1. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology Dose Reduction in Half-Time Myocardial Perfusion SPECT-CT with Multi-Focal Collimation Morgan C. Lyon, MS 1,2 Courtney Foster, MS 1, Xinhong Ding 3, Sharmila Dorbala, MD 1,2, Don Spence 3, Manojeet Bhattacharya, PhD 3, A. Hans Vija, PhD 3, Marcelo F. DiCarli, MD 1,2 and Stephen C. Moore, PhD 1,2. 1 Brigham and Women’s Hospital, Dpt. of Radiology, Div. of Nuclear Medicine, Boston, MA 2 Harvard Medical School, Dpt. of Radiology, Boston, MA 3 Molecular Imaging, Siemens Medical Solutions USA, Inc., Hoffman Estates, IL Copyright American Society of Nuclear Cardiology

2. BACKGROUND 1- Recent technological advances in myocardial perfusion imaging (MPI) may warrant use of lower injected activity. 2- It has been shown in phantom experiments that multifocal collimators with an iterative reconstruction package (IQSPECT) may allow for significant reductions in patient dose or scan time due to the increased count sensitivity. 3- We hypothesized that half-time and half-dose myocardial perfusion imaging acquired with IQSPECT would be quantitatively equivalent to full-dose myocardial perfusion imaging acquired with Low Energy High Resolution (LEHR) collimators. Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology

3. METHODS A.Study type: Prospective B.Study subjects: 93 patients referred for clinically indicated Tc-99m sestamibi MPI. C.Study comparisons A.Full-dose/full-time LEHR with Flash 3D reconstruction B.IQSPECT with Flash 3D for 4 half-time stress-scan dose conditions: full-dose, half-dose, quarter-dose, and eighth-dose. D.Study endpoints: A.Primary end point: Regional and global TPD scores B.Secondary end point(s): Image quality (based on visual interpretation of the images for count density, signal to noise ratio, artifacts, and overall interpretive quality). E.Study variables: SPECT hardware/software and injected dose (via simulation) Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology

4. RESULTS Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology Fig. 1 SPECT/CT myocardial perfusion images of a subject with normal perfusion. All images were reconstructed iteratively and corrected for attenuation.

5. RESULTS Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology Fig. 4 Bland Altman-Plots comparing the global Total Perfusion Deficit (TPD) score of Low Energy High Resolution (LEHR) stress images to the global TPD of IQSPECT stress images for 68 subjects. The solid line represents the mean difference in global TPD scores and the dashed lines represent ±two SDs.

6. CONCLUSIONS 1- Tc-99m sestamibi SPECT perfusion images, quantitatively equivalent to those acquired with the standard injected activity using Low Energy High Resolution (LEHR) collimation, can be obtained with IQSPECT technology in half the time, and with half the injected dose. 2- Differences in Total Perfusion Deficit scores between LEHR and IQSPECT were statistically significant at quarter and eighth-dose conditions with half-time imaging. Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology