Dynamic geometric mean studies using a single headed rotating gamma camera

A technique for acquiring dynamic geometric mean studies utilizing a single-headed rotating gamma camera has been developed. The camera head is repeatedly rotated between opposed views under computer control. A single data set results, from which a dynamic sequence of geometric mean images can be produced. Software has been developed to accomplish data acquisition and the reformatting required. The accuracy of the geometric mean data formed using this technique has been studied experimentally, and compared with results obtained from anterior and posterior sequences. In a simple clearance experiment of a 1-I volume with a known clearance of 20 ml.min-1, the geometric mean data resulted in estimates of volume remaining in the container with a mean error or +2.0 ml (s.d. = 5.7 ml, range -4.5 +/- 15.3 ml), while the anterior and posterior images yielded volume estimates with mean errors of -10.1 ml (s.d. = 16.6 ml, range -47.4 +/- 10.5 ml) and +35.5 ml (s.d. = 22.6 ml, range -3.2 +/- 51.6, ml), respectively. The technique is easy to implement and does not require modification of existing hardware. An application of the technique to a clinical study of gastric emptying is also included.