{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T13:45:21Z","timestamp":1792071921641,"version":"4.4.0"},"reference-count":42,"publisher":"Wiley","issue":"9","license":[{"start":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T00:00:00Z","timestamp":1788307200000},"content-version":"vor","delay-in-days":1,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"},{"start":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T00:00:00Z","timestamp":1788220800000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["aapm.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2026,9]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Technological developments in computed tomography (CT) have increased the diversity of acquisition and reconstruction strategies available for clinical imaging. Task\u2010based image quality metrics that account for patient\u2010size variability are needed to characterize reconstructed image performance and support protocol optimization across clinically relevant imaging conditions.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Purpose<\/jats:title>\n                    <jats:p>To propose and evaluate a novel size\u2010specific weighted detectability index (SSW\u2010d\u2019), a task\u2010based image performance metric (d') that incorporates lesion contrast weighting and water\u2010equivalent diameter variability for the characterization of CT images acquired at low dose.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      First, a multi\u2010sized image quality phantom was scanned on two CT systems: one photon\u2010counting CT (PCCT, CT1) and one CT equipped with energy integrating detectors (EICT, CT2). Acquisitions were performed with a volume CT dose index (CTDI\n                      <jats:sub>vol<\/jats:sub>\n                      ) of 3.2 mGy at 120kV without a tin filter (Sn), at Sn100 and Sn140kV. Second, acquisitions at 3.2 mGy were performed on CT1 using three reconstruction algorithms (FBP, QIR\u20102, QIR\u20104). Subsequently, five reconstruction kernels (Br32, Br44, Br56, Br68, and Br76) were evaluated at 1.1 mGy. A higher CTDI\n                      <jats:sub>vol<\/jats:sub>\n                      value of 6 mGy, combined with Br68 and QIR\u20104, was also tested. The detectability index values (d\u2019) were determined for two 10 mm diameter lesions according to two different levels of contrast, based on iodine and bone equivalent tissue. The SSW\u2010d\u2019 was calculated for each CT system and for each individual task. Then, SSW\u2010d\u2019 was expanded to include both tasks, applying contrast weights determined for each of them.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>On CT1, the highest SSW\u2010d\u2019 values were 19.3\u00a0\u00b1\u00a00.3 and 6.9\u00a0\u00b1\u00a00.0, at 120 kV for bone and iodine rods, respectively. On CT2, the highest SSW\u2010d\u2019 results were 19.0\u00a0\u00b1\u00a00.3 and 4.9\u00a0\u00b1\u00a00.0 at Sn100 kV for bone and iodine rods, respectively. The lowest values were at Sn140kV for both rods and CT systems. When encompassing both tasks, the maximum SSW\u2010d\u2019 values were 10.05\u00a0\u00b1\u00a00.04 and 8.25\u00a0\u00b1\u00a00.03, respectively obtained at 120 kV for CT1 and at Sn100 kV for CT2. The results showed that the lowest SSW\u2010d\u2019 values were at Sn140 kV for both CT systems. Comparison of acquisition and reconstruction parameters showed that the highest SSW\u2010d\u2032 value was obtained using the Br32 kernel (17.6\u00a0\u00b1\u00a00.7), approximately twofold higher than that obtained at 6 mGy (8.6\u00a0\u00b1\u00a00.3). The lowest SSW\u2010d\u2032 value (1.9\u00a0\u00b1\u00a00.1) was obtained with FBP, while the highest performance was achieved with QIR\u20104 reconstruction.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>A novel metric based on a size\u2010specific weighted detectability index (SSW\u2010d\u2019) was developed and evaluated for the characterization of reconstructed CT image performance across a range of patient\u2010equivalent diameters and clinically relevant detection tasks. The proposed SSW\u2010d\u2019 consolidates multiple detectability index measurements into a single descriptor that accounts for lesion contrast weighting and patient\u2010size variability. The metric was sensitive to acquisition and reconstruction parameters and proved useful for identifying imaging conditions that maximize task\u2010based performance in ultra\u2010low\u2010dose CT. These findings suggest that SSW\u2010d\u2019 may serve as a practical tool for image\u2010quality characterization and protocol optimization across clinically relevant imaging scenarios.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/mp.70668","type":"journal-article","created":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T08:05:21Z","timestamp":1788336321000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Size\u2010specific weighted detectability index for computed tomography image characterization"],"prefix":"10.1002","volume":"53","author":[{"given":"Isabelle","family":"Fitton","sequence":"first","affiliation":[{"name":"Department of Radiology Universit\u00e9 de Paris; Assistance Publique H\u00f4pitaux de Paris, H\u00f4pital Europ\u00e9en Georges Pompidou  Paris 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