[Show abstract][Hide abstract] ABSTRACT: In mammography units, the X-ray tube focal spot is located directly above the chest wall edge of the detector. Therefore, the X-ray beam is incident at a different angle along the cathode-anode axis. When the X-ray beam is incident on the imaging plate (IP) at a relatively large angle, the resolution property of a new imaging plate with dual-sided reading system would be degraded compared with the conventional imaging plate because of the parallax effect, which produces a shift in the image on two sides of the imaging plate. To evaluate the oblique incidence effect of the X-ray beam on the degradation of resolution properties and detection of simulated microcalcifications of a new CR system with a pixel size of 50 microm, its basic imaging properties and observer performance tests were compared with those of a conventional CR system. The resolution properties were evaluated by measuring modulation transfer functions (MTFs). Observer performance tests were conducted to compare the detectability of simulated microcalcifications of CR systems. Degradation of presampling MTFs for the new system is greater than that of the conventional CR system when the X-ray beam was incident at the same angle on the imaging plate. We found that the degradation of the area under the ROC curve (Az) for the new CR system was greater than that of the conventional CR system when the X-ray beam was incident at the same angle on the imaging plate.
[Show abstract][Hide abstract] ABSTRACT: To investigate the physical imaging properties and detection of simulated microcalcifications of a new computed radiography (CR) system with a pixel size of 50 microm for digital mammography.
New and conventional CR were employed in this study. The new CR system included a high-resolution imaging plate coupled with the FCR5000MA (50 microm pixel pitch) including transparent support and a dual-sided reader. The conventional CR system was coupled with the FCR9000 (100 microm pixel pitch). Modulation transfer functions (MTFs) and Wiener spectra (WS) of the new and conventional CR systems were measured. Observer performance tests were conducted to compare the effects of pixel size (50 microm vs. 100 microm) on the diagnostic accuracy of CR systems in the detection of simulated microcalcifications.
The presampling MTF of the new CR system was higher at high frequencies than the conventional CR system. The WS of the new CR system was comparable to that of the conventional CR system at all frequencies. The area under the receiver operating characteristic (ROC) curve (Az) obtained with the new CR and the conventional CR systems were 0.84 and 0.79, respectively. Results showed that the detection of simulated clustered microcalcifications was significantly improved by use of the new CR system compared with the conventional CR system (p<0.05).
The new CR mammography system improved physical imaging properties and detection of simulated microcalcifications over conventional CR mammography.
No preview · Article · Jul 2004 · Radiation Medicine