Limitations of Rb-82 weight-adjusted dosing
accuracy at low doses
Jonathan B. Moody, PhD,
Kerri M. Hiller, BS, CNMT, RT(N),
Benjamin C. Lee, PhD,
James R. Corbett, MD,
Edward P. Ficaro, PhD,
and Venkatesh L. Murthy, MD, PhD
INVIA Medical Imaging Solutions, Ann Arbor, MI
Division of Nuclear Medicine, Department of Radiology, University of Michigan, Ann Arbor, MI
Received Dec 18, 2015; accepted Apr 28, 2016
Introduction. Weight-adjusted dosing is important to maintain accurate quantiﬁcation for
dynamic cardiac three-dimensional positron emission tomography (PET). However, the man-
ufacturer of the only Food and Drug Administration approved rubidium-82 (Rb-82) generator
(CardioGen-82, Bracco Diagnostics, Inc.) recommends recalibration after each change in dose
which is inefﬁcient in a busy clinical PET lab. The objective of this study was to evaluate the
accuracy of Rb-82 dosing without this recalibration.
Methods. After daily calibration to either 30 mCi (1110 MBq) or 12 mCi (444 MBq), Rb-
82 doses between 6 and 45 mCi (222-1665 MBq) were eluted and measured on an external dose
calibrator. This was repeated for four generators at weeks 1, 2, or 4 of the generator cycle. The
measurements were compared with values reported by the infusion system.
Results. For requested doses less than 30 mCi, the measured dose was consistently lower
than the requested dose, ranging from 23.2 mCi at 25 mCi to 25.5 mCi at 10 mCi. The error
exceeded 10% for doses less than or equal to 26 mCi for the 30 mCi calibration. Residual
activity in the infusion system dead volume accounted for the discrepancy between requested
and delivered doses for calibration to 30 mCi but not 12 mCi.
Conclusions. The CardioGen-82 infusion system is capable of accurate weight-adjusted
doses without recalibration for Rb-82 doses as low as 26 mCi when calibrated to 30 mCi. For
doses less than 26 mCi, the generator-reported residual activity within the infusion system can
be used to correct the delivered dose. (J Nucl Cardiol 2017;24:1395–401.)
Key Words: Weight-adjusted dosing
Æ cardiac PET Æ rubidium-82
PET Positron emission tomography
FDA Food and Drug Administration
Patient-speciﬁc weight-adjusted dosing of radio-
pharmaceuticals for cardiac positron emission
tomography (PET) is important to avoid detector satu-
ration for dynamic blood ﬂow quantiﬁcation with three-
dimensional (3D) PET systems.
It is also one approach
to reduce radiation exposure from noninvasive cardiac
which has recently been emphasized by
Electronic supplementary material The online version of this
article (doi:10.1007/s12350-016-0531-2) contains supplementary
material, which is available to authorized users.
Reprint requests: Venkatesh L. Murthy, MD, PhD, Division of Nuclear
Medicine, Department of Radiology, University of Michigan, 1338
Cardiovascular Center, 1500 E. Medical Center Dr, SPC 5873, Ann
Arbor, MI 48109-5873; firstname.lastname@example.org
J Nucl Cardiol 2017;24:1395–401.
Copyright Ó 2016 American Society of Nuclear Cardiology.