Visualization of the greater and lesser occipital nerves on three-dimensional double-echo steady-state with water excitation sequence

Visualization of the Extracranial Branches of the Trigeminal Nerve Using Improved Motion-Sensitized Driven Equilibrium-Prepared 3D Inversion Recovery TSE Sequence

BACKGROUND AND PURPOSE

Visualization of the extracranial trigeminal nerve is crucial to detect nerve pathologic alterations. This study aimed to evaluate visualization of the extracranial trigeminal nerve using 3D inversion recovery TSE with an improved motion-sensitized driven equilibrium (iMSDE) pulse.

MATERIALS AND METHODS

In this prospective study, 35 subjects underwent imaging of the trigeminal nerve using conventional 3D inversion recovery TSE, 3D inversion recovery TSE with an iMSDE pulse, and contrast-enhanced 3D inversion recovery TSE. The visibility of 7 extracranial branches of the trigeminal nerve, venous/muscle suppression, and identification of the relationship between nerves and lesions were scored on a 5-point scale system. In addition, SNR, nerve-muscle contrast ratio, nerve-venous contrast ratio, nerve-muscle contrast-to-noise ratio, and nerve-venous contrast-to-noise ratio were calculated and compared.

RESULTS

Images acquired with iMSDE 3D inversion recovery TSE had significantly higher nerve-muscle contrast ratio, nerve-venous contrast ratio, and nerve-to-venous contrast-to-noise ratio (all P < .001); improved venous/muscle suppression and clearer visualization of the trigeminal nerve branches except the ophthalmic nerve than with conventional 3D inversion recovery TSE (all P < .05). Compared with contrast-enhanced 3D inversion recovery TSE, images acquired with iMSDE 3D inversion recovery TSE had significantly higher SNR, nerve-muscle contrast ratio, and nerve-to-venous contrast-to-noise ratio (all P < .05), and demonstrated comparable diagnostic quality (scores ≥3) of the maxillary nerve, mandibular nerve, inferior alveolar nerve, lingual nerve, and masseteric nerve (P > .05). As for the identification of the relationship between nerves and lesions, iMSDE 3D inversion recovery TSE showed the highest scores among these 3 sequences (all P < .05).

CONCLUSIONS

The iMSDE 3D inversion recovery TSE is a promising alternative to conventional 3D inversion recovery TSE and contrast-enhanced 3D inversion recovery TSE for visualization of the extracranial branches of trigeminal nerve in clinical practice.

Is 3T MR nerve-bone fusion imaging a viable alternative to MRI-CBCT to identify the relationship between the inferior alveolar nerve and mandibular third molar

OBJECTIVES

To investigate the feasibility of MRI nerve-bone fusion imaging in assessing the relationship between inferior alveolar nerve (IAN) / mandibular canal (MC) and mandibular third molar (MTM) compared with MRI-CBCT fusion.

MATERIALS AND METHODS

The MRI nerve-bone fusion and MRI-CBCT fusion imaging were performed in 20 subjects with 37 MTMs. The Hausdorff distance (HD) value and dice similarity coefficient (DSC) was calculated. The relationship between IAN/MC and MTM roots, inflammatory, and fusion patterns were compared between these two fused images. The reliability was assessed using a weighted κ statistic.

RESULTS

The mean HD and DSC ranged from 0.62 ~ 1.35 and 0.83 ~ 0.88 for MRI nerve-bone fusion, 0.98 ~ 1.50 and 0.76 ~ 0.83 for MRI-CBCT fusion. MR nerve-bone fusion had considerable reproducibility compared to MRI-CBCT fusion in relation classification (MR nerve-bone fusion κ = 0.694, MRI-CBCT fusion κ = 0.644), direct contact (MR nerve-bone fusion κ = 0.729, MRI-CBCT fusion κ = 0.720), and moderate to good agreement for inflammation detection (MR nerve-bone fusion κ = 0.603, MRI-CBCT fusion κ = 0.532, average). The MR nerve-bone fusion imaging showed a lower ratio of larger pattern compared to MR-CBCT fusion (16.2% VS 27.3% in the molar region, and 2.7% VS 5.4% in the retromolar region). And the average time spent on MR nerve-bone fusion and MRI-CBCT fusion was 1 min and 3 min, respectively.

CONCLUSIONS

Both MR nerve-bone fusion and MRI-CBCT fusion exhibited good consistency in evaluating the spatial relationship between IAN/MC and MTM, fusion effect, and inflammation detection.

CLINICAL RELEVANCE

MR nerve-bone fusion imaging can be a preoperative one-stop radiation-free examination for patients at high risk for MTM surgery.

MRI of the intraorbital ocular motor nerves on three-dimensional double-echo steady state with water excitation sequence at 3.0 T

PURPOSE

To explore the capability of three-dimensional double-echo steady state with water excitation sequence (3D-DESS-WE) to determine the intraorbital ocular motor nerves (IOMN).

MATERIALS AND METHODS

A 3.0 T scanner was applied to investigate 30 healthy volunteers based on the 3D-DESS-WE sequence. Dunnett t test was conducted to evaluate the signal intensity (SI) of the left oculomotor nerve (CNIII), frontal white matter, cerebrospinal fluid (CSF), and lateral rectus (LR). The oculomotor nerve's detectability, trochlear nerve (CNIV), and abducens nerve (CNVI) were evaluated independently by two observers. The average assessment scores were determined, and interobserver variability for these nerves' detectability was determined using a weighted kappa analysis.

RESULTS

The SI of CNIII is similar to that of the frontal white matter (t = 2.26, P > 0.05), lower than the CSF, and higher than the LR (t = 3.81, - 3.45, P < 0.05). The average scores of the superior division of CNIII and the branch to medial rectus (MR), inferior rectus (IR), inferior oblique (IO), CNIV, and CNVI were 3.01, 3.07, 3.78, 2.98, 2.88, and 3.97, respectively. The interobserver variability was excellent (κ = 0.83-1.00).

CONCLUSION

The 3D-DESS-WE sequence shows an ability to detect the IOMN course in healthy volunteers effectively.