Design and Testing of Indigenous Cost Effective Three Dimensional Radiation Field Analyser (3D RFA)

Technology in Cancer Research and Treatment ISSN 1533-0346 Volume 13, Number 3, June 2014 Adenine Press (2014) Design and Testing of Indigenous Cost Effective Three Dimensional Radiation Field Analyser (3D RFA) The aim of the study is to design and validate an indigenous three dimensional Radiation Field Analyser (3D RFA). The feed system made for X, Y and Z axis movements is of lead screw with deep ball bearing mechanism made up of stain less steel driven by stepper motors with accuracy less than 0.5 mm. The telescopic column lifting unit was designed using linear actuation technology for lifting the water phantom. The acrylic phantom with dimensions of 800 3 750 3 570 mm was made with thickness of 15 mm. The software was developed in visual basic programming language, classified into two types, viz. beam analyzer software and beam acquisition software. The premeasurement checks were performed as per TG 106 recommendations. The physical parameters of photon PDDs such as D max, D 10, D 20 and Quality Index (QI), and the electron PDDs such as R 50, R p, E 0, E po and X-ray contamination values can be obtained instantaneously by using the developed RFA system. Also the results for profile such as field size, central axis deviation, penumbra, flatness and symmetry calculated according to various protocols can be obtained for both photon and electron beams. The result of PDDs for photon beams were compared with BJR25 supplement values and the profile were compared with TG 40 recommendation. The results were in agreement with standard protocols. www.tcrt.org DOI: 10.7785/tcrt.2012.500370 K. M. Ganesh, Ph.D. 1 * A. Pichandi, M.Sc. 2 R. M. Nehru, Ph.D. 3 M. Ravikumar, Ph.D. 1 1 Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Hosur Road, Bangalore 560029, India 2 Health Care Global Hospitals, Sampingeram Nagar, Bangalore 560027, India 3 Atomic Energy Regulatory Board, Mumbai 400094, India Key words: Radiation field analyser; Beam flatness; Beam symmetry; Penumbra; Field size; Percentage depth dose; Beam profile. Introduction Radiation therapy plays a vital role in cure and alleviation of sufferings of cancer patients. In India, it is estimated that over 1 million cancer cases are detected every year (1) and a majority of them require radiotherapy at one time or other during their course of the treatment. Radiation oncology is a specialty field where treatment delivery is done mainly by photon and electrons through sophisticated machines such as linear accelerators, cyber knife (2), etc. with the availability of newer modalities of treatment in radiotherapy, such as medical linear accelerators with Multi Leaf Collimator (MLC), micro-mlc and dynamic MLC facilities (3), X-knife (4) and gamma knife units (5). With the availability of computerized Abbreviations: AERB: Atomic Energy Regulatory Board; D 10 %: Dose at 10 cm Depth; d 80 cm: Depth of 80% Dose; FFF: Flattening Filter Free; HMI: Human Machine Interface; LM: Linear Motion; MLC: Multi Leaf Collimator; PC: Personalized Computer; PDD: Percentage Depth Dose; QI: Quality Index; RBA: Radiation Beam Analyser; RFA: Radiation Field Analyzer; SAD: Source to Chamber Distance; SD: Standard Deviation; SNR: Signal to Noise Ratio; SSD: Source to Surface Distance; TPS: Treatment Planning System; Z ref : Reference Depth; 3D RFA: Three Dimensional Radiation Field Analyser. *Corresponding author: K. M. Ganesh, Ph.D. Phone: 191 9945889421 E-mail: kmganesh1@gmail.com 195

196 Ganesh et al. treatment planning systems with 3D facilities, radiation oncology scenario is poised for a major leap forward and is tending towards technology oriented treatment delivery. To ensure the quality treatment, effective acquisition of beam is very necessary (6). In modern radiotherapy beam acquisition is done mainly using Radiation Field Analyzer (RFA) that acquires such beam from the treatment machine and gives as per the requirement of Treatment Planning System (TPS) vendors (7). To drastically reduce the burden of getting the imported RFAs, an indigenous cost effective and suitable three dimensional RFA for Indian conditions is absolutely necessary. An effort in designing such a cost effective, rugged 3D RFA will lead to drastic reduction of treatment cost and benefit to the cancer patients is need of the hour. The indigenous system was tested as per the TG 106 (8) protocol. The results were compared with BJR25 supplement (9) and TG 40 (7) recommendations in a high energy linear accelerator along with the obtained from the other commercially available RFA vendors. Materials and Methods Development of 3D RFA The development of 3D RFA would be categorically divided into three parts such as, (i) Development of water phantom, telescopic column lifting, three dimensional stepper motors such as alignment designing for phantom, development of console for manual movements of stepper motors and zero adjustments. (ii) Development of software for beam acquisition using Microsoft Visual basic 6 software and development of analyzing software for giving as per International/National protocols. (iii) Integration of dual channel electrometer, the stepper motor Linear Motion (LM) guide assembly and the acquisition software. Design of Water Phantom Water phantom was made with 15 mm thick acrylic with 800 3 750 3 570 mm size. UV pasting were made to ensure no water leakage. The larger size of the phantom was to accommodate the LM guide and stepper motor assembly. Telescopic Lifting Mechanism The Lift table is a separate water phantom carriage with electrically operated lifting mechanism for the positioning of the water phantom. The carriage has two fixed and two steerable rollers with brakes. The electrical version has one compartment and two drawers for storing accessories and is furthermore equipped with a leveling frame for fine adjustment in vertical and horizontal directions. The lifting mechanism is capable of lifting 700 Kgs with stroke of 40 cm and the speed were set at 5 mm/sec on max load (can be increased to 15 mm) to avoid any jerk and wobbling of water phantom during movement. The lifting assembly is provided with a 2 button pendent for operation. The load bearing frame is fitted with four heavy duty caster wheels with locking options. The phantom lifting platform has 4 degrees of adjustment to account for the leveling of floor or phantom. The overall height was kept at 1450 mm for the lifting mechanism. LM Guide and Ball Screw Linear motion systems are unique motion systems in which linear motion is supported by rolling contact elements. These linear motion systems can best be described as a motion system which uses the rotational motion principle of a deep grooved ball bearing. The combined LM and lead screw is known as linear actuator. A lead screw also known as a power screw is a screw designed to translate turning motion into linear motion. An electric motor was mechanically connected to rotate a lead screw. A lead screw has a continuous helical thread machined on its circumference running along the length (similar to the thread on a bolt). Threaded onto the lead screw is a lead nut or ball nut with corresponding helical threads. The nut is prevented from rotating with the lead screw (typically the nut interlocks with a non-rotating part of the actuator body). Therefore, when the lead screw is rotated, the nut will be driven along the threads. The direction of motion of the nut will depend on the direction of rotation of the lead screw. By connecting linkages to the nut, the motion can be converted to usable linear displacement. In our design, we used stepper motor and high precision stainless steel moving mechanism. Stepper Motor A stepper motor (or step motor) is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor s position can then be commanded to move and hold at one of these steps without any feedback sensor (an open-loop controller). In our study, three stepper motor for X, Y and Z positioning were used which had the speed of 40 mm/s and accuracy of 0.5 mm. All three stepper motor are controlled by the control console system through driver card. The motors can also be controlled locally by the Human Machine Interface (HMI) pendent which communicates through the same driver card.

Indigenous Three Dimensional Radiation Field Analyser 197 Human Machine Interface (HMI) A local pendent to control and adjust the X, Y and Z movements was developed using HMI. The pendent was designed with two page operation to provide all the required functions. The HMI pendent was developed with touch screen technology. The first page (main page) has the following buttons of operation (Figure 1): a) X, Y, Z forward/reverse switch b) Virtual home c) Define home d) Machine home e) Speed selection (fast/slow) and f) Next button a) X, Y, Z value entry for desired movements b) Start and c) Speed selection Dual Channel Electrometer The Personalized Computer (PC) Electrometer (Sun Nuclear Inc., USA) has two triaxial BNC inputs for connection to ion chambers for dosimetric measurements. The ion chamber voltage bias can be adjusted to various levels at either polarity. For air density correction, there are internal temperature and pressure sensors that measure ambient conditions and an input for an external remote temperature sensor. A USB port provides power and communication with PC software. The conductive enclosure (4 10.5 14 cm) provides EMI shielding and LED status indicators. The calibrated dual channel electrometer has dose rate of 0.001-500.0 pa, 1 fa resolution (low range) and 0.001-500.0 na, 1 pa resolution (high range). In charge mode the ranges are 0.001 pc-999.9 μc, 1 fc resolution (low range) and 0.001 nc-999.9 μc, 1 pc resolution (high range). Repeatability of the electrometer is 0.1% (IEC 60731 requirement: 0.5%) (10). Three preset bias voltages of 0, 150 and 300 volts can be used. The bias voltages can also be set independently to fulfill our custom needs. The electrometer was procured along with the calibration certificate. Ionization Chamber Figure 1: Display of first page on the HMI pendent. The Next button provided in the first page will take the operator to the second page, which has the following operations (Figure 2): The ionization chambers of 0.125 cc (Standard Imaging Inc., USA) (8) is used for both reference and field measurements. The cylindrical chamber has 36 mm rigid stem with inner diameter of 5.5 mm. The chamber has an aluminum electrode with 1 mm diameter and 5 mm long. The chambers are energy independent from 30 KeV to 50 MeV range. For both the chambers the calibration certificates were obtained. Beam Analysis Software The software for radiation beam analyzer was developed in the Microsoft Visual basic 6.0 platform which can support all windows operating systems. Different software modules required by the RFA system that were developed are (i) Beam scanning module (ii) Beam analysis 1. Import other vendor file module 2. Protocol library module 3. Result display module Figure 2: Display of second page on the HMI pendent. Beam Scanning Module: Beam scanning module controls the stepper motor, LM guide mechanism and the dual channel electrometer. Before collecting the radiation beam, the electrometer can be reset for residual charges by choosing the

198 Ganesh et al. zeroing option. The option to set the bias voltage is also provided in the window. Before the commencement of actual collection, it is mandatory to feed the type of radiation unit, energy, field size, Source to Surface Distance (SSD), wedge angle, gantry angle, collimator angle etc. to the developed RFA software. The screen shot indicating these options are shown in Figure 3. In the same window, the provision for direct selection of Percentage Depth Dose (PDD), in plane profile, cross plane profile, diagonal (left-right) profile and diagonal (right-left) profiles can be obtained for multiple depths and multiple field sizes. All the profiles are displayed in the same live window. Additionally an option is provided to select the PDD scan direction (top-bottom or bottom-top). Before obtaining the actual profile, the detector will get aligned to the preset home position (0, 0, 0 coordinates) and then the collection of occurs for profile. The system is programmed in such a way that on completion of each scan the system will automatically normalize the maximum reading to 100%. While collecting the in plane or cross plane profiles the detector will move to collect beam by calculating the scan starting point from the fed field size and the penumbral margin information. The software is developed in such a way that the detector checks for the shortest distance from its current position to start the scan. Beam Data Analysis Import other vendor file module: The scan of other commercially available RFA can be imported for analyzing in the developed software. When the scan files of other vendors are imported the is programmed to convert those files into file extension format of the developed software which is RBA (Radiation Beam Analyser) attached to each file. This module provides option to check the scanned of other vendors with developed software and vice-versa. Protocol library module: Various standard protocol libraries were made available in the developed software for the convenience of the users such as AERB, IAEA, DIN, TG 45 etc. A typical screen indicating the selection options is presented in Figure 4. Figure 3: A typical beam scanning module screen.

Indigenous Three Dimensional Radiation Field Analyser 199 Figure 4: A typical protocol selection screen. Result display module: The result will be displayed as per the selected parameters. In single screen, the option of opening multiple profiles/pdd s, stretching/skewing of windows were made available. The displayed results may be converted in to ASCII or any other format as required by the vendors Treatment Planning Systems (TPS). A typical 6 MV photon PDD for 10 3 10 cm 2 field size obtained at 100 SSD with the display of results is shown in Figure 5. Communication Configuration The communication link of the developed 3D RFA were designed as per the conceptual diagram illustrated in Figure 6. The communication ports of various electronic devices that are required to form the full 3D RFA assembly posed a major challenge while undertaking the task. The ionization chamber Figure 5: Result display screen along with the measured depth dose profile.

200 Ganesh et al. Figure 6: Conceptual diagram of the developed 3D RFA. had BNC type connector (normally available type of connector), while the electrometer had TNC type of input. The electrometer had Type A USB port as output and Type B USB port for input. The 3D motion controller had the RS232 output. To overcome the port problem a special device called USB over IP was introduced in the electronics that will convert the electrometer output to RS232 output. This RS232 output and the output from the 3D motion controller are connected to an ethernet hub, through which the control console system communicates with both the electrometer and motion controller. Premeasurement Checks The premeasruement checks were performed as per the task group 106 (8) recommendations. The noise, signal to noise ratio, leakage, effect of polarity, effect of sampling time, effect of dose rate and effect of step size were measured as per TG 106 recommendation. Validation of the 3D RFA The premeasurement checks were performed as per TG 106 recommendations. The physical parameters of photon PDDs such as D max, D 10, D 20 and quality index (QI), and the electron PDDs such as R 50, R p, E 0, E po and X-ray contamination values can be obtained instantaneously by using the developed RFA system. Also the results for profile such as field size, central axis deviation, penumbra, flatness and symmetry calculated according to various protocols can be obtained for both photon and electron beams. The result of PDDs for photon beams were compared with BJR25 supplement values and the profile were compared with TG 40 recommendation. Result and Discussion Premeasurement Test The premeasurement tests were performed for 6 MV, 18 MV photons and 16 MeV electrons as dry run and water run separately in Clinac DHX linear accelerator (Varian Medical Systems, USA). Noise, Signal to Noise Ratio (SNR), leakage, effect of dose rate measurements was measured for dry run. Noise, SNR, leakage, effect of sampling time, effect of dose rate, effect of step size were analysed in water as recommended in TG 106 (8) report. Noise, SNR and Leakage The in-air measurement (dry run) and water run was performed in a dual energy accelerator for the field size of 20 3 20 cm 2 and 10 3 10 cm 2 at source to chamber distance (SAD) of 100 cm for 6 MV, 18 MV photons and 16 MeV electrons. The ionization chamber with 0.125 cc was used for both field and reference. To determine the noise in the normalized flattened region the central 80% of field size was taken. In the same region the SNR was calculated as the coefficient of variation which is the Standard Deviation (SD) divided by the mean. The leakage were measured as the coefficient of variation and mean in the non-radiation region of the profile obtained with 20 3 20 cm 2 and 10 3 10 cm 2 field size. The non-radiation region was taken as the final 2 cm region of the tail portion of the profile. The results for 6 MV and 18 MV photons and 16 MeV electrons in air and water are shown in Tables I, II and III, respectively.

Indigenous Three Dimensional Radiation Field Analyser 201 Field size (cm 2 ) Field size (cm 2 ) Table I Premeasurement results of photon beams (dry run). Noise (SD) Table II Premeasurement results of photon beams (water run). Noise (SD) 6 MV Photons 18 MV Photons SNR (Coefficient ) Leakage 6 MV Photons 18 MV Photons SNR (Coefficient ) Leakage Noise (SD) Noise (SD) SNR (Coefficient ) Leakage 10 3 10 0.466 0.004 0.055 0.64 0.006 0.046 20 3 20 1.105 0.010 0.020 1.076 0.010 0.045 SNR (Coefficient ) Leakage 10 3 10 0.260 0.003 0.110 0.696 0.007 0.019 20 3 20 0.091 0.002 0.027 0.634 0.006 0.037 Table III Premeasurement result of 16 MeV Electron beam (dry and water run). Field size (cm 2 ) Noise (SD) Dry run SNR (Coefficient ) Leakage Noise (SD) Water run SNR (Coefficient ) Leakage 15 3 15 0.264 0.002 0.022 0.18 0.001 0.097 In the dry run, the SD was minimum at 100 0.466 for 6 MV photons with 10 3 10 cm 2 and maximum with 20 3 20 cm 2 as 100 1.105. The coefficient of variation and leakage was less significant for both field sizes. In the water run, the SD was minimum at 100 0.091 for 6 MV photons with 20 3 20 cm 2 and maximum with 10 3 10 cm 2 as 100 0.696 for 18 MV photons. The coefficient of variation and leakage in water run was less significant for both field sizes for photons. The noise for electron was more in dry run compared with water run was observed. The SNR and leakage was less significant in both cases for electrons. The leakage measurement in premeasurement tests had inconsistency which may be probably due to non-availability of flat region at the tail portions due to the mechanical constraint of the RFA. Polarity The dry run profiles were acquired for the field size of 20 3 20 cm 2 for 6 MV photon and 16 MeV electron beam for four different polarities such as 1150, 2150, 1300 and 2300 V. The measurement was done using 0.125 cc ionization chamber. The parameters such as flatness, symmetry and penumbra were determined and presented in Table IV. Though some difference was found with the parameters when measured with different polarity, but the results all were within agreeable limits irrespective of the polarity used. The variation in flatness for both 6 MV photons and 16 MeV electrons did not show significant variation with change of polarity. Whereas the maximum variation in the symmetry was observed as 0.13% and the maximum variation in penumbra by 0.25 mm with both energies. Sampling Time The profile were acquired in water for the field size of 20 3 20 cm 2 for 6 MV and 18 MV photon beams at 100 cm SSD for three different sampling time such as 1000 ms, 1500 ms and 2000 ms using 0.125 cc ionization chamber for both reference and field measurements. The profile for 16 MeV electron beam was obtained with 15 3 15 cm 2 applicator. The parameters such as flatness, symmetry and penumbra were determined and the variations are tabulated in Table V and Table VI for 6 and 18 MV photons and 16 MeV electrons, respectively. The flatness was observed with the difference of 0.41% and 0.34% for 6 and 18 MV photon beams, respectively. The symmetry for 6 MV photon varied by 0.11% and 0.42% for 18 MV photons. The variation in penumbra for both photon energies was found less significant with all three sampling times. The flatness for electron was observed with 0.36% and the symmetry varied by 0.40% for 15 3 15 cm 2 applicator. The variation in penumbra was found to be less significant with all three different sampling times. The sampling time with 2000 ms gave good results, however the measurement taken with other sampling times also were found to be satisfactory within the limits. Table IV Effect of polarity for 6 MV photon and 16 MeV electron beams. 6 MV Photons 16 MeV Electrons Polarity (Volts) 2300 0.93 0.24 8.31 8.30 0.96 1.05 11.05 11.03 300 0.93 0.34 8.10 8.07 0.96 0.97 11.06 11.14 2150 0.93 0.28 8.06 8.13 0.96 0.93 11.04 11.10 150 0.93 0.37 8.23 8.20 0.96 0.86 11.13 11.07

202 Ganesh et al. Table V Photon profiles for different sampling time. 6 MV Photons 18 MV Photons Sampling time (ms) 1000 0.28 0.20 8.94 8.38 0.72 1.23 7.33 7.38 1500 0.51 0.31 8.69 8.93 1.11 1.38 7.51 7.33 2000 0.10 0.23 8.46 8.77 0.67 0.96 7.25 7.35 Sampling time (ms) Table VI Electron profile for different sampling time. 16 MeV Electrons 1000 1.72 1.41 11.25 11.04 1500 1.57 1.15 11.16 11.25 2000 1.36 1.01 11.09 11.23 Table VII 6 MV photon beam parameters for different dose rates for 10 3 10 cm 2 field size. Dose rate (MU/Min) 6 MV Photons 160 1.51 1.39 8.97 8.78 320 0.93 0.34 8.69 8.93 400 0.78 0.80 8.95 8.77 Dose Rate The profile in water were acquired at D max depth for the field size of 10 3 10 cm 2 for 6 MV and 18 MV photon beam at 100 cm SSD for four different dose per monitor unit. For 6 MV the dose rate effect was studied with 160 MU/min, 320 MU/min and 400 MU and for 18 MV photons the dose rate was studied at 200 MU/min, 400 MU/min and 600 MU. The profile for 16 MeV electron was acquired at Z ref depth with 15 3 15 cm 2 applicator with dose rates similar to 18 MV photons. 0.125 cc ionization chamber was used for both reference and field measurement. The parameters such as flatness, symmetry and penumbra were determined and the variations are presented in Table VII for 6 MV photon and in Table VIII for 18 MV photon and 16 MeV electrons. The flatness for 6 MV photons with dose rates differed by about 0.73%, the symmetry varied by 1.05% with no considerable difference with the penumbra on either side. The flatness for 18 MV photons with different dose rates differed by about 0.47% and by 0.63% for 16 MeV electrons. The symmetry varied by 0.39% and 0.11% for 18 MV photons and 16 MeV electrons, respectively, with no considerable difference with the penumbra on either side. Testing of Analyser Software To test the calculated results of PDD beam, a depth dose profile with 100 cm SSD in 6 MV for 10 3 10 cm 2 field size was obtained by importing the other vendor (PTW, Germany) ASCII format file in to the developed software. The obtained result through the developed software such as D max, D s, D 100, D 200, QI, R 80 and R 50 were tabulated in Table IX. The results of PTW RFA were compared to find the accuracy of calculation of results. The results were in agreement within 0.1% and 0.2 mm. A typical screen showing the display of imported PDD in ASCII format for 6 MV photons is shown in Figure 7. To test the calculated results of profile beam with the developed software, a profile with 100 cm SSD in 6 MV for 10 3 10 cm 2 field size obtained at 16 mm depth was obtained by importing the PTW ASCII format file in to the developed Table VIII Beam parameters for 18 MV photon and 16MeV electron for different dose rates. 18 MV Photon 16 MeV Electron Dose MU/Min 200 0.88 1.17 7.85 7.77 1.15 1.25 11.19 11.07 400 1.11 1.38 7.51 7.33 1.18 1.21 11.24 11.08 600 1.35 0.99 7.70 7.65 1.78 1.14 11.11 11.22

Indigenous Three Dimensional Radiation Field Analyser 203 Table IX Comparison of PDD with PTW and software for 6 MV photons at 10 3 10 cm 2. Parameters PTW Software Software D max 16.20 16.00 0.20 D S 50.92 50.93 0.01 D 100 67.71 67.71 0.00 D 200 39.19 39.19 0.00 QI 0.6734 0.6733 0.001 R 80 67.63 67.60 0.04 R 50 156.11 155.96 0.15 typical screen showing the display of imported beam profile in ASCII format for 6 MV photons at 10 3 10 cm 2 is shown in Figure 8. Measurement of Beam Data To test the measured results of photon PDD beam, a depth dose profile with 100 cm SSD in 6 MV photons for 10 3 10 cm 2 and field sizes was obtained through the developed RFA. A typical PDD acquired using the developed RFA is shown in Figure 9. The result such as depth of dose max Figure 7: Screen showing the display of imported PDD in ASCII format for 6 MV photons. Table X Comparison of beam profile (10 3 10 cm 2, 6 MV) at 16 mm depth. Parameters PTW Software Software Cax 20.03 20.03 0.00 Field size (cm) 10.12 10.12 0.00 6.12 6.20 0.08 5.86 5.86 0.00 1.27 1.27 0.00 0.64 0.58 0.70 Table XI Validation of beam profile (10 3 10 cm 2, 6 MV) at 16 mm depth Parameters BJR25 Measured D max (cm ) 1.5 1.6 0.10 D 80 (cm) 6.7 6.57 0.13 D 10 67.5 67.7 0.20 QI 0.676 0.009 0.675 0.001 software. The result such as central axis shift, field size, penumbra left, penumbra right, flatness and symmetry were calculated and tabulated in Table X. The results of PTW RFA were compared to find the accuracy of calculation of results. The results were in agreement within 0.7% and 0.08 mm. A (D max ), dose at 10 cm depth (D 10 %), the depth of the 80% dose (D 80 cm) and QI were tabulated in Table XI. The results of the developed software were compared with BJR25 values to find the accuracy of calculation of results. The results were in agreement within 0.1% and 2 mm.

204 Ganesh et al. Figure 8: Screen showing the display of imported beam profile in ASCII format for 6 MV photons at 10 3 10 cm 2 field size. Figure 9: Screen showing the display of acquired PDD for 6 MV photons for 10 3 10 cm 2 field size and the results. To test the beam profile with the developed RFA, beam were obtained for both photon and electron energies. The profile results such as beam flatness and symmetry for 6 MV and 18 MV photons for 5 3 5 cm 2, 10 3 10 cm 2 and 30 3 30 cm 2 field sizes were acquired at D max depth from the developed software and compared with the base line value as recommended in AAPM TG 40 Report No. 46 (7). Similarly the profile results for 6, 9, 12, 16 and 18 MeV electrons were also obtained at reference depth (Z ref ) and compared with the base line values. The flatness and symmetry definitions in the developed software were programmed as per AAPM TG 45 Report No. 47 (11). The results are presented in Table XII for photons and in Table XIII for electrons.

Indigenous Three Dimensional Radiation Field Analyser 205 The maximum variation in flatness and symmetry is 0.51% and 0.5%, respectively for both 6 and 18 MV photons. Similarly the variation in both flatness and symmetry among all the 5 electron energies were within 0.7%. The results of photons and electrons were in agreement with AAPM TG 40. The was also obtained using -RFA (Scanditronix, USA) for the same filed size with identical setup. The PDD parameters for 6 and 18 MV Photons such as R 100 and R 80 D s, D 100, D 200 and QI for 5 3 5 cm 2, 10 3 10 cm 2 and 30 3 30 cm 2 at 100 cm SSD were obtained. The results are presented in Table XIV. Table XII Validation of beam profile for 6 and 18 MV Photons with base line value for 5 3 5 cm 2, 10 3 10 cm 2 and 30 3 30 cm 2 field size at D max depth. Energy 6 MV photon 18MV photon Parameters Base line value Measured Base line value Measured Base line value Measured 5 3 5 cm 2 10 3 10 cm 2 30 3 30 cm 2 0.6 0.7 20.1 0.92 1.2 20.28 1.58 1.2 0.38 0.2 0.3 20.1 0.4 0.8 20.4 0.2 0.7 20.5 1.81 1.3 0.51 0.95 0.9 0.05 2.21 2 0.21 0.3 0.5 20.2 1.21 1.5 20.29 0.4 0.5 20.1 Table XIII Validation of beam profile for 6, 9, 12, 16 and 18 MeV electrons with base line value for 15 3 15 cm 2, 25 3 25 cm 2 applicator at Z ref. Base line value Measured Base line Value Measured Data Energy Parameters 15 3 15 cm 2 25 3 25 cm 2 6 MeV 9 MeV 12 MeV 16 MeV 20 MeV 0.88 0.95 20.07 1.5 1.1 0.4 0.45 1.1 20.65 1.5 1.8 20.3 0.89 0.5 0.39 1.6 0.9 0.7 1.01 0.85 0.16 1.4 1.1 0.3 0.86 0.5 0.36 1 0.8 0.2 0.78 1.02 20.24 1.2 0.6 0.6 0.86 0.85 0.01 1.5 1 0.5 0.38 0.8 20.42 1.1 0.9 0.2 0.84 0.4 0.44 2.1 1.8 0.3 1.5 1.7 20.2 2.6 1.9 0.7 Table XIV Comparison of results with the developed software (5 3 5 cm 2, 10 3 10 cm 2 and 30 3 30 cm 2 for 6 and 18 MV photons at 16 mm depth). Energy Parameters 5 3 5 cm 2 10 3 10 cm 2 30 3 30 cm 2 6 MV Photon 18 MV Photon R 100 15.30 15.70 20.40 16.00 16.00 0.00 13.30 14.00 20.70 R 80 60.70 60.74 20.04 64.62 66.47 21.85 73.50 74.87 21.37 D s 42.20 52.50 210.30 51.80 62.04 210.24 68.50 74.72 26.22 D 100 62.90 63.12 20.22 66.67 66.92 20.25 72.20 72.04 0.16 D 200 34.60 34.49 0.11 38.72 38.59 0.13 45.80 45.96 20.16 QI 0.64 0.63 0.01 0.67 0.67 0.00 0.74 0.75 20.01 R 100 35.50 36.00 20.50 32.00 34.00 22.00 23.70 24.00 20.30 R 80 97.50 97.83 20.33 98.90 99.13 20.23 97.40 98.31 20.91 D s 20.00 29.80 29.80 28.49 38.95 210.46 50.70 59.28 28.58 D 100 79.10 79.23 20.13 79.78 79.71 0.07 79.30 79.52 20.22 D 200 51.00 51.16 20.16 53.19 52.99 0.20 55.90 56.02 20.12 QI 0.76 0.76 0.00 0.79 0.78 0.00 0.83 0.83 0.00

206 Ganesh et al. The results of commercial -RFA were compared with the results of the developed software to find the accuracy of calculations. The results for 6 and 18 MV photons for 5 3 5 cm 2 field were in agreement within 0.25% and 0.5 mm except for surface dose which is around 11%. The maximum variation for 10 3 10 cm 2 field were within 0.25% and 2 mm except for surface dose which is around 10% for both photon energies. Similarly, the maximum variation for 30 3 30 cm 2 field for 6 and 18 MV photons were within 0.25% and 1.4 mm except for surface dose which is around 9%. The PDD results of 5 different electron energies (6, 9, 12, 16 and 20 MeV) for 15 3 15 cm 2 and 25 3 25 cm 2 applicator at 100 cm SSD such as R 50, R p, E 0, E p0 and X-ray contamination were obtained and tabulated in Table XV. The typical electron PDD for 9 MeV obtained through the developed RFA is presented in Figure 10. The maximum variation in results with -RFA and the developed RFA for 6, 9, 12, 16 and 20 MeV electrons were within 0.85% and 1.58 mm for 15 3 15 cm 2 applicator. Similarly, the maximum variation among the results for 25 3 25 cm 2 applicator is 0.2% and 3.1 mm. The beam profile were acquired for 6 and 18 MV photons for 5 3 5 cm 2, 10 3 10 cm 2 and 30 3 30 cm 2 field size at 100 cm SSD. The parameters such as penumbra right, penumbra left, flattens, symmetry and central axis deviation are tabulated comparing with the developed software in Table XVI. The maximum variation among the parameters for both photon beams were 1.27 mm and 1.51% for 5 3 5 cm 2 field, 1.73 mm and 0.73% for 10 3 10 cm 2 field. The maximum variation among both the photon energies for 30 3 30 cm 2 field size were 1.23 mm and 0.4%. The beam profile were acquired for 6, 9, 12, 16 and 20 MeV electrons 15 3 15 cm 2 and 25 3 25 cm 2 applicator at 100 cm SSD. The results such as left and right penumbras, flatness and symmetries for all electron energies for both applicators were presented in Table XVII. Table XV Comparison with developed software (15 3 15 cm 2 and 25 3 25 cm 2 for 6 MeV, 9 MeV, 12 MeV, 16 MeV, and 20 MeV electrons). Energy Parameter Applicator 15 3 15 cm 2 25 3 25 cm 2 6 MeV Electron 9 MeV Electron 12 MeV Electron 16 MeV Electron 20 MeV Electron R 50 23.89 24.60 0.03 23.80 23.60 0.20 R p 29.11 30.60 1.49 28.90 29.90 21.00 E 0 (MeV) 5.57 5.73 0.16 5.53 5.49 0.04 E p0 (MeV) 6.15 6.30 0.15 5.98 6.16 20.18 X-ray 0.20 0.26 0.06 0.20 0.30 20.10 R 50 35.88 36.67 0.79 35.90 36.20 20.30 R p 43.85 44.90 1.05 43.80 42.60 1.20 E 0 (MeV) 8.36 8.54 0.18 8.36 8.44 20.08 E p0 (MeV) 9.02 9.15 0.13 8.94 8.71 0.23 X-ray 0.40 0.66 0.26 0.50 0.49 0.01 R 50 49.95 50.68 0.73 49.70 49.90 20.20 R p 60.02 61.60 1.58 60.70 59.00 1.70 E 0 (MeV) 11.64 11.81 0.17 11.59 11.63 20.04 E p0 (MeV) 12.17 12.51 0.34 12.32 11.99 0.33 X-ray 0.99 1.29 0.30 1.20 1.40 20.20 R 50 65.86 66.15 0.29 66.00 65.90 0.10 R p 79.03 80.50 1.47 79.60 82.70 23.10 E 0 (MeV) 15.35 15.41 0.06 15.37 15.36 0.01 E p0 (MeV) 15.87 16.40 0.53 16.15 16.67 20.52 X-ray 1.99 2.57 0.58 2.30 2.20 0.10 R 50 83.00 83.15 0.15 83.10 84.00 20.90 R p 101.20 102.40 1.20 101.70 101.90 20.20 E 0 (MeV) 19.34 19.35 0.01 19.36 19.35 0.01 E p0 (MeV) 20.18 20.76 0.58 20.61 20.66 20.05 X-ray 3.59 4.44 0.85 3.90 3.70 0.20

Indigenous Three Dimensional Radiation Field Analyser 207 Figure 10: Screen showing the display of acquired PDD for 9 MeV electrons for 25 3 25 cm 2 applicator and the results. Table XVI Comparison of with the developed software (5 3 5 cm 2, 10 3 10 cm 2 and 30 3 30 cm 2 for 6 and 18 MV photons at D max depth). Data Energy Parameters 5 3 5 cm 2 10 3 10 cm 2 30 3 30 cm 2 6 MV 18 MV Pen. Left 2.50 2.89 20.39 3.02 4.67 21.65 2.64 3.84 21.20 Pen. Right 2.51 2.96 20.45 2.94 4.67 21.73 2.64 3.85 21.21 0.50 0.60 20.10 1.19 0.92 0.27 1.90 1.58 0.32 0.10 0.20 20.10 0.18 0.40 20.22 0.00 0.20 20.20 Pen. Left 1.79 3.05 21.26 5.34 6.43 21.09 3.33 4.56 21.23 Pen. Right 1.78 3.05 21.27 5.48 6.37 20.89 3.33 4.56 21.23 0.30 1.81 21.51 0.91 0.95 20.04 2.20 2.21 20.01 0.10 0.30 20.20 0.48 1.21 20.73 0.00 0.40 20.40 The variations for electrons were found to be within 1.49% and 1.75 mm for 15 3 15 cm 2 cone among all electron energies. Whereas the maximum variation observed for 25 3 25 cm 2 applicator were found within 0.4 mm and 1.5%. A typical electron profile obtained for 20 MeV with 15 3 15 cm 2 applicator is shown in Figure 11.

208 Ganesh et al. Table XVII Comparison with the developed software (15 3 15 cm 2 and 25 3 25 cm 2 applicator for 6 MeV, 9 MeV, 12 MeV, 16 MeV and 20 MeV electrons). Energy Parameters 15 3 15 cm 2 25 3 25 cm 2 6 MeV 9 MeV 12 MeV 16 MeV 20 MeV Pen. Left 8.83 8.92 0.009 8.6 8.4 0.2 Pen. Right 8.22 8.83 0.61 8.1 7.9 0.2 0.9 0.88 0.02 1.5 1.2 0.3 1.94 0.45 1.49 1.5 1.3 0.2 Pen. Left 7.15 8.48 1.33 7.8 7.5 0.3 Pen. Right 7.1 8.69 1.59 7.4 7.2 0.2 0.92 0.89 0.03 1.6 1.4 0.2 1.75 1.01 0.74 1.4 1.2 0.2 Pen. Left 8.26 9.87 1.61 7.6 7.3 0.3 Pen. Right 8.02 9.57 1.55 8.1 8.5 20.4 0.9 0.86 0.04 1 1.2 20.2 1.31 0.78 0.53 1.2 1 0.2 Pen. Left 9.82 10.72 0.9 8.3 8.7 20.4 Pen. Right 9.04 10.79 1.75 8.3 8.5 20.2 0.9 0.86 0.04 1.5 3 21.5 1.13 0.38 0.75 1.1 1.2 20.1 Pen. Left 9.82 11.03 1.21 9.3 9.2 0.1 Pen. Right 9.34 10.75 1.41 9.3 9.1 0.2 0.88 0.84 0.04 2.1 2.3 20.2 1 1.5 0.5 1.2 1.8 20.6 Figure 11: Screen showing the display of acquired profile for 20 MeV electrons for 15 3 15 cm 2 applicator and the results.

Indigenous Three Dimensional Radiation Field Analyser 209 Conclusion The overall performances of premeasurement checks as per TG106 were found satisfactory with the developed RFA. The validation of the beam by exporting the files of the other vendors showed good agreement and proved the confidence of the developed software. The comparison of the photon PDDs results with BJR25 supplement values also gave good agreement (within 2% or 2 mm) with the measured. The flatness and symmetry results for photon and electrons satisfies TG 40 recommendation (2% for photons flatness and 3% for electrons flatness from the base line value; 3% for symmetries of both electron and photons). The outcome of the study is encouraging and has a wider scope for imparting the same into clinical use. Further improvement of the developed system with wireless technology and incorporation of additional softwares for obtaining parameters for Flattening Filter Free (FFF) beams is also feasible. Conflict of Interest We certify that regarding this paper, no actual or potential conflict of interest exists; the work is original, has not been accepted for publications nor is concurrently under considerations elsewhere, and will not be published elsewhere without the permission of the editor and that all author have contributed directly to the planning, execution or analysis of the work reported or to the writing of the paper. Acknowledgement The Authors thank Atomic Energy Regulatory Board (AERB), India for the financial support for developing the system. The Authors also thank Mr. T. Vijayareddy and Mr. V. P. Sundraraj for their technical support. References 1. Ramnath, T., Deenu, N., Nandakumar, A. Projections of Number of Cancer Cases in India (2010-2020) by Cancer Groups. Asian Pacific J Cancer Prev 11, 1045-1049 (2010). PMID: 21133622 2. Sonja, D., Carlo, C., Chuang., C. F., Cohen, A. B., Garrett, J. A., Lee, C. L., Lowenstein, J. R., d Souza, M. F., Taylor, D. D., Jr., Xiaodong, W., Cheng, Y. Report of AAPM TG 135: Quality assurance for robotic radiosurgery. Med Phys 38, 2914-2936 (2011). DOI: 10.1118/1.3579139 3. Gopi, S., Ganesan, S., Aruna, P., Sanjay, S. Comparision of beam requirements for MLC commissioning on a TPS. Pol J Med Phys Eng 14, 63-77 (2008). DOI: 10.2478/v10013-008-0006-0 4. Lu,W., Jinsheng, L., Kamen P., Peter, H., Wei, L., Lili, C., Shawn, M., Robert, P., Charlie, M. Commissioning and quality assurance of a commercial stereotactic treatment-planning system for extracranial IMRT. J Appl Clin Med Phys 7, 21-34 (2006). [http://www.jacmp. org/index.php/jacmp/article/view/2125/889] 5. Maitz, A., Wu, A., Lunsford, L., Flickinger, J., Kondziolka, D., Bloomer, W. Quality assurance for gamma knife stereotactic radiosurgery. Int J Radiat Oncol Biol Phys 32, 1465-1471 (1995). [http:// dx.doi.org/10.1016/0360-3016(95)00577-l] 6. Jemema, S., Upreti, R., Sharma, S., Deshpande, D. Commissioning and comprehensive quality assurance of a commercial 3D treatment planning system using IAEA Technical Report Series-430. Australas Phys Eng Sci Med 31, 207-215 (2008). PMID: 18946979 7. Kutcher, J., Coia, L., Gillin, M. Comprehensive QA for radiation oncology: report of AAPM radiation therapy committee task group 40. Med Phys 21, 581-618 (1994). [http://dx.doi.org/10.1118/1.597316] 8. Das, I., Cheng, C., Watts, R. Accelerator beam commissioning equipment and procedures: report of the TG 106 of the Therapy Physics Committee of the AAPM. Med Phys 35, 4186-4215 (2008). [http://dx.doi.org/10.1118/1.2969070] 9. Jordan, T. Central axis depth dose for use in radiotherapy. Br J Radiol 5(Suppl. 25), 62-109 (1996). 10. IEC 60731. Medical Electrical Equipment Dosimeters with ionization chambers as used in radiotherapy. International Electrotechnical. Ed. 3.0 (2011). 11. Nath, R., Biggs, P. J., Bova, F. J., Ling, C. C., Purdy, J. A., Van de Geijn, J., Weinhous, M. S. AAPM code of practice for radiotherapy accelerators: report of AAPM radiation therapy task group No. 45. Med Phys 21, 1093-1121 (1994). [ http://dx.doi.org/10.1118/1.597398] Received: January 7, 2013; Revised: June 6, 2013; Accepted: June 11, 2013