Temporal evolution of administered activity in cardiac gated SPECT and patients’ effective dose: analysis of an historical series

• Published in: European journal of nuclear medicine and molecular imaging Vol. 40; no. 3; pp. 325 - 330
• Main Authors: Marcassa, C., Zoccarato, O., Calza, P., Campini, R.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.02.2013; Springer Nature B.V
• Subjects: Adoption; Aged; Algorithms; alpha Radiation; Cameras; Cardiac-Gated Single-Photon Emission Computer-Assisted Tomography - adverse effects; Cardiac-Gated Single-Photon Emission Computer-Assisted Tomography - methods; Cardiology; Drug therapy; Emotions; Evolution; Female; Heart; Humans; Imaging; Male; Medicine; Medicine & Public Health; Myocardial Perfusion Imaging - adverse effects; Nuclear Medicine; Occupational Exposure - analysis; Oncology; Original Article; Orthopedics; Patients; Perfusion; Radiation; Radiation Dosage; Radiology; Retrospective Studies; Single photon emission computed tomography; Technetium Tc 99m Sestamibi - adverse effects; Time Factors; Tracers; Myocardial perfusion imaging dosimetry; Gated SPECT; Radiation exposure
• ISSN: 1619-7070; 1619-7089
• DOI: 10.1007/s00259-012-2287-5

Purpose Myocardial perfusion imaging contributes >20 % of the average medical radiation exposure to the population in the USA. Imaging protocols able to achieve a radiation exposure ≤9 mSv in 50 % of the studies by 2014 have been recommended. The aim of this study was to analyse the temporal evolution of administered activities in patients scheduled for dual-day 99m Tc tracer gated single photon emission computed tomography (SPECT) and to compare different dose administration protocols in terms of patients’ effective dose. Methods Patients evaluated from 1 July 2002 to 31 January 2012 were allocated according to the protocol adopted: group 1: fixed activity according to diagnostic reference level: 740 MBq up to 80 kg (adapted for weight <60 kg); 900 MBq 80–100 kg, 1,110 MBq >100 kg, standard filtered back-projection (FBP) reconstruction; group 2: weight-adjusted activity: 8 MBq/kg up to 1,110 MBq, standard FBP reconstruction; and group 3: 4 MBq/kg, UltraSPECT wide beam reconstruction (WBR) reconstruction. A dual-head Anger camera (GE Helix) was used. Results A total of 9,060 patients were allocated to different groups: 4,751 in group 1, 2,844 in group 2 and 1,465 in group 3. The stress + rest administered activity was 1,617 ± 180 in group 1, 1,136 ± 260 in group 2 and 682 ± 164 MBq in group 3 (all p  < 0.001). Patients’ effective dose was 13.7 ± 3 in group 1, 9.5 ± 2.8 in group 2 and 5.7 ± 1.6 mSv in group 3 (all p  < 0.001). The 50th percentile was 12.6 in group 1, 9.1 in group 2 and 5.3 mSv in group 3. The effective dose received by the dedicated cardiologists was 2.1, 1.5 and 1.0 μSv/exam in group 1, group 2 and group 3 periods, respectively (all p  < 0.001). Conclusion A significant reduction over time in the administered activity for gated SPECT was achieved; accordingly, a significant reduction in patients’ exposure was obtained. A simple weight-adjusted strategy with 8 MBq/kg immediately fulfils the recommendations to limit exposure. In selected group 3 patients, a stress-only strategy allows for studies with <3 mSv exposure. Thus, at least the adoption of a new reconstruction algorithm is strongly encouraged, and suggested tracer activities for cardiac gated SPECT are to be revised.