Measurement of 6 MV small field beam profiles - comparison of micro ionization chamber and linear diode array with monte carlo code.

The objective of this study is to analyze small field photon beams acquired with commonly available detectors. Beam profiles of 6 MV photons from the Siemens Primus Linear Accelerator were measured with a micro ion chamber (IC CC01, IBA) and linear diode array (LDA-99SC, IBA). Data was acquired using a water phantom for small fields (0.5×0.5 cm2 to 4×4 cm2) at depth of maximum dose, 5 cm and 10 cm. Profiles were also generated with EGSnrc Monte Carlo code. Measured and simulated profiles were compared in terms of percentage difference of the area under the simulated and measured profiles (PD), ratio of the measured to simulated dose at the point of maximum deviation within the central region of profile (R), full width half maximum (FWHM) and penumbra. For field sizes ≥1×1 cm2, the maximum PD is 3.17 % and 2.87 % for IC and LDA respectively, whereas R is in the range of 0.95-1.05 for IC and 0.99-1.05 for LDA. LDA measured FWHM and penumbra are also in better agreement with the simulated results. This study demonstrated that LDA can be used for acquisition of beam profiles for field size as low as 1×1 cm2.

Recent Trend in Specialty Choices of Medical Students and House Officers from Public Sector Medical Universities, Karachi.

OBJECTIVE: To determine career choices of medical students of public-sector medical universities and factors affecting their career choices. METHODS: The cross-sectional study was conducted at Dow University of Health Sciences and Jinnah Sindh Medical University, Karachi, from May 2015 to May 2016, and comprised 4th and 5th year medical students and house officers. A self-administrated structured questionnaire was used to collect data which was entered and analysed using SPSS 20. RESULTS: Of the 445 Subjects, 314(70.6%) were females. There were 206(46.3%) 4th year students, 194(43.6%) were from the 5th year and 45(10%) were house officers. Top 15 medical specialties were ranked according to the respondents' top three choices. Internal medicine 67(15.1%), cardiology 47(10.6%), paediatrics 46(10.3%) and general surgery 40(9.0%) were the four highest ranked specialties. Overall, 377(84.7%) subjects said prestige in working in that field was the reason of their respective choices. CONCLUSIONS: Medical students chose a wider range of specialties and stated varying factors affecting their choices.

A survey on radiation protection awareness at various hospitals in Karachi, Pakistan.

Purpose: To assess the awareness level of radiation protection among the radiation workers (i.e. medical radiation technologists, medical physicists, and medical radiological professionals) at the selected radiology, nuclear medicine, and radiotherapy facilities in Karachi, Pakistan. Material and methods: This survey was carried out in Karachi which has the largest number of hospitals, including radiology, nuclear medicine, and radiotherapy facilities in all Pakistan. In this double-blind survey, a questionnaire was designed and distributed to one hundred and sixty five (165) medical radiation workers at their respective workplaces. These radiation workers included the medical radiation technologists, medical physicists, and medical radiological practitioners. These radiation workers had varying experiences, training records, education, and fields of specialization. Out of these total 165 respondents, 84 belonged to the radiology facilities, 20 to nuclear medicine facilities, and 61 to radiotherapy facilities. The educational level was classified as less than 16 years, and equal to or greater than 16 years. Similarly, the training was classified as "attended" or "never attended" and the experience as less than five years, between 5 and 10 years, and greater than ten years. The data was processed through SPSS (v.20) against a significance level (P ≤ 0.05). Results: The statistical analysis of the survey indicates that the radiation workers in radiology, nuclear medicine, and radiotherapy facilities in Karachi have limited awareness of radiation protection issues. The overall outcome of the survey also concluded that the awareness regarding radiation effects, radiation warning signs, and annual dose limit is optimum. However, the response to the questions related to patient protection remained unsatisfactory. Conclusion: This study showed that most of the radiation workers who participated in the survey lacked appropriate awareness of radiation protection measures. The radiation workers did show a better understanding of basic radiation protection parameters, such as the annual dose limit and radiation effects. However, the radiation workers needed an overall improvement in radiation protection awareness, particularly, related to patient protection. This awareness and knowledge should be improved through systematic and periodic trainings.

A review of international and developed practices of medical physics from a legislative and regulatory point of view and its applicability and comparison with Pakistan.

The importance of the medical physics profession and medical physicists is widely recognized by the international bodies like ILO, IAEA, EC, etc. The description of a medical physicist's qualification framework, their role and responsibilities have been addressed in the legislative and regulatory frameworks of developed countries like the USA (in 10CFR) and the EC (EC RP 174) and less comprehensively in developing counties like Pakistan. AFOMP has contributed positively in various regulatory and policy matters regarding the medical physics practices in Asian countries. Furthermore, the recommendations of IAEA's regional meeting on "Medical Physics in Europe-Current Status and Future Perspective" in Vienna, 2015, address the need and mechanism of a harmonized framework for medical physicists' qualifications. The lack of a comprehensive professional recognition framework becomes more challenging when we see that hi-tech diagnostic (e.g. PET CT) and therapeutic (e.g. cyberknife, VMAT, tomotherapy, etc.) modalities are now available in many parts of the world, including Pakistan which still have a basic level of medical physics qualification and practices. Therefore, international efforts like the above-mentioned IAEA-EC meeting in 2015; and by AFOMP activities related to training, qualification and recognition of medical physicists can provide a pathway to further improve medical physics practices in the developing world. The objective of this review is to (i) summarize the international practices for the legislation and regulation of medical physics, (ii) provide a brief overview of the medical physics practices in Pakistan and (iii) discuss the applicability of the IAEA-EC meeting's recommendations to the case of Pakistan. The review highlights the areas which are addressed in IAEA-EC meeting and could be beneficial to other nations as well, particularly, for low and middle income countries. The review also presents few suggestions how to progress with the medical physics profession in developing countries in general, and in Pakistan in particular. These suggestions also include further possible pathway the IAEA could consider, like IAEA project or meetings, to further strengthen the medical physics profession globally.

Variations in the Dose Profiles of Physical and Virtual Wedge Filters of ONCOR Linear Accelerator.

PURPOSE: In this study, we measured the dose profiles of physical wedges (PWs) and virtual wedges (VW) for photon energies (6 MV and 15 MV), various field sizes (10 × 10, 15 × 15, and 20 × 20 cm2), depths (dmax, 10 cm, 20 cm), and wedge angles (15°, 30°, 45°, and 60°). This study was performed using a Siemens ONCOR IMRT Plus linear accelerator. The acquired dose profiles of PW and VW were compared and statistically analyzed. MATERIALS AND METHODS: The dose profiles were measured using IBA CC13 ion chamber in IBA Blue phantom (a three-dimensional water phantom). The source-to-surface distance was kept 100 cm and measurements were taken for 10 × 10, 15 × 15, and 20 × 20 cm2 field sizes and for 15°, 30°, 45°, and 60° PWs. These measurements were taken for both 6 MV and 15 MV photon energies. VW profiles were obtained using LDA-99 linear detector array (IBA, Germany). The percent off-axis dose difference between PW and VW profiles were calculated, analyzed, and plotted. Statistics on the measured data was applied using SPSS version 13. RESULTS AND CONCLUSION: The percent dose difference between PW and VW beam profiles were calculated at different off-axis positions. These dose variations increased in the wedge direction (toe region), but were negligible in the nonwedge direction. The results of one-way analysis of variance show that the dose variation between PW and VW are significant with off-axis positions, wedge angles, and depth, but are statistically nonsignificant with energy and field sizes. These variations could produce abnormal doses, especially in large field sizes and wedge angles in clinical applications, which could be avoided by understanding the behavior of wedge profiles and comparing the calculated (from treatment planning system) and measured (actual) doses.

Vestibular schwannoma: an unusual post radiotherapy response.

Vestibular schwannoma is a relatively uncommon tumor. Although, it is benign but locally expansile and spreads to damage the adjacent structures. Treatment strategy includes surgery, Stereotactic Radiosurgery (SRS) either by standard or hypofractionated protocols. Due to its benign nature, radiation therapy cannot remove the tumor completely, instead radiation therapy halts the growth of vestibular schwannoma and inactivates this benign tumor. Response of radiation in the form of tumor shrinkage is seen 2 - 2.5 years after the radiations. We report a case of vestibular Schwannoma in which residual tumor of 3.1 cm size following subtotal resection was irradiated of the dose of 54 Gy in 30 equal fractions on 3-Dimensional Conformal Radiation Therapy (3-DCRT). A follow-up CT scan brain after 2 months of radiotherapy showed complete disappearance of the disease categorized as complete response. This is an unusual phenomenon and is likely due to the very rarely seen malignant transformation or presence of malignant component in this benign tumor.