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Biomedical subjects

J C Cheng

Publications and source records attributed to J C Cheng.

At least 55 records · Page 3Linked to original sources
PubMed1999

Medical data mining using evolutionary computation.

In this paper, we introduce a system for discovering medical knowledge by learning Bayesian networks and rules. Evolutionary computation is used as the search algorithm. The Bayesian networks can provide an overall structure of the relationships among the attributes. The rules can capture detailed and interesting patterns in the database. The system is applied to real-life medical databases for limb fracture and scoliosis. The knowledge discovered provides insights to and allows better understanding of these two medical domains.

Algorithms↗
PubMed1999

Bone mineralization at the callotasis site after completion of lengthening.

We studied the course of bone mineralization of regenerate bone after callotasis lengthening. Twenty-three patients (eight boys) (mean age at operation 11.5 years, range 4-17 years; leg length discrepancy [LLD] at surgery ranging from 4 to 13 cm) underwent dual-energy X-ray absorptiometry (DEXA) scanning weekly during the distraction phase, at 2 week intervals until removal of the fixator, and at the time of their out-patient visits thereafter, for a mean of 794 +/- 420 days after removal of the apparatus. At removal of the fixator, the bone mineral content (BMC) of the regenerate was nearly 70% of the normal contralateral limb. With time, this value gradually increased, and tended to reach normal values, with no significant difference between femur and tibia. With time, the BMC of the regenerate tends to return to the value of the normal contralateral limb. Probably, once the limb length discrepancy has been equalized, the mechanical stimuli imparted through weight-bearing to the lengthened limb are of the same magnitude bilaterally. In this instance, then, the newly formed bone, responding to these physical stimuli, would normalize its mineral content, confirming that bone remodeling continues well after lengthening is terminated. Mineralization of the regenerate after completion of the lengthening process reaches values significantly greater than at removal of the fixator, with an increase of >50% of the prelengthening values, regardless of the underlying pathology. The final value of this increased BMC is not significantly different than in the normal contralateral unoperated limb. At least part of the increase in bone mineralization following callotasis lengthening is due to the normal process of growth and development.

Absorptiometry, Photon↗
PubMed1999

A pilot study of three-dimensional conformal radiotherapy in unresectable hepatocellular carcinoma.

BACKGROUND: The purpose of this study was to determine the potential role of three-dimensional (3-D) conformal radiotherapy (RT) in treatment of unresectable hepatocellular carcinoma (HCC). METHODS: Thirteen patients were included in this study, which was conducted between 1993 and 1996. Nine patients (group A) were treated with 3-D conformal RT alone because of main portal vein thrombosis, inferior vena cava thrombosis, obstructive jaundice and failure of previous transcatheter arterial chemoembolization (TACE) to control the disease. The remaining four patients (group B) were treated with a combination of TACE and 3-D conformal RT. RESULTS: The greatest dimension of the main tumour in the whole group of patients ranged from 6 to 25 cm (median 15 cm). The radiation dose ranged from 40 to 60 Gy. The tumour response was evaluated by computed tomography scans of the liver 6-8 weeks after completion of radiotherapy. Partial response was observed in 58% of the patients (seven of 12) and minimal response in another 25% of patients (three of 12). One patient could not be evaluated because of the development of hepatic failure 1 month after completion of RT. All patients in group B lived for more than 1 year (range 16-40 months). In group A, one patient who had a large tumour (11 x 10 x 21 cm) with portal vein thrombosis was converted to become resectable after 45 Gy of radiation. The resection specimen revealed no residual cancer cells. This patient is alive longer than 15 months after treatment without the evidence of disease. CONCLUSIONS: Our experience indicates that HCC is more radiosensitive than it was traditionally expected. Three-dimensional reconstruction of tumour and surrounding organs helps to avoid excessive exposure of the liver and adjacent organs to RT and makes it a safer treatment modality for unresectable HCC. Our preliminary data show promise and are worthy of further study to explore the potential role of radiotherapy in the treatment strategy for HCC at various stages of involvement.

Aged↗
PubMed1999

Incidence of complicated healing and osteoradionecrosis following tooth extraction in patients receiving radiotherapy for treatment of nasopharyngeal carcinoma.

A group of 43 patients requiring tooth extraction after radiotherapy for nasopharyngeal carcinoma (NPC) was studied retrospectively to determine the incidence of post-extraction complications. It was found that because of the method used in the delivery of radiation, extraction of maxillary posterior teeth resulted in the greatest risk of complications (28.9 per cent), including a 10.5 per cent risk of osteoradionecrosis (ORN). Based on the findings, a protocol was established for the dental care of such patients. It was concluded that when extraction of maxillary posterior teeth was necessary, prophylactic antibiotics were not sufficient to prevent the complication of delayed healing. The risk of ORN was 10.5 per cent within the field of maximal radiation dose. Hyperbaric oxygen may be the better choice of preventive measures. However, in view of the low risk of ORN, wholesale prescription of hyperbaric oxygen therapy may not be indicated. An additional patient who had tooth extraction two weeks prior to radiotherapy was included to show that if adequate time for wound healing was not allowed, ORN could develop.

Adult↗
PubMed1999

Specific interaction between the hepatitis C virus NS5B RNA polymerase and the 3' end of the viral RNA.

Hepatitis C virus (HCV) NS5B protein is the viral RNA-dependent RNA polymerase capable of directing RNA synthesis. In this study, an electrophoretic mobility shift assay demonstrated the interaction between a partially purified recombinant NS5B protein and a 3' viral genomic RNA with or without the conserved 98-nucleotide tail. The NS5B-RNA complexes were specifically competed away by the unlabeled homologous RNA but not by the viral 5' noncoding region and very poorly by the 3' conserved 98-nucleotide tail. A 3' coding region with conserved stem-loop structures rather than the 3' noncoding region of the HCV genome is critical for the specific binding of NS5B. Nevertheless, no direct interaction between the 3' coding region and the HCV NS5A protein was detected. Furthermore, two independent RNA-binding domains (RBDs) of NS5B were identified, RBD1, from amino acid residues 83 to 194, and RBD2, from residues 196 to 298. Interestingly, the conserved motifs of RNA-dependent RNA polymerase for putative RNA binding (220-DxxxxD-225) and template/primer position (282-S/TGxxxTxxxNS/T-292) are present in the RBD2. Nevertheless, the RNA-binding activity of RBD2 was abolished when it was linked to the carboxy-terminal half of the NS5B. These results provide some clues to understanding the initiation of HCV replication.

Amino Acid Sequence↗
PubMed1999

A new alignment jig for quantification and prescription of three-dimensional alignment for the patellar-tendon-bearing trans-tibial prosthesis.

Clinically, it is hard to achieve and reproduce prosthesis alignment at will during daily prosthesis fitting. A new alignment jig was designed and developed to facilitate quantification and prescription of prosthesis alignment for patellar-tendon-bearing (PTB) trans-tibial prostheses. The alignment jig provided instantaneous readings of the three-dimensional orientation and position of the socket relative to the prosthetic foot in standardised units. The inter- and intra-tester errors of the alignment jig in measuring prosthesis alignment were evaluated and demonstrated to have good reliability. The alignment jig was recommended to be used clinically after the conventional dynamic alignment procedure to document the prosthesis alignment. Further application of the alignment jig for systematic evaluation of the effects of prosthesis alignment on gait for trans-tibial amputees is suggested.

Artificial Limbs↗
PubMed1999

Outcome of surgical treatment of congenital muscular torticollis.

Eighty-four patients with congenital muscular torticollis were treated surgically in a 10-year period with a mean followup of 5 years (range, 2-13 years). All patients were classified into subgroups according to the type of congenital torticollis, the limitation of passive rotation of the neck, and other parameters, including head tilt and craniofacial asymmetry. Twenty-two (26.2%) patients underwent surgery before they were 1 year of age, 22.6% were between 1 and 3 years of age, 38.1% were between 3 and 10 years, and 13.1% were older than 10 years. Postoperative management included physiotherapy for 3 to 4 months and the application of a multiply adjustable torticollis brace for 10 weeks in children older than 2 years of age. Loss of the sternomastoid column was found in 82.6%, poor scar in 2.4%, lateral band in 47.2% and 1.2% required a second operation. The final overall score showed excellent results in 88.1%, good results in 8.3%, and fair to poor results in 3.6%. The most important factor affecting the overall result and outcome was found to be the age of the patient at the time of operation. However, this series also showed that for patients who were 10 years or older at the time of surgery, 63.6% had excellent results and 81.8% had good to excellent results, indicating the benefit of surgery even in the late cases.

Adolescent↗
PubMed1998

Diagnostic thoracic-computed tomography in radiotherapy for loco-regional recurrent breast carcinoma.

PURPOSE: This study was initiated to evaluate whether pretreatment diagnostic thoracic CT scan was useful for patients with loco-regional recurrent breast carcinoma, and to assess its impact on the design of radiotherapeutic treatment. METHODS AND MATERIALS: Between March 1991 and January 1997, 44 patients underwent thoracic CT examination with contrast material before the consideration of radiotherapy for their isolated loco-regional recurrent breast carcinoma. The CT radiographs were prospectively reviewed for additional findings clinically undetected by prior physical examination and plain-chest radiograph. The changes made in treatment design and dosage of radiation as a result of CT findings were recorded for analysis. The correlation between prognostic indicators and the CT findings was also studied. RESULTS: Twenty-two of 44 (50%) patients were found to have additional abnormalities detected only after thoracic CT examinations were performed. The strategy of radiation therapy was altered in 17 of 22 (77%) patients as a result. Patients with shorter disease-free interval (p = 0.08) and multiple sites of recurrence (p = 0.05) tended to have greater numbers of findings on CT scan previously unsuspected. Thus, CT scan is a valuable guide to treating loco-regional recurrent disease. CONCLUSION: Pretreatment diagnostic thoracic CT scan offers essential information that can alter treatment planning and thus optimize treatment strategy for a large proportion of patients with clinically isolated loco-regional recurrent breast carcinoma. In this population of patients we recommend that thoracic CT examination be considered before the initiation of radiation therapy.

Breast Neoplasms↗
PubMed1998

Posterior tibial nerve somatosensory cortical evoked potentials in adolescent idiopathic scoliosis.

STUDY DESIGN: Somatosensory-evoked potentials were used to evaluate neurologic function in patients with adolescent idiopathic scoliosis. OBJECTIVES: To compare the somatosensory-evoked potentials between patients with adolescent idiopathic scoliosis and healthy control individuals, and to determine the incidence of abnormal somatosensory function in patients with adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Somatosensory-evoked potentials are sensitive in detecting structural lesions in the somatosensory pathway. Previous studies on somatosensory function in patients with idiopathic scoliosis have demonstrated statistical differences in somatosensory-evoked potential latency between scoliotic and normal groups. However, no documentation of the actual incidence of abnormal somatosensory-evoked potentials is available. SUBJECTS AND METHODS: Posterior tibial nerve somatosensory cortical evoked potentials were evaluated on 147 young patients with adolescent idiopathic scoliosis and 31 healthy control individuals. RESULTS: Seventeen patients with idiopathic scoliosis showed pathologic evoked potentials. Among them were seven with absent somatosensory-evoked potential waveform and 10 with delayed latency. The results were reproducible on repeated measurement. CONCLUSIONS: Adolescent idiopathic scoliosis could be subdivided according to the somatosensory-evoked potential findings into two subgroups, those with and those without a somatosensory pathologic process. Potential clinical significance in predicting curve progression in idiopathic scoliosis could be pursued further.

Adolescent↗
PubMed1998

Lengthening of a one-bone forearm. A sequel of neonatal osteomyelitis.

An 8-year-old girl presented with marked shortening of the right forearm due to destruction of both the radius and ulna secondary to neonatal osteomyelitis. A one-bone forearm operation was performed to achieve a stable forearm. Two years later, the one-bone forearm was lengthened for 6 months by callus distraction (callotasis) achieving 12 cm of extra length. The patient was last followed up at the age of 16. The appearance and functional outcome of the right upper limb had been improved and she was independent in all activities of daily living.

Child↗
PubMed1998

The role of arthroscopy in ankle and subtalar degenerative joint disease.

Treatment options for degenerative joint disease of the ankle and subtalar joints are limited. When conservative management fails, the only effective procedure is arthrodesis. With the advent of the small arthroscope and the development of better instrumentation and distraction techniques, small joint arthroscopy has gained popularity as an important diagnostic and therapeutic tool in the treatment of ankle and subtalar disorders. Although the benefits of arthroscopic ankle arthrodesis are well established, and arthroscopic subtalar arthrodesis has been described recently, the role of arthroscopic debridement for degenerative joint disease of the ankle and subtalar joints remains controversial. Traditionally, operative arthroscopy for ankle arthritis has not met with great success; however, recent studies have shown that it can provide an interim alternative to arthrodesis in early arthritis with preserved range of motion. Lesions associated with arthritis, such as impinging osteophytes and loose bodies, can be treated effectively with arthroscopy.

Ankle Joint↗
PubMed1998

Pseudoaneurysm after high tibial osteotomy and limb lengthening.

A case of a young man with anterior tibial artery rupture and pseudoaneurysm formation that occurred during lengthening of a scarred limb is presented. Leg length discrepancy occurred because of previous distal femoral and proximal tibial fractures. Two corrective operations were performed 11 and 2 years earlier at another hospital. As limb deformity persisted, distal femoral and proximal tibial osteotomies combined with limb lengthening were performed. The aim was to achieve 120 mm (70 mm femoral, 50 mm tibial) lengthening. The operative and early postoperative course was uneventful. Twenty-six days after surgery (when femoral and tibial lengthening was 13.5 mm and 5.5 mm, respectively), blood began oozing from the operative scar during limb distraction. At 70 days after surgery (when femoral and tibia lengthening was 41.5 mm and 14 mm, respectively), a rupture and pseudoaneurysm of the anterior tibial artery became apparent. Documentation of a normal pulses in the foot after surgery, the late presentation of pseudoaneurysm, and the initiation of bleeding by limb distraction indicate that limb lengthening either aggravated an unrecognized arterial injury or precipitated de novo rupture of the anterior tibial artery scarred from previous trauma. The pseudoaneurysm was treated successfully by transarterial embolization.

Adult↗
PubMed1998

Determinants of axial and peripheral bone mass in Chinese adolescents.

OBJECTIVE: To determine the relation of puberty, physical activity, physical fitness, and calcium intake with bone mineral content (BMC) of the distal radius, and on bone mineral density (BMD) of the L2 to L4 vertebrae in a group of healthy Chinese adolescents. DESIGN: Cross sectional survey. SUBJECTS: A group of 179 healthy Chinese adolescents (92 boys and 87 girls) aged 12 to 13 years enrolled in the first year of the Tii Junior High School in Shatin, Hong Kong. Ninety four of the pupils enrolled were in the physical education major class (PE), and the other 85 were in the art major class (ARTS). MAIN OUTCOME MEASURES: Correlation of BMC of the distal radius and BMD of the L2 to L4 vertebrae with level of physical activity, physical fitness (isometric and isokinetic), muscle strength of the upper and lower limb, and calcium intake. RESULTS: BMC of the distal radius and BMD of the L2 to L4 vertebrae were significantly positively correlated. Univariate and regression analysis showed that age, pubertal staging, physical fitness, and muscle strength were significantly associated with bone mass in a positive way. Calcium intake and type of sport practised did not exert a significant influence on BMC of the distal radius and BMD of the L2 to L4 vertebrae in boys. The results for the BMD of the L2 to L4 vertebrae were similar in girls and boys; however, in girls, the BMC of the distal radius had a negative correlation with calcium intake. Physical fitness was a significant positive predictor of BMD of the L2 to L4 vertebrae. CONCLUSIONS: Among Chinese adolescents bone mass was positively influenced by certain measures of physical fitness as well as by age, weight, and pubertal stage.

Adolescent↗
PubMed1998

The conservative management of acute pyogenic iliopsoas abscess in children.

We describe three cases of acute pyogenic abscess of the iliopsoas in children treated conservatively. Two patients had image-guided aspiration and one was managed with antibiotics alone. All made a complete recovery. Acute pyogenic abscess of the iliopsoas in children can be treated effectively and safely with intravenous antibiotics and image-guided aspiration of the abscess.

Acute Disease↗
PubMed1998

Percutaneous intramedullary Kirschner wiring for displaced diaphyseal forearm fractures in children.

Displaced fractures of the forearm in children are often treated conservatively, but there is a relatively high incidence of redisplacement, malunion and consequent limitation of function. We have performed percutaneous Kirschner (K) wire fixation in 72 such children under the age of 14 years, of which 57 were reviewed for our study. Both the radius and ulna were fractured in 45 (79%), the radius only in eight and the ulna only in four. The mean initial angulation was 19 degrees in the lateral plane and 9 degrees in the anteroposterior plane for the radius and 15 degrees and 9 degrees, respectively, for the ulna. In 42 patients (74%) we performed closed reduction. In the remaining 15 (26%) closed reduction failed and an open reduction, through a minimal approach, was required before K wiring. At a mean follow-up of 20 months all patients had good functional results with an excellent range of movement. Only five had angulation of from 10 degrees to 15 degrees and none had nonunion, premature epiphyseal closure or deep infection. Percutaneous intramedullary K wiring for forearm diaphyseal fracture is a convenient, effective and safe operation, with minimal complications.

Adolescent↗
PubMed1998

Severe progressive deformities after limb lengthening in type-II fibular hemimelia.

Until recently the accepted treatment of choice for severe type-II fibular hemimelia has been Syme's or Boyd's amputation. The alternative of distraction lengthening using the Ilizarov technique is now available. We report three patients (four limbs) with type-II fibular hemimelia who were treated by the Ilizarov technique and followed up for two to six years. Severe progressive procurvatum and valgus deformity of the tibia and valgus deformity and lateral subluxation of the ankle were found in all four limbs. Multiple additional soft-tissue and bony surgery was necessary. In view of these problems we feel that reappraisal of the indications for lengthening in type-II fibular hemimelia is necessary.

Child↗
PubMed1998

Individual differences in P3 scalp distribution in older adults, and their relationship to frontal lobe function.

There is evidence that frontal lobe function may diminish in normal aging. The P3 component of the event-related brain potential (ERP) elicited by target events in an oddball paradigm becomes more frontally oriented in elderly subjects. It was hypothesized that the extent to which the P3 distribution is frontally oriented in old subjects may index less efficient frontal lobe function. In this study, bootstrapping methods were used to establish the reliability of the locations of maxima of surface brain activity obtained with ERP recordings from young and old subjects. The results indicated that brain activity maxima are reliable for a given individual. However, among the elderly only, there were also clear individual differences in the distribution of the P3 component elicited by target stimuli in an oddball paradigm. On the basis of these differences, the old subjects were divided into two groups. In line with predictions, those elderly subjects who showed frontal-maximal P3 scalp distributions had lower performance on standardized neuropsychological tests of frontal lobe function than those elderly subjects who showed posterior-maximal scalp topographies.

Adult↗