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Toru Chikui Last modified date:2019.06.24

Associate Professor / Division of Maxillofacial Diagnostic and Surgical Sciences
Department of Dental Science
Faculty of Dental Science


Graduate School
Undergraduate School


E-Mail
Phone
092-642-6407
Fax
092-642-6410
Academic Degree
PhD
Field of Specialization
Oral Diagnostic Science
Outline Activities
Research: 1.The quantitative analyses of the MRI image in the head and neck lesions.2. Head and neck radiology .3. Quantitative MRI of the head and neck region.
Education: 1. Lecture: Oral and Maxillofacial Radiology (Fifth-grade student), Early exposure (Freshman)2. Practice: Oral and Maxillofacial Radiology (radiation physics and clinical radiology) (5th-6th grade student)
Socail activities: 1. Lecture to the JICA members
Research
Research Interests
  • New model analysis applied to the diffusion weighted images with multiple b values
    keyword : diffusion weighted image, statistical model
    2019.04~2021.04.
  • The analysis of the distribution of MRI contrast medium
    keyword : MRI contrast medium, head and neck
    2006.03~2016.04The analysis of the distribution of MRI contrast medium..
  • MRI image of the masticatory muscle.
    keyword : MRI, diffusion, ADC, tractography
    2009.04~2012.03.
  • Measurment of T1, T2 and ADC of the head and neck lesion. Estimation of diffusion parameters of the head and neck region.
    keyword : MRI, T1 value, T2 value, ADC
    2006.04Measurment of T1, T2 and ADC of the head and neck lesion..
  • Early detection of metastatic cervical lymph nodes.
    keyword : cervical lymph node, diagnostic imaging
    1998.04~2003.12Early detection of metastatic cervical lymph nodes.
Academic Activities
Reports
1. 筑井 徹, 大賀 正浩, 北本 江梨奈, 白石 朋子, 川野 真太郎, 吉浦 敬, 吉浦 一紀, Quantification of Diffusion and Permeability of MRI in the Head and Neck Region, Journal of Radilogy and Radiation Therapy, 2014.03, Diffusion Weighted Image (DWI) has various roles such as tissue characterization, the prediction and monitoring of the response to treatment and
differentiation of recurrent tumors from post-therapeutic changes. The malignant tumors have a lower ADC compared to benign lesions. Follow-up of early response to cancer treatment is reflected in an ADC increase in the primary tumor and nodal metastases; whereas nonresponding lesions tend to reveal only
a slight increase or even a decrease in ADC during follow-up. However, there are many limitations regarding the performance of DWI in the head and neck
region, therefore, many attempts has been performed to overcome the flaws of the diffusion-weighted single-shot-echo planar imaging.
The pharmacokinetic analyses of dynamic contrast enhanced MRI (DCE-MRI) can provide physiological condition of the tissue, and Tofts and Kermode
Model has been applied to the head and neck region. Some researchers have used it for the prediction and monitoring of the tumor response to cancer therapy.
The general consensus is that the early changes of these parameters during the early phase after the treatment are useful for the interpretation of the response
to the treatment. However, the parameters reported in the literature vary considerably; therefore, it is difficult to compare the values of the parameters among research groups.
Both DWI and the pharmacokinetic analysis of the DCE-MRI have shown a wide range of potential benefits in this region, but more comparative studies with established scan techniques and the quantification of the data are required.
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2. Chikui T, Obara M, Simonetti AW, Ohga M, Koga S, Kawano S, Matsuo Y, Kamintani T, Shiraishi T, Kitamoto E, Nakamura K, Yoshiura K., The Principal of Dynamic Contrast EnhancedMRI, theMethod of Pharmacokinetic Analysis, and Its Application in the Head and Neck Region., Int J Dent, 2012.11, Many researchers have established the utility of the dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) in the differential diagnosis in the head and neck region, especially in the salivary gland tumors. The subjective assessment of the pattern of the time-intensity curve (TIC) or the simple quantification of the TIC, such as the time to peak enhancement (T(peak)) and the wash-out ratio (WR), is commonly used. Although the semiquantitative evaluations described above have been widely applied, they do not provide information on the underlying pharmacokinetic analysis in tissue. The quantification of DCE-MRI is preferable; therefore, many compartment model analyses have been proposed. The Toft and Kermode (TK) model is one of the most popular compartment models, which provide information about the influx forward volume transfer constant from plasma into the extravascular-extracellular space (EES) and the fractional volume of EES per unit volume of tissue is used in many clinical studies. This paper will introduce the method of pharmacokinetic analysis and also describe the clinical application of this technique in the head and neck region..
Papers
1. WannakamonPanyarak, Toru Chiku, Yasuo Yamashita, Takeshi Kamitani, Kazunori Yoshiura., Image Quality and ADC Assessment in Turbo Spin-Echo and Echo-Planar Diffusion-Weighted MR Imaging of Tumors of the Head and Neck, Academic Radiology, https://doi.org/10.1016/j.acra.2018.11.016, 2018.12, Rationale and Objectives

We aimed to compare the distortion ratio (DR), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) between turbo spin-echo (TSE)-diffusion-weighted imaging (DWI) and echo-planar imaging (EPI)-DWI of the orofacial region and prove the usefulness of TSE-DWI for the differential diagnosis of orofacial lesions.
Materials and methods

The DR, SNR, and CNR of both sequences were compared in 42 cases. Then, the apparent diffusion coefficient (ADC) of various orofacial lesions obtained by TSE-DWI was investigated in 143 lesions.
Results

In the first study, 38 of 42 cases were analyzed. TSE-DWI showed a significantly lower DR (p < 0.05) and higher SNR and CNR than EPI-DWI (p < 0.05), indicating the superiority of TSE-DWI. In the second study, 114 cases (79.3%) were successfully analyzed. When lesions were divided into cysts, benign tumors, squamous cell carcinoma, malignant lymphoma, and other malignant tumors (OT), significant differences were observed in all pairs of lesions (p < 0.05) except squamous cell carcinoma and OT (p = 0.877). The area under the curve for distinguishing benign from malignant tumors was 0.80 with a cutoff ADC of 1.29 × 10-3 mm²/s.
Conclusion

TSE-DWI produced better quality images than EPI-DWI. TSE-DWI yields the high possibility of obtaining ADC in the orofacial region, and this value was considered useful for the differential diagnosis of orofacial lesions..
2. Chikui T, Yamashita Y, Kise Y, Saito T, Okamura K, Yoshiura KBr J Radiol.., Estimation of proton density fat fraction of the salivary gland., Br J Radiol, doi: 10.1259/bjr.20170671., 91, 1085, 2018.05, OBJECTIVE:
Our first objective was to prove the validity of the six-point Dixon method for estimating the proton density fat fraction (PDFF) of the salivary gland. The second objective was to estimate the salivary gland PDFF using Dixon method to evaluate the pathological conditions.
METHODS:
At first, 12 volunteers underwent two types of sequences: single-voxel magnetic resonance spectroscopy and the Dixon method and the PDFFs obtained by the two methods were compared. Next, a total of 67 individuals [normal, n = 46; Sjögren's syndrome (SS), n = 11; and IgG4-related dacryoadenitis and sialadenitis (IgG4-DS), n = 4, parotitis, n = 6] were enrolled to estimate the parotid gland (PG) and submandibular gland (SMG) PDFF using the Dixon method.
RESULTS:
This volunteer study demonstrated excellent correlation between two methods (R2 = 0.964, slope = 1.05). In the normal group, the PG-PDFF was correlated with the weight and body mass index (BMI) (ρ = 0.38, p = 0.0085; and ρ = 0.63, p < 0.0001). The SMG-PDFF was also correlated with the weight, BMI, and serum triglyceride (ρ = 0.37, p = 0.0067; ρ = 0.42, p = 0.0022; and ρ = 0.35, p = 0.024). The PG-PDFF of the SS group (48.2 ± 15.1%) was higher than that of any other groups; however, no significant difference was found due to the wide overlap. The SS group (39.0 ± 26.14%) also had significantly higher SMG-PDFF than the normal group (8.9 ± 5.4%), p < 0.0001) and IgG4-DS group (3.8 ± 2.3%), p = 0.020).
CONCLUSION:
The Dixon method is a feasible method for estimating the PDFF and demonstrates fat accumulation in SMG in the SS group. Advances in knowledge: The PDFF obtained by the Dixon method is helpful for understanding the salivary gland pathological condition..
3. Yoshitaka Kise, Toru Chikui, Yasuo Yamashita, Kouji Kobayashi, Kazunori Yoshiura, Clinical usefulness of the mDIXON Quant the method for estimation of the salivary gland fat fraction: Comparison with MR spectroscopy., Br J Radiol., doi.org/10.1259/bjr.20160704, 2017.07, To estimate the fat fraction (FF) in the salivary glands (SGs) by the mDIXON method and the MRS method, and to compared the results.
METHODS:
Sixteen healthy volunteers were enrolled. mDIXON Quant and MRS (point-resolved spectroscopy: PRESS) with a single TE were employed to measure the FF in the parotid gland (PG) and submandibular gland (SMG). Multiple TEs were applied in 10 volunteers to correct for T2 decay. In addition, we assumed that the 1.3 ppm peak accounted for 60% of the total fat peak and estimated the FF (MRS all) as a gold standard. On mDIXON Quant images, VOIs were set on the bilateral SGs and we obtained the FF (mDIXON) of each VOI.
RESULTS:
There was a strong correlation between the results of the mDIXON Quant method and the MRS (single TE) method (R2=0.960, slope=0.900). Using PRESS with multiple TEs, there was also a strong correlation between FF (mDIXON) and FF (MRS all) (R2=0.963, slope=1.18). FF (MRS all) was 24.9 ± 12.7% in the PG and 4.5 ± 3.0% in the SMG, while FF (mDIXON) was 29.4 ± 16.2% in the PG and 6.4 ± 4.7% in the SMG. There were no significant differences between the two methods, but the Bland-Altman plot showed that FF (mDIXON) was slightly larger than FF (MRS all) for small FF areas.
CONCLUSIONS:
The mDIXON Quant method could be clinically useful for evaluating the FF of SGs, but the absolute values need careful interpretation Advance in knowledge: This study suggested the potential clinical usefulness of the mDIXON Quant method for the SGs..
4. Toru Chiikui, Erina KItamoto, Yukiko Nishioka Kami, Shintaro Kawano, Kouji Kobayashi, Takeshi Kamitani, Makoto Obara, Kazunori Yoshiura, Dynamic contrast-enhanced MRI of oral squamous cell carcinoma: A preliminary study of the correlations between quantitative parameters and the clinical stage., Br J Radiol., org/10.1259/bjr.20140814, 2015.04, To probe the utility of dynamic contrast-enhanced (DCE) -MRI parameters in assessing the clinical characteristics of oral squamous cell carcinoma.
METHODS:
A total of 85 tumors were included. We applied the Tofts and Kermode model for the DCE-MRI data, and obtained three dependent parameters: the influx forward volume transfer constant into the extravascular extracellular space (EES) from the plasma (Ktrans), the fractional volume of EES per unit volume of tissue (ve) and the fractional volume of plasma (vp). We evaluated the correlations between these parameters and the clinical stages.
RESULTS:
The T stage showed a negative correlation with the Ktrans (r = -0.2272, P = 0.0365), but it did not show a significant correlation with the other parameters. The N stage showed a negative correlation with Ktrans (r = -0.1948, P = 0.0404), and there were significant differences between N1 and N2+3 (0.119±0.027 min-1 vs 0.096±0.023 min-1, P = 0.0198) and between N0 and N2+3 (0.114±0.29 min-1 vs 0.096±0.023 min-1, P = 0.0288).
CONCLUSIONS:
A decrease in the Ktrans at the primary site was found in advanced N stage cases, which might indicate that the hypoxic status cause a high possibility of the metastasis. Advances in knowledge: A decrease in the Ktrans at the primary site suggested the high possibility of an advanced N stage..
5. Erina Kitamoto, Toru Chikui, Shintaro Kawano, Masahiro Ohga, Kouji Kobayashi, Yoshio Matsuo, Takashi Yoshiura, Makoto Obara, Hiroshi Honda, Kazunori Yoshiura, The application of dynamic contrast-enhanced MRI and diffusion-weighted MRI in patients with maxillofacial tumors., Academic Radiology, org/10.1016/j.acra.2014.08.016, 22, 2, 210-216, 2015.02, To elucidate the characteristics of four types of tumors, including squamous cell carcinoma (SCC), malignant lymphoma (ML), malignant salivary gland tumors (MSGTs), and pleomorphic adenoma (Pleo), in the maxillofacial region using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted MRI (DW-MRI)data.
MATERIALS AND METHODS:
A total of 59 tumors were included in this research. DCE-MRI and DW-MRI were performed. We applied the Tofts and Kermode model (TK model) for the DCE-MRI data and obtained three dependent parameters: the influx forward volume transfer constant into the extravascular extracellular space from the plasma (K(trans)), the fractional volume of extravascular extracellular space per unit volume of tissue (ve), and the fractional volume of plasma (vp).
RESULTS:
Among the K(trans) values, there were no significant differences between the three types of malignant tumors; however, there was a significant difference between the SCC and Pleo (P = .0099). The ve values of the Pleo were highest, with significant differences compared to the other categories (SCC, P = .0012; ML, P = .0017; and MSGT, P = .041). The ML had the lowest ve values, and there were significant differences between ML and the other two types of malignant tumors (SCC, P = .0278 and MSGT, P = .0062). In 14 (24%) cases, apparent diffusion coefficient (ADC) could not be measured because of poor image quality. The ADC values of the ML were lowest, whereas those of Pleo were highest, similar to that observed for ve.
CONCLUSIONS:
The Pleo tumors had lower K(trans) values and higher ve values, which are useful for differentiating them from the malignant tumors. Moreover, the ve was also useful for establishing a diagnosis of ML..
6. Chikui T, Obara M, Simonetti AW, Ohga M, Koga S, Kawano S, Matsuo Y, Kamintani T, Shiraishi T, Kitamoto E, Nakamura K, Yoshiura K., The principal of dynamic contrast enhanced MRI, the method of pharmacokinetic analysis, and its application in the head and neck region., Int J Dent, doi: 10.1155/2012/480659, 2012.11, The principal of dynamic contrast enhanced MRI, the method of pharmacokinetic analysis, and its application in the head and neck region..
7. Chikui T, Kitamoto E, Kawano S, Sugiura T, Obara M, Simonetti AW, Hatakenaka M, Matsuo Y, Koga S, Ohga M, Nakamura K, Yoshiura K, Pharmacokinetic analysis based on dynamic contrast-enhanced MRI for evaluating tumor response to preoperative therapy for oral cancer., J Magn Reson Imaging, doi: 10.1002/jmri.23704, 2012.06, 口腔扁平上皮ガンにおける、術前科学放射線の治療効果判定を、MRIのダイナミック撮影をコンパートメントモデル解析を用いる事により評価可能であるか検討した。治療高価判定としては、組織学的効果を大星、下里分類を用い、 gold standardとした。コンパートメントモデル解析から得られる、血管外細胞外のスペースveの変化量が、組織学的効果判定と相関する事を明らかにした。すなわわち、腫瘍細胞の減少による血管外細胞外スペースの割合の増加をMRでとらえる事が可能であることを示した。.
8. Matsubara R, Kawano S, Chikui T, Kiyosue T, Goto Y, Hirano M, Jinno T, Nagata T, Oobu K, Abe K, Nakamura S., Clinical Significance of Combined Assessment of the Maximum Standardized Uptake Value of F-18 FDG PET with Nodal Size in the Diagnosis of Cervical Lymph Node Metastasis of Oral Squamous Cell Carcinoma.
, Acad Radiol, 19, 6, 708-17, 2012.06.
9. Chikui T, Kawano S, Kawazu T, Hatakenaka M, Koga S, Ohga M, Matsuo Y, Sunami S, Sugiura T, Shioyama Y, Obara M, Yoshiura K., Prediction and monitoring of the response to chemoradiotherapy in oral squamous cell carcinomas using a pharmacokinetic analysis based on the dynamic contrast-enhanced MR imaging findings., Eur Radiol, DOI: 10.1007/s00330-011-2102-x, 2011 Aug;21(8), 2011.08.
10. Shiraishi T, Chikui T, Yoshiura K, Yuasa K., Evaluation of T2 values and apparent diffusion coefficient of the masseter muscle by clenching., Dentomaxillofac Radiol. , 40, (1), 35-41., 2011.01.
11. TORU CHIKUI, TOMOKO SHIRAISHI, TAKAHIRO ICHIHARA, TOSHIYUKI KAWAZU, MASAMITSU HATAKENAKA, YUKIKO KAMI, KENJI YUASA , KAZUNORI YOSHIURA, Effect of clenching on T2 and diffusion parameters of the masseter muscle, Acta Radiologica, 51, 1, 58-63, 2010.01.
12. Toru Chikui, Mayumi Shimizu, Toshiyuki Kawazu, Kazutoshi Okamura, Tomoko Shiraishi, Kazunori Yoshiura, A quantitative analysis of sonographic images of the salivary gland: A comparison between the sonographic findings and the sialographic findings, UltrasoundinMed.&Biol., 35(8):1257-1264, 2009.08.
13. Toru Chikui, Kenji Tokumori, Ryosuke Zeze, Tomoko Shiraishi, Takahiro Ichihara, Masamitsu Hatakenaka, Kazunori Yoshiura, A fast Look-Locker method for T1 mapping of the head and neck region., Oral Radiol, 25:22–29, 2009.06.
14. TORU CHIKUI, KAZUTOSHI OKAMURA, KENJI TOKUMORI, SEIJI NAKAMURA, Quantitative Analyses of Sonographic images of the parotid gland in patient with Sjogren's syndrome., Ultrasound in Med. & Biol., Vol. 32, No. 5, pp. 617- 622, 2006, 2006.05.
15. Toru Chikui, Kenji Yuasa1, kenji Tokumori, Shigenobu Kanda, Naonobu Kunitake, Katsumasa Nakamura,, Change of sonographic findings on cervical lymph nodes before and after preoperative radiotherapy, European Radiology, 10.1007/s00330-003-2173-4, 14, 7, 1255-1262, (2004) 14:1255–1262, 2004.07.
16. Change of sonographic findings on cervical lymph nodes before and after preoperative radiotherapy.
17. Chikui T., Yonetsu K., Nakamura T., Multivariate feature analysis of sonographic findings of metastatic cervical lymph nodes: contribution of blood flow features revealed by power Doppler sonography for predicting metastasis, AJNR Am J Neuroradiol., Vol.21,No.3,pp.561-567, 2000.05.
Presentations
1. Wannakamon Panyarak, Toru Chikui, Yasuo Yamashita, Kazunori Yoshiura, Image quality and ADC assessment in turbo-spin echo and echo-planar diffusion-weighted MR imaging of oral and maxillofacial tumors, 日本歯科放射線学会第59回学術大会, 2018.05, Purposes
The first was to compare the distortion ratio (DR) and the signal-to-noise ratio (SNR) between TSE-DWI and EPI-DWI. The second was to demonstrate the image distortion between TSE-DWI and T2 WI and to estimate ADC in various kinds of diseases.

Materials & Methods
At first, 42 patients underwent MRI using TSE-DWI and EPI-DWI. The DR, SNR, and ADC were compared between the two techniques.
Secondly, 160 underwent MRI using TSE-DWI. The distortion along X- and Y-axes was defined the distance from the centroids of the lesion on DWIb1000 to that of T2WI. We also estimated ADC values of the lesions.

Results
DR of TSE-DWI was significantly less than that of EPI-DWI and SNR of TSE-DWI was significantly higher than that of EPI-DW. ADC values of palatine tonsils and submandibular glands in TSE-DWI were significantly higher than those in EPI-DW.
The deviations along X-axis were 0.57±1.30 mm and that along the Y-axis were 0.27±1.74 mm, therefore, the image distortion was very small. Regarding the ADC values, cysts presented the highest values followed by vascular lesion and benign tumors, while malignant lymphoma showed the lowest values.

Conclusions
TSE DWI can produce less distortion and higher SNR than TSE-DWI, while TSE-DWI possibly exhibits different ADC values. Therefore, the TSE-DWI could be good alternative to EPI-DWI and is useful for the differential diagnosis..
2. Wannakamon Panyarak, Toru Chikui, Yasuo Yamashita, Kazunori Yoshiura, Image quality assessment in turbo-spin echo diffusion-weighted MR imaging and the correlation between the ADC value and the histological features of head and neck tumors, ASHNR 2017, 2017.09, Purpose
Many studies have supported the utility of diffusion-weighted images (DWIs) in the differential diagnosis. However, Echo-planar imaging (EPI) DWIs are susceptible to inhomogeneity of the magnetic field, which limits their usefulness in the head and neck region. Thus, the first purpose of this study was to evaluate the image distortion of Turbo-spin echo (TSE)-DWIs in comparison to anatomical images. The second purpose was to demonstrate the apparent diffusion coefficient (ADC) values in various types of head and neck lesions.

Materials & Methods
In all cases, MRI was performed using a clinical 3T whole-body MRI system (Philips Healthcare, Best, Netherlands). A total of 99 cases were enrolled. In each case, MRI was performed and T2-weighted images (T2WIs) and TSE-DWIs (b-value, 0 and 1000 s/mm2 [DWIb0 and DWIb1000]) were obtained.
At first, the DWI was reoriented onto a T2WI to match the matrix size and slice thickness. Then, we carefully drew the lesion, the bilateral Masseter muscles (MMs) and the spinal cord and defined them as regions of interest (ROIs) on a DWIb0, a DWIb1000 and a T2WI. The centroids of the ROIs were obtained. The differences along the X-axis (the direction of frequency encoding) and the Y-axis (the direction of phase encoding) were measured among these centroids. For the second purpose, an ADC map was obtained using DWIb0 and DWIb1000 images. All of the procedures were performed using the OsiriX Lite software program (Pixmeo SARL, Bernex, Switzerland) and the Image J software program (NIH, Maryland, USA).

Results
The 88 cases (89%) (benign tumor, n=20; malignant tumor, n=52; inflammation, n=9; cyst, n=7) could be evaluated by TSE-DWI .Eleven cases were excluded because their lesions were too small (n=8), or due to the presence of a severe metal artifact (n=3).
Focusing on the comparison of DWIb1000 images to T2WIs, the deviations along X-axis were 0.87±0.62 mm, 0.74±0.61 mm, and 0.42±0.38 mm (lesion, MMs, and spinal cord, respectively). Meanwhile, the deviations along the Y-axis were 1.37±1.28 mm, 1.44±0.99 mm, and 0.67±0.57 mm (lesion, MMs, and spinal cord, respectively). The deviation along the Y-axis was significantly larger than that along the X-axis in MMs and the spinal cord (p-value < 0.05); however, the absolute amount was not so large. In addition, the deviation that was observed between DWIb0 images and T2WIs was almost identical to that observed between DWIb1000 and T2WI (mean difference, <0.1 mm). Thus, the image distortion in the direction was not so severe.
Regarding the ADC values, cysts presented the highest values (1.91±0.59 x10-3 mm2/s) followed by benign tumors (1.46±0.44 x10-3 mm2/s), while malignant lymphoma showed the lowest values (0.86±0.12 x10-3 mm2/s). Thus, the ADC values obtained from TSE-DWIs were useful for evaluating these lesions.

Conclusions
TSE-DWIs were found to be immune to image distortion; thus, these images could be easily superimposed on anatomical images. Moreover, the ADC values that were obtained showed high diagnostic power in assessment of head and neck lesions.
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3. Toru Chikui, Wannakamon Panyarak, Yasuo Yamashita, Toshiyuki Kawazu, Kazunori Yoshiura, The detection of recurrence of oral cancer using turbo spin echo-diffusion-weighted imaging , ASHNR 2017, 2017.09, Objective
Many studies have supported the utility of diffusion-weighted image (DWI) for detecting recurrence. However, Echo-planar imaging DWIs are susceptible to inhomogeneity of the magnetic field, which limits its usefulness in the head and neck region. The first objective was to evaluate the utility of turbo spin echo (TSE)-DWI for detecting recurrence of oral cancer. The second objective was to compare the observer performance between TSE-DWI and gadolinium-enhanced T1-weighted imaging (Gd-T1WI).
Materials and Methods
Forty-two patients underwent surgery for oral squamous cell carcinoma and postoperative MRI, including axial T2-weighted imaging (T2WI), TSE-DWI and Gd-T1WI. All MRI procedures were performed using a 3T MRI system (Philips Healthcare, Best, the Netherlands). Twenty-two patients were classified as the recurrence group, and 20 were classified as the non-recurrence group. First, the DWI images were automatically adjusted for the translational and rotational motion to achieve superimposition with the Gd-T1WI images. We then assumed the high-signal-intensity area on DWIb1000 images or the enhanced area on Gd-T1WI images to indicate signs of recurrence and calculated the sensitivity and specificity. Once the enhanced area was identified, we outlined this area as a region of interest, copied it onto the adjusted ADC map, and measured the ADC value. These procedures were performed using the PACS system (Volume Analyzer Synapse Vincent; FUJIFILM, Tokyo, Japan). Next, two observers (observer 1: 22 years experience, observer 2: 3 years experience) interpreted the presence of recurrence using a five-point scale. The first session included the T1WI, T2WI and Gd-T1WI images, and the second included the axial T1WI, T2WI, DWIb1000, ADC map and combined T2WI and DWIb1000 fusion images. We estimated the area under the curve (AUC) using a receiver operating characteristic analysis. The image interpretation was performed on a personal computer using the OsiriX Lite software (Pixmeo SARL, Bernex, Switzerland).
Results
The sensitivity was 81.8% on both DWI b1000 and Gd-T1WI, and the specificity was 75% on DWI b1000 and 55% on Gd-T1WI. Although the specificity of DWI b1000 was quite high, the T2 shine-through might have reduced it to some degree. Of the 27 cases with enhanced areas on Gd-T1WI, the ADC of non-recurrence (1.82±0.51×10−3 mm2/s) was significantly higher than that of recurrence (1.14±0.113×10−3 mm2/s) (P<0.0001, Wilcoxon’s test). The AUCs in the first session including Gd-T1WI were 0.74±0.08 and 0.66±0.08 for observers 1 and 2, respectively. The AUCs in the second session including DWI were 0.79±0.07 and 0.82±0.06 for observers 1 and 2, respectively. There was a significant difference in the findings of observer 2 between the two methods (P=0.02). Therefore, DWI yielded a higher AUC, even if they did not used the enhanced MR images. In addition, a low ADC value was found to be characteristic of recurrence, and a good fusion image on DWI along with anatomical images were believed to help observers interpret the imaging findings.
Conclusions
TSE-DWI was found to be immune to image distortion and proved useful for differentiating between recurrence and a postoperative state. Adding the TSE-DWI sequence improved the observer performance regarding the interpretation of recurrence.
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4. Tomoko Shiraishi, Toru Chikui, Kunihiro Miwa, Toyohiro Kagawa, Shoko Yoshida, Kenji Yuasa, Quantitative shear wave elastography for the differentiation between metastatic and inflammatory cervical lymph nodes., 11th Asian congress of oral and maxillo-facial Radiology, 2016.11.
5. Yoshitaka Kise, Toru Chikui, Yasuo Yamashita, Kouji Kobayashi, 吉浦 一紀, Eiichirou Ariji, Quantitative shear wave elastography for the differentiation between metastatic and inflammatory cervical lymph nodes., 11th Asian congress of oral and maxillo-facial Radiology, 2016.11.
6. Chikui T, Yamashita Y, Shimizu M, Yoshimura K, Estimation of the proton density fat fraction of the salivary gland, ASHNR 50th Annual Meeting, 2016.09, Purpose
The first purpose was to assess the value of a six-echo variant of the modified Dixon Quant (mDixon) for salivary gland fat fraction (FF) quantification against multi-echo T2 corrected MR spectroscopy which was used as the reference standard. The second goal was to apply mDixon to estimate the FFs and to compare them among the control group, Sjogren's syndrome (SS) group and IgG4 related disease (IgG4-RD) group.
Materials and Methods
To conduct this study, 10 healthy volunteers were enrolled and 20 parotid glands (PGs) were evaluated. Quantitative MRI was performed using the mDixon sequence in addition to single-voxel MRS to compare the mDixon-FF with MRS-FF. On the FF image obtained by the mDixon method, we measured the FF of the region of interest (ROI). For the MRS, five unsuppressed 1H spectra were acquired by the Stimulated Echo Acquisition Mode with different echo delays (TE=13-53ms). Time-domain quantification was performed using the AMARES algorithm from the MRUI software package. Relaxation times T2 of water and the four main different triacylglycerol components (5.3, 2.1,1.3,and 0.9 ppm) were determined. For the second purpose, we applied the mDixon sequence to 64 cases. Eleven patients were thus assigned to the SS group, 4 patients to the IgG4-RD group, and the remaining 49 patients to the control group with any abnormality of the salivary gland. The outlines of both the PGs and submandibular glands (SMGs) were traced to set the ROIs to estimate the FF. In the control group, we evaluated any correlations among the FF, height, weight, body mass index (BMI), cholesterol level, and serum triglyceride level. We also compared the FF among the three groups.
Results
The FF(mDixon) correlated closely with the FF(MRS) according to the following equation FF(mDixon)=1.06xFF(MRS)-2.6 with R2 of 0.99. Therefore, the FF(mDixon) was considered to be potentially appropriate for clinical use. The PG-FF of the control group positively correlated with the weight and BMI (?=0.32, P=0.024 and ?=0.59, P < 0.001, respectively). The SMG-FF also correlated with the weight, BMI and serum triglyceride levels (?=0.59,P=0.0228, ?=0.38,P=0.0067 and ?=0.52, 0.0004, respectively). The SS group had a higher PG-FF(50.3±1.7%) than both the control group (34.9±11.1%) and IgG4-RD group (35.2±21.7%) and a significant difference was found between the SS group and control group (P=0.0113, Steel-Dwass test). This trend was remarkable in the submandibular gland. The SS group had a significantly higher SMG-FF(41.1±25.9%) than both the control group (7.4±4.5%) and IgG4-RD group (3.9±3.2%) (P < 0.0001 and P=0.0258, respectively, Steel-Dwass test). Therefore, the SMG-FF was lower than the PG-FF in the control group (P < 0.001, paired t test), however fat may accumulate rapidly in SMG patients due to the progression of SS.
Conclusions
Estimating the FF of the salivary gland using mDixon was thus found to be highly accurate in comparison to the MRS method. Therefore, this modality is considered to be potentially appropriate for clinical application. The FF obtained by mDixon quantitatively revealed the characteristic fat accumulation (especially SMGs) in the SS group..
7. Estimation of the fat fraction of the salivary gland using mDixon Quant.
8. Yoshitaka Kise, Toru Chikui, Yashio Yamashita, Koji Kobayashi, Atsushi Takemura, Kazunori Yoshiura, Eiichiro Ariji, Salivary gland fat fraction estimated with a new MRI method, IADR, Objectives: Measurement of fat fraction (FF) in the salivary glands is important in such diseases as Sjogren'ssyndrome, and it can be performed with MR spectroscopy. However, there is a limit in clinical application due to the complicated manipulations. A new magnetic resonance imaging (MRI) method, named mDIXON Quant, is convenientfor clinical application. The aim of this study was to estimate FF in the salivary glands using two different methods,mDIXON Quant and MR spectroscopy, and then to investigate the clinical usefulness of mDIXON Quant incomparison with MR spectroscopy.Methods: Sixteen healthy volunteers were enrolled in this study. They received two types of MRI examination,mDIXON Quant (6-point DIXON method) and MR spectroscopy (PRESS Single TE method), to measure FF in theparotid and submandibular glands. Ten subjects were also scanned by PRESS Multi TE method to determine theeffect of T2 value. On mDIXON Quant images, the regions of interest were set on both sides of the parotid andsubmandibular glands using the obtained FF map to determine FF.Results: 1. High correlation was observed in FF measured by mDIXON Quant and PRESS (Single TE) (slope=1.07, R2=0.960). 2. T2 value of the fat peak calculated by PRESS (Multi TE) was greater than T2 value of the water peak. 3. Even in taking the effect of T2 value by Multi TE method into account, a high correlation between mDIXON Quantand PRESS (Multi TE) was observed (slope=0.594, R2=0.964).Conclusions: The mDIXON Quant method appeared to be effective for FF measurement in the salivary glandsbecause the values obtained by mDIXON Quant correlated well with those by MR spectroscopy..
9. Kazutoshi Okamura, Yutaka Yoshida, Chikui Toru, Kazunori Yoshiura, Evaluation of improvement effect on the iterative reconstruction method in hard tissue, The 10th Asian Congress of Oral and Maxillo Facial Radiology, 2014.11, Institution and Country
Department of Oral & Maxillofacial Radiology, Faculty of Dental Science, Kyushu University, Japan.
*Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, Japan.

Correspondence e-mail
okamura@rad.dent.kyushu-u.ac.jp

Introduction
Iterative Reconstruction (IR) algorithms for Computed Tomography (CT) is widely used in clinical practice in late years. Although improvement in image quality and dose reduction have been reported, many were evaluated based on soft tissue.

Objectives
To evaluate improvement effect on the IR method in hard tissue like teeth and bone, with high-contrast object.

Materials and methods
Images of a high-contrast and a water cylinder phantom were acquired with Alexion four-row CT (Toshiba Medical Systems, Tokyo, Japan) at 120 kV tube voltage and five tube current levels. They were reconstructed with filtered back projection (FBP) and adaptive iterative dose reduction three-dimensional (AIDR 3D; Toshiba Medical Systems) reconstruction algorithms using the bone kernel. The slice thickness was 1.0mm and the reconstruction FOV was 70.2mm. The minimum separable hole size was estimated on the images of the high contrast phantom and the noise power spectrum (NPS) was measured on the images of the water cylinder phantom for FBP and for four levels of AIDR 3D.


Results
The NPSs of AIDR 3D were lower than that of FBP. The noise reduction effect was observed visually at low tube current. The minimum separable hole size was 0.5mm at 150 and 100mA, it raised by lowering tube current, and it was 1.0mm at 10mA. There ware no effect of AIDR 3D in detection size.

Conclusions and discussion
On these conditions, the effect of AIDR 3D did not lead to improvement in detection ability. At the time of evaluation of the hard tissue with low tube current, use of AIDR 3D may have an opposite effect. Evaluation with complicated structures like trabecular bone is required.
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10. Tomoko Shiraishi, Chikui Toru, Marie Hashimoto, Kenji Yuasa, Evaluation of Malignant lymphoma(ML) using MRI and US, The 10th Asian Congress of Oral and Maxillo Facial Radiology, 2014.11, Introduction
Malignant lymphoma(ML)almost occurs in lymph node, but rare extranodal. It was frequently mistaken for another malignant tumor.
Objectives
To elucidate the characteristics of ML imaging features in head and neck region.
Materials and methods
We described 8 patients (5 male and 3 female, average age, 67 years, age range 20). 8 lesions were histopathologically diagnosed as ML (tongue, 1 buccal mucosa, 3 maxilla and palate, 3 submandibular, 1) between 2006 and 2012. MRI was performed all lesions. We evaluated the signal intensity (SI) of T1WI, T2WI and estimated the diffusion coefficient (ADC) with b-factors of 0,500,1000 sec/mm2. In four cased, the dynamic MRI study was performed and the time intensity curve (TIC) was obtained. US was performed 2 lesions. US end point was internal echogenicity, internal vascularity, posterior echo enhancement.
Results
All ML cases had low intensity on T1WI. On T2WI, SI ranged from middle to high intensity. Mean ADC values were 0.771±0.142 sec/mm2 for ML, which were significantly lower than squamous cell carcinoma (? ± ??sec/mm2 in our preliminary study). TIC type showed a rapid increase downward titration type or a rapid increase storm decrease type.
Conclusions and discussion 
On both T1WI and T2WI, SI was not specific for ML. However, ADC was extremely low and the most characteristic finding, which suggested the small amount of extracellular space.
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11. Chikui Toru, Erina Kitamoto, Masahiro Ohga, Kazunori Yoshiura, The pharmacokinetic analysis of the dynamic contrast –enhanced MRI in maxillofacial region., The 10th Asian Congress of Oral and Maxillo Facial Radiology, 2014.11, Introduction
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is widely performed, but cannot elucidate the underlying physiological conditions. A pharmacokinetic analysis of the DCE-MRI findings may provide such information.
Objectives:
To elucidate the characteristics of tumors using a pharmacokinetic analysis.
Materials and Methods
A total of 135 tumors were examined[91 squamous cell carcinomas (SCC), 24 malignant lymphomas (ML), 10 malignant salivary gland tumors (MSGTs) and 10 pleomorphic adenomas (Pleo)]. We applied the Tofts and Kermode model and obtained three parameters: the influx forward volume transfer constant into the extravascular extracellular space (EES) from the plasma (Ktrans), the fractional volume of EES (ve) and the fractional volume of plasma (vp). We compared the parameters among the four types of tumors and also evaluated the correlation between the TMN stage and the parameters in SCC.
Results
ML had a significantly lower ve than the other categories (SCC; P<0.0001, MSGT; P=0.049 and Pleo; P=0.0001) and it also had the lowest Ktrans. Pleo had the highest ve value, significantly higher than that of SCC (P=0.0033), and had the lowest vp, which was significantly different from SCC (P=0.018). A small amount of EES and low permeability were characteristic of ML, while a large amount of EES and poor vascularity were characteristic of Pleo. In SCC, the Ktrans decreased with the progression of the N stage, and the Ktrans of N2 cases was lower to that of No cases (P = 0.0028).
Conclusions
The pharmacokinetic analysis clarified the physiological conditions of the tumors.
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12. Attempt for the estimation of the concentration of the Gd-contrast medium. Phantom study and clinical application..
13. Quantitative analysis of sonographic images of the salivary gland: Comparison between the sonographic findings and the sialographic findings.
14. Attempt for the estimation of the concentration of the Gd-contrast medium. Phantom study and clinical application..
15. T1 measurement by the Look-Locker sequence. The phantom study and the application to the head and neck lesion.
16. Sonographic texture characterizationof the parotid gland of the patient with the xerostomia.
17. The role of the Ultrasonography for the diagnoses of the patients with oral cancer..
18. The state of imaging diagnosis of cervical lymph nodes..
Membership in Academic Society
  • Japanese society for magnetic resonance in medicine
  • Japanese society of oral and maxillofacial radiology
  • The Japanese Society of Medical Imaging
  • The Japanese society of ultrasonics in medicine.
  • Japanese stomatological society
  • Japanese society of oral implantology
Educational
Educational Activities
Education for undergraduate students

1. Lecture: Oral and Maxillofacial Radiology (Fifth-grade student), Early exposure (Freshman)
2. Practice: Oral and Maxillofacial Radiology (radiation physics and clinical radiology) (4th-6th grade student)


Other Educational Activities
  • 2006.11.
  • 2005.11.
  • 2000.08.
Social
Professional and Outreach Activities
1. The lecture to the JICA member (Oral and Maxillofacial Radiology)

2. The executive secretary of study group. The group gives the information about the imaging diagnosis to the general dentists..