Inter-Observer Reliability in Myocardial Blood Flow Meas-urement using Rb-82-PET/CT

Background/Objectives: Myocardial perfusion PET/CT e.g. using Rb-82 enables the measurement of absolute myocardial blood flow (MBF) and hence the blood-flow-reserve which plays a crucial role in the diagnosis of coronary artery disease. However, the val-ues might depend on the observer’s analysis and thus on the observer’s experience. We investigated the inter-observer reliability of MBF measurements in Rb-82-PET/CT. Methods: 30 consecutive patients who underwent Rb-82-PET/CT for suspected myocardial is-chemia were analysed. Stress conditions were simulated using 400 µg Regadenoson. MBF was measured using Corridor 4DM software. Myocardial flow-reserve (MFR) is the ratio of absolute flow measurements under stress and rest conditions. Four different phy-sicians with different levels of experience (two senior physicians and 2 residents) meas-ured the MBF. The experience of the residents was 1 year and no previous experience re-spectively. Intraclass correlation coefficients (ICC) were calculated for MBF and MFR in the three main vascular territories as well as in the whole left ventricle. Additionally the left ventricular ejection fraction (EF) was determined. Results: The evaluation of MBF showed an excellent correlation between all observes indicated by a low in-ter-observer-variability. Comparing the two different levels of experience, senior physi-cians showed an even slightly higher accordance in MBF-assessment (ICC ranging from 0.9 to 0.98) than residents (ICC ranging from 0.86 to 0.94). The MFR-calculations showed a slightly lower reliability due to the accumulation of variability in rest and stress meas-urements (ICC between 0.78 and 0.81), still indicating a good reliability. EF-calculations also showed a good reliability among different observers (ICC 0.83). Conclusion: Meas-urement of MBF, MFR and EF in Rb-82-PET/CT is highly robust with a very low in-ter-observer variability. A slightly higher inter-observer reliability was found for more experienced physicians.