Quantitative diffusion tensor imaging of corticospinal tract: Initial experience.

Objective: Diffusion Tensor Imaging (DTI) and fiber tractography are a relatively new magnetic resonance imaging technique that can provide white matter architectures. In this pilot study, we use these techniques to quantify and evaluate the integrity of white matter tract in a group of subjects with and without lesions involving the corticospinal tract. Methods: Ten subjects (7 patients and 3 controls) who underwent conventional MRI and DTI were retrospectively recruited. DTI data was analyzed with a multiple ROI approach on a workstation to isolate corticospinal tract and obtain fractional anisotropy (FA) and directional average mean diffusivity (Dav). Comparison of these values between affected and unaffected corticospinal tract was done using a Mann-Whitney U test. Results: FA values of the affected side were significantly lower than the unaffected side (comparing affected side of patient versus control and affected side of patient versus unaffected side of patient). Whereas, Dav value was significantly higher only when compared with the affected side of the patient to the control group. Comparison of the unaffected side of the patient versus control and the left side of control versus right side of control showed no statistical differences. Four out of five patients with residual neurological deficit had a higher mean difference of FA. Conclusion: Pathological change of corticospinal tract from various diseases can be quantitatively measured by DTI and fiber tractography. This technique might be useful for early disease detection, to predict disease prognosis or quantitative follow-up of disease progression.

Pre-operative evaluation with magnetic resonance imaging in tetralogy of fallot and pulmonary atresia with ventricular septal defect.

BACKGROUND: Preoperative evaluation of patients with pulmonary atresia and ventricular septal defect (PA/ VSD) are generally done by echocardiogram and cardiac catheterization. The authors' objective of the present study was to compare the findings of Gadolinium (Gd) enhanced cardiac magnetic resonance angiography (MRA) with cardiac catheterization. MATERIAL AND METHOD: Patients who had PA/VSD were prospectively evaluated using cardiac catheterization and cardiac MRA. A branch of the pulmonary arteries was divided into: main pulmonary artery (MPA), left and right branch pulmonary artery (LPA & RPA), major aortopulmonary collateral arteries (MAPCA) and minor collaterals. Each study was interpreted blindly. The agreement of findings was compared using Kappa statistics. RESULTS: There were 43 patients who received both cardiac catheterization and cardiac MRI within a 2 month period The average age was 13.8 +/- 8.4 (2-30) years-old. There was an agreement among measurement of both MPA and LPA & RPA with Kappa statistics of more than 0.8. Gd-enhanced MRA was able to identify more branches of MAPCA when compared to cardiac catheterization. CONCLUSIONS: The results of the present study indicate that Gd-enhanced MRA is a feasible, fast and accurate technique for identification of all sources of pulmonary blood supply in patients with complex pulmonary atresia. The present study was a noninvasive alternative to cardiac catheterization. Gd-enhanced MRA can better delineate small (minor) branches of collateral.

Accuracy of visual assessment in the detection and quantification of myocardial scar by delayed enhancement magnetic resonance imaging.

BACKGROUND: Delayed-enhancement magnetic resonance imaging (DE-MRI) is now a standard for the detection of myocardial scar and viability. Standard analysis needs expensive software. OBJECTIVE: To determine the accuracy of visual assessment in the detection and quantification of myocardial scar by DE-MRI technique. MATERIAL AND METHOD: The authors enrolled 32 patients with coronary artery disease (CAD) as documented by coronary angiography (CAG) and left ventricular dysfunction. All patients underwent cardiac magnetic resonance imaging for the assessment of global and regional myocardial function and DE-MRI. The presence and amount of scar in each myocardial segment was assessed by standard method. Visual assessment was performed by two methods: 1) visual drawing of the boundary of the hyperenhancement region and calculation of percentages of scar in an individual segment; 2) visual estimation of grading of hyperenhancement area from 0 (no scar) to 4 (> 75% scar). The agreement for scar detection and correlation of scar quantification for individual segments were evaluated. RESULTS: Thirty-one of 32 patients in the present study had myocardial scar. One thousand four hundred and thirty two myocardial segments were analyzed. Visual detection of myocardial scar has an excellent level of agreement with standard method of scar (Kappa = 0.963 and 0.952, p<0.001 for visual method I and II). Visual method I and II has an accuracy of 98.2% and 97.6% respectively in the detection of myocardial scar compared to standard method. Percentages of myocardial scar in each myocardial segment by visual method I correlate very well with standard method (Intraclass Correlation Coefficient = 0.885). Visual grading of amount of myocardial scar also has an excellent correlation with standard method (Spearman rank correlation coefficient = 0.934). CONCLUSION: Visual assessment of myocardial scar is accurate for the detection and quantification of scar.

The accuracy of magnetic resonance venography for diagnosis of dural sinus thrombosis.

A retrospective study of 24 patients who underwent magnetic resonance venography (MRV) was performed. The MRV was using a 3D-PC technique and thick-slab multiplanar reconstruction. Four patients underwent conventional angiography. There were 4 males and 20 females with an age range of 8-71 years. The MRV was considered as positive for dural sinus thrombosis (DST) in 8 patients and negative in 16 patients. There were 2 false positive in the MRV.The sensitivity of MRV is 100%,specificity 88%,positive predictive value 75% and negative predictive value 100%.We concluded that MRV is a valuable screening method for DST. One pitfall concerning the use of MRV is that a false positive interpretation may occur due to hypoplasia of the transverse sinus which is a normal variant.

A comparison of MR myelography of brachial plexus injury with CT myelography and conventional myelography.

The purpose of study is to assess the accuracy of magnetic resonance myelography (MRM) of the cervical spine in patients with preganglionic Brachial Plexus Injury (BPI) by using CT myelography as the gold standard and comparing this with routine conventional myelography. Patients with a clinically diagnosis of Brachial plexus Injury were studied (9 males, 1 female, aged 16 - 42 years old) [mean age = 25.4 years old]). All patients had undergone clinical evaluation by an orthopedic surgeon and five patients had had additional somatosensory evoked potentials (SEP) performed. All patients were investigated by conventional myelography, computed tomography myelography (CTM) and magnetic resonance myelography (MRM). We used CT myelography as the gold standard and the accuracy of MRM and myelography were assessed in relative to this. The sensitivity in detecting a pseudomeningocele by MRM is 100% and the sensitivity in detecting nerve root abnormality is 90% at the level of the C5, C6 roots and 100% for the C7, C8, T1 roots. MR Myelography had many advantages over conventional and CT myelography which include the absence of radiation and the lack of need for intrathecal injection of contrast medium.