The impact of greyscale inversion for nodule detection in an anthropomorphic chest phantom: a free-response observer study

Abstract

Objective:The aim of this work was to assess the impact of greyscale inversion on nodule detection on posteroanterior chest X-ray images. Previous work has attempted this, with no consensus opinion formed. We assessed the value of “fast-flicking” between standard and inverted display modes for nodule detection.Methods:Six consultant radiologists (with 5–32 years' reporting experience) completed an observer task under the free-response paradigm. An anthropomorphic chest phantom was loaded with 50 different configurations of simulated nodules (1–4 nodules per case) measuring 5, 8, 10 and 12 mm in spherical diameter; each configuration represented a single case. In addition, 25 cases contained no nodules. Images were displayed in three modes: (i) standard, (ii) inverted and (iii) fast-flicking between standard and inverted display modes. Each observer completed the study in a different order of display (i, ii, iii) using a calibrated 5-megapixel monitor. Nodules were localized with mouse clicks and ratings assigned using a 1–10 discrete slider-bar confidence scale. Rjafroc (Pittsburgh, PA) was used for data analysis; differences in nodule detection performance were considered significant at 0.05.Results:The observer-averaged weighted jackknife alternative free-response receiver-operating characteristic figures of merit were 0.715 (standard), 0.684 (inverted) and 0.717 (fast-flicking). Random-reader fixed-case analysis revealed no statistically significant difference between any treatment pair [F(2,8) = 1.22; p = 0.345].Conclusion:No statistically significant difference in nodule detection was found for the three display conditions.Advances in knowledge:We have investigated the impact of fast-flicking between standard and inverted display modes for the detection of nodules. We found no benefit.

The diagnostic value of grey-scale inversion technique in chest radiography

“…Thompson et al reported that two display modes can improve nodule detection [ 26 ]. These authors hypothesized that the advantage of using two display modes might lie in the fast-flicking between the two images, namely standard and inverted, which would draw attention to suspicious areas, (e.g.…”

“…This fast-flicking technique was not employed by our readers, for whom the detection was already slightly improved, suggesting that it might only partly explain the advantages of such a combination. Even if limited in number, the majority of studies that have applied the grey-scale inversion display mode to chest radiography have attempted to demonstrate its additional value in detecting lung nodules, either real or simulated, with opposite results [ 17 , 22 – 26 ]. Nodules were fairly represented in our sample (16.8%, 85 cases), and significant differences were not observed in accuracy or interobserver agreement with the combination of the two techniques.…”

“…Based on the evidence that viewing the inverted image (black on white) improves human contrast perception [16], grey-scale inversion has been proposed as a valid supplementary tool to increase the diagnostic accuracy of radiographic imaging [17][18][19][20][21]. In chest radiography, the diagnostic value of inverted images has been investigated mostly for parenchymal nodules [17,[22][23][24][25][26], pneumothorax [20] and rib fractures [27] detection. The clinical advantages of using this display method, however, are still debated, and no general consensus has been reached.…”

Evidence-Based Survey Design: The Use of Continuous Rating Scales in Surveys

“…Although sliders are often used as continuous rating scales, they can be designed to function as discrete rating scales (e.g., 10‐ or 11‐point scales), similar to discrete NRSs, by making the marker snap to grid between grid lines (e.g., Thompson, Thomas, Manning, & Hogg, ). Alternatively, when sliders are set to capture input within a 0‐to‐100 range without decimal points , it is unclear whether they are a true continuous rating scale or a 101‐point discrete rating scale.…”