{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,20]],"date-time":"2026-04-20T17:39:22Z","timestamp":1776706762846,"version":"3.51.2"},"reference-count":11,"publisher":"Wiley","issue":"10","license":[{"start":{"date-parts":[[2015,9,15]],"date-time":"2015-09-15T00:00:00Z","timestamp":1442275200000},"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":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["aip.org"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2015,10]]},"abstract":"<jats:sec><jats:title>Purpose:<\/jats:title><jats:p>To characterize the performance of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy (MR\u2010IGRT) system.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods:<\/jats:title><jats:p>The imaging performance characterization included four components: ACR (the American College of Radiology) phantom test, spatial integrity, coil signal to noise ratio (SNR) and uniformity, and magnetic field homogeneity. The ACR phantom test was performed in accordance with the ACR phantom test guidance. The spatial integrity test was evaluated using a 40.8 \u00d7 40.8 \u00d7 40.8 cm<jats:sup>3<\/jats:sup> spatial integrity phantom. MR and computed tomography (CT) images of the phantom were acquired and coregistered. Objects were identified around the surfaces of 20 and 35 cm diameters of spherical volume (DSVs) on both the MR and CT images. Geometric distortion was quantified using deviation in object location between the MR and CT images. The coil SNR test was performed according to the national electrical manufacturers association (NEMA) standards MS\u20101 and MS\u20109. The magnetic field homogeneity test was measured using field camera and spectral peak methods.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results:<\/jats:title><jats:p>For the ACR tests, the slice position error was less than 0.10 cm, the slice thickness error was less than 0.05 cm, the resolved high\u2010contrast spatial resolution was 0.09 cm, the resolved low\u2010contrast spokes were more than 25, the image intensity uniformity was above 93%, and the percentage ghosting was less than 0.22%. All were within the ACR recommended specifications. The maximum geometric distortions within the 20 and 35 cm DSVs were 0.10 and 0.18 cm for high spatial resolution three\u2010dimensional images and 0.08 and 0.20 cm for high temporal resolution two dimensional cine images based on the distance\u2010to\u2010phantom\u2010center method. The average SNR was 12.0 for the body coil, 42.9 for the combined torso coil, and 44.0 for the combined head and neck coil. Magnetic field homogeneities at gantry angles of 0\u00b0, 30\u00b0, 60\u00b0, 90\u00b0, and 120\u00b0 were 23.55, 20.43, 18.76, 19.11, and 22.22 ppm, respectively, using the field camera method over the 45 cm DSV.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions:<\/jats:title><jats:p>The onboard imaging unit of the first commercial MR\u2010IGRT system meets ACR, NEMA, and vendor specifications.<\/jats:p><\/jats:sec>","DOI":"10.1118\/1.4930249","type":"journal-article","created":{"date-parts":[[2015,9,15]],"date-time":"2015-09-15T17:00:48Z","timestamp":1442336448000},"page":"5828-5837","update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":56,"title":["Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system"],"prefix":"10.1002","volume":"42","author":[{"given":"Yanle","family":"Hu","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Leith","family":"Rankine","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Olga L.","family":"Green","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rojano","family":"Kashani","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H. 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Omar","family":"Wooten","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"James F.","family":"Dempsey","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sasa","family":"Mutic","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2015,9,15]]},"reference":[{"key":"e_1_2_6_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.semradonc.2014.02.008"},{"key":"e_1_2_6_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.semradonc.2014.02.012"},{"key":"e_1_2_6_4_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.2761342"},{"key":"e_1_2_6_5_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3125662"},{"key":"e_1_2_6_6_1","doi-asserted-by":"publisher","DOI":"10.1088\/0031\u20109155\/54\/12\/N01"},{"key":"e_1_2_6_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.semradonc.2014.02.015"},{"key":"e_1_2_6_8_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3190392"},{"key":"e_1_2_6_9_1","unstructured":"Phantom Test Guidance for the ACR MRI Accreditation Program American College of Radiology 2005."},{"key":"e_1_2_6_10_1","unstructured":"NEMA Standards Publication MS 1\u20102008: Determination of Signal\u2010to\u2010Noise Ratio (SNR) in Diagnostic Magnetic Resonance Imaging National Electrical Manufacturers Association 2008."},{"key":"e_1_2_6_11_1","unstructured":"NEMA Standards Publication MS 9\u20102008: Characterization of Phased Array Coils for Diagnostic Magnetic Resonance Images National Electrical Manufacturers Association 2008."},{"key":"e_1_2_6_12_1","article-title":"Acceptance testing and quality assurance procedures for magnetic resonance imaging facilities","author":"Jackson E. 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