Can measuring hippocampal atrophy with a fully automatic method be substantially less noisy than manual segmentation over both 1 and 3 years?

To quantify the "segmentation noise" of several widely used fully automatic methods for measuring longitudinal hippocampal atrophy in Alzheimer's disease and compare the results to the segmentation noise of manual segmentation over both 1 and 3 years. The segmentation noise of 5 longitudinal hippocampal atrophy measurement methods was quantified, including checking its Gaussianity, using 264 subjects from the ADNI1 back-to-back (BTB) data set over both 1 year and 3 year intervals. The segmentation methods were FreeSurfer 5.3.0 both cross sectional and longitudinal, FreeSurfer 6.0.0 longitudinal, MAPS-HBSI and FSL/FIRST 5.0.8. The BTB manual segmentation of 75 ADNI subjects from a previous study provided the manual distributions for comparison. All methods, including the manual segmentation, violated the Gaussianity assumption. Two methods, FreeSurfer 6.0.0 and MAPS-HBSI, had a segmentation noise substantially less than a surrogate for manual segmentation. FreeSurfer 5.3.0 longitudinal was confirmed as a surrogate for manual segmentation. The violation of the Gaussian assumption by the segmentation methods assessed, including manual, suggests results of previous studies that assumed Gaussian statistics without confirmation may need review. Fully automatic FreeSurfer 6.0.0 and MAPS-HBSI both have lower segmentation noise than manual requiring less than two thirds of the subjects to detect the same treatment effect

Multislice T1 Relaxation Time Measurements in the Brain Using IR-EPI: Reproducibility, Normal Values, and Histogram Analysis in Patients with Multiple Sclerosis

Purpose: To perform T1 measurements using inversion recovery (IR) echoplanar imaging (EPI) to evaluate reproducibility, normal values, and T1 histogram analysis as a measure of disease progression in multiple sclerosis (MS) patients. Materials and Methods: Multislice IR-EPI was performed in 10 controls and 36 MS patients. Region-of-interest (ROI) and T 1 histogram analysis were performed on T1 maps and compared to hypointense T1 lesions and brain atrophy in MS patients. Results: Coefficient of variation (COV) varied from 1.6% to 4.9%. Callosal normal (appearing) white matter (N(A)WM) showed the lowest and cortical gray matter the highest T1 values. T1 histogram analysis in controls showed a sharp WM peak centered on a T1 value of 729 msec (range = 679-765) with extension into a shoulder of higher T1 values. In MS patients, a shift toward higher T1 values (mean = 788 msec, range = 700-957) with a lower relative peak amplitude was present, predominantly resulting from T1 prolongation in NAWM. T1 histogram parameters strongly related to hypointense T1 lesion volume and brain atrophy in MS patients. Conclusions: IR-EPI provides a reproducible method to obtain T1 values in the brain. Regional variation in T1 values is present in N(A)WM of volunteers and MS patients. Since T1 histogram parameters reflect changes in NAWM and correlate with conventional measures of disease burden in MS patients, T 1 histogram analysis may provide a global measure of disease progression in MS

Serial isotropic three-dimensional fast FLAIR imaging: Using image registration and subtraction to reveal active multiple sclerosis lesions

OBJECTIVE. Image registration and subtraction to detect the change of disease burden in multiple sclerosis on serial MR images should benefit from the use of high-resolution isotropic voxels. We compared 1.2-mm isotropic three-dimensional (3D) fast fluid-attenuated inversion recovery (FLAIR) images with standard 3-mm two-dimensional spin-echo images for the detection of new or enlarging lesions in longitudinal studies. SUBJECTS AND METHODS. Serial MR images were obtained at baseline, month 6 (n = 20), and month 7 (n = 16). For the half-yearly intervals, subtracted 3D FLAIR images and T2-weighted spin-echo images were compared. For the monthly intervals, subtracted 3D FLAIR images were compared with triple-dose contrast-enhanced T1-weighted spin-echo images. New, enlarging, and enhancing lesions were marked in consensus by two radiologists. RESULTS. At the half-yearly intervals, 3D FLAIR imaging detected more new or enlarging lesions than T2-weighted spin-echo imaging, both at the initial interpretation (80 vs 52; p 0.05). CONCLUSION. Isotropic 3D FLAIR imaging holds great promise for the detection of new or enlarging lesions in multiple sclerosis using registration and subtraction techniques certainly at longer intervals

Neuronal damage in T1-hypointense multiple sclerosis lesions demonstrated in vivo using proton magnetic resonance spectroscopy

Hypointense T1 lesions in multiple sclerosis patients correlate with axonal loss at autopsy and biopsy. We evaluated the chemical substrate of hypointense T1 lesions by using in vivo proton magnetic resonance spectroscopy, and analyzed the spectroscopic correlate of increased T1- relaxation time measurements. Localized proton magnetic resonance spectroscopy and T1-relaxation time measurements were performed in lesions, selected on T1-weighted spin-echo magnetic resonance images according to degree of hypointensity, in normal appearing white matter (NAWM) and in normal white matter of controls. In NAWM, prolongation of T1-relaxation time and a decrease in N-acetylaspartate (NAA) were present, compared with normal white matter. Severely hypointense lesions showed a lower concentration of NAA and creatine compared with NAWM and a lower concentration of NAA compared with isointense to mildly hypointense lesions. NAA concentration correlated with degree of hypointensity of lesions and with T1-relaxation time within the spectroscopic voxel. Our results provide the first in vivo evidence of axonal damage in severely hypointense T1 lesions in multiple sclerosis patients, T1-relaxation time correlates with the concentration of NAA in both multiple sclerosis lesions and NAWM, indicating that this parameter deserves further evaluation to monitor disease progression

Sensitivity and reproducibility of volume change measurements of different brain portions on magnetic resonance imaging in patients with multiple sclerosis

The course of multiple sclerosis (MS) can be monitored by measuring changes in brain volume, but consensus is still lacking on the best strategy to be adopted. We compared the reproducibility and sensitivity of volume measurements from different brain portions for detecting changes on magnetic resonance imaging (MRI) in patients with MS. T1-weighted MRI of the brain was performed in 50 patients with relapsing-remitting MS at study entry and after an average follow-up of 18.4 months. Using a semiautomated technique for brain parenchyma segmentation, the volumes of the following brain portions were measured: (a) the whole brain (whole-brain volume, WBV), (b) the seven slices rostral to the velum interpositum (seven-slice volume, SSV), (c) the central slice of the image set (central-slice volume, CSV) and (d) the infratentorial regions (infratentorial-brain volume, IBV). All these measurements were carried out by a single observer and were repeated twice on ten randomly selected scans to test the intra-observer reproducibility using the four strategies. At follow-up there was a significant decrease in all the measures of brain volume (P ranged from 0.002 to < 0.001). The univariate correlations between changes in WBV, SSV, CSV and IBV were all statistically significant, with the exception of that between changes in CSV and IBV; r values ranged from 0.34 (for the WBV/IBV correlation) to 0.80 (for the WBV/SSV correlation). The mean intra-observer coefficient of variations were 1.9 % for WBV, 1.5 % for SSV, 2.9 % for CSV and 2.2% for IBV measurements. The measurement of volume on a portion of brain selectively including the regions in which MS pathology is more diffuse is as reliable and sensitive to disease-related changes as that on the whole brain, with significant time saving for processing

MR venography of multiple sclerosis

BACKGROUND AND PURPOSE: The distribution of multiple sclerosis (MS) lesions in the brain follows a specific pattern, with most lesions in the periventricular regions and in the deep white matter; histopathologic studies have shown a perivenous distribution. The aim of this study was to illustrate these distribution patterns in vivo using high-resolution MR venography. METHODS: Seventeen MS patients underwent MR imaging at 1.5 T. Venographic studies were obtained with a 3D gradient-echo technique. MS lesions were identified on T2-weighted images, and their shape, orientation, and location were compared with the venous anatomy on the venograms. RESULTS: The use of contrast material facilitated the visualization of small veins and increased the number of veins seen. A total of 95 MS lesions could be identified on both the T2-weighted series and the venograms; a central vein was visible in all 43 periventricular lesions and in all but one of the 52 focal deep white matter lesions. The typical ovoid shape and orientation of the long axis of the MS lesions correlated well with the course of these veins. CONCLUSION: With MR venography, the perivenous distribution of MS lesions in the brain can be visualized in vivo. The venous anatomy defines the typical form and orientation of these lesions

Adaptation of lateral pterygoid and anterior digastric muscles after surgical mandibular advancement procedures in different vertical craniofacial types:A magnetic resonance imaging study

Objective. Surgical mandibular advancement procedures induce major adaptations of jaw-closing muscles. In this study, adaptation of antagonist muscles, the lateral pterygoid (LPM) and anterior digastric (DigA) muscles, was evaluated. Study design. Eighteen adult patients with mandibular retrognathia and individually varying vertical craniofacial dimensions were treated with bilateral sagittal split osteotomies (BSSO), in some cases combined with a Le Fort I osteotomy (LF Bimax). The sample was divided into 1 short-face (SF, n = 7) and 2 long-face groups (LF BSSO, n = 3; and LF Bimax, n = 8). Pre- and postoperative maximum cross-sectional areas (CSA) and volumes were compared in these groups. Results. Postoperatively, CSA and volume of LPM increased in BSSO cases and decreased in bimaxillary cases. Inconsistent increases and decreases of CSA and volume of DigA were seen in all groups. Conclusions. The LPM became larger in SF and LF BSSO patients and smaller in LF Bimax patients. The DigA adapted unpredictably

Magnetic resonance image registration in multiple sclerosis: Comparison with repositioning error and observer-based variability

Purpose: To study the use of image registration in the analysis of multiple sclerosis (MS) lesion volume and compare this with repositioning error and observer-based variability. Materials and Methods: The normalized mutual information (NMI) algorithm is evaluated in an accuracy study using a phantom, followed by a validation study on magnetic resonance (MR) data of MS patients. Further, using scan-rescan MR data, the effect of registration on MS lesion volume compared with repositioning error and observer based variability is assessed. Results: The registration accuracy was near perfect in the phantom study, while the in vivo validation study demonstrated an accuracy on the order of 0.2-0.3 mm. In the scan-rescan study, quantification accounted for 15.6% of the relative variance, repositioning for 44,4%, and registration for 40,0%. Conclusion: NMI resulted in robust and accurate alignment of MR brain images of MS patients. Its use in the detection of changes in MS using large serial MR imaging (MRI) data warrants future evaluation