Organ volume determination by CT scanning: reduction of respiration-induced errors by feedback monitoring

Computed tomography potentially provides an accurate means of determining organ volume, by summation of serial section areas. Variation in level of held respiration for each serial scan, however, severely limits accuracy in the thorax and upper abdomen. A simple strain gauge has been used to provide the patient with visual indication of the level of held respiration, so that biofeedback regulation may be achieved. Change in liver area between nominally identical pairs of images, with and without biofeedback regulation, has been used as an indicator of section reproducibility. Significant improvement in reproducibility was seen for all pairs of images where biofeedback regulation was used, compared with those pairs with conventional breath-holding. Biofeedback regulation has many applications in imaging the thorax and upper abdomen.