Diagnostic value of Tl-201 lung uptake is dependent on measurement method

Background, Increased lung uptake during exercise thallium 201 single photo n emission computed tomography is related to left ventricular dysfunction a nd extent of coronary artery disease (CAD), We studied the influence of the lung region of interest (ROI), used to quantify TI-201 lung uptake, on the diagnostic value of the lung-to-heart uptake ratio(LHR) in detecting CAD w ith TI-201 myocardial single photon emission computed tomography. Methods and Results. We retrospectively studied 152 consecutive patients re ferred to our center for stress TI-201 scanning. Of these, 116 had proven m ultivessel CAD and 36 had either normal findings on coronary angiogram or a low likelihood (<5%) of CAD. Poststress quantitative analysis was performe d from a 4 x 4-pixel ROI over the hottest myocardial region, an 8 x 8-pixel left lung ROI, an 8 x 8-pixel right lung ROI, and a manual ROI encompassin g the whole right lung. The LHR was calculated for each lung ROI, Right LHR (R-LHR) provided the best interobserver and intraobserver reproducibility, R-LHR and total R-LHR values were significantly higher in patients with CA D. Only history of myocardial infarction significantly influenced the R-LHR measurement. Conclusions. The methodology of LHR measurement significantly influences th e clinical contribution of TI-201 lung uptake evaluation. Optimal reproduci bility and diagnostic accuracy are provided by a right lung ROI.