Tube voltage in chest and abdomen DR imaging: Which settings return maximal non‐prewhitening model observer with eye filter (NPWE) detectability?

• Published in: Medical physics (Lancaster) 2025-01, Vol.52 (1), p.146-157
• Main Authors: Moore, Craig S., Wood, Tim J., Saunderson, John R., Beavis, Andrew W.
• Format: Article
• Language: English
• Subjects: model observer; optimization; x‐ray imaging
• ISSN: 0094-2405; 2473-4209; 2473-4209
• DOI: 10.1002/mp.17477

Background The non‐prewhitening computational model observer with eye filter (NPWE) has been shown to reasonably predict human observer performance in general radiography and is an appropriate substitute when real clinical trials are not feasible. In this study, the NPWE model observer is used to detect specific tasks (circular designer nodules) ranging between 1 and 30 mm in diameter using chest and abdomen phantom images acquired across the diagnostic energy range (60–125 kVp) with and without an anti‐scatter grid. Purpose The aim of this study was to derive tube voltage (kVp) settings that return maximal NPWE detectability (d’) of designer nodules, for digital radiography (DR) chest and abdomen imaging. Methods Images of a chest phantom (LucAl phantom) and a surrogate for an abdomen (18.5 cm PMMA) were acquired across the diagnostic energy range (60–125 kVp) with matched effective dose (for the respective anatomies), with and without an anti‐scatter grid, on a general x‐ray system. Images were captured using an Agfa DX‐D 40C wireless indirect caesium iodide (CsI) imaging panel. Modulation transfer function (MTF), normalized noise power spectrum (NNPS), and contrast (C) were measured in each image and the detectability index d’ was calculated for circular designer nodules with diameters ranging from 1 to 30 mm (in steps of 1 mm). Results The calculated d’ peaked at a nodule diameter of 3 mm irrespective of tube voltage, for both chest and abdomen images. A tube voltage of 80 kVp returned maximal d’ for chest imaging across all nodule diameters both with and without an anti‐scatter grid. A tube voltage of 70 kVp returned maximal d’ for abdomen imaging. Conclusion The NPWE observer model has been used to derive tube voltages (kVp) that return maximal detectability (d’) of designer nodules for chest and abdomen radiography using a modern DR imaging system. This will provide the medical physicist with a starting point in the task of optimising tube voltage range for chest and abdomen imaging.