Cobalt-60 Teletherapy Research Articles

Risk assessment for occupational potential exposure at cobalt teletherapy units

The occupational potential exposure risk that could occur due to source stuck event at 60Co teletherapy facility is estimated. Such risk estimation has been carried out quantitatively and qualitati...

Protective effects of genistein and melatonin on mouse liver injury induced by whole-body ionising radiation.

The aim of the present study was to investigate the effectiveness of melatonin and genistein in preventing radiation therapy (RT)-induced liver injury in mice. A total of 70 Swiss Albino male mice were divided into 7 equal groups (n=10/group) as follows: Melatonin (M group, G3), genistein (G group, G4), polyethylene glycol-400 (P group, G5), RT only (RT group, G2) and sham irradiation (C group, G1). RT plus genistein (RT+G group, G7) and RT plus melatonin (RT+M group, G6) were the co-treatment groups. Firstly, hepatic tissue damage was induced in mice via exposure to a single dose of 6-Gy irradiation. RT was performed with a cobalt-60 teletherapy machine (80 cm fixed source-to-surface distance, 2.5-cm depth). Melatonin was processed (100 mg/kg, intraperitoneal) 30 min before and genistein was administered (200 mg/kg, SC) one day prior to the single dose of irradiation. Six months following irradiation, all mice were sacrificed. The degree of liver injury was measured using histological liver sections. Liver injury was significantly worse in the RT group than in the control group (C; RT vs. C; P<0.05); however, liver injury decreased following co-treatment with melatonin or genistein vs. RT alone (RT+M and RT+G vs. RT; P<0.05). No difference was observed between the RT+M and RT+G groups (P>0.05). The present study revealed that melatonin and genistein administration prior to irradiation protects mice against liver injury, which may have therapeutic implications for RT-induced injuries.

Dosimetric evaluation of cobalt-60 teletherapy in advanced radiation oncology

AbstractBackgroundRecent investigations demonstrate a strong potential for cobalt-60 (Co-60)-based teletherapy. The influence of the lower energy and penetration of a cobalt-60 beam compared with linear accelerator beams is negligible for intensity-modulated radiotherapy.PurposeThe aim of this research is to investigate source head fluence modulation in cobalt-60 teletherapy by using a three-dimensional (3D) physical compensator and secondary collimator jaw motion.Materials and methodsThe Oncentra treatment planning system was used to develop three hypothetical plans by secondary collimator jaw motion. A clinical MDS Nordion Equinox 80 cobalt-60 teletherapy unit was used to acquire conventional water phantom beam characteristics. Fluence modulation experiments were executed at 5·0 cm depth in a PTW universal intensity-modulated radiation therapy (IMRT) verification phantom using calibrated Gafchromic external beam therapy 2 (EBT2) and RTQA2-1010 film batches. Gafchromic EBT2 film was used to sample intensity maps generated by secondary collimator jaw motion, yet Gafchromic RTQA2-1010 film sampled maps from the 3D physical compensator. The solid-state drives used were 75·0 and 74·3 cm for the Gafchromic EBT2 and Gafchromic RTQA2-1010 film measurements.ResultsA 2D gamma index analysis was coded to compare EBT2 film measurements with Digital Imaging and Communications in Medicine data. This analysis was also used to verify film measurements versus Monte-Carlo simulations.ConclusionLateral beam profiles generated from water phantom measurements were used to establish source head fluence modulation on the film measurements. The source head fluence of a cobalt-60 teletherapy beam could be modulated by secondary collimator jaw motion and using a 3D physical compensator.

Assessment of Radiation Therapy Resources in the Dominican Republic

The Dominican Republic (DR) is an upper-middle-income country that has taken several strides to address cancer care at the national level. In 2007, a national healthcare plan known as the Seguro Familiar Salud (SFS) was established. Presently, the SFS provides coverage to 65% of the DR population and substantially covers radiotherapy center and machine maintenance costs; in effect, there has been a drastic expansion of radiotherapy services since 2010. We sought to review the radiotherapy resources currently in the DR and assess the impact of these resources within the Caribbean. We queried the Directory of Radiotherapy Centres (DIRAC) to obtain information on the radiotherapy resources in the Caribbean. Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology (GEC-ESTRO) and International Atomic Energy Agency (IAEA) recommendations in conjunction with 2012 GLOBOCAN cancer incidence data were employed to assess the radiotherapy resources in the DR and compare these resources in context with the resources in other Caribbean countries. The DR has 12 centers with 19 linear accelerators, 1 Cobalt-60 (Co-60) teletherapy unit, 2 Co-60 stereotactic units. High-dose rate (HDR) brachytherapy is offered at 4 sites and low-dose rate (LDR) brachytherapy is offered at 1 site. Staffing in the DR includes 26 radiation oncologists, 12 medical physicists, and 12 dosimetrists. On assessment, the DR has a sufficient number of radiotherapy machines, but needs six additional physicians and physicists. In comparison to other Caribbean countries, the DR contains the most radiotherapy centers and machines with the latest technology. Notably Haiti, the third most populous Caribbean country, has no radiotherapy resources. As many Caribbean countries do not have radiotherapy centers, patients may travel elsewhere to receive radiotherapy. If only considering the countries that are not territories of mainland countries, with the exception of Puerto Rico and Martinique that do have radiotherapy centers, an additional 47 teletherapy machines are needed in the Caribbean, reflecting a 40% increase. The DR has emerged as a leader of radiotherapy resources in the Caribbean. Understanding of the radiotherapy resources in the DR is important as Caribbean countries without radiotherapy resources, such as Haiti, utilize the same resources. The DR has a robust radiotherapy program, but does not have enough resources to compensate for patients from other Caribbean countries that lack radiotherapy resources.

A ring-based compensator IMRT system optimized for low- and middle-income countries: Design and treatment planning study.

We propose a novel compensator-based IMRT system designed to provide a simple, reliable, and cost-effective adjunct technology, with the goal of expanding global access to advanced radiotherapy techniques. The system would employ easily reusable tungsten bead compensators that operate independent of a gantry (e.g., mounted in a ring around the patient). Thereby the system can be retrofitted to existing linac and cobalt teletherapy units. This study explores the quality of treatment plans from the proposed system and the dependence on associated design parameters. We considered 60 Co-based plans as the most challenging scenario for dosimetry and benchmarked them against clinical MLC-based plans delivered on a linac. Treatment planning was performed in the Pinnacle treatment planning system with commissioning based on Monte Carlo simulations of compensated beams. 60 Co-compensator IMRT plans were generated for five patients with head-and-neck cancer and five with gynecological cancer and compared to respective IMRT plans using a 6 MV linac beam with an MLC. The dependence of dosimetric endpoints on compensator resolution, thickness, position, and number of beams was assessed. Dosimetric accuracy was validated by Monte Carlo simulations of dose distribution in a water phantom from beams with the IMRT plan compensators. The 60 Co-compensator plans had on average equivalent PTV coverage and somewhat inferior OAR sparing compared to the 6 MV-MLC plans, but the differences in dosimetric endpoints were clinically acceptable. Calculated treatment times for head-and-neck plans were 7.6 ± 2.0 min vs 3.9 ± 0.8 min (6 MV-MLC vs 60 Co-compensator) and for gynecological plans were 8.7 ± 3.1 min vs 4.3 ± 0.4 min. Plan quality was insensitive to most design parameters over much of the ranges studied, with no degradation found when the compensator resolution was finer than 6 mm, maximum thickness at least 2 tenth-value-layers, and more than five beams were used. Source-to-compensator distances of 53 and 63 cm resulted in very similar plan quality. Monte Carlo simulations suggest no increase in surface dose for the geometries considered here. Simulated dosimetric validation tests had median gamma pass rates of 97.6% for criteria of 3% (global)/3 mm with a 10% threshold. The novel ring-compensator IMRT system can produce plans of comparable quality to standard 6 MV-MLC systems. Even when 60 Co beams are used the plan quality is acceptable and treatment times are substantially reduced. 60 Co-compensator IMRT plans are adequately modeled in an existing commercial treatment planning system. These results motivate further development of this low-cost adaptable technology with translation through clinical trials and deployment to expand the reach of IMRT in low- and middle-income countries.

TREATMENT OF RADIOTHERAPY FOR SERVIKS CANCER WITH SEPARATION MORE THAN 20 CENTIMETERS USING COBALT-60 AT UNIT RADIOTHERAPY INSTALLATION RADIOLOGY RSUP DR. KARIADI SEMARANG

Background: Cervical cancer is a type of cancer that emerges from the cervix. In the early stages of the tumor, treatment therapy will be performed surgically on organs affected by cancer cells, at an advanced stage will be done adjuvant therapy with curative goals through a combination of chemotherapy, surgery, and radiotherapy. In radiotherapy treatment is done with several techniques such as Brachyterapi, IMRT, 3DCRT, and 2D with external aircraft radiation modality with Linac (Linear Accelator) and Cobalt-60. For Brachyterapi (internal radiation) technique, the radiation source is directly placed on the target tumor by using the after loading technique generally, whereas the external radiation techniques of 3DCRT and IMRT are generally performed on external radiation plane using MLC (Multi leaf Collimator) by following the target shape tumors resulting from CT Simulator and TPS (Treatment Planning System) calculations. For IMRT alone the technique used is almost the same as 3DCRT technique. In cobalt-60 is generally used for the treatment of radiation therapy has an average energy of 1.25 MV. At 1.25 MV cobalt energy with 10x10 cm field area will get maximal energy at depth (d max) 0.5 cm and energy will decrease to half (d half) at a depth of 11 centimeter on water media. So that in planning of radiation using cobalt-60 plane have limited separation diameter less than 20centimeter. Methods : This type of research is qualitative with case study approach. the data was collected in October-December 2017 at radiotherapy Installation of Dr. Kariadi General Hospital Semarang by observation methodology, interview with Radiation Oncologist Specialist, Medical Physiciast and Radiographer. the data obtained from the study were analyzed by an interactive model, creating the interview transcripts subsequently reduced and processed within the type of open coding, given within the type of quotations then are often drawn conclusions. Result: The results of this study demonstrate that the management of cervix cancer radiation utilizing 2D procedure in radiotherapy installation of Dr. Kariadi General Hospital Semarang includes patient examination, planning medical physics, verification and radiation treatments. 2D techniques are used pupose to paliative radiation, homogenity of dose and the location of the target volume is close to the Organ at Risk. Field radiation evaluation was performed before first and third irradiation, patient evaluation after five times of radiation and evaluation after 25rd radiation. Conclusion: The reason for doing the external radiation exposure of cervical cancer with tumor stage further consideration according to the Anatomical Pathology with pT3aN0M0 stage. So the purpose of palliative external radiation. with cervical cancer using cobalt-60 teletherapy air as much as 50 Gy with a fractionation s25 times, and each fractionation with doses of 2Gy. The reason for doing the external radiation exposure of cervical cancer with tumor stage further consideration according to the Anatomical Pathology with pT3aN0M0 stage. So the purpose of palliative external radiation. with cervical cancer using cobalt-60 teletherapy air as much as 50 Gy with a fractionation 25 times, and each fractionation with doses of 2Gy. The reason for doing the external radiation exposure of cervical cancer with tumor stage further consideration according to the Anatomical Pathology with pT3aN0M0 stage. So the purpose of palliative external radiation

Imaging and Dosimetric Consideration for Titanium Prosthesis Implanted within the Irradiated Region by Cobalt-60 Teletherapy Unit

The aim of this research is to observe dose distributions in the vicinity of titanium prosthetic implants during radiotherapy procedures on 60Co teletherapy machine, Prowess Panther treatment planning system (TPS). Data were obtained using a locally fabricated tissue equivalent phantom CT images with titanium prosthesis which was irradiated with 60Co gamma radiation. Prowess TPS (1.25 MeV) estimated less variations. Proximal ends of the metal recorded slight increase in doses as a result of backscatter with dose increment below acceptable tolerance of ±3%. Doses measured decreases on the distal side of the prosthesis at a distance less than dmax from the plate on each beam energy. The depth dose increases marginally after a certain depth level which generally originated from the unperturbed dose due to increase in the electron fluence. The percentage of depth doses decrease with the increase in plate thickness. A reduction in the above trend was also noticed with an increase in beam energy primarily because scattered photons are more forwardly directed. Prowess TPS (convolution superposition algorithm) was found to be better at reducing dose variation when correction for artifact. Manual calculations on blue phantom data agree with results from Prowess. This treatment system is capable of simulating dose around titanium prosthesis as its range of densities, 0.00121 to 2.83, excludes titanium density (rED for titanium is 3.74).

Leakage radiation and workplace monitoring of a cobalt-60 teletherapy facility in South-West Nigeria: Is the dose significant?

BACKGROUND: Cobalt-60 (Co-60) teletherapy machines are still in use in most developing countries because of their minimal power requirements, reduced operational cost, and since the source does not vary in energy, the amount of quality assurance required to ensure “good beam” is dramatically reduced. Although as the machine wear, the chances of leakage radiation increase. AIMS AND OBJECTIVES: The aim of this study was to determine if leakage radiation at 5 cm and 1 m from the Co-60 teletherapy source head is within the acceptable tolerance limit set by the International Electro-technical Commission (IEC) and to determine if controlled and supervised areas within working hours were within the Institute of Physics and Engineering in Medicine (IPEM) limit. MATERIALS AND METHODS: The machine used was a Theratron® Phoenix Cobalt 60 Teletherapy machine. A RadEye™ B20-ER Multi-Purpose Survey Meter was used to measure mean time-average dose rate (TADR) at various points in the controlled and supervised areas. Instantaneous dose rate (IDR) for leakage radiation was measured at 5 cm from the source head using the same Survey Meter and a measuring tape. In addition, measurement was made at 1 m from the normal treatment distance in patient and nonpatient planes. RESULTS: The mean TADR at beam OFF position in the controlled area at four different areas was 2.15 ± 0.48 μSv/h, which was <7.5 μSv/h IPEM limit and mean TADR in the supervised area at six different areas was 1.70 ± 0.45 μSv/h, which was also <2.5 μSv/h IPEM limit. The percentage IDR leakage radiation at beam OFF position at 5 cm and 1 m was within 200 μSv/h and 20 μSv/h IEC tolerance limit, respectively. Percentage leakage radiation at beam ON in patient plane was below the maximum and average IEC tolerance limit and nonpatient planes at 1 m was below 0.5% IEC limit. CONCLUSION: Supervised and controlled areas were within the acceptable range. Leakage radiation was within the tolerance limit.

Re-Shielding of Cobalt-60 Teletherapy Rooms for Tomotherapy and Conventional Linear Accelerators using Monte Carlo Simulations

Purpose. Nearly all Cobalt-60 teletherapy machines were removed around the world during the last two decades. The remaining ones are being used for experimental purposes. However, the rooms of these teletherapy machines are valuable because of lack of space in radiotherapy clinics. In order to place a new technology treatment machine in one of these rooms, one should re-shield the room since it was designed only for 1.25 MeV gamma beams on average. Mostly, the vendor of the new machine constructs the new shielding of the room using their experience. However, every radiotherapy room has different surrounding work areas and it would be wise to shield the room considering these special conditions. Also, the shield design goal of the clinic may be much lower than the International Atomic Energy Agency (IAEA) or the local association accepts. The study shows re-shielding of a Cobalt-60 room, specific to the clinic, using Monte Carlo simulations.Materials & Methods. First, a 6 MV Tomotherapy machine, then a 10 MV conventional linear accelerator (LINAC) was placed inside the Cobalt-60 teletherapy room. The photon flux outside the room was simulated using Monte Carlo N-Particle (MCNP6.1) code before and after re-shielding.For the Tomotherapy simulation, flux distributions around the machine were obtained from the vendor and implemented as the source of the model. The LINAC model was more generic with the 10 MeV electron source, the tungsten target, first and secondary collimators. The aim of the model was to obtain the maximum (40x40 cm2 ) open field at the isocenter. Two different simulations were carried out for gantry angles 90o and 270o . The LINAC was placed in the room such that the primary walls were A’ (Gantry 270o ) and C’ (Gantry 90o ) (figure 1).The second part of the study was to model the re-shielding of the room for Tomotherapy and for the conventional LINAC, separately. The aim was to investigate the recommended shielding by the vendors. Left side of the room was adjacent to a LINAC room with 2 meters thick concrete wall (figure 1). No shielding was necessary for that wall. Behind wall A-A’ there was an outdoors forbidden area; behind wall B-B’ was the contouring room for the doctors; and the control room was behind wall C-C’ (figure 1). After some modifications, the final shielding was designed.Results. The photon flux distributions outside the room before and after the re-shielding were compared. The re-shielding of Tomotherapy reduced the flux down to 1.89 % on average with respect to pre-shielding (table 1). For the conventional LINAC case; after re-shielding, the photon flux in the control room -which corresponds to gantry 90°- decreased down to 0.57% with respect to pre-shielding (table 2). The photon flux behind wall A’ -which corresponds to gantry 270°- decreased down to 2.46%. Everybody was all safe behind wall B’ even before re-shielding.

Radioactive Cobalt-60 Teletherapy Machine - Estimates of Personnel Dose in Mock Emergency in Patient Release during "Source Stuck Situation".

Radioactive Cobalt-60 Teletherapy Machine - Estimates of Personnel Dose in Mock Emergency in Patient Release during "Source Stuck Situation".

Expression of Radioresistant Gene PEG10 in OSCC Patients and Its Prognostic Significance

Background:Oral squamous cell carcinoma (OSCC) is one of the most common forms of cancer occurring worldwide. PEG10 is well known as a paternally expressed gene from a newly recognized imprinted region at human chromosome 7q21. Previous study had demonstrated that the significant expression of PEG10 was found in radioresistant OSCC cell line and its expression was significantly associated with poor survival in several cancers. Therefore it has been evaluated as a potential marker in OSCC patients undergoing radiotherapy.Objective:This study was conducted to analyze the mRNA expression of PEG10 in OSCC and its expression in relation to clinicpathological features, radiotherapy treatment response and survival.Methods:This study included tissue specimens obtained via biopsy of 118 patients with OSCC who were recommended for radiotherapy treatment and 80 healthy control tissues analysis of mRNA expression of PEG10 was done by real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Patients were treated with 70 Gy of radiation dose by shrinking field technique using Cobalt-60 teletherapy machine.Results:Significantly higher mRNA expression of PEG10 was found in OSCC patients when compared with matched controls. High level of PEG10 mRNA expression showed a significant correlation with lymph node metastasis (p = 0.0047) and tumor stage (p = 0.0499). Multivariate Cox regression analysis revealed that high level of mRNA expression of PEG10 was significantly associated with poor survival (p < 0.05). Our research demonstrated that the expression of PEG10 was higher in radioresistant tumor.Conclusion:We observed significantly increased expression of PEG10 in context of lymph node status, advanced stage and poor survival in our study. Thus PEG10 gene can be used as potential predictive and prognostic biomarker in OSCC patients undergoing radiotherapy.

Radioprotective effect of hesperidin on reducing oxidative stress in the lens tissue of rats.

Introduction:Oxidative stress is a common factor in cataract. Considering the antioxidant properties of hesperidin as a flavanone glycoside from the flavonoid family with radioprotective effect, this study aimed to determine the protective effect of this flavanone glycoside on reducing oxidative stress in the eye lens tissue of mature rats caused by gamma irradiation.Materials and Methods:A total of 48 adult rats were randomly divided into six groups, namely, control, Dimethyl sulfoxide (DMSO), hesperidin, radiation, radiation + DMSO, and radiation + hesperidin. 15 Gy irradiation was carried out using Cobalt-60 teletherapy instrument with a source-to-surface distance of 80 cm at a dose rate of 98.5 cGy/min. 2 days following irradiation, we removed the rats' lenses and analyzed them to determine the effects of hesperidin.Results:The comparison of control and intervention groups after irradiation showed that malondialdehyde (MDA) level in the lens tissue was significantly higher in the irradiation groups than the control group. Furthermore, a significant difference between radiation and radiation + hesperidin groups were observed. The level of glutathione (GSH) in the lens tissue was significantly lower in the irradiation groups compared to the control group. Nonetheless, significant elevation of GSH in the radiation + hesperidin group compared to radiation group was seen.Conclusions:Radiation exposure reduced GSH and enhanced MDA levels in the lens tissue. However, GSH and MDA levels were modulated after hesperidin consumption. These results show the antioxidative properties of hesperidin in the lens and demonstrated that radiation complications such as cataract can be reduced by hesperidin through reducing oxidative stress.

Reduced incidence of interstitial pneumonitis after allogeneic hematopoietic stem cell transplantation using a modified technique of total body irradiation.

Allogeneic hematopoietic stem cell transplantation is a curative-intent treatment for patients with high-risk hematologic diseases. However, interstitial pneumonitis (IP) and other toxicities remain major concerns after total body irradiation (TBI). We have proposed using linear accelerators with rice-bag compensators for intensity modulation (IM-TBI), as an alternative to the traditional cobalt-60 teletherapy with lung-shielding technique (Co-TBI). Patients who received a TBI-based myeloablative conditioning regimen between 1995 and 2014 were recruited consecutively. Before March 2007, TBI was delivered using Co-TBI (n = 181); afterward, TBI was administered using IM-TBI (n = 126). Forty-four patients developed IP; of these cases, 19 were idiopathic. The IP-related mortality rate was 50% in the total IP cohort and 63% in the idiopathic subgroup. The 1-year cumulative incidences of IP and idiopathic IP were 16.5% and 7.4%, respectively; both rates were significantly higher in the Co-TBI group than in the IM-TBI group. Multivariate analysis revealed that Co-TBI was an independent prognostic factor for both total and idiopathic IP. In the acute myeloid leukemia subgroup, patients with different TBI techniques had similar outcomes for both overall and relapse-free survival. In conclusion, IM-TBI is an easy and effective TBI technique that could substantially reduce the complication rate of IP without compromising treatment efficacy.

Monte Carlo based investigations of electron contamination from telecobalt unit head in build up region and its impact on surface dose

A Telecobalt unit has wide range of applications in cancer treatments and is used widely in many countries all around the world. Estimation of surface dose in Cobalt-60 teletherapy machine becomes important since clinically useful photon beam consist of contaminated electrons during the patient treatment. EGSnrc along with the BEAMnrc user code was used to model the Theratron 780E telecobalt unit. Central axis depth dose profiles including surface doses have been estimated for the field sizes of 0×0, 6×6, 10×10, 15×15, 20×20, 25×25, 30×30cm2 and at Source-to-surface distance (SSD) of 60 and 80cm. Surface dose was measured experimentally by the Gafchromic RTQA2 films and are in good agreement with the simulation results. The central axis depth dose data are compared with the data available from the British Journal of Radiology report no. 25. Contribution of contaminated electrons has also been calculated using Monte Carlo simulation by the different parts of the Cobalt-60 head for different field size and SSD's. Moreover, depth dose curve in zero area field size is calculated by extrapolation method and compared with the already published data. They are found in good agreement.

DVH Analysis of Cobalt-60 treatment plans incorporating a recently developed MLC

Purpose: The aim of this investigation was to measure the gain in DVH indices when the recently developed MLC was used for Cobalt-60 treatments. Methods: A prototype multileaf collimator (MLC) that was retrofitted to telecobalt-60 therapy machine was reported and is currently proposed for clinical trials in our institution. Ten patients’ plans that were previously planned through an ECLIPSE ® treatment planning system and were treated with open beams from Cobalt-60 machine were imported into Radiation Oncology Planning System [ROPS] and the dose calculations and dose volume histogram (DVH) analysis were performed. The plans were re-planned using the Cobalt-MLC, a feature available in the ROPS planning system. The DVH analysis consisted of conformity index (CI), homogeneity index (HI) and conformation number (CN). The results of this study are presented in this paper. The analysis specifically aimed at measuring the gain in these indices when the MLC was compared with open beams. Results: DVH Comparison of ten sites using open and Cobalt MLC fields showed that the use of MLC results in reduced normal tissue dose, while maintaining the GTV dose. Lower value of CI for normal structures was observed demonstrating the sparing of critical organs when MLC was used. The index HI was studied to show the significance of hot spots outside the PTV. Hot spots were observed even with MLC beams for some cases due to less number of fields. Conclusion: It has been demonstrated through DVH analysis that the use of the recently developed MLC for Cobalt Teletherapy machine results in benefit for the treatment of patients.

Validation of in-house treatment planning system software for cobalt-60 teletherapy unit at two radiotherapy installations

DSSuperDose v.1.0 is an in-house treatment planning system (TPS) developed by Medical Physics and Biophysics Laboratory (LFMB) Universitas Indonesia as a treatment planning software for Cobalt-60 teletherapy unit. The main objective of this study was the validation of in-house TPS calculation as an essential part in quality assurance (QA) of radiotherapy. Validation of an in-house TPS was performed with two Cobalt-60 teletherapy units by comparison between in-house TPS and ISIS TPS and by measurements of absorbed dose. Mean dose deviations between in-house TPS and measurement were (1.97 ± 2.42)% for open field, (1.32 ± 1.30)% for tray field, and (2.91 ± 2.36)% for wedge field treatments. In-house TPS provide optimal planning for open and tray beam conditions with depth fewer than 10 cm (≤ 10 cm) and field sizes up to 20×20 cm2, while for wedge beam conditions with field sizes fewer than the physical size of the wedge. Comparison of in-house TPS and ISIS TPS demonstrated a good match of 96%. From the results, it is concluded that DSSuperDose v.1.0 is adequately accurate for treatment planning of radiotherapy.

Neuroprotective effects of erythropoietin against oxidant injury following brain irradiation: an experimental study.

IntroductionRadiation therapy (RT) is a major treatment modality, and the central nervous system is a dose-limiting organ in clinical RT. This experimental study aims to present the evaluation of the neuroprotective effects of erythropoietin (EPO) against oxidant injury following brain irradiation in rats.Material and methodsForty Wistar rats were randomly assigned to four groups (n = 10 each). In group 1 the rats received no EPO and underwent sham RT. The rats in groups 2 and 3 received EPO. In group 2 rats underwent sham RT, while in group 3 rats received RT. The rats in group 4 received no EPO and underwent RT. Rats were irradiated using a Cobalt-60 teletherapy machine using a single fraction of 20 Gy covering the whole brain. Cervical dislocation euthanasia was performed. The nitrite and malondialdehyde (MDA) levels and the superoxide dismutase (SOD) and glutathione peroxidase (GSHPX) activities were evaluated in dissected brain tissues.ResultsThe nitrite and MDA levels were higher in the RT group (2.10 ±0.62 ppm, 26.02 ±2.16 nmol/ml; p < 0.05) and lower in the EPO + RT group (1.45 ±0.12 ppm, 25.49 ±1.90 nmol/ml; p < 0.05). The SOD and GSHPX activity was higher in the EPO + RT group (2.62 ±0.49 U/mg, 1.75 ±0.25 U/mg, p < 0.05).ConclusionsThis study supports the probable neuroprotective effects of EPO against oxidant injury following brain irradiation in a rat model, presumably through decreasing free radical production and increasing expression of antioxidant enzymes.

Comparison of the effects of melatonin and genistein on radiation-induced nephrotoxicity: Results of an experimental study.

The aim of the present study was to compare the effects of melatonin and genistein on radiation-induced nephrotoxicity (RIN). A total of 70 Swiss Albino mice were divided into 7 groups. Five control groups were defined, which were sham irradiation (C, G1), radiation therapy only (RT, G2), melatonin (M, G3), genistein (G, G4) and polyethylene glycol-400 (G5), respectively. The co-treatment groups were the RT plus melatonin (RT+M, G6) and RT plus genistein (RT+G, G7) groups. Irradiation was applied using a cobalt-60 teletherapy machine (80-cm fixed source-to-surface distance, 2.5-cm depth). Melatonin was administered (100 mg/kg, intraperitoneal injection) 30 min before the single dose of irradiation, whereas genistein was administered (200 mg/kg, subcutaneous injection) 1 day before the single dose of irradiation. All the mice were sacrificed 6 months after irradiation. As an end point, the extent of renal tubular atrophy for each mouse was quantified with image analysis of histological sections of the kidney. Tissue malondialdehyde (MDA) levels were also measured in each animal. In the histopathological examination of the mouse kidneys, there was a statistically significant reduction (P<0.05) in the presence of tubular atrophy between the RT+M and RT+G groups and the RT group. There was a statistically significant increase in MDA levels in the irradiated versus sham groups (RT vs. C; P<0.05); however, MDA levels were significantly decreased by co-treatment with melatonin or genistein vs. RT alone (RT+M and RT+G vs. RT; P<0.05). In conclusion, the present experimental study showed that melatonin and genistein supplementation prior to irradiation-protected mice against RIN, which may have therapeutic implications for radiation-induced injuries.

Development, physical properties and clinical applicability of a mechanical Multileaf Collimator for the use in Cobalt-60 radiotherapy

According to the Directory of Radiotherapy Centres (DIRAC) there are 2348 Cobalt-60 (Co-60) teletherapy units worldwide, most of them in low and middle income countries, compared to 11046 clinical accelerators. To improve teletherapy with Co-60, a mechanical Multi-Leaf Collimator (MLC) was developed, working with pneumatic pressure and thus independent of electricity supply. Instead of tungsten, brass was used as leaf material to make the mechanical MLC more affordable. The physical properties and clinical applicability of this mechanical MLC are presented here. The leakage strongly depends on the fieldsize of the therapy unit due to scatter effects. The maximum transmission through the leaves measured 2.5 cm from the end-to-end gap, within a field size of 20 cm × 30 cm defined by jaws of the therapy unit at 80 cm SAD, amounts 4.2%, normalized to an open 10 cm × 10 cm field, created by the mechanical MLC. Within a precollimated field size of 12.5 cm × 12.5 cm, the end-to-end leakage is 6.5% normalized to an open 10 cm × 10 cm field as well. This characteristic is clinically acceptable considering the criteria for non-IMRT MLCs of the International Electrotechnical Commission (IEC 60601-2-1). The penumbra for a 10 cm × 10 cm field was measured to be 9.14 mm in plane and 8.38 mm cross plane. The clinical applicability of the designed mechanical MLC was affirmed by measurements relating to all relevant clinical properties such as penumbra, leakage, output factors and field widths. Hence this novel device presents an apt way forward to make radiotherapy with conformal fields possible in low-infrastructure environments, using gantry based Co-60 therapy units.

Size Effects of Gold and Iron Nanoparticles on Radiation Dose Enhancement in Brachytherapy and Teletherapy: A Monte Carlo Study

Introduction In this study, we aimed to calculate dose enhancement factor (DEF) for gold (Au) and iron (Fe) nanoparticles (NPs) in brachytherapy and teletherapy, using Monte Carlo (MC) method. Materials and Methods In this study, a new algorithm was introduced to calculate dose enhancement by AuNPs and FeNPs for Iridium-192 (Ir-192) brachytherapy and Cobalt-60 (Co-60) teletherapy sources, using the MC method. In this algorithm, the semi-random distribution of NPs was used instead of the regular distribution. Diameters were assumed to be 15, 30, and 100 nm in brachytherapy and 15 and 30 nm in teletherapy. Monte Carlo MCNP4C code was used for simulations, and NP density values were 0.107 mg/ml and 0.112 mg/ml in brachytherapy and teletherapy, respectively. Results AuNPs significantly enhanced the radiation dose in brachytherapy (approximately 60%), and 100 nm diameter NPs showed the most uniform dose distribution. AuNPs had an insignificant effect on teletherapy radiation field, with a dose enhancement ratio of 3% (about the calculation uncertainty) or less. In addition, FeNPs had an insignificant effect on both brachytherapy and teletherapy radiation fields. FeNPs dose enhancement was 3% in brachytherapy and 6% (about the calculation uncertainty) or less in teletherapy. Conclusion It can be concluded that AuNPs can significantly increase the absorbed dose in brachytherapy; however, FeNPs do not have a noticeable effect on the absorbed dose