title: Gamma radiation measurements and Monte Carlo computations following myocardial perfusion imaging with 201Tl.
abstract: In the current study, the time-dependent retention of (201)Tl-thallous chloride (111 MBq) was measured in a 56-y-old man undergoing myocardial perfusion imaging. For 23 d following the (201)Tl injection, total-body retained activity was measured by (i) in situ gamma spectrometry using a portable high-purity germanium (HPGe) detector and (ii) ex vivo urine radioassay using a shielded HPGe detector. The time-dependent decrease in total-body activity followed a monoexponential function, exp(-0.011 t), with an excellent correlation (R(2)=0.9988) between the experimental data and the fitted values. The effective half-life, Teff, of (201)Tl (physical half-life, Tph: 72.9 h) was therefore 63 h and the biological half-life, Tb, 463 h=19.3 d, identical to those measured in the same patient in 1997 (i.e. 14 y ago). The time-dependent decrease in the urine activity concentration, which followed a monoexponential function, exp(-0.0115 t), corroborated the foregoing results. The correlation (R(2)=0.9939) between the experimental data and the fitted values was again excellent. The effective half-life, Teff, was 60.26 h and the biological half-life, Tb, 348 h=14.5 d. Monte Carlo simulation using a simple model of the patient as a unit-density cylinder filled with water and containing a uniform distribution of (201)Tl yielded photon flux results in reasonable agreement with the measured data.
authors.affiliation: Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece. clouvas@eng.auth.gr
authors.forename: A
authors.initials: A
authors.lastname: Clouvas
authors.forename: S
authors.initials: S
authors.lastname: Xanthos
mesh_terms: D001822:Body Burden; D005720:Gamma Rays; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009010:Monte Carlo Method; D055414:Myocardial Perfusion Imaging; D011829:Radiation Dosage; D013793:Thallium / Q000493:pharmacokinetics*; D014915:Whole-Body Counting / Q000379:methods*
chemical_list: C027549:thallium chloride; D013793:Thallium