Kyushu University [Toru Chikui (Professor) Faculty of Dental Science, Department of Dental Science]

Toru Chikui

Last modified date：2024.04.16

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

1 Research Interests

2 Academic Activities

2.1 Papers

2.2 Reports

2.3 Presentations

3 Membership in Academic Society

4 Educational Activities

5 Other Educational Activities

6 Professional and Outreach Activ...

Graduate School

Department of Dental Science
Graduate School of Dental Science

Undergraduate School

Department of Dentistry
School of Dentistry

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Homepage

https://kyushu-u.elsevierpure.com/en/persons/toru-chikui
　Reseacher Profiling Tool　Kyushu University Pure

Phone

092-642-6407

Fax

092-642-6410

Academic Degree

PhD

Country of degree conferring institution (Overseas)

Field of Specialization

Section of Oral and Maxillofacial Radiology

Total Priod of education and research career in the foreign country

00years00months

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

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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.
.

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

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1.	Toru Chikui, Masahiro Ohga, Yukiko Kami, Osamu Togao, Shintaro Kawano, Tamotsu Kiyoshima and Kazunori Yoshiura, Correlation between diffusion-weighted image-derived parameters and dynamic contrast-enhanced magnetic resonance imaging-derived parameters in the orofacial region, Acta Radiologica Open, 10.1177/20584601241244777, 13, (3), 1-9, 2024.03, Background: Diffusion-weighted imaging (DWI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) are widely used in the orofacial region. Furthermore, quantitative analyses have proven useful. However, a few reports have described the correlation between DWI-derived parameters and DCE-MRI-derived parameters, and the results have beencontroversial. Purpose: To evaluate the correlation among parameters obtained by DWI and DCE-MRI and to compare them between benign and malignant lesions. Material and Methods: Fifty orofacial lesions were analysed. The apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudodiffusion coefficient (D) and perfusion fraction (f) were estimated by DWI. For DCE-MRI, TK model analysis was performed to estimate physiological parameters, for example, the influx forward volume transfer constant into the extracellular-extravascular space (EES) (Ktrans) and fractional volumes of EES and plasma components (ve and vp). Results: Both ADC and D showed a moderate positive correlation with ve (ρ = 0.640 and 0.645, respectively). Ktrans showed a marginally weak correlation with f (ρ = 0.296), while vp was not correlated with f or D; therefore, IVIM perfusion-related parameters and TK model perfusion-related parameters were not straightforward. Both D and ve yielded high diagnostic power between benign lesions and malignant tumours with areas under the curve (AUCs) of 0.830 and 0.782, respectively. Conclusion: Both D and ve were reliable parameters that were useful for the differential diagnosis. In addition, the true diffusion coefficient (D) was affected by the fractional volume of EES..
2.	Kam Yukiko, Chikui Toru, Togao Osamu, Kawano Shintaro, Fujii Shinsuked, Ooga, Masahiro, KiyoshimaTamotsu, Yoshiura Kazunori, Usefulness of reconstructed images of Gd-enhanced 3D gradient echo sequences with compressed sensing for mandibular cancer diagnosis: comparison with CT images and histopathological findings, European Radiology , https://doi.org/10.1007/s00330-022-09075-w, 2022.08, Objectives To compare the delineation of mandibular cancer by 3D T1 turbo field echo with compressed SENSE (CS-3D-T1TFE) images and MDCT images, and to compare both sets of images with histopathological findings, as the gold standard, to validate the accuracy and clinical usefulness of CS-3D-T1TFE reconstruction. Methods Twenty-four patients with mandibular squamous cell carcinoma (SCC) who underwent MRI including CS-3D-T1TFE and MDCT examinations before surgery were retrospectively included. For both examinations, 0.5-mm-thick coronal plane images and 0.5-mm-thick plane images perpendicular and parallel to the dentition were constructed. Two radiologists rated bone invasion in three categories indexed by cortical bone, cancellous bone, and mandibular canal (MC), and inter-rater agreement was assessed by weighted kappa statistics. In 20 of the 24 patients who underwent surgery, the correlation of bone invasion with the histopathological evaluation by pathologists was assessed using Pearson’s correlation coefficient. Soft-tissue invasion was assessed by diagnosing the presence of invasion into the mylohyoid muscle, gingivobuccal fold, and masticator space, and inter-rater agreement was assessed by kappa statistics. Results The interobserver agreement for bone invasion assessment was almost perfect with CS-3D-T1TFE and substantial with MDCT. The image evaluations by both observers agreed with the pathological evaluations in 15 of the 20 cases, showing high correlation (r > 0.8). CS-3D-T1TFE also showed higher inter-rater agreement than MDCT for all measures of soft-tissue invasion. Conclusions CS-3D-T1TFE reconstructed images were clinically useful in accurately depicting the extent of mandibular cancer invasion and potentially solving the problem of lesion overestimation associated with conventional MRI.
3.	Naoki Kaneko, Junsei Sameshima, Shintaro Kawano, Toru Chikui, Takeshi Mitsuyasu, Hu Chen, Taiki Sakamoto, SeijiNakamura, Comparison of computed tomography findings between odontogenic keratocyst and ameloblastoma in the mandible: Criteria for differential diagnosis, Journal of Oral and Maxillofacial Surgery, Medicine, and Pathology, 10.1016/j.ajoms.2022.07.016, 2022.09, Objectives Appropriate differential diagnosis between odontogenic keratocysts (OKCs) and ameloblastomas before treatment is crucial, but the radiographic findings, including computed tomography (CT), are often similar. This study, therefore, aimed to compare the CT findings of OKCs and ameloblastomas in the mandible. Methods Forty-one OKC and 28 ameloblastoma patients were radiologically evaluated by using initial CT images focusing on features such as long/short diameters, CT values, the appearance of the cortex, locularity, scalloped margins, sclerotic rims, and high-density structures. Subtypes of ameloblastoma were also considered. Statistical analyses, including multivariate logistic regression analysis, were performed to determine the features that were helpful for differential diagnosis. Results Short diameters and locularity were found to be significant features in the differential diagnosis. Between unicystic and conventional ameloblastomas, the frequency of sclerotic rims and buccal disappearance was significantly different. Based on these results, criteria were established for differential diagnosis between OKCs and ameloblastomas, and the diagnostic accuracy was 92.8 %. Conclusion This finding indicates that several CT findings are strikingly different between OKCs and ameloblastomas, and that these criteria for differential diagnosis are clinically useful..
4.	Takase H, Togao O, Kikuchi K, Hata N, Hatae R, Chikui T, Tokumori K, Kami Y, Kuga D, Sangatsuda Y, Mizoguchi M, Hiwatashi A, Ishigami K., Gamma distribution model of diffusion MRI for evaluating the isocitrate dehydrogenase mutation status of glioblastomas, Br J Radiol, DOI: 10.1259/bjr.20210392, 95, 2022 Feb 9:20210392. doi: 10.1259/bjr.20210392. Online ahead of print., 2022.02, Objective:To determine whether the γ distribution (GD) model of diffusion MRI is useful in the evaluation of the isocitrate dehydrogenase (IDH) mutation status of glioblastomas. Methods:12 patients with IDH-mutant glioblastomas and 54 patients with IDH-wildtype glioblastomas were imaged with diffusion-weighted imaging using 13 b-values from 0 to 1000 s/mm2. The shape parameter (κ) and scale parameter (θ) were obtained with the GD model. Fractions of three different areas under the probability density function curve (f1, f2, f3) were defined as follows: f1, diffusion coefficient (D) 1.0×10−3 and 3.0 × 10−3 mm2/s. The GD model-derived parameters measured in gadolinium-enhancing lesions were compared between the IDH-mutant and IDH-wildtype groups. Receiver operating curve analyses were performed to assess the parameters' diagnostic performances. Results:The IDH-mutant group’s f1 (0.474 ± 0.143) was significantly larger than the IDH-wildtype group’s (0.347 ± 0.122, p = 0.0024). The IDH-mutant group’s f2 (0.417 ± 0.131) was significantly smaller than the IDH-wildtype group’s (0.504 ± 0.126, p = 0.036). The IDH-mutant group’s f3 (0.109 ± 0.060) was significantly smaller than the IDH-wildtype group’s (0.149 ± 0.063, p = 0.0466). The f1 showed the best diagnostic performance among the GD model-derived parameters with the area under the curve value of 0.753. Conclusion:The GD model could well describe the pathological features of IDH-mutant and IDH-wildtype glioblastomas, and was useful in the differentiation of these tumors. Advances in knowledge:Diffusion MRI based on the γ distribution model could well describe the pathological features of IDH-mutant and IDH-wildtype glioblastomas, and its use enabled the significant differentiation of these tumors. The γ distribution model may contribute to the non-invasive identification of the IDH mutation status based on histological viewpoint..
5.	Togao O, Chikui T, Tokumori K, Kami Y, Kikuchi K, Momosaka D, Kikuchi Y, Kuga D, Hata N, Mizoguchi M, Iihara K, Hiwatashi A., Gamma distribution model of diffusion MRI for the differentiation of primary central nerve system lymphomas and glioblastomas, PLoS One, doi: 10.1371/journal.pone.0243839. eCollection 2020., 15, 12, e0243839., 2020.12, [URL], The preoperative imaging-based differentiation of primary central nervous system lympho- mas (PCNSLs) and glioblastomas (GBs) is of high importance since the therapeutic strate- gies differ substantially between these tumors. In this study, we investigate whether the gamma distribution (GD) model is useful in this differentiation of PNCSLs and GBs. Twenty- seven patients with PCNSLs and 57 patients with GBs were imaged with diffusion-weighted imaging using 13 b-values ranging from 0 to 1000 sec/mm2. The shape parameter (κ) and scale parameter (θ) were obtained with the GD model. Fractions of three different areas under the probability density function curve (f1, f2, f3) were defined as follows: f1, diffusion coefficient (D) 1.0×10−3 and 3.0 × 10−3 mm2/sec. The GD model-derived parameters were compared between PCNSLs and GBs. Receiver operating characteristic (ROC) curve analyses were performed to assess diagnostic performance. The correlations with intravoxel incoherent motion (IVIM)-derived parameters were evaluated. The PCNSL group’s κ (2.26 ± 1.00) was significantly smaller than the GB group’s (3.62 ± 2.01, p = 0.0004). The PCNSL group’s f1 (0.542 ± 0.107) was significantly larger than the GB group’s (0.348 ± 0.132, p
6.	Chikui T, Tokumori K, Panyarak W, Togao O, Yamashita Y, Kawano S, Kamitani T, Yoshiura K., The application of a gamma distribution model to diffusion-weighted images of the orofacial region, Dentomaxillofac Radiol, doi: 10.1259/dmfr.20200252., 2020.08, Objectives: This study evaluated the correlation among the diffusion-derived parameters obtained by monoexponential (ME), intravoxel incoherent motion (IVIM) and γ distribution (GD) models and compared these parameters among representative orofacial tumours. Methods: Ninety-two patients who underwent 1.5 T MRI including diffusion-weighted imaging were included. The shape parameter (κ), scale parameter (θ), ratio of the intracellular diffusion (ƒ1), extracellular diffusion (ƒ2) and perfusion (ƒ3) were obtained by the GD model; the true diffusion coefficient (D) and perfusion fraction (f) were obtained by the IVIM model; and the apparent diffusion coefficient (ADC) was obtained by the ME model. Results: ƒ1 had a strongly negative correlation with the ADC (ρ = -0.993) and D (ρ = -0.926). A strong positive correlation between f and ƒ3 (ρ = 0.709) was found. Malignant lymphoma (ML) had the highest ƒ1, followed by squamous cell carcinoma (SCC), malignant salivary gland tumours, pleomorphic adenoma (Pleo) and angioma. Both the IVIM and GD models suggested the highest perfusion in angioma and the lowest perfusion in ML. The GD model demonstrated a high extracellular component in Pleo and revealed that the T4a+T4b SCC group had a lower ƒ2 than the T2+T3 SCC group, and poor to moderately differentiated SCC had a higher ƒ1 than highly differentiated SCC. Conclusions: Given the correlation among the diffusion-derived parameters, the GD model might be a good alternative to the IVIM model. Furthermore, the GD model's parameters were useful for characterizing the pathological structure..
7.	Panyarak, W., Chikui, T., Tokumori, K., Yamashita Y, Kamitani T., Togao, O., Yoshiura, K., Utility of a diffusion kurtosis model in the differential diagnosis of orofacial tumours, Clinical Radiology, doi: 10.1016/j.crad.2020.01.008., 75, 7, 507-519, 2020.07, AIM: To compare the goodness of fit and correlations between diffusion kurtosis imaging (DKI) and a mono-exponential (ME) model, to compare the corrected apparent diffusion coefficient (Dapp) and apparent kurtosis (Kapp) of the DKI model, and the apparent diffusion coefficient (ADC) of the ME model among the various orofacial lesions, and to evaluate the diagnostic performances between the two models. MATERIALS AND METHODS: A total of 100 orofacial lesions underwent echo-planar diffusion magnetic resonance imaging (MRI) with four b-values. The goodness of fit was evaluated using Akaike information criterion. The correlations of the diffusion-derived parameters were evaluated. The diagnostic performance was analysed by receiver operating characteristics (ROC). RESULTS: The DKI model showed a significantly better goodness of fit than the ME model (p
8.	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 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..
9.	Chikui T, Yamashita Y, Kise Y, Saito T, Okamura K, Yoshiura K., 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 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..
10.	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..
11.	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..
12.	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..
13.	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..
14.	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。.
15.	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.
16.	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.
17.	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.
18.	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.
19.	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.
20.	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.
21.	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.
22.	Change of sonographic findings on cervical lymph nodes before and after preoperative radiotherapy.
23.	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.

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1.	Erina Kitamoto, Kazutoshi Okamura, Toru Chikui, Kazuhito Hioki, Kazunori Yoshiura., Evaluation of cervical lymph node metastasis in oral squamous cell carcinoma using dual-energy CT imaging, The 13th Asian Congress of Oral and Maxillo-Facial Radiology （The 13th ACOMFR 2022), 2022.06, Objectives To evaluate whether dual-energy CT (DECT) imaging analysis are useful for the detection of lymph node metastases in oral squamous cell carcinoma. Methods In this study, 23 new oral squamous cell carcinoma patients who underwent contrast-enhanced CT were included. 64 lymph nodes (20 metastatic, 44 nonmetastatic) pathologically diagnosed by neck dissection were retrospectively evaluated. A circular regions of interest (ROI) was drawn on the largest diameter of the control lymph node, specifically avoiding areas of visible necrosis. From these ROIs, attenuation values at 40 keV, 70 keV, and 100 keV, and iodine concentration data were recorded. The spectral attenuation curve slope (40 keV-70 keV, 40 keV-100 keV) and iodine concentration were used as three parameters to correlate with pathology. Results The spectral attenuation curve slope was significantly lower in metastatic nodes than in nonmetastatic nodes. Iodine concentration was significantly lower in metastatic nodes than in nonmetastatic nodes. There was an extremely high correlation between the spectral attenuation curve slope and iodine concentration. Conclusions Both spectral attenuation curve slope analysis and iodine concentration are expected to improve detection of lymph node metastasis in oral cancer. Furthermore, it was suggested that iodine concentration could be used as a single representative parameter. .
2.	Yukiko Kami, Toru Chikui, Osamu Togao, Shintaro Kawano, Shinsuke Fujii, Masahiro Ooga, Tamotsu Kiyoshima, Kazunori Yoshiura, Usefulness for Imaging Diagnosis of Mandibular Cancer by reconstructed images of Gd-enhanced 3D gradient echo sequences with compressed sensing -Comparison with CT images and histopathological findings- , The 13th Asian Congress of Oral and Maxillo-Facial Radiology （The 13th ACOMFR 2022), 2022.06, Objectives: To compare the delineation of mandibular cancer by 3D T1 turbo field echo with Compressed SENSE (CS-3D-T1TFE) images and MDCT images and compare them with histopathological images as reference standards to validate the accuracy and clinical usefulness of CS-3D-T1TFE reconstruction images. Methods: Twenty-four patients with mandibular squamous cell carcinoma (SCC) who underwent MRI including CS-3D-T1TFE and MDCT examination before surgery were included. For both images, 0.5-mm-thick coronal plane images and 0.5-mm-thick plane images perpendicular and parallel to the dentition were constructed. Two radiologists rated bone invasion in three type categories indexed by cortical bone, trabecular bone, and mandibular canal, and inter-rater agreement was assessed by weighted kappa statistics. In 20 of 24 cases, the bone invasion was correlated with histopathological evaluation by pathologists using Pearson's correlation coefficient. Soft-tissue invasion was assessed by diagnosing the presence of invasion into mylohyoid muscle, gingivobuccal fold, and masticator space, and inter-rater agreement was assessed by kappa statistics. Results: In the evaluation of bone invasion, the inter-rater agreement in the imaging evaluation of CS-3D-T1TFE was higher than that of MDCT and showed a high correlation with pathological assessment. In the soft-tissue invasion assessment, CS-3D-T1TFE showed higher inter-rater agreement than MDCT on all measures of soft tissue invasion. Conclusions: CS-3D-T1TFE reconstructed images were shown to be clinically useful, accurately depicting the extent of mandibular cancer invasion and potentially solving the problem of conventional MRI overestimating the lesion. .
3.	Toru Chikui, Masahiro Ohga, Yukiko Kami, Kazutoshi Okamura, Osamu Togao, Tamotsu Kiyoshima, Kazunori Yoshiura, Correlation between diffusion-derived parameters and pharmacokinetic parameters based on dynamic contrast enhanced MR imaging, The 13th Asian Congress of Oral and Maxillo-Facial Radiology （The 13th ACOMFR 2022), 2022.06, Objectives: To evaluate the correlation between the parameters derived from TSE-diffusion weighted imaging (TSE-DWI) and those obtained by a pharmacokinetic analysis based on dynamic contrast enhanced MR imaging (DCE-MRI). Methods: A total of 33 orofacial lesions were included. Patients underwent both TSE-DWI with 6 b-values and DCE-MRI with a temporal resolution of 1.97s. From TSE-DWI, we estimated the true diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (f) using an IVIM model, and the apparent diffusion coefficient (ADC) using an monoexponential model. From DCE-MRI, we estimated the influx forward volume transfer constant (Ktrans), fraction volume of cellular space (vc), extracellular-extravascular space (ve) and plasma (vp). Location-matched regions of the interest were placed when possible. Spearman’s correlation coefficients were estimated between the parameters. Results: Vc had moderate or weak negative correlations with D and ADC (ρ=–0.413 and ρ=–0.349, respectively), while ve had a moderate or weak positive correlation with D and ADC (ρ=0.409 and ρ=0.371 respectively). Both trends were reasonable; however, the comparative low correlation coefficient may be related to other factors that affected the diffusion-parameters and the uncertainty of both the diffusion and pharmacokinetic models. Vp had a weak positive correlation with f (ρ=0.388). The moderately positive correlation with Ktrans(ρ=0.443)) was slightly surprizing, because Ktrans is determined by both blood flow and the permeability surface-area product. Conclusions: Although DCE-parameters could be predicted from diffusion-derived parameters to some extent, both parameters should be used in a complementary way..
4.	Panyarak Wannakamon, Chikui Toru, Tokumori Kenji, Yamashita Yasuo, Yoshiura Kazunori, A comparison among gamma distribution, intravoxel incoherent motion, and mono-exponential models of orofacial tumours: a preliminary study , European Congress of Radiology 2020, 2020.07.
5.	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..
6.	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 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. .
7.	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) (PConclusions 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. .
8.	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.
9.	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.
10.	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 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..
11.	Estimation of the fat fraction of the salivary gland using mDixon Quant.
12.	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..
13.	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. .
14.	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. .
15.	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; PConclusions The pharmacokinetic analysis clarified the physiological conditions of the tumors. .
16.	Toshiyuki Kawazu, Toru Chikui, Tomoko Shiraishi, Masamitsu Hatakenaka and Kazunori Yoshiura, Evaluation of masseter muscle before and after contraction using Real-time tissue Elastography, 23rd ESHNR Annual Meeting, 2010.09.
17.	Attempt for the estimation of the concentration of the Gd-contrast medium. Phantom study and clinical application..
18.	Quantitative analysis of sonographic images of the salivary gland: Comparison between the sonographic findings and the sialographic findings.
19.	Attempt for the estimation of the concentration of the Gd-contrast medium. Phantom study and clinical application..
20.	T1 measurement by the Look-Locker sequence. The phantom study and the application to the head and neck lesion.
21.	Sonographic texture characterizationof the parotid gland of the patient with the xerostomia.
22.	The role of the Ultrasonography for the diagnoses of the patients with oral cancer..
23.	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..

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