MRI Assessment of Vestibulocochlear nerve disease Diagnosed by Videonystagmography (VNG), and Pure- Tone Audiometry (PTA) Testsرسالة ماجستير

Abstract

The purpose of this study was to investigate the role and sensitivity of magnetic resonance imaging (MRI) in the diagnoses of the vestibular disorders, comparing the MRI to vestibular function tests including videonystagmography (VNG), and pure-tone audiometry (PTA) test, with positive results and reported as a vestibular disorder. Addiitonally, to determine image quality of MRI sequences used by the two vendors by quantifying the image quality metrics (IQM), including signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) and to make comparisons between the different sequences. Methodology The sample included 49 patients aged 7 - 77 years, 20 males and 29 females. Of the 49 patients who underwent an MRI exam, 32 had previously had vestibular function tests performed with positive findings. Three radiologists reviewed the MRI examinations of the patients; in addition to recording the measurements of vestibulocochlear nerve (VCN) diameter. A statistical measure of mean, standard deviation, and range were calculated. Diagnostic reports from the three radiologists were assessed by intraclass correlation coefficient (ICC) for all data results. The measurement of the vestibulocochlear nerve length was made on balanced fast field echo-150 slices (B_FFE_150 Slices) and fast imaging employing steady-state acquisition (FIESTA) on both sides from the axial images, and the two diameters measured on the sagittal reformatted image formed from the T2-weighted three-dimensional driven VI equilibrium techniques (T2W_3D_DRIVE) or FIESTA sequence to calculate the cross sectional area (CSA). Measurement of SNR was performed by the Difference Method for both in-vivo and phantom, whereas CNR was calculated by estimating the ratio of mean of signal to the SD of the background which represents the noise. Radiologist Diagnostic Results Radiologist’s diagnostic reports showed the presence of pathology in 53.1% of all cases based on the MRI examinations. The results of the vestibular function tests showed a 58.8% with a central, and a 41.2% have a peripheral vestibular dysfunction. The mean values for VCN length were 19.02mm. The CSA mean for all patients, positive cases, negative instances were 1.50mm², 1.58mm², 1.43mm², respectively. Result for SNR and CNR In Phantom measurements of General Electric Healthcare (GE Healthcare) sequences, coronal-T1-FSE-Thin sequence has the highest value for SNR of 85.97 dB, and coronal T2- weighted fast spin-echo (Cor T2-FSE) has the highest CNR of 161.32 dB. Philips Healthcare a higher SNR value for T2-weighted fast field echo (T2-FFE), which is 162.97dB, and fluid attenuated inversion recovery –long repetition time (FLAIR-Long TR) has the highest CNR value, which is 27.59 dB. In vivo, the study's findings suggest that when the three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA) sequence was utilized for imaging, the GE Healthcare VII MRI had the best signal-to-noise ratio (SNR), with an SNR value of 11.21 dB. The T2- weighted fast spin-echo (T2-FSE) sequence, on the other hand, generated the highest contrast-to-noise ratio (CNR) result, measuring 161.32 dB. With an SNR of 17.36 dB, Philips Healthcare MRI device produced the greatest SNR rating when using the T1-weighted fast field echo ( T1-FFE) sequence, and fast imaging employing steady-state acquisition (FIESTA) recorded the highest CNR value of 322.26 dB. Conclusion The study suggests that parasagittal high resolution T2 weighted (DRIVE, constructive interference in steady state (CISS), and FIESTA) MRI can be used to measure the vestibulocochlear nerve, which is thicker in patients with positive MRI results. MRI is the preferred examination for recognizing vestibular nerve disorders, and most diagnosed disorders match central vestibular dysfunction on VNG test results. The study found that sequences with high SNR and CNR in Philips Healthcare and GE Healthcare MRI provided comparable image quality and excellent diagnostic capabilities. Understanding these sequences is crucial for assessing vestibular function test results and differentiating vestibular disorders. Videonystagmography (VNG) remains a crucial tool within the etiologic diagnosis of patients complaining of vertigo, even within the post-MRI period. Sequences that have a high SNR and CNR in Philips Heathcare were TI –FFE and FIESTA respectively, but in GE MRI the better sequences for getting a high SNR and CNR were 3D FIESTA and T2-FSE respectively.