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Biomedical subjects

S H Lai

Publications and source records attributed to S H Lai.

At least 19 recordsLinked to original sources
PubMed2001

Fatal retroperitoneal haemorrhage: an unusual complication of percutaneous endoscopic gastrostomy.

A 93-year-old lady with dementia, neurological dysphagia and aspiration pneumonia, died from massive retroperitoneal haemorrhage which developed as a rare and, it is believed, hitherto unreported, complication of percutaneous endoscopic gastrostomy (PEG), which was performed for feeding purposes. It is postulated that the initial, unsuccessful attempt at needle puncture of the stomach, under endoscopic guidance, had resulted in iatrogenic perforation and laceration of the splenic and superior mesenteric veins close to their confluence with the portal vein. It would also appear that dense fibrous adhesions between the pyloro-antral region of the stomach and the posterior hepatic surface had altered the immediate anatomical relations of the stomach in such a manner as to have predisposed to these events.

Aged↗
PubMed2001

Ossifying lipoma of the hand: a case report.

INTRODUCTION: Ossifying lipoma is an uncommon tumour and its occurrence in the hand is rare. It is often not diagnosed preoperatively. CLINICAL PICTURE: Our case presented with a lump in the hand which was painful with activity. The lipomatous component of the tumour was radiologically not distinguishable. TREATMENT: The hand was explored through a wide palmar incision, revealing a lipomatous tumour. The tumour was completely excised and diagnosis made after histological examination. OUTCOME: After 1 year, the patient has had normal function of the hand with no tumour recurrence. DISCUSSION: The diagnosis of ossifying lipoma could be made with certainty only after radiological examination, excision and histological examination. The bony component is of mesenchymal origin and may come about as a result of metaplastic transformation.

Adult↗
PubMed2000

Non-infectious epiglottitis in children: two cases report.

Two young children who suffered from thermal injuries to the epiglottis after swallowing corrosive agent and hot water respectively. Findings, clinically and radiologically, in both children were similar to acute infectious epiglottitis. Both recovered quickly with close observation and parenteral antibiotics. Although Haemophilus influenzae type b (Hib) is the major pathogen of epiglottitis, in areas with low incidence of Hib infection and high vaccination rates, non-infectious epiglottic swelling should be considered first.

Burns↗
PubMed2000

A hierarchical neural network algorithm for robust and automatic windowing of MR images.

A novel hierarchical neural network based algorithm for automatic adjustment of display window width and center for a wide range of magnetic resonance (MR) images is presented in this paper. The algorithm consists of a feature generator utilizing both wavelet histogram and compact spatial statistical information computed from a MR image, a competitive layer based neural network for clustering MR images into different subclasses, two pairs of a radial basis function (RBF) network and a bi-modal linear estimator for each subclass, as well as a data fusion process using estimates from both estimators to compute the final display parameters. Both estimators can adapt to new kinds of MR images simply by training them with those images, which make the algorithm adaptive and extendable. The RBF based estimator performs very well for images that are similar to those in the training data set. The bi-modal linear estimator provides reasonable estimations for a wide range of images that may not be included in the training data set. The data fusion step makes the final estimation of the display parameters accurate for trained images and robust for the unknown images. The algorithm has been tested on a wide range of MR images and has shown satisfactory results.

Algorithms↗
PubMed2000

Effect of carbon dioxide tension in the first three days of life on the development of retinopathy of prematurity.

BACKGROUND: This study focuses on the effect of carbon dioxide tension in the first 3 days of life on the development of retinopathy of prematurity (ROP) in mechanically ventilated premature infants. METHODS: From January 1997 to June 1998, 91 premature infants (gestational age 28.8 +/- 2.5 weeks, birth weight 1169 +/- 385 g) born in Chung Gung Children's Hospital requiring mechanical ventilation in the first 72 hours were enrolled in our study. Ophthalmic examination was performed initially at 4-6 weeks of age and then every week if ROP was found and every other week if the result was normal until discharge. These infants were divided into 2 groups: those with and without ROP. Medical records of the highest and lowest blood gas measurements were recorded during the first 3 days of life. To screen for possible risk factors related to the development of ROP within these 2 groups, variables comprising perinatal data were compared. RESULTS: The perinatal factors were compared, whish showed that infants with ROP had a lower mean gestational age (p < 0.001), mean birth body weight (p < 0.001), and a longer duration under mechanical ventilation (p < 0.001). The severity and incidence of ROP were not affected by either hypercapnia or hypocapnia; even with the superimposed effect of hyperoxia, the effect was minimal. CONCLUSION: Hypercarbia or hypocarbia in the first 3 days of mechanically ventilated preterm neonates does not affect the subsequent development of retinopathy of prematurity. However, a lower gestational age and birth weight as well as longer-duration mechanical ventilation might be independent predictors for the occurrence of ROP. The role of PaCO2 in the pathophysiology of retinopathy of prematurity remains undetermined, and further investigation in the future is warranted.

Carbon Dioxide↗
PubMed1999

A novel local PCA-based method for detecting activation signals in fMRI.

A novel local principal component analysis (LPCA) technique is presented for activation signal detection in functional magnetic resonance imaging (fMRI) without explicit knowledge about the shape of the model activation signal. Unlike the traditional PCA methods, our LPCA algorithm is based on a measure of separation between two clusters formed by the signal segments in active periods and inactive periods, which is computed in an eigen-subspace. In addition, we only applied PCA to the temporal sequence of each individual voxel instead of applying PCA to the fMRI data set. In our algorithm, we first applied a linear regression procedure to alleviate the baseline drift artifact. Then, the baseline-corrected temporal signals were partitioned into active and inactive segments according to the paradigm used for the fMRI data acquisition. Principal components were computed from all these segments for each voxel by PCA. By projecting the segments of each voxel onto a linear subspace formed by the corresponding most dominant principal components, two separate clusters were formed from active and inactive segments. An activation measure was defined based on the degree of separation between these two clusters in the projection space. We show experimental results on the activation signal detection from various sets of fMRI data with different types of stimulation by using the proposed LPCA algorithm and the standard t-test method for comparison. Our experiments indicate that the LPCA algorithm in general provides substantial signal-to-noise ratio improvement over the t-test method.

Algorithms↗
PubMed1999

A new variational shape-from-orientation approach to correcting intensity inhomogeneities in magnetic resonance images.

A new intensity inhomogeneity correction algorithm based on a variational shape-from-orientation formulation is presented. Unlike most previous methods, the proposed algorithm is fully automatic, widely applicable and very efficient. Since no prior classification knowledge about the image is assumed in the proposed algorithm, it can be applied to correct intensity inhomogeneities for a wide variety of medical images. In this paper, a finite-element method is used to model the smooth bias-field function. Orientation constraints for the bias-field function are computed at the nodal locations of the regular discretization grid away from the boundary between different class regions. The selection of reliable orientation constraints is facilitated by the goodness of fit of a first-order polynomial model to the neighborhood of each nodal location. The automatically selected orientation constraints are integrated in a regularization framework, which leads to minimization of a convex and quadratic energy function. This energy minimization is accomplished by solving a linear system with a large, sparse, symmetric and positive semi-definite stiffness matrix. We employ an adaptive preconditioned conjugate-gradient algorithm to solve the linear system very efficiently. Experimental results on a variety of magnetic resonance images are given to demonstrate the effectiveness and efficiency of the proposed algorithm.

Algorithms↗
PubMed1997

Fast numerical algorithms for fitting multiresolution hybrid shape models to brain MRI.

In this paper, we present new and fast numerical algorithms for shape recovery from brain MRI using multiresolution hybrid shape models. In this modeling framework, shapes are represented by a core rigid shape characterized by a superquadric function and a superimposed displacement function which is characterized by a membrane spline discretized using the finite-element method. Fitting the model to brain MRI data is cast as an energy minimization problem which is solved numerically. We present three new computational methods for model fitting to data. These methods involve novel mathematical derivations that lead to efficient numerical solutions of the model fitting problem. The first method involves using the nonlinear conjugate gradient technique with a diagonal Hessian preconditioner. The second method involves the nonlinear conjugate gradient in the outer loop for solving global parameters of the model and a preconditioned conjugate gradient scheme for solving the local parameters of the model. The third method involves the nonlinear conjugate gradient in the outer loop for solving the global parameters and a combination of the Schur complement formula and the alternating direction-implicit method for solving the local parameters of the model. We demonstrate the efficiency of our model fitting methods via experiments on several MR brain scans.

Algorithms↗
PubMed1995

Human breast sarcoma and human breast implantation: a time trend analysis based on SEER data (1973-1990).

Since the demonstration in the 1940s of foreign body induction of sarcomas in rodents, the safety of artificial implants in humans has been a matter of concern. In this study, we assess the risk for the development of breast sarcomas in women with silicone breast implants. Our analysis is based on the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program database for the years 1973-1990 and on estimates of breast implantation rates from about 1960 onward. We have divided the SEER data into two equal time periods, 1972-1981 and 1982-1990. For each time period, we estimated the average annual number of women in the United States who had received breast implants 10 or more years earlier. This analysis allows for a 10 year latency period for the induction of breast sarcoma. We calculated that the average number of women in the U.S. 10 or more years post breast implantation was 55,000 for the 1973-1981 period and 509,000 for the 1982-1990 period. We then examined the SEER data to observe whether there was a concomitant rise in the female breast sarcoma incidence rates between these two time periods. We found the mean age-adjusted incidence rate of breast sarcomas was 0.13 per 100,000 women for the initial 9-year period, 1973-1981, and 0.12 per 100,000 women for the latter 9-year period, 1981-1990.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Combination therapy with zidovudine and dideoxycytidine in patients with advanced human immunodeficiency virus infection. A phase I/II study.

OBJECTIVE: To evaluate the safety and immunologic and antiviral effects of combination therapy with zidovudine and dideoxycytidine (ddC) in patients with advanced human immunodeficiency virus type 1 (HIV) infection. DESIGN: A phase I/II open-label, dose-ranging study. SETTING: Two AIDS Clinical Trials Group units. PATIENTS: Patients (56) with advanced HIV disease. INTERVENTIONS: Patients were randomly assigned to one of three paired regimens of zidovudine and ddC. We evaluated six dosing regimens, each involving oral administration of the study drugs at 8-hour intervals. MEASUREMENTS: Pharmacokinetics, toxicity, CD4 counts, p24 antigenemia and clinical end points. MAIN RESULTS: The median follow-up period was 40.6 weeks (range, 0.3 to 70 weeks). Neither drug affected the pharmacokinetic profile of the other. Episodes of serious hematologic toxicity were infrequent, occurring in only 17.9% of patients, and did not differ among the regimens (P = 0.15). Severe sensory peripheral neuropathy occurred in two patients (one patient each in regimens 1 and 4). One patient receiving regimen 4 died. The mean maximal increase in CD4 counts exceeded 109 cells/mm3, and 69% of patients receiving combinations containing 300 or 600 mg of zidovudine daily had an increase in CD4 counts of 50 cells/mm3 or greater. Regimens containing 600 mg of zidovudine daily (regimens 2 and 5) were also more likely to result in persistent increases in CD4 counts above pretreatment values than were the two lowest dose regimens (P = 0.003). The decline in CD4 counts was more rapid, and the suppression of the p24 antigenemia was less rapid and less sustained in patients receiving the lowest zidovudine dose alone (regimen 6). The addition of ddC to regimen 6 (regimen 3) resulted in a slower decline in the CD4 counts (P = 0.06). CONCLUSIONS: Combination therapy with zidovudine and ddC at the doses tested was well tolerated and did not result in toxicity. A daily oral dose of 150 mg of zidovudine appeared to produce a suboptimal effect on p24 antigenemia and CD4 counts. Combination therapy with ddC and higher doses of zidovudine produced greater and more persistent effects in patients with advanced HIV infection compared with other study regimens and with the results of previous trials of zidovudine monotherapy.

Adult↗
PubMed1992

Quantitative analysis of human immunodeficiency virus type 1 antibody reactivity by western immunoblots: evaluation of relative antibody levels in seropositive individuals and mothers.

A quantitative analysis of antibody responses to human immunodeficiency virus type 1 (HIV-1) proteins using Western immunoblots and 125I-labeled protein A is reproducible and can be validated. The antibody levels obtained by Western immunoblots were compared with stoichiometric p24 radioimmunoassay over a wide range of antibody (correlation coefficient, .94; P less than .001). Antibody levels to gp160 and gp120 were validated using purified antigens. Analysis of antibody levels from 31 seropositive individuals revealed a statistically significant correlation between antibody levels to p24 and the other viral proteins except gp120. Anti-gag p24 antibody was strongly correlated with antibodies to other env products, specifically gp41 and gp160. Using the validated assay, HIV-1-infected mothers of infants were found to have highly variable levels of antibody to all viral proteins. Mothers of infected infants did not differ significantly from mothers of uninfected infants in antibody pattern or levels to any viral protein including gp120.

Adult↗
PubMed1991

A hospital-based prospective study of perinatal infection with human immunodeficiency virus type 1.

Most infants with pediatric acquired immunodeficiency syndrome and infections with human immunodeficiency virus type 1 (HIV-1) are infected perinatally by their mothers. To determine the proportion of exposed infants who are infected, we conducted a hospital-based prospective study in HIV-1-infected women whose infants were delivered at a single metropolitan hospital in Miami, Fla. A population of uninfected women and their infants was also enrolled and followed longitudinally for 2 years to assess laboratory and clinical measurements. The median follow-up is now 18 months for 82 infants born to HIV-1-infected mothers. The proportion of infected infants in this group is 0.30 (25/82). None of the infants born to 110 HIV-1-seronegative mothers were seropositive. Infected infants were easily distinguished from noninfected infants by virus isolation. No single immunologic or hematologic measure was predictive of infection for all infants at risk for HIV-1 infection who were 6 months of age or younger. As a group, however, infected infants could be distinguished from uninfected index infants by a number of immunologic measures by 6 months of age; the absolute number of CD4+ lymphocytes and the CD4+/CD8+ lymphocyte ratio were the variables most predictive of infection. As in retrospective studies, clinical disease developed in 80% of infected infants within the first 24 months of life. This study provides documentation of HIV-1 perinatal transmission risk and early correlates of infection in young infants from a single hospital.

Acquired Immunodeficiency Syndrome↗
PubMed1991

The donation and sale of blood by intravenous drug users.

In spite of efforts to dissuade intravenous drug users (IVDUs) from donating or selling blood, some continue to do so. As part of a longitudinal study, 915 IVDUs in South Florida were interviewed concerning their history of donation or sale of blood and tested for antibodies to HIV-1 and HTLV-I/II. Approximately 17 percent had either donated or sold blood during 1985 through 1988; most contributors (80.4 percent) sold to commercial blood services. IVDUs who had donated/sold blood were more likely to be male and not in drug treatment than were those who had not contributed blood. IVDUs not in treatment at the time of interview were more likely than IVDUs in treatment to have sold blood. Of those who had donated/sold blood since 1985, 19.6 percent subsequently tested positive for antibodies to HIV-1 and 5.7 percent were positive for antibodies to HTLV-I/II. Increased effort is required to screen prospective donors and sellers, particularly at commercial blood banks.

Adult↗
PubMed1990

HTLV-I/II seropositivity and death from AIDS among HIV-1 seropositive intravenous drug users.

In a prospective study of street-recruited intravenous drug users (IVDUs) in Miami, Florida, USA, 107 (46.5%) of 230 IVDUs were infected with HIV-1. Of these HIV-1 seropositive individuals, 23 were also infected with human T-lymphotropic virus type I or II (HTLV-I/II). To test the hypothesis that HTLV-I/II infection has an effect on the survival of HIV-1 seropositive IVDUs, various baseline clinical and laboratory HIV-1 related indices in HTLV-I/II positive and negative groups were compared. Life table analysis and Cox's proportional hazards model were used to estimate the potential effect of HTLV-I/II infection on the survival patterns of people infected with HIV-1. IVDUs infected with both viruses were three times more likely to die from AIDS during follow-up than were those infected with HIV-1 only. This finding suggests that HTLV-I/II seropositivity may adversely affect the clinical outcome of HIV-1 seropositive patients.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Urinary electrolytes and blood pressure in three Yi farmer populations, China.

The relation between blood pressure and urinary electrolytes, including sodium, potassium, calcium, and magnesium were examined in male farmers of the Yi nationality who live in three separate communities in Sichuan and Yunnan provinces in China, where the lifestyles, habits, and living conditions are very different. One of these three communities was unacculturated and had the lowest average blood pressure as well as the lowest prevalence rate of hypertension in China; one was acculturated and had the highest average blood pressure; and the third was moderately acculturated with its average blood pressure between the other two. Blood pressure was taken on each of 3 days and corresponding 24-hour urine specimens were collected to measure potassium, sodium, calcium, magnesium, urea nitrogen, and creatinine. Ecological and individual-based data correlation analyses were employed to study the relations among age, body mass index, some related indexes of electrolyte derivatives, and blood pressure. Multiple regression analyses were used to explore the relation of blood pressure to the above indexes, adjusted for age, body mass index, urea nitrogen and creatinine, and geographical differences. Statistically significant correlation analyses showed that systolic blood pressure was positively associated with sodium-creatinine, calcium-creatinine, sodium-potassium, calcium-magnesium, and urea nitrogen and creatinine ratios; negatively associated with potassium-creatinine and magnesium-creatinine ratios. The ridge regression analysis selected only calcium-magnesium ratio as a predictor of systolic blood pressure.

Adult↗
PubMed1988

Oral contraceptives and premenopausal breast cancer in nulliparous women.

Characteristics of women with potential for modifying the relationship between use of oral contraceptives (OCs) and the risk of premenopausal breast cancer were investigated using data from the Cancer and Steroid Hormone study, a population-based, case-control study conducted in eight geographic areas of the United States. Cases consisted of 2945 women who were premenopausal and 20-54 years of age when breast cancer was diagnosed between December 1, 1980, and December 31, 1982; controls consisted of 2646 women with no history of breast cancer who were also premenopausal and 20-54 years of age when selected during the same period. Results are presented with the cases and controls divided into eight groups on the basis of age at diagnosis on selection (20-44, 45-54), parity (0, greater than or equal to 1), and age at menarche (less than 13, greater than or equal to 13). Among nulliparous women who experienced menarche before age 13, the relative risk of developing breast cancer in the age interval 20-44 years is estimated to be 1.0 for never-users of OCs (reference), 1.3 for greater than 0-3 years of use (95% confidence intervals 0.7-2.4), 1.3 for 4-7 years (95% CI 0.7-2.6), 2.7 for 8-11 years (95% CI 1.2-6.3), and 11.8 for 12 years or longer (95% CI 1.4-95.7). OC use is not significantly related to the risk of breast cancer among women in any of the other seven groups. These findings suggest that prolonged OC use may accelerate the onset of breast cancer for a small group of susceptible women while having no appreciable impact on overall risk. The findings should be regarded as tentative, however, since they are based upon numerous comparisons and because age of menarche was stratified at 13 years to highlight the concentration of breast cancer risk apparent in our data.

Adult↗
PubMed1987

Breast cancer risk in relation to type of estrogen contained in oral contraceptives.

We report analyses designed to address the recent hypothesis that women who use combination-type OCs containing ethinylestradiol (EE) are at increased risk of breast cancer before age 45, if use of such OCs occurs prior to first term pregnancy (FTP). Our findings, based on data from 1679 cases and 1689 controls, 20-44 years of age, from the population-based Cancer and Steroid Hormone Study, are against the hypothesis. The relative risk of breast cancer by duration of exclusive use prior to FTP of OCs containing EE is estimated to be 1.0 (1-12 months EE use), 1.2 (13-48 months EE use), and 0.9 (49+ months EE use). There was no evidence of a latent effect. Among parous women with 49+ months exclusive use prior to FTP of EE-containing OCs, the relative risk of breast cancer was estimated as 0.9 (0-4 years after FTP) and 0.6 (5-9 years after FTP). Among nulliparous women with 49+ months exclusive use of EE-containing OCs, the relative risk of breast cancer was estimated as 1.0 (0-4 years since first use), 0.7 (5-9 years since first use), and 1.1 (10-14 years since first use). With regard to exclusive use of OCs containing mestranol, parous women who used such preparations long-term before their FTP showed no alteration of breast cancer risk, even 15 years or more after pregnancy. Nulliparous women with exclusive use of ME-containing OCs did show elevations in breast cancer risk, but the magnitude of risk in relation to duration of use and latent interval shows no pattern that suggests a cause-effect relationship.

Adult↗