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Improvement of Algorithm for Quantification of Regional Myocardial Blood Flow Using ¹⁵O-Water with PET

¹ Department of Tracer Kinetics, Hokkaido University School of Medicine, Sapporo, Japan
² Department of Health Science, Hokkaido University School of Medicine, Sapporo, Japan
³ Department of Nuclear Medicine, Hokkaido University School of Medicine, Sapporo, Japan

View larger version (80K): [in a new window]   FIGURE 1. Transaxial 15O-CO images were rotated to generate short axial images in horizontal long axial and in vertical axial slices. Rotation angles for each reorientation were set manually monitoring the rotated images.

View larger version (43K): [in a new window]   FIGURE 2. Positioning of LV ROI on short axial 15O-CO images. When a position in left ventricle is clicked on the image, the LV ROI is set automatically. Program defines mean ROI count yields as 85% of the true blood volume concentration.

View larger version (69K): [in a new window]   FIGURE 3. When 15O-water washout images are superimposed on extravascular images and analyzed with semiautomated edge-detection routine, a whole myocardial ROI is determined. Program extracts 3D region enclosing the whole myocardial wall; process is performed in the 3D matrices. Positioning of whole LV wall ROI on 15O-water washout images is evident. (A) Circles are placed semiautomatically inside and outside myocardial edges. (B) Program defines endocardial and epicardial borders of LV wall (B).

View larger version (27K): [in a new window]   FIGURE 4. Scheme of algorithm of original method (A) and modified method (B). (A) R(t) and LV(t) correspond to measured time–activity curves in regional myocardial ROI and in left ventricle, respectively. Input function Ca(t), tissue time–activity curve Ct(t), and rMBF are derived from R(t) and LV(t). (B) W(t) corresponds to measured time–activity curve in whole myocardial ROI. Uniform input function Cawhole(t) is derived from W(t) and LV(t). Then, each rMBF is estimated using a known input function Cawhole(t) and R(t).

View larger version (91K): [in a new window]   FIGURE 5. Program automatically divides whole myocardial ROI into 16 anatomic segments according to the rule in the American Society of Echocardiography report (14). Quantified rMBF values are presented automatically on polar map (A) and on 15O-water images (B).

View larger version (53K): [in a new window]   FIGURE 6. When paired rest and stress studies are performed, the new program generates automatically polar maps of rest MBF, stress MBF, and coronary flow reserve.

View larger version (48K): [in a new window]   FIGURE 7. Reproducibility of rMBF with original method (A) and modified algorithm (B) in 576 ROIs of 36 subjects. (Top) Regression lines and intervals of SEEs are drawn. Correlation was significantly higher when calculated with modified method than with original method (P < 0.05). (Bottom) Bland–Altman plots.

View larger version (17K): [in a new window]   FIGURE 8. Simulations demonstrate the effect of error in PTF or Va in calculated MBF values. In estimated MBF, fewer errors were induced by errors in PTF or Va with modified method than with original method.