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Biomedical subjects

S K Chen

Publications and source records attributed to S K Chen.

At least 37 records · Page 2Linked to original sources
PubMed1998

Implementation of an oral and maxillofacial radiology image management and communication system.

OBJECTIVES: To implement an oral and maxillofacial radiology image management and communication system (OMFR IMACS) in the School of Dentistry, National Taiwan University. METHODS: An OMFR IMACS has been implemented over 3 years in three phases: (1) Establishment of an OMFR image processing laboratory for research and graduate student training; (2) Installation of network infrastructure and (3) Total system integration. RESULTS AND CONCLUSIONS: Intraoral, panoramic, cephalometric, and TMJ radiographs are directly processed with digital image acquisition devices or are converted into a digital format for viewing via UTP cable through FastEthernet in the eleven different divisions of the school. The system archives about 400 Mb of imaging data daily, representing 80% of the workload of the OMFR Division. The system is now used parallel to the conventional film-library system and has been integrated as part of the oral health service.

Humans↗
PubMed1997

Digitizing of radiographs with a roller-type CCD scanner.

OBJECTIVES: Roller-type scanners can be used to digitize radiographs. This study evaluated the physical performance of a roller-type scanner with regard to dynamic range, scan reproducibility, and homogeneity. METHODS: A VXR-12 (Vidar System Corp., Herndon, Va.) roller-type scanner with imaging editing software Paint Shop Pro (JASC Inc., Minnetonka, Minn.) was used to digitize a step tablet image on Kodak T-MAT G films (Kodak, Rochester, N.Y.). The step tablet image was scanned at various locations and with different scanning settings. The pixel values of the resulting image were analyzed. The step tablet image was also scanned by a Wellhofer WD 102 Filmdensitometer (Wellhofer Dosimetrie, Schwarzenbruck, Germany) to measure the optical densities of the steps on the film for comparison. RESULTS: With the use of the default scanning settings the digitized images had pixel values distributed in a similar dynamic range to that of the film densitometer. This scanner produced consistent images with different scanning positions, different orientation of the images, and different power states of the scanner. CONCLUSIONS: This roller-type scanner has a similar dynamic range to that of the film densitometer. The operating condition of the scanner is stable, and the resulting image is not significantly affected by the scanning positions. This type of scanner should be suitable for digitizing dental x-ray films, although the limiting scanning resolution might not be sufficient for some diagnostic purposes.

Absorptiometry, Photon↗
PubMed1997

Detection of small differences in mass using a direct digital dental X-ray system.

OBJECTIVES: To evaluate experimentally how in direct digital radiography heterogenous detector response may influence the depiction of small mass differences. METHODS: A step wedge of a bone-simulating resin was imaged at 70 kVp using RadioVisioGraphy ZHR 32000. Exposure time and step wedge position on the detector varied. The pixel values of the stored images of the step wedge were converted to luminance values of the displayed images. RESULTS: The relationship between pixel and luminance values was non-linear. The difference in luminance between adjacent steps varied with position of step wedge. Regardless of position, there was an increase in difference of luminance between steps with increasing exposure. A greater relative change in luminance was consequently seen in the thinner parts of the step wedge. The failure to perceive individual steps of the wedge in its thicker parts was related to insufficient relative change in luminance between steps. CONCLUSIONS: The heterogeneous response of the detector resulted in a varying ability to depict small mass changes over the detector area.

Evaluation Studies as Topic↗
PubMed1997

Surgical treatment of complete acromioclavicular separations.

A retrospective study of fifty-two patients (48 cases followed up), with Allman-Tossy grade III acromioclavicular separations, who were treated with coracoclavicular reconstruction by Mersilene prosthetic substitute (Mersilene tape with polyester suture, 5 mm wide, 30 cm, Ethicon), was carried out. The average follow up was 38 months, with the longest being 10 years, and the shortest being 8 months. The average age of the patients was 32 years, with a range from 20 to 62 years. Two groups were divided by age. Although the younger age group showed better results than the elder one in pain, range of motion and return to previous occupation or sports, the overall outcome was satisfactory in 41 of 48 (86%) followed patients. For the grade III acromioclavicular separation patients, surgical reconstruction with Mersilene looping provides a reliable result including use of the arm for sports or repetitive work.

Acromioclavicular Joint↗
PubMed1997

Salvage operation for neglected ankle fractures.

From 1986 to 1993, 49 cases of untreated or poorly treated ankle fractures who received salvage surgery were followed up for an average of 36.4 months. The patients included 31 males & 18 females with an average age of 41.6y/o and the time interval from initial injury to reconstructive surgery average due 17.6 months. They were classified and treated according to their grade of reduction and degree of arthrosis. The surgical methods included arthrotomy & joint debridement, revised open reduction, lower tibial osteotomy and ankle arthrodesis, depending on different individual conditions. After surgery, all cases had symptomatic relief and functional improvement with an average score increased from 26.3 preoperatively to 86.8 at follow up. The goals of ankle fractures is as articular fractures, they are treated by surgical anatomic reduction with rigid fixation as early as possible in order to provide good functional results. Nevertheless they are varied in neglected ankle fractures according to their individual conditions: open reductions were performed on cases with no or little arthritic change even though arthrosis might occur later because, if necessary, future conversion to osteotomy or arthrodesis would be easier. As for late cases with advanced arthritis, ankle arthrodesis were done by compressive arthrodesis with necessary bone graft to secure fusion in an optimal position.

Adolescent↗
PubMed1997

Subtalar arthrodesis for subtalar arthritis.

Primary subtalar arthritis is not common except in cases of generalized arthritis such as rheumatoid arthritis. The majority of subtalar arthritis results from intraarticular calcaneal fractures. Arthrodesis seems to be the only way to solve this problem. Thirteen patients (15 feet) were treated with subtalar arthrodesis at KMCH. Preoperative diagnosis included 13 feet with traumatic arthritis secondary to a calcaneal fracture, one foot with rheumatoid arthritis and one foot with primary osteoarthritis. The mean follow up period was 24.9 months. Lateral approach without fibular osteotomy was done with decompression if there was entrapment syndrome and the arthrodesis were accomplished with use of staples for internal fixation. Eleven (85%) of the patients were satisfied with the results. Objectively, the results were excellent after 11 arthrodesis (73%), good or fair after three (20%), and poor after one (7%). There was no nonunion. Complications occurred in 1 patient who developed superficial wound infection, and in 1 patient with staple loosening. Though there was no case of nonunion, the fusion time was rather long. This might have been due to the fixation method because staples can not provide compression force which accelerates union. We believe subtalar arthrodesis is appropriate for isolated subtalar arthritis unless there are associated talonavicular or calcaneocuboid arthritis in which case triple arthrodesis will be more appropriate.

Adult↗
PubMed1996

Detecting osteoporosis using dental radiographs: a comparison of four methods.

The authors evaluated dental radiographs for signs of osteoporosis using four methods: fractal dimension, microdensitometry, pixel intensity and panoramic analysis of cortical thickness. The efficacy of these methods also was compared against three standard bone density measurement techniques used to diagnose osteoporosis in bones other than the jaws: quantitative computed tomography and single- and dual-photon absorptiometry. Pixel intensity was significantly more effective than the other dental methods at distinguishing between radiographs from the osteoporotic group and the control group, although fractal dimension and microdensitometry methods also were effective.

Absorptiometry, Photon↗
PubMed1995

Digitizing of radiographs with a flatbed scanner.

OBJECTIVES: Flatbed scanners with the transparency scanning option can be used to digitize radiographs. The physical performance of this type of scanner was studied with regard to the digitizing of radiographs, including the dynamic range, the reproducibility and the homogeneity. METHODS: An Artix ArtiScan (Artix Technologies Inc., Milpitas, CA, USA) flatbed scanner with imaging editing software Aldus PhotoStyler (Aldus Corporation, Seattle, WA, USA) was used to digitize a stepped exposure image on Kodak T-MAT G films (Kodak, Rochester, NY, USA). The stepped exposure image was scanned at various locations and with different scanning settings. The pixel values of the resulting digital images were analysed. The stepped exposure image was also scanned by a laser densitometer to measure the optical densities of the steps on the film for comparison. RESULTS: Using the default scanning settings, the digitized images had pixel values distributed in a narrower range than that of the optical density values of the films. The range of the pixel values was widened by increasing the scanning time. Even then, the resulting pixel value profile was not identical to the optical density profile measured on film. The characteristic curve of this digitizing system was steeper than that of the film. Different pixel value distributions were obtained when the stepped exposure image was scanned at different positions on the scanning field, and when scans were obtained at different times. Reproducible results could be acquired when the images were scanned in the same area of the scanning field without changing the scanning settings and after the power had been on for a few minutes. CONCLUSIONS: In order to obtain digitized radiographs of any reliability from flatbed scanners, these should be carefully calibrated at the operating conditions.

Densitometry↗
PubMed1995

Linear unsharp mask filtering of linear cross-sectional tomograms of the posterior mandible.

Linear unsharp mask filtering is a digital image processing technique which can enhance diagnostic information by subtracting from the original image the linear blur which was formed in the direction of the linear tomographic movement. It was applied to linear cross-sectional tomograms of the posterior mandible aiming at retrieving cross-sectional outline information. This study demonstrated that the current Orthophos Program 16 with a 6.72 degrees tomographic angle does not provide accurate cross-sectional outline information of the posterior mandible. Linear unsharp mask filtering of these images also failed to provide more information. A larger tomographic angle of 10 degrees was employed with the Polytome to simulate the modified Program 16 with a wider beam. The resulting tomographic images showed better defined cross-sectional outlines, and after the linear unsharp mask filtering, the outlines were more readily retrieved. In order to get cross-sectional outline information of the posterior mandible, the tomographic angle of the Orthophos program 16 should be increased to more than 10 degrees which can be achieved by increasing the width of the x-ray beam.

Aged↗
PubMed1994

Frequency domain analysis of cross-sectional images of the posterior mandible.

The Siemens Orthophos (Siemens, München, Germany) is a panoramic machine that uses a microchip to control the movements of the radiation source and film. Several programs are available for different views of the facial skeleton and associated structures. Program 16 is dedicated to cross-sectional imaging of the posterior mandible. Three millimeter cross-sections were cut from 12 cadaver specimens of the mandible. These sections were imaged separately by contact radiography, 48 degrees hypocycloidal tomography of Philips Polytome (Philips-Massiot, Paris, France), and program 16 of the Orthophos panoramic machine. Program 16 of the Orthophos was also used to image the cross-sections after they were glued back together with the surrounding parts of the specimens. Four different images of the cross-sections were thus obtained. The contact radiographs were used as gold standards. Frequency domain analysis, which was used to compare the images resulting from each imaging modality, demonstrated that useful diagnostic information was in the range of 0.12 to 0.60 cycles/mm for the contact radiographs. In spite of differing tomographic angles for the Orthophos program 16 and the hypocycloidal tomography, the images of the 3 mm cross-sections showed similar frequency distribution. However, the Orthophos Program 16 did not produce diagnostically useful images when the cross-sections were imaged with the surrounding parts of the specimens probably because of the narrow tomographic angle used for this program. These images had strong low to medium frequency components compared with the gold standard images. These results suggest that diagnostically more useful images with the Orthophos might be obtained by increasing the tomographic angle.

Aged↗
PubMed1994

Modulation transfer function of a digital dental x-ray system.

An impulse train method to control aliasing was used to measure the modulation transfer function of a digital dental x-ray system (RVG 32000 ZHR, Trophy Radiologie, Vincennes, France). The detector of this system is composed of an intensifying screen, a fiber optics taper, and a charged couple device chip. The modulation transfer function could not be measured by impulse method such as the line spread function or edge response function because of aliasing from undersampling of the digital system. The system modulation transfer function was difficult to recover at the spatial frequencies smaller than the Nyquist frequency. The modulation transfer function beyond the Nyquist frequencies was impossible to recover in this study.

Fourier Analysis↗
PubMed1994

Evaluation of single-use masks and respirators for protection of health care workers against mycobacterial aerosols.

BACKGROUND: The recent increase in multidrug-resistant tuberculosis has spawned a major controversy concerning the degree of respiratory protection needed by health care workers, particularly during sputum-inducing procedures. The objective of this study was to measure the filtration efficiencies of a single-use submicron surgical mask, two disposable dust/mist respirators, a dust/mist/fume respirator, and a high-efficiency particulate air respirator against aerosolized mycobacteria. Facial fit was not addressed. METHODS: In a specially designed enclosed test apparatus, an aerosol was generated with a Collison nebulizer from a known concentration of Mycobacteria chelonae, used as a surrogate for Mycobacterium tuberculosis. Aerosol concentrations were measured with Anderson samplers upstream and downstream of the test masks and respirators, which were heat sealed to a metal plate. RESULTS: Mean efficiencies ranged from approximately 97% for the surgical mask and a dust/mist respirator to more than 99.99% for the high-efficiency particulate air respirator. Measurements of filter efficiency with an Aerodynamic Particle Sizer for the M. chelonae aerosol and independent challenge tests with latex spheres correlated closely with measurements of M. Chelonae collection efficiency determined with Andersen samplers. CONCLUSIONS: Analysis of variance and Tukey's method for multiple comparisons indicated that the dust/mist/fume respirator and the HEPA respirator collected M. chelonae with significantly greater efficiency than did either the surgical mask or the dust/mist respirator. Even the least efficient mask tested, however, had a filter efficiency of more than 97% against particles averaging less than 1 micron in aerodynamic diameter.

Aerosols↗
PubMed1993

Detector response and exposure control of the RadioVisioGraphy system (RVG 32000 ZHR).

The RadioVisioGraphy system (RVG 32000 ZHR) was studied with respect to some physical properties including the precision and linearity of the exposure control and the detector response to x-rays. The x-ray unit was found to yield repetitive exposures that are precisely controlled by the CCX timer. A "preheat" and an "after exposure" period were noticed, and their resulting x-ray exposures were measured. Two RVG detectors were compared for their responses with x-rays. The differences between the detectors were insignificant. However, inhomogeneous detector responses were found in both of the detectors; with the same exposure, the central parts of the detectors yielded lower pixel values than the peripheral parts. A calibration equation was developed to correct for the inhomogeneity.

Radiation Dosage↗
PubMed1993

Paragonimus calcified ova mimicking left renal staghorn stone.

We report on a 49-year-old woman with clusters of Paragonimus calcified ova unusually located in the left retroperitoneal space and renal capsule mimicking a left renal staghorn stone. The diagnosis and treatment are discussed. We also reviewed the endemic condition of paragonimiasis in Taiwan.

Animals↗
PubMed1992

Image resolution in the midsagittal plane of the Orthopantomograph-10 using Lanex regular and T-Mat G screen-film combination.

Image resolution was measured in the midsagittal plane of the Orthopantomograph-10 with the use of Lanex regular and T-Mat G screen-film combination. A thin platinum edge phantom was used to obtain images for calculation of the edge response functions. Subsequently, line spread functions and modulation transfer functions of the system were calculated. Noise equivalent passband values, which were expressed in line pairs per millimeter, were derived to describe the image resolution. The noise equivalent passband values derived in this study were generally smaller than those reported in a previous study. The width of the image layer was found to be uniform at different vertical levels.

Humans↗
PubMed1992

Behavioural problems among preschool age children in Shanghai: analysis of 3,000 cases.

This paper reports the preliminary findings of an epidemiological study of 3,000 children ages four and five in the Shanghai area. Associations were investigated between problems in the narrow band syndromes of the Achenbach Child Behavior Checklist and certain sociodemographic variables (a one-child family, other social circumstances related to the family). No strong evidence emerged of a distinct psychopathology associated with children from single-child families, although there was a significant correlation between being an only child and having social withdrawal problems. Delinquent behaviour and hyperactivity were more frequent among boys, while somatic complaints, schizoid or anxious, and depression were more frequent among girls. A four year follow-up study of 433 children from the original group who continued to have problems showed a marked increase in hyperactive syndrome problems; this suggests the existence of a clinically identifiable group of behaviourally disturbed children. Early identification allows for early treatment and comparison of the relative efficacy of early and late treatment approaches.

Child Behavior Disorders↗
PubMed1991

[Repair method and healing of skeletal muscle injury].

This study used m.anterior tibialis of rabbits to document recovery after laceration and repair after a healing period of 12 weeks. Postoperation care were divided into three groups: cast immobilization one or four weeks, and free activity. There were three different methods used to repair muscles including simple suture with Dexon 2-0, modified Kessler with 1/4 width of mersiline 5-0 and simple suture with tendon graft. Physiologic recovery including tension force and muscle contracture length had been tested. Histologic recovery including H & E and ATPase stains had been examined. The recovery of tension force was influenced by immobilization time, not by suture method. The best recovery of tension force was resulted from postoperation care with free activity. The result of shortening length of muscle was according to different suture methods and had no relation with immobilization time. Modified Kessler suture resulted in the best muscle contracture length. The method of modified Kessler suture without immobilization was recommended for management of lacerated muscle.

Animals↗