Congress:
EuroSafe Imaging 2019
Keywords:
Action 5 - Performance indicators for radiation protection management, Radiation physics, Mammography, Physics, Quality assurance
Authors:
L. Marti-Bonmati, J. Chimeno, P. Gras, M. Sabater, N. Lopez, J. M. Campayo, J. I. Villaescusa
DOI:
10.26044/esi2019/ESI-0054
Description of activity and work performed
MATERIAL AND METHODS:
8 mammography systems were analyzed during 2016 y 2017: Giotto I3DL (3units),
Fujifilm Amulet FDR (3 units) and Hologic Selenia (2 units).
According to the Spanish protocol of quality assurance in radiodiagnostic (PECCRD)(1) ,
the image quality is evaluated with 6 different tests.
In this study we focus on the following tests since we consider them relievable to assess image quality and dosimetry:
-Image quality: Contrast thickness threshold The phantom CDMAM 3.4 was used in this test.
This phantom contains gold discs of different thicknesses (0.03 μm – 2 μm) and diameters (0.1 mm – 2 mm).
The phantom was placed within 4 cm of PMMA.
Thus,
the hall phantom was equivalent to 5 cm of PMMA or 6 cm of breast tissue.
The image quality was assess as the minimum gold thickness detectable for each diameter.
-Dosimetry: Mean glandular dose The mean glandular dose was estimated following the Dance methodology (2).
The air-kerma at the entrance surface was measured with Black Piranha (RTI) detector.
The absorbed dose was estimated for 2 cm ,
4.5 cm,
5 cm and 6 cm of PMMA.
All acquisitions were Full Field Digital Mammography and were obtained using AEC (clinical conditions).
The jointly assessment of image quality and dosimetry was carried out by the figure of merit:
α = IQF · DG / (IQFal · DG_al)
IQF≡Σi di·μi , di is the diameter of gold discs of CDMAM and μi is the contrast thickness threshold detected.
DG≡ Mean glandular dose for a certain tissue thickness
DG_al≡ Mean glandular dose achievable for a certain tissue thickness.
IQFal≡ Achievable value of IQF.
Both achievable values could be calculated from Table 1 and Table 2.(3)
According to this figure of merit,
systems with lower value are better rated.
We only evaluate the impact of the figure of merit while using phantom equivalent to 5 cm of PMMA.