Dose Optimization in

Interventional Radiology

Aida M. Lobriguito, MSc, CSci, MIPEM

Medical Physicist

King Fahad Medical City

National Training Course on Justification and Optimization

of Protection in Diagnostic X-ray Imaging and Interventional

Radiology (18-20 October 2016)

INTRODUCTION

% IR Procedures from US Survey

Source: NCRP Report No. 160 Ionizing Radiation Exposure of the Population of the US

What is Interventional

radiology ? Interventional radiology is concerned with

providing diagnosis and treatment of disease

by a variety of percutaneous procedures

performed under the guidance of radiologic

imaging performed by :

Radiologists

Cardiologists

Neurologists

Other clinicians

Who are at risk in IR

procedures?

Patients

Staff

For skin injuries and eye lens

opacities (cataract)

What is Optimization?

Optimization is the radiation

dose to the patient that is

commensurate with the

medical purpose and

avoidance of radiation that is

clinically unnecessary or

unproductive.

It involves the design,

appropriate selection, and

use of equipment, protection

tools and working

procedures.

Interventional

Radiology

CT

Radiography

Comparison of radiography with IR

and cardiology doses

Procedure Mean Effective Dose

(mSv)

Chest (radiography) 0.03

Abdomen (radiography) 0.6

ERCP (endoscopic retrograde 3.9

choangiopancreatography)

Cardiology:

Coronary angiography (CA) 3.1

PTCA (percutaneous trnasluminal 15.1

coronary angioplasty)

Cardiovascular embolization 19.5

Interventional radiology:

Renal angiography 13.7

Vascular stenting 10.4

TIPS (transjugular intrahepatic 53.6

portosystemic shunt)

PATIENTS: RISKS AND

SAFETY

Deterministic Effects

• Tissue reactions/Skin injuries

• Cataract

Skin injury from

Transjugular

Intrahepatic

Portosystemic Shunt -

TIPS

Stochastic Effects

Procedure Approx. onset 1. Erythema at 2Gy hours 2. Permanent epilation at 7Gy 3 wk 3. Delayed skin necrosis at 12 Gy >1 yr 4. Moist desquamation at 18 Gy 4 wk

5

Acute radiation doses, delivered to tissues

during a single procedure or closely

spaced procedures, will cause:

(a) 6-8 weeks after multiple coronary angiography and angioplasty

procedures.

(b) 16-21 weeks

(c) 18-21 months after the procedures showing tissue necrosis .

(d) Close-up photograph of the lesion shown in (c).

(e) Photograph after skin grafting. (Photographs courtesy of T. Shope & ICRP).

(d) (e)

(a) (c)

(b)

Coronary angioplasty twice in a day followed

by bypass graft because of complication. Dose

20 Gy (ICRP 85)

Deterministic effects caused by cell death:

burns, organ failure, death

IAEA Training Course on Radiation Protection for Doctors (non-radiologists, non-cardiologists) using

Fluoroscopy

At 3 wks At 6.5 mos Surgical flap

Following ablation procedure with arm in beam near port and separator

one removed. About 20 minutes of fluoroscopy.

Reproduced from Wagner – Archer,

Minimizing Risks from Fluoroscopic X Rays,

3rd ed, Houston, TX, R. M. Partnership, 2000

Reports Received by FDA of Skin Injury from Fluoroscopy.

Procedure with

Report of Injury

Number of Injuries

Reported from Procedure

RF cardiac catheter ablation 12 Catheter placement for chemotherapy 1 Transjugular interhepatic portosystemic shunt 3 Coronary angioplasty 4 Renal angioplasty 2 Multiple hepatic/biliary procedures 3 (angioplasty, stent placement, biopsy, etc.) Percutaneous choloangiogram followed 1 by multiple embolizations

Skin Injuries: IR and IC

Why do they occur?

No training in radiation protection

for those performing these studies,

of the:

• Cardiologist

• Urologist

• Gastro-enterologist

• Orthopedic Surgeon

• Vascular Surgeon

• Traumatologist

• Pediatrician

• Anesthesiologist

Skin Injuries are

associated with:

• Complex procedure with lengthy time

over the same skin area

• Prolonged use of high-dose modes of

operation

• Unnecessary body parts in the field of the X

ray beam

• Large patients or steep beam angles requiring

transmission through thick body mass

Skin Injuries are

associated with:

• Patients with health conditions that

predispose them to radiation injury

• Multiple procedures in the same patient over

short periods of time

• Lack of dose monitoring to warn physicians

that high doses are accumulating

• Inexperienced physicians

Radiation Dose-determining Factors

Equipment

Patient Weight

Diagnostic vs. Interventional

Complexity of the Procedure

Constant potential generator

Arc system (X Ray tube down)

High efficiency intensifier/

flat panel detectors

Easy operational controls

Good image saving and retrieving (last hold)

HOW MUST BE AN X Ray SYSTEM BE "SPECIFICALLY DESIGNED" FOR

INTERVENTIONAL RADIOLOGY?

PATIENT DOSE REDUCTION

MEASURES

Performance of the X Ray system used

Old versus new

Use of dedicated units

Well calibrated

With dose reduction features

Knowledge of the operator on the use of

the unit

Fluoroscopy time

Not a good indicator of dose but is good

to evaluate quality of performance

IR/Cardiology procedures

Important factors for dose reduction

Complexity of procedures

Needs training of physician on the procedure

Number of series (Images)

Use cine sparingly.

For pediatric patients at least 60 frames per

sec.

Patient size - affects exposure factors

Available protection tools

Dose monitoring and management

IR/Cardiology procedures

Important factors for dose reduction

THE KNOWLEDGE OF DOSE RATES FOR

DIFFERENT OPERATIONAL MODES AND

FOR DIFFERENT INTENSIFIER INPUT SIZE

IS IMPORTANT

THEN, IT IS POSSIBLE TO HAVE

CRITERIA FOR THE CORRECT

USE OF DIFFERENT OPERATION

MODES

Perform routine and annual QC tests and make

corrections when needed.

Establish image quality criteria.

QA/QC

Equipment

Patient Dose Management

Justification of procedure

Equipment condition – QC performed, well

calibrated

Procedure to be done: simple or complex??

Expected doses known? Verified?

Informed consent

Before the Procedure

During the Procedure

• Area Product (KAP or DAP)

mGy mGy

mGy

KAP or DAP meter - needs proper calibration.

Values can be used to determine equivalent or

effective dose to the whole body.

Measure Patient Doses

Setting of Dose Notification

New machines have alarm system.

Set Rules for patient follow up

Establish Reference levels

“Patient risk”

“Clinical protocol”

“Equipment performance”

Reference levels (indicative of the state of the

practice): an instrument to help operators to conduct

optimized procedures with reference to patient

exposure

Required by international (IAEA) and national

regulations For complex procedures reference levels should

include:

the complexity of the procedures.

more parameters like:

(European Dimond Consortium recommendations)

Procedure: CA PTCA

DAP (Gycm2) 57 94

Fluoroscopy time (min) 6 16

No. of frames 1270 1355

Reference levels in interventional

cardiology

(European proposal 2003)

DIMOND EU project. E.Neofotistou, et al, Preliminary reference levels in interventional

cardiology, J.Eur.Radiol, 2003

Dosimetry Records

• Measure and Record Patient Radiation Dose

• Record Fluoroscopy Time

• Record Available Measures

– DAP (Dose Area Product)

– Cumulative Dose

– Skin Dose

• Use dose conversion factors such as effective

dose per DAP

After the Procedure

Dosimetry Follow-UP

• Develop Methods to Quantify Late Effects

– Design medical records to clearly document the number

and types of interventional procedures received by the

patient.

– Maintain a database of all patients with procedures and

dose information.

– Review dose information to identify patients with high

doses (>3Gy) for follow-up.

– Establish procedures for follow-up; including skin

examination at 30 days.

After the Procedure

• Remove the grid during procedures on small patients or when the image intensifier cannot be placed close to the patient.

• When the procedure is unexpectedly prolonged, consider positioning the patient or altering the X ray field or other means to alter beam angulation so that the same area of skin is not continuously in the direct X Ray field.

• Patients should be counseled on radiation risks if the procedure carries a significant risk of such injury.

Practical Actions in Controlling

Patient Doses

Practical Actions in Controlling Dose

• Records of exposure should be kept if the estimated maximum cumulative dose to skin is 3Gy or above.

• All patients with estimated skin doses of 3 Gy or above should be followed up 10 to 14 days after exposure.

• The patient’s personal physician should be informed of the possibility of radiation effects.

• If the dose is sufficient to cause observable effects,

• the patient should be counseled after the procedure.

• A system to identify repeated procedures should be set up.

IAEA-KFSHRC Highest MSD and DAP values

for 9 Procedures

Procedure Highest MSD Highest Total DAP

(mGy) (cGy-cm2)

CA 889.2 13,784

PTCA 4,470 33,658

TIPSS 734.7 17,177

Cerebral 713.8 Not available

PTC 983.0 not available

Abdomen 675.6 30,794

Nephrostomy 84.1 1,887

Gastrostomy 349 6,342.7

Embolization 499.9 11, 498.4

Findings & Recommendations

A review of the protocols for TIPSS and PTCA

should be made and standardized. Dose reductions

techniques should be determined.

High DAP values are due to cineradiography as can be

seen from the fluoro time variances. Dose reduction

techniques for should be considered such as no. of

frames.

Image quality criteria and assessment should be set

and standardized.

Counseling of patients especially for PTCA should be

made when doses exceed 2 Gy and dose should be

recorded on the patient’s chart.

Findings & Recommendations

Skills and training needs of operators should be

assessed and structured training program should be

developed.

Introduction of reference dose levels should be made.

Although the use of Mathlab based program showed

to be efficient in dose evaluation, more clinical trials

should be made by intercomparing with other

institutions.

More data should be collected for low frequency

procedures for validation.

Golden Rules

• Radiation dose to the patient should be limited to

that required for the procedure being performed

• Appropriate collimation

• Patient should be positioned as close as reasonably

possible to the image receptor

• Distance between the patient and the X-ray tube

should be maximized to the extent practicable

• Each arm of the patient should be kept outside the

radiation field unless an arm is intentionally imaged

as part of the procedure

Golden Rules

• Lowest dose rate that is clinically

• When electronic magnification is necessary, the lowest

acceptable magnification factor should be used

• Fluoroscopy should be used sparingly and only when

real-time imaging guidance is needed

• Last-image-hold feature or loop replay should be used

whenever possible

• Image acquisition should be activated only when higher

quality image review is essential, and it should be limited

to the frame rate and run duration necessary to

accomplish the immediate task

• In some cases, retrospectively stored fluoroscopy may

reduce the need for image acquisition

STAFF: RISKS AND SAFETY

Deterministic effects in cardiology

studies

Skin injuries on hand

Eye cataract

Staff

Shielding & Positioning Eye Shielding Is Imperative

• Leaded Ceiling Shield 98% reduction.

• Leaded Glasses Shield ~74-91%

• Differences in performance related to operator position, likely representing interplay of design and fit.

• Sports wraparound or side shields important. Rehani. Cataract RASSC Dec

2011

Diligent use personal protective

equipment (PPE).

Lead goggles provide effective

protection but there are issues

of comfort.

Use of suspended shields

protects head and neck.

Use of PPE can reduce eye

doses to about 3/10 of the dose

limit.

What can be done in the light of the new

recommendation for the lens of the eye?

It is important to note that…

Reported eye lens doses:

0.3-11 mGy/study (without use of

protective devices)

0.011-0.33 mGy/study (with protective devices)

Rehani. Cataract RASSC Dec

2011

45

3 As

Awareness

Appropriateness

Audit

Thank you !