Assessment of resting myocardial blood flow in regions of known transmural scar to confirm accuracy and precision of 3D cardiac positron emission tomography

Figures

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  Fig. 1. Range of resting myocardial blood flow in regions of transmural scar. The range of resting myocardial blood flow in regions of transmural scar is narrow and constrained between ~ 0.20 and 0.39 mL/min/g with a mean of ~ 0.30 mL/min/g. rMBF in non-transmural scar and normal tissue is greater and with a wider range. Thus, transmural scar can be used as a reference “truth” to assess accuracy of quantitative software packages and/or PET systems

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  Fig. 2. PET imaging protocol. Subjects received 3 consecutive resting 82Rb scans using 2 distinct infusion profiles

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  Fig. 3. An example of the methodology in a large severe inferior transmural scar. A Quality assurance was checked using visual assessment of time activity curves and two automated algorithms. Motion correction was performed as needed. B A ROI was placed around the severe defect on relative images with the resultant size, RU% and average rMBF displayed. This ROI was defined as “ROI-Scar”. C Segmental analysis of the 17-segment polar maps from all SWP. Scar was defined as contiguous segments within the perfusion defect that comprised > 50% of the segment with a segmental summed rest score ≥ 2 and %RU < 65% in all four SWP. These segments are in white font and their average was defined as “Seg-Scar”. Contiguous segments involving the scar but not meeting the noted requirements were averaged and defined as “Seg-Border” (turquoise font). The remaining normal segments (various colors) were averaged and defined as “Seg-Norm”. D Comparisons of rMBF between ROI-Scar and Seg-Scar in various SWP

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  Fig. 4. Accuracy of resting MBF of transmural scar per software package. The green center represents the expected rMBF of transmural scar (< 0.39 mL/min/g for ROI analyses). The layered concentric circles outside the green center represent higher rMBF. The blue concentric circle immediately outside the green circle is for segmental analyses limited by the upper bounds of 0.44 mL/min/g. For each software package, the computed rMBF for infarcts from all 60 resting scans are displayed as round dots. All values are in mL/min/g

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  Fig. 5. Comparison of HeartSee ROI-Scar versus Seg scar

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  Fig. 6. Resting MBF in transmural scar by software package. All analyses are segmental apart from HS-ROI. HS = HeartSee, 4DM-FDV = 4DM with fixed distribution volume, Emory-V = Emory Votaw model, Emory-O = Emory Ottawa model

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  Fig. 7. Minimum resting MBF within transmural scar by software package

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  Fig. 8. Segmental resting MBF of normal myocardium surrounding transmural scar by software package

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  Fig. 9. Whole heart resting MBF of patients with transmural scar by software package

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  Fig. 10. Comparison of resting MBF in 4DM versus 4DM-FDV. rMBF (mL/min/g) in the infarcted segments (white values) is 0.50 versus 0.30, respectively. This fact confirms accuracy within the infarcted segments with 4DM-FDV. However, outside of the infarcted segments, most rMBF are higher in the FDV model. The orange segments represent rMBF that are unrealistic in the 4DM-FDV model

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  Fig. 11. Inaccurate boundary selection. Due to the absence of myocardial uptake and LV aneurysmal segments within the transmural scar, the software package inaccurately identified myocardial boundaries, an error which could not be remedied manually with standard tools within the SWP. This erroneous boundary detection led to a “spillover effect,” yielding falsely elevated MBF values in the scar. Bottom left corner is an echocardiogram with the LV aneurysm outlined in pink