Diffusion parameters of the core of cingulum are associated with age-related ventricular enlargement: a diffusion tensor tractography study.

PURPOSE: To evaluate the influence of the size of lateral ventricles on diffusion parameters of the normal cingulate bundle. METHODS: Eighty normal subjects (17-55 years) underwent MRI at 3 T including diffusion tensor imaging. Superior (SC) and inferior (IC) cingulum were analyzed separately. Mean diffusivity (MD0.30) and fractional anisotropy (FA0.30) were measured by tractography at FA threshold 0.30; further diffusion parameters were analyzed by tractography-based core analysis in volumes of 3.0 cm3/1.5 cm3. The diffusion parameters were correlated with corresponding cross-sectional coronal areas of lateral ventricles. The analysis was performed also separately for young (17-34) and middle-aged (35-55) subjects. RESULTS: FA0.30 values did not correlate with ventricular size, but there was a weak negative correlation (r = - 0.225) between MD0.30 of SC and ventricular size. In all controls and in the older age group, ventricular size correlated positively with core FA of SC (r = 0.262/r = 0.391) and negatively with mean diffusivity (r = - 0.324/r = - 0.303) and radial diffusivity (λ2: r = - 0.238/r = - 0.277; λ3: r = - 0.353/r = - 0.424) of the core of SC. In the younger age group, only the mean diffusivity of SC correlated with ventricular size (r = - 0.273). Ventricular size was not associated with axial diffusivity. The core parameters of IC did not correlate with ventricular size. CONCLUSION: Radial diffusivity of the core of cingulum decreases in age-dependent ventricular enlargement, which can be related to tissue compaction with stretching of axons and diminution of extracellular spaces. The phenomenon, which is reverse to the assumed effect of age-related myelin loss, can influence on DTI parameters in middle-aged subjects.

Interpretation of magnetic resonance imaging in the chronic phase of traumatic brain injury: what is missed in the original reports?

PRIMARY OBJECTIVE: To find eventual differences in detecting the late stage TBI findings in MRI between two neuroradiologists and to compare the results with the original reports. METHODS AND PROCEDURE: Two neuroradiologists with different levels of experience (R1 and R2) reviewed 89 cranial 1.5 T MRI examinations of patients with clinically evident TBI. They recorded the nature, location and side of the finding and stated their view of traumatic axonal injury (TAI). The original reports were reviewed accordingly. MAIN OUTCOMES AND RESULTS: TAI was reported as being evident or possible in 51 patients with TBI. However, only 30 (76%) of these concerned the same patients. R1 reported more contusion findings, but both found the same number of spot-like haemorrhages. The most striking difference was in the reporting of localized atrophy. R1 reported atrophy in 51/178 (29%) frontal lobes, whereas R2 in 14/178 (8%). Many of the findings were missed in the original reports. CONCLUSIONS: The interpretation of TBI findings in late stage MRI yields significant variability between neuroradiologists. This may endanger diagnostics and lead to false treatment decisions and medico-legal problems. Standardized quantitative imaging analysis programs and advances in MRI technology should be utilized to improve radiological TBI diagnosis.

Diffusion tensor tractography of the uncinate fasciculus: pitfalls in quantitative analysis due to traumatic volume changes.

PURPOSE: To demonstrate the sensitivity of quantitative diffusion tensor tractography to traumatic injury of the uncinate fasciculus (UF), and to evaluate the effect of volume changes on the accuracy of quantitative analysis. MATERIALS AND METHODS: Diffusion tensor imaging (DTI) was performed at 3 T for 110 patients with traumatic brain injury (TBI) and 60 control subjects. Volume, mean diffusivity (MD), and mean fractional anisotropy (FA) of the UF were measured by means of tractography. The influence of FA threshold on mean FA values was determined and the values were further related to the tract volume. RESULTS: In patients with TBI, 16% of the volumes and 29% of the FA values were decreased and 25% of the MD values were increased (>2 SD from the mean of controls). Small tracts (6% of trajectories) often had normal mean FA, but low volume-related FA values. Large UFs often had decreased mean FA values, but normal volume-related central values (3% of trajectories). CONCLUSION: Posttraumatic FA and MD changes and volume reductions are common in the tractography of UF. Trauma-induced volume changes can cause misleading whole-tract mean FA values. Therefore, additional volume-based analysis of the central part is beneficial for clinical assessment.

Reliability of diagnosis of traumatic brain injury by computed tomography in the acute phase.

The purpose of our study was to determine the accuracy and reliability of the computed tomographic (CT) diagnosis of acute traumatic brain injury (TBI) and to evaluate the inter-observer variation of CT reports of acute TBI between two experienced neuroradiologists and a neuroradiologist in training. One hundred cranial CT examinations of suspected TBI were chosen randomly from those taken during 1 year at a university central hospital, with institutional ethics committee approval. Two neuroradiologists and one neuroradiologist in training read the scans independently and were blinded to the clinical data. The original reports of radiologists on call, who were either radiology residents or general radiologists, were reviewed. Main outcome measures were false-positive and false-negative findings, and the congruency of different readers' reports. The reference standard was a group consensus formed by three neuroradiologists. Radiologists on call missed a significant number of brain contusions (67%), but with regard to intraventricular and subarachnoid hemorrhages and edema, their accuracy was moderate. They reported practically no false-positive brain contusion findings, and all readers found subdural hemorrhages reliably. The two experienced neuroradiologists had the smallest number of false-negative findings, but their reports differed significantly. Of the other neuroradiologists' mistakes, 75% were false-positive, nearly all of these concerning contusions, whereas the other made random mistakes. In conclusion, there was a marked variation between readers in the detection of brain contusion findings on acute brain CT. Experience increased accuracy, yet even between the reports of the most experienced readers, there were marked differences.