hamid reza baghani

In current study, the relative biological effectiveness (RBE) values relevant to the various Iodine radioisotopes, have been assessed to compare the performance of the MCSD and GEANT4-DNA Monte Carlo codes at low energy regions. After the calculation of the Auger electrons energy spectrum, obtained from the Iodine radioisotopes including 123I, 124I, and 125I through the GEANT4 Monte Carlo code, the calculation of the RBE values was performed through the GEANT4-DNA extension by considering the B-DNA model. In addition, the RBE values were also estimated by the MCDS code in completely aerobic conditions. The results of this study showed that employing the GEANT4-DNA-option4 physics by GEANT4-DNA extension in the physical stage provides near results in comparison with MCDS code for the radiobiological assessments and RBE estimation. The obtained highest difference values in this study were related to the use of GEANT4-DNA-option2 physics which varies from 22.30% to 24.60% for the studied radioisotopes. Since double strand damages along the DNA molecule can eventually lead to the cell death, and due to the appropriable agreement between the calculated results of RBEDSB values through the MCDS and GEANT4-DNA codes, it can be deduced that the MCDS code provides accurate results for the radiation induced DNA damage.

In prostate cancer radiotherapy, due to the proximity of the prostate to the rectum, it can be affected by high radiation doses. It has been reported that about 70% of secondary cancers after prostate cancer radiotherapy occur in the bladder and rectum, which are exposed to direct radiation. Since prostate cancer radiotherapy may be accompanied by side effects, the aim of this study is to investigate the risk of secondary cancers after the radiotherapy of prostate cancer inside the outfield organs.

The dose volume histogram data relevant to 39 patients with prostate cancer (who were treated with 3-dimensional conformal radiotherapy technique in 2022 in Tehran) were extracted, and the uniform absorbed dose inside the sensitive tissues was calculated according to the gEUD concept. Then, the risks of secondary malignancies following prostate cancer radiotherapy were calculated using the model introduced by the BEIR report. Accordingly, the lifetime attributable risk values (LAR) were estimated based on the desired organs and patient age at exposure time through the calculation of Excess relative risk (ERR) and Excess absolute risk (EAR) values.

From the obtained results, the gEUD values for the rectum ranged from 51.04 Gy to 74.69 Gy and for the bladder from 27.22 Gy to 75.51 Gy. The maximum calculated risk values for the rectum and bladder were calculated to be 49.85% and 74.91%, respectively. Besides, a significant level of secondary cancer risk within the rectum and bladder was obtained for most of the studied patients. Furthermore, small values of secondary cancer risks were estimated for patients who were irradiated at older ages, and higher ones were obtained for patients who were irradiated at younger ages.

The results showed that there is a higher probability of developing secondary malignancies in the bladder than the rectum. The information obtained in this research can improve the performance of the treatment process, so that information about secondary cancers following radiation therapy for prostate cancer will ultimately help doctors design more effective and optimal treatment designs.

Absorbed dose enhancement due to the presence of high atomic number nanoparticles (NP)s has been estimated and modeled by Monte Carlo (MC) simulation methods. In the current study, two MC codes of MCNPX and EGSnrc codes were compared by calculation of secondary electron energy spectra and nano-scaled dose values around four types of spherical NPs.

The MC model was composed of a spherical nanoparticle with a diameter of 50 nm and mono-energetic sources of photons with energies of 30,60, and 100 keV. The secondary electrons emitted from the nanoparticle were scored on the nanoparticle surface and the delivered dose to water around the nanoparticle was tallied using concentric shells with a thickness of 25 nm. Four different elements were used as materials of NPs, including Gold, Bismuth, Gadolinium, and Hafnium.

Our results showed a considerable difference in the number of emitted electrons per incident photon between the two codes. There were also discrepancies between the two codes in the energy spectra of secondary electrons. Calculated radial dose values around NPs in nano-scale had a similar pattern for both codes. However, significant differences existed for some elements.

It can be concluded that the results of nano-scaled MC modeling for nanoparticle-based radiation therapy are dependent on the code type and its algorithm for electron transport as well as exploited cross-section libraries.

Prostate cancer is the most common and second leading cause of death among men in the world. Nowadays, radiotherapy has been known as one of the most affecting methods for prostate cancer treatment. Nevertheless, radiotherapy is accompanied by the concern of developing secondary cancers by the scattered radiation to the neighbor  organs at risk. Several studies have shown that secondary cancers after the radiotherapy of prostate cancer treatment, occur in tissues such as the bladder and rectum which have been exposed to direct or indirect radiations. Therefore, this review study aimed to evaluate the influencing factors for developing secondary cancers after the radiotherapy of prostate cancer. To access the previously validated published studies, Persian and English keywords such as prostate cancer, secondary cancers, radiotherapy and organs at risk have been searched in ISID, Google Scholar, Science Direct, PubMed, and World Health Organization, between 1997 and 2021. Totally 246 pieces of literature have been selected which finally, by ignoring the similar and overlapping studies, only 40 studies were reviewed. In the present study, the most affecting factors for developing secondary malignancies including the anatomical status changes, dose variations, smoking and the impact of the various treatment techniques, have been studied. The results of the reviewed studies showed a reduction of secondary cancer risks with performing the modern modalities such as proton therapy to treat prostate cancer. Moreover, organ movements and anatomical status changes which vary from one patient to others, have been reported to make a significant difference in the relative risk of secondary cancers. It has been shown that smoking may increase the risk of secondary cancers after the radiotherapy of prostate cancer, so radiotherapy and smoking may cause genetic mutations. Despite the advantages of radiotherapy for prostate cancer treatment, developing secondary cancers after the radiotherapy should not be ignored. Assessments of the affecting factors for secondary cancers after the radiotherapy of prostate cancer require social and comprehensive studies which can result in an accurate modality with fewer side effects.

The considerable growth of 3D printing technology in recent years has led to the application of this emerging technology in many medical fields, in which recently performed studies have shown the special importance of this technology which can enhance the results of the treatment method. Since, surgery is one of the main modalities to treat patients, the advent of 3D printing technology in surgery and the creation of different patient organs with 3D printers, improve the surgeon's performance. Hence, the accuracy and quality of the surgery can be enhanced. The aim of this study was to review the current statues and the applications of the 3D printing technology in surgery.

By searching the indexed articles in Persian and Latin databases, Scopus, PubMed, Science direct, Scholar, 34 studies were reviewed.

3D printing applications in surgery: Generally, the ability to generate a physical object with complex structures from a digital model has been introduced as the 3D printing technology which offers many advantages over the traditional manufacturing. The most important advantage of 3D printing technology is the ability to produce objects based on individual needs in which can reduce the costs of their production. Furthermore, complex preoperative procedures can be practiced. In other words, 3D printed models allow physicians to become familiar with medical procedures which possible problems created during the operation, can be identified before the operation. This modern technology generally includes three main steps to generate 3D objects from imaging data. The first step is the acquisition of image data. Then, the interest region is extracted which is termed as the segmentation. Finally, the digital data is transferred to the 3D printers to produce the 3D object.  For 3D model production, printer selection highly depends on speed, accuracy, cost, and availability of the printing materials. Recent advances in 3D printing technology have made it possible to use various biocompatible materials such as titanium and degradable polyesters to produce 3D models. Complex surgeries require more precise visual understanding before the surgery to ensure about the success of the treatment. In this regard, 3D printing technology can be a promising way to produce faster and cheaper models. In addition, this modern technology enables producers to produce highly specialized products for a wide range of patient organs. Applying a physical model results in better performance and greater visual perception about the desired treatment area, which can significantly reduce the side effects during surgery. Since a large contribution of the surgical process can be performed outside the operating room hence, 3D printed models can reduce the operation time. In fact, before the operation, surgeons will have enough time to make decisions, evaluate solutions and focus on other key elements during the operation. So, based on the basic role of 3D printing technology in surgery, the purpose of the present review is to investigate the current state of 3D printing technology and its clinical application in surgery for the construction of various 3D organs via medical imaging data. In this paper, some applications such as maxillofacial, spinal, liver, etc., are briefly discussed. Maxilla-facial and cranial facial reconstruction are the complex procedure which have been one of the first and most proven applications of 3D printing in the field of surgery to correct the facial deformities after the tumor resection. In this method with the application of 3D printers, at first, a 3D model of the desired anatomy is prepared to reduce a significant amount of time for linking the titanium plates to transplant adjacent bones (while the patient is anesthetized). Also, the production of titanium implants using the 3D printers will result in a very precise fit with the target tissue, the risks of maxillofacial surgery can be reduced.The use of 3D printing applications before or during complex surgeries like congenital heart defects has been reported in several studies. Since, acquiring to the real anatomical structures in patients with complex congenital defects, are sometimes unpredictable, treatment planning and surgical decision-making require a thorough understanding of three-dimensional anatomy. Therefore, the 3D printing technique, as a widely used method in all medical fields can overcome the defects of common preoperative imaging, especially in cardiovascular surgery.The other application of 3D printing technology includes spinal surgery in which due to the complex anatomy of the spine and the delicate nature of the surrounding structures, 3D printers will improve preoperative planning and increase the accuracy during the surgery.Liver surgery can be another suitable candidate for performing 3D printing technology to create 3D printing models. The two main applications of 3D printing technology in this field include training or necessary planning for surgery and liver functional cell printing through bio-printing technology that can be used in the study of liver disease and pharmaceutical research.Renal tumor resection is the other example of 3D printing applications in which 3D models have an exclusive role to enhance the accuracy of renal surgery. The 3D printed models can accurately display three-dimensional spatial relationships between different anatomical and pathological structures. Three-dimensional printed kidney models may also facilitate interdisciplinary communication and decision-making about the management of patients undergoing renal surgery.  In the field of renal surgeries, employing of 3D printed models plays a specific performance to train young surgeons which consequently increases the practical skills of surgeons which can accurately visualize the anatomical and morphological relationship compared to volumetric imaging.The obtained results of performed studies in the field of 3D printing show the potential significance of this technology in surgery which can lead to improvement of therapeutic outcomes. Since the printed models by 3D printing technology have an appropriate fit to the anatomy, the use of these models can reduce the associated errors during surgery.It is worth noting that despite the valuable advantages of this technology, some disadvantages such as limited printing size and costly printing process can be discussed which many studies try to address the deficiency of 3D printing technology in clinical applications. The cost of 3D printed models varies according to the type of performed printing method and applicable software which requires specialized users. The main mentioned costs for 3D model creation include hardware, software, and printed materials. In the future, the production costs of 3D models would be likely reduced in which the use of 3D models would become more traditional in common clinical operation. The 3D printed physical models are based on medical imaging which are prone to errors during the imaging procedures. Hence, increasing the accuracy of creating printed models requires improving the clinical imaging methods. Generally, with the advances in this modern technology, faster, cheaper, and more accurate models can be produced.

Beam shaper applicator is one of the dedicated applicators for intraoperative electron radiotherapy which is usually employed for large tumors irradiation. Due to the high weight and impossibility of direct placement on the patient’s body, a significant air gap exists between the applicator and patient. Therefore, knowing the effective position of electron source (SSDeff) is quiet essential to correct the applicator output for this air gap effect and deliver an accurate prescribed dose to the patient. The current research aims to determine the SSDeff for all produced square fields by beam shaper applicator at different electron energies using Monte Carlo (MC) simulation.

At first, the head of LIAC accelerator in conjunction with beam shaper applicator was simulated by MCNPX MC code and then, the validity of the simulated model was evaluated through comparing the calculated percentage depth dose (PDD) curves at different field sizes and energies with the corresponding measured ones. After verifying the simulated model, the SSDeff was determined for different field sizes and electron energies using inverse square law (ISL) method.

The obtained results showed that the SSDeff is a function of electron energy and field size. Dependency of SSDeff  on field size variations was much more than variations of electron energy. Generally, the SSDeff increments with either increasing the field size or electron energy.

The determined SSDeff values for the electron beam of the beam shaper applicator at the current study, can be applied to correct the electron beam output in clinical practice.

Radon is a natural radioactive gas that easily enter to respiratory tract and cause considerable biologic damages. The main objective of this study was to determine the dose from the alpha and gamma radiations of radon decay chain products in trachea tissue using Monte Carlo simulation.

At first a trachea-equivalent cylindrical phantom was simulated by MCNPX Monte Carlo code. Then, dose profiles from alpha and gamma-emitter progenies were separately calculated. The daughter radionuclides were considered as suspended particles with uniform distribution inside the trachea inner volume.

The results showed that the received dose by trachea in alpha decay is considerably higher than that of gamma decay. The maximum administered dose by alpha decay was 1.72×10-16 Gy/decay. 218Po was had the highest dose among the studied alpha emitter daughter nuclides. The maximum administered dose by gamma decay was also equal to the 17.55×10-19 Gy/decay, where 214Pb and 214Bi had almost the same contribution in calculated dose.

The daughter radionuclides from radon decay chain, especially alpha emitter products of 218Po and 214Po, can be considered as a serious danger viewpoint to the internal exposure. These daughter nuclides can attach to the inner wall of trachea and remain in the respiratory system for long periods of time which can cause to the continuous exposure of trachea. Reducing the biologic effects of these internal radiation source requires especial schemes in order to avoid entering the radon and its radioactive daughters to human respiratory system, as much as possible.

Breast cancer is considered as one of the main causes of cancer death in women. Early diagnosis and treatment, especially by modern technologies play major roles in management of breast cancer. Radiation therapy is known as one of the main treatment options for breast cancer. Nowadays, 3D printing technology is also used to rapidly construct objects with high quality. Many studies have shown the positive effects of this technology on the results of cancer radiation therapy. The aim of this study was to review the application of 3D printing technology in treatment of breast cancer by mega voltage electron and photon beams, including bolus, applicators, immobilizer devices, and compensators. Creating personalized treatment devices by 3D printing technology reduces treatment errors, therefore, the prescribed dose is increased in the treatment area and subsequently improves treatment outcomes. In spite of the valuable benefits of this technology, there are some disadvantages such as size limitations and the number of materials used for printing. Indeed, recent studies are trying to fix the shortcomings of 3D printing technologies in clinical applications.

Nowadays, 3D printing technology is used for rapid prototyping of high quality objects, so that this technology plays an important role in the modern fields of medicine, especially in surgery, radiation therapy, radiology and etc. Generally, the process of creating a physical object from a digital model is considered as a simple definition of 3D printing. Compared to conventional printers, 3D printers create a physical 3D model of the desire target. Creation of a model by 3D printer requires a digital 3D model which can be obtained by scanning a set of 3D images or drawing them using CAD design software, as well as using computed tomography (CT) data or magnetic resonance imaging (MRI) imaging. Then, this digital model is sent to the printer and finally, a 3D layer-by-layer model is created. The whole mentioned process is called as fast prototyping or 3D printing. Since, personal radiotherapy is introduced as one of the main modality for the treatment and management of various cancers, requires precise details to improve the performance of the employed modality. Todays, 3D printers are able to produce a realistic model of complex geometries, so 3D printing technology can be a complementary and promising method for treating patients and making specific equipment for them, especially in radiotherapy. The dramatic growth of 3D printing technology in various fields of medicine in recent years, has led to the introduction of new applications of this technology in these fields, so that the importance of this technology in improving the performance of treatment modalities, has been reported in several recent studies. The use of 3D printing technology will reduce the cost of radiation therapy which as a promising method, can enhance the efficacy of employed modality. Performed studies have shown that 3D printing technology is a fast, practical and inexpensive method for delivering a uniform dose to the target volume while protecting healthy tissues in the radiation field. Furthermore, this technology reduces patient discomfort which can provide specific radiotherapy devices to each patient. The employment of 3D printed devices, based on the anatomical features of each patient in radiotherapy, such as bolus and fixed devices can reduce daily uncertainty (in radiotherapy) and also increase the accuracy of treatment. 3D printing technology enables users to employ various materials for better performance of radiotherapy method. So far, several materials have been used and evaluated to produce the desired 3D object via the 3D printing technology, including polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol (PETG), thermoplastic elastomers (TPE), Polyamide (PA, also called nylon), thermoplastic polyurethane (TPU), and polyvinyl acetate. The accuracy and efficacy of 3D printing technology highly depends on the performed materials for creation of the 3D objects. PLA and ABS have been introduced as the most common performed materials in 3D printing technology. PLA is a type of odorless plastic polymer which can be used in many industries, such as biodegradable implants and food packaging. ABS is more resistant than PLA which can tolerate the high temperatures. PA material is flexible, very cohesive and very resistant as a plastic polymer as well. The most common use of TPE has been introduced in the construction of flexible objects which with the use of this material objects can be created in a short time. PETG materials are a combination of PET and glycols with different concentrations. All the mentioned materials are available in the form of filaments with diameters of 1.75 mm and 3 mm. Performed investigations in our present work have shown that patient-specific devices can be generated from volumetric CT images or MRI data by 3D printing. In fact, 3D printing technology has great potential for improving the accuracy and efficiency of personal radiotherapy which this technology offers a relatively inexpensive and effective method to produce devices based on individual anatomy in radiotherapy. The practical usage of the 3D printing technology in radiation therapy can improve treatment outcomes and reduce treatment error which the weaknesses of traditional radiotherapy methods can be eliminated. Due to the advantages of this new method, the main aim of present review is to introduce some applications of 3D printing technology in radiotherapy, as a new approach in this therapeutic method, such as bolus, phantoms, brachytherapy applicators, filters, patient fixation devices, compensatory blocks and grid blocks. In most of the performed studies, the advent of 3D printing technology in the field of radiotherapy has been reported as a cost-effective and accessible method so that more practical parts can be produced. Performed studies also showed that the favorable agreement between the printed model in terms of matching the unique body geometry of each patient will reduce the side effects of radiation to healthy tissues..

Internal exposure to radon gas progeny can lead to serious biologic damages to the lung tissue. The aim of this study was to evaluate the absorbed dose by lung tissue due to the exposure from short-lived radioactive products of radon (222Rn) decay using Monte Carlo simulation.

A lung equivalent phantom including 64 air sacs was simulated by MCNPX code. Then, the absorbed dose from short-lived radioactive products of radon decay chain including 218Po, 214Po, 214Pb and 214Bi was calculated for both suspended and deposited states of daughter nuclides inside the lung.

The results showed that alpha decay has more contribution to the lung absorbed dose in comparison with the beta and gamma decay. Furthermore, the received dose by the lung was higher when the radon progenies were deposited inside the lung so that the maximum received dose to lung was 100 times higher than that of calculated in suspended state.

Short-lived daughter radionuclides of radon decay chain, especially alpha emitter products, can be considered as dangerous internal radiation sources. The biological effects of these daughter radionuclides is more severe when are suspended inside the respiratory system.

Context: Intraoperative radiotherapy (IORT) is an accepted standard treatment for early stages of breast cancer in the selected cases. This is proven in two large clinical trials including ELIOT and TARGIT-A ones, which are based on high energy electron beam and low kV X-ray energy, respectively. Published results of two trials aimed at evaluating the local recurrence as the final outcome. In ELIOT study, the local recurrence rate is 4.4% versus 0.4% in patients, who received IORT and External Beam Radiotherapy (EBRT), in comparison to 3.2% and 1.3% in TARGIT-A trial. These differences need to be further evaluated regarding the efficacy and beneficence of IORT. The aim of this study is to further analyze the data of these two trials to confirm the strategy of IORT in breast cancer as boost or radical modality. Evidence Acquisition: Two main breast IORT trials were considered in this study. To this end, a computerized search was performed through MEDLINE, PubMed, PubMed Central, ISI web of knowledge, and reference list of related articles. All of the published data from these trials were gathered and their subjects were analyzed and compared. Statistical analysis revealed that in patients with matching clinical, pathological, and biological profiles in both trials, radical IORT using either electron or low kV X-ray is effective and acceptable. It seems that in patients with low risk factors, IORT is more effective than EBRT. Patient selection according to America Society of Radiation Oncology or European Society of Radiation Therapy classification guidelines confirmed that the local recurrence rate of ELIOT in low risk patients, similar to TARGIT, was less than 1.9%. We compared the ELIOT and TARGIT-A trial documents and found all of similarities and differences referred to these two trials recommend, using IORT for selected cases of breast cancer with at least non inferiority in Disease free survival (DFS) and overall survival (OS) as well as superiority in cosmetic, non-breast cancer death, and more.

Environmental and occupational human exposure from neutron source can lead to the serious biologic effects. The aim of this study is to evaluate the cancer incidence risk for various human organs at different neutron dose levels due to exposure from an Americium-241/Beryllium (Am-241/Be), a standard neutron source for calibration purposes.
Material and We measured ambient dose equivalent H*(10) at different distances from Am-241/Be mixed neutron source by Berthold LB 6411 detector and determined cancer incidence risk for different organs of both male and female subjects at different neutron exposure levels by BEIR VII model. Exposure age had a reverse impact on cancer incidence risk of different organs. We found that as H*(10) increases, cancer incidence risk increments as well. Colon (for men) and bladder (for women) had the highest sensitivity to neutron exposure, while prostate and uterus showed the lowest risk of cancer incidence among male and female subjects, respectively. Older exposed persons are at a lower risk of cancer incidence. The risk of cancer incidence for various organs is considerably associated with gender, such that radiation sensitivity of female organs was higher at all the measured neutron dose levels.

The accurate dose delivery in intraoperative radiotherapy (IORT) tightly depends on the precision of measured dose by the ion chamber. Output factor (OF) measurement of dedicated intraoperative electron radiotherapy (IOERT) accelerators using ion chamber faces some technical challenges including determination of Ksat.
The goal was to evaluate the performance of ethanol chlorobenzene (ECB) dosimeter in measuring the OF of intraoperative electron beam and to compare the results to those of ionometric dosimetry and Monte Carlo simulation. Consequemtly we determined the Ksat of employed ion chamber through comparison of the ECB response to ion chamber.
LIAC dedicated accelerator (LIAC Sordina SpA, Italy) was used for irradiation. To calculate the Ksat, ECB and Advanced Markus chamber were placed at the depth of maximum dose for different energies of LIAC accelerator. Then, Ksat was calculated through comparison of the obtained results. To measure the OF of electron beam, ECB was placed at the depth of maximum dose for each combination of energy/applicator size, and the absorbed dose was determined. Obtained results were compared to those of Advanced Markus chamber and Monte Carlo simulation.
The results of Ksat measurement showed that there is a very good agreement between the practically obtained Ksat and theoretical values determined by Laitano formalism at different energies (the maximum difference between the results was lower than 1%). The results of ECB OF measurement were in accordance to the results of ionometric dosimetry and Monte Carlo simulation (the maximum difference between the results was about 1.5% and 1.7%, respectively).
Based on the results, it may be concluded that the ECB dosimeter could be considered as an accurate tool for both OF measurement of intraoperative electron beam and cross calibration of employed ion chambers for absolute dosimetry (determination of the Ksat).

Background and Dose calculations in trachea HDR brachytherapy treatment planning systems are greatly based on TG-43 protocol in which, all materials including air inside trachea are treated the same as water. The aim of this study was to survey the effect of air on dose calculations of Flexiplan treatment planning system in trachea HDR brachytherapy.
To evaluate the effect of air inhomogeneity, a neck-equivalent plexiglass cylindrical phantom was used. Dose measurement was carried out by EDR2 film. Treatment planning and irradiation were performed using Flexiplan software and Flexitron brachytherapy system, respectively.
The results showed that considering the air inside trachea as water increases the absorbed dose by 12% which can lead to increment of patient dose.
A significant difference was seen between dosimetry results in the two conditions. Therefore, taking the air similar to water has a considerable effect on dose calculations of trachea HDR brachytherapy and accuracy of treatment plan performed.

Background and Beam shaper is a type of applicator used in conjunction with the intraoperative electron radiotherapy. This study aimed at quantitative evaluation of the photon contamination of this applicator using Monte Carlo simulation.
In this experimental study, at first the head of LIAC accelerator was simulated along with the beam shaper applicator using MCNPX Monte Carlo code. Validity of the simulated model was evaluated by comparing the percentage depth dose curves obtained by Monte Carlo simulation and practical dosimetry. Finally, the photon contamination at different clinical field sizes and electron energies was quantitatively determined.
The results showed that by increase in field size, the photon contamination of the beam shaper applicator was considerably decreased. Furthermore, increment of electron energy could increase the photon contamination.
Increasing the photon contamination at the phantom surface by increment of electron energy and decrement of field size can be attributed to increasing the probability of electron interaction with the steel blades of the beam shaper and production of bremsstrahlung radiation at higher energies. Due to the photon contamination, employing the beam shaper applicator can increase the surface dose.

125I is one of the important sources frequently used in brachytherapy. Up to now, several different commercial models of this source type have been introduced to the clinical radiation oncology applications. Recently, a new source model, IrSeed-125, has been added to this list. The aim of the present study is to determine the dosimetric parameters of this new source model based on the recommendations of TG-43 (U1) protocol using Monte Carlo simulation.
The dosimetric characteristics of Ir-125 including dose rate constant, radial dose function, 2D anisotropy function and 1D anisotropy function were determined inside liquid water using MCNPX code and compared to those of other commercially available iodine sources.
The dose rate constant of this new source was found to be 0.983.015 cGyh-1U-1 that was in good agreement with the TLD measured data (0.965 cGyh-1U-1). The 1D anisotropy function at 3, 5, and 7 cm radial distances were obtained as 0.954, 0.953 and 0.959, respectively.
CONCLUISON: The results of this study showed that the dosimetric characteristics of this new brachytherapy source are comparable with those of other commercially available sources. Furthermore, the simulated parameters were in accordance with the previously measured ones. Therefore, the Monte Carlo calculated dosimetric parameters could be employed to obtain the dose distribution around this new brachytherapy source based on TG-43 (U1) protocol.

With the development of science and technology in the medical field and need more than ever to accuracy and quality of treatment has been causer increase different radiotherapy methods. Almost the past two decade’s intraoperative radiation therapy (IORT) as one of the new techniques used to treat cancer patients. One of the problems with this method is obtaining accurate dosimetry, because neither before nor after surgery ray images taken from the area of patient data do not match exactly. Therefore, dosimetric characteristics for intraoperative dedicated radiation therapy accelerators in comparison of conventional accelerators are difficult. The main objective of this study was to investigate the LIAC head a light and portable intraoperative radiation therapy accelerator and dosimetry calculate its features. For this purpose, the LIAC head was simulated using Monte Carlo (MCNP). Then the percentage depth dose curves obtained for reference applicator (10 cm) in all accelerator energies using experimental measurements, simulation model was validated. All experimental measurements were done by 12MeV models of LIAC accelerator. Finally, some dosimetric parameters such as maximum absorbed dose (Dm), maximum depth dose (dm), R50, practical range (Rp), dose profile and other dosimetric parameters evaluated for reference applicator in the all LIAC electron beam energies.The results of this work show that the LIAC accelerator is designed for intraoperative radiation therapy method.

Low dose rate brachytherapy sources have been widely used for interstitial implants in tumor sites, particularly in prostate. Dosimetric characteristics of a new IrSeed 125I brachytherapy source have been determined using the LiF thermoluminescent dosimeter (TLD) chips. Dose rate constant, radial dose function, and anisotropy function around the IrSeed 125I source were measured in a plexiglass phantom using TLD-100 chips. A plexiglass slab phantom with dimensions of 30×30×7.3 cm3 was used to measure dose distribution around the source. Dose rate constant was measured to be equal to 0.965±0.006 cGyh-1U-1. Radial dose function, anisotropy function, and geometry function have been presented as tabulated data for the IrSeed source. Basically, the dosimetric parameters presented here for this new IrSeed source have clinical and treatment planning applications.

Interaluminal brachytherapy is one of the important methods of esophageal cancer treatment. The effect of applicator attenuation is not considered in dose calculation method released by AAPM-TG43. In this study, the effect of High-Dose Rate (HDR) brachytherapy esophageal applicator on dose distribution was surveyed in HDR brachytherapy.A cylindrical PMMA phantom was built in order to be inserted by various sizes of esophageal applicators. EDR2 films were placed at 33 mm from Ir-192 source and irradiated with 1.5 Gy after planning using treatment planning system for all applicators.The results of film dosimetry in reference point for 6, 8, 10, and 20 mm applicators were 1.54, 1.53, 1.48, and 1.50 Gy, respectively. The difference between practical and treatment planning system results was 0.023 Gy (<2.7%), on average.Due to the similar practical results for different esophageal applicators, it can be concluded that attenuation properties of applicator wall doesnt have a significant difference with water and therefore the Flexiplan treatment planning system accuracy is further confirmed.

Orthogonal radial fields are those in which the central axes are perpendicular to each other. An example of these orthogonal fields is the set of craniospinal orthogonal fields that are used for radiotherapy of medulloblastoma. Craniospinal radial fields consist of two parallel-opposed fields for brain exposure and one or two posterior spinal fields for spinal cord exposure. The main problem in using these combinative fields is the overlap of radial fields, where they adjoin. Therefore, adjusting radial fields in craniospinal radiotherapy is of remarkable significance and can outstandingly affect the reduction of the side effects due to radiotherapy. In doing so, two different setups were used for craniospinal radiotherapy, and by using dosimetry in each adjustment in the junction region between brain and upper spine fields and in organs at risk, the results of the two adjustments were compared. Each one of these two setups was separately performed on a Rando phantom. In the first setup, the arrangement of radial fields was performed without the rotation of the treatment bed and the collimators of the brain fields. In the second setup, the arrangement of radial fields was performed using the rotation of the treatment bed and the collimators of brain fields. For dosimetry, GR-200 TLDs were used. For radiotherapy, a varian linac (2100 C/D Model) was used. The results of dosimetry in the brain CTV, junction of brain and upper spine fields, thyroid and heart in the first setup were equal to 105, 168, 46 and 44 cGy, respectively, and in second setup, 106, 140, 48 and 44 cGy, respectively. Absorbed dose to the testes in both setups was negligible. Discussion and The results of dosimetry in both setups showed that angling the bed and the collimators for the brain fields prevents the overlap of radial fields and reduces the side effects due to radiotherapy.