A new algorithm for the quantitation of myocardial perfusion SPECT. I: Technical principles and reproducibility

We have developed a new, completely automatic 3-dimensional software approa ch to quantitative perfusion SPECT. The main features of the software are m yocardial sampling based on an ellipsoid model; use of the entire count pro file between the endocardial and epicardial surfaces; independence of the a lgorithm from myocardial shape, size, and orientation and establishment of a standard 3-dimensional point-to-point correspondence among all sampled my ocardial regions; automatic generation of quantitative measurements and 5-p oint semiquantitative scores for each of 20 myocardial segments and automat ic derivation of summed perfusion scores; and automatic generation of norma l limits for any given patient population on the basis of data fractionally normalized to minimize hot spot artifacts, Methods: The new algorithm was tested on the tomographic images of 420 patients studied with a rest (TI)-T -201 (111-167 MBq, 35 s/projection)stress Tc-99m-sestamibi (925-1480 MBq, 2 5 s/projection) separate dual-isotope protocol on a single-detector camera, a dual-detector 90 degrees camera, and a triple-detector camera. Results: The algorithm was successful in 397 of 420 patients (94.5%) and 816 of 840 image datasets (97.1%), with a statistically significant difference between the success rates of the (TI)-T-201 images (399/420, or 95.0%) and the Tc- 99m images (417/420, or 99.3%; P < 0.001), Algorithm failure was caused by extracardiac uptake (10/24, or 41.7%) or inaccurate identification of the v alve plane because of low count statistics (14/24, or 58.3%) and was obviat ed by simply limiting the image volume in which the software operates. Repr oducibility of measurements of summed perfusion scores (r = 0.999 and 1 for stress and rest, respectively), global defect extent (r = 0.999 and 1 for stress and rest, respectively), and segmental perfusion scores (exact agree ment = 99.9%, kappa = 0.998 for stress and 0.997 for rest) was extremely hi gh. Conclusion: Automatic 3-dimensional quantitation of perfusion from (TI) -T-201 and Tc-99m-sestamibi images is feasible and reproducible. The descri bed software, because it is based on the same sampling scheme used for gate d SPECT analysis, ensures intrinsically perfect registration of quantitativ e perfusion with quantitative regional wall motion and thickening informati on, if gated SPECT is used.