Thallium-201 lung uptake: comparison of an automatic and a manual method of ROI drawing

An automatic method for ROI drawing to measure 201TI lung uptake after stress testing in planar and tomographic myocardial perfusion imaging, was compared with the more commonly used manual method. A linear correlation in the lung/heart ratio (LHR) and lung washout (LWO) data, obtained in planar and SPECT images with the two methods, was found. Pearson's correlation coefficient between the automatic and manual methods was highly significant both for LHR and for LWO. For LHR we found a high linear correlation between the two methods in the planar anterior (r = 0.71, p < 0.001), SPECT anterior (r = 0.84, p < 0.001), and SPECT LAO (r = 0.96, p < 0.001) views. The analysis of LWO data showed a good linear correlation for the planar anterior (r = 0.84, p < 0.001), SPECT anterior (r = 0.66, p < 0.005) and SPECT LAO (r = 0.79, p < 0.001) views. Furthermore, comparison by the student's t test of the averages of the LHR and LWO values obtained in the same views but with different methods was performed. The advantages and the critical issues associated with the automatic method are discussed; it appears to be quick and easy to perform and to be equivalent to the more time-consuming method based on a manual definition of left lung ROI.