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International Atomic Energy AgencyIAEA

Examples of Good & Bad Examples of Good & Bad Practice (physical factors)Practice (physical factors)

L 12a

Lecture 12 : Examples of Good & Bad Practice (physical factors) 2Radiation Protection in Cardiology IAEA

Educational ObjectivesEducational Objectives

1. How wedge filter & field size affect the skin dose

2. When and how to use wedge filter


Answer True or FalseAnswer True or False

1. Wedge filter should not be used in flat panel detectors.

2. Size of the radiation field is similar in all the cardiology procedures, then collimation is not necessary.

3. In cardiology procedures, the hands of the medical specialists are never in the direct radiation field.


Topics includedTopics included

• Use of wedge filter.

• Collimation (filed size).

• Use of cine instead of fluoroscopy.

• Use of cine to verify the proper position of the table.

• Hands inside the direct beam.


Philips systems


Example of lack of wedge filter use in a left projection. Image quality is not good (too bright in the upper left corner of the image) and in addition, more dose per frame than necessary. Bad practice!.

Series 14:KVP: 88Distance source to detector: 1048Exposure time 8 X-ray tube current 467 Intensifier size 169.9 mm Positioner primary angle 5.2 (LAO)Positioner secondary angle 28.313 Sep 04; 40414


Example of lack of wedge filter use in a right projection. Image quality is not good (too bright in the upper right corner of the image) and in addition, more dose per frame than necessary. . Bad practice!.

Series 21:KVP 87Distance source to detector 995 Exposure time 8 X-ray tube current 472 Positioner primary angle - 41.1 (RAO)Positioner secondary angle 28.8

13 Sep 04; 40414


Example of appropriate use of the wedge filter. (flat panel). Good practice!.

Series : 6(0008,0020) : Study Date : 21/09/2004 (0008,0080) : Institution Name : HOSPITAL SEVERO OCHOA (0008,1090) : Manufacturer's Model Name : INTEGRIS Allura Flat Detector (0018,0060) : KVP : 78.0 (0018,1110) : Distance Source to Detector : 1.08(0018,1111) : Distance Source to Patient : 0.765 (?)(0018,1150) : Exposure Time : 6(0018,1151) : X-ray Tube Current : 812 (0018,1510) : Positioner Primary Angle : -31.2(0018,1511) : Positioner Secondary Angle : 32.2


No wedge filter used. Image partially saturated.Bad practice!.

Lecture 12 : Examples of Good & Bad Practice (physical factors) 10Radiation Protection in Cardiology IAEA0.8 mGy/fr (60% more)0.5 mGy/fr


proper filtering

improper filtering causes image deterioration (II Philips Integris H3000)

Image Intensifier versus Flat detector

Filtering prevents image saturation in low absorption areas


Image from GE-INNOVA FD

Improper filtering does not cause image deterioration

Image Intensifier versus Flat detector


Use of wedge filter in right Use of wedge filter in right projectionsprojections


Effect of the wedge filter in skin dose distribution (right projections). Saving skin dose and improving image quality. Good practice!.

Lecture 12 : Examples of Good & Bad Practice (physical factors) 16Radiation Protection in Cardiology IAEAAreas in red are saturated in the slow film. Skin dose more than 0.8 Gy.


Philips Integris: Use of wedge Philips Integris: Use of wedge filter in left projectionsfilter in left projections


Effect of the wedge filter in skin dose distribution (left projections). Saving skin dose and improving image quality. Good practice!.


Use of wedge filter in right and Use of wedge filter in right and left projectionsleft projections


Geometry with small field sizeGeometry with small field size


26 cm2

68 cm2

28 cm2


Geometry with big field sizeGeometry with big field size


1.2 Gy

0.6 Gy113 cm2

41 cm2


No wedge filter used. Geometry No wedge filter used. Geometry with big radiation field size. with big radiation field size.

Overlapping of radiation fields Overlapping of radiation fields could occur.could occur.


91 cm2

234 cm2

319 cm2


Hands in the direct radiation Hands in the direct radiation fieldfield


This is a bad practice. The hand of the cardiologist is in the direct radiation field during fluoroscopy. This should be avoided.


This is a bad practice. The hand of the cardiologist is in the direct radiation field and a cine run is acquired (dose is a factor of 10 higher than during fluoroscopy). This should be avoided.


This is a bad practice. The hand of the cardiologist is in the direct radiation field and a (second) cine run is acquired (dose is a factor of 10 higher than during fluoroscopy). This should be avoided.


The use of cine instead of The use of cine instead of fluoroscopyfluoroscopy


CommentsComments

• One series with more that 999 frames (more than 80 seconds)

• Probably a fellow uses cine instead of fluoroscopy (images on that series support this assumption).

• 80 seconds of fluoroscopy (low mode) could be 30 mGy in the skin. 1000 frames can be 500 mGy (76 kV; 857 mA; 7 ms)!!!.

• Lateral projection: 89º; -5º. The sternum of the patient was in the beam during part of the series. Table is moved up.


The sternum of the patient is now in the beam, Fellow is trying to find the good position at the isocenter. Table should be moved up in this case.


Answer True or FalseAnswer True or False

1. Wedge filter should be used in the same position for right and left projections.

2. Wedge filter improve the visualization of the images but increase the skin dose of the patient.

3. Typically one cine frame requires 10 times for dose at the entrance of the patient than a fluoroscopy image.


Additional InformationAdditional Information


• Patients who had multiple coronary angiographies and who underwent more than four PTCAs. 7824 PTCAs performed during 14 years was analysed.• 14 patients were included in the study. Each patient had undergone between 4 and 14 coronary angiographies and between 5 and 10 PTCAs, performed over a period of 2-10 years.


• Mean values of maximum skin dose per procedure were 217 mGy for the diagnostic studies and 391 mGy for the PTCAs. • Only a slight radiation skin injury was clinically demonstrated in one patient with a history of 10 coronary angiographies and 10 PTCAs (estimated maximum skin dose 9.5 Gy).


CONCLUSION:

IC procedures performed on modern X-ray systems under QA programmes and by cardiologists trained in RP, repetition of procedures is not the main cause of possible skin radiation injuries.

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Documents

use of wedge filter

wedge filter field size

false wedge filter

image quality

use of cine

good practice

direct radiation field

image saturation