# Thallium Use, Toxicity, and Detoxification Therapy: An Overview
## 7 201 Thallium Sentigraphy  
Myocardial perfusion scintigraphy (MPS) is one of the most used techniques to perform noninvasive cardiac imaging tests in the diagnosis of acute onset chest pain as well as in the evaluation of subjects with coronary artery disease in conditions of exercise stress or pharmacological stress to increase coronary blood flow. An increase in coronary flow can be obtained increasing oxygen demand in healthy coronary dynamics under stress exercise (bicycle or treadmill), with dobutamide (a \(\beta_{1}\)-adrenergic agonist), or by pharmacological vasodilitation with adenosine [62] or pyridamole for patients unable to perform exercise under effort. The clinic protocol involves intravenous injections of small quantities of radioactive compounds at peak stress followed by imaging of its distribution in the heart with a rotating gamma camera. There are three radioactive tracers available: \({}^{201}\)thallium and two \({}^{99m}\)technetin (sestamibi and tetrofosmin). Thallous (201) chloride has been used routinely as a tracer since the 1970s [14, 15]. Single-photon emission computed tomography (SPECT) thallium is used as a screening test for coronary artery disease (CAD) [63] and coronary-to-pulmonary artery fistula (CPAF) [64]. \({}^{201}\)TI has a half-life of 73.1 h and decomposes by electron capture, emitting X-rays (68-80 KeV) and gamma-rays (137-167 KeV). \({}^{201}\)TI is incorporated into the myocytes via the Na\({}^{+}\)/K\({}^{+}\)-ATPase transport system and facilitates diffusion. Imaging of the process starts within 5-10 min after peak stress and injection when the heart is rested. After about 4 h from intravenous injection, there is a redistribution of thallium between the intra- and the extra-cellular spaces in all the myocytes, without considering perfusion [65]. The image soon after the injection is a combination of viability and perfusion, whereas the redistribution image only presents viability. The radiation exposure [100-150 mega Becquerel (MBq)] of \({}^{201}\)TI is high due to its relatively long half-life, and only 4% of the injected solution is absorbed by the myocytes. In addition, its low-energy emission leads to low-resolution images. The half-life of \({}^{99m}\)Tc is 6.00 h; thus, the radiation exposure is much lower than that thallium. In addition, the positive effects of technetium use include better images in obese subjects and women with large breasts. MPS is a good method for imaging the effects of coronary artery disease on the heart during exercise stress and pharmacological stress after an injection of \({}^{201}\)TI and \({}^{99m}\)Tc [66]. Several studies have highlighted the excellent accuracy in the detection of coronary artery disease in subjects with undiagnosed chest pain using the MPS technique [67]. \({}^{201}\)TI scintigraphy, unlike \({}^{99m}\)Tc, is commonly used in clinical oncology as a tool for imaging malignant neoplasms such as sarcoma, lung, and breast cancer [68]. [PERSON] et al. (2008) [69] were able to distinguish a chondromyxoid fibroma (benign bone tumor) from a chondrosarcoma (primary bone sarcoma) in the left knee of an 18-year-old man by using \({}^{201}\)TI scintigraphy and magnetic resonance imaging. In a successive paper, the pigmented villonodular synovitis (tecnosynovial giant cell non-malignant tumor) in the right elbow of an 18-year-old woman was studied [70]. Magnetic resonance imaging revealed an isointense signal of the tumor; the use of \({}^{201}\)TI scintigraphy enabled the highlightingand location of an abnormal accumulation of a cancerous mass in the elbow, which was surgically removed. [PERSON] and coauthors (2015) [71] used 201 Tl scintigraphy to differentiate malignant bone tumors from benign bone tumors. The study involved 279 patients with bone lesions (228 benign and 51 malignant). The authors evaluated 201 Tl intake by studying tumor-to-background contrast (TBC).