Radiation therapy facilities in the United States
About half of all cancer patients in the United States receive radiation therapy as a part of their cancer treatment. Little is known, however, about the facilities that currently deliver external beam radiation. Our goal was to construct a comprehensive database of all radiation therapy facilities in the United States that can be used for future health services research in radiation oncology.
From each state's health department we obtained a list of all facilities that have a linear accelerator or provide radiation therapy. We merged these state lists with information from the American Hospital Association (AHA), as well as 2 organizations that audit the accuracy of radiation machines: the Radiologic Physics Center (RPC) and the Radiation Dosimetry Services (RDS). The comprehensive database included all unique facilities listed in 1 or more of the 4 sources.
We identified 2,246 radiation therapy facilities operating in the United States as of 2004-2005. Of these, 448 (20%) facilities were identified through state health department records alone and were not listed in any other data source.
Determining the location of the 2,246 radiation facilities in the United States is a first step in providing important information to radiation oncologists and policymakers concerned with access to radiation therapy services, the distribution of health care resources, and the quality of cancer care.
Available from: Ehsan Mihandoost
- "Radiotherapy is used for curative or palliative purpose in various patient malignancies . It is estimated that about 50–70% of clinical oncology treatments are performed with either radiotherapy alone or a combination of radiotherapy and chemotherapy  . However, radio sensitivity of normal tissues surrounding the tumor limits the therapeutic gain. "
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ABSTRACT: Nowadays, radiotherapy has become an integral part of the treatment regimen in various malignancies for curative or palliative purposes. Ionizing radiation interacts with biological systems to produce free radicals, which attack various cellular components. Radioprotectors act as prophylactic agents that are administered to shield normal cells and tissues from the harmful effects of radiation. Melatonin has been shown to be both a direct free radical scavenger and an indirect antioxidant by stimulating antioxidant enzymes and suppressing prooxidative enzymes activity. In addition to its antioxidant property, there have also been reports implicating antiapoptotic function for melatonin in normal cells. Furthermore, through its antitumor and radiosensitizing properties, treatment with melatonin may prevent tumor progression. Therefore, addition of melatonin to radiation therapy could lower the damage inflicted to the normal tissue, leading to a more efficient tumor control by use of higher doses of irradiation during radiotherapy. Thus, it seems that, in the future, melatonin may improve the therapeutic gain in radiation oncology treatments.
Available from: Mohammad Hadi Bahadori
- "On the basis of the evidence in different studies, melatonin is potentially useful in culture condition as direct scavenging of free radicals (2). Melatonin has the effect of: inhibition of the activity of a pro-oxidative enzyme, stimulation of the activity of antioxidant enzymes, distribution in all tissue, cells and cellular compartments throughout the organism, and rapid diffusion through all biological membranes (8-10). The results of this study indicate that COCs need lower concentration of melatonin (10 nM) during maturation stages in comparison to oocytes without cumulus cells. "
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ABSTRACT: Background: It is important to protect oocytes and embryos from oxidative stress in the culture medium. Melatonin has been shown to be a direct free radical scavenger.
Objective: Effect of melatonin during in vitro oocyte maturation, fertilization and embryo development of mouse oocytes was evaluated.
Materials and Methods: Oocytes from supper-ovulated mouse were divided to two groups: cumulus oocyte complexes (COCs, group I) and denuded COC (d-COCs, group II). The oocytes were cultured in maturation medium with different doses of melatonin (1×101-105 nM). The cumulus expansion and nuclear status were evaluated after 24 h of in-vitro maturation. The oocytes were used for in-vitro fertilization. The fertilized oocytes were cultured in medium supplemented with different doses of melatonin.
Results: The expansion (86.79%) and maturation (80.55%) rate of COCs increased in supplemented medium with 10 nM of melatonin vs. control group (73.33%), p=0.006 and p=0.026 respectively), but oocytes without cumulus cells indicated higher maturation rate at higher melatonin doses (10 and 100 M, 84.34% and 79.5% respectively( vs. 69.33% in control group (p=0.002). Fertilization rate was higher in treated medium with 1 μM of melatonin (93.75%, p=0.007). The rate of cleavage and blastocyst formation was promoted in medium supplemented with 10 and 100 nM of melatonin (92.37% and 89.36% vs. 81.25% in control group, p=0.002). We observed a dose dependent response to melatonin treatment in this experiment.
Conclusion: Exogenous melatonin can promote cumulus cell expansion, in vitro oocyte maturation, and embryo development. However we investigated a dose-dependent response in different stages of maturation and development. It may reflect sensitive rate of oocytes and embryos to culture conditions.
Available from: canterbury.ac.nz
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ABSTRACT: This thesis details an investigation of the suitability of commercially-available single crystal and polycrystalline diamond films made via chemical vapor deposition (CVD) that were not studied previously for use in radiotherapy dosimetry. Novel sandwich-type detectors were designed and constructed to investigate the dosimetric response of diamond films under clinical conditions. Relatively inexpensive diamond films were obtained from three manufacturers: Diamonex, Diamond Materials GmbH and Element Six. Spectrophotometry, Raman spectroscopy and bulk conductivity studies were used to characterize these films and correlate crystalline quality with detector performance. Novel detectors were designed and constructed to investigate detectors under clinical conditions, including Perspex encapsulations and PCBs to minimize fluence perturbations. The dosimetric response of these diamond detectors was examined using a 6 MV beam from a Varian Clinac 600C linear accelerator. Diamond detectors were evaluated by measuring a number of response characteristics. Polycrystalline CVD diamond films from Diamonex (100, 200, 400-μm thicknesses) were considered unsuitable for dosimetric applications due to their lack of stability, low sensitivity, high leakage currents, high priming dose and dependence on dose rate. High-quality polycrystalline diamond films from Diamond Materials (100, 200, 400-μm thicknesses) displayed characteristics that varied with film thickness. A 100-μm film featured slow response dynamics and high priming doses. Thicker films featured suitable dosimetric characteristics, e.g. negligible leakage currents, low priming doses, fast response dynamics and good sensitivity with small sensitive volumes. Element Six single crystal CVD diamond films (500-μm thicknesses) with small sensitive volumes (0.39 mm³) exhibited suitable characteristics for dosimetry. These films showed negligible leakage currents (< 1.25 pA), low priming doses (1–10 Gy), quick response dynamics, high sensitivity (47–230 nC Gy⁻¹) and were weakly dependent on dose rate and directional dependence (±1%). A relatively inexpensive single crystal CVD diamond film from Element Six that exhibited high sensitivity (230 nC Gy⁻¹ at 0.5 V μm⁻¹), amongst other favourable characteristics, was selected for further analyses. An appropriate operating voltage was determined before further clinically relevant measurements could be conducted. This included how changes in an applied electric field affected detector response, and determined whether an optimal operating voltage could be realized within the parameters of conventional instrumentation used in radiation therapy. The results of this study indicated a preference towards using 62.5 V (at ~0.13 V μm⁻¹) out of a range of 30.8–248.0 V for temporal response as required for modulated beams due to its minimal rise time (2 s) and fall time (2 s) yet sufficient sensitivity (37 nC Gy⁻¹) and weak dependence on polarity (±1.5%). Investigations were then performed on the same diamond detector to evaluate its performance under more clinically relevant conditions. Repeatability experiments revealed a temporary loss in sensitivity due to charge detrapping effects following irradiation, which was modelled to make corrections that improved short-term precision. It was shown that this detector could statistically distinguish between dose values separated by a single Monitor Unit, which corresponded to 0.77 cGy. Dose rate dependence was observed when using low, fixed doses in contrast to using stabilized currents and higher doses. Depth dose measurements using this detector compared well with ion chambers and diode dosimeters. Comparisons of initial measurements with values in the literature indicate encouraging results for fields sizes < 4 x 4 cm², but further measurements and comparisons with Monte Carlo calculations are required. Using this detector to make off-axis measurements in the edge-on orientation reduced perturbation of the beam due to its sandwich configuration and thin 150 nm Ag contacts. This diamond detector was found to be suitable for routine dosimetry with conventional radiotherapy instrumentation with a materials cost of < NZ$200.
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