Biomedical subjects

Jianrong Wu

Publications and source records attributed to Jianrong Wu.

4 recordsLinked to original sources

PubMed2004

Saturation modified point spread functions in two-photon microscopy.

Excitation saturation can dramatically alter the effective imaging point spread function (PSF) in two-photon fluorescence microscopy. The saturation-modified PSF can have important implications for resolution in fluorescence imaging as saturation leads to both an increased fluorescence observation volume and an altered spatial profile for the PSF. We introduce here a computational approach to accurately quantify molecular excitation profiles that represent the modified imaging PSF in two-photon microscopy under the influence of excitation saturation. An analytical model that accounts for pulsed laser excitation is developed to calculate the influence of saturation at any location within the excitation laser profile. The overall saturation modified molecular excitation profiles are then evaluated numerically. Our results demonstrate that saturation can play an important role in two-photon fluorescence microscopy even with relatively modest excitation levels.

Fluorescent Dyes↗

PubMed2004

Second neoplasms in pediatric patients with primary central nervous system tumors: the St. Jude Children's Research Hospital experience.

BACKGROUND: Details on second neoplasms (SNs) following pediatric central nervous system (CNS) tumors are scant, because of the rarity of such SNs. The goal of the current study was to investigate and characterize these rare SNs. METHODS: The authors reviewed clinical and treatment data on all institutional patients age < 22 years at diagnosis of a primary CNS tumor who developed any type of SN. Patients with neurofibromatosis type 1 were excluded. Cumulative incidence rates were estimated, and putative risk factors were analyzed. RESULTS: The SNs investigated in the current study included 10 gliomas (42%), 5 meningiomas (21%), 2 desmoid tumors, 2 myelodysplastic syndromes, 2 basal cell carcinomas, 1 leukemia, 1 malignant fibrous histiocytoma, and 1 thyroid carcinoma. Twenty-one patients had previously received radiotherapy, and 12 patients had received chemotherapy. The SN was related to a genetic cause in 7 patients (29%). Eleven patients died of their SNs, including 8 patients with glioma and 2 patients with myelodysplastic syndromes. The estimated 15-year cumulative incidence rate for malignant SNs was 4%. Children with choroid plexus tumors had an estimated 10-year cumulative incidence rate of 20.2%; 2 of those patients had germline TP53 mutations. Age </= 2 years was a significant risk factor (P = 0.016) for development of an SN only when patients with genetic conditions were included in the analysis. No significant difference in the estimated cumulative incidence of SNs was found among patients who had received different types of therapy. CONCLUSIONS: The risk of lethal SNs after pediatric CNS tumors is small. Young patients and patients with choroid plexus tumors appear to have an increased risk of SNs that is associated with genetic factors.

Adolescent↗

PubMed2003

Likelihood-based confidence intervals for a log-normal mean.

To construct a confidence interval for the mean of a log-normal distribution in small samples, we propose likelihood-based approaches - the signed log-likelihood ratio and modified signed log-likelihood ratio methods. Extensive Monte Carlo simulation results show the advantages of the modified signed log-likelihood ratio method over the signed log-likelihood ratio method and other methods. In particular, the modified signed log-likelihood ratio method produces a confidence interval with a nearly exact coverage probability and highly accurate and symmetric error probabilities even for extremely small sample sizes. We then apply the methods to two sets of real-life data.

Biomedical Research↗

PubMed2002

Likelihood analysis for the ratio of means of two independent log-normal distributions.

Existing methods for comparing the means of two independent skewed log-normal distributions do not perform well in a range of small-sample settings such as a small-sample bioavailability study. In this article, we propose two likelihood-based approaches-the signed log-likelihood ratio statistic and modified signed log-likelihood ratio statistic-for inference about the ratio of means of two independent log-normal distributions. More specifically, we focus on obtaining p-values for testing the equality of means and also constructing confidence intervals for the ratio of means. The performance of the proposed methods is assessed through simulation studies that show that the modified signed log-likelihood ratio statistic is nearly an exact approach even for very small samples. The methods are also applied to two real-life examples.

Biological Availability↗