Hildebrand Dijkstra MSC, Presenter: Nothing to Disclose

Marcel Greuter PhD, Abstract Co-Author: Nothing to Disclose

Roelant Visser, Abstract Co-Author: Nothing to Disclose

Ruben van Engen, Abstract Co-Author: Nothing to Disclose

Matthys Oudkerk MD, PhD, Abstract Co-Author: Nothing to Disclose

Assessment of quality measurements on four different mammography systems based on the IEC 62220-1-2 protocol and an alternative quality protocol in terms of NPS, MTF and DQE.

Alternative method A was compared to the IEC-62220-1-2 protocol (method B). In both methods a stainless steel plate (120x60x0.8mm) was imaged on three DR mammography systems (GE Senographe Essential, Hologic Lorad Selenia and IMS Giotto) and two CR systems (Fuji FCR Profect with BD-HR screens and Kodak CR 975 with EHR-M and EHR2-M screens in combination with a GE Senographe DMR) for determination of the Modulation Transfer Function (MTF). Noise Power Spectrum (NPS) was computed on homogeneous exposed images. Anti-scatter grid and compression paddle were present in method A, however not in method B. All measurements were performed using added filtration (45mm PMMA). Using MTF and NPS the Detector Quantum Efficiency (DQE) was computed for both methods and all systems (Matlab 7.5, MathWorks). Mean detector dose in method A was 210 μGy and 60 μGy for method B.

At 1 line pairs/mm MTF for method A varied between 0.68 and 0.83, and for method B between 0.74 and 0.88 depending on the mammography system. NPS varied between 2.0e-6 and 5.4e-6 (method A), and between 2.9e-6 and 5.6e-6 mm² for method B. DQE varied between 0.07 and 0.36 (method A), and between 0.28 and 0.63 for method B. At 5 line pairs/mm MTF varied between 0.11 and 0.52 (method A), and between 0.12 and 0.51 for method B. NPS varied between 3.0e-7 and 2.2e-6 (method A), and between 4.9e-7 and 9.9e-6 mm² for method B. DQE varied between 0.01 and 0.14 (method A), and between 0.04 and 0.38 for method B. Quality ranking of the five systems in terms of DQE was dependent on the method used.  

The IEC 62220-1-2 protocol gave higher values of MTF, NPS and DQE with respect to the alternative model for line-pair frequencies. Ranking of mammography systems based on quality parameters such as DQE is dependent on the quality protocol.

Measuring MTF, NPS and DQE seems useful to characterise detector properties, however, the measurement setup needs attention.

Dijkstra, H, Greuter, M, Visser, R, van Engen, R, Oudkerk, M, Quality Parameters Measured on Four Mammography Systems: NPS, MTF, and DQE.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6008358.html