5 Hardware Components
5.1 Components
Pre-Patient Collimator
The collimator contains two independently controlled blades. The motion of the blades provides
continuously variable beam thickness and Z-axis position. The collimator also has three bow-tie
beam filters that filter and shape the beam to optimize dose and image quality.
Gemstone Clarity Detector
Features a unique 3-dimensional post patient collimator to ensure HU uniformity and to
minimize scatter / beam hardening artifacts associated with wide coverage systems. Provides
160 mm coverage, 512 slices from 256 detector rows in the Z direction. The 256 rows are 0.625
mm in the Z direction. Each signal can be collected from an individual detector row. The
Gemstone scintillator material is created from garnet gemstones fused with a rare earth
phosphor composition.
5.2 Coverage
The Axial Detector Coverage/Beam Collimation for the 512-slice system are 5, 40, 80, 120, 140,
and 160 mm beam collimation/detector coverage (0.625 mm).
Table 12: Images per Rotation
Slice Thickness
(mm)
Detector Coverage (mm)
5 40 80 120 140 160
5 1i 8i 16i 24i 28i 32i
2.5 2i 16i 32i 48i 56i 64i
1.25 4i 32i 64i 96i 112i 128i
0.625 NA 64i 128i 192i 224i 256i
0.625z NA 128i 256i 384i 448i 512i
5.3 Axial interval
The interval is equal to the number of images per rotation times the beam collimation, e.g., in
the 256 x 0.625 mode, 256 images are generated, each 0.625 mm thick for a total of 160 mm of
coverage protection. For collimation greater than 40 mm, a slight overlap is applied when the
acquisition contains multiple table locations.
5.4 Helical pitch, scan mode, and collimation
Scan modes for helical are expressed in terms of pitch. Helical pitch is defined as the ratio of
table travel per rotation in millimeters divided by the beam collimation. Previous systems
expressed scan modes with names and defined pitch as table travel per rotation in millimeters
divided by the detector row width.
For example: 55/40 mm = 1.375: 1 (Table Speed (55) divided by the Beam Collimation (40 mm)
equals a Pitch of 1.375.
The following pitches are available:
Revolution CT User Manual
Direction 5480385-1EN, Revision 1
Chapter 8 Equipment 183
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