Abstract
PurposeThe trend towards faster acquisition protocols in whole-body positron emission tomography/magnetic resonance (PET/MR) arises the question of whether short PET data acquisition protocols in a whole-body multi-station context allow for reduced PET acquisition times while providing adequate PET image quality and accurate quantification parameters. The study goal is to investigate how reducing PET acquisition times affects PET image quality and quantification in whole-body PET/MR in patients with oncologic findings.MethodsFifty-one patients with different oncologic findings underwent a clinical whole-body 18F-Fluorodeoxyglucose PET/MR examination. PET data was reconstructed with 4, 3, 2, and 1 min/bed time intervals for each patient to simulate the effect of reduced PET acquisition times. The 4-minute PET reconstructions served as reference standard. All whole-body PET data sets were analyzed regarding image quality, lesion detectability, PET quantification and standardized uptake values.ResultsA total of 91 lesions were detected in the 4-minute PET reconstructions. The same number of congruent lesions was also noticed in the 3 and 2 minutes-per-bed (mpb) reconstructed images. A total of 2 lesions in 2 patients was not detected in the 1 minute PET data reconstructions due to poor image quality. Image noise in the blood pool increased from 22.2% (4 mpb) to 42.1% (1 mpb). Signal-to-noise ratio declined with shorter timeframes from 13.1 (4 mpb) to 9.3 (1 mpb). SUVmean and SUVmax showed no significant changes between 4 and 1 mpb reconstructed timeframes.ConclusionsReconstruction of PET data with different time intervals has shown that 2 minutes acquisition time per bed position instead of 4 minutes is sufficient to provide accurate lesion detection and adequate image quality in a clinical setting, despite the trends to lower image quality with shorter PET acquisition times. This provides latitude for potential reduction of PET acquisition times in fast PET/MR whole-body examinations.
Highlights
The successful integration of positron emission tomography (PET) and magnetic resonance (MR) imaging into one whole-body positron emission tomography/ magnetic resonance (PET/MR) system combines the excellent soft-tissue contrast and several functional imaging parameters provided by MR with the high sensitivity and quantification of radiotracer metabolism supplied by PET [1] [2] [3]
Magnetic resonance (PET/MR) arises the question of whether short PET data acquisition protocols in a whole-body multi-station context allow for reduced PET acquisition times while providing adequate PET image quality and accurate quantification parameters
The successful integration of positron emission tomography (PET) and magnetic resonance (MR) imaging into one whole-body PET/MR system combines the excellent soft-tissue contrast and several functional imaging parameters provided by MR with the high sensitivity and quantification of radiotracer metabolism supplied by PET [1] [2] [3]
Summary
The successful integration of positron emission tomography (PET) and magnetic resonance (MR) imaging into one whole-body PET/MR system combines the excellent soft-tissue contrast and several functional imaging parameters provided by MR with the high sensitivity and quantification of radiotracer metabolism supplied by PET [1] [2] [3]. In most PET/MR imaging protocols this comes at the at the cost of considerably increased PET/MR acquisition times when compared to PET/CT This is because MR requires the acquisition of multiple different imaging sequences (e.g. T1, T2, diffusion weighted imaging) to generate a choice of soft tissue contrasts per bed position. A clinical routine whole-body PET/MR protocol including 4–5 bed positions with a duration of 5–10 minutes per bed position mainly consists of five MR sequences (T1-weighted Dixon-VIBE, diffusion weighted EPI, T2-weighted TIRM, T2-weighted HASTE and T1-weighted VIBE post contrast). This prolonged whole-body MR protocol ensures different soft tissue for diagnostic assessment in a variety of oncologic indications. In such rather lengthy protocols, MR is currently the time limiting factor in PET/MR imaging
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