THE DIFFERENTIAL-DIAGNOSIS OF BENIGN AND MALIGNANT BONY LESIONS IN BONE SCANNING - USING THE RATIO OF RADIOUPTAKE AT DIFFERENT TIMES

For the evaluation of bony metastases in cancer patients, bone scanning has become an important tool, but some limitations exist. One of these is the differential diagnosis of benign and malignant bony lesions, in which bone scanning shows one or more lesions in the spine. To help solve this, bone scintigraphy was performed 4 and 24 hours after intravenous injection of Tc-99m MDP; the ratio of radiouptake in the lesion and normal spine was measured as 24-hr/4-hr (T/F) ratio. Fifty-four patients with an average age of 56 years were studied and divided into two groups. Group A included 34 patients (17 women and 17 men) with bony metastases. Group B included 20 patients (8 women and 12 men) with radiographically proven benign bony lesions and no evidence of cancer. An LFOV Elscint Apex 400 digital gamma camera and an Informatek Simis 5 nuclear minicomputer were used. The results showed that the T/F ratio of Group A was 1.3 ± 0.15 (mean ± SD) and that of Group B was 1.0 ± 0.12 (mean ± SD). The P value was less than 0.001. We conclude that the ratio of radiouptake of lesions and normal spine at 24 and 4 hours may be a reliable method of differentiating benign bony lesions from malignant lesions.