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Effects of treatment on the abdomen and pelvis
Published in Anju Sahdev, Sarah J. Vinnicombe, Husband & Reznek's Imaging in Oncology, 2020
DWI used in combination with T2WI combines the strength of the high sensitivity of DWI with anatomical information from T2WI. Studies have shown that using image fusion of these two sequences (T2-DWI) offers the highest accuracy in differentiating between residual or recurrent tumour and post-treatment effects (Figure 39.1) (8). Apparent diffusion coefficient (ADC) values can be used as an objective tool, with recurrent or residual tumour having a lower ADC. However, individual ADC value cut-offs cannot be relied upon because of considerable overlap between malignant and non-malignant conditions. DWI should always be interpreted in combination with other conventional MRI sequences rather than in isolation (9).
Biomarkers for Organophosphate Poisoning: Physiological and Pathological Responses
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
Arik Eisenkraft, Avshalom Falk, Kevin G. McGarry Jr.
As the diffusion of water in the tissue is restricted, the obtained diffusion coefficient is an apparent diffusion coefficient (ADC), which is a measure of the diffusivity of water in the tissue environment. The underlying principle of quantitative determination of ADC is outlined in the legend to Figure 21.5. It should be pointed out that the determination of ADC requires acquisition of at least two images—one without diffusion-sensitizing gradients and another with diffusion-sensitizing gradients.
Quantitative imaging to guide mechanism-based modeling of cancer
Published in Ruijiang Li, Lei Xing, Sandy Napel, Daniel L. Rubin, Radiomics and Radiogenomics, 2019
David A. Hormuth, Matthew T. McKenna, Thomas E. Yankeelov
DW-MRI is an imaging technique that has been used to assess cellularity (the number of cells within a region) in vivo. Briefly, DW-MRI is sensitive to the diffusion of water molecules within a sample. The diffusion of water in free solution is described by random, Brownian, motion which is due to thermal energy (Einstein 1905). In tissue, however, water molecules are no longer freely diffusing, but are restricted by cells, macromolecules, and extracellular structures which serve to reduce the diffusion coefficient of water molecules. In DW-MRI, this reduced diffusion coefficient of water is termed the apparent diffusion coefficient (ADC). Typically, a pulsed gradient diffusion experiment is used to calculate the ADC in each voxel. Several studies have showed correlation between ADC and cellularity (Sugahara et al. 1999; Anderson et al. 2000; Guo et al. 2002; Humphries et al. 2007; Jiang et al. 2016) and correlation between ADC and extracellular space (Barnes et al. 2015). Other DW-MRI-based approaches such as VERDICT (Panagiotaki et al. 2014) or IMPULSED (Jiang et al. 2016) have been developed to provide estimates of cellularity and cell size. A more technical description of DW-MRI is found in Chapter 5, while a review of its application to cancer can be found in (Koh & Collins 2007). Figure 21.1a displays a representative ADC map which shows a higher ADC at the center of the tumor indicative of a region of necrosis.
Radiological analysis of orbital lymphoma histological subtypes
Published in Orbit, 2023
Valerie Juniat, Cassie A. Cameron, Kelsey Roelofs, Nicholas Bajic, Sandy Patel, James Slattery, Garry Davis, Daniel Rootman, Dinesh Selva
Lymphoma may present with a wide array of imaging features beyond the classic ‘moulding to the globe’ appearance. CT and MRI are helpful as a means to differentiate orbital lymphomas from other tumours, lymphoproliferative disorders and inflammation.5–18 Sequencing tools such as apparent diffusion coefficient/diffusion-weighted imaging (ADC/DWI) ratios can be generally useful in differentiating cellular lesions such as lymphoma, although these are not specific enough for lymphoma subtyping.19–21 Further, there is little available understanding regarding the differential appearance of orbital lymphoma based on histologic subtype. This study was performed to evaluate the diversity of radiological features in orbital lymphoma, and to determine possible histological-radiological associations.
New magnetic resonance imaging sequences for fibrosis assessment in Crohn’s disease: a pilot study
Published in Scandinavian Journal of Gastroenterology, 2022
Bénédicte Caron, Valérie Laurent, Freddy Odille, Silvio Danese, Gabriela Hossu, Laurent Peyrin-Biroulet
Recently, Avila et al. showed that magnetic resonance elastography could be a reliable tool for detecting intestinal fibrosis in CD [13]. IVIM and T1 mapping sequences could also be used as new tools to diagnose intestinal fibrosis. Djelouah et al. evaluated the role of additional diffusion-weighted imaging (DWI) to a standard MRE including GBCA-enhanced imaging for the diagnosis of endoscopic recurrent CD after ileocolonic resection [14]. Adding DWI to standard contrast-enhanced MRE did not significantly increase performances for the detection of CD-related endoscopic recurrence after surgery [14]. The thresholds of apparent diffusion coefficient (ADC) values for differentiating active inflammatory, non-active and fibrotic lesions are not established, yet [4]. ADC mean values calculated on DWI-MRE may be associated to 1-year conservative medical therapy of patients with CD without extramural complications, indicating patients who have a low intramural total burden of both acute inflammatory cells and/or fibrotic tissue [4]. IVIM and T1 mapping sequences could be evaluated for assessing fibrosis after ileocolonic resection in patients with CD.
Predicting neoadjuvant chemoradiotherapy response with functional imaging and liquid biomarkers in locally advanced rectal cancer
Published in Expert Review of Anticancer Therapy, 2022
Trang Thanh Pham, Stephanie Lim, Michael Lin
DWI is the most studied functional MRI modality for prediction of CRT response in rectal cancer. Apparent diffusion coefficient (ADC) measures water diffusion through tissue, and has an inverse relationship with tissue cellularity. Viable tumor cells have low ADC values, whereas necrotic tumor cells have high ADC values. Single-center small prospective DWI studies assessing mean ADC in general have shown that a lower ADC before CRT [46–48], higher ADC after CRT [49–52], and a greater percentage increase in ADC over time-points [46–49,52–57] was associated with good response to CRT in rectal cancer. Patients with a high ADC before CRT are hypothesized to have radio-resistant tumor necrosis, leading to poorer CRT response. Selected prospective DWI studies for response prediction in rectal CRT are shown in Table 1. A meta-analysis of 6 DWI studies, compared DWI with standard morphologic T2-weight MRI, and found that ADC outperformed T2-weighted imaging in assessment of response after CRT [28]. Our group assessed tumor heterogeneity by performing a histogram analysis of ADC quantiles (10th, 25th, 50th, 75th, 90th), skewness and kurtosis before, during, and after-CRT. We found that ADC 75th and 90th quantile values were significantly higher in responders than nonresponders to CRT [50].