The use of thallium-201 lung/heart ratios.

This survey gives an overview of the methodology of thallium-201 lung/heart uptake ratios often used as an independent factor in the assessment of patients with coronary artery disease undergoing myocardial perfusion scintigraphy. Different techniques have been used in the past. The most sensitive method is one which calculates a lung/heart ratio from scintigraphy obtained immediately after cessation of exercise. If single photon emission tomography (SPET) is routinely performed the anterior projection of the data set obtained during tomographic acquisition should be used in preference to a separate planar anterior static images recorded before or after the SPET procedure. The lung/heart ratio is useful as a prognostic indicator of outcome as it accurately mimics the degree of left ventricular dysfunction. With the increasing popularity of pharmacological stress testing there is evidence that this ratio still offer valid information. Additional work in this field is nevertheless required to further confirm this observation. In routine clinical practice, the lung/heart ratio should help and enable physicians to prioritise patients for urgent intervention.