{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,20]],"date-time":"2026-10-20T16:30:55Z","timestamp":1792513855243,"version":"4.5.0"},"reference-count":31,"publisher":"Wiley","issue":"11","license":[{"start":{"date-parts":[[2023,8,21]],"date-time":"2023-08-21T00:00:00Z","timestamp":1692576000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["R01EB001838"],"award-info":[{"award-number":["R01EB001838"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["R01HL155293"],"award-info":[{"award-number":["R01HL155293"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["P41EB028744"],"award-info":[{"award-number":["P41EB028744"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["aapm.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2023,11]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Background<\/jats:title><jats:p>High tube current generates a high flux of x\u2010rays to photon counting detectors (PCDs) that can potentially result in the piling up of pulses formed by concurrent photons, which can cause count loss and energy resolution degradation.<\/jats:p><\/jats:sec><jats:sec><jats:title>Purpose<\/jats:title><jats:p>To evaluate the performance of clinical photon\u2010counting CT (PCCT) systems in high flux, potentially influenced by pulse pileup effects, in terms of task\u2010generic image quality metrics.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>A clinical phantom was scanned on a commercial PCCT scanner (NAEOTOM Alpha, Siemens) at 120\u00a0kV under fourteen different tube current levels (40\u20131000\u00a0mA) with a rotation time of 0.25 s and a pitch of 1. The dose levels corresponded to CTDI<jats:sub>vol<\/jats:sub>(32\u00a0cm phantom) of 0.79\u201319.8\u00a0mGy. CT sinograms were reconstructed using QIR\u2010off mode (noniterative reconstruction algorithm), Br44 kernel, and a voxel size of . imQuest, an open\u2010source MATLAB\u2010based software package was used to calculate noise power spectrum (NPS), task transfer function (TTF), contrast\u2010to\u2010noise ratio (CNR), and CT number according to AAPM Task Group 233 metrology.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The 50% cut\u2010off frequency of TTF (f<jats:sub>50<\/jats:sub>) remained mostly constant across all higher tube currents for all inserts, namely polyethylene, bone, air, and acrylic. Using the lowest two data points (40 and 80\u00a0mA), the expected relationship between noise magnitude and tube current was determined to be noise mA<jats:sup>\u22120.47<\/jats:sup>. The measured noise magnitude were up to 11.1% higher than the expected value at the highest tube current. The average frequency of NPS (<jats:italic>f<\/jats:italic><jats:sub>av<\/jats:sub>) decreased from 0.32 to 0.29\u00a0mm<jats:sup>\u22121<\/jats:sup>as tube current increased from 40 to 1000\u00a0mA. No considerable effects were observed in CT number measurement of any insert; however, CT numbers for air and bone changed almost monotonically as tube current increased. Absolute CNR increased monotonically for all inserts; however, the difference between measured and expected CNRs were approximately \u22126% to 12% across all tube currents.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>Increasing tube currents did not affect the spatial resolution, but slightly affected the CT number and noise measurements of the clinical PCCT system. However, the effects were only considerable at clinically irrelevant tube currents used on a small 20\u2010cm phantom. In general clinical practices, automatic exposure control techniques are used to decrease the variation of flux on the detector, which alleviates the chances of detector saturation due to high count rates. The observed effects could be due to pulse pileup, signal\u2010dependent filtration of the system, or nonlinearities in the reconstruction algorithm. In conclusion, either the deadtime of the detector used in the photon\u2010counting CT system is shorter such that count losses due to pulse pileup are negligible, or pulse pileup has inconsiderable effects on the image quality of clinical photon\u2010counting CT systems in routine clinical practice due to possible corrections applied on the system.<\/jats:p><\/jats:sec>","DOI":"10.1002\/mp.16671","type":"journal-article","created":{"date-parts":[[2023,8,22]],"date-time":"2023-08-22T02:55:07Z","timestamp":1692672907000},"page":"6693-6703","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Exploration of the pulse pileup effects in a clinical CdTe\u2010based photon\u2010counting computed tomography"],"prefix":"10.1002","volume":"50","author":[{"given":"Mridul","family":"Bhattarai","sequence":"first","affiliation":[{"name":"Medical Physics Graduate Program Duke University Durham North Carolina USA"},{"name":"Center for Virtual Imaging Trials (CVIT) Duke University Durham North Carolina USA"},{"name":"Department of Radiology \u2013 School of Medicine Duke University Durham North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Steve","family":"Bache","sequence":"additional","affiliation":[{"name":"Clinical Imaging Physics Group \u2013 Duke University Health System Durham North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ehsan","family":"Abadi","sequence":"additional","affiliation":[{"name":"Medical Physics Graduate Program Duke University Durham North Carolina USA"},{"name":"Center for Virtual Imaging Trials (CVIT) Duke University Durham North Carolina USA"},{"name":"Department of Radiology \u2013 School of Medicine Duke University Durham North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ehsan","family":"Samei","sequence":"additional","affiliation":[{"name":"Medical Physics Graduate Program Duke University Durham North Carolina USA"},{"name":"Center for Virtual Imaging Trials (CVIT) Duke University Durham North Carolina USA"},{"name":"Department of Radiology \u2013 School of Medicine Duke University Durham North Carolina USA"},{"name":"Clinical Imaging Physics Group \u2013 Duke University Health System Durham North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2023,8,21]]},"reference":[{"key":"e_1_2_8_2_1","doi-asserted-by":"publisher","DOI":"10.1088\/1361\u20106560\/abc5a5"},{"key":"e_1_2_8_3_1","doi-asserted-by":"publisher","DOI":"10.1148\/radiol.2018172656"},{"key":"e_1_2_8_4_1","doi-asserted-by":"publisher","DOI":"10.1002\/mp.15112"},{"key":"e_1_2_8_5_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.nima.2018.05.027"},{"key":"e_1_2_8_6_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4954008"},{"key":"e_1_2_8_7_1","doi-asserted-by":"publisher","DOI":"10.1002\/mp.12799"},{"key":"e_1_2_8_8_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3429056"},{"key":"e_1_2_8_9_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3539602"},{"key":"e_1_2_8_10_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3592932"},{"key":"e_1_2_8_11_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4941743"},{"key":"e_1_2_8_12_1","doi-asserted-by":"publisher","DOI":"10.1088\/0031\u20109155\/61\/4\/1572"},{"key":"e_1_2_8_13_1","doi-asserted-by":"crossref","unstructured":"BarberW NygardE WesselJ et\u00a0al.Optimizing CdTe detectors and ASIC readouts for high\u2010flux x\u2010ray imaging. vol 8143. 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