Abstract 3191: Experimental Validation Using Radiolabeled Microspheres of Absolute Quantitation of Regional Myocardial Blood Flow (MBF) Using Dynamic Rb-82 Positron Emission Tomography (PET)
Absolute quantitation of MBF with dynamic Rb-82 PET has great potential in the assessment of the extent and severity of ischemia in patients with suspected coronary artery disease, particularly at centers that lack access to a cyclotron, but requires validation of MBF estimation.
METHODS: In order to validate our automated Rb-82 PET MBF quantitation based on generalized factor and compartment analyses (GFADS), we compared rest/stress regional Rb-82 MBF to reference MBF measured with radiolabeled microspheres (MS) in 6 dogs before and after creation of a critical LAD stenosis. High resolution dynamic Rb-82 PET acquisitions were performed on a Siemens HRRT in 3D listmode at rest and during adenosine stress in conjunction with injection of MS. Studies were rebinned into 24 5-sec, 6 10-sec, and 4 20-sec frames, and reconstructed using OSEM, compensating for scatter, randoms, attenuation and resolution. Hearts were cut into 5 mm slices (8 radial segments per slice). Myocardial segments were re-mapped to match the 17 segments of the standard polar map. Left and right ventricle input functions were automatically computed using GFADS. LV input was validated with on-line measurements of arterial activity. Polar maps of MBF (K1, ml/g/min) and coronary flow reserve (CFR) were computed using a 2-compartment kinetic model yielding 34 segments at rest and stress for each dog, that were remapped into apical, mid and basal ischemic and non-ischemic territories.
RESULTS: MBF (uncorrected by RPP) derived from dynamic PET were in reasonable agreement with MS values at rest: MBF (PET) = 0.38 x MS + 0.39, r= 0.70, and in good agreement with MS values at stress: MBF(PET) = 0.48 x MS + 0.22; r=0.86. Regional CFR derived from dynamic PET was also in good agreement with MS values in the normal LCX territory (PET:1.44Â±0.17 vs MS:1.53Â±0.14) as well as in the LAD territory where a stenosis was created (1.07Â±0.18 vs. 1.17Â±0.16). PET and MS CFR values correlated well over the range of 0.51–2.37: CFR(PET) = 0.796 x MS + 0.421; r=0.940.
CONCLUSION: Absolute quantification of MBF and CFR can be obtained from dynamic rest/stress Rb-82 PET using a fully automated GFADS approach which was validated in experimental animals using MS flow and should permit rapid determination of absolute MBF in patients.