title: Diffusion-weighted imaging in cancer: physical foundations and applications of restriction spectrum imaging.
abstract: Diffusion-weighted imaging (DWI) has been at the forefront of cancer imaging since the early 2000s. Before its application in clinical oncology, this powerful technique had already achieved widespread recognition due to its utility in the diagnosis of cerebral infarction. Following this initial success, the ability of DWI to detect inherent tissue contrast began to be exploited in the field of oncology. Although the initial oncologic applications for tumor detection and characterization, assessing treatment response, and predicting survival were primarily in the field of neurooncology, the scope of DWI has since broadened to include oncologic imaging of the prostate gland, breast, and liver. Despite its growing success and application, misconceptions about the underlying physical basis of the DWI signal exist among researchers and clinicians alike. In this review, we provide a detailed explanation of the biophysical basis of diffusion contrast, emphasizing the difference between hindered and restricted diffusion, and elucidating how diffusion parameters in tissue are derived from the measurements via the diffusion model. We describe one advanced DWI modeling technique, called restriction spectrum imaging (RSI). This technique offers a more direct in vivo measure of tumor cells, due to its ability to distinguish separable pools of water within tissue based on their intrinsic diffusion characteristics. Using RSI as an example, we then highlight the ability of advanced DWI techniques to address key clinical challenges in neurooncology, including improved tumor conspicuity, distinguishing actual response to therapy from pseudoresponse, and delineation of white matter tracts in regions of peritumoral edema. We also discuss how RSI, combined with new methods for correction of spatial distortions inherent in diffusion MRI scans, may enable more precise spatial targeting of lesions, with implications for radiation oncology and surgical planning. See all articles in this Cancer Research section, "Physics in Cancer Research."
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California. nswhite@ucsd.edu.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: White
authors.forename: Carrie
authors.initials: C
authors.lastname: McDonald
authors.affiliation: Department of Psychiatry, University of California, San Diego, San Diego, California.
authors.forename: Carrie R
authors.initials: CR
authors.lastname: McDonald
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California.
authors.forename: Niky
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authors.lastname: Farid
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California.
authors.forename: Josh
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authors.lastname: Kuperman
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California.
authors.forename: David
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authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California.
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Schenker-Ahmed
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California.
authors.forename: Hauke
authors.initials: H
authors.lastname: Bartsch
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Rakow-Penner
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California.
authors.forename: Dominic
authors.initials: D
authors.lastname: Holland
authors.affiliation: Department of Pathology, University of California, San Diego, San Diego, California.
authors.forename: Ahmed
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authors.lastname: Shabaik
authors.affiliation: Department of Physics, University of Oslo, Oslo, Norway.
authors.forename: Atle
authors.initials: A
authors.lastname: Bjørnerud
authors.affiliation: Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Tuva
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authors.lastname: Hope
authors.affiliation: Department of Radiation Oncology, University of California, San Diego, San Diego, California.
authors.forename: Jona
authors.initials: J
authors.lastname: Hattangadi-Gluth
authors.affiliation: Department of Urology, University of California, San Diego, San Diego, California.
authors.forename: Michael
authors.initials: M
authors.lastname: Liss
authors.affiliation: Department of Urology, University of California, San Diego, San Diego, California.
authors.forename: J Kellogg
authors.initials: JK
authors.lastname: Parsons
authors.affiliation: Center for Theoretical and Applied Neuro-Oncology, Division of Neurosurgery, University of California, San Diego, San Diego, California.
authors.forename: Clark C
authors.initials: CC
authors.lastname: Chen
authors.affiliation: Department of Radiology, University of California, Los Angeles, Los Angeles, California.
authors.forename: Steve
authors.initials: S
authors.lastname: Raman
authors.affiliation: Department of Radiology, University of California, Los Angeles, Los Angeles, California.
authors.forename: Daniel
authors.initials: D
authors.lastname: Margolis
authors.affiliation: Department of Urology, University of California, Los Angeles, Los Angeles, California.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Reiter
authors.affiliation: Department of Urology, University of California, Los Angeles, Los Angeles, California.
authors.forename: Leonard
authors.initials: L
authors.lastname: Marks
authors.affiliation: Department of Neuosciences, University of California, San Diego, San Diego, California.
authors.forename: Santosh
authors.initials: S
authors.lastname: Kesari
authors.affiliation: Department of Radiation Oncology, University of California, San Diego, San Diego, California.
authors.forename: Arno J
authors.initials: AJ
authors.lastname: Mundt
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Kane
authors.affiliation: Department of Urology, University of California, San Diego, San Diego, California.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Kaine
authors.affiliation: Center for Theoretical and Applied Neuro-Oncology, Division of Neurosurgery, University of California, San Diego, San Diego, California.
authors.forename: Bob S
authors.initials: BS
authors.lastname: Carter
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California.
authors.forename: William G
authors.initials: WG
authors.lastname: Bradley
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, California. Department of Neuosciences, University of California, San Diego, San Diego, California.
authors.forename: Anders M
authors.initials: AM
authors.lastname: Dale
mesh_terms: D003952:Diagnostic Imaging / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D008495:Medical Oncology / Q000379:methods; D009369:Neoplasms / Q000175:diagnosis* / Q000473:pathology*