Functional, physiological, and metabolic toolbox for clinical magnetic resonance imaging: Integration of acquisition and analysis strategies

Abstract

Selected neuroimaging strategies have been integrated into a clinical brain imaging protocol to provide quantitative high‐resolution functional, physiological, and metabolic maps to complement exquisitely detailed anatomic images without excessively prolonging the conventional clinical examination or analysis time. The physiological maps of blood pool parameters (relative cerebral blood volume, tissue transit time, and arrival time), apparent diffusion coefficient, tissue water content, and functional neuronal activation maps are derived from series of images acquired with echo‐planar imaging. The metabolic map reflecting tissue sodium homeostasis (tissue sodium concentration) is acquired using twisted projection imaging and a customized dual‐tuned, dual‐quadrature 23Na/1H brain radiofrequency coil that ensures coregistration of data and avoids moving the patient. The different types of acquired images are transferred to a common file format with customized file management software and the corresponding maps are derived by applying appropriate fitting algorithms. Customized software allows rapid interrogation and manipulation of all resultant images and maps for detailed but rapid interpretation, printing, and archiving immediately following completion of acquisition. As all acquisitions and processing are performed by the magnetic resonance technologist, the neuroradiologist is able to focus on the interpretation of this immensely rich data set. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 572–581, 1997

Visual feedback to stabilize head position for fMRI

“…Our experience is that such interference from the visual feedback system is not significant in the activation maps produced with t-tests at either 1.5 or 3.0 T. The visor reduces head motion for cooperative subjects to allow whole-brain fMRI. This is suitable for mapping studies as used clinically for locating eloquent cortex in presurgical planning for epilepsy (27,28). Given the requirement to minimize head motion, the current device fills an important role in aiding the acquisition of high-quality fMRI data without patient discomfort from bite bar or thermoplastic mask.…”

Simultaneous single‐quantum and triple‐quantum‐filtered MRI of 23Na (SISTINA)

“…The methods used in the aforementioned studies are only able to provide a weighted average of the intracellular and extracellular signals. However, measurement of the changes in sodium concentration in the intracellular compartment would yield useful information on cell viability (2, 6). A number of previous studies showed different ways to differentiate intracellular from extracellular sodium signals.…”

Low‐rank reconstruction for simultaneous double half‐echo 23Na and undersampled 23Na multi‐quantum coherences MRI

“…The signal originating from the intracellular space is particularly interesting when assessing cell viability. 9,10 As suggested by previous findings, the TQ signal might be sensitive to the intracellular compartment 8,[11][12][13] and therefore, possibly enables additional tissue characterization. Sampling MQCs is challenging and requires specific 23 Na MR sequences involving at least three radiofrequency (RF) pulses with multiple phase-cycling to filter for the 23 Na quantum coherences.…”

“…Especially the triple quantum (TQ) signal could provide richer tissue sodium characterization, which is linked to cell vitality 7,8 when compared to conventional single quantum (SQ) signal alone. The signal originating from the intracellular space is particularly interesting when assessing cell viability 9,10 . As suggested by previous findings, the TQ signal might be sensitive to the intracellular compartment 8,11–13 and therefore, possibly enables additional tissue characterization.…”