Discussion
A. Role of bone scintigraphy as a first-line study
After the administration of radiopharmaceuticals, tracers travel through bloodstream and reach their own target organs by the guidance of tagging material. When they arrive at their target organs, the uptake mechanism of tracers would be undertaken so the target tissues can be imaged. Their functions can be visualized, as abnormal uptake patterns may be demonstrated in abnormally functioning tissues. Such functional study of tissues provided is a major benefit of bone scintigraphy. It allows the early detection of metastatic diseases because morphological appearance may not be changed in early stage even though the functions have already been altered [5]. Hence, early diagnosis and treatment can be provided, thereby improving prognosis.
Adding to that, since the sensitivity of bone scintigraphy is governed by the level of osteoblastic activities, osteoblastic metastases may show a higher uptake of tracers and appear “hot”; whereas osteoclastic metastases may demonstrate a lower uptake of tracers and appear “cold”. Based on the uptake pattern of different metastases, the primary tumor of these metastases can be deduced. For instance, osteoblastic lesions are frequently observed in prostrate and breast cancer, while osteoclastic lesions are
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To illustrate, patients with MR unsafe metallic implants cannot undergo a MRI scan. Claustrophobic patients may need to be sedated before the examination due to the narrow bore of MRI scanners. If a whole body scan is required, the examination time will be very long, which may not be applicable for pediatric patients. Besides, MRI is insensitive to calcifications or even gross ossification. It is, therefore, difficult to evaluate some suspicious mineralized tumors, cortical bone erosion and bone formation [16], which may then be referred to have a CT scan or bone scintigraphy