Quantitative sacro-iliac scintigraphy. I. Methodological aspects.

Methodological aspects of quantitative sacroiliac scintigraphy (QSS) using [99mmTc]methylene diphosphonate (MDP) were studied. To improve the diagnostic value of QSS it is important to understand the errors involved in the calculated indices. The accumulated radioactivity in the sacro-iliac joint, compared with that in the sacral bone (SI ratio), decreased linearly with age, by about 24% from the age of 15 years to 71 years. The post-injection time of scintigraphy was not critical, if the scintigraphy was carried out after 2.5 hours. Although the variances of the SI ratios in our control material were relatively high, the repeatability of the SI ratio measurement was 3.9%. The influence of measuring geometry on the QSS and the acceptability of the sacrum as the reference area were tested.