4. Initial Checks Physicist
5.6 Image Quality and Radiation Dose
5.6.1 Objective
To ensure that adequate image quality is achieved.
Measure the mean glandular dose to ensure that it does not exceed 3.0 mGy, which is the maximum value allowed in the regulations for screen-film systems as well as for full field digital mammography (FFDM) systems.
5.6.2 Required Equipment
a) Dosimeter calibrated at the mammography X-ray beam energies b) Accreditation phantom
c) Compression paddle 24x30
NOTE!NOTE!
HVL Values will be required to calculate Radiation Dose.
5.6.3 Procedure
1. Login according to the section 2. Start Up and Login.
2. Enter a new patient by pressing Patient Registration icon, see Figure 1, Position 1.
3. Create a new patient record in the local database. Fill in: Last Name: Test_Six
First Name: Mean Glandular Dose
Patient ID: day+time when the test is performed (example: 200411281350)
DOB: 05 05 1955 Gender: Other 4. Press Exam button.
5. Choose procedure FD QC processed. 6. Install the compression paddle.
7. Center the phantom left to right and place dosimeter next to phantom and about 4 cm from chest wall edge, see Figure 24. Try to get the dosimeter at the same height as the phantom top. Compress phantom until OpComp indicator light is lit, see Figure 11.
Image Quality and Radiation Dose
Figure 24 Positioning of the accreditation phantom
8. Choose Opdose 2 on the control console. Select AEC sensor 2 at AWS, see section 4.1 Site Audit / Evaluation of Technologist QC Program.
9. Use H mode.
10. Double click on the first image in the icon gallery, see Figure 3, Position 2. 11. Select the automatic decompression button on the control console.
12. Make an exposure and check if an automatic release of the compression paddle was performed and note in Appendix 2, Test Form 5.6 Image Quality and
Radiation Dose.
NOTE!NOTE!
Record all values in the appropriate place in section 5.6 Image Quality and Radiation Dose and calculate the mean glandular dose. Other accepted methods for calculating mean glandular dose may also be used.
13. Examine the image at acquisition size (To get full resolution click top “image” -> “acquisition size.) optimize window level settings. Determine how many fibers, specks and masses can be visualized. Always count the number of visible objects from the largest object of a given type downward. Note the results in
Appendix 2, Test Form 5.6 Image Quality and Radiation Dose.
XXX XXX
Fibers
Specks
Image Quality and Radiation Dose
14. If a problem exists while looking at the image on the AWS send the image to the diagnostic reviewstation or printer and then examine the image.
15. Record the thickness reported in the image annotation, see Appendix 2, Image
Quality and Radiation Dose.
16. Optional: Repeat radiation dose and image quality tests for D Mode. (Unless D Mode is the clinical Technique).
17. Choose the Close patient tab card and close patient by clicking this button.
5.6.4 Analysis
• Count each fiber as one point if the full length of the fiber is visible and the location and orientation of the fiber are correct. Count a fiber as 0.5 point if not all but more than half of the fiber is visible and its location and orientation are correct. If a fiber-like artifact appears anywhere in the image but is not in an appropriate location or orientation, deduct the "artifactual" fiber from the last "real" fiber scored if the artifactual fiber is equally or more apparent. • When studying the specks, it can be useful to take advantage of the zoom
and invert function. Each speck group shall be counted as one point. A full speck group is counted if four or more specks are visible in the group in the proper locations. Count a speck group as 0.5 point if two or three specks of the group are visible. If noise or speck-like artifacts are visible in the wrong locations in the phantom insert, subtract each speck-like artifact one for one from the last real speck counted.
• Count each mass as one point if a density difference is visible in the correct location and the full mass is visible against the background. Count each mass as 0.5 point if a density difference is visible in the correct location but the full mass is not visible, so that the mass does not have a circular appearance. If there is a mass-like artifact in the wrong location anywhere in the image, deduct the "artifactual" mass from the last "real" mass scored if the artifactual mass is equally or more apparent.
Image Quality and Radiation Dose
5.6.5 Performance Criteria and Corrective Action
The required performance criteria:
• The mean glandular dose must not exceed 3 mGy (3 mRad). The desired performance criteria:
• The mean glandular dose should not exceed 2 mGy (2mRad).
The number (total present: 6 fibers, 5 speck groups and 5 masses) of fibers, speck groups and masses that shall be identifiable are given in the table below.
Table 4 Object Score Criteria for the accreditation phantom Test
If any level is found to be beyond any action level stated, the source of the problem must be identified and the problem corrected by a Siemens customer support engineer. Consult with your MP to determine if further testing is required.
Phantom used Required
Fibers ≥ 5
Accreditation phantom Speck groups ≥ 4