Room: Track 1
Purpose: The noise-response (NR) method is an approach used to measure the detector modulation transfer function (MTF) from flat-field images, from which the noise power spectrum (NPS) and detective quantum efficiency (DQE) can also be calculated. This study investigated the feasibility of incorporating the NR method into routine quality control (QC) to evaluate digital image receptor performance for radiography and fluoroscopy in the clinical environment and compared this method to the more common edge spread function method.
Methods: Flat-field images were acquired using the AAPM TG-116–recommended beam quality at various detector dose levels based on the exposure index from radiography equipment and the target detector dose from fluoroscopy equipment. Flat-field for-processing images were analyzed by MATLAB software using the NR method to calculate the MTF and NPS, from which the DQE was derived. For comparison purposes, for-processing images of a high-contrast sharp edge were used to calculate the MTF using the IEC 62220-1 standard methodology, which is based on the edge spread function.
Results: The two methods of determining MTF yielded comparable results; however, the NR method was simpler to perform since it required only flat-field images. Analysis of flat-field images using the
NR method also allowed for calculation of the NPS and DQE, which are potentially useful QC metrics.
Conclusion: The NR method allows for the determination of image receptor MTF, NPS, and DQE in the clinical setting using only flat-field images. Because the NR method circumvents the complications of using an edge and the results with this method are comparable to those obtained with the IEC 62220-1 method, the NR method may be better suited for routine QC of detector performance in the clinical setting.