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DOI: 10.1148/rg.276075120
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Technologic Advances in Multidetector CT with a Focus on Cardiac Imaging1

Dianna D. Cody, PhD and Mahadevappa Mahesh, PhD

1 From the Department of Imaging Physics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Unit 56, Houston, TX 77030 (D.D.C.); and the Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Md (M.M.). From the AAPM/RSNA Physics Tutorial at the 2005 RSNA Annual Meeting. Received May 17, 2007; revision requested June 20 and received July 6; accepted July 10. D.D.C. is a speaker for the Medical Technology Management Institute; M.M. receives research support from Siemens.

Figure 1
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  		Figure 1.  Mosaic detectors have elements that are all a uniform size. The thickness of the sections that can be generated from these detectors is a multiple value of the uniform size of the detector element. (In this case, sections can have a thickness of 1.25, 2.5, 3.75, 5, 7.5, or 10 mm.)

 

Figure 2
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  		Figure 2.  Variable or nonuniform detectors are composed of elements that are not uniform in size but can be combined with a postpatient collimator unit to generate sections with several different thickness values. (In this case, sections can have a thickness of 1, 2.5, 5, or 10 mm.)

 

Figure 3
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  		Figure 3.  Hybrid detectors are composed of elements that are not uniform in size, but in general only a limited number of element sizes is used. This design has been especially popular on 16-channel CT scanners across all manufacturers. The detector design shown is from a Toshiba four-channel scanner.

 

Figure 4
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  		Figure 4.  Detector array designs for CT scanners that can yield 64 images per gantry rotation.

 

Figure 5
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  		Figure 5.  SGraph shows the dose profile of a 5-mm-thick x-ray beam.

 

Figure 6A
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  		Figure 6a.  Effect of dose efficiency in different multiple-row detector CT scanners: four-channel scanners (a) versus a 16-channel scanner (b).

 

Figure 6B
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  		Figure 6b.  Effect of dose efficiency in different multiple-row detector CT scanners: four-channel scanners (a) versus a 16-channel scanner (b).

 

Figure 7
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  		Figure 7.  CTDIw values (normalized to the 16-channel scanner values) for four- (left), 16- (center), and 64- (right) channel multiple-row detector CT scanners from the same manufacturer. The four-channel acquisitions deliver higher dose index values than the 16- and 64-channel acquisitions owing to poor dose efficiency. Red bars = head CT dose, yellow bars = body CT dose.

 




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