{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T03:02:04Z","timestamp":1789700524939,"version":"4.0.1"},"reference-count":25,"publisher":"Wiley","issue":"9","license":[{"start":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T00:00:00Z","timestamp":1787875200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T00:00:00Z","timestamp":1787875200000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"funder":[{"DOI":"10.13039\/100005625","name":"RSNA Research and Education Foundation","doi-asserted-by":"publisher","award":["RSCH2302"],"award-info":[{"award-number":["RSCH2302"]}],"id":[{"id":"10.13039\/100005625","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["aapm.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["J Applied Clin Med Phys"],"published-print":{"date-parts":[[2026,9]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Ultra\u2010high\u2010resolution (UHR) photon\u2010counting CT (PCCT) with small\u2010pixel detectors improves resolution and noise, but its dependence on diverse imaging conditions remains insufficiently characterized.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Purpose<\/jats:title>\n                    <jats:p>To systematically evaluate the small\u2010pixel effect in UHR PCCT by assessing noise properties and high\u2010contrast spatial resolution under varying acquisition and reconstruction conditions.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Images of an ACR CT accreditation phantom with a body ring simulating a medium\u2010sized patient were acquired on a clinical PCCT system (NAEOTOM Alpha.Peak, Siemens Healthineers, Germany) using standard\u2010resolution (STD) and UHR modes. Scans were performed at dose levels ranging from 3 to 24 mGy. Reconstructions included slice thicknesses from 0.2\/0.4 to 3.0\u00a0mm, convolution kernels from Br36 to Br72, quantum iterative reconstruction both off and at strength levels 1\u20134, matrix sizes of 512 to 1024, and field\u2010of\u2010view (FOV) settings from 210 to 350\u00a0mm. Both low\u2010energy threshold (T3D) and virtual monoenergetic images were evaluated. Image noise was quantified using noise magnitude, noise power spectrum (NPS), and average spatial frequency. High\u2010contrast spatial resolution was evaluated using the modulation transfer function and visual assessment of resolution patterns.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Compared with the STD mode, the UHR mode consistently reduced image noise, with the greatest reductions observed at thinner slice thicknesses and with sharper kernels. In contrast, dose level, QIR strength, matrix size, and spectral image type had minimal influence on the relative noise differences between the two modes. NPS analysis further demonstrated lower noise magnitude and, depending on the imaging conditions, a shift of the noise spectrum toward lower spatial frequencies, indicating relative suppression of high\u2010frequency noise in the UHR mode. High\u2010contrast spatial resolution was more strongly influenced by imaging sampling conditions, particularly matrix size and FOV, and remained overall comparable between the STD and UHR modes.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>The UHR mode of PCCT consistently achieves lower image noise than the STD mode without compromising high\u2010contrast spatial resolution. Its greatest benefit is observed in high\u2010spatial\u2010resolution imaging protocols employing thin slice thicknesses and sharp reconstruction kernels, whereas the incremental benefit is limited for routine CT imaging. These findings support a task\u2010based implementation of the UHR mode to optimize protocol selection according to clinical imaging requirements.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/acm2.70776","type":"journal-article","created":{"date-parts":[[2026,8,29]],"date-time":"2026-08-29T04:45:37Z","timestamp":1787978737000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Phantom evaluation of small\u2010pixel effect in ultra\u2010high\u2010resolution photon\u2010counting CT: Noise texture and high\u2010contrast spatial resolution"],"prefix":"10.1002","volume":"27","author":[{"given":"Kyu\u2010Ho","family":"Song","sequence":"first","affiliation":[{"name":"Department of Radiology UT Southwestern Medical Center  Dallas Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Colin","family":"Shan","sequence":"additional","affiliation":[{"name":"Department of Radiology UT Southwestern 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