Abstract
Attenuation correction is an essential requirement for quantification of positron emission tomography (PET) data. In PET/CT acquisition systems, attenuation maps are derived from computed tomography (CT) images. However, in hybrid PET/MR scanners, magnetic resonance imaging (MRI) images do not directly provide a patient-specific attenuation map. The aim of the proposed work is to improve attenuation correction for PET/MR scanners by generating synthetic CTs and attenuation maps. The synthetic images are generated through a multi-atlas information propagation scheme, locally matching the MRI-derived patient's morphology to a database of MRI/CT pairs, using a local image similarity measure. Results show significant improvements in CT synthesis and PET reconstruction accuracy when compared to a segmentation method using an ultrashort-echo-time MRI sequence and to a simplified atlas-based method.
Highlights
P OSITRON emission tomography/magnetic resonance imaging (PET/MR) scanners are expected to offer a new range of applications in neuro-oncology, epilepsy and neurodegenerative diseases such as Alzheimer’s disease [1]
The existence of a plateau in terms of accuracy in the parameter space means that small changes in parameters result in a very similar pseudo computed tomography (CT) and indicates that the method is robust to the choice of parameters
This paper presents a CT and attenuation map synthesis algorithm based on a multi-atlas information propagation scheme
Summary
P OSITRON emission tomography/magnetic resonance imaging (PET/MR) scanners are expected to offer a new range of applications in neuro-oncology, epilepsy and neurodegenerative diseases such as Alzheimer’s disease [1]. The attenuation information is usually obtained from a transmission scan in standalone PET or derived from a computed tomography (CT) image in combined PET/CT systems. Regarding PET/MR scanners, the strong magnetic field and the limited bore diameter of the MRI prevent the use of a transmission source. As MRI image intensities do not reflect the electron densities, alternative methods must be developed for PET/MR acquisitions. These methods can be classified into three main categories: emission, segmentation, and atlas-based approaches [2]
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