Abnormally high diffuse activity on bone scintigram the importance of exposure time for its recognition

Abstract

When the bone scintigram reveals high diffuse skeletal activity, it may be misinterpreted as normal. Some authors have reported such scintigrams in articles entitled "Significance of absent or faint kidney sign on bone scan" and "False negative bone scintigram". Three cases with bone metastasis showing high diffuse skeletal activity are presented in this paper. The recognition of abnormally high diffuse skeletal activity on bone scintigrams is discussed. The exposure time of all three cases was short when compared with normal cases, when the bone image was taken with a preset count. Therefore, exposure time is very important for objective differentiation between the cases showing high diffuse skeletal activity and normal cases.

Technical note: identifying the prostate cancer ‘superscan’ by quantitative skeletal scintigraphy

“…Using the 12th thoracic vertebra to soft tissue ratio they were able to distinguish superscan patients from other groups. Characteristically shortened imaging time was reported by Fukuda et al in such patients [8], and this gave good objective differentiation between superscan and normal images. Since 1992, this centre has quantified individual spot images by recording the time to acquire a fixed count of 600 K (Hawkins and Baldwin, unpublished).…”

“…That descriptive term in prostate, breast and lung metastases was followed by numerous publications describing superscan appearances in other clinical aetiologies -renal osteodystrophy [4], multiple myeloma [5], metabolic bone disease and lymphoma [6], gastric cancer [8] renal tubular acidosis [12], nasopharangeal carcinoma [13] and hyperparathyroidism [14]. The superscan findings are more frequently correlated with prostate cancer than with other conditions.…”

“…Their estimates suggested that 85% of the injected activity appeared in bone compared with 40% in normal individuals. In three reported cases of highly diffuse skeletal activity, all presented as shortened exposure times that afforded sensitive and objective differentiation from normal cases [8]. At the time of single-head cameras and spot images, the index of uptake in this centre was taken simply from the time to acquire a fixed count for each of several images.…”