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T Chikui

Publications and source records attributed to T Chikui.

16 recordsLinked to original sources
PubMed2005

Correlation between diagnostic accuracy and perceptibility.

OBJECTIVES: To correlate diagnostic accuracy for proximal caries with perceptibility of low contrast image details using regression analysis. The other purpose was to determine the attenuation range required for proximal caries diagnosis. METHODS: The results of the two types of observer performance tests described above were retrieved from previous studies. Recording media included in those studies were the Compuray and the Dixel, direct digital radiographic systems, and Ektaspeed Plus film. The average numbers of perceptibility of image details from five observers were calculated for each step and for every combination of contiguous steps of the aluminium test phantom from the perceptibility test. The average diagnostic accuracy for proximal caries from the same five observers was correlated with the total number of perceptible details from the phantom using regression analysis. Finally, attenuation range required for proximal caries diagnosis was calculated from the attenuation range of the phantom where the maximum correlation coefficient was obtained. RESULTS: Maximum correlation (r=0.68) was obtained at the combination of five contiguous steps of the aluminium test phantom. Attenuation range required for proximal caries diagnosis corresponded to the 2 mm to 6 mm thickness of aluminium with acrylic block of 12 mm thickness. CONCLUSIONS: There is a correlation between perceptibility of low contrast image details and diagnostic accuracy for proximal caries. There may be a possibility to simplify observer performance tests for proximal caries diagnosis by using the standardized phantom simulating its attenuation range.

Adolescent↗
PubMed2005

Effects of the automatic exposure compensation on the proximal caries diagnosis.

OBJECTIVE: To elucidate the effect of automatic exposure compensation (AEC) on the diagnostic accuracy of proximal caries by comparing several digital intraoral imaging systems with a film. MATERIALS AND METHODS: Twenty-seven extracted teeth served as proximal caries samples. Three digital radiographic systems; the Compuray, the Dixel, and the Sens-A-Ray without scintillator layer, and Kodak Ekta-speed Plus films were used as recording media. Radiographs of the teeth samples were obtained with each recording medium under seven to eight different exposures including the optimum level. Six oral radiologists evaluated the possibility of proximal caries with the five-grade-confidence-scale. On digital radiographs, image manipulations were allowed after the initial assessment. Receiver operating characteristic (ROC) curves were obtained at each exposure in each recording medium. The area under the ROC curve (Az) was used as the representative value of diagnostic accuracy. Diagnostic accuracy (DA) curves were obtained by plotting averaged Az values from all observers as a function of incident exposure in each system. RESULTS: The effect of exposure variation on the DA was slight in the film while it was significantly larger in the digital systems without AEC. Among digital systems, the effect of exposure variation was smaller in the system with AEC than those without AEC. There was no significant effect on the diagnostic accuracy even if digital image manipulation was employed. CONCLUSION: AEC minimizes the decrease of DA due to inadequate exposures. Since it compensates for the narrow exposure range in the digital intraoral sensor systems, the system with AEC may be preferable for the clinical diagnostic tasks.

Adolescent↗
PubMed2002

Lymphoepithelial lesion of the parotid gland.

We describe a case of lymphoepithelial lesion of the parotid gland, also known as salivary lymphoepithelial lesion. Lymphoepithelial lesions are usually seen in conjunction with autoimmune disease of the salivary glands and these lesions do not always remain benign. Our case consisted of two masses that had different imaging features. Moreover, we could investigate the changes of the size and internal architecture on imaging due to the postponement of surgical intervention on the masses. At review 6 months later, the size of the masses had increased. The aims of this paper were to: (1) investigate the contribution of gray-scale sonography, power Doppler sonography, magnetic resonance imaging, and computed tomography to the diagnosis; and (2) consider the appropriate imaging modality to follow-up this case to monitor for recurrence or malignant transformation.

Diagnosis, Differential↗
PubMed2001

Possibility of sialographic sonography: a Doppler phantom study.

OBJECTIVES: The purpose of this study was to develop a new diagnostic method that has the merits of both sialography and sonography. STUDY DESIGN: Saline solution and various contrast media (Urografin 76%; 100%, 90%, and 67% Lipiodol Ultra-Fluide; 5% and 1% barium sulfate; and Levovist) were injected into thin tubes at a rate of approximately 0.001 to 0.1 mL/s. The relationship between the Doppler signal intensity and the kind, concentration, and velocity of the fluid was analyzed. RESULTS: Levovist, 90% and 67% Lipiodol Ultra-Fluide, and the barium sulfate solutions produced Doppler signals. The mixture of Lipiodol Ultra-Fluide and saline solution produced high signals at any concentration, in contrast with the barium sulfate solutions. Signals could be observed at any speed, from the speed of normal sialography down to 0.001 mL/s, and there was a proportional relationship between signal intensity and velocity for all fluids producing signals. CONCLUSION: The fact that we could obtain high signals with several fluids indicates potential clinical diagnostic usefulness of sialographic sonography.

Barium Sulfate↗
PubMed2001

The combined use of US and MR imaging for the diagnosis of masses in the parotid region.

PURPOSE: To evaluate the usefulness of the combination of the two non-invasive modalities US and MR imaging to diagnose masses in the parotid region. MATERIAL AND METHODS: The US and MR findings of 21 patients with parotid masses were analyzed retrospectively by two radiologists without any clinical or histopathological information. The specific points evaluated were location, shape, margin, internal architecture, and intensity level on both US and MR, posterior echo enhancement on US, and capsule-like lining of the tumor on MR. RESULTS: The findings concerning the shape and margin on US and MR were in fairly good agreement. Concerning the findings of the internal architecture, US could reveal the minute structures of the tumor while MR demonstrated differences in the signal intensities of histological tissue types of the various tumors. The posterior echo enhancement on US and the capsule-like lining on MR of the tumors were also useful for the diagnosis. CONCLUSION: Our results suggest that the combination of US and MR is useful for examining soft tissue masses in the parotid region to make a more accurate diagnosis, and not just differentiate malignant lesions from those which are benign.

Adolescent↗
PubMed2000

Tumor recurrence criteria for postoperative contrast-enhanced computed tomography after surgical treatment of oral cancer and flap repair.

OBJECTIVE: To characterize the computed tomography (CT) findings that distinguish cancer recurrence from postoperative changes that mimic such recurrence. STUDY DESIGN: We evaluated a total of 72 CT scans from 32 patients who had undergone surgery with either pectoralis major myocutaneous flap or forearm flap. The observers evaluated the presence and pattern of enhancement, the presence of low density areas, and changes in the adipose tissue of the flap. RESULTS: A persistent zone of high attenuation over 6 months suggested the high possibility of recurrence. However, an enhancement within 6 months occurred both with the recurrent tumor and with postoperative tissue. In the patients with recurrence (n = 12), the enhanced areas were focal (n = 8) or diffuse (n = 4). Focal-type recurrence often occurred at the posterior margin. The presence of low-density areas and changes in the adipose tissue in the flap are also helpful for detecting recurrence. CONCLUSIONS: The combination of several features seen on CT images can be useful in differentiating tumor recurrence from postoperative tissue changes.

Adipose Tissue↗
PubMed2000

Multivariate feature analysis of sonographic findings of metastatic cervical lymph nodes: contribution of blood flow features revealed by power Doppler sonography for predicting metastasis.

BACKGROUND AND PURPOSE: Sonographic criteria of the lymph node have been found to be good indicators for metastatic lymph nodes. We determined which sonographic features are most predictive of metastasis in cervical lymph nodes among patients with head and neck cancer. METHODS: Gray-scale and power Doppler sonograms were retrospectively analyzed in 133 cervical lymph nodes (57 metastatic and 76 reactive nodes) from 52 patients with head and neck cancer. The gray-scale sonographic features of the presence or absence of hilar echoes, parenchymal echogenicity, and short and long axis lengths as well as the power Doppler features of normal hilar flow and abnormal parenchymal flow were evaluated. Univariate and multivariate logistic regression analyses were conducted to determine the relative value of each sonographic feature. RESULTS: At univariate analysis, all sonographic features assessed were found to be important. Multivariate analysis, however, suggested that the presence or absence of hilar echoes, increases in short axis length, and the presence of normal hilar flow were the only sonographic features that were predictive of reactive (presence of hilar echoes and hilar flow) and metastatic (increases in short axis length) lymph nodes. Although multivariate analysis did not indicate any significant contribution of the color-flow criteria for predicting metastatic nodes, the color-flow criteria appeared to improve the overall diagnostic accuracy for the less experienced observer. CONCLUSION: The sonographic criteria most predictive of metastatic cervical lymph nodes were absent hilar echoes and increases in short axis length, as assessed by logistic regression analysis. Compared with these gray-scale criteria, color-flow criteria had fewer predictive advantages.

Adult↗
PubMed2000

Abnormal blood flow to the submandibular glands of patients with Sjögren's syndrome: Doppler waveform analysis.

OBJECTIVE: To assess abnormalities in blood flow to the submandibular glands of patients with Sjögren's syndrome (SS). METHODS: Doppler waveform analysis was performed on the facial artery to assess blood inflow to the submandibular gland of 21 patients with primary SS and 69 healthy subjects. Blood flows were compared before and after secretory stimulation with lemon extracts. RESULTS: The facial artery of healthy subjects in the resting state exhibited a biphasic waveform with a high systolic peak and a prominent second peak of compliance followed by a low diastolic flow. In contrast, the waveform of patients with SS was more uniform compared with the healthy subjects, substantiated by decreased resistive and pulsatility indices, suggesting a hyperemic state of the downstream vascular bed. After stimulation of salivary secretion, the facial artery of healthy subjects responded by decreasing resistive and pulsatility indices, waveform changes indicative of increased blood inflow to the submandibular gland. In contrast, the facial artery of patients with SS responded insufficiently to the stimulation, with the magnitude of changes in the resistive and pulsatility indices being significantly lower than those of the controls. Doppler waveform abnormalities were correlated with the severity of gland damage, supporting a close connection between abnormal blood inflow to the salivary gland and impaired secretory function in SS. CONCLUSION: Our findings suggest that blood inflow responses to secretory stimulation may be defective in the salivary glands of patients with SS.

Adult↗
PubMed1999

Assessment of image quality in dental radiography, part 1: phantom validity.

OBJECTIVE: The purpose of this study was to describe and validate an image-quality phantom to be used in dental radiography for comparison of film and digitally acquired images. STUDY DESIGN: An aluminum block of 12 steps, with 7 holes in each step, was covered by acrylic blocks. This phantom was radiographed with Kodak Ultra-speed and Ektaspeed Plus films at 70, 65, and 60 kVp with the whole exposure range available. All together, 50 dental films were randomly sequenced and presented to 7 observers. The average number of perceptible holes from all steps was plotted against exposure for each tube voltage and film type, generating a modified perceptibility curve. The tentative optimum exposure level was determined from perceptibility curves in each experimental condition and compared with that determined by means of the standard aluminum stepwedge and the preset time of the x-ray machine. The density range of this phantom at the optimum exposure was compared with that of clinical dental radiographs. Validity of the phantom was evaluated according to the optimum exposure level from the modified perceptibility curves and the overall density range. Finally, the average maximum numbers of perceptible holes at the tentative optimum exposure level were compared for each tube voltage and film type. The statistical test used was a 2-way factorial analysis of variance. RESULTS: The exposure at the perceptibility curve peak approximated that obtained by means of the standard aluminum step-wedge and the time preset by the manufacturer. The overall density range at the perceptibility curve peak covered the clinical density range for each tube voltage and film type. There were no statistically significant differences between film types or among tube voltages. CONCLUSIONS: The x-ray attenuation range for this phantom seemed to approximate clinical conditions. In addition, differences in image quality could be quantitatively evaluated by means of the number of the holes seen in the phantom.

Absorptiometry, Photon↗
PubMed1999

Assessment of image quality in dental radiography, part 2: optimum exposure conditions for detection of small mass changes in 6 intraoral radiography systems.

OBJECTIVE: The purpose of this study was to compare 2 film systems and several digital intraoral systems with regard to visual image quality through use of a test phantom developed for this purpose. STUDY DESIGN: The detectors used for digital imaging were as follows: Computed Dental Radiography (CDR), Digora, Dixel, and Sens-A-Ray without scintillator layer. Two types of digital images were prepared for the observer performance test: one with original gray scales and another with contrast enhancement. Images with and without enhancement from the 4 systems were displayed to 7 observers. The change in the average number of perceptible holes was plotted against exposure, and modified perceptibility curves were created and compared with curves for the film systems. The exposure level at which the maximum number of holes was perceived was defined to be optimum. The optimum exposure levels were determined for each digital system and compared with that of the film systems. At the optimum exposure, the average maximum numbers of perceptible holes in each digital system with and without contrast enhancement were compared with the maximum numbers for the film systems. The minimum exposure levels were determined to be those at which the number of perceptible holes exceeded the number for film, and the possibility of exposure reduction was evaluated. RESULTS: All digital systems except the Digora system showed lower optimum exposures than E-speed film. In all digital images without enhancement, however, the maximum number of perceptible holes was significantly lower than that for the film systems at that exposure. With contrast enhancement, all digital systems except the Sens-A-Ray system showed visibility superior to that of the film systems. With the CDR, Digora, and Dixel systems, exposures could be further reduced by a considerable amount, with greater retention of information than was associated with film. CONCLUSIONS: Our results strongly suggest that digital systems, if properly used, can exceed film systems in the detection of small mass changes.

Contrast Media↗
PubMed1999

Prediction of perceptibility curves of direct digital intraoral radiographic systems.

OBJECTIVES: To derive and test a method to predict Perceptibility Curves (PCs) for direct digital intraoral radiographic systems. METHODS: A test object was used to determine the performance of an average observer with respect to the threshold contrast and internal noise of the human visual system. These data were combined with system parameters to predict PCs mathematically. RESULTS: Data on the performance of an average observer could be defined to obtain values of the effective threshold contrast as a function of background gray level. This function combined with the gamma-value of the system predicted PCs that agreed well with PCs obtained in the conventional way. CONCLUSION: It is possible to predict PCs from a limited number of system parameters together with predetermined data on an average observer.

Artifacts↗
PubMed1999

Doppler spectral waveform analysis of arteries of the hand in patients with Raynaud's phenomenon as compared with healthy subjects.

OBJECTIVE: We sought to characterize and compare the blood flow patterns of peripheral arteries of the hand in patients with Raynaud's phenomenon and in healthy subjects. SUBJECTS AND METHODS: We used Doppler sonography to assess the blood flow pattern of the proper palmar digital artery and the deep radial arch in the hands of 79 healthy subjects and 24 patients with primary and secondary Raynaud's phenomenon. We determined the resistive index, pulsatility index, peak systolic velocity, and end-diastolic velocity of these peripheral arteries at rest and after cold immersion. RESULTS: The proper palmar digital artery of healthy subjects showed higher end-diastolic velocities and lower resistive indexes than did the deep radial arch. Compared with healthy subjects, patients with Raynaud's phenomenon had higher resistive and pulsatility indexes but lower peak systolic and end-diastolic velocities in these arteries. Accordingly, the differences in end-diastolic velocity and resistive index seen in the two peripheral arteries of healthy subjects were not seen in patients with Raynaud's phenomenon. Analysis of receiver operating characteristic curves showed high diagnostic accuracy in detecting the disease. Cold-immersion studies revealed that for the proper palmar digital arteries throughout the time after immersion, all these Doppler parameters were significantly lower for the velocities and higher for the indexes in patients with Raynaud's phenomenon than in healthy subjects. CONCLUSION: Taken together, these results suggest a legitimate role for Doppler sonography in the assessment of Raynaud's phenomenon.

Adult↗
PubMed1998

Mucoepidermoid carcinoma in the mandible: findings of panoramic radiography and computed tomography.

Six patients with mucoepidermoid carcinoma in the mandible were studied with both panoramic radiography and computed tomography. Lesion shape and margin were evaluated on panoramic radiography, and bony expansion and cortical plate destruction were evaluated on computed tomography. In addition, a possible correlation among radiographic findings, histologic findings, and prognosis was investigated. Lesions found on panoramic radiography were classified into three types; each type pertained to two of the six patients. The lesion types were as follows: cystic, characterized by a large, cystic radiolucent area; rarefying, characterized by rarefying changes of the trabeculae; and infiltrative, characterized by a central ill-defined area of bony destruction. The results show that computed tomography is useful in the identification of tumor extent, bony expansion, and cortical plate destruction resulting from tumors. None of the patients whose lesions were of the cystic or rarefying type showed evidence of disease after surgery. In contrast, both of the patients whose lesions were of the infiltrative type died of their tumors. Histologic findings of the cystic and rarefying types showed tumors that were well-differentiated or moderately well-differentiated, whereas findings of the infiltrative type showed poorly differentiated tumors. Radiographic findings correlated with histologic findings and prognosis of mucoepidermoid carcinoma in the mandible in this limited series.

Adult↗
PubMed1997

Submandibular gland duct endoscopy. Diagnostic value for salivary duct disorders in comparison to conventional radiography, sialography, and ultrasonography.

The purpose of this study is to evaluate the usefulness of endoscopy as a procedure for the diagnosis of submandibular gland duct disorders. Endoscopy of the submandibular glands was performed on 12 patients with symptoms of obstructive sialoadenitis to identify the cause of obstruction. The endoscopic findings were then compared to those of diagnostic procedures such as conventional radiography, sialography, and ultrasonography. Six normal subjects also underwent endoscopy to better understand the normal findings of the duct system. Endoscopy demonstrated salivary gland calculus in 5 of 12 patients, which was revealed as filling defects on sialograms and as strongly echogenic structures on ultrasonograms in 4 of the patients. Endoscopy revealed secretion plugs, secretion plaques, and/or stenosis, which could not be seen by any other diagnostic procedures in 5 patients, as the cause of recurrent swelling in all 7 patients not demonstrating sialolith. Abnormal findings of the duct wall such as vasodilatation, fibrosis, edema, or erythema were seen in four patients, three of whom exhibited dilatation of the duct system on sialograms. In four patients, a decreasing internal echo level of the gland was seen on ultrasonograms. Our initial results for submandibular gland duct endoscopy thus appear to be promising.

Adult↗
PubMed1997

Imaging findings of lipomas in the orofacial region with CT, US, and MRI.

OBJECTIVE: The aim of this study was to document retrospectively the imaging findings of lipomas with the use of computed tomography, ultrasonography, and magnetic resonance imaging. STUDY DESIGN: Thirteen patients with 11 lipomas and 2 lipomatoses were evaluated. Eleven cases were examined by computed tomography, 9 by ultrasonography, and 3 by magnetic resonance imaging. RESULTS: Lipomas had a density ranging from -134 to -83 Hounsfield units, (mean-108) on the computed tomography images. The margins were ill defined in 9 of 10 cases. The superficial muscles were displaced externally in 8 cases and internally in 2 cases. With ultrasonography, 8 lesions were hypoechoic, and one was hyperechoic. All three lesions had a high signal intensity on both T1- and T2-weighted images. CONCLUSIONS: Lipomas had a specific range of computed tomography Hounsfield unit values and also displaced the surrounding soft tissue. Although some variation in the ultrasonographic appearance was observed, the lesions tended to be hypoechoic. These findings may be useful for diagnosing lipomas in the orofacial region.

Adolescent↗