Split dose bone scanning

Hundred patients with neoplasms of the breast (n=74), prostate (n=11), lung (n=9) and the female genital tract (n=6) underwent bone scintigraphy according to a split dose protocol. An initial dose of 550 MBq of Tc99m methylene diphosphonate was used and images were taken at 3 hours. The scans were analyzed qualitatively by three observers and quantitatively by a simple transmission densitometer. With this protocol more lesions were detected at 24 hours (n=148) than at 3 hours (n=136). The confidence level of reporting also increased. Quantification analysis showed that in patients of breast cancer with metastates (n=42), there was decrease in soft tissue, kidney and rib uptake at 24 hours. Significant improvement was also seen in lesion to soft tissue ratio and lesion contrast. In patients of breast cancer without observed metastates (n=32), the decrease in the soft tissue uptake was less significant. However, the vertebral uptake was higher at 24 hours. Patients with other types of neoplasms showed similar trends. It is concluded that the split dose protocol leads to clinically significant improvement in the detection of skeletal metastases and should be utilized in situations where it could have a bearing on staging and sub- sequent management. (author)