Biomedical subjects

K Kuroyanagi

Publications and source records attributed to K Kuroyanagi.

At least 37 records · Page 2Linked to original sources

PubMed1997

Evaluation of XD/A Plus and ST8G films for cephalometric radiography with Grenex G8 and BH-III screens.

OBJECTIVES: Sensitometric properties, clinical image quality, and patient dose requirements are important considerations when selecting film for cephalometrics. Two recently released films, XD/A Plus and ST 8G green sensitive films, were studied. METHODS: The films were each combined with Grenex G8 (Fuji Medical) green-fluorescing matched and BH-III (Kasei Optonix) blue-fluorescing mismatched intensifying screens. The density response and resolution for each screen-film combination were evaluated by use of the characteristic curve and modulation transfer function. The kilovoltage settings providing clinically acceptable images were assessed individually by 12 observers. Clinically acceptable images for each combination were also compared, and the skin entrance doses in the temporomandibular joint region were determined. RESULTS: The average contrast at the most effective density range was found to be slightly higher for the BH-III group than for the G8 group. The modulation transfer function for the BH-III group was inferior to that for the G8 screens. There were no significant differences in diagnostically acceptable image quality among the four combinations; nevertheless the BH-III screen group required two to three times more exposure than the G8 screen group. CONCLUSIONS: XD/A Plus and ST8G films provide acceptable image detail for cephalometrics. To minimize the patient dose they should be used with green-emitting screens.

Analysis of Variance↗

PubMed1997

Sensitometric effects of varying the intensifying screens used with Agfa Dentus ST8G and RP6 panoramic radiographic films.

OBJECTIVES: To compare the sensitometric effects and information yield of varying the intensifying screens used with both Dentus ST8G and RP6 Agfa Gevaert, Dormagen, Germany panoramic radiographic films. MATERIAL AND METHODS: Four screen-film combinations were employed for each of the two film types. The screens used were blue fluorescing PX-III (Kasei Optonix, Tokyo, Japan) and Special (Siemens AG, Bensheim, Germany), as well as green fluorescing Lanex Regular (Eastman Kodak, Rochester, NY, USA) and Trimax T16 (3M, Mineapolis, Minnesota, USA). The density response for each screen-film combination was evaluated using the characteristic curves generated. Information yield, as determined by the radiographic detection of defects in an aluminium test object, was evaluated by nine observers. RESULTS: The characteristic curves for ST8G were different when green and blue fluorescing screens were used; however, those for RP6 varied little irrespective of the choice of intensifying screens. Observers were able to perceive defects at significantly lower radiation exposures for ST8G combined with green fluorescing screens compared with blue emitting screens. RP6 with all screen combinations provided similar image detail perceptibility at comparable exposures with ST8G with green-fluorescing screens. CONCLUSIONS: RP6 is suitable for use with either the spectrally matched blue emitting screens or green-emitting screens. ST8G radiographic film should always be matched to rare earth screens.

Analysis of Variance↗

PubMed1997

Radiation dosage reduction in general dental practice using digital intraoral radiographic systems.

This report describes the radiation dosage reduction possible in the general dental practice with two CCD (charge-coupled device)-based intraoral radiographic systems: the RVG-S (Trophy Radiologie, Vincennes, France) and the Sens-A-Ray (Regam Medical Systems, Sundsvall, Sweden). Radiation dosages (air-kerma; Gy) necessary for obtaining clinically acceptable images were measured at the cone tip using an ionization chamber type 660-1 (Nuclear Associates, Victoreen, Inc., Carle Place, New York, USA). When the RVG-S was used with an Oramatic 70 (Trophy Radiologie) X-ray generator, dosages at the cone tip ranged from 322 to 612 microGy. These corresponded to 40-60% of the dosages necessary when using Ektaspeed dental X-ray film (Eastman Kodak, Rochester, New York, USA) with a Heliodent 70 (Siemens, Erlangen, Germany) X-ray generator. At 60 kVp, the Sens-A-Ray reduced the dosage in the order of 30% compared with Ektaspeed dental X-ray film. Reduction in radiation dosage is one of the benefits of digital intraoral radiographic systems in general dental clinics. The RVG-S provides greater dose savings than does the Sens-A-Ray.

Evaluation Studies as Topic↗

PubMed1996

Optimum exposure ranges for computed dental radiography.

OBJECTIVE: Computed dental radiography (CDR; Schick Technologies Inc, Lond Island City, NY, USA) can be used with any dental X-ray generator. The optimum exposure at various tube voltage settings was studied. METHODS: Images were made of a dental QA jaw phantom and a standard aluminium stepwedge. Exposures were made between 50 and 90 kVp at 10 kVp intervals. Two contrast indices were calculated from the bone stepwedge pixel values: CI(1), the ratio between the highest and lowest pixel values, and CI(2), the difference between them. RESULTS: Contrast indices were greatest at low kVp. The gradual decrease in CI(1) with increased exposure demonstrated that the optimum exposure range was always relatively wide. Maximum CI(2) values were found at exposures of 27, 17, 15, 11 and 9microC kg-1 at 50, 60, 70, 80 and 90 kVp, respectively, at the centre of the optimum exposure range. Pixel values for each aluminium step increased both with increased exposure and with increased kVp. The longest contrast scale was obtained at 11.0, 9.6, 8.7, 7.2 and 7.0 microC kg-1 at 50, 60, 70, 80 and 90 kVp. The steepest slopes were obtained either with thin aluminium steps or at low kVp. CONCLUSIONS: CDR is a fast CCD-based system and is capable of operating at a wide range of kVp settings.

Aluminum↗

PubMed1996

Technical report. Processing to achieve high-contrast images with computed dental radiography.

OBJECTIVES: To determine the effects of equalization on image contrast and signal-to-noise ratio (SNR) with Computed Dental Radiography (CDR). METHODS: Pixel value distributions were measured for various tissue thicknesses of a dental quality assurance jaw phantom and the average pixel values and SNR calculated. RESULTS: Equalization resulted in enhanced image contrast of underexposed images by effecting pixel value adjustment with little change in SNR. Overexposed images demonstrated minimal difference in contrast or SNR when equalization was applied. CONCLUSION: The equalize function of CDR is a convenient method to provide high-contrast images from underexposed images without detriment to the SNR. As it does not compensate for overexposure, the function will not lead to inappropriate overdosage of the patient.

Humans↗

PubMed1996

Technical note. Modulation transfer function analysis of a newly revised rotational panoramic machine.

OBJECTIVES: To determine the modulation transfer function (MTF) and noise equivalent passband (NE) values for a newly revised rotational panoramic X-ray machine, the PC-1000 (Panoramic Corp., Fort Wayne, Indiana, USA). METHODS: Images of a 10 microns test slit were taken at various locations along the X-ray beam projection path using a Lanex Regular/T-Mat G image receptor. Line spread functions were obtained at specific beam paths by scanning slit images with a microdensitometer. RESULTS: MTF values were highest around the central plane of the image layer, with a maximum near the centre of 0.25 at 4 cycles/mm. The NE values near the central plane of image layer were 1.4 cycles/mm. MTF and NE values in the anterior region were low, 0.2 and 1.2, respectively. The width of the image layer was narrower in the anterior and wider in the posterior segments. Rapid decreases in MTF and NE values were found on the X-ray tube side compared with the receptor side of the central plane. Using a spatial frequency of 0.25 MTF the shape of the image layer was coincident with that determined visually. CONCLUSION: On the basis of the MTF and NE values the image resolution produced by this machine is considered acceptable for panoramic dental radiography.

Mathematics↗

PubMed1996

Low-cost teleradiology for dentistry.

The performance of a low-cost teleradiology system was studied. The time needed for radiographic transmission between computers and the image integrity following transmission were measured. The image resolution was analyzed with a line-pair test chart. Images were transmitted through computers that had a video-processing board and a modem at both the transmission and receiving sites. Intraoral radiographs were captured with a black and white charge-coupled device camera. The time required for image transmission was less than 1 minute (46 to 56 seconds), an effective transmission speed of 1.73 kbyte/s (13.9 kbit/s). No changes were observed in pixel value distributions; hence, there was no loss of image detail. The maximal resolution of the system was 4 line-pairs/mm. The performance of the teleradiology system demonstrated its potential as an effective, low-cost telenetwork for dentistry.

Diagnosis, Computer-Assisted↗

PubMed1995

Sens-A-Ray characteristics with variations in beam quality.

This study examined the relationship between x-ray beam quality and image characteristics with the use of the Sens-A-Ray (Regam Medical Systems, Sundsvall, Sweden). To evaluate the x-ray response, properties of the image sensor, dark current and statistical noise, sensitivity, and contrast resolution were measured. Tube voltage, tube current, and exposure time were varied. Exposures were determined with the use of an ionization chamber. Pixel values beneath a lead strip were used to calculate dark current effects. Contrast was measured with pixel values from the images of a step-wedge. Dark current noise increased in proportion to exposure time. Although the sensitivity at each tube voltage was linear and proportional to the exposure, the gradient was inversely proportional to increased tube voltage. After subtraction of the dark current and statistical noise, the gradient of the sensitivity at low tube voltage remained steeper than at high tube voltages. Hence, sensitivity decreased with increased tube voltage. Sensitivity gradients at each different tube current were similar. Irrespective of exposure, contrast resolution between adjoining step-wedge steps > or = 9 mm were too small to distinguish at 50 kVp. The gray levels for each step below 12 mm in thickness were distinguishable with 90 kVp. Increased dark current noise consequent to long exposure times narrowed the available gray scale range. Lower tube voltage resulted in higher sensitivity with larger gradients than higher tube voltages.

Analog-Digital Conversion↗

PubMed1995

A dual sensitivity screen system for TMJ image enhancement in cephalometric radiography: sensitometric evaluation.

OBJECTIVES: An in vitro evaluation of the image quality of the TMJ OrthoCeph Slimline Cassette System (TOSCS). METHODS: The density response, resolution and clarity of the system were evaluated by use of the characteristic curve, modulation transfer function and root mean square quantum mottle. Relative sharpness was evaluated qualitatively by five observers. RESULTS: Increased density with Trimax 12 gave almost the same contrast as that with Trimax 8 in the diagnostic range, whereas MTF and RMS for Trimax 12 were inferior. CONCLUSIONS: The dual-sensitivity screen system should lead to improved radiographic contrast of the TMJ region in cephalometric radiography. The reduction in sharpness is probably clinically insignificant.

Absorptiometry, Photon↗

PubMed1995

Perceptibility of defects in an aluminum test object: a comparison of the RVG-S and first generation VIXA systems with and without added niobium filtration.

OBJECTIVE: To compare the first generation VIXA (Gendex, Milan, Italy) and the RVG-S (Trophy Radiologie, Vincennes, France) for detection of defects in an aluminium test object at various exposures both with and without added niobium filtration. METHODS: Images of a 7 mm aluminium test object with defects ranging from 0.1 to 1.5 mm with standardized projection geometry. Seven dentists acted as observers. Perceptibility curves were developed for both sensors under the various filtration conditions and exposures. RESULTS: At optimum exposures both the VIXA and the RVG-S permitted the same number of defects to be observed. The optimum exposures were similar for the two systems, but the dynamic range was greater for the RVG-S. Addition of niobium filtration did not appreciably alter the radiation dose required to perceive a given number of defects using either system. CONCLUSIONS: The two systems performed equally at optimum exposure when the dose is approximately the same irrespective of the presence or absence of niobium filtration. Beyond the optimal level, the RVG-S outperformed the VIXA system.

Aluminum↗

PubMed1995

Comparing the sensitometric properties of dental X-ray films.

This article describes a study that compared the sensitometric properties and information yields of four dental X-ray films: Eastman Kodak Ultra-Speed DF-57 and Ektaspeed EP-21, Flow DV-58 and Agfa Gevaert Dentus M2 Comfort. Dentus M2 Comfort gave the greatest contrast, a speed between the conventional D- and E-speed film groups and an exposure latitude wider than Ultra-Speed but less than DV-58. A significant difference in detail was found with low exposures, Dentus M2 Comfort and Ektaspeed outperforming the other two film types.

Absorptiometry, Photon↗

PubMed1995

Observer performance in the assessment of contract enhanced CT: effects of contrast medium and grey scale window on detection of defects in a simulated peripheral rim border.

The image contrast of X-ray CT systems depends on the properties of the imaging system, the number of grey scales used in the digital sampling process, and the addition or otherwise of a contrast medium. The effect of contrast medium is often emphasized in the peripheral rim of pathologic masses. In this study, a special hexagonal test object made of acrylic phosphate and a cylindrical container were employed. When the contrast medium IOPAMIRON 300 was used to fill the space between the test object and its cylindrical container, a contrast-enhanced peripheral rim with or without signal of defect was observed. Visual perceptibility was examined from the signals resulting from varying contrast by use of contrast medium and adjusting the grey scale by image processing. Threshold contrast influenced by window width was recorded in each image contrast, different ranges of window width was recorded in each instance using statistical analyses. While window width was inversely proportional to image contrast, different ranges of window width and image contrast provided better visual perceptibility for each concentration of the contrast medium. The range of window width for obtaining the best visual perceptibility was determined for a contrast-enhanced image.

Absorptiometry, Photon↗

PubMed1995

Objective and subjective assessments of Kodak Ektaspeed plus new dental X-ray film: a comparison with other conventional X-ray films.

A new dental X-ray film called EKTASPEED Plus has been released by the Eastman Kodak Company. Its sensitometric properties, inclusive of modulation transfer function (MTF) and Wiener spectrum (WS) and the visibility of radiographic details, were compared with those of other conventional dental X-ray films, EKTASPEED EP-22 (Eastman Kodak Co.) and Ultra-Speed DF-57 (Eastman Kodak Co.). The base plus fog density of EKTASPEED Plus was between those for EKTASPEED and Ultra-Speed. Relative speed of EKTASPEED Plus was slightly faster than EKTASPEED, and about two times faster than that of Ultra-Speed. The contrast of EKTASPEED plus was close to that of Ultra-Speed. Only minor differences existed between the film types studied when the sharpness and the granularity were compared. The MTF and WS also revealed no substantial differences between the films. Perceptibility testing showed minor differences between the three films, with EKTASPEED Plus consistently revealing more defects at lower exposures irrespective of whether a Burger's phantom or aluminum test block was used.

Evaluation Studies as Topic↗

PubMed1994

[Toxicity studies of paclitaxel. (I)--Single dose intravenous toxicity in rats].

Paclitaxel, an antineoplastic agent, was given to Crj: CD (SD) rats of both sexes at 38, 50, 65 and 85 mg/kg by single intravenous administration to investigate its acute toxicity. The results obtained are summarized as follows: 1. Tachypnea and decreased activity with prone position were noted for vehicle and all paclitaxel groups, and alopecia for all paclitaxel groups. 2. Deaths occurred for one out of 5 males and 2 out of 5 females at 85 mg/kg. One female died of respiratory insufficiency induced by vehicle on Day 0. One female and one male died of the systemic toxicity of paclitaxel such as hypoplasia of the bone marrow and lymphoid depletion of lymphatic organs on Days 6 and 12, respectively. 3. On Days 4 and 5, all paclitaxel groups showed decreases of reticulocyte and white blood cell counts, as well as decrease of differential count of neutrophils. These changes were generally recovered by a week after dosing. 4. Histopathological examinations revealed atrophy of the thymic medulla, hypoplasia of the bone marrow and lymphoid depletion of the spleen for a few males at 85 mg/kg, and hypospermatogenesis and tubular atrophy of the testes for all paclitaxel groups. Based on these results, 85 mg/kg of paclitaxel was lethal to rats, and hematopoietic, lymphoid and male reproductive systems were primarily affected under this condition.

Alopecia↗

PubMed1994

[Toxicity studies of paclitaxel. (II)--One-month intermittent intravenous toxicity in rats].

Paclitaxel, an antineoplastic agent, was intravenously given to Crj:CD (SD) rats of both sexes at 0 (saline), 0 (vehicle), 1.0 (low dose), 3.3 (intermediate dose) and 10.0 (high dose) mg/kg at five-day interval over one-month period (6 times in total) to investigate its repeated dose toxicity and the reversibility of toxic effects. The results obtained are summarized as follows: 1. Decreased activity with prone position was observed for high dose and vehicle groups, and alopecia was seen for many high dose rats. Body weight gain and food intake were suppressed for high and intermediate dose groups. No deaths occurred. 2. Red blood cell count, hemoglobin, hematocrit, white blood cell count, relative neutrophil count, platelet count and reticulocyte count were decreased for high dose groups. Red blood cells count was also decreased for intermediate dose groups. 3. Thymic atrophy, splenic hematopoiesis, bone marrow hypoplasia, testicular atrophy with suppression of spermatogenesis and tubular atrophy, and epididymal atrophy were observed for high dose rats. 4. Above-described changes excluding the findings on the testis and epididymis for high dose rats were shown to be generally reversible. Based on these results, the no-toxic effect dose of paclitaxel was estimated to be 1.0 mg/kg in rats under this study condition.

Alopecia↗

PubMed1994

[Toxicity studies of paclitaxel. (III)--Six-month intermittent intravenous toxicity in rats].

Paclitaxel, an antineoplastic agent, was intravenously given to Crj:CD (SD) rats of both sexes at 0 (saline), 0 (vehicle), 0.3 (low dose), 1.0 (intermediate dose) and 3.3 (high dose) mg/kg at seven-day interval over a six-month period (total of 27 doses) to investigate its repeated dose toxicity. The results obtained are summarized as follows: 1. No deaths occurred in this study. Vehicle-related salivation was seen for some high dose and vehicle control rats. Soiling of the perigenital region was observed for some high dose females. 2. Red blood cell count, hemoglobin, hematocrit and white blood cell count were decreased for high dose rats. Reticulocyte count was increased and relative neutrophil count was decreased for high dose males. 3. Relative erythroid and myeloid cell count were decreased for high dose rats in bone marrow smear examinations. 4. Bone marrow hypoplasia and splenic hemosiderosis were observed for high dose rats, and thymic atrophy and lymphoid depletion were seen for some high dose males. Based on the these results, the no-toxic effect dose of paclitaxel was estimated to be 1.0 mg/kg in rats under this study condition.

Animals↗

PubMed1994

[Reproductive and developmental toxicity studies of paclitaxel. (I)--Intravenous administration to rats prior to and in the early stages of pregnancy].

Paclitaxel, an antineoplastic agent, was administered intravenously to Crj: CD (SD) rats daily at dose levels of 0 (saline and vehicle), 0.1, 0.3 and 1.0 mg/kg for 63 days prior to mating and during the mating period in males, and for 14 days prior to mating and during the mating period as well as day 0 to day 7 of gestation in females. Results were as follows: 1. Body weight gains were shown a tendency to hasten in vehicle-treated male rats associated with the increased food consumption. However, the vehicle-treated group had no effect in the other parameters that were measured in this study when compared to the saline-treated group. 2. 1.0 mg/kg paclitaxel caused suppression of the body weight gains accompanied by the decreased food consumption in either male or female rats. 3. Adrenal and ovarian weights were decreased in 1.0 mg/kg dams at term. 4. The fertility indices in both sexes of 1.0 mg/kg were lower than the saline-treated group. However, the copulation indices in both sexes in 1.0 mg/kg rats were comparable to those of the saline-treated group. 5. Decreases in the number of corpora lutea, implantations and live fetuses or increases in the number of empty implantation sites and total embryo-fetal deaths were observed in 1.0 mg/kg dams. However, the fetal weights, crown-rump distances and tail lengths in live fetuses were not affected by paclitaxel treatment. Based on the reproductive and developmental indices, the no toxic-effect dose level of paclitaxel is 0.3 mg/kg/day for parent animals and their fetuses.

Adrenal Glands↗

PubMed1994

[Reproductive and developmental toxicity studies of paclitaxel. (II)--Intravenous administration to rats during the fetal organogenesis].

Paclitaxel, an antineoplastic agent, was administered intravenously to pregnant Crj: CD (SD) rats daily at dose levels of 0 (saline and vehicle), 0.15, 0.3 and 0.6 mg/kg from day 7 to day 17 of gestation. Results were as follows: 1. The ossification of hyoid bodies was retarded in F1 fetuses by the vehicle. However, the vehicle-treated group had no effect in the other parameters that were measured in this study when compared to the saline-treated group. 2. Body weight gains and food consumption in F0 dams were not affected by paclitaxel during the gestation and lactation periods. 3. Paclitaxel failed to affect the organ weights in F0 dams. 4. Paclitaxel did not alter the prenatal development in F1 fetuses. 5. External, internal and skeletal malformations were not induced by paclitaxel. Further, paclitaxel did not affect the skeletal variations and ossification processes. 6. Paclitaxel did not alter the delivery status of F0 dams or viability and weaning indices in F1 pups. 7. The day required for presence of hair was significantly delayed in 0.6 mg/kg F1 pups at paclitaxel. However, the days required for pinnae detachment, incisor eruption, eye opening, testicular descent and vaginal opening were not affected by paclitaxel. 8. No effects on body weight gains or food consumption were observed in both male and female F1 rats. 9. Paclitaxel did not alter the developmental behavior, learning ability and memory, spontaneous motor activity or emotionality in F1 rats. 10. The reproductive performance in both male and female F1 rats were not affected by paclitaxel. 11. Paclitaxel did not alter the organ weights in both male and female F1 rats. 12. No influence on prenatal development was observed for F2 fetuses even at the highest dose level of paclitaxel. Based on the reproductive and developmental indices, the no toxic-effect dose level of paclitaxel is 0.6 mg/kg/day and 0.3 mg/kg/day for dams (F0) and their offspring (F1), respectively.

Animals↗