David V. Beard, PhD #{149}Bradley M. Hemminger, MS #{149}J. Randolph Perry, MD #{149}Matthew A. Mauro, MD

Keith E. Muller, PhD #{149}David M. Warshauer, MD #{149}Michael A. Smith, MD #{149}Alexander J. Zito, MD

Interpretation ofCT Studies: Single-ScreenWorkstation versus Film Alternator’

From the Departments of Radiology (D.V.B., B.M.H., J.R.P., M.A.M., D.M.W., M.A.S., A.J.Z.), Com-

puten Science (D.V.B.), Biostatistics (K.E.M.), and Surgery (M.A.M.), School of Medicine, University ofNorth Carolina, 509 Old Infirmary Rd. Chapel Hill, NC 27599-7510. Received August 31, 1992; revi-sion requested October 21; revision received December 21; accepted December 29. Supported in part

by NIH grant no. ROl CA44060. Address reprint requests to D.V.B.‘ RSNA, 1993

565

Computer Applications

A prototype single-screen worksta-tion with a 2,048 x 2,560-pixel high-brightness monitor, 0.11-secondimage display time, and simple ergo-nomic design was compared to a con-ventional horizontal film alternatorin diagnostic interpretation of chestcomputed tomography (CT) studies.Four radiologists used either theworkstation or film alternator in in-terpretation of studies obtained in 10patients. A counterbalanced within-subject repeated measures expen-mental design was used. Responsetimes were analyzed for both meth-ods of interpretation. Grades of excel-lent, acceptable, and unacceptablewere assigned by a blinded “grader”to reports of the radiologists. The av-erage time needed for an interpreta-tion at the workstation was 5.65 mm-utes. No interpretations were gradedunacceptable. Retrospective poweranalysis showed that 16 observersrather than four would have beenrequired to show that use of theworkstation was faster than the alter-nator. With this 95% confidence inter-val, the workstation interpretationtime is clinically equivalent to thatwith the alternator. These data showthat this type of workstation haspractical application in interpretationof CT, magnetic resonance imaging,and ultrasound studies.

Index terms: Computed tomography (CT),

image display and recording #{149}Diagnostic nadi-

ology, observer performance, 47.1211, 60.1211Images, display #{149}Images, interpretation #{149}Pic-

tune archiving and communication system

Radiology 1993; 187:565-569

P ICTURE archiving and communica-tion systems (PACS) hold the

promise of reduced costs (1,2) andimproved logistics through reductionin film expenses, simultaneous accessby multiple radiologists to the same

imaging study, elimination of lostexaminations, and the potential forcost-effective access to various image

processing techniques (3,4). This is

particularly true for modalities suchas computed tomography (CT), which

are inherently digital and for whichmultiple small images completely fitonto available monitors. These poten-tial benefits, however, have awaiteddesign of a workstation that can facili-

tate fast and accurate interpretationsof CT studies (5).

A number of researchers have eval-

uated various workstations for inter-pretation of CT and magnetic reso-

nance (MR) imaging studies. All ofthese used one to eight 1,024 x 1,024-pixel monitors with image displaytimes ranging from 1.5 to 26 seconds.

Foley et al (6) observed reduced accu-racy, likely caused by the slow 7.5-26-

second image display time of the

commercial workstation they wereevaluating. In general, however, otherstudies (7-11) have concluded that

with a good quality monitor, appro-pniate window settings, and accept-able computer-interpreter interaction,use of a PACS workstation can pro-

vide the same interpretation accuracyas a film alternator.

Interpretation time is another mat-ten. In most of these studies, time with

workstations was found to be consid-

erably longer than with a film alterna-

ton, with radiologists often taking

more than twice as long to interpreta study, although Straub et al (11)

found two display modes-one withtwo high-speed 2,000 x 2,000-pixelmonitors, and the other with a high-speed cine or sequential display-to

be as fast as film for an abdominalmass detection task involving comple-

tion of a computerized findings form

as part of a receiver operating charac-

teristic study.

Fast as well as accurate interpreta-

tion is essential if a CT workstation isto be clinically effective. To this end,we constructed a prototype worksta-tion called FilmStrip, by using a single

2,048 x 2,560-pixel high-brightness

monitor, a new interface design witha simple computer-human interac-tion, and an extremely fast image dis-play time. FilmStrip is designed for

interpretation of CT, ultrasound (US),and MR imaging studies, which in-volve a large number of small images.

A time and motion study (12) sug-

gested that image display area, imagedisplay time, and a simple interaction

are the most important factors in in-terpretation speed with a worksta-

tion. Because of this, we expectedFilmStrip to facilitate faster CT scaninterpretation than previous elec-tronic workstations. A simplified timeand motion analysis (13,14) of an ex-ample may be helpful. A previousprototype CT workstation of ours(FilmPlane [8]) used a single 1,024 x

1,024-pixel monitor to display fourfull-resolution CT images in 1.5 sec-onds. Each image display operation

displayed a new row containing two

CT images. Observation of radiolo-gists using FilmPlane to interpretcomplex CT studies indicated that onaverage, 49 image display operationswere used to interpret complex 40-section chest CT studies. Since each

Abbreviation: PACS = picture archiving andcommunication system.

566 #{149}Radiology May 1993

image display operation required 1.5seconds, the radiologist spent an

average of 73 seconds (49 opera-

tions X 1.5 seconds) waiting for im-

ages to be displayed during an inter-

pretation.FilmStrip, on the other hand, allows

simultaneous display of 12 full-resolu-

tion images, rather than the four thatthe early workstation could manage.Since many more images are dis-

played at the same time, the radiolo-gist needs only about 18 image dis-

play operations to view the entire

study during the interpretation. Also,

since the images are displayed in 0.11

second, the radiologist spends an av-erage of only 2 seconds (18 opera-tions X 0.11 second) waiting for im-ages to be displayed during the

interpretation, for a savings of oven 70seconds per study when compared

with FilmPlane. Additionally, theFilmStrip interaction design requires

fewer button presses and other handmotions, which results in even fasterinteraction times.

We conducted an experiment toevaluate the hypothesis that the inter-pretation time of chest CT studieswith the FilmStrip workstation is din-ically equivalent to that with a filmalternator.

“down” scroll buttons to control move-ment (Fig 1). While the 2,048 x 2,560-pixel monitor can display simultane-ously 20 full-resolution 512 x 512 CT im-ages, preliminary observer testing mdi-cated that the radiologists prefer imagesthat are the same physical size as film.Interpolation was used to enlarge theimages, resulting in 640 x 640-pixel,9 x 8-cm images, with 12 images simulta-neously displayed in a three columnby four row filmstrip. A somewhat

smaller 2,000 x 1,600-pixel monitor alsowould allow display of 12 full-resolutionimages.

The workstation keyboard is configuredinto a five-button control panel, with but-tons for up and down functions as well asthree preset intensity windows (Fig 2).Each operation scrolls the filmstrip up ordown by two rows, or half of the display,which allows an image to be comparedwith all of its neighboring images. Sincethe majority of CT interaction involvesscrolling, we applied the principle oflarge buttons (17,18) and used the spacebar for down and all the other type-writer keys for up. Lung, soft-tissue, andbone preset intensity windows are pro-vided through three function keys at thetop of the keyboard. These intensitywindow settings were fixed for all cases.Since preset intensity windows must beused with an alternator and film, wechose to not provide dynamic inten-sity windowing, thus allowing a con-trolled comparison of the workstationand alternator.

Figure 1. FilmStrip metaphor.

t

MATERIALS AND METHODS

Equipment

Studies were interpreted with a conven-tional horizontal film alternator and Film-Strip. This prototype workstation uses a

single 28 x 35-cm, 2,048 x 2,560-pixel, 72-Hz, noninterlaced monitor (MegascanTechnology, Littleton, Mass) providing50 ft-L of brightness at the center of the

screen. This monitor has five times morepixels than a conventional 1,024 x 1,204-pixel display. The monitor is mounted in-side a dark, nonglare cabinet, in portraitorientation, with a vertical monitor sur-face, and with its center at average eyelevel. This monitor uses a 2,048 x 2,560-pixel video buffer and a 4,096 x 4,096-pix-el frame buffer all connected with a VMEbus to a workstation (model 4/370; SunMicrosystems, Mountain View, Calif). Theframe buffer can contain up to 40 12-bit-per-pixel CT images. A special bus con-necting the high-speed frame buffer to thevideo buffer allows any number of imagesin the frame buffer to be windowed ac-cording to intensity, increased or de-creased in size, copied to the video buffer,and displayed on the monitor in 0.11 sec-ond. This near-instant image display timeis slightly faster than the human reaction

time to press a keyboard button.The design of FilmStrip uses the meta-

phor (15,16) of a single-panel vertical alter-nator in which the images are arrayed in along vertical “filmstrip” with “up” and

Observers and Cases

Four board-certified radiologists experi-enced with chest CT participated in thestudy. All observers were less than 45

years old and had experience with corn-puter word processors.

Eight studies with multiple abnormal

findings at chest CT and two studies with-out abnormalities were selected by a radi-ologist who was not an observer. Findingsamong the abnormal cases were distrib-uted as follows: mediastinal or hilarmasses or masses bordering the heart(n = 4), pleural effusions (n = 2), paren-chymal infiltrate (n = 1), esophageal nar-rowing (n = 1), and positive findings atcytologic evaluation of sputum (ii = 1).An additional chest CT case was used fortraining the radiologists to use the work-station. All studies had been obtainedwith the same CT scanner (2060; Techni-care [GE Medical Systems], Milwaukee,Wis), with an average of 37 sections percase. The CT scout view was included inthe upper left-hand corner of the film-strip. To control for the effect of case onoutcome, the 10 cases were paired fordifficulty and divided into two equalgroups. The original CT requisition form,typically including patient history and

the referring physician’s clinical ques-lion, was obtained for each case. Theoriginal films were used for alternatorviewing.

Figure 2. FilmStrip control panel, based onthe Sun workstation keyboard.

Experimental Design andProcedure

A counterbalanced, within-subject ex-perimental design was used, with eachobserver reading one group of cases byusing the film alternator and the othergroup using the FilmStrip in separate ses-

sions several weeks apart. Each case wasread exactly once by each observer, andeach case was read the same number oftimes with the workstation and film alter-nator. Case presentation, observer, andmethod were controlled. Two observersstarted with the workstation and pro-

gressed to the alternator, while the othersstarted with the film alternator.

Film alternator sessions were conductedin clinical reading rooms with dimmedlighting during inactive periods. One hour

was typically required to interpret the

cases and gather the observer’s verbalcomments. Care was taken to eliminate

interruptions and distractions. Observers

Volume 187 #{149}Number 2 Radiology #{149}567

neous findings, all critical findings, all

relevant findings, and a rich detail of non-critical findings; acceptable-no erroneous

findings, all critical findings, and all rele-vant findings; or unacceptable-an erro-neous finding, a missed critical finding, or

a missed relevant finding.

Data

RESULTS

were instructed to work as quickly as pos-sible to produce a report of clinically ac-

ceptable quality. For each case, the ob-

server was given a patient film folder

containing the single CT chest study and a

card containing the relevant requisitioninformation. Films in the patient folderwere in the correct order. Observersloaded the films onto the alternator,viewed the images, and dictated the re-

port by using a familiar dictation machine.

We used a dictated report rather than the“findings form” typically used for receiveroperating characteristic studies, because a

findings form can augment human work-

ing memory (19) and distort the user’s be-

havior and interpretation time. FilmStripsessions were conducted in a controlled

environment (20). After the dictationdevice, seat adjustment, and keyboard

and monitor placement were checked, thefive-button interaction was demonstrated,

and the observer trained for 3 to 4 mm-utes. The monitor was initially blocked with alarge piece of cardboard for each trial. To

start each trial, the experimenter dis-played the appropriate study on the moni-

ton, removed the cardboard and allowedthe observer to see the images, and gavethe observer the requisition information.The observer then scrolled back and forththrough the images, changed intensity

windows as needed, and dictated a report.

Data Collection

Verbal protocol-that is, verbal com-ments made by the observer during the

experiments-was collected throughout

the study. At the end of each session, theexperimenter conducted an unstructured

interview to determine the observer’s feel-

ings and opinions with regard to worksta-

tion versus film alternator interpretation.

Besides videorecording the postsessionreview and analysis, the experimenter also

used a stopwatch to measure the time

used to load the films onto the alternator,

the time to file the films back into the pa-tient folder, and the total time of the inter-

pretation, with precision of about 1 sec-

ond.In a well-designed PACS environment,

the radiologist should not have to waitwhile the workstation locates, moves, and

displays the required case. Avoiding this

waiting time can be accomplished either

by the workstation predicting which case

will be needed next and “prefetching” it(21) or by using an extremely high-speed

image storage device and network to

transmit the study in a few seconds (2).Because the radiologist should not have towait for images to be loaded into a well-

designed PACS workstation, the time to

load the images into the workstation wasnot included in the interpretation time forthis experiment. Whether film load andunload time should be included in filminterpretation time depends on the opera-

tional characteristics of the clinical envi-ronment of the reader. We report bothtotal film interpretation time (includingthe time to load and unload the films) aswell as prehung film times (without thetime to load and unload the films) to allow

the reader to make institutionally specificcomparisons.

Data Analysis

Exploratory analysis was used to com-

pare identity, logarithmic, and inverse

transformations of response times to en-

sure that the distribution was acceptably

Gaussian. The distribution of the untrans-

formed data was judged to be the best.

Hence, response times are analyzedthroughout. The univariate approach torepeated measures analysis of variance(22) was conducted on the total time, with

trial (numbers 1 through 5) and method(film vs workstation) as repeated factors.Appropriate confidence intervals were

created to assess uncertainty of estimates.

We measured interpretation accuracy toensure valid interpretation times. Accu-

racy of the dictated reports was analyzedby a radiologist “grader” blinded to ob-server and interpretation method. All four

reports as well as the requisition form and

original films were available. The tran-

scnibed reports were evaluated as follows.

A list of findings was generated for eachreport. Then, a findings list was generated

for each case, on the basis of the patientrecord, radiologic reports, and the filmsand images. The findings for each casewere further divided into “critical find-ings,” which would affect patient care de-

cisions, “relevant findings” related to theclinical question contained in the requisi-

tion form, and additional “noncritical”

findings. Finally, the grader examinedeach report and assigned one of the fol-lowing overall grades: excellent-no erro-

The average time needed at theworkstation to interpret the CT stud-

ies was 5.65 minutes (Table 1). The

total film time (with loading and un-loading) averaged 6.21 minutes, while

prehung film (without loading andunloading) averaged 5.01 minutes.Observers 2, 3, and 4 were faster with

the workstation than with film, in-cluding loading and unloading time.Observer 1 was faster with film.

Analysis of total time yielded three

nonsignificant tests: (a) method by

trial (F = 1.56 on 4 and 12 df with

P = .25, Geisser-Greenhouse epsilon

of .47), (b) trial (F = 0.66 on 4 and 12 dfwith P = .63, Geisser-Greenhouse ep-

silon of .30), and (c) method (F = 1.38

on 1 and 3 dfwith epsilon automati-cally 1.0). The small number of obser-

vations may have limited the sensitiv-

ity of the design. Hence, a confidence

interval was created for the mean dif-ference between the method totaltimes. The mean difference of the four

observations (averaging across the

nonsignificant trial factor) was 0.56

minutes, with a standard deviation of0.95 and a standard error of 0.47. For

the Student t statistic with 3 df, a 95%confidence interval for the mean dif-

ference between workstation and to-tal film is therefore 0.56 ± 0.47 (2.353),

or equivalently, in minutes (-0.55,1.66). Retrospective power analysis

indicates that with the same observed

values, 16 observers rather than four

would have been required to showthat the workstation was faster than

film at 95% confidence.Prehung film times also were com-

pared to workstation total time. The

analysis yielded three nonsignificant

tests: (a) method by trial (F = 1.60 on

4 and 12 dfwith P = .24, Geisser-

Greenhouse epsilon of .47), (b) trial

(F = 0.62 on 4 and 12 dfwith P = .66,

Geisser-Gneenhouse epsilon of .30),

and (c) method (F = 2.51 on 1 and 3 dfwith epsilon automatically 1.0). The

mean difference of the four observa-

tions for prehung film time minus

workstation total time (averaging

across the nonsignificant trial factor)

was -0.64 minutes, with a standard

deviation of 0.81 and a standard error

of 0.40. For t with 3 df, a 95% confi-

Observer

Cases

A B C D E F G H I J

Film E E E E EWorkstation E A E E E

2

Film A A E E EWorkstation E E E E A

3Film A E E E A

Workstation MD MD MD E MD4

Film E E E E EWorkstation E E E A E

Note-A = acceptable, E = excellent, MD = missing data point. There were no unacceptable reports.

Rating

568 #{149}Radiology May 1993

dence interval for the mean differencebetween total workstation time andprehung film time is therefore -1.58± 0.40 (2.353), or equivalently, in mm-utes, (-1.58, 0.30).

In short, we are 95% confident thatthe FilmStrip workstation is no morethan 1 minute and 40 seconds fasterthan film with loading and unloadingand no more than 33 seconds slower.Furthermore, we are 95% confidentthat the workstation is no more than18 seconds faster than prehung film

and no more than one minute and 35seconds slower.

Interpretation accuracy with both

film and workstation was nearly iden-tical, with no unacceptable reportsdictated for either film or workstation(Tables 2, 3). There was no noticeabledifference in performance between

the two methods, with film alternatorand workstation having almost thesame number of excellent and accept-able reports. Technical difficultieswith one dictation tape resulted infour dictated reports that could not beanalyzed. Learning effect precludedretesting that observer for those cases.

Observations

Observers expressed feelings of

comfort and seemed to feel in controlwhile using the workstation. Therewas no observed fumbling with thecritical up and down buttons. Allobservers believed that image sizeand quality were acceptable and thatthe FilmStrip design provided suffi-cient display area, speed, and simplic-ity to be clinically useful. Most impor-tant, they all said they would bewilling to use a similar system in aclinical setting.

While three observers were fasterwith the workstation than with film,the fastest observer (observer 1) wasfasten with film. While being inter-viewed, observer 1 indicated that hehad developed and refined hismethod of interpreting CT studieswith a horizontal alternator ovenmany years. He stated that he ex-pected to be able to interpret CTmuch faster with FilmStrip after moretraining, as he would have more timeto refine his interpretation behavior tobest match the advantages and draw-backs of electronic display.

Several minor problems were en-countered. First, observers occasion-ally had to look down at the keyboard

to locate the intensity window keys,increasing the duration of the inter-pretation. Second, we used a scrollincrement of two rows (half screen)per up or down command. The ob-

Table 2

Interpretation Accuracy

servers generally managed to main-tam spatial context while scrollingand could achieve rapid movementthrough the examination. The two-

row scroll, however, sometimes con-fused the observers because of thevisual similarity of the unnumberedsections in adjacent rows; on severaloccasions, the observers reinterpretedtwo rows after scrolling. Third, whileall the observers stated that the de-fault windows were adequate, two

wanted to adjust the default liver in-tensity window for several cases.

DISCUSSION

After 3-4 minutes of training, averageinterpretation time with the worksta-tion was 34 seconds faster than with thealternator when the time to load and

unload the ifims was included. Giventhe confidence intervals described inour results, we are comfortable in con-cluding that workstation interpretationtime is clinically equivalent to total filmalternator time, including loading andunloading of films.

Interpretation of studies with theworkstation averaged 33 seconds slowerthan with prehung film, with a confi-dence interval ranging from 18 secondsfaster to 1 minute and 35 seconds

slower. Thus, it is likely that prehungfilm would be slightly faster than the

workstation in an efficient film opera-tion. Given the work patterns of thetypical CT radiologist reading 20-50cases per day, not to mention the filmhandling patterns of the typical clinicaloperation, we believe that in general,however, the use of a workstation inlieu of prehung film would have no sig-nificant impact on daily productivity.

Further, we expect reductions in work-station interpretation time after severalminor improvements are made to theuser interface design and after radiolo-gists receive additional training and be-

Table 3

Summarized Interpretation Accuracy

Method ExcellentAc-

ceptableUnac-

ceptable

Film 16(80) 4(20) 0Workstation 13 (81) 3 (19) 0

Note-Values in parentheses are percent-ages.

come more familiar with workstationinteraction and learn how best to inte-grate it into their clinical activity.

Therefore, given the similarity in in-terpretation times and the logistic ad-vantages of PACS, we believe that aneffective PACS with a workstation simi-lar to FilmStrip should be a clinicallyequivalent alternative to film for clinicalchest CT, especially when images areneeded in several locations at the sametime during patient work-up. Further,we believe that because of the similarityin image interaction, these results canbe extended to use in general CT, MRimaging, and US.

Caveats

Observers-The observers were suffi-

ciently computer literate to use word

processors. It is not clear that similarlyrapid acceptance would be found withradiologists who feel uncomfortable in-

teracting with computers, but we wouldexpect similar interpretation times aftersufficient training.

Cases-Each case was read the samenumber of times for a given method

and observer, controlling for the relativeeffect of case on interpretation time. Ab-solute interpretation times for both filmand workstation, however, were af-fected by the complex abnormal caseswe selected.

Fatigue-Each interpretation session

Volume 187 #{149}Number 2 Radiology #{149}569

with the workstation lasted less than 1hour. It is possible that after longer in-terpretation sessions, mental and eyefatigue of the film alternator and work-

station might affect relative perfor-mance or comfort.

Single versus multiple examinations.-Our interpretation tasks involved onlysingle CT studies, with no comparison

of serial studies. A two-monitor versionof FilmStrip, however, with each moni-tor containing a filmstrip of a differentstudy and operated either indepen-

dently or in a linked way can be used to

simultaneously present serial studies.

Implications for FutureWorkstation Design

Speed-Fast image display is essential

for a fast interpretation time. A typicalinterpretation may require from 30 to 60scrolling operations, so decreasing im-age display time from 2.0 seconds to 0.1second could decrease interpretationtime by up to 1.9 minutes. Ideally, im-age display time would be in the 0.1-second range, with no apparent image

display lag after a scrolling command.Screen space-Previous work (23)

with an eye tracker suggests that radiol-

ogists need to view simultaneously at

least six to eight images in a multiple-image mosaic display for effective single

CT study interpretation. Additionally,with more images displayed simulta-neously, fewer scroll operations areneeded, which further reduces interpre-tation time. On the other hand, toomany monitors may spread the images

over too large a physical area and actu-ally slow the interaction. A multiple-image mosaic display of from eight to 12images per study on one or two moni-tons with a quick response time mayprovide an effective balance for inter-

pretation of single studies. A high-speedcine display (1 1) sequentially showingsingle images has the potential togreatly reduce screen space require-ments for a workstation, but more studyis needed before the relative interpreta-

lion speed for a primary interpretationtask involving report dictation can bedetermined for the cine mode.

Simplicity-Our experimental resultssuggest that extremely simple interac-lion may be important. As suggested byBrown et al (9), we did not includezooming, general roaming, a magnify-ing glass, individual image movement,or many other commonly availablefunctions. While these functions mayprovide some additional utility, theyincrease overall interpretation time, andthey make systems harder to learn anduse.

FilmStrip is a prototype developed tofocus on the computer-human interac-tion aspects of CT interpretation, and as

such, it omits the essential connectionsto radiology information systems, hospi-tal information systems, and the generalPACS environment. A clinically viableCT workstation might also include dy-namic intensity windowing and otherimage processing functions for occa-sional use; linear, area, and volumemeasuring, and cine display, multipla-nar reformation, three-dimensional vol-ume rendering, and Hounsfeld unitmeasuring. A more complex interactionmay also be required for a workstationdesigned to interpret multiple modali-ties. The integration of this additionalfunction will necessarily increase thecomplexity of the interaction and possi-bly increase interpretation time. Fur-then, it is possible that a well-designed,mouse-based interface may be superiorto our five-button control panel for amore complex interaction.

While we encountered no critical in-terpretation quality problems with ourgeneral preset intensity windows, ver-bal comments from the observers mdi-cated the desire for intensity windowvalues set for each particular study.While dynamic intensity windowing bythe radiologist is a possible solution, itoften takes more than 10 seconds peradjustment, which potentially decreasesoverall productivity. A clinical operationalso can be designed to have technolo-

gists preselect intensity windows foreach study. The relative cost-effective-ness of these two approaches is beyondthe scope of this article.

Cost-The hardware used for thisexperiment cost about $65,000 in 1992,and the software development costs of asimilar commercial product might bedouble or triple this expense. Until low-er-cost 2,048 x 2,560-pixel monitors be-come available, their practical radiologicuse may be justified only for high-vol-

ume modalities such as computed radi-ography. Thus, for CT and MR imagingalone, a superior workstation might bebased on a relatively low-cost prototypeworkstation that we have built, calledFilmStriplet, which uses a standardworkstation (Sparc 2; Sun Microsystems)expanded to include 128 Mbytes ofmain memory, along with two 1,024 x1,024-pixel monitors. This Sun worksta-tion has a hardware cost of about$15,000, although software costs wouldmake a similar commercial CT worksta-tion considerably more expensive. Film-Striplet can display eight full-resolutionCT images in about 0.05-0.1 second andallows rapid scrolling and selection offixed-intensity windows. Further studyis needed, however, before the potential

role of FilmStriplet in clinical diagnosiscan be established. U

Acknowledgments: We thank Joseph Lee,MD, Richard Clark, MD, and Gene Johnston,PhD, for help in preparation of this manuscript.

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