Biomedical subjects

R C Chan

Publications and source records attributed to R C Chan.

At least 37 records · Page 2Linked to original sources

PubMed2001

The outcome of shunted hydrocephalic children.

BACKGROUND: Neurological sequelae and mental retardation may result from different etiological types of hydrocephalus. The aim of our study is to determine the intellectual development and the "shunt history" of these children with regard to the complications and revision rates. METHODS: We reviewed the medical history of non-tumoral pediatric hydrocephalic patients who had received first shunt insertions between 1983 and 1997 and had been regularly followed up at the out-patient clinics of Taipei Veterans General Hospital. These patients were categorized into five different etiological groups. Their intelligence test scores and the surgical morbidity encountered over this period were used as the main outcome measures. RESULTS: Out of the seventy-three patients, post-meningitis hydrocephalus patients had the significantly highest shunt revision rate (2.50 +/- 0.82, p = 0.01). They also showed retardation in IQ scores, but the different was not significant when compared with other groups. The results of IQ tests were not related to either the age of initial shunt insertion (p = 0.461) or revision rates (p = 0.292). For physical disabilities, post-meningitis hydrocephalic patients showed-highest incidence of epilepsy (40%) while hydrocephalic patients associated with myelomeningocele had the highest incidence of motor deficits (56.25%). CONCLUSIONS: Childhood hydrocephalic patients had different developmental neuroimpairments with respect to different etiologies. This study provides information about the physical and mental outcome of post-operative hydrocephalic patients which is valuable to assist in counsel of their families.

Cerebrospinal Fluid Shunts↗

PubMed2001

Dysexecutive symptoms among a non-clinical sample: a study with the use of the Dysexecutive Questionnaire.

Clinical studies indicate that damage to the frontal lobes may lead to a set of symptoms collectively known as 'Dysexecutive syndrome', which is characterized by changes in emotion, personality, motivation, behaviour and cognitive aspects. Factor analytical study using questionnaires measuring dysexecutive problems in everyday life also suggests a fractionation of the dysexecutive syndrome among patients with neurological disorders. As yet, very little research has been conducted to explore the base-rate of executive problems in everyday life among the non-clinical population. This pilot study aimed to explore dysexecutive behaviour similar to that of dysexecutive syndrome reported by a non-clinical sample. A total of 93 presumably normal participants were recruited. The Dysexecutive Questionnaire and a set of clinical tests of executive function were administered to all the participants. A 5-factor solution very similar to that of a previous study was derived: inhibition (factor 1), intentionality (factor 2), knowing-doing dissociation (factor 3), in-resistance (factor 4), and social regulation (factor 5). Correlation was established among the derived factors and tests of executive function. This study provides empirical evidence that a non-clinical sample may encounter similar dysexecutive behaviours in daily life. The issue of the fractionation of the executive system among the non-clinical sample will also be discussed.

Adult↗

PubMed2000

How does spinal cord injury affect marital relationship? A story from both sides of the couple.

PURPOSE: To explore the impact of spinal cord injury (SCI) upon the family and marital relationship in Hong Kong. METHOD: Semi-structured interviews were conducted on 66 persons with SCI and 40 spouses. Qualitative information on family and marital relationships, life satisfaction, social functioning and leisure activities was transcribed and analysed. RESULTS AND CONCLUSION: It was found that the impact of the SCI was manifested in different but interrelated aspects onto the individuals and their spouses. However, many of the problems were due to the lack of communication between them. Rehabilitation professionals should then treat the couple as a single unit in order to facilitate mutual understanding and get rid of any distorted perception.

Cultural Characteristics↗

PubMed2000

Anti-restenotic effect of copper-62 liquid-filled balloon in porcine coronary arteries: novel use of a short half-life positron emitter.

PURPOSE: To determine the efficacy of the use of copper-62, a positron emitter with a half-life of 9.7 minutes, as an intracoronary brachytherapy (IRBT) source in the prevention of neointima formation (NF) following overstretch balloon injury (BI) in the porcine model. METHODS AND MATERIALS: Sixteen swine were treated after BI to their left anterior descending (LAD), left circumflex (LCX), and/or right coronary artery (RCA). Twelve of the injured arteries received placebo and 10 received 25 Gy, delivered to 0.5 mm from the surface of the treatment balloon filled with liquid (62)Cu. Dosimetry was based on Monte Carlo calculations. Two weeks after treatment, the animals were sacrificed, and the treated coronaries were perfusion-fixed and stained. Intimal area (IA) and medial fracture length (FL) were analyzed by computer-aided histomorphometry. RESULTS: The ((62)Zn/(62)Cu) generator, together with a rapid concentration process, was successful in delivering the short-lived (62)Cu at the high concentration required for intravascular brachytherapy (IVBT). The fracture length in the two groups was similar (2.10 +/- 0.57; 2.02 +/- 0.77; p = NS). Arteries studied showed significant reduction in NF (IA: 0.23 +/- 0.47 mm(2) vs. 1.08 +/- 0.57 mm(2); p < 0.01. IA/FL = 0.09 +/- 0.17 mm vs. 0.51 +/- 0.21 mm; p < 0.01). CONCLUSIONS: This study demonstrated that use of liquid (62)Cu as an IVBT source is safe and feasible. All 16 swine tolerated the treatment well with no radiation-induced side effects or symptoms throughout the 2-week period. The isotope delivered the dose necessary to inhibit NF in the porcine coronary BI model.

Animals↗

PubMed2000

The pattern of coping in persons with spinal cord injuries.

PURPOSE: To examine the modes of coping and adjustment of persons with spinal cord injuries (SCI) in Hong Kong. METHOD: A cross-sectional design was adopted. Structured questionnaires and semi-structured interviews on 66 persons with SCI were completed. Cluster analysis was performed to identify persons with SCI who are at risk for psychosocial morbidity. RESULTS/CONCLUSION: The group at risk for developing psychological difficulties is characterized by high scores on external locus of control, inadequate coping modes, and low perceived social support. High levels of depression, social role dissatisfaction, care-giving burden, low levels of life satisfaction, and marital maladjustment are commonly noted. Rehabilitation of persons with SCI should also aim at promoting perceived personal control, acceptance of physical status, and realistic appraisal of stressful situations to facilitate better adjustment and coping with commonly identified stresses and difficulties. Counselling should be initiated at an early stage to reduce the development of distorted perceptions so that the needs and concerns of individuals with SCI may be better met and resolved. The frustrations due to unmet expectations may be prevented at an early stage through build-up of more realistic understandings related to the illness and living with the illness.

Adaptation, Psychological↗

PubMed2000

Intracoronary gamma-radiation therapy after angioplasty inhibits recurrence in patients with in-stent restenosis.

BACKGROUND: Treatment of in-stent restenosis presents a critical limitation of intracoronary stent implantation. Ionizing radiation has been shown to decrease neointimal formation within stents in animal models and in initial clinical trials. We studied the effects of intracoronary gamma-radiation therapy versus placebo on the clinical and angiographic outcomes of patients with in-stent restenosis. METHODS AND RESULTS: One hundred thirty patients with in-stent restenosis underwent successful coronary intervention and were then blindly randomized to receive either intracoronary gamma-radiation with (192)Ir (15 Gy) or placebo. Four independent core laboratories blinded to the treatment protocol analyzed the angiographic and intravascular ultrasound end points of restenosis. Procedural success and in-hospital and 30-day complications were similar among the groups. At 6 months, patients assigned to radiation therapy required less target lesion revascularization and target vessel revascularization (9 [13.8%] and 17 [26.2%], respectively) compared with patients assigned to placebo (41 [63.1%, P=0.0001] and 44 [67.7%, P=0.0001], respectively). Binary angiographic restenosis was lower in the irradiated group (19% versus 58% for placebo, P=0.001). Freedom from major cardiac events was lower in the radiation group (29.2% versus 67.7% for placebo, P<0.001). CONCLUSIONS: Intracoronary gamma-radiation used as adjunct therapy for patients with in-stent restenosis significantly reduces both angiographic and clinical restenosis.

Aged↗

PubMed2000

Intracoronary beta-radiation therapy inhibits recurrence of in-stent restenosis.

BACKGROUND: Intracoronary gamma-radiation therapy reduces recurrent in-stent restenosis (ISR). This study, BETA WRIST (Washington Radiation for In-Stent restenosis Trial) was designed to examine the efficacy and safety of the beta-emitter 90-yttrium for the prevention of recurrent ISR. METHODS AND RESULTS: A total of 50 consecutive patients with ISR in native coronaries underwent percutaneous transluminal coronary angioplasty, laser angioplasty, rotational atherectomy, and/or stent implantation. Afterward, a segmented balloon catheter was positioned and automatically loaded with a 90-yttrium, 0.014-inch source wire that was 29 mm in length to deliver a dose of 20.6 Gy at 1.0 mm from the balloon surface. In 17 patients, manual stepping of the radiation catheter was necessary for lesions >25 mm in length. The radiation was delivered successfully to all patients, with a mean dwell time of 3.0+/-0.4 minutes. Fractionation of the dose due to ischemia was required in 11 patients. At 6 months, the binary angiographic restenosis rate was 22%, the target lesion revascularization rate was 26%, and the target vessel revascularization rate was 34%; all rates were significantly lower than those of the placebo group of gamma-WRIST. CONCLUSIONS: beta-Radiation with a 90-yttrium source used as adjunct therapy for patients with ISR results in a lower-than-expected rate of angiographic and clinical restenosis.

Adult↗

PubMed2000

Serial volumetric intravascular ultrasound analysis of the efficacy of beta irradiation in preventing recurrent in-stent restenosis.

We compared postintervention and follow-up intravascular ultrasound findings of 25 patients from the beta-Washington Radiation for InStent restenosis Trial (in which all patients received radiation) and 75 patients from the Washington Radiation for InStent restenosis Trial (in which patients were randomized to gamma irradiation). The decrease in lumen volume was similar for beta versus gamma and less in both gamma versus placebo and beta versus placebo; the increase in intimal hyperplasia volume was similar for beta versus gamma and greater in both beta versus placebo and gamma versus placebo.

Beta Particles↗

PubMed2000

Intracoronary brachytherapy not associated with changes in major side branches.

Intravascular radiation (IR) is emerging as a potential solution for the prevention and treatment of restenosis. Subacute thrombosis late coronary occlusion of the target lesion after intracoronary brachytherapy has been described in two studies. None of these studies assessed in detail the evolution of side branches following IR. The purpose of this study was to determine the frequency of side-branch occlusion in patients undergoing IR. We evaluated the procedural and 6-month follow-up angiograms of 170 consecutive patients enrolled in the GAMMA-I and WRIST studies who presented a major side branch (diameter > 1.5 mm) at the treated lesion. Major side branches treated during the procedure and/or total occlusion of the main branch were excluded for analysis. Sixty-three patients (control = 30, irradiated = 33) were identified and side branches were classified in one of three categories: no significant stenosis, > 50% stenosis, and occluded. The baseline patient and lesion characteristics were similar among the classified groups. No difference was observed between the control and irradiated arteries after the procedure for side-branch occlusion (14% and 9%, P = NS). A significant decrease of restenosis was observed after IR compared to control (20% vs. 70%: P < 0.001). The patency rates and rates of side-branch occlusion were similar between the two groups. However, in the control group, 50% of the side-branch occlusions that occurred after the procedure were patent at 6-month follow-up. In contrast, in the irradiated group, the incidence of side-branch occlusion increased from 9% to 15% at 6-month follow-up in the irradiated group. Low doses of radiation applied to noninjured side branches are not associated with adverse effects. The absence of restoration patency followed by IR is most likely a consequence of a delayed healing process.

Aged↗

PubMed2000

Coping with spinal cord injury: personal and marital adjustment in the Hong Kong Chinese setting.

STUDY DESIGN: A cross-sectional retrospective study was carried out with structured questionnaires and semi-structured interviews on 66 persons with spinal cord injury (SCI) and 40 spouses. OBJECTIVES: The study aimed to explore the psychosocial adjustment of Hong Kong Chinese couples at the post SCI stage. An important study interest was the impact of care-giving in spouses of persons with SCI. SETTING: Three major regional rehabilitation centres and one community resource centre in Hong Kong. METHODS: A set of psychometric measures tapping different aspects of psychological functioning was included. These were locus of control (Levenson's Internality, Powerful Others, and Chance Scale), perceived social support (Provision of Social Relationship), coping strategies (Ways of Coping Checklist), marital adjustment (Dyadic Adjustment Scale), caregiving burden (Caregiver Burden Inventory), depression (Beck Depression Inventory), life satisfaction (Satisfaction with Life Situation), and social role adjustment (Katz Adjustment Scale - Relative Form). RESULTS: Persons with SCI with pre-injury marriage were more depressed (P<0.05) as compared with those with post-injury marriage. However, the two groups did not differ in terms of satisfaction with life situation and social role dissatisfaction. The spouses in the preinjury marriage reported a significantly higher score in time-dependent burden than those in the post-injury marriage (P<0.05). Care-giving burden was associated with locus of control, social support, and modes of coping (P<0.05). CONCLUSION: The impact of SCI is a long-lasting effect not limited to the patients but also extending to their spouses. Findings from the adjustment outcomes and coping styles of persons with SCI and their spouses indicate that they are not passive victims. A similar injury may produce different outcomes in different individuals. Rehabilitation professionals should thus be alert to both the couple's differing needs and idiosyncrasies in their helping process.

Adaptation, Psychological↗

PubMed2000

Early attachment of anaerobic bacteria may play an important role in biliary stent blockage.

BACKGROUND: In vitro studies have demonstrated that ciprofloxacin suppresses Escherichia coli attachment on stents, and ciprofloxacin has been shown to prolong stent patency in cats. However, clinical studies with antibiotic prophylaxis have produced conflicting results. The aim of this study was to isolate and identify the bacteria that attach early on unblocked stents removed from patients and to study their enzyme activities. METHODS: Eighteen unblocked biliary stents were removed from 17 patients (benign obstruction in 14 and malignant obstruction in 4). All patients received antibiotic prophylaxis (mean of 6 days). Stents were in place for a mean of 33 days. The inside of stents was scraped and sludge was cultured aerobically and anaerobically. Identification of isolated bacteria and measurement of beta-glucuronidase and phospholipase C activities were performed by using standard techniques. Gastric and duodenal juice from 18 patients with no biliary diseases was used as control samples. RESULTS: All stents were patent and only 6 had visible sludge. There were 19 anaerobes isolated from 16 stents (Clostridium perfringens 13, Clostridium bifermentans 4 and Bacteroides fragilis 2). Phospholipase C was detected in all Clostridium species. beta-Glucuronidase was produced only by 12 of 13 C perfringens isolates. Sixteen aerobes including Enterococcus species and Bacillus species were isolated but none produced beta-glucuronidase or phospholipase C. There were no aerobic gram-negative bacteria isolated from stents. Clostridium species and B fragilis were not recovered from the control samples. CONCLUSIONS: In patients who had received antibiotic prophylaxis against gram-negative bacterial infection, anaerobic bacteria may play a role in initiating stent blockage.

Adult↗

PubMed2000

Attentional deficits in patients with closed head injury: a further study to the discriminative validity of the test of everyday attention.

This study aimed to explore the attentional performance of patients with closed head injury (CHI) and to examine the discriminative validity of the Test of Everyday Attention (TEA) in this clinical population. A sample of 21 patients with CHI was recruited for this study. Another sample of matched controls was also recruited for comparison. In addition, other clinical tests of attention and questionnaires on everyday life cognitive failures were also given to the participants during the assessment session. The results showed that patients with CHI exhibited significant differences in most of the TEA subtests, as well as clinical tests of attention, as compared with the matched controls. These findings suggest that the majority of the TEA subtests are able to discriminate out those patients with attentional deficits from the normal population in terms of sustained attention, selective attention, divided attention, and attentional switching.

Adult↗

PubMed2000

A new model-based technique for enhanced small-vessel measurements in X-ray ciné-angiograms.

Arterial diameter estimation from X-ray ciné angiograms is important for quantifying coronary artery disease (CAD) and for evaluating therapy. However, diameter measurement in vessel cross sections < or =1.0 mm is associated with large measurement errors. We present a novel diameter estimator which reduces both magnitude and variability of measurement error. We use a parametric nonlinear imaging model for X-ray ciné angiography and estimate unknown model parameters directly from the image data. Our technique allows us to exploit additional diameter information contained within the intensity profile amplitude, a feature which is overlooked by existing methods. This method uses a two-step procedure: the first step estimates the imaging model parameters directly from the angiographic frame and the second step uses these measurements to estimate the diameter of vessels in the same image. In Monte-Carlo simulation over a range of imaging conditions, our approach consistently produced lower estimation error and variability than conventional methods. With actual X-ray images, our estimator is also better than existing methods for the diameters examined (0.4-4.0 mm). These improvements are most significant in the range of narrow vessel widths associated with severe coronary artery disease.

Arterial Occlusive Diseases↗

PubMed2000

Stress and coping in spouses of persons with spinal cord injuries.

OBJECTIVE: To examine the sources of stress and the patterns of coping of spouses of persons with spinal cord injuries (SCI) among Hong Kong Chinese. DESIGN: A cross-sectional correlation design. A set of structured questionnaires and semi-structured interviews were administered. SUBJECTS: Forty spouses of persons with SCI were recruited and interviewed. OUTCOME MEASURES: These included coping strategies, depression, care-giving burden, life satisfaction and marital adjustment. RESULTS: The most stressful situations reported by the participants concerned health issues of their injured partners, the family and marital interactions, and the care-giving burden imposed on them. Cluster analysis indicated a potential at-risk group, characterized by high scores in external locus of control, inadequate coping modes and limited social support. They were noted to manifest high levels of depression, care-giving burden, low levels of life satisfaction and marital adjustment. CONCLUSION: The identification of the potential at-risk group indicates that spouses of persons with SCI suffer levels of stress comparable to those of their injured partners. Rehabilitation plans should include this potential at-risk group to help them release the stress and to prevent them from developing clinically significant mental disorders.

Adaptation, Psychological↗

PubMed2000

Sudomotor abnormalities in reflex sympathetic dystrophy.

BACKGROUND: Intractable pain and sweating dysfunction can occur in patients with reflex sympathetic dystrophy (RSD). We, therefore, investigated autonomic function by measuring sympathetic skin response (SSR) in these patients. This method provides useful information regarding the pathophysiologic changes in and clinical evaluation of RSD. METHODS: Twenty-six RSD patients and 22 age-matched normal subjects were involved in our investigation. Three significant stages of RSD were classified through three-phase bone scanning of the wrist, carpal and metacarpal bones. There were 11 patients in stage I RSD, nine in stage II and six in stage III. SSRs were recorded from the bilateral palms of each subject simultaneously using electrical stimulation of the median nerve in the wrist. Latency and amplitude side ratios were calculated and compared with the control group. RESULTS: The affected/normal (A/N) hand amplitude ratios were significantly lower in stage I RSD, and stage II RSD patients exhibited significantly higher A/N amplitude ratios compared with the control group. A/N amplitude and A/N latency ratios in stage III RSD did not change significantly. The A/N latency ratios in stage I RSD were significantly higher than those of the control group and those of stage II RSD. In one stage I patient and three stage III patients, SSRs were bilaterally unobtainable. CONCLUSIONS: It appears that abnormal SSRs may be associated with autonomic disturbance in RSD patients.

Adult↗

PubMed1999

Angiotensin-converting enzyme inhibition as antiatherosclerotic therapy: no answer yet. QUIET Investigators. QUinapril Ischemic Event Trial.

Angiotensin-converting enzyme inhibitors have proven to be of clinical benefit in congestive heart failure. Whether they also provide benefit to patients with coronary artery disease in the absence of congestive heart failure via an antiatherosclerotic mechanism is a question the QUinapril Ischemic Event Trial quantitative coronary angiography (QCA) study attempted to answer: 1,750 patients with normal left ventricular function who were undergoing coronary angiography and angioplasty were randomized to 20 mg/day of quinapril versus placebo and followed for 3 years for cardiac end points. A randomly selected subgroup of the total cohort underwent follow-up angiography. The primary QCA end point was the categorical designation of progression versus nonprogression, defined either by QCA or by a cardiac event in patients selected for the QCA trial who had no usable follow-up x-ray film. Secondary end points in patients with 2 angiograms were: new stenosis development, change in minimum lumen diameter index, and change in percent diameter stenosis index. There were 119 progressors among 243 placebo-treated patients (49%) and 111 progressors among 234 quinapril-treated patients (47%) (p = NS). There were 44 patients with new stenosis development in the placebo group (19%) and 50 (22%) in the quinapril group (p = NS). Change in minimum lumen diameter index was -0.21+/-0.03 mm in the placebo group and -0.18+/-0.03 mm in the quinapril group (p = NS). Finally, change in percent diameter stenosis index was +5.1+/-1.0 in the placebo group and +3.5+/-1.0 in the quinapril group (p = NS). Potential confounders of this trial are presented and discussed.

Adult↗

PubMed1999

Dynamic measurement of bone blood perfusion with modified laser Doppler imaging.

Although the mechanisms are not clearly defined, blood flow may play an important role in moderating skeletal adaptation. Most techniques currently available to measure blood flow in bone are time-consuming and require destruction of the tissue, but laser Doppler technology offers a less invasive method. The present study assessed whether laser Doppler perfusion imaging could detect changes in perfusion in cortical bone. By use of modified laser Doppler perfusion imaging with an adjustable, incorporated, near infrared-laser gain photodetection system, perfusion of blood in the mid-diaphyseal tibial cortex of New Zealand White rabbits (n = 5) was measured before, during, and after occlusion of the femoral artery. During occlusion, perfusion decreased 69% compared with control levels; removal of the arterial clip caused flux values to return to near normal. Laser Doppler perfusion imaging provides a two-dimensional image related to blood flow, and the results of this pilot study suggest that it may be an effective technique for imaging in vivo dynamic changes in perfusion in cortical bone.

Animals↗

PubMed1999

Increased CD4+ T-lymphocyte senescence fraction in advanced human immunodeficiency virus type 1 infection.

Human immunodeficiency virus type 1 (HIV-1) infection is accompanied by peripheral CD4+ T-cell losses. CD4+ T-cell numbers often increase during antiviral treatment of acquired immune deficiency syndrome (AIDS), however, alterations in the CD4+ T-cell repertoire have not been completely corrected for these patients. Such individuals remain at increased risk of infection. Although senescence of the CD4+ T cells has not been adequately evaluated for advanced HIV-1 infection, hypothetically, replicative senescence could complicate therapeutic reconstitution of the CD4+ T cells in AIDS. In this study, correlates of replicative senescence, terminal restriction fragment (TRF) length and percentage short (< 5.0 kb) telomeric DNA (senescence fraction), were measured for the CD4+ T cells of HIV-1-infected patients with peripheral CD4+ T-cell counts of < 200/mm3. The results show that for advanced HIV-1 infection the TRF length of the CD4+ T cells is decreased (P < 0.01), and the senescence fraction increased (P < 0.05), when compared with uninfected controls. These findings suggest that cellular senescence may contribute to disruption of CD4+ T-cell diversity observed following the therapeutic, immunologic reconstitution of AIDS.

Adult↗