Browsing by Author "Junichiro Sakamoto"

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    Diffusion tensor imaging of the inferior alveolar nerve using 3T MRI: A study for quantitative evaluation and fibre tracking
    (2016-01-01) Shinya Kotaki; Junichiro Sakamoto; Kornkamol Kretapirom; Ngamsom Supak; Yasunori Sumi; Tohru Kurabayashi; Tokyo Medical and Dental University; Mahidol University; National Center for Geriatrics and Gerontology - National Institute for Longevity Sciences
    © 2016 The Authors. Published by the British Institute of Radiology. Objectives: Diffusion tensor imaging (DTI) can provide structural information and objective values for nerves. The aims of this study were to perform quantitative evaluation and fibre tracking of the normal inferior alveolar nerve (IAN) using DTI on 3.0-T MRI. Methods: DTI was applied to 92 IANs of 46 healthy volunteers. Circular regions of interest (ROIs) were placed on three different positions at the mandibular foramen, second molar and mental foramen of each nerve on apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps, and the ADC and FA of each ROI were measured. Differences in the values arising from the nerve positions were evaluated. Furthermore, fibre tracking of the IANs was performed by tractography, and the quality of visualization was evaluated. Results: There were no significant differences in the ADC and FA between the right and left sides regardless of the anteroposterior positions. Regarding differences arising from the anteroposterior measurement positions, the ADC and FA showed no significant differences (p > 0.017), except for the ADCs between the positions at the mandibular foramen and mental foramen in the left side (p = 0.0068). Overall, 70 (76%) of the 92 IANs could be visualized fully or partially by tractography. Conclusions: The ADC and FA of the IAN were successfully obtained from healthy volunteers using DTI and were confirmed to be symmetrical regardless of the measurement positions. DTI is a feasible technique for the quantitative evaluation and visualization of the IAN.
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    The intravoxel incoherent motion MRI of lateral pterygoid muscle: A quantitative analysis in patients with temporomandibular joint disorders
    (2017-01-01) Supak Ngamsom; Shin Nakamura; Junichiro Sakamoto; Shinya Kotaki; Akemi Tetsumura; Tohru Kurabayashi; Tokyo Medical and Dental University; Mahidol University
    © 2017 The Authors. Published by the British Institute of Radiology. Objectives: To quantitatively evaluate diffusion and perfusion status of lateral pterygoid muscle (LPM) in patients with temporomandibular joint disorder (TMD) by intravoxel incoherent motion (IVIM) imaging and to correlate with findings on temporomandibular joints (TMJs) by conventional MRI. Methods: 42 patients with TMD underwent MRI. To assess IVIM parameters, diffusionweighted imaging was obtained by spin-echo-based single-shot echoplanar imaging. Regions of interest were created on all diffusion-weighted images of the superior belly of the lateral pterygoid (SLP) and inferior belly of the lateral pterygoid (ILP) at b-values 0-500 s mm22. Then, IVIM parameters, diffusion (D) and perfusion (f) were calculated using biexponential fittings. The correlation of these values with conventional MRI findings on TMJs was investigated. Results: For SLP, the f parameter in TMJs with anterior disc displacement without reduction was significantly higher than that in normal ones (p =0.015). It was also significantly higher in TMJs with joint effusion than in those without (p =0.016). On the other hand, for both SLP and ILP, the D parameter significantly increased in TMJs with osteoarthritis compared with those without (p =0.015 and p =0.022, respectively). Conclusions: Pathological changes of LPM in patients with TMD may be quantitatively evaluated by IVIM parameters.