Quantitative imaging using MRI
Ruijiang Li, Lei Xing, Sandy Napel, Daniel L. Rubin in Radiomics and Radiogenomics, 2019
Diffusion-weighted imaging (DWI) is an MRI technique that is sensitive to the microscopic, thermally induced self-diffusion of water molecules within a system [16,17]. In biological tissues, water movement is neither completely free nor random due to the constant physical and chemical interactions that water molecules have with other macromolecules, intracellular organelles, cell membranes, and vascular structures. The differing patterns of water diffusion in various tissues give rise to the specific image contrast in a diffusion-weighted image. For example, necrotic tissues that have lost cellular integrity allow for greater mobility of water molecules and will exhibit lower signals on diffusion-weighted images. Conversely, tissues with increased cellularity (e.g., tumors) have numerous boundaries that impede the diffusion of water and will exhibit high signal intensities. A quantitative analysis of DWI data returns estimates of the apparent diffusion coefficient (ADC), and in well-controlled situations, the ADC has been shown to correlate inversely with tissue cellularity [18,19]. Thus, DWI provides indirect functional information about the cytoarchitecture of specific biological tissues, which could aid in distinguishing between normal and diseased tissues.
Management of Locally Advanced and Recurrent Rectal Cancer
Peter Sagar, Andrew G. Hill, Charles H. Knowles, Stefan Post, Willem A. Bemelman, Patricia L. Roberts, Susan Galandiuk, John R.T. Monson, Michael R.B. Keighley, Norman S. Williams in Keighley & Williams’ Surgery of the Anus, Rectum and Colon, 2019
Several authors have reported on the utility of adding diffusion-weighted imaging to MRI to further enhance the accuracy and diagnostic capability of MRI. In a study by Lanbregts et al., 42 patients with suspected LRRC underwent both MRI and diffusion-weighted imaging.76 Two radiologists then independently reviewed the images, and the results between MRI and diffusion-weighted imaging were compared, as was the agreement between the two radiologists. Although the authors did not find diffusion-weighted imaging useful in improving the diagnostic accuracy of MRI, it did improve the specificity of MRI and, therefore, the agreement between radiologists.76 In another study by Grosu et al., diffusion-weighted imaging was found to facilitate the distinction between post-treatment fibrosis and local recurrence.77 It is, however, important to note that the collective experience with diffusion-weighted imaging seems rather limited at this point.
Neuroimaging
John W. Scadding, Nicholas A. Losseff in Clinical Neurology, 2011
Diagnostic neuroimaging is central to modern neurology practice. Magnetic resonance imaging (MRI) is the investigation of choice in most circumstances and in routine clinical use produces images that resemble gross pathology. MRI also offers physiological information beyond anatomical imaging. Diffusion weighted imaging has rapidly become established in clinical use, whereas other advanced applications such as spectroscopy and functional magnetic resonance imaging (fMRI) still have only limited usefulness outside research. Computed tomography (CT) remains the workhorse of emergency imaging. Most vascular imaging is now performed non-invasively although catheter angiography still has a role in selected patients, mainly following intracranial haemorrhage.
Intimate partner violence and brain imaging in women: A neuroimaging literature review
Published in Brain Injury, 2023
Jirapat Likitlersuang, David H. Salat, Catherine B. Fortier, Katherine M. Iverson, Kimberly B. Werner, Tara Galovski, Regina E. McGlinchey
Diffusion-weighted imaging is another domain of MRI that can be used to create the contrast image of the diffusion of water molecules within the brain tissue. The diffusion tensor imaging (DTI) is one of the DWI sequences that can evaluate the white matter tractography (3D modeling) of nerve fibers as well as microstructural tissue properties. Specifically, the degree in anisotropy or degree of directionality of water molecules movement within the brain can be extracted. Fractional anisotropy (FA) is a scalar value from 0 to 1 and in diffusion imaging described the fiber density, axonal diameter, and myelination in the brain white matter. A value of one indicates fluid flow in one direction without any restriction (anisotropic), while a value closer to zero indicates leaky axon and unrestricted flow in all directions (isotropic). In other words, the reduced FA value may indicate an alteration of the integrity of the white matter tracts (Figure 2).
Diagnostic accuracy of diffusion-weighted imaging in differentiating glioma recurrence from posttreatment-related changes: a meta-analysis
Published in Expert Review of Anticancer Therapy, 2022
Xiaoli Du, Qian He, Boli Zhang, Na Li, Xuewen Zeng, Wenbo Li
Diffusion weighted imaging (DWI) is the only method that can measure the diffusion of water molecules in living tissues at early disease stages. In recent years, the recurrence of glioma has been identified by quantitative analysis of the average apparent diffusion coefficient (ADC) value [6], cumulative ADC square analysis [7] and parameter response diagram [8]. Meta-analyses of DWI have been conducted to differentiate glioma recurrence and the posttreatment response. For example, Zhang H et al. included 9 Chinese and English studies until October 2014, comprising 284 patients, proving the advantage of DWI in distinguishing glioma recurrence and radioactive encephalitis [9]. Tsakiris C et al. included 24 English studies published before October 2019, comprising 900 patients, proving that DWI was superior in terms of sensitivity and specificity for perfusion weighted imaging (PWI) in distinguishing glioma recurrence and pseudoprogression [10]. Our study is a meta-analysis on DWI to differentiate between postoperative recurrence of glioma and posttreatment-related changes, guide clinical treatment and improve patient prognosis.
Clinical presentation of a neuropsychiatric lupus patient with symmetrical basal ganglia lesions containing cytotoxic oedema cores surrounded by vasogenic oedema
Published in Modern Rheumatology Case Reports, 2020
Syoko Tsubouchi, Haeru Hayashi, Koichiro Tahara, Kayo Ishii, Takuya Yasuda, Yusuke Yamamoto, Takahiro Mizuuchi, Hiroaki Mori, Mayu Tago, Eri Kato, Tetsuji Sawada
Magnetic resonance imaging (MRI) is a useful radiographic procedure for detecting CNS abnormalities even at a subclinical level, with a sensitivity to capture 40 to 75% of abnormalities in NPSLE [12]. Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping are MRI sequences that can evaluate tissue microstructure based on the differences of water molecules in Brownian motion (diffusion) influenced by various brain pathologies [10]. These approaches are useful for evaluating high intensity lesions on T2-weighted (T2W) brain MRI images, which either represent ischaemic lesions due to embolism, vasculitis and microangiopathic lesions, or represent non-ischaemic perilesional oedemas [13]. High intensity lesions on T2W brain MRI images can be divided into cytotoxic and vasogenic oedemas based on signal intensity on DWI and ADC images [14]. Cytotoxic oedema is an intracellular oedema caused by energy-metabolic abnormalities in the brain that lead to dysfunction of membrane ion channels and yield low ADC and high DWI signals. On the other hand, vasogenic oedema, which is an extracellular oedema caused by disruption of blood brain barrier due to endothelial damage, exhibits the profile of high ADC and iso to low DWI.
Related Knowledge Centers
- Contrast
- Diffusion
- In Vivo
- Macromolecule
- Tissue
- Tractography
- Mri Sequence
- Biological Membrane
- White Matter
- Spin–Lattice Relaxation