Choice of beam energy and dosimetric implications for radiation treatment in a subpopulation of women with large breasts in the United States and Japan.

Radiation complications are often related to the dose inhomogeneity (hot spot) in breast tissue treated with conservative therapy, especially for large patients. The effect of photon energy on radiation dose distribution is analyzed to provide guidelines for the selection of beam energy when tangential fields and limited slices are used to treat women with large breasts. Forty-eight patients with chest wall separation > 22 cm were selected for dosimetric analysis. We compared the maximum dose in the central axis (CAX) plane (2D) using 6-, 10-, and 18-MV photon beams in all patients and 3D data set for 16 patients. Correlation between hot spot dose (HSD), separation, breast cup size, breast volume, and body weight was derived with beam energy. Among the 48 patients in this study, HSD > 10% in the CAX plane was noted in 98%, 46%, and 4% of the population when 2D dosimetry was performed; however, with 3D study, it was in 50%, 19%, and 6% of the patients with 6-MV, 10-MV and 18-MV beams, respectively. The chest wall separation, body weight, and breast volume were correlated with the HSD in both the 2D and 3D plans. Patient's bra size was not correlated with the hot spot. The chest wall separation was found to be the most important parameter to correlate with hot spot in tangential breast treatment. Simple guidelines are provided for dose uniformity in breast with respect to chest wall separation, body weight, bra size, and breast volume with tangential field irradiations.     

Rapidly growing mycobacteria: clinical and microbiologic studies of 115 cases

We analyzed clinical and microbiologic features of 115 cases involving rapidly growing mycobacteria (RGM) isolated at the University of Texas M.D. Anderson Cancer Center, Houston (2000-2005) and identified by 16S ribosomal RNA gene sequencing analysis. At least 15 RGM species were included: Mycobacterium abscessus (43 strains [37.4%]), Mycobacterium fortuitum complex (33 strains [28.7%]), and Mycobacterium mucogenicum (28 strains [24.3%]) most common, accounting for 90.4%. Most M abscessus (32/43) were isolated from respiratory sources, whereas most M mucogenicum (24/28) were from blood cultures. Antimicrobial susceptibility tests showed that M abscessus was the most resistant species; M mucogenicum was most susceptible. From blood and catheter sources, 46 strains (40.0%) were isolated; 44 represented bacteremia or catheter-related infections. These infections typically manifested high fever (mean temperature, 38.9 degrees C), with a high number of RGM colonies cultured. All infections resolved with catheter removal and antibiotic therapy. Six strains (M abscessus and M fortuitum only) were from skin, soft tissue, and wound infections. There were 59 strains from respiratory sources, and 28 of these represented definitive to probable infections. Prior lung injuries and coisolation of other pathogenic organisms were common. Overall, 78 RGM strains (67.8%) caused true to probable infections without direct deaths.     

Effect of processor temperature on film dosimetry

Optical density (OD) of a radiographic film plays an important role in radiation dosimetry, which depends on various parameters, including beam energy, depth, field size, film batch, dose, dose rate, air film interface, postexposure processing time, and temperature of the processor. Most of these parameters have been studied for Kodak XV and extended dose range (EDR) films used in radiation oncology. There is very limited information on processor temperature, which is investigated in this study. Multiple XV and EDR films were exposed in the reference condition (d_max., 10 × 10 cm², 100 cm) to a given dose. An automatic film processor (X-Omat 5000) was used for processing films. The temperature of the processor was adjusted manually with increasing temperature. At each temperature, a set of films was processed to evaluate OD at a given dose. For both films, OD is a linear function of processor temperature in the range of 29.4–40.6°C (85–105°F) for various dose ranges. The changes in processor temperature are directly related to the dose by a quadratic function. A simple linear equation is provided for the changes in OD vs. processor temperature, which could be used for correcting dose in radiation dosimetry when film is used.     

Testing for aerobic heterotrophic bacteria allows no prediction of contamination with potentially pathogenic bacteria in the output water of dental chair units

Background: Currently, to our knowledge, quality of output water of dental chair units is not covered by specific regulations in the European Union, and national recommendations are heterogeneous. In Germany, water used in dental chair units must follow drinking water quality. In the United States of America, testing for aerobic heterotrophic bacteria is recommended. The present study was performed to evaluate whether the counts of aerobic heterotrophic bacteria correlate with the presence of potentially pathogenic bacteria such as Legionella spp. or Pseudomonas aeruginosa. Methods: 71 samples were collected from 26 dental chair units with integrated disinfection device and 31 samples from 15 outlets of the water distribution pipework within the department were examined. Samples were tested for aerobic heterotrophic bacteria at 35°C and 22°C using different culture media and for Legionella spp. and for Pseudomonas aeruginosa. Additionally, strains of Legionella pneumophila serogroup 1 were typed with monoclonal antibodies and representative samples of Legionella pneumophila serogroup 1 were typed by sequence based typing.Results: Our results showed a correlation between different agars for aerobic heterotrophic bacteria but no correlation for the count of aerobic heterotrophic bacteria and the presence of Legionella spp. or Pseudomonas aeruginosa.Conclusion: Testing for aerobic heterotrophic bacteria in output water or water distribution pipework within the departments alone is without any value for predicting whether the water is contaminated with potentially pathogenic bacteria like Legionella spp. or Pseudomonas aeruginosa.     

Microarray analysis and biochemical correlations of oxidative stress responsive genes in retinoblastoma

Purpose: Oxidative stress, which refers to the biological damage caused by free radicals produced in excess of innate antioxidant defenses, is indicated in the ocular cancer retinoblastoma (RB). Here we have analysed the differential expression of oxidative stress responsive genes in oxidant-induced RB cells, and in RB tumor tissues. Methods: The study included cultured RB cells, and four RB tumor tissues. The reactive oxygen species (ROS) levels in Y79 cells and the RB tumor induced by hydrogen peroxide were quantified by Dichlorofluorescein (DCF) fluorescence assay. We then analysed the gene expression profile of cultured RB cells induced with hydrogen peroxide (400 μM H(2)O(2) for 8 h) by microarray analysis, and the expression of select genes were validated in Y79 cells and RB tumor tissues by real-time PCR analysis. Results: The oxidant-induced RB tumors showed an average increase in ROS levels of 44-fold compared to induced non-neoplastic donor retina. H(2)O(2)-induced RB cell line showed a 3-fold increase in ROS levels. Microarray analysis on RB cell line induced with H(2)O(2) showed differentially regulated genes involved in cellular processes such as: oxidative stress, angiogenesis, lipid metabolism, cell proliferation, and cell signaling pathways. Several up-regulated genes such as SOD, GPX, CAT, CDC25A, CREBBP, JUN, MMP-2, iNOS, CRYAA, RXRA, ACACB and HMGCR were validated by real-time PCR. These results corroborated with the gene expression analysis in RB tumor tissues. Relating the antioxidant gene expression with the clinico-pathologic features of the tumor tissues, we found that the tumor with invasion of choroid, optic nerve and retinal pigment epithelium, had relatively higher ROS levels and minimal antioxidant gene expression, when compared with the tumor with only choroidal invasion. Conclusions: The study suggests active involvement of redox signaling pathways in the pathogenesis of RB. Consideration of oxidative stress components in the clinical management of RB patients is emphasized.