A comprehensive Study of the Out of Field Non Target Dose Associated with 6 and 10 MV Flattened and Flattening Filter Free X Ray Beam in a True Beam Linear Accelerator.

AIM: To evaluate the out-of-field dose associated with flattened (FF) and flattening filter-free (FFF) 6 and 10 MV X-ray beams in a TrueBeam linear accelerator (Linac). MATERIALS AND METHODS: Measurements were taken in a slab phantom using the metal oxide semiconductor field effect transistor (MOSFET) detector at varying depths (dmax, 5 cm, and 10 cm) for clinically relevant field sizes and up to 30 cm from the field edges for 6 and 10 MV FF and FFF beams in TrueBeam Linac. Dose calculation accuracy of the analytic anisotropic algorithm (AAA) and Acuros algorithm was investigated in the out-of-field region. Similarly, the out-of-field dose associated with volumetric modulated arc therapy (VMAT) head-and-neck plan delivered to a body phantom was evaluated. RESULTS: The out-of-field dose for both FF and FFF photon beams (6 and 10 MV) decreased with increasing distance from the field boundary and size. Furthermore, regardless of FF in the field, higher-energy photon beams were associated with lower out-of-field dose. Both algorithms underestimated the dose in the out-of-field region, with AAA failing to calculate the out-of-field dose at 15 cm from the field edge and Acuros failing to calculate out-of-field radiation at 20 cm. At 5 cm from the field edge, an average of 50% underestimation was observed, and at 10 cm, an average of 60% underestimation was observed for both FF and FFF (6 and 10 MV) beams. The VMAT head-and-neck plan performed with the FFF beam resulted in a lower out-of-field dose than the FF beam for a comparable dose distribution. CONCLUSION: Compared with flattened beams, the FFF modes on TrueBeam Linac exhibited a clinically relevant reduction in the out-of-field dose. Further dosimetric studies are warranted to determine the significant benefit of FFF beams across different cancer sites.

Status of cancer treatment by radiotherapy and requirement of radiation oncology medical physicists in Asia Oceania federation of organizations for medical physics region.

Objective: Cancer is a major health problem worldwide including Asian-Pacific region. The region hosts over 4.5 billion people, over 60% of the world population and very divergent socioeconomically. The major cancers in the region in male include lung, stomach, liver, colorectal and esophagus and in female breast, lung, cervix, colorectal, and stomach. Over 60% of cancer patients need radiotherapy alone or in combination with surgery and/or chemotherapy, and therefore, radiotherapy is the main and essential modality of cancer treatment. Radiation oncology medical physicists play a pivotal role in efficient implementation of radiotherapy. This study was aimed to assess the status of cancer treatment by radiotherapy and the requirement of radiation oncology medical physicists in the region. Materials and Methods: To access the status and requirement of radiotherapy machines, availability of radiation oncology physicists in the region of Asia Oceania Federation of Organizations for Medical Physics (AFOMP), we have carried out a survey by sending questioners to AFOMP National Medical Physics Organizations (NMO). We received response from 21 countries, 100% response, regarding availability of teletherapy units, number of medical physicists working in radiotherapy and related information. Using GLOBOCAN cancer incidence data and considering 62.5% of cancer patients need radiotherapy treatment and up to 500 cancer patients can be treated in a year on one teletherapy machine, the gap between the available and required teletherapy machine to treat all the cancer patients requiring radiotherapy is estimated. Further, we estimated the gap between radiotherapy medical physicists available and required as per International Atomic Energy Agency and European Society for Therapeutic Radiology and Oncology guidelines. Results: It was observed that availability of teletherapy machines in AFOMP region is 0.21-14.0 teletherapy machine/million population and radiotherapy medical physicist are 0.82-2.43/teletherapy unit.

The International Organization for Medical Physics - a driving force for the global development of medical physics.

The International Organization for Medical Physics (IOMP) is the world's largest professional organization in the field of medical physics and has official non-governmental organization status with the World Health Organization (WHO) and the International Atomic Energy Agency (IAEA). IOMP is charged with a mission to advance medical physics practice worldwide by disseminating scientific and technical information, fostering the educational and professional development of medical physics and promoting the highest quality medical services for patients. IOMP's activities are directed towards the promotion of medical physics globally, improving patient care, and contributing to the benefit of healthcare to the society. Major organizational activities include but are not limited to scientific events, international collaborations, dissemination of information, education, training, and research. For nearly 60 years of existence, IOMP turned into a key factor not only in the field of medical physics, but also healthcare, and other related disciplines. IOMP is looking forward to future perspectives in international collaboration and enhancement of the professional skills, all directed towards enhancing patient benefit.

Medical physicist certification and training program accreditation.

As a profession, medical physics combines an advanced understanding of physics and math with knowledge of biology, anatomy and physiology. Consequently, rigorous education and training is required to assure that medical physicists have the requisite fundamental knowledge, specialized technical skills, and clinical understanding to contribute to the medical care of patients safely. There is, therefore, an interest in standardizing the educational pathways and in developing mechanisms to assure that competency is achieved and maintained. Throughout the world, several countries, regions, and professional organizations have developed mechanisms for accrediting medical physics educational programs, both for didactic work performed in undergraduate or post-graduate settings, and for clinical training conducted in hospitals and clinics. In addition, several national and international programs exist for certifying individual medical physicists. In some cases, once initial certification is achieved, the diplomate enters a program of maintenance of certification, to ensure that the skills obtained during training are not lost over a career. This article explores the differences and similarities in the training program accreditation and physicist certification mechanisms.

Dosimetry procedure to verify dose in High Dose Rate (HDR) brachytherapy treatment of cancer patients: A systematic review.

High dose rate (HDR) brachytherapy is a widely accepted cancer treatment method which provides high cure rates. In a HDR brachytherapy treatment, high radiation doses are delivered to the tumor area by placing the radioactive sources in the close proximity to the region of interest. The brachytherapy dose delivery follows the inverse square law with rapid dose fall of leading to minimal damage to the surrounding normal tissue. The safe direct delivery of the radiation dose to the tumour leads to good treatment outcomes comparable to other modalities of treatment. Hence, it is crucial to maintain a sharp drop in the radiation dose distribution within very short distances. Treatment planning system (TPS) which is controlled by a computer algorithm plays a significant role in calculating the optimum doses to the tumour area during a typical HDR brachytherapy treatment. However, the optimum dose calculated by the TPS must be verified by using an independent testing method in order to eliminate under/over irradiation of the tumor region and as quality assurance. In general, two types of independent dose verification methods(experimental and computational) are used to crosscheck the doses calculated by TPS. This systematic review aims to summarize the studies done in the past ten years on HDR brachytherapy treatment planning verification and to analyze the reliability and limitations.

Status of medical physics education and training in AFOMP region.

Medical physicists are health professionals recognized by the International Labour Organization (ILO) and hence medical physicists working in a clinical environment should have the required competency and undergo a structured training program and residency under an experienced medical physicist in a recognized institution. Furthermore, medical physics is a rapidly growing area needing a high degree of knowledge and professional competency due to the rise in complexity of treatment procedures, increasing access to medical technology, and the requirement of coordination between the disciplines of medicine, physics and biomedical engineering. The unprecedented surge in medical physics competency in the last 2-3 decades is due to the implementation of specialized physics intensive procedures such as particle therapy, image-guided & intra-operative radiotherapy, advanced imaging and nuclear medicine techniques. In this scenario to handle this new technology era the quantity of qualified medical physicists needs to be in consonance with the competency needed. There is a special requirement for education and training of medical physicists which led to the opening of numerous educational programs around the world. The Asia-Oceania Federation of Organizations for Medical Physics (AFOMP) was founded in 2000 and today 19 countries national medical physicist associations (NMPO) are member of AFOMP. The AFOMP region is populated by over 4.5 billion people and socioeconomically is very diverse with GDP per capita as high as around US $60,000 [Australia] to as low as around US $750 [Nepal]. We conducted a survey by sending questionnaires to AFOMP NMPOs to assess the status of medical physics education and training in the region. We have received responses from 20 countries in the AFOMP region to the questionnaire. It was observed that 16 [80%] countries from AFOMP have well organized master program in medical physics, however only 8 [50%] programs were accredited and in only 9 [45%] countries are medical physicists registered as health professionals.

Estimation of radiation-induced second cancer risk associated with the institutional field matching craniospinal irradiation technique: A comparative treatment planning study.

AIM: To estimate and compare the lifetime attributable risk (LAR) of radiation-induced second cancer (SC) in pediatric medulloblastoma patients planned with institutional 3D conformal field matching method, gap junction method and Intensity Modulated Radiotherapy (IMRT). BACKGROUND: The epidemiological studies on childhood cancer survivors reported that long-term cancer survivors who received radiotherapy are at a significantly increased risk for the development of SC. Hence, the increased concern to predict the SC risk for long-term survivors. MATERIALS AND METHODS: In addition to institutional field matching planning method, IMRT and gap junction methods were created for ten pediatric medulloblastoma patients. The risk estimates were made based on the site-specific cancer risk coefficient provided by the BEIR VII committee according to the organ equivalent dose for various critical organs. Also, plans were compared for target volume dose distribution and dose received by critical organs. RESULTS: When compared to the gap junction method, the IMRT and institutional field matching method were superior in normal tissue sparing and dose conformity. However, highly significant volume of low dose associated with IMRT was the main concern for the SC risk. The accumulated LAR for all the critical organs with 3D conformal gap junction and IMRT method was 23-25% while for the 3D conformal field matching method it was 21%. CONCLUSION: The LAR associated with the institutional field matching technique was substantially lower. As this method is highly robust and easy to set up, it can be a better choice of a craniospinal irradiation technique where 3DCRT is the only choice of treatment.

Estimated Risk of Radiation Induced Contra Lateral Breast Cancer Following Chest Wall Irradiation by Conformal Wedge Field and Forward Intensity Modulated Radiotherapy Technique for Post-Mastectomy Breast Cancer Patients

Background: Epidemiological studies have indicated an increasing incidence of radiation induced secondary cancer (SC) in breast cancer patients after radiotherapy (RT), most commonly in the contra-lateral breast (CLB). The present study was conducted to estimate the SC risk in the CLB following 3D conformal radiotherapy techniques (3DCRT) including wedge field and forward intensity modulated radiotherapy (fIMRT) based on the organ equivalent dose (OED). Material and Methods: RT plans treating the chest wall with conformal wedge field and fIMRT plans were created for 30 breast cancer patients. The risks of radiation induced cancer were estimated for the CLB using dose-response models: a linear model, a linear-plateau model and a bell-shaped model with full dose response accounting for fractionated RT on the basis of OED. Results: The plans were found to be ranked quite differently according to the choice of model; calculations based on a linear dose response model fIMRT predict statistically significant lower risk compared to the enhanced dynamic wedge (EDW) technique (p-0.0089) and a non-significant difference between fIMRT and physical wedge (PW) techniques (p-0.054). The widely used plateau dose response model based estimation showed significantly lower SC risk associated with fIMRT technique compared to both wedge field techniques (fIMRT vs EDW p-0.013, fIMRT vs PW p-0.04). The full dose response model showed a non-significant difference between all three techniques in the view of second CLB cancer. Finally the bell shaped model predicted interestingly that PW is associated with significantly higher risk compared to both fIMRT and EDW techniques (fIMRT vs PW p-0.0003, EDW vs PW p-0.0032). Conclusion: In conclusion, the SC risk estimations of the CLB revealed that there is a clear relation between risk associated with wedge field and fIMRT technique depending on the choice of model selected for risk comparison.

Thyroid dysfunction following therapeutic external radiation to head and neck cancer.

AIM: The aim of the present study was to evaluate changes in thyroid function in patients with head and neck cancer treated with external beam radiotherapy (EBRT). MATERIALS AND METHODS: This prospective study was conducted on ninety patients with non-thyroid head and neck cancer who were referred to the department of radiotherapy. Thyroid function tests were conducted before, midway during and after EBRT, with follow up at monthly intervals up to 6 months after the completion of therapy. RESULTS: Serum T3 and T4 levels were decreased at completion of EBRT and remained so after 6 months follow up. However, serum TSH levels did not significantly vary. CONCLUSION: EBRT to the neck region for treatment of head and neck cancer induces hypothyroidism and therefore utmost care must be taken to exclude the thyroid from radiation beams without sparing the tumor as far as possible. The clinical protocol in such cases should include monitoring of T3, T4 and TSH levels during and after the EBRT.

Prognostic and diagnostic value of serum pseudocholinesterase, serum aspartate transaminase, and serum alinine transaminase in malignancies treated by radiotherapy.

BACKGROUND: There is substantial evidence that environmental factors cause or accelerate the onset of malignancy. Environmental factors, due to the presence of many pollutants and carcinogenic agents, alter cellular growth, which leads to biochemical changes in the blood. MATERIALS AND METHODS: In the present study, we estimated serum pseudocholinesterase (PCHE), serum aspartate transaminase (AST), and serum alanine transaminase (ALT) in 92 patients with head and neck cancer and 71 patients with cancer of the uterine cervix; all of them were patients attending our department for radiation therapy. We also estimated PCHE, AST, and ALT levels in 30 healthy normal individuals. The estimations in cancer patients were done before the start of radiotherapy, midway through radiotherapy (30 Gy dose), at the end of radiotherapy, and during subsequent monthly follow-up visits over a period of at least 6 months. RESULTS AND DISCUSSION: We have observed that the PCHE levels were lower (31-49% of normal value) in all patients with malignancies, except in those with stage II head and neck cancers. We also found that the levels start increasing as radiotherapy progresses. The patients with no detectable/visible disease activity at 6 months follow-up showed PCHE values in the normal range. Similarly, the AST and ALT values were much higher (138-229% of normal value) in all the malignant cases as compared to the normal healthy individuals. The values decrease and approach normal levels as radiotherapy progresses and, in 92% of head and neck cancer cases [stages IIA, IIB, and IIIA] with no disease activity, the PCHE, AST, and ALT were normal or near normal; the corresponding figure in cancer cervix cases was 89%. From the present study we conclude that PCHE, AST, and ALT can be used as good prognostic biochemical tumor markers in the management of malignancies of the head and neck and uterine cervix.

Radiation dose to contralateral breast during treatment of breast malignancy by radiotherapy.

AIMS: External beam radiotherapy is being used regularly to treat the breast malignancy postoperatively. The contribution of collimator leakage and scatter radiation dose to contralateral breast is of concern because of high radio sensitivity of breast tissue for carcinogenesis. This becomes more important when the treated cancer breast patient is younger than 45 years and therefore the contralateral breast must be treated as organ at risk. Quantification of contralateral dose during primary breast irradiation is helpful to estimate the risk of radiation induced secondary breast malignancy. MATERIALS AND METHODS: In present study contralateral breast dose was measured in 30 cancer breast patients undergoing external beam therapy by Co-60 teletherapy machine. Postoperative radiotherapy was delivered by medial and lateral tangential fields on alternate days in addition to supraclavicle field daily with 200 cGy/F to a total dose of 5000 cGy in 25 fractions. CaSO4: Dy thermoluminescence dosimeter discs were employed for these measurements. Three TLD discs were put on the surface of skin of contralateral breast, one at the level of nipple and two at 3 cms away from nipple on both side along the midline for each field. At the end treatment of each filed, TLD discs were removed and measured for dose after 24 h on Thelmador-6000 TLD reader. RESULTS: The dose at the contralateral breast nipple was to be 152.5 to 254.75 cGy for total primary breast dose of 5000 cGy in 25 equal fractions which amounted to 3.05-6.05% of total dose to diseased breast. Further it was observed that the maximum contribution of contralateral breast dose was due to medical tangential half blocked field. CONCLUSION: CaSO4; Dy thermoluminescence dosimetry is quite easy, accurate and convenient method to measure the contralateral breast dose.