PT - JOURNAL ARTICLE AU - Tavoosi, Anahita AU - Wells, R. Glenn AU - Merani, Azmina AU - Kimberly, Gardner AU - Ruddy, Terrence AU - Small, Gary AU - Crean, Andrew AU - Chow, Benjamin AU - Beanlands, Rob AU - deKemp, Robert TI - <strong>Exponential Dosing for Consistent Image Quality with Rubidium-82 PET MPI</strong> DP - 2022 Aug 01 TA - Journal of Nuclear Medicine PG - 3337--3337 VI - 63 IP - supplement 2 4099 - http://jnm.snmjournals.org/content/63/supplement_2/3337.short 4100 - http://jnm.snmjournals.org/content/63/supplement_2/3337.full SO - J Nucl Med2022 Aug 01; 63 AB - 3337 Introduction: Myocardial perfusion imaging (MPI) with positron emission tomography (PET) provides high diagnostic and prognostic values for coronary artery disease. Cardiac PET also appears to be a promising non-invasive modality with prognostic value in obese patients. Imaging with PET is susceptible to the patient’s body habitus, as the increase in body weight leads to higher fractions of attenuated and scattered photons resulting in lower quality images. The current guidelines advise a single fixed dose (e.g. 1100 MBq) or a weight-based dose (e.g. 9 MBq/kg) of Rb-82 for PET MPI, which still has the limitation of poor image quality in obese patients. The aim of this study was to investigate whether Rb-82 activity administered as a squared function of patient weight (exponential dosing) can help standardize image quality across a wide range of body sizes.Methods: Fifty consecutive patients who underwent clinically indicated Rb-82 PET myocardial perfusion imaging (MPI) with exponential dosing (0.1 MBq/kg2) were identified as exponential group. These were compared to a weight-matched group of 50 patients who also underwent clinically indicated Rb-82 cardiac PET MPI imaging with linear dosing (9 MBq/kg). ECG-gated and ungated (static) PET images were analyzed at stress from both cohorts referred for Rb-82 MPI on a Siemens Vision600 PET-CT scanner with ≈200 ps time-of-flight (TOF) resolution using TOF-OSEM reconstruction (4 iterations, 5 subsets) and 6 mm Gaussian post-filtering. Myocardium signal recovery was measured as the maximum activity in the left ventricle (LVMAX) at end-diastole. Corresponding background signal and noise were measured as the left atrium blood cavity mean and standard deviation (BLMEAN and BLSD). Myocardium signal-to-noise ratio (SNR = LVMAX / BLSD) and myocardium-to-blood contrast-to-noise ratio (CNR = (LVMAX - BLMEAN) / BLSD) were calculated for both the static and ECG-gated end-diastolic images.Results: The linear and exponential dosing cohorts had the same mean and variance of patient weights as expected (81 ± 18 kg). There was no difference in mean rubidium dose between the two cohorts (728 ± 164 vs 686 ± 308 MBq; p=0.35). The SNR and CNR measurements of image quality (Figure 1) clearly demonstrate better uniformity of image quality in the exponential dosing group. The exponent (Beta) of a power-function fit to the data showed that image quality was no longer a significant function of patient weight (Beta ≈ 0) in the exponential dosing cohort (95% CI including zero) whereas it was in the matched cohort using linear dosing (Beta &lt; 0). Median gated SNR and CNR values were slightly lower on average using exponential vs linear dosing (67 vs 77 and 49 vs 57; both p&lt;0.01) likely due to the non-linear effect of injected activity on image quality as measured over the distribution of patient weights in the comparative cohorts.Conclusions: The findings show a more consistent SNR and CNR across all patient weights for both static and gated images when using exponential dosing compared to linear weight-based dosing. This approach enables better standardization of image quality without increasing radiation dose to the population as a whole.