Diffusion Tensor Magnetic Resonance Imaging Finding of Discrepant Fractional Anisotropy Between the Frontal and Parietal Lobes After Whole-Brain Irradiation in Childhood Medulloblastoma Survivors: Reflection of Regional White Matter Radiosensitivity?

Qiu, Deqiang; Kwong, Dora L.W.; Chan, Godfrey Chi Fung; Leung, LP; Khong, Pek‐Lan

doi:10.1016/j.ijrobp.2007.04.041

Cited by 75 publications

(71 citation statements)

References 34 publications

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“…Postnatal normal brain development is known to be temporally accompanied with gradual and local tissue morphological changes in both WM and GM that can lead to subtle changes in water diffusion (80,(83)(84)(85)90,(93)(94)(95)(96)(97), thus providing an effective biological platform to evaluate the sensitivity of DKI. An in vivo DKI study has been recently performed to examine the changes in various diffusivity and kurtosis parameters at different postnatal time points (33,60).…”

Section: Monitoring Postnatal Brain Maturation By Dki and Conventionamentioning

confidence: 99%

MR diffusion kurtosis imaging for neural tissue characterization

2010

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In conventional diffusion tensor imaging (DTI), water diffusion distribution is described as a 2nd-order three-dimensional (3D) diffusivity tensor. It assumes that diffusion occurs in a free and unrestricted environment with a Gaussian distribution of diffusion displacement, and consequently that diffusion weighted (DW) signal decays with diffusion factor (b-value) monoexponentially. In biological tissue, complex cellular microstructures make water diffusion a highly hindered or restricted process. Non-monoexponential decays are experimentally observed in both white matter and gray matter. As a result, DTI quantitation is b-value dependent and DTI fails to fully utilize the diffusion measurements that are inherent to tissue microstructure. Diffusion kurtosis imaging (DKI) characterizes restricted diffusion and can be readily implemented on most clinical scanners. It provides a higher-order description of water diffusion process by a 2nd-order 3D diffusivity tensor as in conventional DTI together with a 4th-order 3D kurtosis tensor. Because kurtosis is a measure of the deviation of the diffusion displacement profile from a Gaussian distribution, DKI analyses quantify the degree of diffusion restriction or tissue complexity without any biophysical assumption. In this work, the theory of diffusion kurtosis and DKI including the directional kurtosis analysis is revisited. Several recent rodent DKI studies from our group are summarized, and DKI and DTI compared for their efficacy in detecting neural tissue alterations. They demonstrate that DKI offers a more comprehensive approach than DTI in describing the complex water diffusion process in vivo. By estimating both diffusivity and kurtosis, it may provide improved sensitivity and specificity in MR diffusion characterization of neural tissues.

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Section: Monitoring Postnatal Brain Maturation By Dki and Conventionamentioning

confidence: 99%

MR diffusion kurtosis imaging for neural tissue characterization

2010

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“…Several studies have reported correlation between changes in DTI indices and decreased neurocognitive functionality such as intelligence quotient scores and processing speeds (11)(12)(13)(14), suggesting DTI as a potential imaging biomarker for treatmentrelated neurotoxicity. A notable finding in these studies is that radiation dose-effect is fiber tract-or region-dependent (15)(16)(17)(18). If an association with observed neurotoxicity can be established, then knowledge of differential radiation sensitivity would be valuable in treatment planning to protect more vulnerable brain regions.…”

Section: Introductionmentioning

confidence: 99%

Effects of Surgery and Proton Therapy on Cerebral White Matter of Craniopharyngioma Patients

Hua

Ogg

et al. 2014

International Journal of Radiation Oncology*Biology*Physics

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Purpose-To determine the radiation dose-effect on the structural integrity of cerebral white matter in craniopharyngioma patients receiving surgery and proton therapy.Methods and Materials-Fifty-one patients (aged 2.1-19.3 years) with craniopharyngioma underwent surgery and proton therapy in a prospective therapeutic trial. Anatomical magnetic resonance images acquired after surgery but before proton therapy were inspected to identify white matter structures intersected by surgical corridors and catheter tracks. Longitudinal diffusion tensor imaging (DTI) was performed to measure microstructural integrity changes in cerebral white matter. Fractional anisotropy (FA) derived from DTI was statistically analyzed for 51 atlasbased white matter structures of the brain to determine radiation dose-effect. FA in surgeryaffected regions in the corpus callosum was compared to that in its intact counterpart to determine whether surgical defects affect radiation dose-effect.Results-Surgical defects were seen most frequently in the corpus callosum because of transcallosal resection of tumors and insertion of ventricular or cyst catheters. The longitudinal DTI data indicated reductions in FA 3 months after therapy, which was followed by a recovery in most white matter structures. A greater FA reduction was correlated with a higher radiation dose in 20 white matter structures, indicating a radiation dose-effect. The average FA in the surgery- Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript affected regions before proton therapy was smaller (P =0.0001) than that in their non-surgery affected counterparts with more intensified subsequent reduction of FA (P=0.0083) after therapy, suggesting that surgery accentuated the radiation dose-effect.Conclusions-DTI data suggest that mild radiation dose-effects occur in patients with craniopharyngioma receiving surgery and proton therapy. Surgical defects present at the time of proton therapy appear to accentuate the radiation dose-effect longitudinally. This study supports consideration of pre-existing surgical defects and their locations in proton therapy planning and studies of treatment effect.

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“…15,16 Quantitative evaluation of changes in normal-appearing white matter (NAWM) of brain tumor patients receiving RT have been described using DTI metrics-i.e., fractional anisotropy (FA) and mean diffusivity (MD)-which are sensitive to changes in the interstitial space volume and constituents in NAWM beyond the visible intensity changes on conventional MR imaging. [15][16][17][18][19] Signifi cant reduction in FA and an increase in MD in the brains of children (aged 3-14 years treated for a medulloblastoma) and adults (with diverse brain tumors) who received combinations of chemotherapy and RT have been reported. 17,18 Also, a differential effect on the frontal lobe compared to the parietal lobe has been reported using FA.…”

Section: Introductionmentioning

confidence: 99%