Diagnostic tests involving radiation are an invaluable tool to manage many other diseases, including those affecting the lungs (asthma, chronic obstructive pulmonary disease); kidney (stones; pyelonephritis); liver and gallbladder; pancreas; and the lymphatic and musculoskeletal system.
Breast cancer and cutaneous melanoma
For patients with early-stage breast cancer and cutaneous melanoma, radioguided surgery and sentinel lymph node biopsy are now the accepted standard of care.
Breast cancer is the most frequent type of cancer diagnosed in women worldwide. Lymph node status is a major prognostic factor in detecting the disease at an early stage. This information is paramount for tailoring the therapy. Depending on the status of the axilla – the area on the human body directly under the joint where the arm connects to the shoulder – the oncologist will apply different treatment strategies, such as surgery and adjuvant (additional) chemotherapy, radiotherapy and hormone therapy.
Sentinel lymph nodes are those that directly drain the lymph from the primary tumour. Consequently, they are the first lymph nodes to potentially receive metastatic cells. When breast cancer metastasizes to regional lymph nodes, it most frequently goes to the sentinel lymph nodes. If the sentinel lymph node is free from micrometastasis, the probability of detecting tumour cells in non-sentinel lymph nodes is less than five per cent. Lymphoscintigraphy – a novel approach that safely and accurately screens axillary lymph nodes – allows the surgeon to identify and biopsy the sentinel lymph node.
Cutaneous melanoma is potentially the most dangerous form of skin tumour, causing 90 per cent of skin cancer mortality. The incidence of cutaneous melanoma is increasing worldwide among white populations (at a rate of four to eight per cent every year), especially where fair-skinned races receive excessive sun exposure. The principal aim of sentinel lymph node biopsy in patients with cutaneous melanoma is to identify the 20 to 25 per cent of patients who carry a regional disease that cannot be seen in clinical tests (in other words, are clinically occult). The technique increases the detection rate of occult lymph node metastases; identifies patients who may benefit from additional postoperative therapy; and allows dividing members of the population into homogeneous subgroups for randomized clinical trials.
High blood pressure caused by the kidneys' hormonal response, also called renovascular hypertension, accounts for about five per cent of all cases of hypertension among the population. It is the only type of hypertension that can be cured. Correction of this disorder in one kidney leads to a normalization of blood pressure provided the other kidney is functioning normally. This can be determined by a renal radionuclide study.
Diseases of the endocrine system
Several pathologies of the endocrine system can be diagnosed using nuclear medicine studies. The most common of these are benign thyroid diseases, such as hyperthyroisim due to Plummer’s adenoma or Basedow’s disease, and thyroid cancer. In the latter case, nuclear medicine studies are necessary to identify possible thyroid remnants in the neck after surgery of metastatic dissemination. Primary parathyroidism due to adenomas is another indication, as well as pheocromocitomas affecting the adrenal glands.