Assessment of vertebral mineral content by means of a single-crystal scintillation camera

Increasing interest in bone mass has led to dedicated commercial dual photon absorptiometry (DPA) instruments. We describe a method for the measurement of the mineral content of the lumbar spine using a scintillation camera. The most appropriate source(s) and collimator were investigated. An especially constructed arm placed the sources in the focal point of a converging collimator. Two single-peak sources, Tc and Am, were used instead of dual-peak Gd source. Phantom studies showed no degradation of the results in water depths of up to 26 cm. Acquiring 10 Mcounts per image over a 300 cm field, a coefficient of variation (c.v.) of 1.7% was obtained. Reducing the total counts per image to 1 Mcount gave rise to a c.v. of 6.2%. Long-term measurements showed a c.v. of 1.1% for density, with a mean value of 0.98 gHa cm compared to 0.90 for a commercial DPA instrument. Repeated measurements of the lumbar spine on 10 patients with a 2 week interval showed a c.v. of 5%. Comparative measurements were made between the scintillation camera and a commercial DPA instrument on six volunteers. Systematic higher results, similar to those observed with the phantom, were obtained with the scintillation camera. The reproducibility on a phantom and in patients is in the same range as commercial DPA instruments. The low cost related to the use of standard nuclear medicine equipment and to inexpensive radioactive sources represent definite advantages.