Andrew Van Tosh MD, Abstract Co-Author: Consultant, Pfizer Inc Consultant, Bracco Group Consultant, Cardinal Health, Inc Consultant, Ion Beam Applications, SA

Nathaniel Reichek MD, Abstract Co-Author: Nothing to Disclose

Christopher J. Palestro MD, Abstract Co-Author: Nothing to Disclose

Kenneth Nichols PhD, Presenter: Royalties, Syntermed, Inc Consultant, Gilead Sciences, Inc

Left ventricular (LV) asynchrony can be quantified by both gated blood pool (BP) & myocardial perfusion (MP) tomography. A concern regarding MP phase measurements is their reliance on tracking myocardial walls in cases of severely reduced MP, for which counts are low. PET data are acquired in gated list mode & both BP & MP data are available for the same pts. To test validity of MP phase measurements for severely decreased MP we compared MP to BP phase measurements, which are not affected by decreased MP.

Data were analyzed retrospectively for 67 pts (42 males; 23 females; 71±12 yrs) with suspected heart disease evaluated by 82Rb PET/CT. Data were collected in gated list mode & rebinned into BP tomograms of tracer imaged during the first pass transit through the heart chambers, & separately into MP tomograms of tracer imaged during equilibrium. For BP PET data LV contraction phases were computed for each of 17 LV segments. Excluding the 3 most basal-septal segments to ensure LV cavity sampling the bandwidth (BW) of contraction phases were computed, defined as % of the R-R interval accounting for 95% of LV regional contractions. MP tomograms were analyzed by commercial algorithms, which computed summed rest scores (SRS) indicating severity of MP defects, & MP phase BW derived from phases of maximum count brightness corresponding to regional end-systole at each voxel at locations identified by algorithms as corresponding to the myocardial wall.

37 pts had negligible defects (SRS ≤ 4) with BP phase BW = 16±8%, lower than the 30 pts with significant MP defects (SRS > 4) (33±22%, p = 0.0001). BP & MP phase BW were similar for all pts (24±% versus 26±16%, p = 0.49), pts with SRS ≤ 4 (16±8% versus 19±9%, p = 0.15), & pts with SRS > 4 (33±23% versus 36±19%, p = 0.50). BP & MP phase BW correlated significantly & similarly with SRS (r = 0.59, p < 0.0001 & r = 0.61, p < 0.0001), consistent with greater amounts of asynchrony being related to more severe myocardial damage. Differences between BP & MP phase BW had no correlation to SRS (r = 0.04, p = 0.75). Thus, severe MP defects had no deleterious effect on MP phase quantitation.

Detection of LV asynchrony by phase measurements derived from gated 82Rb PET/CT tomograms are robust & reliable, regardless of severity of MP defects.

It is justifiable to include scintigraphic asynchrony measurements in forming clinical impressions for pts exhibiting severe MP defects.

Van Tosh, A, Reichek, N, Palestro, C, Nichols, K, Validity of Myocardial Perfusion Asynchrony Measurements.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13012329.html