Spiral or Helical CT

These CT scanners have a gantry that rotates continuously in the same direction. During scanning, data acquisition is combined with continuous movement of the patient through the gantry. The path of the X-rays can be described as a spiral or helix, hence the name helical or spiral CT. These scanners can acquire data for 20 to 60 seconds at a stretch, allowing them to scan a fairly large volume very quickly. This is advantageous for a number or reasons: 1) often the patient can hold their breath for the entire study, reducing motion artifacts, 2) it allows for more optimal use of intravenous contrast enhancement, and 3) the study is quicker than the equivalent conventional CT allowing for higher resolution in the same study time. The data obtained from spiral CT is often perfect for 3D imaging because of the lack of motion mis-registration and the increased out of plane resolution. Scanners capable of spiral CT are usually more expensive and therefore fewer institutions have them.

Medical Imaging Techniques
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