Table TID 10014. Scanning Length
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IFF TID 10013 “CT Irradiation Event Data” Row 4 CT Acquisition Type equals (116152004, SCT, "Spiral Acquisition") |
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EV (113895, DCM, "Top Z Location of Reconstructable Volume") |
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EV (113896, DCM, "Bottom Z Location of Reconstructable Volume") |
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IF any of Rows 4 through 7 or Row 34e of TID 10013 are present. |
If present, shall be the same UID as in the images reconstructed from this irradiation event. |
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For Spiral scanning, the scanning length is normally the table travel in mm during the tube loading (see Figure A-16). For Sequenced scanning, the scanning length is the table travel between consecutive scans times the number of scans. For Stationary and Free scanning, the scanning length is the nominal width of the total collimation. |
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The length of the reconstructable volume is the maximum z-range between the outermost edges of the top and bottom slices that can be reconstructed from the acquisition. For Spiral scanning, the length of reconstructable volume is the z-range between the outermost beginning of the first reconstructable slice and the outermost end of the last reconstructable slice (see Figure A-16). For Sequenced scanning, the length of reconstructable volume is the z-range between the outermost beginning of the first slice and the outermost end of the last slice (i.e., including any skip). For Stationary and Free scanning, the length of reconstructable volume is the nominal width of the total collimation. |
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For Spiral scanning, the exposed range is as defined in [IEC 60601-2-44] (Ed. 3) 203.115(b) (see Figure A-16). |
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The Top and Bottom Z Locations of the Reconstructable Volume are independent of the slice width of any actual reconstructed slices. They are measured from the edges of the volume, and hence are not equal to the Z locations encoded in the images of any actual reconstructed slices, which are recorded as the center of the slice. |
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These locations are patient (not table or gantry) relative, to allow them to be defined in the Patient Coordinate System and hence related to the Image Position (Patient) in the reconstructed images. They are also defined in terms of the top (towards the patient's head), and bottom (towards the patient's feet) of the corresponding ranges, in order to make them independent of whether the scan starts at the top or the bottom or shuttles back and forth in between (see Figure A-16). |
