Optimization of Image Quality for Myocardial Perfusion Imaging With Rubidium-82 PET in Patients With Known or Suspected Ischemic Heart Disease (RUBY-DOSE)

Background Selection of the appropriate administered activity for each patient's body habitus is very important to obtain diagnostic image quality. Current SPECT imaging guidelines suggest "…an effort to tailor the administered activity to the patient's habitus and imaging equipment should be made… [however] strong evidence supporting one particular weight-based dosing scheme does not exist." [Henzlova JNC 2016]. An increase in body weight leads to higher fractions of attenuated and scattered photons, resulting in lower quality PET images for a given injected activity [Cherry 2004, Ghanem JNMT 2011]. Weight-based tracer dosing is commonly recommended as a solution in whole-body PET imaging with F-18-FDG [Masuda JNM 2009, Boellaard EJNMMI 2010]. In contrast, Rb-82 PET imaging has traditionally been performed using a single dose (e.g. 40 mCi) administered for all patients [Tout NMC 2012] but this is known to result in lower count-density and image quality in larger patients. This effect can be mitigated to some degree by administration of Rb-82 activity as a proportion of body weight while maintaining accuracy for the detection of disease [Kaster JNC 2012].

The most recent European Association of Nuclear Medicine (EANM) guidelines recommend Rb-82 dosing for 3D PET imaging at 10 MBq/kg [Sciagrà EJNMMI 2020] although the American Society of Nuclear Cardiology (ASNC) still accepts the use of a single dose ranging from 740 to 1110 MBq (20-40 mCi) depending on the PET-CT device sensitivity [Dilsizian JNC 2016]. The ASNC lower limit of 740 MBq may not allow adequate dose reduction in very small or pediatric patients, and conversely the upper limit of 1480 MBq may not allow adequate image quality in the largest patients. For whole body FDG PET, weight-based dosing as a linear function of patient weight (MBq/kg) still does not result in uniform image quality across all patients [Nagaki JNMT 2011]. Recent oncology PET studies have suggested the dose of F-18-FDG be administered as a quadratic function of weight [de Groot EJNMMI Res 2013] and demonstrated that uniform quality of PET images can be maintained across a wide range of patient weights [Musarudin IJNM 2019].

Our center has for many years used weight-based dosing as a linear function of body weight (9-10 MBq/kg) to reduce variations of image quality depending on body habitus, and to reduce detector saturation during the tracer first-pass for accurate blood flow quantification [Renaud JNM 2017a]. Despite this approach, larger patients still suffer from reduced counts and image quality [Renaud JNM 2017b].

Objective To determine whether Rb-82 activity administered as a squared function of patient weight (quadratic dosing) can standardize PET myocardial perfusion image quality over a wide range of body weights.

Primary Hypothesis