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Lymphoscintigraphy plays an important role in the evaluation of lymphedema and several types of tumors, primarily melanoma and breast cancer. Confirmation of a lymphatic etiology for extremity swelling, along with localization of sites of lymphatic obstruction and leakage, can be achieved with lymphoscintigraphy. Its utilization to detect the sentinel node in melanoma patients is well established, while controversy still exists regarding its similar use in patients with breast cancer. In general, isolated removal of the sentinel node is a simpler, more limited surgical procedure that can be performed on an outpatient basis with the patient under local anesthesia and with far fewer complications than more extensive lymph node dissections.

To understand the various scintigraphic patterns of parathyroid disease, it is important to understand parathyroid embryology and anatomy. Although experienced neck surgeons can achieve a high success rate of parathyroidectomy after bilateral neck exploration without prior localizing study [2, 3], a preoperative localization study would decrease operative time and morbidity and is frequently needed for the minimally invasive surgical approach that is currently practiced with increasing frequency. The most commonly used and most cost effective modality for preoperative localization is Tc-sestamibi and alternatively Tc-Myoview. The technique is being used before the initial surgery but is most clearly indicated for the preoperative evaluation of recurrent or persistent hyperparathyroidism. SPECT and particularly pinhole acquisition are valuable to improve the accuracy of localization. Intraoperative gamma probe localization is increasingly used also along with the minimally invasive surgical approach. The spectrum of parathyroid disease demonstrated with Tc-sestamibi scintigraphy includes eutopic disease, ectopic disease, solitary adenoma, double or multiple adenomas, cystic adenoma, lipoadenoma, multiple endocrine neoplasia, hyperfunctioning parathyroid transplant and others. The diagnosis of parathyroid tumors with Tc-sestamibi scintigraphy is based on the difference in clearance rates between the thyroid and diseased parathyroid glands, and any condition that interferes with radiotracer clearance will limit the effectiveness of the study. Atypical washout is one of the known entities that can limit the accuracy of these stuidies and it is probably related to the mitochondrial contents of the cells of the abnormal glands. Adding thyroid scan and ultrasonography improves results but is not cost effective enough to be a routine practice.

Subtraction Tc-sestamibi, iodine-123 scintigraphy or more recently PET may be helpful in difficult cases.

Several biological effects can result from ionizing radiation. These can be due to direct or indirect mechanisms, and they can be acute or delayed. Acute effects occur with exposure to high-level radiation. Delayed effects may appear after a long time and include cancer, genetic effects, effects on the unborn child, and other effects such as cataracts and hypothyroidism. Based on our current knowledge, no level of exposure to radiation can be described as absolutely safe and no level is uniformly dangerous. Radiation doses have to reach a certain level to produce acute injury but not to cause cancer or genetic damage. No biological effects in individuals have ever been documented as being due to levels of ionizing radiation employed for medical diagnosis. Absorbed doses from nuclear medicine procedures are very low. Fear of radiation must not be permitted to undermine the great value of radiation in clinical practice. However, safe handling of all levels of radiation is important to prevent or minimize possible biological effects.