Count rate performance and dose optimization for rCBF with O-15 water bolus injection in a new 3D PET

Journal Article · Mon May 01 04:00:00 EDT 1995 · Journal of Nuclear Medicine

OSTI ID:441612

Holm, S; Law, I; Paulson, O B ^[1]

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1. Univ. Hospital, Copenhagen (Denmark)

Increasingly complicated paradigms for study of brain function combined with new higher dose estimates for O-15 water stress the need for high sensitive equipment and optimized dose utilization. We use a new PET scanner (Advance, General Electric) in 3D mode covering 15 cm in 35 slices with an approx. isotrope resolution of 5 mm. For bolus water studies we collect one 90 sec frame after 20 sec delay. Total counts (trues and randoms in FOV) are stored in 1 sec intervals from 120 sec before injection. Reconstruction and archiving within 8 min allow studies every 10 minutes unlimited. From the observed count rate curves we calculate Noise Equivalent Counts (NEC) assuming values for randoms fraction (0.32) and scatter (0.25). In 6 normal volunteers we studied the dependency of NEC on activity with 7 injections 25-1600 MBq during rest (eyes closed, lights dimmed). The 50-800 MBq exams were duplicated with eyes open and lights on. Additionally decay experiments have been performed in various phantoms. Observed activation response in gross {open_quote}visual{close_quote} ROIs relative to mean brain was independent of injected activity. The calculated NEC versus injected dose (normalized to 70 kg) has a broad maximum around the value at 800 MBq. NEC per MBq plotted against MBq is an efficiency measure. Its maximal value for activity approaching zero is about 60 kcounts/MBq. Optimal activity per injection depends on actual limits of effective dose and the paradigm, i.e., required minimum No. injections. More than 400MBq in one bolus has very limited effect on NEC; fractioning below 100 MBq to maximize total counts also has low benefit and is not recommended unless required by paradigm.

• OSTI ID: 441612
• Report Number(s): CONF-950603--
• Journal Information: Journal of Nuclear Medicine, Journal Name: Journal of Nuclear Medicine Journal Issue: Suppl.5 Vol. 36; ISSN JNMEAQ; ISSN 0161-5505
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
56 BIOLOGY AND MEDICINE
APPLIED STUDIES
BRAIN
COUNTING RATES
DIAGNOSTIC TECHNIQUES
OXYGEN 15
PHANTOMS
POSITRON COMPUTED TOMOGRAPHY
RECORDING SYSTEMS
WATER