{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,10]],"date-time":"2026-10-10T00:04:12Z","timestamp":1791590652740,"version":"4.3.4"},"reference-count":23,"publisher":"Wiley","issue":"6","license":[{"start":{"date-parts":[[2021,4,15]],"date-time":"2021-04-15T00:00:00Z","timestamp":1618444800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["aapm.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2021,6]]},"abstract":"<jats:sec><jats:title>Purpose<\/jats:title><jats:p>The purpose of this study was to quantify location and direction\u2010dependent variations in the 3D modulation transfer function (MTF) of a high\u2010resolution CT scanner with selectable focal spot sizes and resolution modes.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>The Aquilion Precision CT scanner (Canon Medical Systems) has selectable 0.25\u00a0mm or 0.5\u00a0mm detectors (by binning) in both the axial (x\u2010y) and detector array width (z) directions. For the x\u2010y and z orientations, detectors are configured (x\u2013y)\u00a0=\u00a00.5 mm\/(z)\u00a0=\u00a00.5\u00a0mm for normal resolution (NR), 0.25\/0.5\u00a0mm for high resolution (HR), and 0.25\/0.25\u00a0mm for super high resolution (SHR). Six focal spots (FS1\u2010FS6) range in size from 0.4 (x\u2010y)\u00a0\u00d7\u00a00.5\u00a0mm (z) for FS1 to 1.6\u00a0\u00d7\u00a01.4\u00a0mm for FS6. Phantoms fabricated from spherical objects were positioned at radial distances of 0, 4.0, 7.5, 11.0, 14.5, and 18.5\u00a0cm. Axial and helical acquisitions were utilized and reconstructed using filtered back projection with the FC18 \u201cBody,\u201d FC30 \u201cBone,\u201d and FC81 \u201cBone Sharp\u201d kernels. The reconstructions were used to measure a 1D slice of the 3D MTF by oversampling the 3D ESF in the axial plane [<jats:italic>MTF<\/jats:italic>(<jats:italic>f<\/jats:italic><jats:sub>r<\/jats:sub>); <jats:italic>\u03c6<\/jats:italic>\u00a0=\u00a00\u00b0)], 45\u00b0 out of the axial plane [<jats:italic>MTF<\/jats:italic>(<jats:italic>f<\/jats:italic><jats:sub>r<\/jats:sub>); <jats:italic>\u03c6<\/jats:italic>\u00a0=\u00a045\u00b0)], in the longitudinal direction [<jats:italic>MTF<\/jats:italic>(<jats:italic>f<\/jats:italic><jats:sub>r<\/jats:sub>); <jats:italic>\u03c6<\/jats:italic>\u00a0=\u00a080\u00b0)], and along the radial and azimuthal directions within the axial plane.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The <jats:italic>MTF<\/jats:italic>(<jats:italic>f<\/jats:italic><jats:sub>r<\/jats:sub>); <jats:italic>\u03c6<\/jats:italic>\u00a0=\u00a045\u00b0) drops to 10% (<jats:italic>f<\/jats:italic><jats:sub>10<\/jats:sub>) at 1.20, 1.45, and 2.06\u00a0mm<jats:sup>\u22121<\/jats:sup> for NR, HR, and SHR, respectively, for a helical acquisition with FS1, FC30, and <jats:italic>r<\/jats:italic>\u00a0=\u00a04\u00a0cm from the isocenter. The <jats:italic>MTF<\/jats:italic>(<jats:italic>f<\/jats:italic><jats:sub>r<\/jats:sub>); <jats:italic>\u03c6<\/jats:italic>\u00a0=\u00a045\u00b0) includes contributions of both the axial\u2010plane MTF (<jats:italic>f<\/jats:italic><jats:sub>10<\/jats:sub>\u00a0=\u00a01.10, 2.04, and 2.01\u00a0mm<jats:sup>\u22121<\/jats:sup>) and the longitudinal MTF (<jats:italic>f<\/jats:italic><jats:sub>10<\/jats:sub>\u00a0=\u00a01.17, 1.18, and 1.82\u00a0mm<jats:sup>\u22121<\/jats:sup>) for the NR, HR, and SHR modes, respectively. For SHR, the axial scan mode showed a 15\u201325% improvement over helical mode in the longitudinal resolution. Helical pitch, ranging from 0.569 to 1.381, did not appreciably affect the 3D resolution (&lt;2%). The radial MTFs across the axial field of view (FOV) showed dependencies on the focal spot length in z; for example, for SHR with FS2 (0.6\u00a0\u00d7\u00a00.6\u00a0mm), <jats:italic>f<\/jats:italic><jats:sub>10<\/jats:sub> at\u00a0 <jats:italic>r<\/jats:italic>\u00a0=\u00a011\u00a0cm was within 17% of the value at <jats:italic>r<\/jats:italic>\u00a0=\u00a04\u00a0cm, but for SHR with FS3 (0.6\u00a0\u00d7\u00a01.3), the reduction in <jats:italic>f<\/jats:italic><jats:sub>10<\/jats:sub> was 46% from 4 to 11\u00a0cm from the isocenter. The azimuthal MTF also decreased as <jats:italic>r<\/jats:italic> increased but less so for longer gantry rotation times and smaller focal spot dimensions in the axial plane. The longitudinal MTF was minimally affected (&lt;11%) by position in the FOV and was principally affected by the focal spot length in the z\u2010dimension.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>The 3D MTF was measured throughout the FOV of a high\u2010resolution CT scanner, quantifying the advantages of different resolution modes and focal spot sizes on the axial\u2010plane and longitudinal MTF. Reconstruction kernels were shown to impact axial\u2010plane resolution, imparting non\u2010isotropic 3D resolution characteristics. Focal spot size (both in x\u2010y and in z) and gantry rotation time play important roles in preserving the high\u2010resolution characteristics throughout the field of view for this new high\u2010resolution CT scanner technology.<\/jats:p><\/jats:sec>","DOI":"10.1002\/mp.14789","type":"journal-article","created":{"date-parts":[[2021,2,20]],"date-time":"2021-02-20T08:06:16Z","timestamp":1613808376000},"page":"2760-2771","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":33,"title":["Location and direction dependence in the 3D MTF for a high\u2010resolution CT system"],"prefix":"10.1002","volume":"48","author":[{"given":"Andrew M.","family":"Hernandez","sequence":"first","affiliation":[{"name":"Department of Radiology University of California Davis Sacramento CA 95817 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pengwei","family":"Wu","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering Johns Hopkins University Baltimore MD 21205 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mahadevappa","family":"Mahesh","sequence":"additional","affiliation":[{"name":"Russell H. Morgan Department of Radiology Johns Hopkins University Baltimore MD 21205 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jeffrey H.","family":"Siewerdsen","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering Johns Hopkins University Baltimore MD 21205 USA"},{"name":"Russell H. Morgan Department of Radiology Johns Hopkins University Baltimore MD 21205 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"John M.","family":"Boone","sequence":"additional","affiliation":[{"name":"Department of Radiology University of California Davis Sacramento CA 95817 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2021,4,15]]},"reference":[{"key":"e_1_2_8_2_1","doi-asserted-by":"publisher","DOI":"10.1007\/s10140-006-0493-9"},{"key":"e_1_2_8_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jcct.2012.04.005"},{"key":"e_1_2_8_4_1","doi-asserted-by":"publisher","DOI":"10.1146\/annurev-bioeng-121813-113601"},{"key":"e_1_2_8_5_1","doi-asserted-by":"publisher","DOI":"10.3233\/XST-2010-0258"},{"key":"e_1_2_8_6_1","doi-asserted-by":"crossref","first-page":"e0137165","DOI":"10.1371\/journal.pone.0137165","article-title":"Ultra\u2010high\u2010resolution computed tomography of the lung: image quality of a prototype scanner","volume":"10","author":"Kakinuma R","year":"2015","journal-title":"PLoS One"},{"key":"e_1_2_8_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.acra.2017.11.017"},{"key":"e_1_2_8_8_1","doi-asserted-by":"publisher","DOI":"10.1186\/s13244-019-0685-y"},{"key":"e_1_2_8_9_1","doi-asserted-by":"publisher","DOI":"10.1120\/jacmp.v17i3.6039"},{"key":"e_1_2_8_10_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4946816"},{"key":"e_1_2_8_11_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.2737263"},{"key":"e_1_2_8_12_1","unstructured":"HsiehJ.Computed tomography: principles design artifacts and recent advances. 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