Comparison of total radiation exposure from 82Rb verses 99mTc-sestamibi MPI

Objectives The intent of this study was to retrospectively determine whether there was a major difference in patient radiation exposure received during a myocardial perfusion imaging (MPI) scan, based on the imaging protocol selected. Saint Joseph’s Hospital has two MPI protocols for patients with a body mass index (BMI) greater than 35 kg/m². The first protocol utilizes ^99mTc-Sestamibi and a SPECT/CT (Siemens Symbia T6) camera, while the second protocol employs ⁸²Rb and a PET/CT (Philips Gemini GXL) system.

Methods Thirty-eight patients, with BMI’s ranging from 24 kg/ m² to 69 kg/ m² who had undergone both a ⁸²Rb MPI scan and a ^99mTc-Sestamibi MPI scan were evaluated. Whole body exposure from ⁸²Rb rest and stress doses (approximately 40 mCi for each dose) were summed and recorded according to the patient’s BMI. The same method was used to sum the ^99mTc-Sestamibi rest and stress doses (approximately a 16 mCi rest dose and a 40 mCi stress dose). The CT radiation exposure was added to the ⁸²Rb and ^99mTc-Sestamibi doses, respectively, and the total radiation exposure of each procedure was compared.

Results This study found that a ⁸²Rb MPI scan gave a 9% higher whole-body dose than a ^99mTc-Sestamibi MPI scan for patients with a BMI less than 48 kg/m². For patients with a BMI of 48 kg/m² or larger, ^99mTc-Sestamibi MPI scan resulted in an average 4% higher total radiation exposure.

Conclusions The total radiation exposure is greater for ⁸²Rb than ^99mTc-Sestamibi myocardial perfusion imaging for patients with BMI’s less than 48 kg/m², however, ^99mTc-Sestamibi delivers a higher exposure for patients with BMI’s equal to or greater than 48 kg/m² due to an increased CT dose during SPECT/CT imaging.