
General Accounting Office (GAO)
26 GEMPEL AND HETZGER
Alabama Department of Pub1ic Hea1th, Guide1ines for Acquiring Com­ puterized Axial Units, Hontgomery, AL (1976).
American Hospital Association, CT Scanners: A Technica1 Report, Chicago, IL 91977.
Banta, H. D. and Sanes, J. R., A Hemorandum on Computed Tomography (CT) Scanners, U.S. Congress, Office of Techno1ogy Assessment (June 23, 1976).
Bogue, T. and Wolfe, S. H., CAT Scanners: Is Faneier Techno1ogy Worth a Billion Dollars of Hea1th Consumers' Honey?, Hea1th Research Group, Washington, D.C. (August 1976).
Comprehensive Hea1th P1anning Counci1 of Kentucky, Guide1ines and Criteria for Special Technica1 Apparatus, Frankfurt, KY (1975).
Evens, R. G. and Jost, R. G., "Economic Analysis of Computed Tomography Units," Amer. J. Roentgenol. 127:191-198 (1975).
Federa1 Register 42(185):48502-48505 (September 23, 1977).
Federa1 Register 43(14):3056-3069 (January 20, 1978A).
Federa1 Register 43(60):13040-13050 (Hareh 28, 1978B).
Fineberg, H. V., Parker, G. S., and Pear1man, L. S., "CT Scanners: Distribution and P1anning Status in the United States," New Eng. J. Hed. 297:216-218 (1977).
General Accounting Office, Computed Tomography Scanners: Oppor­ tunity for Coordinated Federa1 P1anning Before Substantia1 Acquisitions, Report to Congress (January 30, 1978).
Hea1th P1anning Counci1, Inc., Acquisition and Use of Computer­ Assisted Tomography in Rhode Is1and, Providence, RI (January 1976) .
Hea1th Services Hanagement, Inc. and The Seven Area-wide Compre­ hensive Hea1th P1anning Agencies of Indiana, Computerized Tomography: How Hany Scanners are Enough?, Indianapo1is, IN
Hassachusetts Department of Pub1ic Hea1th, CT Scanning, Boston, HA (1976) .
GOVERNMENT REGULATION OF CT THROUGH 1978
National Academy of Sciences, Institute of Medicine, A Po1icy Statement: Computed Tomographie Scanning, Washington, D.C. (April 1977).
New York Department of Pub1ic Hea1th, Pre1iminary Interim Guide- 1ines for Computerized Transaxial Tomography, Albany, NY (1977) .
Ohio Department of Hea1th, Review Criteria on Computed Tomography (CT), Co1umbus OH (1975).
Shapiro, S. H. and Wyman, S. H., "CAT Fever," New Eng. J. Med. 294:954-956 (1976).
Socia1 Security Administration, Hedicare Coverage of Computerized Tomography Diagnostic Services (October 1976).
27
We11ing, K. M., "CAT Lovers. The Medica1 Profession Embraces the Computerized Scanner," Barron's (August 16, 1976), p. 11.
MULTIPLE ENDPOINTS IN THE ASSESSMENT OF NON-INVASIVE TECHNOLOGY
W. R. Ayers
1. INTRODUCTION
In 1966, $42.1 billion or 5.9 percent of the Gross National Produet (GNP) was spent on health eare. By fiseal year 1976, health eare spending had more than tripled - growing to $139.9 billion - and eonsumed about 8.6 percent of the GNP. (See Washing­ ton Post, May 8, 1977, p. Al et seq.) Between 1965 and 1974, aeeording to a eongressional estimate, half of the 27.7 billion inerease in hospital eare eosts eould be aeeounted for direetly or indireetly by the introduetion of new medieal teehnology as eited by Culliton (1977). Despite these large dollar inereases, data showing that more spending has resulted in improved health are un­ available. The biomedieal eommunity and elinieal medieine espeeially ean no longer afford the luxury of eostly development, wasted initial expenditure, and ultimate attrition by disrepute - a sequenee eharaeterized in gastrie freezing teehniques for the eontrol of upper gastrointestinal hemorrhage and in hyperbarie oxygen ehambers, to name two fairly reeent medieal fiaseos.
1.1 Non-Invasive Teehnology for Clinieal Chest Diseases
For example, like all elinieians, ehest physieians (pulmonary and eardiae) depend primarily on the elinieal history, the physieal examination, and routine laboratory studies, ineluding x-rays and the eleetroeardiogram. Most diagnoses are made or at least strongly suggested during that "standard elinieal workup." To be sure, the ehest physieian mayaiso use some speeialized studies such as sputum examination in the ease of the pulmonologist or speeialized
29
30 AYERS
maneuvers to enhance heart sounds and murmurs in the case of the cardiologist, but these are "tricks of the trade."
The chest physician, like other specialists, has in the past been forced to use invasive techniques (e.g., biopsies, surgical explorations, cardiac catheterizations, etc.) in the diagnosis and management of a sizeable portion of conditions encountered in clin­ cal practice. And chest physicians, like other physicians, are in­ trigued and enthused by the newer non-invasive techniques discussed in this book.
Nuclear imaging and the measurement of radio-labeled gases for the determination of ventilation/perfusion abnormalities in lung disorders gained widespread clinical use in the early 1960's as reported by Taplin (1964) and Wagner (1964). These techniques are routinely used in the diagnosis and monitoring of pulmonary vascu­ lar syndromes and more recently in the delineation of areas of myo­ cardial necrosis in cardiology.
Ultrasonic imaging has been in wide clinical use since the late 1960's. (See Newell, 1963, and Grossman, 1966.) It is a rou­ tinely performed diagnostic study applied primarily to cardio­ vascular conditions of the chest.
Computerized tomography, a new imaging technique introduced in the last five years, has had an unprecedented growth rate. There are already more than 700 of these instruments in the United States, each costing from $85,000 to $800,000. The initial instruments, designed to scan only the head, were technically successful, but as pointed out by Peterson (1976) at Harvard depicted very few lesions that were treatable. Whole body scanners, now in wide clinical use, must compete with other imaging devices, e.g., ultrasonography, nuclear scanning, angiography and other conventional x-ray studies, for the proper place in the diagnostician/monitor's armamentarium.
1.2 Assessment of Medical Technology
What is needed, of course, are controlled studies using agreed-upon criteria for measurement. Medicine must assiduously guard against the development of such measures by economists alone. It is characteristic of econometric analyses to quantify benefits in terms of successful ultimate outcomes. In medical systems this usually translates into reduced death rates or improved state of health in a defined community.
Burger (1974) reports that, with a few notable exceptions (e.g., near irradication of polio by development of vaccines), most breakthroughs in total community health have come from technologies
ASSESSMENT OF NON-INVASIVE TECHNOLOGY
outside medicine such as nutrition, sanitation and education. (See also the New York Times, June 26, 1977, p. E19 et seq.)
31
No one expected the development of the electrocardiograph and the subdiscipline of electrocardiography to irradicate heart disease. The determinants of heart health and heart disease include variables unrelated to a device useful in the diagnosis and monitoring of some cardiac conditions. It is likewise illogical to expect an imaging device, such as computerized tomography, to alter materially the incidence or outcome of community disease rates.
Meaningful assessment of medical technology requires the development of two conceptual frameworks. One should be used to categorize the levels of technology being applied; the other, to categorize the characteristics of health services to be delivered. Then rationaloutcomes are nearly self-evident and are setting­ specific.
2. LEVELS OF TECHNOLOGY
Fortunately, Thomas (1971) has categorized medical technology for uso His concepts have been applied by Ayers (1977) to tech­ nology for handicapping conditions. In Thomas' view there are three levels of technology. The first is termed "non-technology," which is impossible to measure in terms of its capacity to alter either the natural course of illnesses or their outcome. It is what is meant by the phrases "caring for" and "standing by." It is indispensable. It is valued highly by the humanitarians in medicine and their patients. It is sometimes called "supportive therapy." The measures of effectiveness for this level of tech­ nology do not easily fit cost-effectiveness studies.
The next level of medical technology is termed "halfway tech­ nology." This relates to the kinds of things that must be done after the fact of illness. It includes detection of or inter­ vention in a process whose course quite often one is unable to do very much about, most likely because of astate of ignorance re­ garding the fundamental aspects of the disease. This level of technology is inherently both highly sophisticated and profoundly primitive. Some outstanding recent examples are organ transplants and the fabrication of artificial organs and limbs. It is the wonderfully technical world of sensors and transducers that measure, stimulate, or simulate the body structure and function. It is the kind of technology that in the public mind and in the media is viewed as a breakthrough rather than as a stopgap. This is the kind of technology, technique, or instrumentation that one must use until there is a genuine understanding of the basic mechanisms involved in a given disease. It is the characteristic of this kind of technology that it costs an enormous amount of money and requires a continuing expansion of specialized personnel
32 AYERS
and faci1ities. Computerized tomography is in this c1ass. But, most important1y, the measures of effectiveness for ha1fway tech­ no10gy are intermediate rather than ultimate. Because members of this techno10gic c1ass are imperfect, comparative studies are especia11y important.
The third type of techno10gy is the kind that is so effective that it is taken for granted and attracts 1itt1e pub1ic notice. This is the genuine1y "decisive techno10gy" of Thomas. This is the rea11y high techno10gy that is based on the resu1ts of funda­ mental understanding of disease mechanisms. When it becomes avai1ab1e, it is re1ative1y inexpensive and easy to deliver. The Sa1k/Sabin vaccine for polio is an examp1e. It is characteristic of most decisive techno10gy that it is usua11y based on severa1 generations of ha1fway techno10gy. Outcomes for ha1fway techno10gy ought not be measured in terms app1icab1e to decisive techno10gy.
3. HEALTH SERVICES DELIVERY SYSTEMS
Many conceptua1 frameworks for the description of hea1th services de1ivery in this country have been proposed and discussed by such authors as F1ag1e (1969), Kissick (1970), and Garfie1d (1970). Common to all is the deve10pment of a concept for the rational a110cation of scarce resources to specific outcomes. These theoretica1 descriptions must hav~ counterparts in actua1ity so that the impact of imp1emented techno10gy can be measured. The conceptua1ized system must be characterized according to its inputs, the medium to be transformed, and its outcomes. One conceptua1 system is charted in Tab1e 1.
Tab1e 1 - Conceptua1 System for Categorization of Elements in Hea1th Services De1ivery System (after Kissick, 1970)
INPUTS MEDIUM OUTPUTS
Personne1 Organizationa1 Services (Le., structure of medi- their kind, qua1ity,
Know1edge and ca1 care quantity, avai1- skills ability, nature and
Financing mecha- cost) Facilities and nisms equipment
Educationa1 Dollars avai1ab1e networks
ASSESSMENT OF NON-INVASIVE TECHNOLOGY 33
Critica1 to the characterization and assessment of techno1ogy in c1inica1 medicine is the rea1ization that diagnostic techno1ogies can be used to support two different kinds of decisions that doctors make with regard to their patients: (1) Nominative decisions derived from patho-physio1ogic 1aws resu1ting in the naming of a disease process, i.e., diagnostic decisions and (2) Managerial decisions based on management techniques cu1minating in the se1ection of a course of action. For examp1e, in c1inica1 chest medicine one may be interested in not on1y naming and monitoring the disease (i.e., diagnosis and prognosis) but also in choosing an action (i.e., patient management). In c1inica1 situations it is not a1ways necessary to arrive at an absolute diagnosis in order to choose an appropriate course of action. Thus, in the case of 1ung nodu1es, it may on1y be required to differentiate benign 1esions from ma1ignant 1esions without attaching a specific patho1ogic diagnosis to the nodu1e. Likewise, in cardiovascu1ar diseases, it may be sufficient to de1ineate the anatomic character­ istics of an intracardiac abnorma1ity and the order of magnitude of the pressure/f1ow deficits, both of which can be done by non-invasive techniques, rather than measure the precise physio1ogic deficits that usua11y require invasive methodo1ogy.
In some of the chapters that fo11ow, se1ected case studies in the app1ication of non-invasive techniques to c1inica1 situations in chest medicine are discussed. No attempt has been made to be exhaustive1y comp1ete; the cases cited are to be viewed as examp1es of app1ication on1y.
4. CONCLUSION
Newer techno1ogies a10ne or in combination (e.g., radio1abe1ed injections at the time of computerized tomography, angiographic studies performed simu1taneousiy with tomography, etc.) hold immense prospects for quicker, 1ess traumatic resu1ts that the c1inician can use in the managerial and nominative decisions that he makes about his patients. On1y when the benefits of these tech­ niques are identified and compared can the required cost-benefit and cost-effectiveness studies be performed.
Organized medicine has had thorny quest ions about ha1fway techno1ogy put to it before but never when dollar cost was the immediate concern. Esca1ating hea1th care costs and severe compe­ tition for federa1 dollars have brought today's perspectives to the assessment of ha1fway techno1ogy. The biomedica1 sciences ought to conduct the appropriate studies of cost-benefit and cost-effective­ ness with the rea1ization that criteria for measurement are specific for the settings in which the techno1ogy is used and shou1d be based on an appreciation of outcomes for specific levels of techno1ogy.
34 AYERS
In the setting of increased costs and uncertain or unclear benefits, Federal response is predictable - regulatory legislation.
ASSESSMENT OF NON-INVASIVE TECHNOLOGY
5. REFERENCES
Ayers, W. R., "The App1ication of Techno1ogy to Handicapping Con­ ditions and for Handicapped Individua1s," The White House Conference on Handicapped Individua1s, Vo1. 1 (1977), p. 15.
Burger, E. J., "Hea1th and Hea1th Services in the United States," Ann. Int. Med. 80:645 (1974).
Cu11iton, B., "Science, Society and the Press," N. Eng. J. Med. 296:1450 (1977).
35
F1ag1e, C. D., "Communications and Contro1 in Comprehensive Patient Care and Hea1th P1anning," Ann. N. Y. Acad. Sci. 161:714 (1969).
Garfie1d, S. R., "The De1ivery of Medica1 Care," Sci. Am. 222:15 (1970).
Grossmann, C. C. et a1. (eds.), Ultrasound in Medica1 Diagnosis, New York, Plenum Press (1966).
Kissick, W. L., "Hea1th Po1icy Directions for the 1970's," N. Eng. J. Med. 282:1343 (1970).
Newe11, J. A., "U1trasonics in Medicine," Phys. Med. Biol. 8: 241 (1963).
Peterson, o. L., "Eva1uating Medica1 Techno1ogy (Editorial) ," Ann. Int. Med., 85:819 (1976).
Tap1in, G. V. et al. , "Suspension of Radioalbumin Aggregates for Photoscanning of the Liver, Spleen, Lung and Other organs," J. Nuc1. Med. 2:259 (1964).
Thomas, L., "The techno1ogy of Medicine," N. Eng. J. Med. 285: 1366 (1971).
Wagner, H. N. et a1., "Diagnosis of Massive Pu1monary Embo1ism in Man by Radioisotope Scanning," N. Engl. J. Med. 271:377 (1964).
THE EVALUATION OF DIAGNOSTIC TESTS*
S. N. Rasmussen
Herlev Hospital
Herlev, Denmark
1. INTRODUCTION
A number of factors must be considered in the evaluation of new methods of investigation including (a) diagnostic value, (b) therapeutic consequence, (c) discomfort and risk to the patient, and (d) economic cost. This chapter deals with the evalu­ ation of a diagnostic test in connection with the detection or exclusion of anatomically defined diseases with an accessible diagnostic criterion (e.g., malignant tumors). In such cases the diagnostic specificity may be calculated (i.e., the probability that a patient has the disease provided the test is positive p(dlt» and the diagnostic sensitivity may also be calculated (i.e., the probability that a patient does not have the disease provided the test is negative p(dlr».
Unfortunately p(dlt) and p(dlt) are rarely calculated. Instead the clinically irrelevant inverse probabilities are determined, i.e., the probability that the test is positive in a patient known to have the disease P(tld) and the probability that the test is negative in a person who does not have the disease p(rld). Fixed standards have been laid down for the testing of new treatments in controlled clinical trials, whereas new methods of diagnostic investigation are rarely subjected to a probabalistic cost/benefit evaluation in a controlled study. Such studies are greatly needed.
*From Rational Diagnosis and Treatment (1976) with permission of the author, S. N. Rasmussen, and the publisher, L. B. Lippincott Co., Philadelphia.
37
2. METHODS OF PROCEDURE
Diagnosticians, i.e., doctors working in departments of radiology, ultrasonics, nuclear medicine, etc., carry out diagnostic examinations and develop new diagnostic methods in order to help their clinical colleagues. Consider the whole sequence of the decision process: (1) The clinician defines his patient's problems and collects the data base, i.e., routine history taking and physical examination; (2) He decides which investigations are to be done; (3) He assesses the results of these investigations and makes a diagnosis; (4) He decides on the best treatment, and (5) He assesses the treatment result. Thus, the decision process comprises two types of decisions: (a) decisions about investiga­ tions and (b) decisions about treatment.
Many clinicians have realised that it is no longer permissible to base therapeutic decisions on tradition and uncontrolled experience, but that the effect of both old and new therapeutic treatment must be tested on controlled therapeutic trials. This viewpoint is also supported by health authorities in several countries which do not permit the introduction of new drugs unless such trials are carried out. However, in the case of methods of investigation most clinicians do not make the same demand. The number of diagnostic tests at our disposal is steadily increasing, but, in contrast to new therapeutic treatments, the benefit of these new diagnostic tests to patients is very rarely evaluated in controlled studies.
Books on clinical research methods effectively deal with the principles of controlled therapeutic trials (i.e., selection of patients, randomization, prevention of bias, statistical evaluation, etc.) but no fixed standards have been laid down for the evaluation of new diagnostic methods. This chapter discusses this problem taking the approach of the clinician, because it is the clinician who defines the clinical problem, decides which diagnostic tests are to be done, and assesses the results of these tests. This means that the diagnostician must provide the clinician with infor­ mation which is formulated in such a way that it is relevant to the clinician's decision on his patient's diagnosis. In that situa­ tion the clinician knows the result of the diagnostic test and he wants to decide whether or not the patient has the disease in question.
When a new diagnostic procedure is evaluated a complex cost­ benefit analysis should be carried out. Four factors have to be considered as defined in the paragraphs below.
EVALUATION OF DIAGNOSTIC TESTS
2.1 The Diagnostic Information Obtained by the Investigation
One must take into account that clinicians use diagnostic tests (a) to establish and (b) to exclude different diagnostic possibilities. A test need not be equally valuable for both (a) and (b).
2.2 The Therapeutic Consequence of Establishing or Excluding a Diagnosis
It must be considered unethical to perform an investigation
39
if it can be predicted in advance that the result will not benefit the patient. Usually the benefit must consist of effective therapy, although it may in some cases be important to prove that a patient suffers from an incurable malignant disease or that he suffers from a benign disease which needs no treatment.
2.3 Discomfort and Risk to the Patient
We must always bear in mind that some diagnostic examinations are unpleasant and that others expose the patient to a risk of serious complications.
2.4 Economic Cost
This includes wages to medical personnel, cost of instruments, cost of prolonged admission to the hospital and patient's loss of income. Such costs have to some extent been ignored by the medical profession, but they need serious attention at a time when we are being forced to realize that expenditure within the health care system cannot continue its uninhibited growth.
3. EVALUATION OF DIAGNOSTIC INFORMATION
An analysis of the value of diagnostic tests is inherently linked to the problem of different types of diseases. Consider very briefly the three types of diseases: (1) Anatomically defined diseases with an accessible defining criterion, e.g., most malignant tumors; (2) Diseases with a concealed anatomical defining criterion, e.g., myocardial infarction, where the true diagnosis is never ascertained in the majority of patients suspected of this disease, since they survive; (3) Clinical syndromes, e.g., rheumatoid arthritis where there is a continuum from patients with completely typical pictures to patients with such atypical pictures that some clinicians will diagnose rheumatoid arthritis and others will not. (The American Rheumatism Association has established a
40 RASMUSSEN
definition of rheumatoid arthritis using arbitrary criteria, but further changes in the delimitation of the syndrome are foreseen.)
It is extremely difficult to establish standards for the evaluation of new tests for the diagnosis of diseases with a con­ cealed defining criterion and for the diagnosis of syndromes. Therefore, we shall concentrate on the first type of diseases, i.e., those diseases which are anatomically defined with an accessible defining criterion. The diagnosis of such diseases has been well analyzed in the literature, especially by Lusted (1968).
If a new diagnostic test is suggested for the diagnosis of, for instance, a malignant tumor, it is necessary to determine p(dlt) and p(cllt) where P means probability, d is the presence of the disease in question and t is the positive outcome of the test. The symbol cl s