Phantoms for diffusion-weighted imaging and diffusion tensor imaging quality control: a review and new perspectives

Abstract

Introduction: Diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) combine magnetic resonance imaging (MRI) techniques and diffusion measures. In DWI, the contrast is defined by microscopic motion of water protons. Nowadays, DWI has become important for early diagnostic of acute stroke. DTI images are calculated from DWI images acquired in at least six directions, which give information of diffusion directionality, making it possible to reconstruct axonal or muscle fiber images. Both techniques have been applied to study body structures in healthy and pathological conditions. Currently, it is known that these images and derived parameters are quite sensitive to factors related to acquisition and processing. Magnetic field inhomogeneity, susceptibility, chemical shift, radiofrequency (RF) interference, eddy currents and low signal-to-noise ratio (SNR) can have a more harmful effect in diffusion data than in T1-or T2-weighted image data. However, even today there are not reference phantoms and guidelines for DWI or DTI quality control (QC). Review: Proposals for construction and use of DWI and DTI QC phantoms can be found in literature. DWI have been evaluated using containers filled by gel or liquid with tissue-like MRI properties, as well as using microfabricated devices. DTI acquisitions also have been checked with these devices or using natural or artificial fiber structures. The head phantom from American College of Radiology (ACR) is also pointed out as an alternative for DTI QC. This article brings a discussion about proposed DWI and DTI phantoms, challenges involved and future perspectives for standardization of DWI and DTI QC.

Prognostic value of global deep white matter DTI metrics for 1-year outcome prediction in ICU traumatic brain injury patients: an MRI-COMA and CENTER-TBI combined study

“…First, MRI scanner calibration currently requires data from a handful of controls undergoing exactly the same protocol as the patients, which is further complicated by the regular updates of MRI sequences and the difficulties associated with scanning healthy subjects using clinical equipment. Developing an MRI phantom suitable for calibrating DTI metrics would be a solution to bypass these difficulties but such devices are not routinely available yet [34]. Secondly, transportation and monitoring of ventilated patients to the MRI is complex and may requires immobilization by means of sedation with neuromuscular blocker.…”

Development of a standard phantom for diffusion-weighted magnetic resonance imaging quality control studies: A review

“…Polysaccharide-based gels such as carrageenan have also been used for isotropic phantoms. 12 Polysaccharides have similar properties to human tissues, and are thus commonly used in MRI phantoms. They are simple sugar monomers with structural elements of cell walls containing intracellular spaces and connective tissue.…”

“…When gels are used for phantoms, their images are of better quality (with fewer distortions) as compared to images obtained with phantoms made of liquids due to the reduction of the macroscopic flow effect. 12 Anisotropic phantoms are more suitable and useful for diffusion tensor imaging than for diffusion-weighted imaging. This is owing to anisotropic phantoms' increased stability, which lowers imaging artifacts brought on by a drop in the macroscopic water flux when they are constructed from layers of an isotropic gel based on agar.…”

Diffusion processes modeling in magnetic resonance imaging

“…The phantom includes aqueous polymer solutions, similar to other devices [12,15] for modeling diffusion processes and typical ADC range. We also included reverse emulsions for modeling hindered and restricted diffusion, such as Cyc-Me and Cap-Me silicone oils with spectroscopic peaks corresponding to adipose tissue (-CH3/-CH2).…”