Patient Couch

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<img align="bottom" alt="Patient Couch - wikiRadiography" height="255" src="$Xv1FY69w==83465/GW340H255" title="Patient Couch - wikiRadiography" width="340"/>

  1. CT gantry
  2. couch top
  3. couch pedestal
  4. couch control pedals (up/down & in/out)
  5. velcro patient immobilisation strap

The patient lies on the couch (also known as a table) and is moved through the CT gantry aperture during the CT examination. Depending on the body part to be scanned and the protocol selected the patient may be positioned supine or prone and either head or feet first. A weight limit for the couch of approximately 205kg (450lb) is specified by the manufacturer beyond which the movement of the table is not guaranteed to be accurate and may even result in damage.

The couch top is usually made of carbon fibre due to its strength and low x-ray attenuation properties. A thin radiolucent mattress and a pillow are placed on the couch top to increase patient comfort. Detachable velcoro straps can be used to help immobilise and secure an active patient. The couch top must be capable of moving at least 1800mm to allow the patient to be scanned from 'head-to-toe' without having to be repositioned.

The couch pedestal (or base) houses the electronic and mechanical components that allow the couch to move in both the horizontal (longitudinal) and vertical direction . The pedestal allows the height of the table to be altered in the vertical direction to make it easier for patients with varying levels of mobility to access it. The foot pedals offer an alternate to using the controls on the CT gantry to move the couch up/down and in/out. The couch can also be moved remotely by the CT operator from the control console.

During conventional slice-by-slice scanning the couch is indexed (moved) between each scan depending on the slice thickness and slice incrementation (degree of overlap or separation) that has been selected for that examination. For spiral/helical CT, including multislice CT, the couch is translated through the gantry at a constant speed depending on the length of the area to be scanned, the total scan time, and the pitch that has been selected.