Abstract
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Objectives In this work we analyzed data from ammonia PET studies using four different commercial software validated for gated SPECT images: Myometrix (MYO), QGS, Emory Cardiac Toolbox (ECT), CardIQ Physio (CIQP).
Methods 28 pts with different pathologies underwent rest and vasodilatatory stress study by using 13NH3 and 3D-PET. The acquisition protocol was: injection of 370 MBq of 13NH3 and a 3D-PET list mode scan (20 min). PET data (last 15 min) were processed into 12 cardiac gates and reconstructed with a 3D-OSEM algorithm also accounting for TOF and PSF. PET images were analyzed with the four software. Paired t-test was used to assess differences in the results. Rest and Stress were analyzed separately as well as altogether to increase statistical power. Comparisons are reported for end-diastolic volumes(EDV) and ejection fractions(EF). To assess inter-program variabilities we computed coefficients of variations(CV) and standard deviations (SD) of paired comparison.
Results Mean EDV[Rest/Stress] for MYO were:129/132ml,ECT: 112/115ml,QGS:111/116ml, CIQP 137/141ml. Mean EF were[Rest/Stress]:58/60%,64/65%,51/56% and 55/55%. The paired comparisons between software are reported as: MYO vs ECT, MYO vs QGS, QGS vs ECT, MYO vs CIQP, ECT vs CIQP and QGS vs CIQP. The mean differences in EDV were: 14%±1%,14.5%±1%,0.3%±1%,- 8%±1%,- 22%±1%,- 22%±1%.The CV were:6.8%,6.0%,6.6%,5.8%, 7.7%,7.0%.The EF mean differences(absolute differences of the EF)were:-5.7%±1%,,5.5%±1%,11%±1%,4.4%±0.5%,10%±1%,-1%±1%. The CV between the programs were: 6.0%,6.0%,6.0%,4.5%,6.5%,6.7%.
Conclusions The inter-software variabilities has been assessed and were found to be limited to about 7% for EDV and 6% for the EF. Given the high mean differences seen between the software care should be taken when comparing results to normalcy limits.