Quantitative and Visual Assessments toward Potential Sub-mSv or Ultrafast FDG PET Using High-Sensitivity TOF PET in PET/MRI

• Published in: Molecular imaging and biology Vol. 20; no. 3; pp. 492 - 500
• Main Authors: Behr, Spencer C., Bahroos, Emma, Hawkins, Randall A., Nardo, Lorenzo, Ravanfar, Vahid, Capbarat, Emily V., Seo, Youngho
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2018; Springer Nature B.V
• Subjects: Assessments; Brain; Computed tomography; Data acquisition; Datasets; Diagnostic systems; Field of view; Fluorodeoxyglucose F18 - chemistry; Glucose; Humans; Image acquisition; Image quality; Imaging; Injection; Lesions; Magnetic Resonance Imaging; Medicine; Medicine & Public Health; Neuroimaging; NMR; Nuclear magnetic resonance; Photomultiplier tubes; Positron emission; Positron emission tomography; Radiology; Reduction; Research Article; Sensitivity; Sensitivity analysis; Statistical analysis; Statistical significance; Time Factors; Tissues; Tomography; Timing resolution; Ultrafast; PET/MRI; Sub-mSv; PET/CT; TOF; High-sensitivity; PET
• ISSN: 1536-1632; 1860-2002
• DOI: 10.1007/s11307-017-1145-z

Purpose Newer high-performance time-of-flight (TOF) positron emission tomography (PET) systems have the capability to preserve diagnostic image quality with low count density, while maintaining a high raw photon detection sensitivity that would allow for a reduction in injected dose or rapid data acquisition. To assess this, we performed quantitative and visual assessments of the PET images acquired using a highly sensitive (23.3 cps/kBq) large field of view (25-cm axial) silicon photomultiplier (SiPM)-based TOF PET (400-ps timing resolution) integrated with 3 T-MRI in comparison to PET images acquired on non-TOF PET/x-ray computed tomography (CT) systems. Procedures Whole-body 2-deoxy-2-[ 18 F]fluoro-D-glucose ([ 18 F]FDG) PET/CT was acquired for 15 patients followed by whole body PET/magnetic resonance imaging (MRI) with an average injected dose of 325 ± 84 MBq. The PET list mode data from PET/MRI were reconstructed using full datasets (4 min/bed) and reduced datasets (2, 1, 0.5, and 0.25 min/bed). Qualitative assessment between PET/CT and PET/MR images were made. A Likert-type scale between 1 and 5, 1 for non-diagnostic, 3 equivalent to PET/CT, and 5 superior quality, was used. Maximum and mean standardized uptake values (SUV max and SUV mean ) of normal tissues and lesions detected were measured and compared. Results Mean visual assessment scores were 3.54 ± 0.32, 3.62 ± 0.38, and 3.69 ± 0.35 for the brain and 3.05 ± 0.49, 3.71 ± 0.45, and 4.14 ± 0.44 for the whole-body maximum intensity projections (MIPs) for 1, 2, and 4 min/bed PET/MR images, respectively. The SUV mean values for normal tissues were lower and statistically significant for images acquired at 4, 2, 1, 0.5, and 0.25 min/bed on the PET/MR, with values of – 18 ± 28 % ( p  < 0.001), − 16 ± 29 % ( p  = 0.001), − 16 ± 31 % ( p  = 0.002), − 14 ± 35 % ( p  < 0.001), and − 13 ± 34 % ( p  = 0.002), respectively. SUV max and SUV peak values of all lesions were higher and statistically significant ( p  < 0.05) for 4, 2, 1, 0.50, and 0.25 min/bed PET/MR datasets. Conclusion High-sensitivity TOF PET showed comparable but still better visual image quality even at a much reduced activity in comparison to lower-sensitivity non-TOF PET. Our data translates to a seven times reduction in either injection dose for the same time or total scan time for the same injected dose. This “ultra-sensitivity” PET system provides a path to clinically acceptable extremely low-dose FDG PET studies (e.g., sub 1 mCi injection or sub-mSv effective dose) or PET studies as short as 1 min/bed (e.g . , 6 min of total scan time) to cover whole body without compromising diagnostic performance.