Approaches for the optimization of MR protocols in clinical hybrid PET/MRI studies

Abstract

Magnetic resonance imaging (MRI) is the examination method of choice for the diagnosis of a variety of diseases. MRI allows us to obtain not only anatomical information but also identification of physiological and functional parameters such as networks in the brain and tumor cellularity, which plays an increasing role in oncologic imaging, as well as blood flow and tissue perfusion. However, in many cases such as in epilepsy, degenerative neurological diseases and oncological processes, additional metabolic and molecular information obtained by PET can provide essential complementary information for better diagnosis. The combined information obtained from MRI and PET acquired in a single imaging session allows a more accurate localization of pathological findings and better assessment of the underlying physiopathology, thus providing a more powerful diagnostic tool. Two hundred and twenty-one patients were scanned from April 2011 to January 2012 on a Philips Ingenuity TF PET/MRI system. The purpose of this review article is to provide an overview of the techniques used for the optimization of different protocols performed in our hospital by specialists in the following fields: neuroradiology, head and neck, breast, and prostate imaging. This paper also discusses the different problems encountered, such as the length of studies, motion artifacts, and accuracy of image fusion including physical and technical aspects, and the proposed solutions.

Diagnostic Value of Diffusion-Weighted Imaging in Simultaneous 18F-FDG PET/MR Imaging for Whole-Body Staging of Women with Pelvic Malignancies

“…The recent introduction of PET/MR imaging scanners has opened a new platform for simultaneous high-quality assessment of local tumor extent and metastatic spread by combining morphologic (MR imaging), functional (DWI), and metabolic (PET) features (10)(11)(12). Nevertheless, a distinct disadvantage of PET/MR imaging compared with PET/CT lies in the significantly prolonged examination time, caused mainly by the acquisition of a substantial number of available MR sequences.…”

Principles of PET/MR Imaging

“…In sequential scanners, PET and sequences for AC prolong the total acquisition, which could lead to unacceptably long acquisition times. Moreover, because of the time delay between MR and PET acquisition, differences in, for example, bladder filling between the 2 scans can lead to misregistrations (39). In simultaneous systems, images are more accurately registered (40) and the total acquisition times can be shorter because the anatomic images, AC sequences, and additional functional imaging can be acquired during the PET acquisition (41).…”

“…Clinical considerations in PET/MR acquisition protocols are discussed for the Biograph mMR (Siemens) by Martinez-Möller et al (41) and for the Ingenuity (Philips) by Vargas et al (39). In preclinical imaging, both PET and MR images are usually acquired in 1 bed position (42,43).…”

Review of Epilepsy - Etiology, Diagnostic Evaluation and Treatment

“…This may reflect the difficulty in localizing and resecting the epileptogenic zone [60]. In order to improve the radiographic detection of epileptogenic lesions, more advanced imaging techniques have been used such as 7T MRI, volumetric analysis, Diffusion Tensor Imaging (DTI), arterial spin labeling and PET [38,[66][67][68][69][70][71][72][73][74]. However, it is currently unknown if such techniques willimprove outcomes.…”