Authors:

B Guzic Salobir¹ , M Stalc¹ , K Senica¹ , M Dolenc Novak¹ , ¹University Medical Centre of Ljubljana, Department for nuclear medicine - Ljubljana - Slovenia ,

Background: Reducing patient radiation exposure has become an important challenge for nuclear cardiology. With the use of solid-state cardiac cameras, the acquisition time for myocardial perfusion imaging (MPI) SPECT has been significantly shortened. This provides an opportunity to lower the injected doses for SPECT MPI.

The purpose of this study was to find out the impact of reduced dose activity on the acquisition time in normally weighted patients undergoing MPI using a solid-state cardiac camera.

Methods: We prospectively evaluated 320 consecutive patients (<100 kg) with suspected or known coronary artery disease referred to our nuclear medicine department for routine MPI. They underwent a 2-day rest and stress imaging on Cardius X-ACT (Digirad), using two different dose protocols. In the "conventional" group, a standard dose of approximately 600 MBq 99mTc tetrofosmin (Myoview, GE Healthcare) was injected each day. In the "reduced" group, 2/3 of conventional dose activity (approximately 400 MBq) was administered each day. The scanning time for the patient was determined by the camera itself according to the preset maximal number of counts. The administered activity, effective dose and the acquisition time were prospectively collected in the Nuclear Cardiology Database.

Results: A total of 320 patients (160 in each group, 43.7% women, mean age 66.5 ± 11.8 years, body weight 80.8 ± 16.2 kg, body mass index 28.7 ± 5.7 kg/m²) were analysed. There were no differences in the body weight and body mass index between the groups. The administered activities and effective doses at rest and stress studies are shown in table 1. The total effective dose for 2-day rest/stress protocol decreased from 9.0 mSv in "conventional" group to 6.0 mSv in "reduced" group. The scanning time per one acquisition lengthened from 7.6±1.5 minutes in "conventional" group to 9.5±2.3 minutes in "reduced" group.

Conclusions: This study demonstrates that with 1/3 effective total dose reduction the imaging time using a solid-state camera is still quick enough to be convenient to the patients and does not reduce the laboratory patient flow, productivity or image quality.