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NINA BRANDSTACK26.06.2013
QUANTITATIVE DIFFUSION TENSOR TRACTOGRAPHY OF LONG ASSOCIATION TRACTS IN PATIENTS WITH TRAUMATIC BRAIN INJURY WITHOUT FINDINGS IN ROUTINE MRIBRANDSTACK NINA, KURKI TIMO, AND TENOVUO OLLI.RADIOLOGY APRIL 2013 267:1 231-239
Quantitative Diffusion-Tensor Tractography Can Detect Posttraumatic Abnormalities
That Are Not Depicted at Conventional MR
Conventional MRI
Superior to CT in the detection of intraparenchymal traumatic lesions
Often normal even in TBI cases with persistent symptoms
True injury/ other disorder?-> Treatment
Medicolegal consequences
Our study: Materials and methods
106 consecutive (from July 2008 to December 2011) clinical
subjects with TBI without abnormalities on routine MRI (age 16-56 years)
62 demographically- matched control subjects
DTI at 3T (Achieva; Philips Medical Systems, Best, the Netherlands) was performed (number of excitations 2, 15 gradient encoding directions)
Deterministic DTT (FiberTrak package, Philips Medical Systems) was performed by using an FA threshold of 0.15 and a turning angle threshold of 27° to terminate the tracking process
The tracts were defined with 2-3 free hand inclusion ROIs and 1-4 exclusion ROIs
Materials and methods
Volume, ADC and FA of the SLF, IFOF, UF, SC, TC, AF, and ILF were measured
Statistical analyses were based on repeated-measures ANCOVA
Sex, age, time between injury and imaging, trauma mechanism and severity of TBI were considered as covariates for the tests
Results
In controls, tract volumes showed large variability while FA and ADC values showed small variability
In several tracts, mean FA values correlated negatively with
the respective volumes
In subjects with TBI, FA values were reduced in both UFs, both IFOFs, and in the right ILF compared with controls (p<0.05)
Diffusivity was increased in half of the tracts
The tract volumes were not significantly reduced
Reproducibility
ICC , Bland-Altman reliability analysisFA/ turning angle threshold: 0.15/60° (light
blue),0.15/27° (blue), 0.30/27° (green)Volume-based FA and ADC analysis in the central
part of the tract with two pretermined sizes: 3cm³ (purple), 1cm³ (red)
Reproducibility -results
For the tract-based methods, intra-rater and inter-rater reliabilities of FA and ADC measurements were excellent.
Between-scan reproducibility was good or excellent
in 127/130 of the measurements.
In our study with relatively few subjects (n=10), neither the turning angle threshold (27°/60°) nor FA threshold (0.15/0.30) had a systematic influence on reproducibility
Conclusions
QDTT is able to show posttraumatic FA and ADC abnormalities in subjects with normal routine MRI in several association tracts, most commonly in the UF
The tract-based FA and ADC measurements are highly reproducible
The large variability of normal tract volumes and the dependence of mean FA values on volume can decrease the accuracy of the method
Thank You