What is 256-slice CT and 320-slice CT?

Updated: Dec 21, 2017
  • Author: Eugene C Lin, MD; Chief Editor: Eugene C Lin, MD  more...
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The primary advantage of 256- and 320-slice CT is the increased craniocaudal coverage.

The 256- and 320-slice CT scanners have a craniocaudal coverage of approximately 12 and 16 cm, respectively. This potentially allows the heart to be scanned in one tube rotation and one heartbeat, without table movement. This technique is ideal for the prospectively triggered sequential scan technique, [46] which substantially reduces radiation dose compared with retrospectively gated helical techniques (see Radiation Dose). If the prospectively triggered technique is used, heart rate control is useful, as a slower heart rate allows a narrower phase window to be used, [47] further decreasing radiation dose. Another advantage is that if the data can be acquired in one heartbeat, phase misregistration artifacts arising from irregular heartbeats are not an issue.

In a comparison of prospectively gated 64- and 256-slice CT, 256-slice CT provided significantly improved and more stable image quality compared with 64-slice CT, at equivalent effective radiation dose. [2]

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