Tag: Preoperative evaluation

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Generation and applications of synthetic computed tomography images for neurosurgical planning

J Neurosurg 141:742–751, 2024

CT and MRI are synergistic in the information provided for neurosurgical planning. While obtaining both types of images lends unique data from each, doing so adds to cost and exposes patients to additional ionizing radiation after MRI has been performed. Cross-modal synthesis of high-resolution CT images from MRI sequences offers an appealing solution. The authors therefore sought to develop a deep learning conditional generative adversarial network (cGAN) which performs this synthesis.

METHODS Preoperative paired CT and contrast-enhanced MR images were collected for patients with meningioma, pituitary tumor, vestibular schwannoma, and cerebrovascular disease. CT and MR images were denoised, field corrected, and coregistered. MR images were fed to a cGAN that exported a “synthetic” CT scan. The accuracy of synthetic CT images was assessed objectively using the quantitative similarity metrics as well as by clinical features such as sella and internal auditory canal (IAC) dimensions and mastoid/clinoid/sphenoid aeration.

RESULTS A total of 92,981 paired CT/MR images obtained in 80 patients were used for training/testing, and 10,068 paired images from 10 patients were used for external validation. Synthetic CT images reconstructed the bony skull base and convexity with relatively high accuracy. Measurements of the sella and IAC showed a median relative error between synthetic CT scans and ground truth images of 6%, with greater variability in IAC reconstruction compared with the sella. Aerations in the mastoid, clinoid, and sphenoid regions were generally captured, although there was heterogeneity in finer air cell septations. Performance varied based on pathology studied, with the highest limitation observed in evaluating meningiomas with intratumoral calcifications or calvarial invasion.

CONCLUSIONS The generation of high-resolution CT scans from MR images through cGAN offers promise for a wide range of applications in cranial and spinal neurosurgery, especially as an adjunct for preoperative evaluation. Optimizing cGAN performance on specific anatomical regions may increase its clinical viability.

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Evaluation of spinal cord compression and hyperintense intramedullary lesions on T2-weighted sequences in patients with cervical spondylotic myelopathy using flexion-extension MRI protocol

Evaluation of spinal cord compression and hyperintense intramedullary lesions on T2-weighted sequences in patients with cervical spondylotic myelopathy using flexion-extension MRI protocol

The Spine Journal 15 (2015) 668–674

Acquired cervical stenosis is caused by the combination of disc protrusion, facet joint degeneration, hypertrophy of the ligamentum flavum, and osteophyte formation. Although these mechanical factors seem to play an important role in the pathogenesis of myelopathy, the role of dynamic factors has been suggested by many authors. Based on these results, dynamic magnetic resonance imaging (MRI) was proposed to improve diagnostic techniques in patients with cervical myelopathy.

PURPOSE: The purpose of the study was to evaluate the importance of dynamic MRI in the assessment of cervical canal stenosis and to determine the percentage of levels in which cord impingement was only visible in the extension MRI and the percentage of cases in which hyperintense intramedullary lesions (HILs) were identified only on the flexion MRI.

STUDY DESIGN: This is a retrospective case series study.

PATIENT SAMPLE: Patients with spondylotic myelopathy who had dynamic cervical MRI at our department from October 2005 to February 2007 were included.

MATERIALS AND METHODS: Fifty-one consecutive patients with spondylotic myelopathy had MRI in the neutral, flexion, and extension positions of the cervical spine.

OUTCOME MEASURES: The following entities were evaluated: canal stenosis (the evaluation of the stenosis was based on the Muhle classification) and the presence or absence of HILs.

RESULTS: Two hundred fifty-five levels were evaluated in the three positions. At each level, the stages in extension were higher than the stages in neutral and flexion positions (p<.05). From C3 to C6, around 22.5% of Stage 3 levels in the extension were Stage 1 in the neutral position. In flexion, HILs are better identified than in neutral and extension positions (p<.05). In 10% of the patients, HILs were identified only in the flexion T2-weighted sequence.

CONCLUSIONS: Extension MRI helps to identify significant cervical canal stenosis that is partially or completely absent on neutral and flexion MRI and to determine the exact number of levels to decompress surgically. Flexion MRI permits better visualization of HILs on T2-weighted sequences.

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