{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,27]],"date-time":"2026-07-27T08:03:57Z","timestamp":1785139437605,"version":"3.55.0"},"reference-count":31,"publisher":"IOP Publishing","issue":"14","license":[{"start":{"date-parts":[[2026,7,27]],"date-time":"2026-07-27T00:00:00Z","timestamp":1785110400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,7,27]],"date-time":"2026-07-27T00:00:00Z","timestamp":1785110400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/iopscience.iop.org\/info\/page\/text-and-data-mining"}],"funder":[{"name":"Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates","award":["8474000748"],"award-info":[{"award-number":["8474000748"]}]}],"content-domain":{"domain":["iopscience.iop.org"],"crossmark-restriction":false},"short-container-title":["Phys. Med. Biol."],"published-print":{"date-parts":[[2026,7,28]]},"abstract":"Abstract<\/jats:title>\n \n Objective.<\/jats:italic>\n To develop and evaluate a scanner-specific power law method for voxelwise effective atomic number (\n \n \n \n <\/jats:tex-math>\n \n \n \n Z<\/mml:mi>\n \n \n eff<\/mml:mi>\n <\/mml:mrow>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n ) and electron density (\n \n \n \n <\/jats:tex-math>\n \n \n \n \u03c1<\/mml:mi>\n \n e<\/mml:mi>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n ) imaging on a commercial spectral photon-counting CT (SPCCT) system, and to demonstrate its applicability to tissue characterization in heterogeneous samples.\n Approach.<\/jats:italic>\n The x-ray linear attenuation coefficient\n \n \n \n <\/jats:tex-math>\n \n \n \u03bc<\/mml:mi>\n (<\/mml:mo>\n E<\/mml:mi>\n )<\/mml:mo>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n was modeled as a power law sum of photoelectric, Compton and empirical correction terms. Model coefficients were fitted to NIST cross sections for\n \n \n \n <\/jats:tex-math>\n \n \n Z<\/mml:mi>\n =<\/mml:mo>\n 6<\/mml:mn>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n \u201321 over the scanner energy range from 7 to 115 keV. A QRM spectral-computed tomography (CT) phantom containing soft-tissue-equivalent, hydroxyapatite and iodine inserts was scanned on a MARS Microlab 5\n \n \n \n <\/jats:tex-math>\n \n \n \u00d7<\/mml:mo>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n 120 SPCCT system in five detector energy bins. For each bin, reconstructed SPCCT\n \n \n \n <\/jats:tex-math>\n \n \n \u03bc<\/mml:mi>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n images were linearly calibrated to NIST\n \n \n \n <\/jats:tex-math>\n \n \n \u03bc<\/mml:mi>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n , and the calibrated\n \n \n \n <\/jats:tex-math>\n \n \n \u03bc<\/mml:mi>\n (<\/mml:mo>\n E<\/mml:mi>\n )<\/mml:mo>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n served as input to four-window and dual-energy models to estimate voxelwise\n \n \n \n <\/jats:tex-math>\n \n \n \n Z<\/mml:mi>\n \n \n eff<\/mml:mi>\n <\/mml:mrow>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n and\n \n \n \n <\/jats:tex-math>\n \n \n \n \u03c1<\/mml:mi>\n \n e<\/mml:mi>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n . The same calibration and model were applied, without retuning, to a meat sample with embedded iodine vials.\n Main results.<\/jats:italic>\n Using NIST\n \n \n \n <\/jats:tex-math>\n \n \n \u03bc<\/mml:mi>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n as input, the four-window formalism gave mean absolute errors of approximately 1% for both\n \n \n \n <\/jats:tex-math>\n \n \n \n Z<\/mml:mi>\n \n \n eff<\/mml:mi>\n <\/mml:mrow>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n and\n \n \n \n <\/jats:tex-math>\n \n \n \n \u03c1<\/mml:mi>\n \n e<\/mml:mi>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n . On calibrated SPCCT images, errors were 4.9% and 2.1% for\n \n \n \n <\/jats:tex-math>\n \n \n \n Z<\/mml:mi>\n \n \n eff<\/mml:mi>\n <\/mml:mrow>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n and\n \n \n \n <\/jats:tex-math>\n \n \n \n \u03c1<\/mml:mi>\n \n e<\/mml:mi>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n with the four-window model, and 3.6% and 1.7% with the best dual-energy pair (50\u201360 \/ 60\u201379 keV). The same framework, applied without retuning, separated fat, muscle, bone and iodine in the heterogeneous meat sample.\n Significance.<\/jats:italic>\n A scanner-specific power law model of\n \n \n \n <\/jats:tex-math>\n \n \n \u03bc<\/mml:mi>\n (<\/mml:mo>\n E<\/mml:mi>\n )<\/mml:mo>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n combined with bin-wise linear calibration can deliver accurate\n \n \n \n <\/jats:tex-math>\n \n \n \n Z<\/mml:mi>\n \n \n eff<\/mml:mi>\n <\/mml:mrow>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n and\n \n \n \n <\/jats:tex-math>\n \n \n \n \u03c1<\/mml:mi>\n \n e<\/mml:mi>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n from a single SPCCT acquisition. Optimized dual-energy windows achieve near-percent\n \n \n \n <\/jats:tex-math>\n \n \n \n \u03c1<\/mml:mi>\n \n e<\/mml:mi>\n <\/mml:mrow>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>\n <\/jats:inline-formula>\n accuracy for clinically relevant materials, providing a quantitative basis for tissue characterization with photon-counting CT.\n <\/jats:p>","DOI":"10.1088\/1361-6560\/ae8aab","type":"journal-article","created":{"date-parts":[[2026,7,14]],"date-time":"2026-07-14T22:54:22Z","timestamp":1784069662000},"page":"145015","update-policy":"https:\/\/doi.org\/10.1088\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Power law spectral photon-counting CT for quantitative effective atomic number and electron density imaging"],"prefix":"10.1088","volume":"71","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-4655-1517","authenticated-orcid":true,"given":"Mohammed","family":"Alzaabi","sequence":"first","affiliation":[{"name":"Khalifa University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8569-6128","authenticated-orcid":false,"given":"Abderaouf","family":"Behouch","sequence":"additional","affiliation":[{"name":"Khalifa University"},{"name":"Ferhat Abbes University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-7881-4399","authenticated-orcid":true,"given":"Briya","family":"Tariq","sequence":"additional","affiliation":[{"name":"Khalifa University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aamir","family":"Raja","sequence":"additional","affiliation":[{"name":"Khalifa University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6633-6223","authenticated-orcid":true,"given":"Nabil","family":"Maalej","sequence":"additional","affiliation":[{"name":"Khalifa University"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"266","published-online":{"date-parts":[[2026,7,27]]},"reference":[{"key":"pmbae8aabbib1","doi-asserted-by":"publisher","DOI":"10.1088\/1748-0221\/6\/01\/C01059","type":"journal-article","article-title":"Pixel sensitivity variations in a CdTe-Medipix2 detector using poly-energetic x-rays","volume":"6","author":"Aamir","year":"2011","journal-title":"J. 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