Lebin Wu

Decreased γ‐aminobutyric acid levels in the parietal region of patients with Alzheimer's disease

To determine whether there are in vivo differences of γ‐aminobutyric acid (GABA) levels in frontal and parietal regions of Alzheimers disease (AD) patients, compared with healthy controls using magnetic resonance spectroscopy (1H‐MRS).

Anatomical features of the cisternal segment of the oculomotor nerve: neurovascular relationships and abnormal compression on magnetic resonance imaging

OBJECT The object of this study was to assess the detailed anatomical features and vascular relationships of the cisternal segment of the oculomotor nerve, and to assess the utility of MR imaging in oculomotor nerve palsy caused by abnormal compression related to arteries and tumors. METHODS The anatomy of the oculomotor nerve was depicted using 3D Fourier transformation constructive interference in steady-state (CISS) MR imaging in 196 volunteers (392 total nerves), in 9 patients with paralysis of the oculomotor nerve, and in 1 preoperative patient with cholesteatoma in the pontine cistern. The vessels adjacent to the oculomotor nerve were detected and compared using 3D time-of-flight MR imaging. The 3D CISS multiplanar reconstruction (MPR) images of the oculomotor nerve in cadavers and in specimens from the cadavers were used to verify the oculomotor nerve shown in the 196 patients. The images were assessed with respect to the demonstration of the oculomotor nerve, the optimal display angles on MPR images, the visualized length of the nerve, neurovascular relationships, and abnormal compression caused by arteries and tumors. RESULTS Three-dimensional CISS MR imaging depicted the cisternal segment of the oculomotor nerve with certainty in 100% of the patients in the transverse, sagittal, and coronal planes. Three-dimensional CISS imaging of the oculomotor nerve in 196 volunteers revealed similar results corresponding to 3D CISS MPR images of cadavers and cadaver specimens. The maximum visualized length of the oculomotor nerve was 14.61 +/- 2.33 mm. The angle between the oculomotor nerve and the median sagittal plane was 24.48 +/- 4.57 degrees on the left and 24.48 +/- 5.07 degrees on the right. The posterior cerebral artery was observed to contact the oculomotor nerve in 216 (55.1%) of 392 nerves, and the superior cerebellar artery was observed to contact the oculomotor nerve in 231 (58.9%) of 392 nerves. The abnormal nerve compression in 9 patients with paralysis of the oculomotor nerve was displayed well in all patients. The adjacent relationship of the oculomotor nerve in 1 preoperative patient with cholesteatoma in the pontine cistern was also demonstrated clearly. CONCLUSIONS Use of 3D CISS sequences and 3D time-of-flight sequences enables accurate identification of the cisternal segment of the oculomotor nerve, neurovascular relationships, and abnormal compression caused by arteries and tumors.

Abdominal aortic intimal flap motion characterization in acute aortic dissection: assessed with retrospective ECG-gated thoracoabdominal aorta dual-source CT angiography.

Objectives To evaluate the feasibility of dose-modulated retrospective ECG-gated thoracoabdominal aorta CT angiography (CTA) assessing abdominal aortic intimal flap motion and investigate the motion characteristics of intimal flap in acute aortic dissection (AAD). Materials and Methods 49 patients who had thoracoabdominal aorta retrospective ECG-gated CTA scan were enrolled. 20 datasets were reconstructed in 5% steps between 0 and 95% of the R-R interval in each case. The aortic intimal flap motion was assessed by measuring the short axis diameters of the true lumen and false lumen 2 cm above of celiac trunk ostium in different R-R intervals. Intimal flap motion and configuration was assessed by two independent observers. Results In these 49 patients, 37 had AAD, 7 had intramural hematoma, and 5 had negative result for acute aortic disorder. 620 datasets of 31 patients who showed double lumens in abdominal aorta were enrolled in evaluating intimal flap motion. The maximum and minimum true lumen diameter were 12.2±4.1 mm (range 2.6∼17.4) and 6.7±4.1 mm (range 0∼15.3) respectively. The range of intimal flap motion in all patients was 5.5±2.6 mm (range 1.8∼10.2). The extent of maximum true lumen diameter decreased during a cardiac cycle was 49.5%±23.5% (range 12%∼100%). The maximum motion phase of true lumen diameter was in systolic phase (5%∼40% of R-R interval). Maximum and minimum intimal flap motion was at 15% and 75% of the R-R interval respectively. Intimal flap configuration had correlation with the phase of cardiac cycle. Conclusions Abdominal intimal flap position and configuration varied greatly during a cardiac cycle. Retrospective ECG-gated thoracoabdominal aorta CTA can reflect the actual status of the true lumen and provide more information about true lumen collapse. This information may be helpful to diagnosis and differential diagnosis of dynamic abstraction.

Diffusion-Weighted MR Neurography of Extremity Nerves With Unidirectional Motion-Probing Gradients at 3 T: Feasibility Study

OBJECTIVE The objective of our study was to show the feasibility and performance of diffusion-weighted MR neurography (MRN) of extremity nerves with unidirectional motion-probing gradients at 3 T. SUBJECTS AND METHODS Forty-seven healthy volunteers and 10 patients underwent diffusion-weighted MRN of extremity nerves with unidirectional motion-probing gradients (anterior-posterior direction only) on a 3-T unit. Images were displayed using a maximum-intensity-projection technique. Two radiologists blindly and independently evaluated the imaging quality of extremity nerves on diffusion-weighted MRN images using a 4-point grading scale, with 4 indicating excellent quality and 1 indicating poor quality, and evaluated the relation of the lesion to adjacent nerves in patients. RESULTS In volunteers, the long trajectories of major extremity nerves, including the radial, median, ulnar, sciatic, tibial, and common peroneal nerves, could be visualized 3D on diffusion-weighted MRN images. The mean imaging quality scores of all nerves for observers 1 and 2 were 3.68 ± 0.70 (SD) and 3.70 ± 0.66, respectively. Interobserver agreement was good (κ = 0.774). In patients, there was no discrepancy in imaging quality scores between observers. Scores of all nerves were 2-4 except in two patients with neurofibromatosis and one patient who underwent imaging soon after surgery. The extent of the lesions and the relationship of the lesions to the adjacent nerves were clearly depicted on diffusion-weighted MRN images of all patients. CONCLUSION This preliminary study shows that 3-T diffusion-weighted MRN with unidirectional motion-probing gradients is feasible for 3D visualization of major extremity nerves. Diffusion-weighted MRN may enable nerve depiction and allow assessment of the anatomic relationship between lesions with diffusion restriction and adjacent nerves.

MRI-guided stereotactic aspiration of brain abscesses by use of an optical tracking navigation system

Background Owing to the high risk of abscess drainage by craniotomy, imaging-guided stereotactic aspiration is considered an ideal choice in the management of brain abscesses. Interventional magnetic resonance imaging (MRI) represents a valuable technique for the treatment of brain abscess as a guiding modality. Purpose To evaluate the safety and efficacy of an interventional MRI system in performing the procedure. Material and Methods Thirteen brain abscesses in 11 patients were treated with percutaneous aspiration. All procedures were performed solely under the guidance of a 0.23-T open-configuration MRI scanner with optical tracking. Clinical and imaging follow-up was at 1 week, 1 month, 3 months, and 6 months. The changes of abscess, MRI features, and clinical symptoms were recorded. Procedure efficacy and safety were evaluated by success rate, procedure time, decrease of abscess, recovery rate, and complication. Descriptive statistical analysis was performed. Results MRI-guided stereotactic aspirations were performed successfully in 13/13 (100%) abscesses. The mean operating time was 70 min (range, 45–100 min). Follow-up MRI at 1 week after the procedure showed average reduction of abscesses by 60% (2.1/3.5). And the abscesses continued to get smaller by up to 89.7% (3.14/3.5) at 1-month follow-up. All cavities resolved at the end of the 6-month follow-up period. The recovery rate was 100% for fever, headache, vomiting, papilledema, meningismus, altered sensorium, 75% (3/4) for hemiparesis, and 83.3% (5/6) for epilepsy. There were no complications. Conclusion Punctures of brain abscesses with subsequent aspiration can be performed safely and efficiently by monitoring the procedure using an open interventional MRI system.

Magnetic resonance imaging-guided percutaneous biopsy of mediastinal masses: diagnostic performance and safety.

ObjectiveThe objective of this study was to evaluate the diagnostic performance and safety of magnetic resonance (MR) imaging–guided percutaneous mediastinal biopsy procedures using a 0.23-T open MR system with optical tracking navigation. Materials and MethodsA retrospective analysis of 59 participants (38 males and 21 females; mean age, 45 years; range, 16–73 years) who underwent MR imaging–guided percutaneous mediastinal biopsy procedures was performed. The access techniques included extrapleural (40 of 59; 67.8%) and transpulmonary (19 of 59; 32.2%) needle paths. Tissue sampling techniques included fine-needle aspiration (22 of 59; 37.3%) and core-needle biopsy (37 of 59; 62.7%). Histopathological analysis of surgical specimen and clinical and imaging follow-ups were used as the reference standard. The procedures were evaluated for technical success rate, number of biopsy passes, diagnostic performance, procedure time, and complications. ResultsTechnical success was achieved in 57 of the 59 procedures (96.6%). For the fine-needle aspiration, a mean of 3 passes (range, 2–4 passes) was performed. For the core-needle biopsy, a mean of 4 passes (range, 3–6 passes) was performed. Pathological and cytological analysis of biopsy specimens showed 41 of 57 malignant lesions (71.9%) and 16 of 57 benign lesions (28.1%), with a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 93.2% (41 of 44), 100% (13 of 13), 100% (41 of 41), 81.2% (13 of 16), and 94.7% (54 of 57), respectively. Procedure time was 30 minutes (range, 20–50 minutes). Mild hemoptysis occurred in 3 cases, and in 2 cases, a small pneumothorax occurred. ConclusionsMagnetic resonance imaging–guided biopsy of mediastinal masses has a high diagnostic performance and is safe for use in clinical practice.

The superiority of 3D-CISS sequence in displaying the cisternal segment of facial, vestibulocochlear nerves and their abnormal changes

OBJECTIVE To select the best imaging method for clinical otologic patients through evaluating 3D constructive interference of steady state (CISS) image quality in visualizing the facial, vestibulocochlear nerves (CN:VII-VIII) and their abnormal changes. METHODS The CN:VII-VIII as well as inner ear structures in 48 volunteers were examined using 3D-CISS and 3D turbo spin echo (TSE) sequences respectively, and displayed to the full at the reformatted and maximum intensity projection (MIP) images. The nerve identification and image quality were graded for the CN:VII-VIII as well as inner ear structures. Statistical analysis was performed using the Wilcoxin test, p<0.05 was considered significant. In addition, 8 patients with abnormality in facial or vestibulocochlear nerves were also examined using 3D-CISS sequence. RESULTS The identification rates for the cisternal segment of facial, vestibulocochlear nerves and corresponding membranous labyrinth were 100%. Abnormal changes of the facial or vestibulocochlear nerves were clearly shown in 8 patients, among them 1 was caused by bilateral acoustic neurinoma, 1 by cholesteatoma at cerebellopontine angle, 1 by arachnoid cyst, 1 by neurovascular adhesion, 4 by neurovascular compression. CONCLUSION With 3D-CISS sequence the fine structure of the CN:VII-VIII and corresponding membranous labyrinth can be clearly demonstrated; lesions at the site of cerebellopontine angle can also be found easily.

MRI-guided brain tumor cryoablation in a rabbit model.

To report the results of an animal trial exploring the feasibility of minimally invasive MR imaging‐guided rabbit brain tumor cryoablation with an argon‐based cryo‐unit.

Deep-gray nuclei susceptibility-weighted imaging filtered phase shift in patients with Wilson’s disease

Background:Susceptibility-weighted imaging (SWI) is a useful tool for evaluating brain paramagnetic mineralization. The aim of this study was to evaluate SWI filtered phase shift in brain gray nuclei of Wilson’s disease (WD).Methods:Twenty-three WD patients and 23 age- and gender-matched healthy controls underwent SWI. Phase values of bilateral brain gray nuclei were measured on corrected phase image of all subjects.Results:Compared with healthy controls, WD patients showed a trend of negative phase shift in all regions of interest, and significantly lower phase value was found in bilateral putamen (PU) (left P = 0.009, right P = 0.001), caudate (left P = 0.001, right P = 0.001), thalamus (TH) (left P < 0.001, right P < 0.001), red nucleus (left P = 0.031, right P = 0.049), and substantia nigra (left P = 0.003, right P = 0.047). The WD patients groups were divided into neurological, hepatic, and asymptomatic onset subgroups. And neurological onset patients had lower phase value than hepatic onset patients on bilateral PU (left P = 0.025, right P = 0.002) and TH (left P = 0.025, right P = 0.025).Conclusion:Abnormal negative phase value was significantly increased in brain gray nuclei of WD patients, giving evidence in vivo about paramagnetic mineralization accumulating in brain gray nuclei. The phase shift of SWI could be used as a potential biomarker to help in diagnosing and evaluating WD.

Diffusion-weighted MR neurography of median and ulnar nerves in the wrist and palm

AbstractObjectivesTo investigate the feasibility of diffusion-weighted magnetic resonance neurography (DW-MRN) in the visualisation of extremity nerves in the wrist and palm.MethodsThirty-two volunteers and 21 patients underwent imaging of the wrist and palm on a 3-T MR scanner. In all subjects, two radiologists evaluated the image quality on DW-MRN using a four-point grading scale. Kappa statistics were obtained for inter-observer performance. In volunteers, the chi-squared test was used to assess the differences in nerve visualisation on DW-MRN and axial fat-suppressed proton density weighted imaging (FS-PDWI).ResultsIn volunteers, the mean image quality scores for the median nerve (MN) and ulnar nerve (UN) were 3.71 ± 0.46 and 3.23 ± 0.67 for observer 1, and 3.70 ± 0.46 and 3.22 ± 0.71 for observer 2, respectively. The inter-observer agreement was excellent (k = 0.843) and good (k = 0.788), respectively. DW-MRN provided significantly improved visualisations of the second and the third common palmar digital nerves and three branches of UN compared with FS-PDWI (P < 0.05). In patients, the mean image quality scores for the two observers were 3.24 ± 0.62 and 3.10 ± 0.83, inter-observer performance was excellent (k = 0.842).ConclusionsDW-MRN is feasible for improved visualisation of extremity nerves and their lesions in the wrist and palm with adequate image quality, thereby providing a supplementary method to conventional MR imaging.Key points• DW-MRN provides adequate image quality for wrist and palm neurography • DW-MRN performs similarly to FS-PDWI in nerve visualisation at the wrist • DW-MRN provides improved visualisation of small nerves in the palm • DW-MRN serves as a supplementary method to evaluate peripheral neuropathies