Future role of vitamin C in radiation mitigation and its possible applications in manned deep space missions: survival study and the measurement of cell viability

Astronauts will be exposed to both chronic space radiation and acute high doses of energetic radiation of solar particle events in long-term deep space missions. The application of radioprotectors in space missions has basic limitations such as their very short time window as well as their acute toxicity and considerable side effects. The aim of the present study was to investigate the potential radiation mitigation effect of vitamin C that is known as an effective antioxidant and free radical scavenger. One hundred twenty male Wistar albino rats weighing 250-300 g were randomized into the following study groups: I, control; II, Only exposure to gamma-radiation [LD50/30]; treated with a single dose of vitamin C, III, 1h before irradiation, IV, V and VI, 1h, 12h and 24 h after irradiation. Measurement of cell viability and proliferation was also performed by using MTT cell proliferation assay. The survival rate in animals received vitamin C 1h, 12h and 24h after irradiation were 55%, 60%, and 80%, respectively. The viability of cells in animals received vitamin C 1h, 12h and 24h after irradiation were 94.9%, 99.0%, and 100%, respectively. The viability of the cells in animals only exposed to gamma rays was 50.1%. These findings reveal that a single dose of vitamin C can potentially be used up to 24 hours after exposure to reduce the detrimental effects of high levels of ionizing radiation in cases such as the occurrence of currently unpredictable solar particle events

Rectal wall dose estimation in intracavitary brachytherapy: a preliminary comparison of an in-house rectal wire versus ICRU 38 recommendations

In intracavitary brachytherapy for gynecological cancers, various techniques are used to locate the anterior rectal wall nearest to the sources but there is no consensus on the best method to do so. This study aimed to compare a technique used routinely in some centers that employs a wire marker to locate the position of the maximum rectal dose point, versus the method recommended by the ICRU Report 38. In a preliminary prospective study on 34 intracavitary insertions for patients with cervical or endometrial cancer, treated at our center based on the Manchester system, the dose distributions were obtained from a treatment planning system following the input of scanned orthogonal anteroposterior and lateral radiographs. For each case, an in-house marked wire was inserted in the rectal lumen and the doses were calculated on several points along the wire seen on the radiographs, to obtain the maximum dose. For the same insertions, the ICRU method was also applied by considering the rectal wall hot spot as a point 0.5 cm posterior to the posterior vaginal wall [visualized on the radiographs by vaginal packing material containing contrast medium]. Averaged over all insertions, mean rectal wall hot spot dose calculated using the positional information obtained by the wire technique was lower by 28.6% than that given by the ICRU method [P < 0.001]. Our initial results add evidence to the suggestion that the wire technique underestimates the rectal wall hot spot dose significantly compared to the ICRU method

Production of a novel high strength heavy concrete using tourmaline and galena for neutron and photon radiation shielding

High density concrete is extensively used for efficient radiation attenuation in radiotherapy rooms and nuclear reactors. Over the past eight years, some efficient galena-based concrete samples for shielding X or gamma rays was produced. The goal of this study was to produce a novel high density concrete against neutron and photon radiations using tourmaline and galena. Attenuation of gamma photons was measured using a Farmer type ionization chamber with a standard [60]Co buildup cap on a Theratron[60] Co therapy unit. Neutron shielding characteristics were measured by using an Am-Be source. The MCNP4C radiation transport computer code was used to investigate the effects of various shield thicknesses on the attenuation of gamma-ray photons and neutrons. The concrete samples had a density of 4.0- 4.2 g/cm[3]. The compressive strength was 326 - 560 kg/cm2. The calculated value for Half Value Layer [HVL] of the tourmaline-galena concrete samples for 60Co gamma rays was 2.72 cm, which is much less than that of ordinary concrete [6.0 cm]. The MC-derived HVL for photons with the same energy was 2.77 cm, which is in a good agreement with the experimental data. Moreover, ToGa concrete had up to 10 times greater neutron attenuation compared to that of the reference concrete. Tourmalin-Galena Concrete opens a new horizon in economic and efficient gamma/neutron shielding in high-energy radiotherapy bunkers, nuclear power plants, and shielding of radioactive sources

fast model for prediction of respiratory lung motion for image-guided radiotherapy: a feasibility study

The aim of this work was to study the feasibility of constructing a fast thorax model suitable for simulating lung motion due to respiration using only one CT dataset. For each of six patients with different thorax sizes, two sets of CT images were obtained in single-breath-hold inhale and exhale stages in the supine position. The CT images were then analyzed by measurements of the displacements due to respiration in the thorax region. Lung and thorax were 3D reconstructed and then transferred to the ABAQUS software for biomechanical fast finite element [FFE] modeling. The FFE model parameters were tuned based on three of the patients, and then was tested in a predictive mode for the remaining patients to predict lung and thorax motion and deformation following respiration. Starting from end-exhale stage, the model, tuned for a patient created lung wall motion at end-inhale stage that matched the measurements for that patient within 1 mm [its limit of accuracy]. In the predictive mode, the mean discrepancy between the imaged landmarks and those predicted by the model [formed from averaged data of two patients] was 4.2 mm. The average computation time in the fast predictive mode was 89 sec. Fast prediction of approximate, lung and thorax shapes in the respiratory cycle has been feasible due to the linear elastic material approximation, used in the FFE model

comparative study on the increased radioresistance to lethal doses of gamma rays after exposure to microwave radiation and oral intake of flaxseed oil

Mobile phones, use electromagnetic radiation in the microwave range. On the other hand, there is only one report on radioprotective effects of flaxseed oil. The aim of this study was to investigate the effect of irradiation of rats with microwaves and/or treatment with flaxseed oil on the induction of adaptive response to a subsequent lethal dose [LD] of gamma rays. Eighty male rats were randomly divided into 6 groups of 13-15 animals. The animals in the 1[st] to 5[th] groups received microwave exposure, microwave+flaxseed oil [dissolved in olive oil], flaxseed [continued after LD], flaxseed, and olive oil. At day 5, all animals were whole-body irradiated with a previously reported LD 50/30 of 8 Gy gamma radiation. The 6th group [controls] received the same LD 50/30, but there was not any other treatment before or after the LD. No death event was observed during days 1-9 after LD irradiation in either group. At day 10, death events started in the 4[th] group. Thirty days after irradiation of the animals, the survival fractions for the control group, as expected, was 53.3% while there was no death event in the 1[st] group [survival rate of 100% in microwave-pretreated animals]. The survival fractions for the 2[nd] to 5[th] groups were 69.2%, 92.3%, 46.1%, and 61.5%, respectively. While these findings open new horizons in radiation protection, the radioresistance induced by microwave radiations emitted by a mobile phone may interfere with the outcome of any subsequent therapeutic application of photons or radioisotopes

Evaluation of the changes in the shape and location of the prostate and pelvic organs due to bladder filling and rectal distension

A steep dose gradient between prostate and organs at risk [rectum and bladder] is ideal in treatment modality, so prostate displacement and deformation due to bladder filling and rectal distension play an important role in critical organs dose. This study aims to evaluate the changes in the shape and location of the prostate and pelvic organs due to bladder filling and rectal distension. Three patients who referred for transrectal prostatic biopsy [Shahid Faghihi Hospital, Shiraz, Iran] with different prostate sizes were enrolled. A 1.5-Tesla MRI system [Avanto, Siemens, Germany] and an ultrasound system [Logiq 500, GE medical systems, USA] were used to collect images of patients prostate at different stages of bladder and rectum fullness. The mean displacement of the prostate after bladder filling in the supine and left decubitus positions along the Anterior-Posterior [AP] axis was posterior by 4.9 mm [range: 0.7-6.3 mm] and along the Superior-Inferior [SI] axis was inferior by 3.4 mm [range: 1.4-5 mm]. Prostate displacement in the Left-Right [LR] axis was negligible. The mean prostate displacement after rectal distension was anterior by 7.1 mm in the supine position, 5.1 mm anterior in the left decubitus position and along the SI axis was inferior by 2.5 mm in the supine and left decubitus positions. The maximum prostate deformation due to rectal distension and bladder filling in the supine position was as large as 3.2 mm, 1.9 mm and 1.2 mm in the AP, SI and LR directions respectively. While in the left decubitus position, it was 2.6 mm, 1.2 mm and 1.3 mm in the AP, LR and SI axis respectively. It is probably of importance to evaluate the influence of the changes in the shape and location of the prostate due to bladder filling, rectal distension and patient position in post-implant brachytherapy dosimetry. Using images of the patients in the left decubitus position with full bladder and distended rectum for planning a treatment are suggested

Production of a datolite-based heavy concrete for shielding nuclear reactors and megavoltage radiotherapy rooms

Biological shielding of nuclear reactors has always been a great concern and decreasing the complexity and expense of these installations is of great interest. In this study, we used datolite and galena [DaGa] minerals for production of a high performance heavy concrete. Datolite and galena minerals which can be found in many parts of Iran were used in the concrete mix design. To measure the gamma radiation attenuation of the DaGa concrete samples, they were exposed to both narrow and wide beams of gamma rays emitted from a cobalt-60 radiotherapy unit. An Am-Be neutron source was used for assessing the shielding properties of the samples against neutrons. To test the compression strengths, both types of concrete mixes [DaGa and ordinary concrete] were investigated. The concrete samples had a density of 4420-4650 kg/m[3] compared to that of ordinary concrete [2300-2500 kg/m[3]] or barite high density concrete [up to 3500 kg/m[3]]. The measured half value layer thickness of the DaGa concrete samples for cobalt-60 gamma rays was much less than that of ordinary concrete [2.56 cm compared to 6.0 cm]. Furthermore, the galena concrete samples had a significantly higher compressive strength as well as 20% more neutron absorption. The DaGa concrete samples showed good shielding/ engineering properties in comparison with other reported samples made, using high-density materials other than depleted uranium. It is also more economic than the high-density concretes. DaGa concrete may be a suitable option for shielding nuclear reactors and megavoltage radiotherapy rooms

Simulation of the shielding effects of an applicator on the AAPM TG-43 parameters of CS-137 Selectron LDR brachytherapy sources

The dose rate distribution delivered by a low dose rate [137]Cs pellet source, a spherical source used within the source trains of the Selectron gynecological brachytherapy system, was investigated using the MCNP4C Monte Carlo code. The calculations were performed in both water and Plexiglas and the absolute dose rate distribution for a single pellet source and the AAPM TG-43 parameters were computed. A spherical phantom with dimensions large enough [60 cm] was used to provide full scattering conditions. In order to score dose at different distances from the source centre, this sphere was divided into a set of 600 concentric spherical shells of 0.05 cm thickness. The calculations were performed up to a distance of 10 cm from the source centre. To calculate the effect of the applicator and dummy pellets on dose rate constant and radial dose function, a single pellet source was simulated inside the vaginal applicator, and spherical tally cells with radius of 0.05 cm were used in the simulations. The F6 tally was used to score the absolute dose rate at a given point in the phantom. The dose rate constant for a single active pellet was found to be 1.102 +/- 0.007 cGyh[-1]U[-1], and the dose rate constant for an active pellet inside the applicator was 1.095 +/- 0.009 cGyh[-1]U[-1]. The tabulated data and 5th order polynomial fit coefficients for the radial dose function along with the dose rate constant are provided for both cases. The effect of applicator and dummy pellets on anisotropy function of the source was also investigated. The error resulting from ignoring the applicator was reduced using the data of a single pellet. The results indicate that F[r, theta] decreases towards the applicator

Combined neoadjuvant chemotherapy and celecoxib in locally advanced breast cancer

Locally advanced breast cancer is a presentation form of cancer with poor prognosis. The optimal method of treatment for these cases remains unclear. In this trial, the role of low dose celecoxib combined with neoadjuvant chemotherapy in locally advanced breast cancer was evaluated. Fifty women with pathologically proven locally advanced breast cancer were enrolled. All patients received preoperative chemotherapy with CAF [Cyclophosphamide 600 mg/m[2], doxorubicin 60 mg/m[2], 5-FU 600 mg/m[2]] regimen. They were randomly assigned into two groups. The first group received oral celecoxib [100mg twice daily] concurrently with chemotherapy and the second group was offered placebo. Chemotherapy was administered every three weeks and celecoxib continued until one week before the surgery. The patients received an average of 3 months treatment. The size of breast mass was measured before each cycle of chemotherapy by a caliper. The pathologic response rate was the primary endpoint of the study. In this trial, 50 patients were eligible, of whom 44 were evaluable. There were 25 patients in the celecoxib group and 25 patients in the placebo arm. Two patients in each group developed metastasis during the treatment course and two patients in group one could not tolerate celecoxib and quit it, so they were excluded from the trial. There was no statistically significant difference in terms of partial or complete response [90.5% vs. 87.0%] between celecoxib and placebo groups. Histological type, grade and hormonal receptor were similar in the two groups. No significant association was observed between menstrual status, size of mass at presentation and response to celecoxib. This study suggests that the use of celecoxib with a dose of 100 mg twice daily combined with neoadjuvant chemotherapy does not improve response rate in locally advanced breast cancer

Production of an economic high-density concrete for shielding megavoltage radiotherapy rooms and muclear reactors

In megavoltage radiotherapy rooms, ordinary concrete is usually used due to its low construction costs, although higher density concrete are sometimes used, as well. The use of high-density concrete decreases the required thickness of the concrete barrier; hence, its disadvantage is its high cost. In a nuclear reactor, neutron radiation is the most difficult to shield. A method for production of economic high-density concrete with appropriate engineering properties would be very useful. Galena [PbS] mineral was used to produce of a high-density concrete. Galena can be found in many parts of Iran. Two types of concrete mixes were produced. The water-to-concrete [w/c] ratios of the reference and galena concrete mixes were 0.53 and 0.25, respectively. To measure the gamma radiation attenuation of Galena concrete samples, they were exposed to a narrow beam of gamma rays emitted from a cobalt-60 therapy unit. The Galena mineral used in this study had a density of 7400 kg/m[3]. The concrete samples had a density of 4800 kg/m[3]. The measured half value layer thickness of the Galena concrete samples for cobalt- 60 gamma rays was much less than that of ordinary concrete [2.6 cm compared to 6.0 cm]. Furthermore, the galena concrete samples had significantly higher compressive strength [500 kg/cm[2] compared to 300 kg/cm[2]]. The Galena concrete samples made in our laboratories had showed good shielding/engineering properties in comparison with all samples made by using high-density materials other than depleted uranium. Based on the preliminary results, Galena concrete is maybe a suitable option where high-density concrete is required in megavoltage radiotherapy rooms as well as nuclear reactors

Radiotherapy techniques for intracranial tumours

Intracranial tumours often require radiotherapeutic approaches that differ from other sites. Their specific requirements merit a specialized discussion. A brief review of radiotherapy techniques to treat intracranial tumours is presented with emphasis on the author's own experience and work, where appropriate. A clinical introduction is presented first followed by a description of both conventional and modern techniques. Examples from clinical practice are also given. The issues discussed include direct simulation, 2D and 3D treatment planning, the use of CT and other imaging modalities, field shaping and non-coplanar techniques. In the modern radiotherapy era, simple conventional techniques still have a role to play in routine clinical practice. As new technologies are introduced into relatively under-resourced centres, they should be used judiciously and appropriately to maximize benefit to the whole patient population

Measurement of the immobilisation efficacy of a head fixation system

In order to assign appropriate planning target volume [PTV] margins, each centre should measure the patient positioning deviations for their set-up techniques. At the Royal Marsden Hospital, UK, a conformal shell [cast] system is used when a stereotactic frame is not suitable. In this paper, we report on a series of measurements with the aim of obtaining the systematic and random components of positioning error when using the above-mentioned shell system. The verification protocol was based on orthogonal pairs of anterior-posterior and lateral electronic portal images [EPIs] used to check the isocentre position. The isocentre verification results of paediatric patients were analysed. A practical [off-line] patient set-up correction strategy had been used with the aim of reducing systematic errors. The verification protocol involved EPI acquisition on the first three fractions and then on a weekly basis. Additional images were taken if an isocentre movement was applied based on a 3 mm tolerance for a consistent 1D discrepancy. Four patients required isocentre corrections ranging between 2 mm and 4 mm. Following the offline corrections, the residual systematic errors in each direction were within 0.5 mm while the 1D random variation was about 1.0 mm. The head fixation system in conjunction with the correction strategy successfully kept the random and systematic positioning errors within an acceptable level well within the 3 mm tolerance. The measured components of positioning error can be used to define appropriate PTV margins

Comparison of MCNP4C, 4B and 4A Monte Carlo codes when calculating electron therapy depth doses

Monte Carlo simulation of radiation transport is considered to be one of the most accurate methods of radiation therapy dose calculation. There are different Monte Carlo codes for simulation of photons, electrons and the coupled transport of electrons and photons. MCNP is a general purpose Monte Carlo code that can be used for electron, photon and coupled photon-electron transport. In this study the MCNP4A, 4B and 4C have been compared when calculating electron beam doses in water. For simulating, the geometry and other parameters were the same for three codes. By choosing two energy indexing algorithm [ITS and MCNP], absorbed doses were scored in water. 10[6] Particles were followed in these three cases. MCNP4C and 4B gave different results compared to 4A when the ITS algorithm was used in 4B and 4C versions. There was a good agreement between versions 4B and 4C. For the energy spectrum, there were significant differences between these three versions in two planes. Because of new improvements in electron transport in 4C, this version is reliable for electron transport and also requires a shorter time than the two previous versions. These results, in addition to the practical measurements acquired with MCNP4B by other investigators, suggest that in electron transport the user should use the ITS indexing energy algorithm

How precise is manual CT-MRI registration for cranial radiotherapy planning

Manual fusion [MF] is a readily available image registration technique that does not require matching algorithms. The operator performs rigid-body transformations interactively. The precision of MF [as implemented on the Philips Pinnacle treatment planning system] was required for cranial CT-MR images used in radiotherapy planning for typical centrally located planning target volumes [PTVs]. A multi-stage MF procedure was developed which 11 observers followed to match the head contour, bones, soft tissues and contoured structures for 5 patient image-sets. Registration parameters were calculated by solving the transformation matrix following a consistent order of translations [T] and rotations [R]. The mean position of centre of each PTV averaged over all observers was used as the reference. The effect of misregistration on the PTV co-ordinates and the volume increase resulting from application of a margin for registration uncertainty were calculated. Mean intra- and inter-observer T/R SDs were 0.5mm/0.4, respectively. Mean intra- and inter-observer registration error and 1.1mm/1.0 [3D distance of each PTV centre from the mean position for all observers] was +/- 0.7 mm respectively, the latter reducing to 1.4 +/- 0.3 mm [1 SD] and 1.6 +/- 0.7 0.6 mm excluding the 3 least experienced operators. A subsequent 2 mm margin for misregistration on average increased the PTV volume by 27%. Moderately trained operators produced clinically acceptable results while experienced operators improved the precision. MF still has an important role in the registration of cranial CT and MR images for radiotherapy planning especially for under-resourced centers