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Integrated whole body MR/PET: where are we?

Yoo HJ, Lee JS, Lee JM - Korean J Radiol (2015)

Bottom Line: This review provides an overview of the technical background of combined MR/PET systems, a discussion of the potential advantages and technical challenges of hybrid MR/PET instrumentation, as well as collection of possible solutions.Various early clinical applications of integrated MR/PET are also addressed.Finally, the workflow issues of integrated MR/PET, including maximizing diagnostic information while minimizing acquisition time are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Seoul National University Hospital, Seoul 110-744, Korea.

ABSTRACT
Whole body integrated magnetic resonance imaging (MR)/positron emission tomography (PET) imaging systems have recently become available for clinical use and are currently being used to explore whether the combined anatomic and functional capabilities of MR imaging and the metabolic information of PET provide new insight into disease phenotypes and biology, and provide a better assessment of oncologic diseases at a lower radiation dose than a CT. This review provides an overview of the technical background of combined MR/PET systems, a discussion of the potential advantages and technical challenges of hybrid MR/PET instrumentation, as well as collection of possible solutions. Various early clinical applications of integrated MR/PET are also addressed. Finally, the workflow issues of integrated MR/PET, including maximizing diagnostic information while minimizing acquisition time are discussed.

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Ultrashort echo time (UTE) MRI-based attenuation correction.MR images acquired at first (A) and second (B) echo times (echo time = 0.07 ms and 2.46 ms, respectively). C. Differential image of A and B. D. UTE-based attenuation map. E. CT of same patient.
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Figure 2: Ultrashort echo time (UTE) MRI-based attenuation correction.MR images acquired at first (A) and second (B) echo times (echo time = 0.07 ms and 2.46 ms, respectively). C. Differential image of A and B. D. UTE-based attenuation map. E. CT of same patient.

Mentions: Inclusion of bone segments in head datasets is essential, as the brain is surrounded by cortical bones (13, 46). Failure to account for bone attenuation in brain PETs introduces a spatially variable bias, which is highest in the other cortical structures and lower in the central brain (13). The currently used method for cortical-bone segmentation in head MRI is the ultrashort echo time (UTE) sequence which is specially designed to visualize tissue with a short T2 relaxation time (41). With this method, MR images acquired at two different echo times, i.e., ultra-short and typical times, are compared in order to identify the bone regions (Fig. 2). Initial versions of the UTE sequence sometimes yield errors in determining the boundary between soft tissue and air and in classifying the ventricle as cerebrospinal fluid (45, 47, 48). Therefore, it is necessary to continue to optimize and further develop MR pulse sequences and image segmentation methods in order to enhance the generation of the PET attenuation map.


Integrated whole body MR/PET: where are we?

Yoo HJ, Lee JS, Lee JM - Korean J Radiol (2015)

Ultrashort echo time (UTE) MRI-based attenuation correction.MR images acquired at first (A) and second (B) echo times (echo time = 0.07 ms and 2.46 ms, respectively). C. Differential image of A and B. D. UTE-based attenuation map. E. CT of same patient.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4296276&req=5

Figure 2: Ultrashort echo time (UTE) MRI-based attenuation correction.MR images acquired at first (A) and second (B) echo times (echo time = 0.07 ms and 2.46 ms, respectively). C. Differential image of A and B. D. UTE-based attenuation map. E. CT of same patient.
Mentions: Inclusion of bone segments in head datasets is essential, as the brain is surrounded by cortical bones (13, 46). Failure to account for bone attenuation in brain PETs introduces a spatially variable bias, which is highest in the other cortical structures and lower in the central brain (13). The currently used method for cortical-bone segmentation in head MRI is the ultrashort echo time (UTE) sequence which is specially designed to visualize tissue with a short T2 relaxation time (41). With this method, MR images acquired at two different echo times, i.e., ultra-short and typical times, are compared in order to identify the bone regions (Fig. 2). Initial versions of the UTE sequence sometimes yield errors in determining the boundary between soft tissue and air and in classifying the ventricle as cerebrospinal fluid (45, 47, 48). Therefore, it is necessary to continue to optimize and further develop MR pulse sequences and image segmentation methods in order to enhance the generation of the PET attenuation map.

Bottom Line: This review provides an overview of the technical background of combined MR/PET systems, a discussion of the potential advantages and technical challenges of hybrid MR/PET instrumentation, as well as collection of possible solutions.Various early clinical applications of integrated MR/PET are also addressed.Finally, the workflow issues of integrated MR/PET, including maximizing diagnostic information while minimizing acquisition time are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Seoul National University Hospital, Seoul 110-744, Korea.

ABSTRACT
Whole body integrated magnetic resonance imaging (MR)/positron emission tomography (PET) imaging systems have recently become available for clinical use and are currently being used to explore whether the combined anatomic and functional capabilities of MR imaging and the metabolic information of PET provide new insight into disease phenotypes and biology, and provide a better assessment of oncologic diseases at a lower radiation dose than a CT. This review provides an overview of the technical background of combined MR/PET systems, a discussion of the potential advantages and technical challenges of hybrid MR/PET instrumentation, as well as collection of possible solutions. Various early clinical applications of integrated MR/PET are also addressed. Finally, the workflow issues of integrated MR/PET, including maximizing diagnostic information while minimizing acquisition time are discussed.

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