Low dose and short time imaging protocol of rest-stress ¹³N ammonia PET with time of flight technique

Purpose: ¹³N ammonia myocardial perfusion PET (¹³N) needs approximately 60min to allow sufficient radio-active decay for stress imaging. The aim of this study was to shorten the interval of rest and stress scan by employing low-dose rest study with help of high resolution-time of flight PET scanner.

Methods: Low dose (185MBq) of ¹³N rest study was performed prior to standard and conventional dose (555MBq) of rest/ adenosine stress ¹³N PET protocol (figure) for 26 patients (age 65±11, male 20). Ejection fraction (EF), end diastolic/ systolic volume=EDV and ESV, and myocardial blood flow (MBF, corrected for normal dose) were compared between low and normal - dose rest scans. Relative values of myocardial uptake (%uptake) from static images were also compared.

Results: EF, EDV, ESV, and MBF showed significant correlation between low and normal-dose (r=0.97, 0.99, 0.99, 0.88 for EF, EDV, ESV, and MBF; p<0.0001 for all). Bland-Altman plot showed good agreement (%limits of agreement: -3.5 to 4.6, -5.3 to 4.9, -3.4 to 4.3, -0.22 to 0.15, and -4.2 to 4.4 for EF, EDV, ESV, MBF, and %uptake). Conclusion Introducing low dose rest ¹³N is feasible and will shorten the conventional protocol and improve throughput time for cardiac PET.

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