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Four Multidetector-Row Helical CT: Image Quality and Volume Coverage Speed¹

¹ From GE Medical Systems, Milwaukee, Wis. From the 1998 RSNA scientific assembly. Received March 11, 1999; revision requested May 5; final revision received September 20; accepted October 4. Address reprint requests to H.H., 20720 W Watertown Rd, Suite 201, Waukesha, WI 53186 (e-mail: hui.hu@imagingtechinc.com).

View larger version (27K): [in a new window]   Figure 1a. Diagrams depict perspective views of the (a) single and (b) four multidetector-row helical CT scanners. (Reprinted, with permission, from reference 11.) In a, 1D = one-dimensional; in b, 2D = two-dimensional.

View larger version (33K): [in a new window]   Figure 1b. Diagrams depict perspective views of the (a) single and (b) four multidetector-row helical CT scanners. (Reprinted, with permission, from reference 11.) In a, 1D = one-dimensional; in b, 2D = two-dimensional.

View larger version (110K): [in a new window]   Figure 2. Corresponding images obtained with 5.0-mm section thickness of a body phantom acquired with various helical CT modes. Left column, top to bottom: Single multidetector-row helical CT scans obtained with table speeds of 5.0, 7.5, 10.0, and 15.0 mm per rotation (rot) and pitches of 1.0, 1.5, 2.0, 3.0, respectively. Right column, top to bottom: Four multidetector-row helical CT scans acquired with table speed (millimeters per rotation) and detector-row beam collimation (millimeters), respectively, of (top three images with 3:1 pitch) 7.5 and 2.5, 11.25 and 3.75, 15.0 and 5.0, and (bottom three images with 6:1 pitch) 15.0 and 2.5, 22.5 and 3.75, and 30.0 and 5.0 (Table 1). Display window width, 350 HU and level, 30 HU. The image artifacts in the right column were assessed by using those in the left column as benchmarks.

View larger version (111K): [in a new window]   Figure 3a. (a) Maximum intensity projection and (b) multiplanar reformation images from a renal donor study acquired with four multidetector-row helical CT (120 kVp, 370 mA, 0.8 second, table speed of 7.5 mm per rotation, 1.25-mm detector-row beam collimation, 1.25-mm reconstruction interval) with 234-mm coverage in 25 seconds and a 1.6-mm (nominal, 1.25-mm) section thickness. One hundred fifty milliliters of 60% contrast material (Omnipaque 300; Nycomed, Princeton, NJ) was injected at 5 mL/sec after the injection-to-scanning delay was determined with a preliminary small bolus (5 mL/sec for 4 seconds; then, transverse scanning of upper abdominal aorta after beginning of bolus and continued at 2-second intervals for 20 seconds). Bilateral accessory renal arteries to both renal hila are depicted clearly. In a, mesenteric arterial branches overlie the renal hila. In b, the separate aortic orifices (arrowheads) of all four renal arteries are demonstrated, and both left renal arteries are visible to their segmental divisions.

View larger version (102K): [in a new window]   Figure 3b. (a) Maximum intensity projection and (b) multiplanar reformation images from a renal donor study acquired with four multidetector-row helical CT (120 kVp, 370 mA, 0.8 second, table speed of 7.5 mm per rotation, 1.25-mm detector-row beam collimation, 1.25-mm reconstruction interval) with 234-mm coverage in 25 seconds and a 1.6-mm (nominal, 1.25-mm) section thickness. One hundred fifty milliliters of 60% contrast material (Omnipaque 300; Nycomed, Princeton, NJ) was injected at 5 mL/sec after the injection-to-scanning delay was determined with a preliminary small bolus (5 mL/sec for 4 seconds; then, transverse scanning of upper abdominal aorta after beginning of bolus and continued at 2-second intervals for 20 seconds). Bilateral accessory renal arteries to both renal hila are depicted clearly. In a, mesenteric arterial branches overlie the renal hila. In b, the separate aortic orifices (arrowheads) of all four renal arteries are demonstrated, and both left renal arteries are visible to their segmental divisions.

View larger version (138K): [in a new window]   Figure 4. Transverse (top row) and coronal (bottom row) multiplanar reformation images of the upper abdomen reconstructed from a single multidetector-row helical CT acquisition (140 kVp, 260 mA, 0.8 second, table speed of 15.0 mm per rotation, 2.5-mm detector beam collimation, 1.25-mm reconstruction interval) with 225-mm coverage in 12 seconds and nominal section thicknesses of 5.0 mm (right column) and 2.5 mm (left column). One hundred fifty milliliters of 60% contrast material was injected at 3 mL/sec with an injection-to-scanning delay of 60 seconds. The thinner sections (left column) show sharper delineation of a dilated pancreatic duct (arrowhead in top row) and the adrenal glands, renal contour, and hemidiaphragms (arrowheads in bottom row) and are preferred for sharper z resolution. The thick sections (right column) may be preferred for reduced image noise and for fewer images to be archived and reviewed. (Image courtesy of Rendon C. Nelson, MD, Department of Radiology, Duke University Medical Center, Durham, NC.)