Quality Assurance Mammography Phantom according to European guidelines
When screening large populations for breast cancer, there are two conflicting demands; on one hand the radiation dose must be as low as possible and on the other hand no tumors may be left undetected. To fulfill both demands the equipment you use has to operate as close to the physical limits as technically possible. Therefore quality measurement, and above all quality assurance, is of the utmost importance. This phantom is really state of the art and a “must” for every breast cancer center.
The QAMAM phantom consists of a perspex (PMMA) block, which contains embedded test objects for the measurement of radiation quality, low contrast resolution and spatial resolution. All test pieces are embedded in such a way that over the whole phantom an equivalent PMMA
thickness of 45 mm is obtained. The positioning of the test elements leaves large areas to evaluate the homogeneity of the X-rays.
- For the measurement of spatial resolution there are 2 perpendicular test patterns, so the resolution parallel and perpendicular to the anode-cathode axis can be measured at the same time. The spacing between the lines of both test patterns varies continuously from 6 to 20 lines per millimeter.
- A pure aluminum step wedge with linear increasing thickness can be used to evaluate both qualitative and quantitative the contrast resolution over the whole dynamic range.
- We used a special low contrast element, made of a pure aluminum base plate with ten gold discs with logarithmically increasing thickness. The gold discs are created using the same special and unique procedure as used for the production of the CDMAM phantom.
- A metal strip at one side of the phantom shields X-rays, leaving the use for a light sensitometer.
- There are several engraved markers with lead inlet and a ridge at the breast side for position referencing.
- 2 rows of 5 steel balls each are used for testing the limitation of the image at the chest wall side.
1) Body made of PMMA:
Dimensions 240 * 185 mm
Thickness 45 mm
2) Step wedge made of Aluminum (96%)
10 steps each 10 * 10 mm
thickness 0.75…3.00 mm
(increments 0.25 mm)
3) Resolution Test Patterns 30 µm Lead:
30 * 30 * 1 mm
4) Low Contrast Pattern:
Base aluminum (99.5%)
10 gold discs
thickness 25 .. 200nm in logarithmic steps
diameter 5.0 mm
5) Location and information Patterns:
engraved with lead inlet, half a circle at breast side (100 mm)
circle in the center
6) Steel balls:
2 rows of 5 balls, diameter 2 mm each
The QAMAM phantom is initiated from the project: “Quality Assurance in Mammography, Department of Diagnostic Radiology, Radboud University Nijmegen Medical Center, the Netherlands, of M.A.O. Thijssen, K.R. Bijkerk, and J.M. Lindeyer.