Assessment of an Unshielded Electron Field Diode Dosimeter for Beam Scanning in Small-to Medium-Sized 6 MV Photon Fields

Abstract Introduction Radiotherapy planning systems require many percentage depth dose (PDD) and profile measurements and there are various dosimeters that can be used to obtain these scans. As dose perturbation is particularly troublesome in smaller photon fields, using a low-perturbation, unshielded electron field diode (EFD) in these fields is of interest. The aim of this work was to investigate the suitability of an unshielded diode for beam scanning in 3×3 cm 2 , 5×5 cm 2 , and 10×10 cm 2 , 6 MV fields. Materials and Methods An EFD was used for all the scans. For comparison, in profile measurements, a tungsten-shielded photon field diode (PFD) was also used. PDDs were measured using the PFD and an RK ionization chamber. Results Very good agreement (0.4%) was found between the PDDs measured with EFD and PFD for the two larger fields. However, the difference between them exceeded 1.0% slightly for the smallest field, which may be attributed to the effect of the larger PFD perturbation. The RK chamber PDDs around 10 cm depth were 1-2% lower than those measured with the diodes. There was good agreement (<1 mm) between EFD-and PFD-measured penumbra widths. Conclusion The EFD generally agrees well with the PFD and may even perform better in smaller fields

Dosimetric verification of the Elekta motorized wedge

Elekta linear accelerator is equipped with a motorized wedge which produces the wedge angles of less than 60° continuously by the combination of a wedged field and an open field with appropriate proportions. The effective wedge angles for various field sizes and depths were calculated using an analytical formula and a 2-D array detector data. The validity of the effective wedge angles has been done by determining wedge angles in accordance with ICRU-24. The effect of the field size on the wedge angle and wedge factor was investigated for motorized wedge. The maximum difference between planned and measured angles was found to be about 10̊. The planned dose for different wedge angles and field sizes compared with measured doses and their differences were found to be less than 3%. The calculating wedge factor throughout linear interpolation method for all field sizes from a few selected measurements had been proved for physical wedge beforehand. This method was applied to obtain the wedge factors with field size and compared with measured data for motorized wedge. The errors were in agreement with ICRU proposed error and less than treatment planning system error. The linear relation between wedge angle and output factor and depth were investigated and the linear interpolation method was proved to calculate wedge angle for any output factor and depth. 

Medical image registration using unsupervised deep neural network: A scoping literature review

In medicine, image registration is vital in image-guided interventions and other clinical applications. However, it is a difficult subject to be addressed which by the advent of machine learning, there have been considerable progress in algorithmic performance has recently been achieved for medical image registration in this area. The implementation of deep neural networks provides an opportunity for some medical applications such as conducting image registration in less time with high accuracy, playing a key role in countering tumors during the operation. The current study presents a comprehensive scoping review on the state-of-the-art literature of medical image registration studies based on unsupervised deep neural networks is conducted, encompassing all the related studies published in this field to this date. Here, we have tried to summarize the latest developments and applications of unsupervised deep learning-based registration methods in the medical field. Fundamental and main concepts, techniques, statistical analysis from different viewpoints, novelties, and future directions are elaborately discussed and conveyed in the current comprehensive scoping review. Besides, this review hopes to help those active readers, who are riveted by this field, achieve deep insight into this exciting field

A Preliminary Study on the Estimation of the Number of Cancer Patients Eligible for Hadron Therapy in Iran and Fars Province

Hadron therapy (HT) with protons and carbon ions is an advanced radiotherapy technique. As the first report addressing this topic, the present study aimed to estimate the number of patients eligible for HT in Fars province and the whole of Iran. The data were collected through direct inspection of medical records of the patients treated at the Radiotherapy Department, Namazi Hospital, Shiraz, Iran in 2014. The patients who were treated with external-beam radiotherapy and declared to be a resident of Fars province were extracted from the medical records. After classification based on appropriate indications and factors, the number of eligible patients in Iran was calculated by scaling (Iran: Fars population). Of the 2,932 medical records, 1,943 patients were treated with external-beam radiotherapy, among which 1,536 were from Fars. The total number of patients eligible for HT in Fars was >351 cases/year (22.9% of the treated patients). The cancer site distribution of the eligible Fars residents was central nervous system primary tumors (n=31), brain metastases (n=64), eye (n=7), head and neck (n=28); thyroid (n=4), lung (n=17), breast (n=56), esophagus (n=5); pancreas (n=5), gastric (n=32), liver and bile duct (n=0), rectum and anus (n=26); prostate (n=27), bladder (n=8), cervix (n=6), soft tissue (n=17); kidney (n=1), Hodgkin lymphoma (n=9), non-Hodgkin lymphoma (n=4), and bone metastases (n=4). A total number of 5,756 cases/year was estimated for the entire country. Considering the experiences of other countries, these results suggest that establishing at least two HT centers (covering the northern and southern parts of Iran) is justified based on the total number of patients. Further accurate estimations and cost evaluations are recommended

Modelling the transport of optical photons in scintillation detectors for diagnostic and radiotherapy imaging**The authors declare equal leadership and contribution regarding this review.

Computational modelling of radiation transport can enhance the understanding of the relative importance of individual processes involved in imaging systems. Modelling is a powerful tool for improving detector designs in ways that are impractical or impossible to achieve through experimental measurements. Modelling of light transport in scintillation detectors used in radiology and radiotherapy imaging that rely on the detection of visible light plays an increasingly important role in detector design. Historically, researchers have invested heavily in modelling the transport of ionizing radiation while light transport is often ignored or coarsely modelled. Due to the complexity of existing light transport simulation tools and the breadth of custom codes developed by users, light transport studies are seldom fully exploited and have not reached their full potential. This topical review aims at providing an overview of the methods employed in freely available and other described optical Monte Carlo packages and analytical models and discussing their respective advantages and limitations. In particular, applications of optical transport modelling in nuclear medicine, diagnostic and radiotherapy imaging are described. A discussion on the evolution of these modelling tools into future developments and applications is presented

Medium-Term Stability of the Photon Beam Energy of An Elekta CompactTM Linear Accelerator Based on Daily Measurements of Beam Quality Factor

Introduction In this study, we aimed to assess the medium-term energy stability of a 6MV Elekta CompactTM linear accelerator. To the best of our knowledge, this is the first published article to evaluate this linear accelerator in terms of energy stability. As well as investigating the stability of the linear accelerator energy over a period of several weeks, the results will be useful for estimation of the required tolerance values for the beam quality factor (BQF) of the PTW QUICKCHECK weblineTM (QCW) daily checking device. Materials and Methods Over a 13 week period of routine clinical service, 52 daily readings of BQF were taken and then analyzed for a 10×10 cm2 field. Results No decreasing or increasing trend in BQF was observed over the study period. The mean BQF value was estimated at 5.4483 with a standard deviation (SD) of 0.0459 (0.8%). The mean value was only 0.1% different from the baseline value. Conclusion The results of this medium-term stability study of the Elekta Compact linear accelerator energy showed that 96.2% of the observed BQF values were within ±1.3% of the baseline value. This can be considered to be within the recommended tolerance for linear accelerator photon beam energy. If an approach of applying ±3 SD is taken, the tolerance level for BQF may be suggested to be set at ±2.5%. However, further research is required to establish a relationship between BQF value and the actual changes in beam energy and penetrative quality

Optimization of Beam Orientation and Weight in Radiotherapy Treatment Planning using a Genetic Algorithm

Introduction: The selection of suitable beam angles and weights in external-beam radiotherapy is at present generally based upon the experience of the planner. Therefore, automated selection of beam angles and weights in forward-planned radiotherapy will be beneficial. Material and Methods: In this work, an efficient method is presented within the MATLAB environment to investigate how to improve the dose distributions by selecting suitable coplanar beam angles and weights for the beam. In the beam angle and weight selection algorithm, the optimal beam angles and weights correspond to the lowest objective function value of the dose distributions of each group of candidate beams. Optimal weights and angles reach a balance between all the objectives. In this work, we used a genetic algorithm and adopted a real-number encoding method to represent both beam weights and angles with an assignable number of repetitions. For the evolution of this algorithm, we used both monophasic and biphasic methods. In monophasic evolution, the chromosome containing the weights and angles is evolved in a single phase. In biphasic evolution, the chromosome is evolved while keeping one parameter (e.g., weight) constant and then, in the second phase, the evolution is continued while keeping the other parameter (e.g., angle) constant. The dose calculation was carried out using “correction-based techniques”. Result: Simple and simulated clinical cases are presented to test the algorithm. They show that the biphasic evolution requires more computation time compared to monophasic (typically 40 and 20 minutes respectively) but results in a better optimization. Conclusion: The results show the efficacy of the algorithm and its fairly acceptable computation time

Protection effect of cerium oxide nanoparticles against radiation-induced acute lung injuries in rats

IntroductionRadiation therapy is one of the most common tools for treating cancer. The aim is to deliver adequate doses of radiation to kill cancer cells and the most challenging part during this procedure is to protect normal cells from radiation. One strategy is to use a radioprotector to spare normal tissues from ionizing radiation effects. Researchers have pursued cerium oxide nanoparticles as a therapeutic agent, due to its diverse characteristics, which include antioxidant properties, making it a potential radioprotector.Materials and methodsOne hundred rats were divided into five groups of A) control group, intraperitoneal (IP) saline injection was done twice a week; B) bi-weekly IP injection of 14.5nM (0.00001mg/kg) CNP for two weeks; C) a single whole thorax radiation dose of 18Gy; D) a single whole thorax radiation dose of 18Gy+bi-weekly injection of 14.5nM CNP for two weeks after radiation; E) bi-weekly IP injection of 14.5nM CNP for two weeks prior to radiation+a single whole thorax radiation dose of 18Gy. Thirty days after irradiation, 7 rats from each group were anesthetized and their lungs extracted for histopathological examination.ResultsStatistical analyses revealed that CNP significantly decreased the incidence of tissue collapse and neutrophile aggregation in rats receiving CNP before radiation in comparison with the radiation group.ConclusionThe results suggested the possibility of using CNP as a future radioprotector due to its ability to protect normal cells against radiation-induced damage

Effect of Oral Zinc Sulphate in Preventionof Radiation Induced OropharyngealMucositis During and After Radiotherapyin Patients with Head and Neck Cancers

Introduction:Mucositis is a disturbing side effect of radiotherapy treatment forhead and neck cancer. To date, no effective modality for its prophylaxis and treatmenthas been found. We performed this study to evaluate the efficacy of oral zincsulphate in delaying the onset of oral and pharyngeal mucositis and decreasing theirseverity.Materials and Methods: Atotal of 58 patients who were treated for head andneck squamous cell carcinoma with radiotherapy or chemoradiotherapy wererandomly assigned to receive oral zinc sulphate (220 mg) or an oral placebo 3 timesa day during their radiotherapy course. Total radiation dose was 6000 cGy to 7000cGy by conventional radiotherapy. Seventy nine percent of the patients also receivedconcurrent chemotherapy. Oral and pharyngeal mucositis were scored according toan RTOG protocol. Results:Time to onset of mucositis did not vary between the two groups.However, oral mucositis scores were less severe in the zinc group in weeks 4 to 6.The difference was statistically significant and the Pvalues for weeks 4, 5 and 6 were0.02, 0.007, and 0.012, respectively. Treatment interruptions in both groups were thesame (four cases each) and all were due to dysphagia (pharyngeal mucositis).Conclusion:Our results suggest that zinc is effective in reducing the severity oforal mucositis but not pharyngeal mucositis. Treatment interruptions were morefrequently caused by pharyngeal mucositis which presented as dysphagia, rather thanoral pain that was a manifestation of oral mucositis