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