Two K versus 4 K storage phosphor chest radiography: detection performance and image quality

Abstract

The purpose of this study was to evaluate the effect of matrix size (4-K versus 2-K) in digital storage phosphor chest radiographs on image quality and on the detection of CT-proven thoracic abnormalities. In 85 patients who underwent a CT of the thorax, we obtained two additional posteroanterior storage phosphor chest radiographs, one with a matrix size of 3,520x4,280 (=4-K) and the other with a matrix size of 1,760x2,140 (=2-K). Acquisition, processing and presentation parameters were identical for all radiographs. Two radiologists evaluated the presence of mediastinal, pleural, and pulmonary abnormalities on hard copies of the radiographs, applying ROC analysis. In addition, four radiologists were asked to subjectively rank differences in image quality and to assess the demarcation of anatomic landmarks comparing the images in a blinded side-by-side manner. These data were analyzed using a two-sided binomial test with a significance level of P<0.05. Both tests, the ROC analysis of the detection performance and the binomial test of the subjective quality ratings, did not reveal significant differences between the two matrix sizes. Compared to 2-K radiographs, 4-K storage phosphor chest radiographs do not provide superior detection performance or image quality when evaluated in identical hard copy formats.

Digital chest radiography: an update on modern technology, dose containment and control of image quality

“…These experimental data explain that a number of clinical studies could not find an advantage of 4k matrices for detection of a broad range of intrapulmonary lesions [ 12 , 13 ], delineation of anatomical landmarks [ 13 ] or interstitial diseases [ 14 ].…”

Seven general radiography x-ray detectors with pixel sizes ranging from 175 to 76 μm: technical evaluation with the focus on orthopaedic imaging

“…Giger and Doi (1987) calculated signal-to-noise (SNR) based on signal detection theory, and found that 200 μm pixel is adequate for detail detection in most digital radiography examinations. Following the introduction of CR devices, it was found that switching from 200 to 100 μm pixels did not improve performance for the detection of intrapulmonary lesions (Koelblinger et al 2007). This was attributed to the poor modulation transfer function (MTF) and detective quantum efficiency (DQE) of the CR powder phosphor plates at spatial frequencies above 2.5 mm −1 Flynn 2002, Schaefer-Prokop et al 2008).…”