The Effect of Including Bone in DIXON-based Attenuation Correction for 18 F-fluciclovine PET/MRI of Prostate Cancer

• Published in: Journal of Nuclear Medicine Vol. 59; no. 12; pp. 1913 - 1917
• Main Authors: Elschot, Mattijs, Selnæs, Kirsten M, Johansen, Håkon, Krüger-Stokke, Brage, Bertilsson, Helena, Bathen, Tone F
• Format: Journal Article
• Language: English
• Published: United States 01-12-2018
• Subjects: FACBC; PET/MRI; fluciclovine; Image Reconstruction; Oncology: GU; Prostate Cancer; Attenuation Correction
• ISSN: 0161-5505; 1535-5667; 2159-662X
• DOI: 10.2967/jnumed.118.208868

The objective of this study was to evaluate the effect of including bone in DIXON-based attenuation correction for
F-fluciclovine Positron Emission Tomography (PET) / Magnetic Resonance Imaging (MRI) of primary and recurrent prostate cancer.
F-fluciclovine PET data from two PET/MRI studies - one for staging of high-risk prostate cancer (28 patients) and one for diagnosis of recurrent prostate cancer (81 patients) - were reconstructed with a 4-compartment (reference) and 5-compartment attenuation map. In the latter, continuous linear attenuation coefficients for bone were included by co-registration with an atlas. The maximum and mean 50% isocontour standardized uptake values (SUV
and SUViso, respectively) of primary, locally recurrent, and metastatic lesions were compared between the two reconstruction methods using linear mixed-effects models. In addition, mean SUVs were obtained from bone marrow in the third lumbar vertebra (L3) to investigate the effect of including bone attenuation on lesion-to-bone marrow SUV ratios (SUVRmax and SUVRiso; recurrence study only). The 5-compartment attenuation maps were visually compared to the in-phase DIXON MR images for evaluation of bone registration errors near the lesions. P-values < 0.05 were considered significant.
Sixty-two (62) lesions from 39 patients were evaluated. Bone registration errors were found near 19 (31%) of these lesions. In the remaining 8 primary prostate tumors, 7 locally recurrent lesions, and 28 lymph node metastases without bone registration errors, using the 5-compartment attenuation map was associated with small but significant increases in SUV
[2.5%; 95% confidence interval (CI) 2.0%-3.0%; p<0.001] and SUViso (2.5%; 95% CI 1.9%-3.0%; p<0.001), but not SUVRmax (0.2%; 95% CI -0.5%-0.9%;
= 0.604) and SUVRiso (0.2%; 95% CI -0.6%-1.0%;
= 0.581), in comparison to the 4-compartment attenuation map.
The investigated method for atlas-based inclusion of bone in
F-fluciclovine PET/MRI attenuation correction has only a small effect on the SUVs of soft-tissue prostate cancer lesions, and no effect on their lesion-to-bone marrow SUVRs when using signal from L3 as a reference. The attenuation maps should always be checked for registration artefacts for lesions in or close to the bones.