Kazunori Yoshiura

Preparation of highly oriented polyarylenevinylene thin films by the Langmuir-Blodgett technique

We obtained three kinds of polyarylenevinylene(poly (p-phenylenevinylene), poly(2,5-dimethoxy-p-phenylenevinylene) and poly(2,5-thienylenevinylene)) thin films with the Langmuir-Blodgett (LB) technique. Stable polyarylenevinylene precursor-anionic amphiphile complex monolayers were formed at the air-precursor aqueous solution interface through adsorption of the precursors onto an amphiphilic monolayer. The polyion complex monolayers could be transferred on substrates by the LB technique. The polyarylenevinylene precursor LB films were converted to polyarylenevinylene films with a heat treatment under nitrogen flow. Extension of the mean n conjugation length and planar orientation of the conjugation sequences were realized in the poly (p-phenylenevinylene) and poly(2,5dimethoxy-p-phenylenevinylene) LB films.

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.

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.

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.

Ultrasonographic evaluation of inflammatory changes in the masseter muscle.

The ultrasonographic images of 32 patients with inflammatory change in the masseteric region were investigated to clarify the characteristic findings and to evaluate the utility of ultrasonography. Inflamed masseter muscles frequently demonstrated reduction of echo intensity and complete or partial absence of hyperechoic bands. The mean thickness of the masseter muscle on the unaffected side was 8.6 mm, whereas that on the affected side was 12.9 mm. Nine of 10 patients with heterogeneous hypoechoic area, but only 1 of 10 patients with homogeneous hypoechoic area, had received surgical treatment before ultrasonographic examination.

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.

Pharmacokinetic analysis based on dynamic contrast-enhanced MRI for evaluating tumor response to preoperative therapy for oral cancer

To evaluate whether a pharmacokinetic analysis is useful for monitoring the response of oral cancer to chemoradiotherapy (CRT).

In vivo Cross-sectional Area of Human Jaw Muscles Varies with Section Location and Jaw Position

Muscle cross-sectional area (CSA) is used as a measure for maximum muscle force. This CSA is commonly determined at one location within the muscle and for one jaw position. The purpose of this study was to establish a method to standardize the analysis of the CSA of the masticatory muscles in vivo, and to compare the CSAs along their entire length for two different jaw positions (opened and closed). The CSAs in the planes perpendicular to the long axes of the masseter, medial, and lateral pterygoid muscles were measured in ten normal young adult subjects by magnetic resonance imaging. Our results showed large differences among the muscles and a non-uniform change in CSA after jaw-opening. The method enables the CSA measurement to be standardized in vivo, and allows for a correct comparison of CSAs in different skull morphologies.

Sonographic analysis of recurrent parotitis in children: a comparative study with sialographic findings.

OBJECTIVE The sonographic features of recurrent parotitis in children were studied to clarify a relationship between sonographic and sialographic findings in this disease. STUDY DESIGN Twenty-one glands (7 on follow-up) were examined by 7.5 MHz ultrasonography and sialography. Echo intensity level, distribution of the internal echoes, and size of hypoechoic areas were compared with the size of punctate shadows on the sialograms. Twenty other histopathologic specimens were analyzed to investigate the entity of hypoechoic areas. RESULTS Sonography showed hypoechoic, heterogeneous internal echoes, the level of which increased as the punctate shadows enlarged. Hypoechoic areas, all of which were larger than the sialographic punctate shadows, were observed in 62% of the glands. Histopathologic analysis suggests that these hypoechoic areas represent dilated peripheral ducts with lymphocytic infiltration. Sonography was likely to detect changes over time more sensitively than sialography. CONCLUSIONS Sonography should be performed as the test of first choice, both in the primary and follow-up stages, in cases of recurrent parotitis in children.

Size and Orientation of Masticatory Muscles in Patients with Mandibular Laterognathism

Size measurements of jaw muscles reflect their force capabilities and correlate with facial morphology. Using MRI, we examined the size and orientation of jaw muscles in patients with mandibular laterognathism in comparison with a control group. We hypothesized that the muscles of the deviated side would be smaller than those of the non-deviated side, and that the muscles of both sides would be smaller than in controls. In patients, a comparison of deviated and non-deviated sides showed, in orientation, differences for masseter and medial pterygoid muscles, but, in size, differences only for the masseter muscle. Nevertheless, muscle sizes in patients were much smaller than in controls. Lateral displacement of the mandible can explain the orientation differences, but not the smaller muscle size, in patients. It is possible that the laterodeviation initiates an adaptive process in the entire jaw system, resulting in extensive atrophy of the jaw muscles.