{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,12]],"date-time":"2026-04-12T03:54:45Z","timestamp":1775966085353,"version":"3.50.1"},"reference-count":29,"publisher":"Wiley","issue":"6Part1","license":[{"start":{"date-parts":[[2013,5,13]],"date-time":"2013-05-13T00:00:00Z","timestamp":1368403200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"},{"start":{"date-parts":[[2015,9,1]],"date-time":"2015-09-01T00:00:00Z","timestamp":1441065600000},"content-version":"tdm","delay-in-days":841,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"funder":[{"DOI":"10.13039\/100006129","name":"Fuel Cycle Technologies","doi-asserted-by":"publisher","award":["SFRH\/BD\/47075\/2008"],"award-info":[{"award-number":["SFRH\/BD\/47075\/2008"]}],"id":[{"id":"10.13039\/100006129","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100006129","name":"Fuel Cycle Technologies","doi-asserted-by":"publisher","award":["SFRH\/BPD\/79735\/2011"],"award-info":[{"award-number":["SFRH\/BPD\/79735\/2011"]}],"id":[{"id":"10.13039\/100006129","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000783","name":"Research Executive Agency","doi-asserted-by":"publisher","award":["301269"],"award-info":[{"award-number":["301269"]}],"id":[{"id":"10.13039\/501100000783","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100006129","name":"Fuel Cycle Technologies","doi-asserted-by":"publisher","award":["SFRH\/BD\/47075\/2008"],"award-info":[{"award-number":["SFRH\/BD\/47075\/2008"]}],"id":[{"id":"10.13039\/100006129","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100006129","name":"Fuel Cycle Technologies","doi-asserted-by":"publisher","award":["SFRH\/BPD\/79735\/2011"],"award-info":[{"award-number":["SFRH\/BPD\/79735\/2011"]}],"id":[{"id":"10.13039\/100006129","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000783","name":"Research Executive Agency","doi-asserted-by":"publisher","award":["301269"],"award-info":[{"award-number":["301269"]}],"id":[{"id":"10.13039\/501100000783","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["aip.org"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2013,6]]},"abstract":"<jats:sec><jats:title>Purpose:<\/jats:title><jats:p>The optimization of the collimator design is essential to obtain the best possible sensitivity in single photon emission computed tomography imaging. The aim of this work is to present a methodology for maximizing the sensitivity of convergent collimators, specifically designed to match the pitch of pixelated detectors, for a fixed spatial resolution value and to present some initial results using this approach.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods:<\/jats:title><jats:p>Given the matched constraint, the optimal collimator design cannot be simply found by allowing the highest level of septal penetration and spatial resolution consistent with the imposed restrictions, as it is done for the optimization of conventional collimators. Therefore, an algorithm that interactively calculates the collimator dimensions, with the maximum sensitivity, which respect the imposed restrictions was developed and used to optimize cone and fan beam collimators with tapered square\u2010shaped holes for low (60\u2013300 keV) and high energy radiation (300\u2013511 keV). The optimal collimator dimensions were locally calculated based on the premise that each hole and septa of the convergent collimator should locally resemble an appropriate optimal matched parallel collimator.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results:<\/jats:title><jats:p>The optimal collimator dimensions, calculated for subcentimeter resolutions (3 and 7.5 mm), common pixel sizes (1.6, 2.1, and 2.5 mm), and acceptable septal penetration at 140 keV, were approximately constant throughout the collimator, despite their different hole incidence angles. By using these input parameters and a less strict septal penetration value of 5%, the optimal collimator dimensions and the corresponding mass per detector area were calculated for 511 keV. It is shown that a low value of focal distance leads to improvements in the average sensitivity at a fixed source\u2010collimator distance and resolution. The optimal cone beam performance outperformed that of other optimal collimation geometries (fan and parallel beam) in imaging objects close to the collimator surface.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions:<\/jats:title><jats:p>These results demonstrate the potential of this kind of optimal convergent collimators for the use in small field of view imaging applications.<\/jats:p><\/jats:sec>","DOI":"10.1118\/1.4804053","type":"journal-article","created":{"date-parts":[[2013,5,13]],"date-time":"2013-05-13T22:00:47Z","timestamp":1368482447000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":6,"title":["Optimization of convergent collimators for pixelated SPECT systems"],"prefix":"10.1002","volume":"40","author":[{"given":"Ricardo M.","family":"Capote","sequence":"first","affiliation":[]},{"given":"Nuno","family":"Matela","sequence":"additional","affiliation":[]},{"given":"Raquel C.","family":"Concei\u00e7\u00e3o","sequence":"additional","affiliation":[]},{"given":"Pedro","family":"Almeida","sequence":"additional","affiliation":[]}],"member":"311","published-online":{"date-parts":[[2013,5,13]]},"reference":[{"key":"e_1_2_8_2_1","doi-asserted-by":"publisher","DOI":"10.1088\/0031\u20109155\/37\/3\/002"},{"key":"e_1_2_8_3_1","first-page":"135","article-title":"An evaluation of lesion detectability with cone\u2010beam, fan\u2010beam and parallel\u2010beam collimation in SPECT by continuous ROC study","volume":"35","author":"Li J.","year":"1994","journal-title":"J. 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