{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T07:13:12Z","timestamp":1789456392367,"version":"build-2803163510"},"reference-count":46,"publisher":"IOP Publishing","issue":"17","license":[{"start":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T00:00:00Z","timestamp":1789430400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T00:00:00Z","timestamp":1789430400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/iopscience.iop.org\/info\/page\/text-and-data-mining"},{"start":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T00:00:00Z","timestamp":1789430400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/publishingsupport.iopscience.iop.org\/questions\/alternative-author-rights-policies\/"},{"start":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T00:00:00Z","timestamp":1789430400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/publishingsupport.iopscience.iop.org\/questions\/alternative-author-rights-policies\/"}],"funder":[{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"crossref","award":["372393016"],"award-info":[{"award-number":["372393016"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["iopscience.iop.org"],"crossmark-restriction":false},"short-container-title":["Phys. Med. Biol."],"published-print":{"date-parts":[[2026,9,15]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    <jats:italic>Objective.<\/jats:italic>\n                    Range uncertainties in proton therapy largely arise from the semi-empirical conversion of x-ray computed tomography (CT) Hounsfield Units to stopping power relative to water (RSP), requiring generous safety margins or robust optimization. Pencil beam-wise integrated depth-dose profiles (IDDs), obtained via proton transmission imaging using a particle integrating detector, can be combined with the treatment planning CT to obtain patient-specific conversion curves. Existing calibration approaches rely on projection images or water-equivalent path length (WEPL) histograms derived from IDDs via signal decomposition or deconvolution. A direct optimization approach based on the acquired IDD signal is proposed, avoiding the need for decomposition or deconvolution and their associated WEPL accuracy and resolution limitations.\n                    <jats:italic>Approach.<\/jats:italic>\n                    The RSP conversion curve is iteratively optimized using Monte Carlo-simulated IDDs acquired from two orthogonal projection angles in a line-scan proton imaging setup. The differentiable implementation of the forward projection operator is embedded in a gradient-based optimization scheme.\n                    <jats:italic>Main results.<\/jats:italic>\n                    The proposed IDD-based optimization approach significantly reduces the calibration error compared to the initial guess. The median mean absolute percentage error on a set of axial CT slices decreases from 1.88% to 0.58%, with a median computation time of 5.47 h per slice. The optimized calibration improves dose accuracy for an exemplary treatment pencil beam. Increasing the spot spacing by a factor of ten decreases the computation time to 0.60 h with minimal loss of accuracy. Using a single projection angle yields comparable results to using both projections (0.64% vs 0.57%). With current detector depth resolutions of\n                    <jats:inline-formula>\n                      <jats:tex-math>\n                        \n                      <\/jats:tex-math>\n                      <mml:math xmlns:mml=\"http:\/\/www.w3.org\/1998\/Math\/MathML\" overflow=\"scroll\">\n                        <mml:mrow>\n                          <mml:mo>\u223c<\/mml:mo>\n                        <\/mml:mrow>\n                      <\/mml:math>\n                    <\/jats:inline-formula>\n                    2 mm, calibration accuracy of\n                    <jats:inline-formula>\n                      <jats:tex-math>\n                        \n                      <\/jats:tex-math>\n                      <mml:math xmlns:mml=\"http:\/\/www.w3.org\/1998\/Math\/MathML\" overflow=\"scroll\">\n                        <mml:mrow>\n                          <mml:mo>\u223c<\/mml:mo>\n                        <\/mml:mrow>\n                      <\/mml:math>\n                    <\/jats:inline-formula>\n                    0.7% is achievable, with potential improvements using finer-resolution detectors.\n                    <jats:italic>Significance.<\/jats:italic>\n                    Particle integrating detectors offer potential for clinical translation due to lower cost and complexity. Direct optimization on IDDs using a differentiable forward operator enables accurate, fully automated calibration, improving upon earlier manual IDD-based or automated WEPL-based approaches.\n                  <\/jats:p>","DOI":"10.1088\/1361-6560\/ae9fb0","type":"journal-article","created":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T22:53:56Z","timestamp":1787871236000},"page":"175041","update-policy":"https:\/\/doi.org\/10.1088\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Patient-specific stopping power calibration of treatment planning x-ray CT using integrated depth-dose profiles acquired by proton transmission imaging\u2014a feasibility study"],"prefix":"10.1088","volume":"71","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6429-5627","authenticated-orcid":true,"given":"Ines","family":"Butz","sequence":"first","affiliation":[{"name":"Ludwig-Maximilians-University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7779-6690","authenticated-orcid":true,"given":"Katia","family":"Parodi","sequence":"additional","affiliation":[{"name":"Ludwig-Maximilians-University"},{"name":"Partner Site Munich"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0106-7448","authenticated-orcid":true,"given":"Chiara","family":"Gianoli","sequence":"additional","affiliation":[{"name":"Ludwig-Maximilians-University"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"266","published-online":{"date-parts":[[2026,9,15]]},"reference":[{"key":"pmbae9fb0bib1","doi-asserted-by":"publisher","DOI":"10.1088\/1361-6560\/ad7cbd","type":"journal-article","article-title":"First clinical implementation of a highly efficient daily online adapted proton therapy (DAPT) workflow","volume":"69","author":"Albertini","year":"2024","journal-title":"Phys. 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