Search PubMed⌕ Search

Biomedical subjects

E Wong

Publications and source records attributed to E Wong.

At least 37 records · Page 2Linked to original sources

Simplified intensity-modulated arc therapy for dose escalated prostate cancer radiotherapy.

Simplified intensity-modulated arc therapy (SIMAT) employs forward planned, conformal, and avoidance arc combinations with dynamic multileaf collimation (MLC) as a simpler alternative to other forms of intensity-modulated radiotherapy (IMRT). In this work, we compare SIMAT with 4-field (4F) and 6-field (6F) 3D conformal radiation therapy (CRT) for prostate cancer treatment. Prostate, seminal vesicle, bladder, and rectum were contoured on the CT images of 10 patients being planned for radiotherapy. Two planning target volumes (PTV) were defined: PTV1 (prostate + seminal vesicles + 1.0-cm margin) and PTV2 (prostate + 1.0-cm margin). SIMAT, 4F, and 6F plans were generated with a prescription dose of 78 Gy to prostate and 54 Gy to the seminal vesicles. Differences in the 3 techniques in terms of target and rectal coverage were compared. In addition, dose distributions of the SIMAT plans were verified with measurements in a phantom. Mean dose to PTV2 (4F, 76 Gy; 6F, 78 Gy; SIMAT, 76 Gy) and the dose delivered to 95% of the target volume (D(95)) were similar between the 3-techniques. Target conformity was better with SIMAT. Mean dose and calculated NTCP for the rectum were lower for SIMAT than those for 4F and 6F plans (4F 55.6 Gy vs. 6F 49.0 Gy vs. SIMAT 42.7 Gy). Mean dose to femoral heads was lower for the 4F technique vs. 6F and SIMAT techniques (4F 44.5 Gy vs. 6F 48.9 Gy vs. SIMAT 49.5 Gy). In-phantom measurement demonstrated good agreement between the plans and SIMAT treatments delivered in phantom. We concluded that SIMAT demonstrates advantages over 4F and 6F in terms of target conformity mean rectal dose and NTCP with good reproducibility in phantom. On the basis of this analysis, we have commenced a clinical pilot study of SIMAT for prostate cancer radiotherapy.

Film Dosimetry↗

Auricular anthropometry of Hong Kong Chinese babies.

OBJECTIVES: To provide a database of the auricular measurements of Chinese infants born in Hong Kong. DESIGN: Prospective cross-sectional study. SETTING AND SAMPLE POPULATION: A total of 2384 healthy singleton, born consecutively at the Prince of Wales Hospital and the Union Hospital from October 1998 to September 2000, were included in the study. The range of gestation was 33-42 weeks. MEASUREMENTS AND RESULTS: Measurements included ear width (EW), ear length (EL) and ear position (EP). The data show generally higher values for males in the parameters measured. When compared with previously published data for Caucasian and Jordanian term babies, Chinese babies have shorter EL. The ears were within normal position in nearly all our infants. CONCLUSION: The human ear appears to grow in a remarkably constant fashion. This study establishes the first set of gestational age-specific standard of the ear parameters for Chinese new-borns, potentially enabling early syndromal diagnosis. There are significant inter-racial differences in these ear parameters.

Asian People↗

An algorithm for systematic selection of beam directions for IMRT.

Selection of the number of beams and their directions can be an important problem in radiation therapy, especially when a tumor surrounds a critical organ or is surrounded by multiple critical organs. Beam directions, in this sense, are chosen to not only avoid critical organs, but also to achieve better target dose uniformity. In intensity-modulated radiation therapy (IMRT), optimization of beam directions is further complicated due to the dependence of one beam direction on its corresponding beamlet intensities and the beamlet intensities of all other beam directions. The result is an excessively enlarged search space, even when the number of beams is small (two to three). Until now, only a handful of publications exist regarding beam direction optimization in IMRT. Here, we report a new systematic approach that determines a suitable number of "more optimal" beam directions without optimizing a complicated objective function or resorting to brute force. We start by assuming that beam directions chosen for an N-beam plan are candidates for beam directions in the search for an (N + 1)-beam plan. Knowing that beam directions in an N-beam plan are not always the best choices for the (N + 1)-beam plan, we introduce into the beam direction selection process an analysis of the beamlet weights of every beam direction set sampled. If the relative weights of any particular beam compared to other beams are insignificant and hence have no significant effect on the quality of the treatment plan, then we eliminate this beam from the plan. The algorithm terminates basically when the relative weights of the last beam compared to other beams are insignificant or the replacement of an eliminated beam does not improve the plan. This concept was applied to three two-dimensional phantoms and each plan was compared to a standard equally spaced IMRT plan in terms of dose distributions, dose-volume histograms, and objective function values. The results show improvements in both target dose uniformity and critical organ sparing often with a fewer number of beams than standard equally spaced beam plans.

Algorithms↗

Transient adrenocortical insufficiency of prematurity and systemic hypotension in very low birthweight infants.

OBJECTIVES: A proportion of preterm, very low birthweight (VLBW, < 1500 g) infants may show inadequate adrenal response to stress in the immediate postnatal period. The human corticotrophin releasing hormone (hCRH) stimulation test was used to: (a) determine the relation between pituitary-adrenal response and systemic blood pressure in these infants; (b) characterise the endocrinological features of transient adrenocortical insufficiency of prematurity (TAP). STUDY DESIGN: A total of 226 hCRH tests were performed on 137 VLBW infants on day 7 and 14 of life in a tertiary neonatal centre. RESULTS: Basal, peak, and incremental rise in serum cortisol (Delta Cort(0-30)) on day 7 were associated significantly with the lowest systolic, mean, and diastolic blood pressures recorded during the first two weeks of life (r > 0.25, p < 0.005). These cortisol concentrations also correlated significantly but negatively with the maximum and total cumulative dose of dopamine (r > -0.22, p < 0.02), dobutamine (r > -0.18, p < 0.04), and adrenaline (r > -0.26, p < 0.004), total volume of crystalloid (r > -0.22, p < 0.02), and duration of inotrope treatment (r > -0.25, p < 0.006). Multivariate regression analysis of significant factors showed that the lowest systolic, mean, and diastolic blood pressures remained independently associated with serum cortisol (basal, peak, and Delta Cort(0-30)) on day 7. Hypotensive infants requiring inotropes (group 2) were significantly less mature and more sick than infants with normal blood pressure (group 1). The areas under the ACTH response curves were significantly greater in group 2 than in group 1, on both day 7 (p = 0.004) and day 14 (p = 0.004). In contrast, the area under the cortisol response curve was significantly greater in group 1 than in group 2 on day 7 (p = 0.001), but there was no significant difference between the two groups on day 14. In addition, serum cortisol at the 50th centile in hypotensive infants had high specificity and positive predictive value (0.80-0.93 and 0.81-0.89 respectively) for predicting early neonatal hypotension. CONCLUSIONS: This study characterises the fundamental endocrinological features of TAP: normal or exaggerated pituitary response; adrenocortical insufficiency; good recovery of adrenal function by day 14 of postnatal life. The results also provide the centiles of serum cortisol for hypotensive patients and infants with normal blood pressure, and show a significant relation between serum cortisol and blood pressure in VLBW infants.

Adrenal Insufficiency↗

Early pituitary-adrenal response and respiratory outcomes in preterm infants.

OBJECTIVE: To assess the influence of circulating (basal) and stimulated plasma adrenocorticotrophin (ACTH) and serum cortisol on the duration of oxygen supplementation and development of chronic lung disease (CLD) in preterm, very low birthweight infants. METHODS: A total of 226 human corticotrophin releasing hormone stimulation tests were performed on 137 very low birthweight infants on days 7 and 14 in a tertiary neonatal centre. RESULTS: Multivariate regression analysis showed that the duration of oxygen supplementation was negatively associated with birth weight, but positively associated with alveolar-arterial oxygen gradient (A-aDO(2)) on the first day and with basal serum cortisol on day 14. In addition, the multivariate classification and regression trees model indicated that the two most useful indices for predicting CLD were clinical risk index for babies (CRIB) score (> 9) and peak serum cortisol (> 740 nmol/l) on day 14. The sensitivity, specificity, positive and negative predictive values of these factors for predicting CLD were 53%, 80%, 81%, and 70% respectively. CONCLUSIONS: The findings suggest that birth weight, severity of initial respiratory failure as reflected by the A-aDO(2) gradient, and continuing "stress" with persistent increase in serum cortisol on day 14 are significant risk factors associated with the duration of oxygen supplementation, whereas early pituitary-adrenal response (basal and peak plasma ACTH and serum cortisol on day 7) is not an independent risk factor. Although CRIB score in combination with peak serum cortisol on day 14 are useful predictors of CLD, the need to use a stimulation test and the relatively late timing of the forecast render these indices unattractive for routine clinical use.

Adrenocorticotropic Hormone↗

Combined use of alcohol hand rub and gloves reduces the incidence of late onset infection in very low birthweight infants.

OBJECTIVE: To assess the incidence of late onset (> 72 hours) infection and necrotising enterocolitis (NEC) in very low birthweight (VLBW) infants in two 36 month periods using two hand hygiene protocols: conventional handwashing (HW; first 36 month period); an alcohol hand rub and gloves technique (HR; second 36 month period). METHOD: VLBW infants admitted to the neonatal intensive care unit during the period December 1993-November 1999 were eligible. A new hand hygiene protocol using alcohol handrub and gloves was introduced in December 1996. Each patient's case record was reviewed retrospectively by two independent investigators using a standard data collection form. The incidence of NEC and systemic infections, including bacterial or fungal septicaemia, meningitis, and peritonitis, in the two periods were compared. RESULTS: The HW and HR groups contained 161 and 176 VLBW infants respectively. The incidence of late onset systemic infection decreased from 13.5 to 4.8 episodes (including NEC)/1000 patient days after introduction of the HR regimen, representing a 2.8-fold reduction. Similarly, the incidence of Gram positive, Gram negative, and fungal infections decreased 2.5-fold, 2.6-fold, and 7-fold respectively. There was also a significant reduction in the incidence of NEC in the HR group (p < 0.0001). Subgroup analysis revealed that the incidence of methicillin resistant Staphylococcus aureus (MRSA) septicaemia was significantly decreased in the second 36 month period (p = 0.048). The clinical data suggest that infants in the HW group had significantly earlier onset of sepsis (p < 0.05) and required oxygen supplementation for longer (p < 0.05) than those in the HR group. Significantly more VLBW infants were discharged from the neonatal intensive care unit without ever being infected (p < 0.0001), and also significantly fewer infants had more than one episode of infection in the HR group (p < 0.0001). CONCLUSION: The introduction of the HR protocol was associated with a 2.8-fold reduction in the incidence of late onset systemic infection, and also a significant decrease in the incidence of MRSA septicaemia and NEC in VLBW infants. This decrease in infection rate was maintained throughout the second 36 month period.

2-Propanol↗

Interferon treatment of multiple pulmonary malignancies associated with papilloma virus.

Over a period of four years, beginning in spring 1988, a previously healthy man developed a primary squamous cell carcinoma of the tonsil, treated with radiotherapy, followed by 10 distinct, primary bronchial squamous cell carcinomas. Four of the cancers were surgically resected, all of which were positive by hybridization for human papilloma virus (type 16). Following the institution of alpha interferon, three smaller lesions disappeared and a larger one shrank in size, facilitating surgical resection. Over the following seven years no new ones have appeared. The finding of papilloma virus in malignancies should prompt consideration of antiviral therapy.

Adult↗

Plasma ghrelin and resistin concentrations are suppressed in infants of insulin-dependent diabetic mothers.

This study aimed to investigate 1) the effect of maternal diabetes mellitus on ghrelin, resistin, leptin, and insulin in term newborns; 2) the interrelationship of these metabolic hormones in the early postnatal period; and 3) the association of the hormones with anthropometric parameters at birth. A total of 120 term newborns were prospectively enrolled and categorized into three groups: 40 were infants of nondiabetic mothers (group N), 42 were infants born to mothers with gestational diabetes on low energy dietary treatment (group D), and 38 were infants born to mothers with preexisting or severe gestational diabetes who required exogenous insulin for stabilization of blood sugar during pregnancy (group I). Plasma ghrelin and resistin were significantly lower in group I than in either group N or group D infants (P < 0.048). Plasma ghrelin and subscapular skinfold thickness were significantly higher in female than in male infants [plasma ghrelin: median (interquartile range), 3.8 (3.0-4.8) vs. 3.0 (2.4-4.0) ng/ml in females and males, respectively; P = 0.003; subscapular skinfold thickness: 4.9 (4.2-5.6) vs. 4.6 (3.9-5.2) mm; P = 0.03]. In group N, plasma ghrelin was significantly, but negatively, associated with birth weight (r = -0.31; P = 0.05) and body length (r = -0.33; P = 0.04), whereas in group I, plasma ghrelin was negatively correlated with plasma resistin (r = -0.37; P = 0.02). Plasma ghrelin and resistin are suppressed in infants of insulin-dependent diabetic mothers, suggesting that the metabolic hormonal system is probably operational in fetal and early postnatal life. A low circulating ghrelin concentration may be advantageous to these infants, because a reduction in appetite may prevent excessive weight gain postnatally and counterbalances the in utero anabolic effect of hyperinsulinism in poorly controlled diabetic mothers. The suppressive effect of insulin on resistin may partially explain the excess accumulation of adipose tissue in infants of diabetic mothers by reducing the inhibitory effect of resistin on adipogenesis. Female infants have significantly higher plasma ghrelin levels than male infants, suggesting that sexual dimorphism exists in utero. This study has also shown an association between some of the metabolic hormones in specific groups of infants and thus suggests that these hormones could have interacted in utero to regulate growth and fat storage during this critical period.

Diabetes Mellitus, Type 1↗

Optimization of helical tomotherapy treatment plans for prostate cancer.

Helical tomotherapy (HT) is a novel treatment approach where the ring gantry irradiation geometry of a helical CT scanner is combined with an intensity-modulated megavoltage x-ray fan beam. An inverse treatment planning system (TomoTherapy Inc., Madison) was used to optimize the treatment plans for ten randomly selected prostate patients. Five different sets of margins (2, 5, 7.5 and 10 mm uniform 3D margins and a non-uniform margin of 5 to 10 mm) were employed for the prostate (GTV2) and seminal vesicles (GTV1). The dose distribution was evaluated in targets, rectum, bladder and femoral heads. HT plans are characterized by a rapid dose fall off around the target in all directions resulting in low doses (less than 30% of the dose at ICRU reference point) to the femurs in all cases. Up to a margin of 5 mm for target structures, it was always possible to satisfy the requirements for dose delivery set by RTOG protocol P-0126. Using a 'class solution', HT plans require minimal operator interaction and result in excellent sparing of normal structures in prostate radiotherapy.

Dose-Response Relationship, Radiation↗

Functional analysis of the structural basis of homophilic cadherin adhesion.

The structures of many cell surface adhesion proteins comprise multiple tandem repeats of structurally similar domains. In many cases, the functional significance of this architecture is unknown, and there are several cases in which evidence for individual domain involvement in adhesion has been contradictory. In particular, the extracellular region of the adhesion glycoprotein cadherin consists of five tandemly arranged domains. One proposed mechanism postulated that adhesion involves only trans interactions between the outermost domains. However, subsequent investigations have generated several competing models. Here we describe direct measurements of the distance-dependent interaction potentials between cadherin mutants lacking different domains. By quantifying both the absolute distances at which opposed cadherin fragments bind and the quantized changes in the interaction potentials that result from deletions of individual domains, we demonstrate that two domains participate in homophilic cadherin binding. This finding contrasts with the current view that cadherins bind via a single, unique site on the protein surface. The potentials that result from interactions involving multiple domains generate a novel, modular binding mechanism in which opposed cadherin ectodomains can adhere in any of three antiparallel alignments.

Binding Sites↗

Efficacy comparison of intravenous artelinate and artesunate in Plasmodium berghei-infected Sprague-Dawley rats.

This paper reports the comparative antimalarial efficacy of intravenous artelinate and artesunate in rats. Prior to efficacy experiments, a Plasmodium berghei-Sprague-Dawley rat model of malaria was developed, in which the clearance effects of intravenous drugs could be readily compared. In efficacy experiments, groups of P. berghei-infected rats were given 3 daily intravenous treatments of artelinate or artesunate at molar equivalent dose rates (total of 0-191.2 micromoles/kg). Artelinate was superior to artesunate in terms of clearance (100% clearance dose of 95.6 micromoles/kg (40 mg/kg) versus 191.2 micromoles/ kg for AS (73.4 mg/kg)) and parasite clearance time (1.7 +/- 0.5 days for AL versus 2.7 +/- 0.5 days for AS at a dose rate of 191.2 micromoles/kg, P < 0.01). No frank clinical toxicity was observed, though both artesunate and artelinate induced dose-related vascular necrosis at the site of injection. The necrosis was less severe and reversible when the drugs were administered via femoral, rather than tail/foot veins. The data suggest that the P. berghei-7-week-old Sprague-Dawley rat model of malaria is reproducible and useful for assessing the efficacy of antimalarials and that artelinate is at least as potent, and safe, as artesunate, the leading clinical treatment for severe malaria.

Animals↗

Facial anthropometry of Hong Kong Chinese babies.

OBJECTIVES: To provide a database of the craniofacial measurements of Chinese infants born in Hong Kong. DESIGN: Prospective cross-sectional study. SETTING AND SAMPLE POPULATION: A total of 2371 healthy singleton, born consecutively at the Prince of Wales Hospital and the Union Hospital from June 1998 to June 2000, were included in the study. The range of gestation was 33-42 weeks. MEASUREMENTS AND RESULTS: Measurements included facial width (FW), facial height (FH), nasal length (NL), nasal width (NW), and length of the philtrum (PhilL). The facial, nasal, nasofacial and nasozygomatic indices were derived. The data show generally higher values for males in the parameters measured. The various indices remained remarkably constant and did not vary significantly between the two genders or with gestation. When compared with previously published data for white people term babies, Chinese babies have similar NW but shorter philtrum length. CONCLUSION: The human face appears to grow in a remarkably constant fashion as defined by the various indices of facial proportions. This study establishes the first set of gestational age-specific standard of such craniofacial parameters for Chinese new-borns, potentially enabling early syndromal diagnosis. There are significant inter-racial differences in these craniofacial parameters.

Asian People↗

Craniofacial anthropometry of Hong Kong Chinese babies: the eye.

OBJECTIVES: To provide a database of the canthal measurements of Chinese infants born in Hong Kong. DESIGN: Prospective cross-sectional study. SETTING AND SAMPLE POPULATION: A total of 2,371 healthy singleton, born consecutively at the Prince of Wales Hospital and the Union Hospital from June 1998 to June 2000, were included in the study. The range of gestation was 33-42 weeks. MEASUREMENTS AND RESULTS: Canthal parameters were measured and included the outer canthal distance (OCD), intercanthal distance (ICD) and palpebral fissure length (PFL). The data generally show higher values for males in the parameters measured. The measurements were also compared with data published overseas. PFL and OCD were significantly larger in Hong Kong Chinese newborn babies, whereas ICD was smaller. CONCLUSION: This study establishes the first set of gestational age-specific standard of such craniofacial parameters for Chinese newborn babies, potentially enabling early syndromal diagnosis. There are significant inter-racial differences in these canthal parameters.

Algorithms↗

Evaluation of an education program for elementary school children with asthma.

To evaluate the effectiveness of a comprehensive asthma management education program for 7- to 12-year-old children with asthma, entitled Roaring Adventures of Puff (RAP), 18 elementary schools in Edmonton were randomized to intervention and control groups. Participating in the program were 76 students with asthma in the intervention schools and 86 in the control schools. Children in the intervention schools had statistically significant improvements in unscheduled doctor visits, missed school days, moderate-to-severe parent rating of severity, severity of shortness of breath, limitations in the kind of play, and correct use of medications. Unscheduled doctor visits and missed school days were the only significant improvements in the control group; however, improvements were about half that of the intervention group. The results showed that a comprehensive, school-based asthma education program is feasible and improves outcomes.

Adolescent↗

The effects of obesity on pulmonary function.

AIMS: (1) To determine the predominant pulmonary function abnormality in our population of obese children; and (2) to assess the correlation between the severity of lung function impairment and the degree of obesity as assessed by dual energy x ray absorptiometry (DEXA). METHODS: Sixty four obese patients underwent physical examination, standardised pulmonary function tests (spirometry, lung volumes, and single breath diffusion capacity for carbon monoxide), and DEXA scan measurements. The trunk and subtotal (total - head) body fat mass were used as surrogate index of body adiposity. RESULTS: Sixteen girls and 48 boys with median age and body mass index (BMI) of 12 years (interquartile range (IQR): 10-14) and 30.1 kg/m2 (IQR: 27.2-32.8) respectively were studied. None of the patients had clinical evidence of cardiopulmonary disease. Reduction in functional residual capacity (median FRC 93% predicted, IQR: 68.5-116.5%) and impairment of diffusion capacity (median DLco 83.5% predicted, IQR: 70.0-100.7%) were the most common abnormalities in our cohort, being observed in 30 (46%) and 21 (33%) patients respectively. Obstructive ventilatory impairment was found in three patients. There was significant negative correlation between the degree of reduction of FRC but not DLco with DEXA scan measurements, but such a relation was not found when BMI was used as the indicator of obesity. CONCLUSION: Reduction in FRC and diffusion impairment were the commonest abnormalities found in our cohort of obese patients. Reduction in static lung volume was correlated with the degree of obesity.

Absorptiometry, Photon↗

Proinflammatory and anti-inflammatory cytokine responses in preterm infants with systemic infections.

OBJECTIVE: A prospective study to investigate the pattern of proinflammatory and anti-inflammatory cytokine responses in preterm infants with systemic infection. METHODS: Very low birthweight infants in whom infection was suspected when they were > 72 hours of age were eligible. A full sepsis screen was performed in each episode. Key cytokines of both proinflammatory and anti-inflammatory pathways, including interleukin (IL) 2, IL4, IL5, IL6, IL10, interferon (IFN) gamma, and tumour necrosis factor (TNF) alpha, were measured at 0 (at the time of sepsis evaluation), 24, and 48 hours by flow cytometric analysis or immunoassay. RESULTS: Thirty seven of the 127 episodes of suspected clinical sepsis were proven infection or necrotising enterocolitis. Both proinflammatory (IL2, IL6, IFNgamma, TNFalpha) and anti-inflammatory (IL4, IL10) cytokines were significantly increased in infected infants compared with non-infected infants. Significant correlations were observed between IL6 and TNFalpha or IL10 as well as IL10 and IFNgamma in infected infants. In the subgroup analysis, plasma IL6, IL10, and TNFalpha concentrations, and IL10/TNFalpha and IL6/IL10 ratios were significantly elevated in patients with disseminated intravascular coagulation compared with infected infants without. The IL10/TNFalpha ratios had decreased significantly 48 hours after the onset, whereas the IL6/IL10 ratio showed only a non-significant decreasing trend. Further, the IL6/IL10 ratio in the deceased infant was disproportionally increased at presentation and continued to increase despite treatment. CONCLUSION: The results indicate that the counter-regulatory mechanism between the proinflammatory and anti-inflammatory cytokine pathways is probably operational in preterm infants of early gestation. High plasma IL6, IL10, and TNFalpha concentrations, and IL10/TNFalpha and IL6/IL10 ratios signify severe infection, but transiently elevated plasma IL10 concentration or IL10/TNFalpha ratio does not necessarily indicate a poor prognosis.

C-Reactive Protein↗

Updated gestational age specific birth weight, crown-heel length, and head circumference of Chinese newborns.

OBJECTIVE: To construct gestation specific standards of birth weight, crown-heel length, and head circumference of Chinese infants. DESIGN: A prospective cross sectional population study. METHODS: The birth weight, crown-heel length, and head circumference were prospectively measured using standard equipment in newborns delivered at 24-42 weeks gestation in the maternity units of 10 public hospitals and two private hospitals in Hong Kong. The findings were used to construct gestation specific standards of these variables. The LMS method using maximum penalised likelihood was used to perform model fitting. The results were compared with those obtained from a cohort of infants born in the same locality between 1982 and 1986. RESULTS: From October 1998 to September 2000, a total of 10 032 infants were measured, representing 9.6% of the total deliveries in Hong Kong during that period. An extra 307 infants with gestation < or = 35 weeks were recruited from October 2000 to June 2001. Each of the three variables showed a normal distribution at each gestational week. Gestation specific reference standards for each variable were constructed for male and female infants separately. Comparison with the 1982-1986 cohort showed a significant secular trend to increased birth weight. The trend was small, but significant, for crown-heel length and head circumference. CONCLUSION: These growth standards will provide useful references for the care of newborns of ethnic Chinese origin. These standards, especially that for birth weight, should be updated regularly.

Birth Weight↗