{"id":98,"date":"2018-03-19T08:45:51","date_gmt":"2018-03-19T13:45:51","guid":{"rendered":"https:\/\/pctk.jhu.edu\/?page_id=98"},"modified":"2018-04-17T23:06:08","modified_gmt":"2018-04-18T04:06:08","slug":"faq","status":"publish","type":"page","link":"https:\/\/pctk.jhu.edu\/index.php\/faq\/","title":{"rendered":"FAQ"},"content":{"rendered":"<p>Looking for more information? The following information may be helpful for you.<\/p>\n<ul>\n<li>How can the users create the material-specific volume images (<em>a<sub>k<\/sub><\/em>) similar to the ones used\u00a0for CT workflow (Fig. 9) of the PcTK paper (Ref. 1)? (03-19-2018, 04-17-2018)\n<ul>\n<li>Our procedure is described in Sec. 3.C of Ref. 1. Users are encouraged to develop better procedures and share their programs for the community spirit with us. Please send us an email if you are willing.<\/li>\n<li>The material-specific volume images (<em>a<sub>xyz,<\/sub><sub>k<\/sub><\/em>) for the &#8220;basis material&#8221;\u00a0<em>k<\/em>\u00a0we used for Ref. 1 was calculated as follows. The local linear attenuation coefficient at <em>xyz,<\/em> <em>\u00b5<sub>xyz<\/sub><\/em>, are modeled by a linear combination of multiple basis materials <em>k<\/em> as <em>\u00b5<sub>xyz<\/sub> = <\/em>\u2211<em><sub>k<\/sub><\/em> <em>r<\/em><em><sub>xyz<\/sub><\/em><em> w<sub>xyz,k<\/sub><\/em> (<em>\u00b5<sub>k<\/sub> \/<\/em><em>r<sub>k<\/sub><\/em>) = \u2211<em><sub> k<\/sub><\/em> <em>a<sub>xyz,k\u00a0<\/sub>\u00b5<sub>k<\/sub><\/em>, where <em>r<sub>xyz<\/sub><\/em>\u00a0is the local density of the object at <em>xyz<\/em>,\u00a0<em>w<sub>xyz,k<\/sub><\/em>\u00a0is the local fraction-by-weight of the density of the material <em>k<\/em>, (<em>\u00b5<sub>k<\/sub> \/<\/em><em>r<sub>k<\/sub><\/em>)\u00a0is the energy-dependent mass attenuation coefficient of the material <em>k<\/em>, and <em>r<sub>k<\/sub><\/em>\u00a0is\u00a0the density of the material <em>k\u00a0<\/em>at the standard state. A material-specific line integrals <em>v<sub>k,j<\/sub><\/em>\u00a0for material <em>k<\/em> and a sinogram pixel <em>j<\/em> can then be calculated by forward projecting <em>a<sub>xyz,<\/sub><sub>k<\/sub><\/em>\u00a0as <em>v<sub>k,j<\/sub>= <\/em>\u2211<em><sub>xyz<\/sub><\/em> <em>h<sub>xyz,j<\/sub> a<sub>xyz,k<\/sub><\/em>, where <em>h<sub>xyz,j<\/sub><\/em>\u00a0is an element of the projection system matrix <em>H<sub>xyz<\/sub><\/em>\u00a0and a product of <em>v<sub>k,j<\/sub><\/em>\u00a0and\u00a0<em>\u00b5<sub>k\u00a0<\/sub><\/em>is used to calculate the attenuated spectrum <em>S<sub>t,j<\/sub><\/em>\u00a0for the sinogram pixel\u00a0<em>j<\/em>. Some of the data can be found in the folder 1_inputdata or 5_refdata. But again, the above was merely our choice made to demonstrate PcTK and CT workflow; users should use their way to define <em>a<sub>xyz,k<\/sub><\/em>\u00a0and calculate <em>v<sub>k,j<\/sub><\/em>.<\/li>\n<li>The mass attenuation coefficients and other properties of various materials are provided in <a href=\"https:\/\/doi.org\/10.1093\/jicru\/os23.1.Report44\">ICRU Report 44<\/a> as well as <a href=\"https:\/\/www.nist.gov\/pml\/x-ray-mass-attenuation-coefficients\">National Institute of Standards and Technology (NIST)<\/a><strong>.\u00a0<\/strong><\/li>\n<\/ul>\n<\/li>\n<li>Can the number of material-specific sinograms for CT workflow more than 2? (03-22-2018)\n<ul>\n<li>Yes, it can be any large number or as few as 1. You just need to modify the workflow code to read data and use them to calculate the attenuated spectrum incident onto the PCD pixels, <em>S<sub>t,j<\/sub><\/em>(<em>E<\/em><sub>1<\/sub>). You also need to prepare (1) material-specific sinograms (data (C) in Sec. 2.C of PcTK paper), and (2) the corresponding energy-dependent linear attenuation coefficients for each material (data (D)).<\/li>\n<li>It is advised to check the image quality of CT images at different energies such as 40, 70, 100, and 130 keV, prior to proceed and generate material-specific sinograms. Often artifacts, thus, problems, are more apparent with the material-specific density images (<em>a<sub>ST <\/sub><\/em>and <em>a<sub>BN<\/sub><\/em>\u00a0in Fig. 9 of PcTK paper) than the material-specific sinograms.<\/li>\n<\/ul>\n<\/li>\n<li>What are the geometry parameters used for CT workflow (Fig. 9) of the PcTK paper (Ref. 1)? (03-19-2018)\n<ul>\n<li>Focus-to-detector distance: 1,080 mm<\/li>\n<li>Focus-to-iso-center distance: 600 mm<\/li>\n<li>Detector pixel size at the detector (not the projected size at the iso-center): 225 \u00b5m<\/li>\n<li>Detector shape: Cylindrical detector with equi-angular sampling<\/li>\n<li>The other parameters (i.e., the number of detector channels and rows) must be apparent or can be calculated from the size of data (.mat files) or specified in Ref. 1.<\/li>\n<\/ul>\n<\/li>\n<li>What is the format of .flt data? (03-19-2018)\n<ul>\n<li>It is\u00a032-bit floating data with no header.<\/li>\n<\/ul>\n<\/li>\n<li>Which forward projector would you recommend?\u00a0(03-19-2018)\n<ul>\n<li>Any projector will be fine and please send us information on available projectors.<\/li>\n<li>We used an in-house projector for Ref. 1 and are using <a href=\"https:\/\/www.astra-toolbox.com\">ASTRA toolbox<\/a> for other projects.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Looking for more information? The following information may be helpful for you. How can the users create the material-specific volume images (ak) similar to the ones used\u00a0for CT workflow (Fig. 9) of the PcTK paper (Ref. 1)? (03-19-2018, 04-17-2018) Our procedure is described in Sec. 3.C of Ref. 1. Users are encouraged to develop better &hellip; <\/p>\n<p class=\"read-more\"><a class=\"btn btn-default\" href=\"https:\/\/pctk.jhu.edu\/index.php\/faq\/\"> Read More<span class=\"screen-reader-text\">  Read More<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"class_list":["post-98","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/pctk.jhu.edu\/index.php\/wp-json\/wp\/v2\/pages\/98","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pctk.jhu.edu\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/pctk.jhu.edu\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/pctk.jhu.edu\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pctk.jhu.edu\/index.php\/wp-json\/wp\/v2\/comments?post=98"}],"version-history":[{"count":14,"href":"https:\/\/pctk.jhu.edu\/index.php\/wp-json\/wp\/v2\/pages\/98\/revisions"}],"predecessor-version":[{"id":131,"href":"https:\/\/pctk.jhu.edu\/index.php\/wp-json\/wp\/v2\/pages\/98\/revisions\/131"}],"wp:attachment":[{"href":"https:\/\/pctk.jhu.edu\/index.php\/wp-json\/wp\/v2\/media?parent=98"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}