Absolute Quantification of Regional Myocardial Uptake of 99mTc-Sestamibi with SPECT: Experimental Validation in a Porcine Model

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Absolute Quantification of Regional Myocardial Uptake of ^99mTc-Sestamibi with SPECT: Experimental Validation in a Porcine Model

Angela J. Da Silva, H. Roger Tang, Kenneth H. Wong, Max C. Wu, Michael W. Dae and Bruce H. Hasegawa

Department of Radiology and Cardiovascular Research Institute, University of California at San Francisco, San Francisco; and Joint Bioengineering Graduate Group, University of California at San Francisco and Berkeley, San Francisco and Berkeley, California

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FIGURE 1. Schematic bull’s eye plot indicates numbering sequence used to identify various myocardial segments. When apical slice was left intact, it would be numbered segment 4 and remaining segments would be numbered as shown.

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FIGURE 2. (A) Axial slice from one CT image of normal pig shown with endocardial and epicardial borders drawn. (B) Myocardial region of interest, or template, derived from CT image. Each pixel in template is assigned value of 1 to represent uniform activity concentration distribution over extent of myocardium. (C) Reconstructed template image obtained after mathematically modeling SPECT acquisition process. (D) Corresponding ^99mTc-sestamibi image.

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FIGURE 3. (A) Axial slice from one CT image of pig with surgically induced LAD coronary artery occlusion shown with endocardial and epicardial borders drawn. Cross section through ventilation tube is visible in lower left corner of CT image. (B) Myocardial region of interest, or template, derived from CT image. (C) Reconstructed template image obtained after mathematically modeling SPECT acquisition process. (D) Corresponding ^99mTc-sestamibi image shows severe anteroseptal perfusion defect.

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FIGURE 4. Integral counts in myocardial region of interest (ROI) from planar images obtained at various times throughout imaging study. Dotted vertical line represents time of cardiac arrest. Solid curve is fit to data obtained while animal was alive, assuming both physical decay and biologic washout (Eq. 1). Dashed curve represents physical decay only, expected after animal is dead.

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FIGURE 5. Ex vivo activity concentration measured in each myocardial segment of one control animal (normal myocardial blood flow). Refer to Figure 1 for physical location of myocardial segments.

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FIGURE 6. In vivo vs. ex vivo activity concentration measurement for eight pigs included in study. ${circ}$ = activity concentration measured in every myocardial segment with only attenuation correction applied. Dashed line is least-squares linear fit to data with slope of 0.421 and offset of 7.09 kBq/g (r = 0.821). ${blacksquare}$ = activity concentration measured in every myocardial segment with both attenuation and partial-volume corrections applied. Solid line is least-squares linear fit to data with slope of 0.901 and offset of 11.17 kBq/g (r = 0.863).

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FIGURE 7. SPECT quantification obtained from postmortem images vs. ex vivo activity concentration for eight pigs included in study. ${circ}$ = activity concentration measured in every myocardial segment with only attenuation correction applied. Dashed line is least-squares linear fit to data with slope of 0.402 and offset of 7.53 kBq/g (r = 0.776). ${blacksquare}$ = activity concentration measured in every myocardial segment with both attenuation and partial-volume corrections applied. Solid line is least-squares linear fit to data with slope of 0.877 and offset of 16.72 kBq/g (r = 0.876).