34 Part I Chapter 2 Common clinical indications for bone scan The indications for bone scintigraphy are numerous and can generally be classified into three distinct clinical scenarios: a) when a specific bone disease is present or suspected, b) to explore unexplained symptoms, or c) for the metabolic assessment prior to the start of therapy. While the diagnostic sensitivity of bone scintigraphy is very high, the low specificity often requires further investigation with other imaging modalities (like X-ray, CT or MRI) or nuclear medicine studies (e.g. FDG-PET/CT). For this reason, anatomical imaging and bone scintigraphy should be considered as complementary methods, which cannot be replaced by each other. Conversely, bone scintigraphy is not indicated in a number of specific conditions, due to limitations of the technique in a specific disease context or lack of clinical impact of imaging results. However, ultimately it must be the Nuclear Medicine physician who evaluates and decides on the indication of each particular case and on the specific protocol that should be applied. Both indications and non-recommended indications are outlined below: Bone scan is indicated in case bone disease is present or suspected 1. Oncology • Solid tumours with high affinity for bone, including prostate-, breast-, lung-, renal cancer [12-17]. • Malignant hematological conditions limited to bone, including Hodgkin’s disease, non-Hodgkin lymphoma [18]. • Bone tumours and bone dysplasia, including osteosarcoma, osteoid osteoma, osteoblastoma, fibrous dysplasia, giant cell tumor, osteopoikilosis [19]. • Soft tissue sarcomas, such as rhabdomyosarcoma. • Paraneoplastic syndromes, including hypertrophic pulmonary osteoarthropathy, algodystrophy, polymyalgia rheumatica, poly(dermato)myositis, and osteomalacia. • Assessment of bone remodeling prior to radionuclide therapy (223Ra, 89Sr, 153Sm-EDTMP, 186Re-HEDP). Whole-body FDG-PET or PET/CT are other imaging modalities that enable detection of the primary tumour and metastases by visualisation of the increased glucose consumption of malignant tissue. The majority of studies comparing FDG-PET with 18F-Fluoride PET or SPECT with Technetium-99m labelled bisphosphonates reported a higher diagnostic sensitivity of FDG for osteolytic metastases and a higher diagnostic sensitivity of bone-affine radiotracers for detecting osteoblastic metastases [20-24].