K Yuasa

Fukuoka Dental College, Hukuoka, Fukuoka, Japan

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Publications (50)42.65 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to display the lingual artery superimposed on the anatomical image and to confirm its course and relation to the adjacent structures, noninvasively. Nineteen volunteers participated in the magnetic resonance imaging (MRI) study and one was excluded for excessive movement during scanning. A three-dimensional phase-contrast sequence (3D-PC) of magnetic resonance angiography (MRA) was used for vessel images, and a 3D-T1 high-resolution volume examination (THRIVE) was used for anatomical images. Colour-coded vessel images from 3D-PC MRA were superimposed on the 3D volume anatomical images, and the arterial course and relation to the adjacent structures were confirmed with multiplanar reconstructed cross-sectional (MPR) images. 3D-PC MRA images visualized the lingual artery in all 18 subjects and the sublingual artery in 14 subjects. In seven of 18 cases the bilateral sublingual arteries were shown to run side by side but had no contact with the sublingual veins. They ran together with the sublingual veins in four cases. Three cases showed irregular patterns. The bilateral sublingual arteries could not be identified in four cases. 3D-PC MRA images of the lingual artery superimposed on the anatomical images may be clinically useful to confirm its course and relationship to the adjacent structures before surgery, in order to prevent haemorrhage.
    International Journal of Oral and Maxillofacial Surgery 05/2013; · 1.52 Impact Factor
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    ABSTRACT: Diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) can be used to evaluate changes that accompany skeletal muscle contraction. To investigate whether jaw opening or closure affect the diffusion parameters of the masseter muscles (MMs). Eleven healthy volunteers were evaluated. Diffusion-tensor images were acquired to obtain the primary (λ(1)), secondary (λ(2)), and tertiary eigenvalues (λ(3)). We estimated these parameters at three different locations: at the level of the mandibular notch for the superior site, the level of the mandibular foramen for the middle site, and the root apex of the mandibular molars for the inferior site. Both λ(2) and λ(3) during jaw opening were significantly lower than that at rest at the superior (P = 0.006, P < 0.0001, respectively) and middle site (P = 0.004, P = 0.0001, respectively); however, the change in λ(1) was not significant. At the lower site, no parameter was significantly different at rest and during jaw opening. There was no significant difference in T2 between at rest (40.3 ± 4.4 ms) and during jaw opening (39.2 ± 2.7 ms; P = 0.12). The changes induced by jaw closure were marked at the inferior site. In the middle and inferior sites, the three eigenvalues were increased by jaw closure, and the changes in λ(1) (P = 0.0145, P = 0.0107, respectively) and λ(2) (P = 0.0003, P = 0.0001) were significant (especially λ(2)). The eigenvalues for diffusion of the MM were sensitive to jaw position. The recruitment of muscle fibers, specific to jaw position, reflects the differences in changes in muscle diffusion parameters.
    Acta Radiologica 12/2011; 53(1):81-6. · 1.33 Impact Factor
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    ABSTRACT: The aim of this study was to quantitatively evaluate the relationship between vascularity within lymph nodes and lymph node size on Doppler ultrasound images of patients with oral cancer. A total of 310 lymph nodes (86 metastatic, 224 benign) from 63 patients with oral cancer were classified into 4 groups according to their short axis diameters: Group 1, short axis diameters of 4-5 mm; Group 2, 6-7 mm; Group 3, 8-9 mm; and Group 4, ≥ 10 mm. Vascular and scattering indices of lymph nodes on Doppler ultrasound images were analysed quantitatively. The vascular index was defined as the ratio of blood flow area to the whole lymph node area and the scattering index was defined as the number of isolated blood flow signal units. For metastatic lymph nodes, the vascular index was highest in Group 1 and decreased as lymph node size increased. The vascular index of benign lymph nodes did not differ significantly among the four groups. The vascular index of metastatic lymph nodes was significantly higher than that of benign lymph nodes in Group 1. For metastatic lymph nodes, the scattering index increased as lymph node size increased and was significantly higher than that of benign lymph nodes in Groups 2-4. An increase in vascularity is a characteristic of Doppler ultrasound findings in small metastatic lymph nodes. As the metastatic lymph node size increases, blood flow signals become scattered, and the scattering index increases.
    Dentomaxillofacial Radiology 10/2011; 40(7):415-21. · 1.27 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the changes in T2 values and apparent diffusion coefficient (ADC) in the masseter muscle by clenching in healthy volunteers. 37 volunteers were enrolled in the study. We measured bite force using pressure-sensitive paper and a T2 map. The ADC map was obtained at rest, during clenching, immediately after and 5 min after clenching. The spin-echo sequence was used to calculate T2, and single-shot spin-echo echo planar imaging was used to calculate the ADC. The motion-probing gradients (MPGs) were applied separately along the posterior-to-anterior (PA), right-to-left (RL) and superior-to-inferior (SI) directions, with b values of 0, 300 and 600 s mm(-2) in each direction. ADC-PA, ADC-RL, and ADC-SI values were obtained, and we calculated the ADC-iso for the mean diffusivity. There were no significant differences between the stronger and weaker sides of bite force before, during or 5 min after clenching for T2 and ADC. The bite force had little effect on these parameters; thus, we used the average of the two sides for the following analyses. Time course analysis of ADC-iso, ADC-PA, ADC-RL and ADC-SI demonstrated a marked increase after clenching and a rapid decrease immediately after clenching, although they did not completely return to the initial values; however, the change in ADC-RL was significantly greater than those in ADC-PA or ADC-SI (P<0.001 each). The changes in T2 were similar to those of ADC, although not as marked. ADC (especially ADC-RL) was altered by contraction of the masseter muscle.
    Dentomaxillofacial Radiology 01/2011; 40(1):35-41. · 1.27 Impact Factor
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    ABSTRACT: The persistent muscle contractions during clenching are thought to cause some temporomandibular disorders. However, no report has so far evaluated the effect of clenching on the masticatory muscles by magnetic resonance imaging (MRI). To investigate the effect of clenching with maximum voluntary contraction on the T(1), T(2), and signal intensity (SI) of the balanced fast field-echo (b FFE) of the masseter muscle. A total of 11 volunteers participated. Multi-echo spin-echo echo-planar imaging was used for T(2) measurements, and multi-shot Look-Locker sequence for T(1) measurements. The Look-Locker sequence has been used for fast T(1) mapping and this method has been applied for the imaging of various tissues. In addition, the b FFE was used due to the high temporal resolution. These three sequences lasted for 10 min and the participants were instructed to clench from 60 s to 80 s after the start of the data acquisition. T(2), T(1), and SI were normalized compared to pre-clenching values. T(2) decreased by clenching, which reflected a decrease of tissue perfusion due to the mechanical pressure. It increased rapidly after the clenching (peak value, 1.11+/-0.03; peak time, 16.8+/-7.6 s after the clenching), which corresponded to the reactive hyperemia and later, it gradually returned to the initial values (half period, 2.22+/-0.84 min). The change in the SI of the b FFE was triphasic and similar to that of T(2) clenching. T(1) increased after the cessation of the clenching and later gradually decreased during the recovery periods. However, the change of T(1) was quite different from that of T(2), with a lower peak value (1.04+/-0.02), a later peak time (36.0+/-28.0 s), and a longer half period (4.76+/-3.40 min) (P<0.0001, 0.0066, 0.02, respectively). The change in T(2) was triphasic and we considered that it predominantly reflected the tissue perfusion.
    Acta Radiologica 07/2010; 51(6):669-78. · 1.33 Impact Factor
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    ABSTRACT: The aim of this study was to describe the magnetic resonance images (MRIs) of the architecture of metastatic lymph nodes as well as healthy lymph nodes and to correlate the images with the histopathologic architecture of the lymph nodes from oral squamous cell carcinoma. The signal intensities of 98 cervical lymph nodes from 20 patients with oral squamous cell carcinoma were evaluated on T2-weighted and diffusion-weighted whole-body imaging with background body signal suppression (DWIBS). The MRI findings were compared with the histopathologic architecture. On T2-weighted images, very hyperintense and/or isointense areas were specific findings for lymph nodes containing metastases from oral squamous cell carcinoma. Histopathology indicated that these areas corresponded to cystic degeneration or keratinization. Using DWIBS images with inverted black-and-white image contrast, cystic degeneration, keratinization, fibrous tissue, tumor tissue, and lymphoid tissue were either hypointense or intermediate in intensity. On T2-weighted images, very hyperintense and/or isointense areas were characteristic findings for lymph nodes containing metastases from oral squamous cell carcinoma. This suggests cystic degeneration or keratinization within the affected lymph nodes. Using DWIBS images, it was difficult to differentiate metastatic from benign lymph nodes.
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 03/2010; 109(6):890-9. · 1.50 Impact Factor
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    ABSTRACT: The purpose of this study was to assess the capacity of dental 3-dimensional computed tomography (3D-CT; limited cone-beam CT) to predict the exposure and injury of the inferior alveolar nerve (IAN) after mandibular third molar extractions. This study was a retrospective case series of patients who presented for extraction of mandibular third molars. Subjects eligible for study enrollment were those who underwent preoperative dental 3D-CT because the mandibular third molars were determined to be extremely close to the IAN on panoramic radiogram. The predictive variable was the anatomic relation of the IAN and third molar apices and was a binary variable, contact or noncontact. The primary outcome variable was IAN exposure, and the secondary outcome variable was IAN injury. From January 2006 to August 2007, 1,853 mandibular third molars in 1,539 patients were extracted. Among them, dental 3D-CT was performed on 53 third molars in 47 patients. The mandibular third molars were judged to make contact with the mandibular canal on dental 3D-CT images in 35 cases (66%). Intraoperative IAN exposure was observed in 17 (49%) contact cases and 2 (11%) noncontact cases on dental 3D-CT images. Of 53 cases extracted after dental 3D-CT examinations, IAN injury occurred in 8 cases (15%). IAN exposure led to IAN injury in 36.8% of cases, whereas IAN injury occurred in only 2.9% of cases without IAN exposure. Although the incidence of IAN injury in the molar-canal contact cases was 23%, all 8 cases with IAN injury (100%) were included in these contact cases. When viewing the anatomic relation between the IAN and mandibular third molar root apices using dental 3D-CT, contact of the 2 anatomic structures results in an increased risk for IAN exposure or injury.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 12/2009; 67(12):2587-91. · 1.58 Impact Factor
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    ABSTRACT: Persistent muscle contractions during clenching are considered to be one reason for temporomandibular disorders. However, no report has evaluated the effect of clenching on the masticatory muscles, as measured by magnetic resonance imaging (MRI). To investigate whether clenching has an effect on either T(2) or the coefficients for diffusion of the masseter muscles (MM), and to evaluate the effect of the distribution of bite force on such indices. Twenty-three subjects were examined. Bite force was measured by a pressure-sensitive sheet, and the force of the right and the left sides was calculated. MRI was used to evaluate T(2), the apparent diffusion coefficient (ADC), and the primary (lambda(1)), secondary (lambda(2)), and tertiary eigenvalues (lambda(3)). These indices on the stronger side of the bite force were compared to those on the weaker side. Thereafter, the indices were compared between at rest and during clenching. There was no significant difference in any of the indices (T(2), ADC, lambda(1), lambda(2), and lambda(3)) between the side of stronger bite force and the side with weaker. T(2) increased by clenching, and the difference was significant in the side with stronger bite force (P = 0.006). ADC, lambda(1), lambda(2), and lambda(3) increased significantly by clenching (P <0.01, P <0.01, P <0.01, and P <0.01, respectively) on both sides. The percentage of change of lambda(2) by clenching was 26.2+/-15.7% on the stronger side and 26.9+/-18.6% on the weaker side, which was significantly greater than either that of lambda(1) or lambda(3). The coefficients for diffusion of the MM were sensitive to change by clenching, and lambda(2) was the most sensitive. Moreover, the relative distribution of the bite forces had no effect on any of the indices.
    Acta Radiologica 12/2009; 51(1):58-63. · 1.33 Impact Factor
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    ABSTRACT: ObjectiveOur purpose was to evaluate the utility of the small region of interest (ROI) method to detect the architecture of cervical lymph nodes and the specificity of time-intensity curves for tissue present in cervical lymph nodes. MethodsSpecimens were taken from 17 lymph nodes of eight patients (ten sides of the neck) with oral squamous cell carcinoma who underwent dynamic contrast-enhanced magnetic resonance imaging (MRI) and neck dissection between 2005 and 2007 at our hospital. Two methods of constructing time-intensity curves were compared: the conventional method that uses relatively large ROIs, and a new method that uses small ROIs. Curves made with the small ROI method were then compared to histopathological findings for dissected lymph nodes. ResultsThe small ROI method allowed differences in signal intensity to be discerned at the tissue level, which was not possible with the conventional large ROI method. Curves for normal lymphoid tissue tended to be type I, those for tumor cells tended to be type II, and those for keratinization/necrosis tended to be types III and IV, indicating that time-intensity curves can be specific to tissue type within lymph nodes. ConclusionThe small ROI method was useful for evaluation of the architecture of cervical lymph nodes.
    Oral Radiology 01/2008; 24(1):25-33. · 0.17 Impact Factor
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    ABSTRACT: Objectives To clarify the histopathological features of low-attenuation areas in computed tomography (CT) images of cervical metastatic and benign lymph nodes in patients with oral squamous cell carcinoma (SCC). Methods CT images of 230 lymph nodes from 37 patients with oral SCC were classified into four categories and compared with histopathological findings. Metastatic lymph nodes were evaluated in terms of focal necrosis, keratinization, fibrous tissue, and the proportion of the lymph node showing focal necrosis. Benign lymph nodes were evaluated in terms of adipose tissue, follicular hyperplasia, sinus histiocytosis, hyperemia, focal hemorrhaging, and the amount of adipose tissue. Results Histopathologically, all 13 metastatic lymph nodes with rim enhancement on CT images included focal necrosis. However, most of the lymph nodes showed no focal necrosis. In addition, tumor cells, keratinization, and fibrous tissue were observed in the lymph nodes. Of the 26 metastatic lymph nodes with a heterogeneous appearance on CT images, four did not show focal necrosis. These lymph nodes showed keratinization or accumulation of lymph fluid. Histopathologically, 20 of 24 benign lymph nodes with a heterogeneous appearance on CT images (83.3%) had accompanying adipose tissue. Conclusions Focal necrosis was the most important factor contributing to low attenuation in metastatic lymph nodes. However, other factors, such as tumor cells, keratinization, fibrous tissue, and accumulation of lymph fluid, also contributed. In benign lymph nodes, the presence of adipose tissue was a contributing factor in low-attenuation areas, as was focal hemorrhaging.
    Oral Radiology - ORAL RADIOL. 01/2008; 24(1):16-24.
  • Choonpa Igaku 01/2007; 34(5):509-520.
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    ABSTRACT: ObjectivesTo develop a simple image viewer that utilizes image files in general-purpose formats that are written from the original 3DX volume data. MethodsWe used FLASH MX2004 for Macintosh to develop a simple image viewer. In developing the software for the simple image viewer, we decided that the viewer should provide the following features: (1) be available to both Windows OS and Mac OS, (2) allow interlocking of the 3D images, (3) display image enlargement, and (4) allow distance measurements. The accuracy of the distance measurements was evaluated. ResultsThe procedure was as follows: (1) write 3D images in jpeg format to a folder on i-VIEW; (2) place the folder containing the 3D images into the directory of the simple image viewer software on a PC; (3) start the software and open the window to input the folder name containing the 3D images; and (4) display the 3D images. Our viewer had features such as image enlargement, interlocking 3D images, drawing, and distance measurements. No significant differences were shown between the measurements made by our simple viewer and the actual values of the images in any direction. ConclusionsOur image-viewing software for 3DX is beneficial for clinical use.
    Oral Radiology 01/2006; 22(2):47-51. · 0.17 Impact Factor
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    ABSTRACT: ObjectivesTo analyze the relationship between lateral displacement of the mandible and scoliosis. MethodsFrom April 2002 through July 2003, we examined posteroanterior cephalometric radiographs and chest X-rays from 85 patients with jaw deformities and a control group of 20 patients with no jaw deformities. To measure the lateral shift of the mandible, we drew a horizontal baseline (X axis) on the cephalogram connecting the intersection of the external margins of the orbits and the most lateral points of the greater wings of the sphenoid. A vertical baseline (Y axis) was then marked perpendicular to the X axis, intersecting the ethmoid crista galli. Then, we measured the lateral displacement of the mandibular mentum from the Y axis. Displacement to the right was designated positive; that to the left was designated negative. Cobb's method was used to measure scoliosis curves on chest X-rays; the direction of the curve was designated similarly. ResultsOf the 85 patients with jaw deformity, 23 (27.1%) had a Cobb angle exceeding 10°. None of the control group had scoliosis exceeding 10°. No correlation was found between the direction of mandibular displacement and the direction of scoliosis. ConclusionThis study suggests a relationship between jaw deformities and scoliosis, as scoliosis was found in 27.1% of the patients with a main complaint of jaw deformity.
    Oral Radiology 01/2006; 22(1):14-17. · 0.17 Impact Factor
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    ABSTRACT: The purpose was to illustrate the sonographic changes of tongue cancer after radical radiotherapy. In 24 patients with tongue cancer treated by interstitial brachytherapy (BRT) (uneventful recovery n = 16 , recurrence n = 5, severe soft tissue complication n = 3), follow-up examination were performed and both the margin and the vascular pattern were retrospectively assessed. We basically performed US examination at least once every 3 months after BRT within 1 year during follow-up period. In the healing process, intraoral sonography shows an unclear margin immediately after brachytherapy and a transient increase of the vascularity lasted within 6 months after BRT, followed by a decrease in the vascularity. The large difference in echogenicity between the primary site and the surrounding tissue and the increased difference suggested the possibility of either radiation ulceration or recurrence. Intraoral sonography could depict the sequence changes of the tongue after BRT, and it was thus useful to confirm the clinical findings of either radiation ulcers or recurrence.
    European Journal of Radiology 01/2005; 52(3):246-56. · 2.51 Impact Factor
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    ABSTRACT: The aim of this study was to assess the changes in the power Doppler sonographic findings in patients with oral cancer undergoing chemotherapy and radiotherapy. We performed US examinations on 187 cervical lymph nodes (71 metastatic and 116 reactive nodes) excised from 52 patients before and after preoperative therapy. On Power Doppler images, we calculated the vascular index (VI) and evaluated the vascular pattern. We also assessed the diagnostic power using receiver operating characteristic (ROC) curve analysis. Irradiation caused an increase of the VI and better visualization of the vessels within the lymph node in the reactive nodes; however, in the metastatic nodes, the VI was not significantly different between that before and after irradiation. When the reader observed the images before irradiation, the area under an ROC curve (Az values) observed by B-mode sonography were closely similar to those obtained by B-mode plus power Doppler sonography. With both images before and after irradiation, the Az value obtained by B-mode plus power Doppler sonography was higher than that by B-mode sonography alone. After irradiation, the enhanced Doppler signals contributed to a better visualization of the vessels and a better detection of any vascular abnormalities.
    European Radiology 08/2004; 14(7):1255-62. · 4.34 Impact Factor
  • Journal of Oral and Maxillofacial Surgery 11/2003; 61(10):1233-6. · 1.28 Impact Factor
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    ABSTRACT: We sought to evaluate the diagnostic efficacy of computed tomography (CT) images in the differentiation between intraosseous malignant tumors and osteomyelitis spreading into the masticator space. A retrospective evaluation was carried out by using CT images from 12 patients with intraosseous malignant tumors and 9 patients with osteomyelitis involving the masticator space and accompanying mandibular bone destruction. The following CT observations are discussed: (1) bone destruction pattern subdivided into spotty, gross, or permeative; (2) cortical bone expansion; (3) diffuse osteosclerotic changes; (4) periosteal reaction; (5) masticator muscle involvement; (6) enlargement of the facial muscle; and (7) attenuation in the subcutaneous adipose tissue. The pattern of permeative bone destruction, cortical bone expansion, and the enlargement of both the masseter and medial pterygoid muscles were all observed in patients with malignant tumors. In contrast, diffuse sclerotic change and a periosteal reaction were significant observations in patients with osteomyelitis. The efficacy of CT in establishing a differential diagnosis of malignant tumors or osteomyelitis is supported by this study.
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 05/2003; 95(4):503-9.
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    ABSTRACT: In recognition of the academic activity ongoing at and the contributions made by the many imaging, imaging-related, radiation oncology, and medical physics specialty societies, Radiology is pleased to publish the titles and authors of their award-winning papers and honored lectures and the names of medal recipients. The following information is printed as sub-mitted by the specialty societies. Our congratulations are ex-tended to the authors, recipients, and societies. —Anthony V. Proto, MD, Editor. "Correlating carotid artery stenosis detected by panoramic ra-diography with clinically relevant carotid artery stenosis deter-mined by duplex ultrasound". "Disc position and the bilaminar zone of the temporomandibular joint in asymptomatic young individuals by magnetic resonance im-aging" Specialty societies that wish to publish this type of announce-ment— of award-winning papers, honored lectures, and medal and award recipients—should send the information to Anthony V.
    AMERICAN ACADEMY OF ORAL AND MAXILLOFACIAL RADIOLOGY; 01/2003
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    ABSTRACT: Most jaw muscles are complex, multipennate with multiple components. The morphologic heterogeneity of masticatory muscles reflects their functions. We hypothesized that the volume of masticatory muscles changes between jaw closing and opening, and that there is a difference in the volume change among the muscles. Magnetic resonance images of the entire head were obtained in ten normal young adult subjects before and after maximum jaw opening. The volume changes of the masseter, medial, and lateral pterygoid muscles were measured. Only slight changes were seen in the masseter and medial pterygoid muscles. The lateral pterygoid muscle, however, significantly decreased its volume during jaw opening. The results provide normative values of muscle volume in living subjects, and suggest that the volume changes differ among jaw muscles.
    Journal of Dental Research 07/2002; 81(6):428-32. · 3.83 Impact Factor
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    ABSTRACT: Experimental models of lymph node metastasis were developed for Doppler sonography. Cervical lymph node (LN) metastasis was induced by the implantation of a VX-2 tumor on the oral floor of 10 rabbits. Twenty metastatic LNs were observed weekly by power Doppler sonography, and the presence of an avascular area and the peripheral vessels were evaluated. The time-averaged maximum velocity (TAMx) at the hilum was also measured. The percentage of the metastatic LNs presenting with an avascular area increased over time. The peripheral vessels were detected in 14 of 20 LNs. The peak time of the TAMx significantly correlated to that of the initial detection of the avascular area. In the beginning, metastatic LNs were depicted as hypervascular structures while the TAMx at the hilum increased. Later, an avascular area was detected and the TAMx at the hilum decreased, which resulted in a blood supply to the node from the peripheral vessels.
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 04/2002; 93(3):350-7.

Publication Stats

304 Citations
42.65 Total Impact Points

Institutions

  • 2005–2011
    • Fukuoka Dental College
      Hukuoka, Fukuoka, Japan
  • 1986–2005
    • Kyushu University
      • Faculty of Dental Science
      Fukuoka-shi, Fukuoka-ken, Japan
  • 2003
    • Sapporo Medical University
      • Department of Oral Surgery
      Sapporo, Hokkaidō, Japan
  • 1994
    • Fukuoka University
      Hukuoka, Fukuoka, Japan