Dose Optimization for Rubidium PET Imaging in Patients With Known or Suspected Ischemic Heart Disease

Condition(s) studied

Investigational drug(s) / intervention(s)

Rb-82 Radioisotope: Quadratic dosing: Rubidium-82 activity prescribed as a squared function of body-weight instead of linear function of body-weight or fixed activity independent of body-weight

Study summary

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." 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. Weight-based tracer dosing is commonly recommended as a solution in whole-body PET imaging with F-18-FDG. In contrast, Rb-82 PET imaging has traditionally been performed using a single dose (e.g. 40 mCi) administered for all patients 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.

The objective of this project is 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.

Sequential patients referred for dipyridamole stress Rb-82 PET perfusion imaging at the University of Ottawa Heart Institute. Patients will be divided into 4 weight groups to determine if there are significance differences in image quality or accuracy of injected Rb-82 activity between patients.

Twelve (12) patients will be recruited in each of the 4 weight groups (3 in each 10 kg interval) to uniformly sample the full range of patient weights from 30 to 190 kg. Based on the previous oncology PET literature image quality is not expected to change as a function of weight, i.e. SNR and CNR will be proportional to weight0 (no weight-dependence) with quadratic dosing of Rb-82. Two operators will perform the PET image analysis as described above.

Eligibility

Primary outcome measure(s)

• Rubidium PET image quality — During the participant scan
  Stress gated signal-to-noise ratio measured in the left ventricle myocardium and blood cavity

Trial sites (1)

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