Performance evaluation of a multi-slice CT system.
Our purpose in this study was to characterize the performance of a recently introduced multi-slice CT scanner (LightSpeed QX/i, Version 1.0, General Electric Medical Systems) in comparison to a single-slice scanner from the same manufacturer (HiSpeed CT/i, Version 4.0). To facilitate this comparison, a refined definition of pitch is introduced which accommodates multi-slice CT systems, yet maintains the existing relationships between pitch, patient dose, and image quality. The following performance parameters were assessed: radiation and slice sensitivity profiles, low-contrast and limiting spatial resolution, image uniformity and noise, CT number and geometric accuracy, and dose. The multi-slice system was tested in axial (1, 2, or 4 images per gantry rotation) and HQ (Pitch = 0.75) and HS (Pitch = 1.5) helical modes. Axial and helical acquisition speed and limiting spatial resolution (0.8-s exposure) were improved on the multi-slice system. Slice sensitivity profiles, image noise, CT number accuracy and uniformity, and low-contrast resolution were similar. In some HS-helical modes, helical artifacts and geometric distortion were more pronounced with a different appearance. Radiation slice profiles and doses were larger on the multi-slice system at all scan widths. For a typical abdomen and pelvis exam, the central and surface body doses for 5-mm helical scans were higher on the multi-slice system by approximately 50%. The increase in surface CTDI values (with respect to the single-slice system) was greatest for the 4 x 1.25-mm detector configuration (190% for head, 240% for body) and least for the 4 x 5-mm configuration (53% for head, 76% for body). Preliminary testing of version 1.1 software demonstrated reduced doses on the multi-slice scanner, where the increase in body surface CTDI values (with respect to the single-slice system) was 105% for the 4 x 1.25-mm detector configuration and 10% for the 4 x 5-mm configuration. In summary, the axial and HQ-helical modes of the multi-slice system provided excellent image quality and a substantial reduction in exam time and tube loading, although at varying degrees of increased dose relative to the single-slice scanner.
McCollough
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Department of Diagnostic Radiology, Mayo Clinic, Rochester, Minnesota 55905, USA. mccollough.cynthia@mayo.edu
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D000180:Acrylic Resins; D000388:Air; D016477:Artifacts; D016014:Linear Models; D008422:Materials Testing; D019047:Phantoms, Imaging; D020959:Polyethylene; D011138:Polytetrafluoroethylene; D011856:Radiographic Image Enhancement / Q000379:methods*; D012680:Sensitivity and Specificity; D015898:Tomography Scanners, X-Ray Computed; D014057:Tomography, X-Ray Computed / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*
D000180:Acrylic Resins; D011138:Polytetrafluoroethylene; D020959:Polyethylene