Physical characterization of a prototype selenium-based full field digital mammography detector.
The purpose of this study was to measure experimentally the physical performance of a prototype mammographic imager based on a direct detection, flat-panel array design employing an amorphous selenium converter with 70 microm pixels. The system was characterized for two different anode types, a molybdenum target with molybdenum filtration (Mo/Mo) and a tungsten target with rhodium filtration (W/Rh), at two different energies, 28 and 35 kVp, with approximately 2 mm added aluminum filtration. To measure the resolution, the presampled modulation transfer function (MTF) was measured using an edge method. The normalized noise power spectrum (NNPS) was measured by two-dimensional Fourier analysis of uniformly exposed mammograms. The detective quantum efficiencies (DQEs) were computed from the MTFs, the NNPSs, and theoretical ideal signal to noise ratios. The MTF was found to be close to its ideal limit and reached 0.2 at 11.8 mm(-1) and 0.1 at 14.1 mm(-1) for images acquired at an RQA-M2 technique (Mo/Mo anode, 28 kVp, 2 mm Al). Using a tungsten technique (MW2; W/Rh anode, 28 kVp, 2 mm Al), the MTF went to 0.2 at 11.2 mm(-1) and to 0.1 at 13.3 mm(-1). The DQE reached a maximum value of 54% at 1.35 mm(-1) for the RQA-M2 technique at 1.6 microC/kg and achieved a peak value of 64% at 1.75 mm(-1) for the tungsten technique (MW2) at 1.9 microC/kg. Nevertheless, the DQE showed strong exposure and frequency dependencies. The results indicated that the detector offered high MTFs and DQEs, but structured noise effects may require improved calibration before clinical implementation.
Saunders
Robert S
RS
Duke Advanced Imaging Laboratories, Departments of Physics and Radiology, Duke University, Durham, North Carolina 27710, USA.
Samei
Ehsan
E
Jesneck
Jonathan L
JL
Lo
Joseph Y
JY
D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D008327:Mammography / Q000295:instrumentation*; D019047:Phantoms, Imaging; D010865:Pilot Projects; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D012643:Selenium / Q000737:chemistry* / Q000528:radiation effects*; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D014159:Transducers; D014963:X-Ray Intensifying Screens
D012643:Selenium