SciFi detector and associated method for real-time determination of profile and output factor for small fields in stereotactic radiotherapy

PURPOSE

For determining small-field profile and output factor during stereotactic radiotherapy quality assurance (QA) procedures, we propose a novel system based on the scintillating fiber (SciFi) detector with output image acquisition and processing to allow real-time monitoring of profile and output factor.

MATERIALS AND METHODS

The employed detector is a SciFi detector made of tissue-equivalent scintillating plastic fibers arranged in 6-layer fiber ribbons with a fiber pitch of 275 μm in each layer. The scintillating signal at the detector output is acquired by a sCMOS (scientific complementary metal-oxide-semiconductor) camera and represents the projected field profile along the fibers axis. An iterative reconstruction method of the field from its projected profile based on a priori knowledge of some features of the radiation field defined by the stereotactic cones is suggested. The detector with implemented data processing has been tested in clinical conditions, for determining beam profiles and output factors, using cone collimators of different sizes from 4 to 15 mm diameter. The detector under test was placed at 1.4 cm depth and 98.6 cm source to surface distance (SSD) in a water-equivalent phantom and irradiated by a 6 MV photon beam.

RESULTS

The reconstructed field profiles obtained from the detector are coherent with data from EBT3 radiochromic films, with differences within ±0.32 mm for both the FWHM and the penumbra region. For real-time determination of the field output factor, the measured data are also in good agreement with data independently determined by the French Institute for Radiological Protection and Nuclear Safety (IRSN) based on radiochromic films and thermoluminescent 1 × 1 mm2 micro-cubes dosimeters (TLD). The differences are within ±1.6% for all the tested cone sizes.

CONCLUSIONS

We propose and have tested a SciFi plastic scintillating detector with an optimized signal processing method to characterize small fields defined by cone collimators. It allows the determination of key field parameters such as full width at half maximum (FWHM) and field output factors. The results are consistent with those independently measured using TLD and radiochromic films. As the SciFi detector does not require a correction factor, it is in line with the International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) TRS-483 recommendations, and can be suitable for online QA of small radiation fields used in photon beam radiotherapy, and is compatible with MRI-LINAC.

Lack of association between human leukocyte antigen polymorphisms rs9277535 and rs7453920 and chronic hepatitis B in a Brazilian population

Hepatitis B virus (HBV) infection is a serious public health problem worldwide. The progression of the disease depends on several host and viral factors and may result in fulminant hepatitis (very rare), acute hepatitis with spontaneous clearance, and chronic hepatitis B infection. Previous studies demonstrated that variations in the human leukocyte antigen (HLA) class II (HLA-DPB1 and HLA-DQB2 genes) are related to the chronic HBV infection. This study aimed to investigate the association of two single nucleotide polymorphism (SNPs), one in the HLA-DPB1 (rs9277535) and one in the HLA-DQB2 (rs7453920), with chronic hepatitis B infection in a southern Brazilian sample. This case-control study included 260 HBV patients attended in a Specialized Center for Health in Caxias do Sul (Brazil) between 2014 and 2016. The same number of controls (matching for age, gender, and ethnicity) was obtained in a University Hospital in the same city and period. Blood samples were collected and genomic DNA was extracted. Genotyping were performed by real-time Taqman PCR method. Odds ratios with 95% confidence intervals and significance level of 5% (P < 0.05) were calculated. Allele frequencies in the SNP rs9277535 were 72.6% for A and 27.4% for G nucleotides in cases and 75.0% for A and 25.0% for G in controls. Allele frequencies in the SNP rs7453920 were of 25.7% for A and 74.3% for G in cases and 28.8% for A and 71.2% for G in controls. No statistically significant association was found between both SNPs and chronic hepatitis B (P > 0.05).

Educational intervention to control cockroach allergen exposure in the homes of hispanic children in Los Angeles: results of the La Casa study

BACKGROUND

Cockroach allergy is common among inner city children with asthma, and exposure to cockroach allergen is associated with more severe disease. However, there has been little evaluation of educational approaches for controlling cockroach infestations and reducing allergen exposure.

OBJECTIVE

An educational intervention to reduce cockroach allergen exposure in the homes of Hispanic children in Los Angeles was implemented and evaluated.

METHODS

Caretakers of 150 children with asthma were randomly assigned to an in-home intervention or comparison group. In the intervention group, peer health educators trained the caretaker to control cockroaches by reducing harbourage and access to food and by applying boric acid, and to reduce allergen exposure by cleaning. Allergen impermeable covers were placed on the child's mattress and pillows. Knowledge, reported and observed behaviour, cockroach counts, and cockroach allergen (Bla g 1) in dust samples from the kitchen and the child's bedding were assessed at study entry and at follow-up 4 months later.

RESULTS

There was improvement in knowledge and in observed and reported behaviour hypothesized to be associated with cockroach control. The geometric mean cockroach number in the intervention homes at the follow-up visit was 60% lower than in the non-intervention homes (95% confidence interval (CI) 14%, 81%). Geometric mean total cockroach allergen collected from the child's bedding was 64% lower in the intervention group (95% CI 12%, 85%). In homes with heavier initial cockroach infestation, there was a larger reduction in total kitchen dust allergen and concentration associated with the intervention than in homes with fewer initial cockroaches.

CONCLUSIONS

We conclude that reduction in number of cockroaches and in total allergen in bedding dust can be achieved by caretakers of asthmatic children following a single home educational intervention by peer educators.

[Management costs of chest and CNS-related adverse events associated with the treatment of acute migraine attacks with oral triptans]

INTRODUCTION

Although adverse events of triptans are usually not important from a clinical point of view, they can worry patients and lead them to consume healthcare resources.

METHODS

A decision analytic model was used to represent the behavior and management of patients who suffered adverse events after taking a triptan. Using data about the incidence of adverse events, the behavior and management of patients, and the unit cost of the healthcare resource consumed, the costs of treating adverse events were calculated, as was the iatrogenic cost factor of the triptans available in Spain.

RESULTS

10 % to 20 % of patients who suffer a chest or CNS-related adverse advent related to triptan use seek medical attention. The management cost of a chest-related event was estimated to be euros 66,43, euros 33,09, or euros 137,01, depending on whether the patient consulted a neurologist, a primary care physician, or a hospital emergency department. For CNS-related events the management cost was estimated to be euros 52,88, euros 16,89 or euros 102,17, respectively. Excluding the placebo effect, the resulting iatrogenic cost factor varied between 1 for almotriptan 12,5 mg and 1,21 for zolmitriptan 2,5 mg. In absolute values, the average cost per patient (above placebo) varied between 0 euros for almotriptan 12,5 mg and euros 1,17 for eletriptan 80 mg.

CONCLUSIONS

The management of adverse events can add substantial costs to a treatment with triptans. These costs vary considerably between triptans due to differences in the incidence of adverse events. Lowest costs were found for almotriptan 12,5 mg.

Prenatal care utilization and foetal outcomes at Harare Maternity Hospital, Zimbabwe

OBJECTIVES

To examine the association between adverse infant outcomes and maternal under utilization of prenatal care, among women delivering at Harare Maternity Hospital.

DESIGN

Hospital based, cross sectional study.

SETTING

Harare Maternity Hospital, Harare, Zimbabwe.

SUBJECTS

A random sample of 3,864 pregnant women.

MAIN OUTCOME MEASURES

Prenatal care utilization, maternal socio-demographic information, as well as birth weight and other neonatal outcome characteristics.

RESULTS

Of the total number of women who participated in this study 3,491 (90%) had at least one prenatal care visit. Women receiving no prenatal care, were more likely to be younger, unmarried and to have been transferred for delivery as compared with women receiving prenatal care. Women receiving no prenatal care were seven times more likely to deliver an infant weighing less than 1,500 grams, adjusted odd ratio (OR) = 7.22; 95% confidence interval (CI) 4.58 to 11.39 as compared with those who booked for care. Newborns of unbooked mothers were more likely to have a low apgar score at birth, adjusted OR = 1.71; to have been admitted to the neonatal intensive care unit, adjusted OR = 2.14, and to require intubation, adjusted OR = 3.35. A large proportion of women (31.4%) initiated prenatal care after 30 weeks gestation.

CONCLUSIONS

There were significant differences between maternal characteristics and foetal outcomes in relation to booking status. Under utilization of prenatal care was associated with sub-optimal foetal outcomes. Improving the socio-economic status of women, their education and access to health care, and family planning methods are all strategies that should contribute to the reduction of adverse foetal outcomes.

Autofluorescence patterns in short-term cultures of normal cervical tissue

Fluorescence spectroscopy has potential to improve cervical precancer detection. The relationship between tissue biochemistry and fluorescence is poorly understood. The goal of this study was to characterize normal cervical autofluorescence, using fresh tissue short-term tissue cultures and epithelial cell suspensions. Transverse, short-term tissue cultures were prepared from 31 cervical biopsies; autofluorescence images were obtained at 380 and 460 nm excitation. Fluorescence excitation-emission matrices were measured from normal, precancerous and cancerous cervical cell suspensions. Observed fluorescence patterns contrast those reported for frozen-thawed tissue, and were placed into groups with (1) bright epithelial and weak stromal fluorescence; (2) similar epithelial and stromal fluorescence; and (3) weak epithelial and bright stromal fluorescence. The average ages of women in the groups were 30.9, 38.0 and 49.2 years. Epithelial fluorescence intensity was similar in Groups 1 and 2, but weaker in Group 3. Stromal intensity was similar in Groups 2 and 3, but weaker in Group 1. The ratio of epithelial to stromal fluorescence intensity was significantly different for all groups. EEMs of cell suspensions showed peaks consistent with tryptophan, reduced form of nicotinamide adenine dinucleotide (phosphate) and flavin adenine dinucleotide. Short-term tissue cultures represent a novel, biologically appropriate model to understand cervical autofluorescence. Our results suggest a biological basis for the increased fluorescence seen in older, postmenopausal women.