Development, characterization, and application of a charged particle microbeam for radiobiological research

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005."September 2005."Includes bibliographical references (leaves 194-197).The goal of this work is to develop a charged-particle microbeam for use in radiobiological research at the MIT Laboratory for Accelerator Beam Applications (LABA). The purpose of this device is to precisely explore the radiation response of biological systems on a cellular and subcellular level, particularly in the area of temporal and spatial effects of radiation on in vitro systems. An accelerator-based 750 keV proton source was characterized and integrated into a laboratory-scale device that includes a deflection/gating system, single-particle detection system, imaging and positioning system, and a collimation system with two designed modes: a "charged-particle microslit" for delivering a -3 micron by 1 mm dose profile; and a pinhole aperture for delivering a -3 micron diameter pattern of radiation. The entire device measures less than 4 m, requires minimal radiation shielding, and utilizes a dedicated ion source. The charged particle microslit has been fully characterized and used to deliver a radiation pattern to a series of mammalian fibroblast cell monolayers that have subsequently been assayed for direct and indirect chemical effects of radiation, double-stranded DNA damage, and DNA repair protein localization. These studies will contribute to the understanding of the radiation-induced bystander effect, which is generally defined as the induction of biological effects in cells that are not directly traversed by ionizing radiation.(cont.) Analysis of the range of assays performed on the microbeam-irradiated cells demonstrates that even though the physical radiation dose is confined to a subnuclear width ( 40 microns) and show dependence on the initial radiation dose delivered to the directly irradiated cells. As an experimental system, the LABA Microbeam was designed to be practically turn-key, and most applications require only one operator to perform. The LABA Microbeam represents a significant step towards a cost-effective and easily operated charged-particle microbeam appropriate for use as a standard laboratory research tool. Further work remains in automation of the microbeam subsystems and optimization/characterization of the pinhole-aperture collimator, as well as expanding the scope of the radiobiological assays performed using the charged-particle microslit.by Michael R. Folkert.Ph.D

Monte Carlo simulation of neutron shielding for proton therapy facilities

Thesis (S.B. and S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998.Includes bibliographical references (leaves 60-63).A study was performed to develop a Monte Carlo method of modeling neutron shielding of proton therapy facilities in a complex, realistic environment. The bulk neutron shielding of the Northeast Proton Therapy Center (Massachusetts General Hospital, Boston, MA) was used as the basis of the design work. A geometrical model of the facility was simulated using the LAHET Code System, a set of Monte Carlo codes developed at Los Alamos National Laboratory. Additional software tools for reading and analyzing the simulation data that the model provides have been developed and tested. In order to verify the computer simulations, neutron detection and data acquisition systems have been assembled, modified, and thoroughly tested in order to monitor the neutron dose equivalent during proton beam operation at several locations on a continuous basis. Preliminary tests show that the geometry and physics models proposed in this work are valid.by Michael R. Folkert.S.B.and S.M

Dose-Intensified Stereotactic Ablative Radiation for Localized Prostate Cancer

Purpose: Stereotactic ablative radiation (SAbR) has been increasingly used in prostate cancer (PCa) given its convenience and cost efficacy. Optimal doses remain poorly defined with limited prospective comparative trials and long-term safety/efficacy data at higher dose levels. We analyzed toxicity and outcomes for SAbR in men with localized PCa at escalated 45 Gy in 5 fractions. Methods and Materials: This study retrospectively analyzed men from 2015 to 2019 with PCa who received linear-accelerator-based SAbR to 45 Gy in 5 fractions, along with perirectal hydrogel spacer, fiducial placement, and MRI-based planning. Disease control outcomes were calculated from end of treatment. Minimally important difference (MID) assessing patient-reported quality of life was defined as greater than a one-half standard deviation increase in American Urological Association (AUA) symptom score after SAbR. Results: Two-hundred and forty-nine (249) low-, intermediate-, and high-risk PCa patients with median follow-up of 14.9 months for clinical toxicity were included. Acute urinary grade II toxicity occurred in 20.4% of patients. Acute grade II GI toxicity occurred in 7.3% of patients. For follow-up \u3e 2 years (n = 69), late GU and GI grade ≥III toxicity occurred in 5.8% and 1.5% of patients, respectively. MID was evident in 31.8%, 23.4%, 35.8%, 37.0%, 33.3%, and 26.7% of patients at 3, 6, 12, 24, 36, and 48 months, respectively. The median follow-up for biochemical recurrence was 22.6 months with biochemical failure-free survival of 100% at 1 year (n = 226) and 98.7% for years 2 (n = 113) and 3 (n = 54). Conclusions: SAbR for PCa at 45 Gy in 5 fractions shows an encouraging safety profile. Prospective studies with longer follow-up are warranted to establish this dose regimen as standard of care for PCa

Comparison of HPV DNA testing in cervical exfoliated cells and tissue biopsies among HIV-positive women in Kenya

HIV-positive women are infected with human papillomavirus (HPV) (especially with multiple types), and develop cervical intraepithelial neoplasia (CIN) and cervical cancer more frequently than HIV-negative women. We compared HPV DNA prevalence obtained using a GP5+/6+ PCR assay in cervical exfoliated cells to that in biopsies among 468 HIV-positive women from Nairobi, Kenya. HPV prevalence was higher in cells than biopsies and the difference was greatest in 94 women with a combination normal cytology/normal biopsy (prevalence ratio, PR = 3.7; 95% confidence interval, CI: 2.4-5.7). PR diminished with the increase in lesion severity (PR in 58 women with high-grade squamous intraepithelial lesions (HSIL)/CIN2-3 = 1.1; 95% CI: 1.0-1.2). When HPV-positive, cells contained 2.0- to 4.6-fold more multiple infections than biopsies. Complete or partial agreement between cells and biopsies in the detection of individual HPV types was found in 91% of double HPV-positive pairs. The attribution of CIN2/3 to HPV16 and/or 18 would decrease from 37.6%, when the presence of these types in either cells or biopsies was counted, to 20.2% when it was based on the presence of HPV16 and/or 18 (and no other types) in biopsies. In conclusion, testing HPV on biopsies instead of cells results in decreased detection but not elimination of multiple infections in HIV-positive women. The proportion of CIN2/3 attributable to HPV16 and/or 18 among HIV-positive women, which already appeared to be lower than that in HIV-negative, would then further decrease. The meaning of HPV detection in cells and random biopsy from HIV-positive women with no cervical abnormalities remains unclear. What\u27s new? Assignment of human papillomavirus (HPV) types to individual cervical lesions is essential for the understanding of the biology of different HPV types, efficacy of HPV vaccines, and design of detection assays. Such attribution is however hampered in HIV-positive women by the high proportion of multiple HPV infections. This study is the first to systematically compare HPV detection in paired cervical exfoliated cells and cervical tissue biopsies. HPV testing using biopsies instead of cells results in decreased detection of multiple infections in HIV-positive women. Exclusive reliance on biopsies also decreased the proportion of CIN2/3 attributable to vaccine-preventable HPV16 and/or 18 infection

Common genetic variants improve risk stratification after the atrial switch operation for transposition of the great arteries

Background: Clinical factors are used to estimate late complication risk in adults after atrial switch operation (AtrSO) for transposition of the great arteries (TGA), but heterogeneity in clinical course remains. We studied whether common genetic variants are associated with outcome and add value to a clinical risk score in TGA-AtrSO patients. Methods and results: This multicenter study followed 133 TGA-AtrSO patients (aged 28 [IQR 24–35] years) for 13 (IQR 9–16) years and examined the association of genome-wide single-nucleotide polymorphisms (SNPs) with a composite endpoint of symptomatic ventricular arrhythmia, heart failure hospitalization, ventricular assist device implantation, heart transplantation, or mortality. Thirty-two patients (24%) reached the endpoint. The genome-wide association study yielded one genome-wide significant (p 20%) risk. Stratified by the combined score, observed 5-year event-free survival was 100%, 79% and 31% for low, intermediate, and high-risk patients, respectively. Conclusions: Common genetic variants may explain some variation in the clinical course in TGA-AtrSO and improve risk stratification over clinical factors alone, especially in patients at intermediate clinical risk. These findings support the hypothesis that including genetic variants in risk assessment may be beneficial

Структурно-семантичний аналіз еврісемантів української мови (на матеріалі лексико-семантичного поля "річ")

В статье рассматриваются лексико-семантические особенности эврисемантов в украинском языке, осуществляется их семантическая классификация, методом компонентного анализа проводится структурный анализ. Представлен фрагмент иерархично упорядоченной парадигмы широкозначных имен существительных, состоящий из ЛСГ "Предмет" и "Дело".У статті розглядаються лексико-семантичні особливості еврісемантів української мови, здійснюється їх семантична класифікація, за допомогою компонентного аналізу проводиться структурний аналіз. Подається фрагмент ієрархічно впорядкованої парадигми широкозначних іменників, представлений ЛСГ "Предмет" та "Справа".In this article lexica-semantic peculiarities of everysemantical nouns in Ukrainian are considered. It was made semantic distinguishing and structural analysis of those elements. The everysemants of a lexica-semantic field "Thing", represented by two groups "Subject" and "Work", are disposed in specific hierarchy

Haploinsufficiency of CYP8B1 associates with increased insulin sensitivity in humans

10.1172/JCI152961The Journal of clinical investigation13221e152961

Genetic association study of QT interval highlights role for calcium signaling pathways in myocardial repolarization.

The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal mendelian long-QT syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals, we identified 35 common variant loci associated with QT interval that collectively explain ∼8-10% of QT-interval variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 new QT interval-associated loci in 298 unrelated probands with LQTS identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies new candidate genes for ventricular arrhythmias, LQTS and SCD