Dual isotope hybrid SPECT/CT in porcine model of peripheral artery disease

Objectives: The goal was to test hypothesis that dual isotope hybrid SPECT/CT imaging of perfusion with Tl-201 and VEGF expression with ^99mTc scVEGF-PEG-DOTA (scV/Tc) can successfully monitor perfusion and angiogenesis following femoral artery ligation.

Methods: Five Yucatan minipigs underwent dissection and isolation of L external femoral artery (FA) which was clipped and transected. Animals underwent 3 sets of SPECT/CT scans: Tl-201 at day 1 (maximal flow reduction) and day 28 (flow restoration), and scV/Tc imaging targeting VEGF receptors -1 and -2 at day 7 (maximal angiogenesis). Biopsy samples were taken at day 7 for well counting and histology. Following day 28 scan pigs underwent iliofemoral arterial contrast angiography and euthanasia. Both hindlimbs were dissected and sections taken from muscle groups for well counting and histology. Scan data were analyzed with 4 DM software (INVIA solutions, Ann Arbor MI). Counts from ROIs drawn around each hindlimb muscle group on serial transverse sections for both legs were converted to mCi and results expressed as ratios L/R.

Results: Day 1 scans showed reduced perfusion in L hindlimb compared to R with partial restoration by day 28. Focal uptake of scV/Tc just distal to clipped vessels was seen at day 7 as well as collaterals on CT angio and improved perfusion to distal limb on day 28. Scan results summarized in table. Asterisk value: ratio for %ID/g.

Conclusion: These preliminary results suggest that dual isotope hybrid SPECT/CT imaging for perfusion and angiogenesis has potential as clinical imaging modality to assess therapies to improve blood flow in patients with PAD. Supporting Data: Coronal Tl-201 SPECT/CT scans of pig hindlimbs day 1 and 28 on left. Transverse SPECT/CT scan at day 7 showing focal uptake of scV/Tc distal to the ligated femoral artery upper right. Contrast angio of L leg day 28 showing collaterals lower right