Pulmonary nodule detection with digital projection radiography: an ex-vivo study on increased latitude post-processing

Abstract

To evaluate increased image latitude post-processing of digital projection radiograms for the detection of pulmonary nodules. 20 porcine lungs were inflated inside a chest phantom, prepared with 280 solid nodules of 4-8 mm in diameter and examined with direct radiography (3.0x2.5 k detector, 125 kVp, 4 mAs). Nodule position and size were documented by CT controls and dissection. Four intact lungs served as negative controls. Image post-processing included standard tone scales and increased latitude with detail contrast enhancement (log-factors 1.0, 1.5 and 2.0). 1280 sub-images (512x512 pixel) were centred on nodules or controls, behind the diaphragm and over free parenchyma, randomized and presented to six readers. Confidence in the decision was recorded with a scale of 0-100%. Sensitivity and specificity for nodules behind the diaphragm were 0.87/0.97 at standard tone scale and 0.92/0.92 with increased latitude (log factor 2.0). The fraction of "not diagnostic" readings was reduced (from 208/1920 to 52/1920). As an indicator of increased detection confidence, the median of the ratings behind the diaphragm approached 100 and 0, respectively, and the inter-quartile width decreased (controls: p<0.001, nodules: p=0.239) at higher image latitude. Above the diaphragm, accuracy and detection confidence remained unchanged. Here, the sensitivity for nodules was 0.94 with a specificity from 0.96 to 0.97 (all p>0.05). Increased latitude post-processing has minimal effects on the overall accuracy, but improves the detection confidence for sub-centimeter nodules in the posterior recesses of the lung.

CsI-detector-based dual-exposure dual energy in chest radiography for lung nodule detection: results of an international multicenter trial

“…Even though our total results do not suggest that a modified study design discriminating obscured and non-obscured nodules would prove DE superiority, further studies in this regard could render opposing results. It also remains unclear if additional image post processing might have a positive impact [24].…”

Detection of Artificial Air Space Opacities with Digital Radiography: Ex Vivo Study on Enhanced Latitude Post-Processing

“…A larger fraction of the potentially useful diagnostic information is presented without the need for image manipulation by the radiologist. For a detailed description of the technique, refer to [8,12]. In this study, renderings of each image were prepared with the default automated tone scale algorithm as well as with five levels of latitude enhancement having EVP gain values (α-1) from 1.0 to 3.0 in increments of 0.5.…”

“…When used for in-department chest radiography, it was assumed to provide slight advantages in the evaluation of disease in the mediastinum [9,11]. For the EVP algorithm, this was already shown with ex vivo experiments using artificial pulmonary nodules, but the effects on the detection of subtle opacifications have not yet been studied [12]. An advantage of EVP over other techniques is that it is separately effective on high and low frequency components of the full scale raw image [12].…”

“…For the EVP algorithm, this was already shown with ex vivo experiments using artificial pulmonary nodules, but the effects on the detection of subtle opacifications have not yet been studied [12]. An advantage of EVP over other techniques is that it is separately effective on high and low frequency components of the full scale raw image [12]. This makes the difference to simply applying a larger window width to all image components.…”

“…Hence, different post-processing techniques to widen the dynamic range of digital images have been developed [8 -11]. EVP (enhanced visualization processing, Carestream Health, Inc., Rochester, NY, USA) as one example, separately reduces the contrast of the low image frequencies, thereby increasing the latitude [8,12]. Simultaneously, the high frequencies are enhanced to preserve detail contrast.…”