TITLE:
An Investigation of the Required MR Bone Attenuation Correction for Quantitative Whole-Body PET/MR Imaging Using Clinical NaF PET/CT Studies
AUTHORS:
Hua A. Ai, Osama Mawlawi, R. Jason Stafford, Jim Bankson, Yiping Shao, Michele Guindani, Richard E. Wendt III
KEYWORDS:
PET/MR, Attenuation Correction, MR-Based Attenuation Correction
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.7 No.3,
June
4,
2018
ABSTRACT: Tissue-classification-based
attenuation correction strategies have been previously proposed to correct for
bone attenuation in PET/MR imaging and simulated using computed tomography.
However, the complication of voxel averaging uniquely associated with bone has
not been considered explicitly in the past. This study investigated the effect
of voxel averaging between bone and soft tissue in attenuation images and
determined how accurately bone must be detected in MR images in order to
perform acceptable attenuation correction of PET data by using CT-simulated
attenuation correction. We found out that treating bone as soft tissue caused a
mean quantification difference of -9.9% ± 5.5% in all 119 bone lesions. There were no significant
differences between lesions in the pelvis and the vertebrae. The nominal
difference in lesions in the ribs was significantly lower, likely due to the
spatial misregistration between the emission and attenuation images.
Interestingly, a non-monotonic relationship between the bone imaging ability
and the absolute PET quantification accuracy was observed, with the minimal
quantification difference achieved at a BVF around 40% for skull lesions (2.6%
± 2.1%), and 30% for non-skull lesions (1.4% ± 1.1%) and all lesions (1.5% ±
1.3%). This study established that a bone classification sensitivity of
approximately 30% BVF is required in order for MR-based attenuation correction
methods to achieve optimal quantification in whole-body PET/MR studies. For
this purpose, higher bone imaging ability of MR may not be necessary.