{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,26]],"date-time":"2026-09-26T03:34:58Z","timestamp":1790393698427,"version":"4.1.0"},"reference-count":42,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2018,3,1]],"date-time":"2018-03-01T00:00:00Z","timestamp":1519862400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"name":"Philips Healthcare"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2018,4]]},"abstract":"<jats:sec><jats:title>Purpose<\/jats:title><jats:p>Photon\u2010counting detectors using CdTe or <jats:styled-content style=\"fixed-case\">CZT<\/jats:styled-content> substrates are promising candidates for future <jats:styled-content style=\"fixed-case\">CT<\/jats:styled-content> systems but suffer from a number of nonidealities, including charge sharing and pulse pileup. By increasing the pixel size of the detector, the system can improve charge sharing characteristics at the expense of increasing pileup. The purpose of this work is to describe these considerations in the optimization of the detector pixel pitch.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>The transport of x rays through the CdTe substrate was simulated in a Monte Carlo fashion using <jats:styled-content style=\"fixed-case\">GEANT<\/jats:styled-content>4. Deposited energy was converted into charges distributed as a Gaussian function with size dependent on interaction depth to capture spreading from diffusion and Coulomb repulsion. The charges were then collected in a pixelated fashion. Pulse pileup was incorporated separately with Monte Carlo simulation. The Cram\u00e9r\u2013Rao lower bound (<jats:styled-content style=\"fixed-case\">CRLB<\/jats:styled-content>) of the measurement variance was numerically estimated for the basis material projections. Noise in these estimates was propagated into <jats:styled-content style=\"fixed-case\">CT<\/jats:styled-content> images. We simulated pixel pitches of 250, 350, and 450 microns and compared the results to a photon counting detector with pileup but otherwise ideal energy response and an ideal dual\u2010energy system (80\/140\u00a0<jats:styled-content style=\"fixed-case\">kV<\/jats:styled-content>p with tin filtration). The modeled CdTe thickness was 2\u00a0mm, the incident spectrum was 140\u00a0<jats:styled-content style=\"fixed-case\">kV<\/jats:styled-content>p and 500\u00a0<jats:styled-content style=\"fixed-case\">mA<\/jats:styled-content>, and the effective dead time was 67\u00a0ns. Charge summing circuitry was not modeled. We restricted our simulations to objects of uniform thickness and did not consider the potential advantage of smaller pixels at high spatial frequencies.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>At very high x\u2010ray flux, pulse pileup dominates and small pixel sizes perform best. At low flux or for thick objects, charge sharing dominates and large pixel sizes perform best. At low flux and depending on the beam hardness, the <jats:styled-content style=\"fixed-case\">CRLB<\/jats:styled-content> of variance in basis material projections tasks can be 32%\u201355% higher with a 250 micron pixel pitch compared to a 450 micron pixel pitch. However, both are about four times worse in variance than the ideal photon counting detector. The optimal pixel size depends on a number of factors such as x\u2010ray technique and object size. At high technique (140\u00a0<jats:styled-content style=\"fixed-case\">kV<\/jats:styled-content>p\/500\u00a0<jats:styled-content style=\"fixed-case\">mA<\/jats:styled-content>), the ratio of variance for a 450 micron pixel compared to a 250 micron pixel size is 2126%, 200%, 97%, and 78% when imaging 10, 15, 20, and 25\u00a0cm of water, respectively. If 300\u00a0mg\/cm<jats:sup>2<\/jats:sup> of iodine is also added to the object, the variance ratio is 117%, 91%, 74%, and 72%, respectively. Nonspectral tasks, such as equivalent monoenergetic imaging, are less sensitive to spectral distortion.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>The detector pixel size is an important design consideration in CdTe detectors. Smaller pixels allow for improved capabilities at high flux but increase charge sharing, which in turn compromises spectral performance. The optimal pixel size will depend on the specific task and on the charge shaping time.<\/jats:p><\/jats:sec>","DOI":"10.1002\/mp.12799","type":"journal-article","created":{"date-parts":[[2018,2,8]],"date-time":"2018-02-08T10:36:50Z","timestamp":1518086210000},"page":"1433-1443","source":"Crossref","is-referenced-by-count":37,"title":["Spectral resolution and high\u2010flux capability tradeoffs in CdTe detectors for clinical <scp>CT<\/scp>"],"prefix":"10.1002","volume":"45","author":[{"given":"Scott S.","family":"Hsieh","sequence":"first","affiliation":[{"name":"Department of Radiological Sciences UCLA Los Angeles CA 90024 USA"},{"name":"Departments of Radiology Stanford University Stanford CA 94305 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Paurakh L.","family":"Rajbhandary","sequence":"additional","affiliation":[{"name":"Departments of Radiology Stanford University Stanford CA 94305 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Norbert J.","family":"Pelc","sequence":"additional","affiliation":[{"name":"Departments of Radiology Stanford University Stanford CA 94305 USA"},{"name":"Departments of Bioengineering Stanford University Stanford CA 94305 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2018,3]]},"reference":[{"key":"e_1_2_6_2_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4820371"},{"key":"e_1_2_6_3_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3512794"},{"key":"e_1_2_6_4_1","doi-asserted-by":"publisher","DOI":"10.1063\/1.1662918"},{"key":"e_1_2_6_5_1","doi-asserted-by":"publisher","DOI":"10.1088\/0031-9155\/52\/15\/020"},{"key":"e_1_2_6_6_1","doi-asserted-by":"crossref","unstructured":"BarberWC NygardE IwanczykJS et\u00a0al. 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