[Evaluation of AEC Consistency in Digital X-ray Imaging Systems]

The Japan Network for Research and Information on Medical Exposures (J-RIME) established the diagnostic reference level (DRL) and is advancing optimization of radiation protection. We believe that the difference in the imaging dose between facilities may be due to the fact that automatic exposure control (AEC) adjustment is not unified among manufacturers. The consistency of AEC is specified in JIS 4751-2-54, but it is not applicable to digital X-ray imaging systems because it is for optical density of analog X-ray imaging systems. This article evaluates the consistency of AEC in digital X-ray imaging systems. The AEC consistency was compared with the AEC-estimated dose from the air kerma (K_AEC) using the phosphor-based imaging plate placed at the back of the AEC detector. We measured the AEC tube voltage and subject thickness characteristics (tracking) of four types of digital X-ray imaging systems at three facilities. In the test of tube voltage characteristics, the average K_AEC values at all tube voltages were 2.37±0.04  µGy for A system, 7.30±1.44  µGy for B system, 3.53±0.13  µGy for C system, and 5.70±0.18  µGy for D system. The relative errors were +2.6 to -1.8% for A system, +25.3 to -22.6% for B system, +5.2 to -1.4% for C system, and +2.5 to -4.4% for D system. In the subject thickness characteristics test, the average K_AEC values for all Al thicknesses were 2.34±0.02  µGy for A system, 5.95±0.23  µGy for B system, 4.25±1.12  µGy for C system, and 5.03±1.27  µGy for D system. The relative errors were +1.0 to -0.9% for A system, +4.1 to -5.0% for B system, +40.5 to -28.1% for C system, and +19.7 to -42.9% for D system.

Pharmacokinetic functions of human induced pluripotent stem cell-derived small intestinal epithelial cells

To develop a novel intestinal drug absorption system using intestinal epithelial cells derived from human induced pluripotent stem (iPS) cells, the cells must possess sufficient pharmacokinetic functions. However, the CYP3A4/5 activities of human iPS cell-derived small intestinal epithelial cells prepared using conventional differentiation methods is low. Further, studies of the CYP3A4/5 activities of human iPS-derived and primary small intestinal cells are not available. To fill this gap in our knowledge, here we used forskolin to develop a new differentiation protocol that activates adenosine monophosphate signaling. mRNA expressions of human iPS cell-derived small intestinal epithelial cells, such as small intestine markers, drug-metabolizing enzymes, and drug transporters, were comparable to or greater than those of the adult small intestine. The activities of CYP3A4/5 in the differentiated cells were equal to those of human primary small intestinal cells. The differentiated cells had P-glycoprotein and PEPT1 activities equivalent to those of Caco-2 cells. Differentiated cells were superior to Caco-2 cells for predicting the membrane permeability of drugs that were absorbed through a paracellular pathway and via drug transporters. In summary, here we produced human iPS cell-derived small intestinal epithelial cells with CYP3A4/5 activities equivalent to those of human primary small intestinal cells.

Development of canine X-chromosome inactivation pattern analysis for the detection of cell clonality by incorporating the examination of the SLIT and NTRK-like family member 4 (SLITRK4) gene

X-chromosome inactivation pattern (XCIP) analysis can be used to assess the clonality of cell populations of various origin by distinguishing the methylated X chromosome from the unmethylated X chromosome. In this study, the utility of XCIP analysis was improved by incorporating the examination of AC dinucleotide repeats in SLIT and NTRK-like family member 4 (SLITRK4) gene into the previously reported CAG repeat examination of androgen receptor (AR) gene in dogs. The rate of heterozygosity when both genes were analysed (125/150, 83.3%) was higher than AR gene examination alone (86/150, 57.3%). Blood samples from heterozygous dogs in either AC-1 or AC-2 of SLITRK4 gene were examined for the corrected inactivation allele ratio (CIAR), resulting in the determination of a reference range of CIAR <3.8 in non-neoplastic cell/tissue samples. Using this analytical method, 49% (21/43) of neoplastic tissue samples from dogs showed a CIAR >3.8, indicating the presence of a clonal population. Through the present study, the availability of canine XCIP analysis was improved by incorporating the examination of the SLITRK4 gene, providing a highly useful laboratory examination system for the detection of the clonality of various cell/tissue samples in dogs.

[Effect of Interspaces of Anti-scatter Grid on the Image Improvement Factor]

The standard general purpose of anti-scatter girds: JIS Z 4910: 2015 (IEC 60627: 2013) has been revised, with the new addition of an image improvement factor (Q) to the physical characteristic. Using aluminum (Al) and fiber-interspaced anti-scatter grids; we studied the meaning of Q by calculating each of the physical characteristics and assessing the image. The experimental method was based on JIS Z 4910: 2015. The two anti-scatter grids had a grid ratio of 12: 1 and a strip frequency of 40 cm^-1. Assessment items consisted of grid exposure factor (B), grid selectivity (Σ), contrast improvement ratio (K), and Q. In addition, the contrast to noise ratio (CNR) and contrast-detail curve (CD-curve) were determined from the contrast-detail phantom image, and the inverse image quality figure (IQF) was then calculated from the CD-curve. Compared to the Al-interspaced anti-scatter grid, the fiber-interspaced anti-scatter grid had B at 0.87, Σ at 0.95, K at 0.99, and Q at 1.14. In the assessment of the contrast-detail phantom image, the fiber-interspaced anti-scatter grid had an IQF of 1.02 times and a CNR of approximately 1.24 times when compared to the Al interspaced anti-scatter grid. The fiber-interspaced anti-scatter grid was superior with respect to the B and Q of the physical characteristics and to the CNR of image quality assessment.

[Development of a simple measurement system for routine management of X-ray equipment]

Routine management of X-ray equipment is critically important, but due to the high cost of commercial management systems it is currently not practical to deploy this valuable instrumentation at every clinical facility. This led us to develop a simple measurement system for routine management purposes that can be deployed for around ¥100 thousand in materials. The system consists of an X-ray output meter, a clamp-type X-ray tube current meter (clamp meter), and a digital oscilloscope. Compared to a standard fluorescence meter, the X-ray output meter provides equivalent accuracy and reproducibility of X-ray tube voltage, X-ray tube current, and irradiation time changes, while also displaying the X-ray output time. The clamp meter must be periodically calibrated, however provides equivalent accuracy and reproducibility to a direct contact meter, while also displaying net X-ray tube current and loading time. Finally, the oscilloscope is able to estimate the waveform of X-ray tube voltage by monitoring each waveform, thus making it an extremely useful instrument for day-to-day management of X-ray equipment installed at clinical facilities.

Characteristic power Doppler sonographic images of tumorous and non-tumorous buccal space lesions

OBJECTIVES

The aim of this study was to evaluate the characteristic power Doppler sonographic images of buccal space tumorous and non-tumorous lesions.

METHODS

48 patients with buccal space lesions were evaluated with greyscale sonography followed by power Doppler sonography with a 12 MHz linear transducer. On greyscale sonography, buccal space lesions were assessed for the boundary (clear or unclear), echogenicity (hypoechoic or isoechoic) and internal architecture (homogeneous or heterogeneous). Power Doppler sonography was performed to evaluate the vascular signals within the buccal space lesions.

RESULTS

48 lesions were found in the 48 patients; of these 48 lesions, 28 were tumourous and 20 were non-tumourous. In the 28 tumours, 15 cases showed clear boundaries, 15 cases were hypoechoic relative to adjacent tissues and 22 cases presented with a heterogeneous appearance on greyscale sonography. The internal vascularity of 19 tumours was shown using power Doppler sonography. In the 20 non-tumorous lesions, 11 cases showed clear boundaries, 17 cases were hypoechoic relative to adjacent tissues and 13 cases presented with a homogeneous appearance on greyscale sonography. 18 non-tumorous lesions showed no internal vascularity using power Doppler sonography. Logistic multivariate regression analysis between the tumour group and the non-tumorous lesions group demonstrated that the internal architecture (odds ratio = 8.270, p = 0.029) and vascular signals (odds ratio = 17.533, p = 0.003) were significant variables.

CONCLUSIONS

Power Doppler sonography is a useful technique for the differential diagnosis of tumorous and non-tumorous buccal space lesions.

Characterization of mandibular fractures using 64-slice multidetector CT

OBJECTIVE

The aim of this study was to characterize mandibular fracture locations using 64-slice multidetector CT (MDCT).

METHODS

CT scans of 138 patients with mandibular fractures who underwent 64-slice MDCT were studied. Mandibular fractures were classified into five types: median, paramedian, angle, condylar and coronoid process. Statistical analysis for the relationship between multiple fractures and type of mandibular fractures was performed using χ(2) test with Fisher's exact test.

RESULTS

The percentage of multiple mandibular fractures was 80.9% median type, 74.3% paramedian type, 52.9% angle type and 60.9% condylar type. The resultant data showed a significant relationship between multiple fractures and the median type (p = 0.000), paramedian type (p = 0.002) and condylar type (p = 0.003).

CONCLUSION

The results suggest that multiple fractures are related to the type of mandibular fractures.

Magnetic resonance characteristics of temporomandibular joint disc displacement in elderly patients

OBJECTIVES

The purpose of this study was to evaluate the MR characteristics of temporomandibular joint (TMJ) disc displacement in elderly patients.

METHODS

Of the MR images of 1660 TMJs in 847 patients with disc displacement who underwent MRI for suspected temporomandibular disorders, 301 TMJs in 154 patients aged over 50 years were studied as an elderly group. These MR images of the elderly group were compared with those of a control group (1359 TMJs in 693 patients aged under 51 years) concerning disc displacement with or without reduction, joint effusion and osteoarthrosis.

RESULTS

The incidence of disc displacement with osteoarthrosis was significantly different between the elderly (41.9%) and the control (19.8%) groups (p = 0.000). Logistic multivariate regression analysis demonstrated that the osteoarthrosis was a significant variable (odds ratio = 2.94, p = 0.000).

CONCLUSIONS

This study suggests that MR characteristics of TMJ disc displacement in elderly patients includes osteoarthrosis.

Maxillary bone invasion by gingival carcinoma as an indicator of cervical metastasis

OBJECTIVES

To evaluate the significance of maxillary bone invasion by gingival carcinoma as an indicator of cervical metastasis.

METHODS

Twenty-one patients with squamous cell carcinoma of the upper gingiva were included in the study. The extent of bone invasion was assessed by dental CT. Six patients had cervical metastases at the initial examination and eight more developed them during the 2-year follow-up period. The relationship of cervical metastases with age and gender of these patients, as well as with the size of the lesion and extent of bone invasion, was examined by logistic multivariate regression analysis.

RESULTS

There was a significant relationship between the presence of bone invasion and the presence of cervical metastasis (P<0.05).

CONCLUSIONS

Maxillary bone invasion is an indicator of cervical metastasis in gingival carcinoma.

Mandibular bone invasion by gingival carcinoma on dental CT images as an indicator of cervical lymph node metastasis

OBJECTIVES

To evaluate the significance of mandibular bone invasion by gingival carcinoma revealed by reformatted dental CT images as a prognostic indicator of cervical metastasis.

METHODS

Thirty-two patients with squamous cell carcinoma of the lower gingiva were examined by dental CT. Cervical metastases and survival rates of these patients were analysed in relation to their clinical characteristics, histologic grading based on gingival biopsy, and mandibular bone invasion using reformatted dental CT imaging diagnoses prior to surgery. The dental CT images were classified into four types: Class I, no bone invasion; Class II, invasion confined to the alveolus; Class III, invasion extending between the alveolus and the mandibular canal; and Class IV, invasion beyond the mandibular canal.

RESULTS

Logistic multivariate regression analysis showed that bony invasion identified on dental CT images was a significant prognostic factor in cervical metastases (P=0.028). The 5-year overall survival rates of Classes I, II, III, and IV were 100% (n=9), 76.2% (n=9), 71.4% (n=7), and 28.6% (n=7), respectively.

CONCLUSIONS

The evaluation of mandibular bone invasion using dental CT images is useful as a prognostic indicator of cervical metastasis for patients with gingival carcinoma.

[Characteristics of a new non-invasive x-ray output analyzer]

The X-ray systems study group used the Victoreen NERO mAx model 8000, a new non-invasive X-ray output analyzer, to measure the tube voltage, tube voltage waveform, tube current, and irradiation time for conditions corresponding to general radiography and mammography. The measurement results were then compared with those obtained using a conventional invasive measuring instrument. The peak values of the tube voltage measured by the NERO mAx and the invasive measuring instrument were compared. The NERO mAx had a good measurement error range of -1.2 to +0.9 kV. For tube current measurement by the NERO mAx, the maximum error for general radiography conditions was +11 mA and that for mammography conditions was +6 mA. For irradiation time measurement, the value for general radiography conditions was slightly greater and the value for mammography conditions was slightly less than the corresponding values obtained by the invasive measuring instrument. If radiation quality is changed during measurement of the characteristics, measurement values change. Since the NERO mAx incorporates two types of X-ray detectors, it shows good measurement reproducibility. The NERO mAx has been shown to have suitable characteristics for use as a measuring instrument for constancy tests. In the future, constancy tests should be used to quantitatively control the factors determining clinical image quality.

Congener-specific characterization of PCDDs/PCDFs in atmospheric deposition: comparison of profiles among deposition, source, and environmental sink

In order to examine the input of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) from various airborne sources to environmental sinks, the atmospheric deposition of congener-specific PCDDs/PCDFs was investigated. Homologue and congener profiles of atmospheric depositions were compared with those of sources and environmental sinks to identify the relationship among atmospheric depositions, sources, and environmental sinks. Moreover, factor analysis was used to detect similarities, differences, and relationships of the variations in deposition fluxes among congeners within the same and different homologues. The results showed that the congener profiles of the atmospheric depositions were primarily determined by those of combustion emissions. Several congeners in some specific samples showed higher proportions within each homologue compared with representative depositions. This result can be partly explained by the influence of impurities in herbicides, 1,3,5-trichloro-2-(4-nitrophenoxy) benzene (CNP) and pentachlorophenol (PCP). The congener profiles of combustion emissions, representative depositions, and urban soils were very similar although their homologue profiles varied. This implied that PCDDs/PCDFs in the urban soils originate from the deposition of combustion emissions and that all congeners within each homologue behave identically in air and soil. Although the congener profiles of the representative depositions were different from those of the sediments in Tokyo Bay and the soil of a paddy field, the combination of congener profiles of the representative depositions and of the impurities in herbicides. CNP and PCP, can explain the congener profiles of the sediments and the paddy field. This study showed that congener-specific data are useful for source identification.

Atmospheric deposition of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls in the Kanto Region, Japan

The atmospheric bulk (dry and wet) deposition of dioxins was investigated at four locations (Tokyo, Yokohama, Tsukuba, and Tanzawa) in the Kanto region (in Japan) over one year using a stainless-steel pot. Annual average polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/PCDF) deposition fluxes were estimated to be from 450 to 1300 ng/m2/yr, and the annual average TEQ fluxes from 5.7 to 17 ng-TEQ/m2/yr at the four locations. The PCDD/PCDF deposition flux was higher in winter than in summer. The deposition flux could be related to ambient temperature, particularly for less chlorinated PCDDs/PCDFs, while the deposition flux is not necessarily related to the amount of precipitation. The PCDD/PCDF deposition flux increased as the particle deposition flux increased, for the winter samples. Based on the ratio of the PCDD/PCDF deposition fluxes to the particle deposition fluxes, the contribution of the reentrainment of soil particles to the TEQ of PCDD/PCDF deposition was considered to be negligible in this region. Based on the air concentrations monitored near our deposition sampling points by the municipalities, the ratio of the annual deposition flux to the annual average air concentration was roughly estimated to be 0.082 cm/s. The range of deposition flux in the Kanto region was estimated to be from 1.5 to 31 (median: 9.8) ng-TEQ/m2/yr based on the range of air concentration data measured by the municipalities. The total annual deposition flux in the entire Kanto region was estimated to range from 50 to 900 g-TEQ/yr (median 320 g-TEQ/yr). This estimated flux was of the same order as the sum of estimated emissions from municipal solid waste incinerators and industrial waste incinerators in the Kanto region. The contributions of dioxin-like PCBs in Yokohama, Tsukuba, and Tanzawa depositions were less than 10% of the total TEQ; however, in Tokyo it was almost equal to or more than 50%.

Diagnostic accuracy of computed tomography for cervical metastases at different anatomical levels in carcinoma of the tongue

OBJECTIVES

To evaluate the variation in diagnostic accuracy of CT in the assessment of cervical lymph node metastases from tongue carcinoma at different anatomical levels.

METHODS

Sixty-one patients with squamous cell carcinoma of the tongue who underwent radical neck dissection were included in this study. The CT and histopathological findings at nodal levels I-V were compared for the presence or absence of lymph node metastases. Sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) of CT were evaluated for each nodal level.

RESULTS

The sensitivity of CT was: level I, 85%; level II, 77.8%; level III, 53.3%; level IV, 66.7% and level V, 25%. There was a significant difference in the sensitivity between the level I-II group (80.9%) and level III-V group (53.6%) (P=0.012). There was no significant difference in the specificity, NPV, and PPV between the two groups.

CONCLUSIONS

The sensitivity of CT in detecting cervical lymph node metastases was significantly smaller at levels III-V than at levels I-II.

Clinicopathological study of carcinomas of the lip and the mucosa of the upper and lower lips

BACKGROUND

Lip carcinomas are rare oral tumors, and there have been few reports of lip carcinoma in Japan.

METHODS

Of 914 patients with oral carcinomas treated between January 1980 and December 1998, 12 (1.3%) had lip carcinoma and 5 (0.5%) had lip mucosal carcinoma. We investigated the clinicopathological features of these 17 patients.

RESULTS

Of the 12 patients with carcinoma of the lip, 10 had squamous cell carcinomas (9, external lower lip; 1 commissures) and 2 had mucoepidermoid carcinomas (external upper lip). Of the 5 patients with lip mucosal carcinoma, 3 had squamous cell carcinomas (2, mucosa of the lower lip; 1, mucosa of the upper lip), 1 had mucoepidermoid carcinoma (mucosa of the lower lip), and 1 had acinic cell carcinoma (mucosa of the lower lip). Of the 12 patients with lip carcinoma, 9 were classified as stage I, 2 as stage II, and 1 as stage III; all 5 of the patients with lip mucosal carcinoma were stage I. Five patients with lip carcinoma were treated by resection, 5 by a combination of resection and reconstruction, and 2 by radiotherapy alone. All patients with lip mucosal carcinoma were treated by resection. After the initial therapy, 3 patients without neck dissection had regional recurrences and received delayed neck dissection, and 2 died with neck regional recurrence after dissection. The 5-year cumulative survival rates of the patients with lip carcinoma and those with lip mucosal carcinoma were 82.5% and 80.0%, respectively.

CONCLUSION

We suggest that early-stage carcinomas of the lip and of the mucosa of the upper and lower lips are frequent, and we found that the outcome of these patients was excellent. However, an aggressive therapeutic approach to the lip carcinoma patient with cervical metastasis appears warranted, in an attempt to improve locoregional control and ultimate survival.

Identifying sources and mass balance of dioxin pollution in Lake Shinji Basin, Japan

On the basis of congener-specific analysis of dioxins in a dated sediment core, the sources and behavior of dioxins in Lake Shinji Basin, Japan, were estimated. The dioxins in the core showed that their deposition in the lake increased rapidly during the 1960s, peaked in the early 1970s, and then decreased gradually. Principal component analysis of the congener-specific data showed that three major sources existed: pentachlorophenol (PCP), chloronitrophen (CNP), and combustion. PCP and CNP are paddy field herbicides used extensively in the basin. The time trends of source contributions were estimated by multiple regression analysis using the source profiles. The results revealed that dioxin emission from PCP and CNP herbicides was high in the 1960s and the early 1970s, respectively. The contributions from PCP, CNP, and combustion in recent surface sediment were about 68, 16, and 16% in terms of total amount of dioxins. From the decreasing trend of dioxin deposition in the lake after extensive herbicide use, the amount of dioxins that accumulated in the agricultural soil in the basin was estimated to have decreased by about 2%/yr or a half-life of about 35 yr, indicating that dioxin runoff from agricultural fields would continue for a long time.

Thermal conductivity of a self-frequency-doubling laser crystal measured by use of optical methods

We present a new all-optical technique to measure the thermal conductivity of laser crystals. This technique can be used for crystals that are too small for direct measurement of thermal conductivity. We used this technique to measure the thermal conductivities of Nd:LYAB, with the result of 44 +/- 6% compared with that of Nd:YAG thermal conductivity.

Correlation between tumor consistency and cervical metastasis in tongue carcinoma

BACKGROUND

The purpose of this study was to assess the correlation between the tumor consistency and cervical lymph node metastasis in tongue carcinoma.

METHODS

Fifty-three patients with squamous cell carcinoma of the tongue were examined with an instrument capable of measuring consistency. These cases were compared in relation to TN classification, pathologic status of nodes, and consistency.

RESULTS

The mean values of consistency in tongue carcinoma were 19. 7 +/- 2.9 g, 13.6 +/- 3.7 g, 27.4 +/- 4.5 g, and 21.2 +/- 6.7 g, corresponding to pathologically positive node group (PN[+]) in T1, pathologically negative node group (PN[-]) in T1, PN(+) in T2, and PN(-) in T2, respectively. Difference in consistency between PN(+) and PN(-) was significant (T1: p <.01, T2: p <.05). In the N0 patients, difference in consistency between PN(+) and PN(-) was also significant (p <.01).

CONCLUSIONS

We suggest that quantitative evaluation of tumor consistency would be useful in determining whether selective neck dissections can safely be omitted in some patients.

67Ga whole-body scintigraphy in the evaluation of head and neck squamous cell carcinoma

The diagnostic accuracy of 67Ga-citrate whole-body scintigraphy for the evaluation of primary tumours, local recurrences, cervical node metastases and distant metastases was investigated in patients with head and neck squamous cell carcinoma (SCC). Altogether, 102 67Ga-citrate whole-body scans were performed on 83 patients with head and neck SCC using a dual-headed gamma camera. The results were compared with those of computed tomography (CT) and final diagnosis. 67Ga scintigraphy correctly diagnosed 28 of 29 primary lesions, a sensitivity of 97% (CT = 97%). For tumour recurrence, 67Ga scintigraphy correctly diagnosed 13 of 15 recurrences and 53 of 58 instances of no recurrence, giving a sensitivity of 87% and a specificity of 91% (CT = 80 and 62%, respectively). Scintigraphy correctly diagnosed 23 of 31 metastatic sides of the neck and all 173 negative sides of the neck, giving a sensitivity of 74% and a specificity of 100% (CT = 90 and 84%, respectively). Finally, scintigraphy correctly diagnosed all 12 distant metastases as well as 86 of 90 cases of no metastasis, resulting in a sensitivity of 100% and a specificity of 96%. Furthermore, in five patients, distant metastases were initially detected on 67Ga scintigraphy. In conclusion, 67Ga whole-body scintigraphy with a dual-headed camera resulted in a high sensitivity and specificity for the detection of primary lesions, recurrences and distant metastases of head and neck SCC. Although the sensitivity for detecting neck node metastases was relatively low, the specificity was high. Thus, 67Ga scintigraphy is an effective technique for the evaluation of head and neck SCC, especially tumour recurrence and distant metastases.

Wavelength-division multiplexing free-space optical interconnect networks for massively parallel processing systems

Wavelength-division multiplexing (WDM) techniques provide many advantages for building optical interconnect networks for massively parallel processing (MPP) systems. A design for a 1024-channel network for MPP systems based on the interconnection-cached network with vertical-cavity surface-emitting laser (VCSEL) arrays with one wavelength is described. We then show how a WDM version with four different wavelengths can increase the channel density. We also show how a WDM system can reduce the fan-in loss by a factor of 4. All the VCSEL's in each array are of the same wavelength, while different arrays use different wavelengths. We describe our experimental WDM subsystem containing four VCSEL arrays, operating at wavelengths of 843, 950, 970, and 980 nm, and three different WDM filters for multiplexing-demultiplexing. We present the operational results of the subsystem at 1 Gbit/s per channel.

Quantitative evaluation of consistency of normal mucosa, leukoplakia and squamous cell carcinoma of the tongue

The quantitative differences in consistency of normal mucosa, leukoplakia and squamous cell carcinoma of the tongue were studied. Forty-five patients with squamous cell carcinoma of the tongue, 26 with leukoplakia and 80 with normal tongues were examined using an instrument capable of measuring consistency as a function of the load (in grams) needed to displace tongue mucosa by 2.0 mm using a probe 2.0 mm in diameter. The mean value for consistency in tongue carcinoma, leukoplakia and normal tongue was 22.1 +/- 8.0 g, 8.3 +/- 2.0 g and 4.8 +/- 0.7 g, respectively. Differences in consistency among these entities were significant (P < 0.001). Furthermore, consistency in tongue carcinoma was significantly correlated to tumour thickness (r = 0.954, P < 0.001). It was concluded that the consistency in tongue lesions was objectively and quantitatively evaluated by this method, and this technique could measure the thickness of the tumorous lesions preoperatively.

Free-space optical bus using cascaded vertical-to-surface transmission electrophotonic devices

A free-space optical bus, which consists of cascaded optical switch devices, is proposed. The switch devices have multiple functions, such as data transmission, data detection, and data repetition. Basic interconnection characteristics were measured with vertical-to-surface transmission electrophotonic devices. Optical switching energy as low as 150 FJ and up to 4 MHz and a relatively high datatransmission rate, i.e., more than 20 MHz, were obtained. Connection cascadability and extendibility were confirmed.

Photorefractive effect in GaP

The photorefractive effect in undoped semi-insulating GaP was observed. GaP has a photorefractive sensitivity in the spectral region of 0.6 to 0.9 microm. The photorefractive center is the deep donor resulting from the P antisite defect. We measured the two-beam coupling gain coefficient and its time constant as functions of the grating period and the pumping intensity, using a 633-nm He-Ne laser. The maximum gain coefficient of 0.33 cm(-1) was obtained at a grating period of 1.1 microm. The time constant, which depends on the grating period, was 3-20 msec at a pumping intensity of 30 mW/cm(2).

Indicatrices of the earth's surface reflection from Landsat MSS data

A method of obtaining an indicatrix or a scattering diagram of the earth's surface is developed. When we regard the earth's surface as a kind of irregular surface, the indicatrix of scattered radiation is a way of effective representation of its surface roughness. The indicatrices of radiation over the sands of a seashore, a downtown area of Tokyo, and some of its suburban areas are obtained from Landsat MSS data. The radiant intensity decreases within the range of 32 degrees to 65 degrees of scattering angles in accordance with the degree of urbanization. Experimental results obtained by a remote sensing simulator are compared with those of Landsat MSS data analysis.

Measurement of spherical aberrations using a solid-state image sensor

An improved way of using the traditional Hartmann test has been evolved to measure spherical aberrations of photographic lenses. Instead of photographic plates, a solid-state linear image sensor was successfully used to achieve improvements in accuracy and in measuring efficiency. It was found possible to locate the intersection of a ray with the image plane in a few seconds, with an error of less than 0.3 microm. Two standard lenses of known data were measured to compare the results of the experiments and the calculations. The precision of the method is briefly discussed theoretically and experimentally.

An orthodontic study of temporomandibular joint disorders. Part 1: Epidemiological research in Japanese 6-18 year olds

Malocclusion is considered one of the etiological factors of temporomandibular joint disorder (TMD). The purpose of this study was to investigate the prevalence of TMD and the relationship between TMD and the type of occlusion. The sample consisted of 7337 Japanese children, 6-18 years old, 3219 boys and 4118 girls. TMD symptoms were recorded as well as the type of occlusion in children with TMD. The prevalence of TMD overall was 12.2%. The prevalence increased with age and was slightly higher in girls (13%) than in boys 11.1%. This difference was not statistically significant. Joint sound as the only symptom was more common in younger subjects. TMD symptoms seemed more complicated with age when pain and abnormal jaw movement combined with sound. Joint sound was the most common symptom (89.3%), followed by the combination of sound and pain (2.2%). The incidence of other symptoms was under 1%. In subjects with TMD, 24.9% exhibited crowding, 20.1% had excessive overjet, 6.8% deep bite, 6.3% edge-to-edge bite, 5.6% anterior crossbite, 5.4% open bite, and 3.8% posterior crossbite. Morphologically normal occlusion was observed in 27.1%. In this study, many subjects with TMD had malocclusions. Early treatment may be important in the prevention of severe TMD. Although those with morphologically normal occlusions were included, a more detailed study concerning other causes of TMD is needed also.