Abstract 18016: Comparison of a Lower-Dosimetry 3D Rb-82 PET Myocardial Perfusion Imaging Protocol Versus the Conventional 2D Protocol

Abstract

Background: Lowering the infusion dose of Rb-82 offers reduced radiation exposure and extends generator life. We therefore compared 3D PET after a lower Rb-82 dose (∼20 mCi) processed using a Monte-Carlo driven scatter correction algorithm against conventional higher dosage (∼50 mCi) 2D Rb-82 PET MPI.

Methods: We tested 19 subjects, mean age 65 years, mean BMI 30 kg/m², 79% male. Rest/stress scans were acquired on a Siemens Accel™ PET scanner in 2D (septa extended) and 3D (septa retracted) modes. Rb-82 doses were rest 53+/-5 mCi and stress 53+/-6 mCi. Imaging times were 2D emission scan for 5 mins (90 sec delay post Rb-82 infusion), followed by a 3 minute, 3D gated emission scan (180 sec delay post infusion). Decay and shorter acquisition times led to a 62% reduction in the effective dosage 2D vs 3D datasets. 3D images were first pre-processed using a Monte-Carlo scatter and prompt gamma correction algorithm (Imagen3D™) then reconstructed using ImagenPro^TM (CVIT, Kansas City, MO). Reconstructed images were evaluated using relative, 17 segment raw scores (Cedars QPET). Studies were read by consensus of 2-blinded readers for: image quality (1-4, poor-excellent), interpretive certainty (1-3, low-high) and rest perfusion using a 17 segment model (0=normal; 1-3 = mild, moderate, or severe perfusion defects). Stress segmental scores were not evaluated due to differences in imaging start time post dipyridamole infusion.

Results: The standard deviation of raw score differences was 6.5% by QPET and only 2.8% of all segments had a raw scoredifference of >15%. By visual analysis, 99% of all rest segments and 88% of all abnormal rest segments were within 1 point. Other visual parameters:

Conclusion: 3D Rb-82 PET using this method of scatter and prompt gamma correction using 60% less dosage, produces equivalent interpretive certainty, image quality and perfusion defect assessment both visual and quantitative when compared to 2D PET.