Impact of resolution and noise characteristics of digital radiographic detectors on the detectability of lung nodules

Abstract

One of the unanswered questions in digital radiography is the connection between physical image quality metrics and clinical detection performance. In this paper, we examine the impact of two physical metrics, resolution and noise, on the detectability of nodules in a pulmonary background for specific digital radiographic detectors. A detection experiment was performed on a simulated image set using anatomical backgrounds from a high-quality lung radiograph and three different simulated nodule sizes ͑2-3.5 mm͒. The resolution and noise of the resulting images were modified using existing routines to simulate a selenium-based and a cesium iodide-based flat-panel detector at comparable exposures. A location-known-exactly ͑LKE͒ observer performance experiment was performed in which four experienced chest radiologists and three physicists specializing in chest radiology scored the images. The data from the observer experiment were analyzed by receiver operating characteristic ͑ROC͒ methodology. The detectability, as measured by the parameter A z , was higher for the selenium detector than the cesium iodide detector for all nodule sizes by an average of 8.5%. For one nodule size ͑2.75 mm͒, the difference between detectors was statistically significant (pϽ0.01). The findings indicate that for the particular task studied, the superior resolution performance of the selenium-based detector provided better detectability of subtle lung nodules even though the images had greater noise than images obtained with the cesium iodide detector.

Resolution and noise measurements of five CRT and LCD medical displays

“…In addition, these noise figures are not reduced to detectability indices for specific clinical tasks. 23,24 Nonetheless, physical measurements, as undertaken in this study, form a necessary first step in characterizing a display system. Our future work will include observer experiments in order to more fully understand how the resolution and noise characteristics of displays affect clinical performance.…”

The impact of breast structure on lesion detection in breast tomosynthesis

“…Twenty-five projection images spanning a 45° arc were simulated by ray tracing with W/Rh at 30 kVp. Noise and scatter were simulated and added to the projection images based on measurements done on the prototype tomosynthesis system [24][25]. A classic filtered back-projection algorithm with a cosine filter was used to reconstruct the tomosynthesis slices at 1 mm slice spacing and 340 μm in-plane resolution.…”

“…Realistic modeling of lesions and image formation are other important factors that need to be addressed. It is also evident that modeling real observers should be done as accurately as possible to accelerate VCTs by moving from signal known exactly paradigms to more complicated observer models with signal and background uncertainty, and incorporation of volumetric data as investigated in [7][8][9][10][11][12][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. The focus of this study is to characterize the effect of background tissue density and heterogeneity on the detection of irregular masses in digital breast tomosynthesis.…”

Simulation of Liver Lesions for Pediatric CT

“…Three experienced pediatric radiologists (with 1, 3, and 18 years of experience with pediatric CT) in an identical controlled lighted environment used a graphical user interface that enabled them to rate the lesions on a confidence scale from 0 (definitely simulated) to 100 (definitely real). This graphical user interface was modified from a graphical user interface for the study of breast lesions (16). The order in which the images were shown was randomized for each observer.…”