Serial Non-Invasive Targeted Imaging of Peripheral Angiogenesis: Validation and application of a semi-automated quantitative approach

摘要

Previous studies by our group have demonstrated the feasibility of non-invasive imaging of αv integrin to assess temporal and spatial changes in peripheral and myocardial angiogenesis. In this study we validate the reproducibility, accuracy, and applicability of a new semi-automated non-invasive approach for serial quantitative evaluation of targeted microSPECT-CT images of peripheral angiogenesis in wild-type and eNOS-deficient mice subjected to hindlimb ischemia.MethodsMice (n=15) underwent surgical ligation of the right femoral artery to induce unilateral hindlimb ischemia. One week post ligation, a ^99mTc-labeled cyclic-RGD peptide targeted at αv integrin (NC100692, n=10) or a ^99mTc-labeled negative control (AH-111744, n=5) was injected and 60-min later in vivo microSPECT-CT images were acquired. Mice were euthanized, tissue from proximal and distal hindlimb was excised for gamma well counting (GWC) of radiotracer activity, and ischemic-to-nonischemic (I/N) ratio calculated. MicroSPECT-CT images were analyzed using a new semi-automated approach which applies complex VOIs derived from segmentation of the microCT onto microSPECT images to calculate I/N activity ratios for the proximal and distal hindlimb. Studies were reprocessed for determination of intra- and inter-observer variability.To compare 3D VOI analysis with traditional manual 2D ROI analysis of maximium intensity projection images, microSPECT images were summed onto a single anterior-posterior projection. Rectangular ROIs were manually drawn and I/N ratio calculated.Our new 3D analysis approach was applied to additional groups of mice (eNOS-/-, n=5; wild-type, n=3) imaged before, 1 and 4 weeks after femoral artery resection.