Clinical application of PET/MRI in oncology

Abstract

Hybrid imaging with integrated positron emission tomography (PET) and magnetic resonance imaging (MRI) combines the advantages of the high-resolution anatomic data from MRI and functional imaging data from PET, and has the potential to improve the diagnostic evaluation of various types of cancers. The clinical oncologic applications of this newest hybrid imaging technology are evolving and substantial efforts are underway to define the role of PET/MRI in routine clinical use. The current published literature suggests that PET/MRI may play an important role in the evaluation of patients with certain types of malignancies, involving anatomic locations such as the pelvis and the liver. The purpose of this article is to review the current published PET/MRI literature in specific body oncologic applications. In addition, PET/MRI protocols and some of the technical issues of this hybrid imaging will be briefly discussed. J. Magn. Reson. Imaging 2016;44:265-276.

Application of Multimodality Imaging Fusion Technology in Diagnosis and Treatment of Malignant Tumors under the Precision Medicine Plan

“…[35] Integrative PET/MRI has both high soft-tissue resolution of MRI and high specificity of PET imaging, thus confirming that it has obvious advantages in the early diagnosis of head and neck tumors, breast cancers, and abdominal and pelvic tumors. [3637] Heusch et al .…”

Whole-body PET/MRI for colorectal cancer staging: Is it the way forward?

“…However, although simultaneous scanning of PET and MRI reduces the misregistration between the two image sets, it is still challenging to match breath-held MR images with freebreathing PET images. 25 In abdominal imaging, this misregistration is most pronounced in studies of the upper abdomen, such as dedicated liver PET/MRI. 35 Indeed, it has previously been demonstrated that the combination of freebreathing PET data with breath-hold MRI sequences can lead to distortion in liver contours, attenuation correction errors, and imaging registration errors.…”

“…In the midst of these diverse imaging techniques for the evaluation of colorectal cancer, an integrated wholebody PET/MRI system which can provide both the highresolution anatomic data of MRI and functional imaging data of PET has recently been introduced. [14][15][16][17][18][19][20][21][22][23][24][25] The clinical advantages of PET/MRI relate predominantly to improvements provided by MRI over CT and the potential for simultaneous PET and MRI acquisitions. 25 Indeed, hybrid PET/MRI can provide several advantages compared with PET/CT: a lack of ionizing radiation, functional imaging such as DWI or dynamic contrast-enhanced (DCE) MRI, the ability to capture cardiac or respiratory motion for better registration, and improved soft-tissue contrast.…”

“…25 Indeed, hybrid PET/MRI can provide several advantages compared with PET/CT: a lack of ionizing radiation, functional imaging such as DWI or dynamic contrast-enhanced (DCE) MRI, the ability to capture cardiac or respiratory motion for better registration, and improved soft-tissue contrast. 25 However, there are also several disadvantages of hybrid PET/ MRI systems, including 3 to 5 times higher cost than PET/ CT, as well as longer examination times and limited patient throughput. Therefore, although combining functional information with anatomic information is an obvious advantage of PET/MRI over PET/CT, the imaging protocols are difficult to complete in the time required for PET/ CT acquisitions.…”

“…22 To the contrary, the main disadvantages of PET/CT are the relatively high radiation exposure from the two components, low contrast resolution of noncontrast CT for soft tissue, and the relatively low spatial resolution of PET data. 22,25 At present, in clinical practice, PET/MRI is preferentially used over PET/CT in the following situations: 1) when imaging the brain, head and neck, abdominal solid organs including the liver, the heart, and the musculoskeletal system due to the better soft-tissue contrast of the MRI component 22,24,[26][27][28][29][30][31] ; 2) when imaging children and women of child-bearing age due to the reduced radiation exposure of PET/MRI; and 3) when the combined anatomic and functional capabilities of MRI together with molecular PET information is needed to provide new insights into disease phenotypes and biology. 22,32 Considering this theoretical background of whole-body PET/MRI, it may not be far-fetched to assume that it may also provide higher performance in the local staging of rectal cancer as well as in detecting distant metastases in patients with colorectal cancer compared to CT or MRI alone.…”