1. RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
Part 19.06: Optimization of protection in Mammography
Practical exercise
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Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
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IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

2. Part No...., Module No....Lesson No
Module title
Overview
To be able to apply quality control protocol to mammography equipment
To measure, by different methods, the focal spot size of a mammographic installation
Interpretation of results
Explanation or/and additional information
Instructions for the lecturer/trainer
19.06 : Optimization of protection in Mammography
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

3. Part 19.06: Optimization of protection in Mammography
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 19.06: Optimization of protection in Mammography
Focal Spot Size measurements
Part …: (Add part number and title)
Module…: (Add module number and title)
Lesson …: (Add session number and title)
Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.)
Duration: (Add presentation time or duration of the session – hrs)
Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate)
References: (List the references for the session)
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

4. Focal spot size – Required equipment
1 - Star pattern
2 - Resolution bar
pattern
3- Pinhole and
slit camera
6X magnifying loupe and reticule
19.06 : Optimization of protection in Mammography

5. Focal spot size (star pattern) (1)
The focal spot size measurement is intended to determine its physical dimensions at installation or when resolution has markedly decreased. For routine quality control the evaluation of spatial resolution is considered adequate
A magnified X-ray image of the test device is produced using a mammography screen-film cassette
19.06 : Optimization of protection in Mammography

6. Focal spot size (star pattern) (2)
Select the focal spot size, 28 kV, and an mAs to obtain an optical density between 0.80 and 1.40 (measured in the central area of the image)
The image should be imaged at the reference point of the image plane, which is located at 60 mm from the chest wall side and laterally centred
19.06 : Optimization of protection in Mammography

7. Focal spot size (star pattern) (2) (cont’d)
Remove the compression device and place the test stand on top of the bucky (breast table)
Place the test device on top of the cassette
19.06 : Optimization of protection in Mammography

8. Focal spot size (star pattern) (2) (cont’d)
According the IEC norm :
a nominal 0.3 focal spot should not exceed 0.45 mm in width and 0.65 mm in length
a nominal 0.4 focal spot should not exceed 0.60 mm in width and 0.85 mm in length
19.06 : Optimization of protection in Mammography

9. Focal spot size (star pattern) (2) (cont’d)
The focal spot dimensions can be estimated from the 'blurring diameter' on the image (magnification 2.5 to 3 times) of the star pattern
The distance between the outermost blurred regions is measured in two directions: perpendicular and parallel to the tube axis
19.06 : Optimization of protection in Mammography

10. Focal spot size (star pattern) (2) (cont’d)
The focal spot size is calculated as:
where :
θ : the angle of the radiopaque spokes (1° or 0.5°),
Dblur : the diameter of the blur.
Mstar : the magnification factor determined by taking the ratio of the diameter of the star pattern on the acquired image (Dimage) to the diameter of the star pattern (Dstar)
19.06 : Optimization of protection in Mammography

11. Focal spot size (slit camera) (1)
To determine the focal spot dimensions (f) with a slit camera, a 10 μm slit is used.
Note: Produce two magnified images (magnification 2.5 to 3 times) of the slit perpendicular and parallel to the tube axis.
The dimensions of the focal spot are derived by measuring each image using an a 6X magnifying loupe with a reticule and correcting for the magnification factor according to:
f = F/Mslit
19.06 : Optimization of protection in Mammography

12. Focal spot size (slit camera) (1) cont’d
where:
F : the width of the slit camera
(Mslit) : the magnification factor determined by measuring the distance from the slit to the plane of the film (dslit-to-film) and the distance from the focal spot to the plane of the slit (dfocal spot-to-slit)
Mslit = dslit-to-film /dfocal spot-to-slit
NB: The method requires a higher exposure than the star pattern method.
19.06 : Optimization of protection in Mammography

13. Focal spot size (pinhole) (1)
To determine the focal spot dimensions (f) with a pinhole, a 30 μm gold-platinum alloy pinhole is used.
Note: Produce a magnified image (magnification 2.5 to 3 times) of the pinhole.
The dimensions of the focal spot are derived by measuring the image with a 6X magnifying loupe and a reticule, and correcting for the magnification factor according to:
f = F/Mpinhole
19.06 : Optimization of protection in Mammography

14. Focal spot size Pinhole camera images of focal spot
19.06 : Optimization of protection in Mammography

15. Focal spot size (pinhole) (1) cont’d
where:
F : the size of the imaged focal spot.
Mpinhole : the magnification factor determined by measuring the distance from the pinhole to the plane of the film (dpinhole-to-film) and the distance from the focal spot to the plane of the pinhole (dfocal spot-to-pinhole)
Mpinhole = dpinhole-to-film /dfocal spot-to-pinhole
NB: The method requires a higher exposure than
the star pattern method.
19.06 : Optimization of protection in Mammography

16. Where to Get More Information
European protocol for the quality control of the physical and technical aspects of mammography screening.
American College of Radiology Mammography Quality Control Manual, Reston VA, 1999.
Quality Control in Diagnostic Imaging, Gray JE, Winkler NT, Stears J, Frank ED. Available at no cost.
19.06 : Optimization of protection in Mammography