Development of Graphical User Interfaces (GUI) software and database for radiation therapy applications

Transcription

1 The University of Toledo The University of Toledo Digital Repository Theses and Dissertations 2005 Development of Graphical User Interfaces (GUI) software and database for radiation therapy applications Kalyan Adhikary Medical University of Ohio Follow this and additional works at: Recommended Citation Adhikary, Kalyan, "Development of Graphical User Interfaces (GUI) software and database for radiation therapy applications" (2005). Theses and Dissertations This Thesis is brought to you for free and open access by The University of Toledo Digital Repository. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of The University of Toledo Digital Repository. For more information, please see the repository's About page.

2 FINAL APPROVAL OF THESIS Master of Science in Biomedical Sciences Development of Graphical User Interfaces (GUI) Software and Databases for Radiation Therapy Applications Submitted by Kalyan Adhikary In partial fulfillment of the requirements for the degree of Master of Science in Biomedical Sciences Date of Defense: August 19, 2005 Major Advisor E. Ishmael Parsai, Ph.D. Academic Advisory Committee John J. Feldmeier, D.O. Michael J. Dennis, Ph.D. Dan Schifter, M.S. (Member at Large) Dean, College of Graduate Studies Keith K. Schlender, Ph.D.

3 Development of Graphical User Interfaces (GUI) Software and Database for Radiation Therapy Applications A Dissertation Presented to Radiation Oncology Department Medical University of Ohio IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE OF MASTER OF SCIENCE IN BIOMEDICAL SCIENCES (MSBS). BY Kalyan Adhikary Medical Physics Radiation Oncology Department Medical University of Ohio Toledo, Ohio August 2005

4 Development of Graphical User Interfaces (GUI) Software and Database for Radiation Therapy Applications Kalyan Adhikary Radiation Oncology Department Medical University of Ohio Toledo, Ohio August

5 Disclaimer This software package is designed to assist the qualified Medical Physicist or dosimetrist in the use of Physics Application. Before operating this software, the user must be familiar with technical and theoretical aspect of medical Physics. The Authors are not responsible for how the package is utilized, for any acts of omissions or calculation flaws. Please use application at your own risk. Authors E.I. Parsai Ph.D. K. Adhikary M.S. 3

6 Acknowledgements At the outset, I would like to express my sincere gratitude to my honorable supervisor Dr. E. I. Parsai, Associate Professor, Radiation Oncology Department, Medical University of Ohio, Toledo, OH, and Dr. J.J. Feldmeier, Chairman and Professor of the Radiation Oncology Department for their constant inspiration, sincere efforts, valuable suggestions, stimulating supervision throughout the my project. I humbly pay my sincere respect to Dr. M. Dennis, Associate Professor, Diagnostic Medical Physics, Medical University of Ohio, Toledo, OH and Dan Schifter for his valuable suggestions and guideline. I would like to express my deep appreciation to other staff physicians, nurses, dosimetrist, and therapists for their help and cooperation during clinical work. I would like to thank my friends Murshed Khadija, Chul lee, Julie Deanna for their encouragement and help in various means I am highly indebted to my respected father Prof. Dr. S.M. Adhikary and Mother Chandra Prabha Adhikary, brothers and sisters for their inspiration and Bishwa K. Aryal for her continuous attention to my project and thanks for reminding me about the value of time. Kalyan Adhikary 4

7 Table of Content Page number 1. Introduction Objectives of the thesis Literature Review Materials and Methods Results Discussion Conclusion References Abstract Appendices 68 5

8 ABBREVIATION MU : Monitor Unit CTPS: Computer Treatment Planning System 3D: Three Dimensional QA: Quality Assurance AAPM : American Association of Physicist in Medicine SRS: TMR: PDD: OAD: PC: Stereotactic Radiosurgery Tissue Maximum Ratio Percentage Depth Dose Off axis Distance Personal Computer ODBC: Operational Database Connection RDBMS: Relational Database Management system PB6.0: PowerBuilder Version 6.0 CSE: Client Server Environment 6

9 INTRODUCTION In recent years, the process of delivering radiation dose for treatment of cancer patients has become more complex and sophisticated. The goal of radiation therapy, however, has not changed. i.e. delivering maximum radiation dose to the tumor volume while protecting the surrounding normal tissue at a minimum level. To achieve this objective, three dimensional (3D) treatment planning systems have been developed with ability to not only modulate the intensity of each beam, creating dose compensator for target dose uniformity, but to inverse the process of dose computation with objectives such as minimal dose to critical structures, maximum dose to target, and uniform dose within a given volume. Similar advancements are observed in brachytherapy discipline where inverse planning can compute the dwell times for delivering radiation dose to a target and the goodness of the calculations need to be verified by the medical physicist. This has increased the need for development of a comprehensive set of quality assurance (QA) tools that can be implemented in a clinical setting and be used in conjunction with treatment planning systems. These QA tools are used to reduce the mistakes made in radiation oncology and to improve the quality of care. Even with implementation of extensive computer power in the field of radiation oncology, human mistakes are still a major source of error from the early stage of field setup to the execution of a treatment plan. A serious human error can cause a therapeutic treatment to fail therefore it is of fundamental importance to eliminate serious human errors during monitor units calculations. Calandrino et al (1) reported on 1,926 controls collected in about 18 months. Serious daily errors rate (errors causing a 5% or higher discrepancy on the daily reference dose) was 1.4% (27/1926). Serious global errors incidence (errors causing a 5% or higher discrepancy on the total reference dose) was found to be 0.9% (15/1,731). They reported that the human error in MU calculation is not negligible; they also indicate the value of the independent control of MU, which is an 7

10 important tool for quality assurance in radiotherapy. In this work the human error incidence in MU calculation is evaluated by an independent MU calculation check. With the increasing of radiotherapy computer treatment planning systems, verification of the treatment is an important component of a quality assurance program. The radiation dose delivered to a patient is based on treatment machine monitor units (MUs) that are calculated either using data tables or within the computer treatment planning system. An independent method for checking radiotherapy MU calculation has been developed chan J et al (4) reported the comparison between the treatment plan and hand calculation monitor units: result of three years clinical experience. The scope of the QA needs for treatment planning is quite broad, encompassing image-based definition of patient anatomy, 3D beam descriptions for complex beams including multi-leaf collimator apertures, 3D dose calculation algorithms, and complex plan evaluation tools including dose volume histograms. The American Association of Physicists in Medicine (AAPM) Task Group 51(2) has recommended an organizational framework for the task of creating a QA program which is individualized to the needs of each institution and addresses the issues of acceptance testing, commissioning the planning system and planning process, routine quality assurance, and ongoing QA of the planning process. This report, while not prescribing specific QA tests, provides the framework and guidance to allow radiation oncology physicists to design comprehensive and practical treatment planning QA programs for their clinics. As part of developing a QA package, computation of monitor unit (MU) for each beam using an independent data base other than the treatment planning systems becomes extremely important. A monitor unit is a quantity of absorbed dose in tissue which is related to the quotient dє/dm, where dє is the mean energy imparted by ionizing radiation to the material of mass dm. If 100 ergs of energy gets absorbed in one gram of absorbing material, it is said that one rad or one centi-gray of dose has been absorbed. In most accelerators, the quantity of one MU is set equal to 1 rad at a depth of 8

11 reference for that beam energy according to the AAPM TG-51 protocol. The treatment planning system which contains the beam energy data will compute the required MU to deliver the prescribed dose and the monitor unit calculation program, using an independent data set will compute the same. These values should be reasonably close. For quality assurance purpose the monitor units may be calculated by simple method similar to a hand calculation where some errors could occur during calculation in selecting book values, reading tables, etc. The MU is computed as only a point dose within a given volume and therefore is generally less accurate than the MU computed by the treatment planing software which is obtained in visual environment by using a very complex monitor unit algorithm (5). In this project, the monitor unit calculated from using the software tools will be compared with the treatment planning done in ADAC planning system. Another aspect of the project is to develop external beam calibration window application according to the general formalism of the TG51 protocol (2). In addition to these QA tools, another module will be created to compute the accumulated dose to a point in a target volume from brachytherapy seed implantation. This dose will be compared with that of a treatment planning system designed for prostate seed implant, which allows the target outlines from the volume study to be digitized into the computer. This particular module uses ultrasound images of prostate obtained during seed implantation to compute a secondary dose calculation. The implant is planned with an inter-seed distance 1 cm and each seed is 0.5 cm in length. The computer software allows inserting the seed in each slide of the ultrasound images. The individual seed can be inserted or deleted in each slides of image. The worksheet, specifying about the seed location, number of seed and number of needles, can be produced by the approved plan. 9

12 OBJECTIVES The following objectives have been undertaken to work in this project. 1. To develop the GUI software tool for hand calculation of a point dose for photon and electron dosimetry. 2. To develop the interfaces for external beam calibration under the basis of TG To find out the dose to arbitrary reference points for prostrate seed implant and compare the result to the real time plan. 4. To develop the interface for calculating monitor units as a second check to the Stereotactic Radiosurgery (SRS) treatment plans. 5. To develop the various utilities such as reports pertaining to the patient information, monitor unit hand calc application, TG-51 beam calibration and dose comparison in prostrate seed implant as a secondary check. 10

13 LITERATURE REVIEW Power Builder programming is well suited to official solutions because of its interfacing capability with major client/server databases, and because of its security and data integrity feature. PowerBuilder is a visual application development environment for client/server database applications. This is a product from Sybase Company Inc. Its main feature is its object-oriented approach to database creation. It has multi-processor and multi-client access with central database system. The client from different region can get access to the central database and can interact with sole database directly that is client can update, insert, delete and select the database tables. Basically the PowerBuilder can be supported world renowned database Oracle as well. PowerBuilder applications can connect to several different databases like DB2, Oracle, and Sybase, as well as with ODBC. PowerBuilder application services are useful in cross-platform development and deployment, and include support for Macintosh, Windows NT, Windows 95, and UNIX platforms. PowerBuilder programming can also be used for web-based applications and can provide a browserbased interface. PowerBuilder's integrated development environment (IDE) helps in easy development and deployment of client/server applications. It comprises an object-oriented programming language called Power Script, along with visual programming tools and a C++ compiler that generates distributable clients and servers. Other parts of the PowerBuilder development environment include an extensive class library, and a set of utilities called painters for building and managing database objects. It provides a painter for each type of object. Applications in PowerBuilder are event-driven, and are scripted with Power scripts The advantages of PowerBuilder include 11

14 PowerBuilder applications are based on an open architecture, and can connect easily to popular databases PowerBuilder can be used for cross-platform development services It is a commercial software tool and has excellent support and resources. PowerBuilder programming is object-oriented and uses class libraries. PowerBuilder supports the use of third party reporting tools. It is an objected oriented GUI software tools and able to promote various requirement of industrial and complex software applications. GUI A program interface takes advantage of the computer s graphics capabilities to make the program easier to use. Well-designed graphical user interfaces can free the user from learning complex command languages. On the other hand, many users find that they work more effectively with a command-driven interface, especially if they already know the command language. PowerBuilder application development services are useful in cross-platform development and deployment. PowerBuilder includes support for Macintosh, Windows NT, and Windows. PowerBuilder empowers developers to cut through all the hype and make the most out of the latest technology trends and get their job done. It makes building applications that solve business needs easier, faster. Whether your business requires delivering 2-tier, Web, or distributed applications, PowerBuilder will help you achieve your goals quickly, deploying wherever your applications need to run. Object-Orientation Implementation: Supports inheritance, encapsulation and polymorphism, with the ability to overload methods at the same object without using inheritance for the same. SQL Support: PowerBuilder supports SQL and Stored Procedures using Data Window and embedded/dynamic SQL and remote procedure calls. 12

15 Data Window : Data Window control is the heart of PowerBuilder and is used to display data in a wide variety of presentation styles Freeform, Tabular, Grid, Labels, Group, N-up, Rich Text edit, Graph, Cross tab, OLE 2.0 and Composite by executing SELECT statements or Stored Procedures in the database. They can also be populated programmatically. Data Window automatically updates the data source just by writing a few lines of Power Script code. Embedded/Dynamic SQL: PowerBuilder supports both embedded and dynamic SQL, including scrollable cursors and Stored Procedure execution. Remote Procedure Calls: It also supports calling Stored Procedures and procedures using function-calling notation (programmers in the industry call this remote procedure calls' even though the actual meaning of 'remote procedure call' is differs from this). Database Connectivity: Database connectivity is its strong point. ODBC Drivers: Supports all popular databases Sybase/Microsoft SQL Server, Informix, Oracle, and DB2-- using ODBC 3.0 drivers. Native Database Drivers: Provides native database drivers for Oracle 8.0, Informix 6.2, Sybase SQL Server 11.1 and Sybase Adaptive Server Enterprise Dynamic Data Exchange: PowerBuilder supports DDE at window object level. PowerBuilder application can act as a DDE client or DDE server or both. OLE 2.0 Support: PowerBuilder supports OLE 2.0 including OLE 2.0 automation from version 4.0 onwards. Data Window Presentation Style: Data can be displayed in any of the OLE 2.0 server's format. OCX Control: OCX control can be inserted in Data Window like any other object. 13

16 OLE 2.0 Automation: This feature was introduced in version 4.0. PowerBuilder can act as an OLE 2.0 client, server or both. V6.0 supports DCOM(Distributed Component Object Model) Data Window Plug-in: Used basically to display Data Window reports on the web Window ActiveX Control: Functionality similar to Window Plug-in --Plug-in is Netscape's way of running other applications in its browser, and 'ActiveX' is Microsoft's method. It also supports secure mode also. Web PB Class Library: Used to generate HTML dynamically at the web server level 1. MU CALCULATION For MU calculation, the following factors need to be considered. a. Beam energy b. Field size or equivalent field size c. Percentage blocked(mlc) d. Technique e. Prescribed dose and doctor s signature f. OAF factor g. Wedge and OAWCF h. Type of block i. TMR, PDD, Beam output factor(sc) and phantom scatter factor(sp) j. Treatment depth and its field size Beam energy: Beam energy is one of the important factors for monitor unit calculation. Higher the energy, greater is the depth of maximum dose. 14

17 Field size and its equivalent area: The field size is one of the most important parameter in treatment planning. The field size is more important because of the scatter beam energy which makes significant different while calculating dose to the patient. This determination must always be made dosimetrically rather than geometrically. The field size will be decided for treatment upon the coverage of tumor. For calculating the MU, the equivalent field size is required to choose the various factors i.e. TMR, PDD, Sp, Sc, etc. To find out the equivalent field size on the skin surface, following formula is used. Equivalent area = 2 lx b/ (l+b) The field size can be different at certain depth so for that depth the field size would be the more than field size on surface. The following formula can be used to find the equivalent field size at depth d. Field size at depth d = rd = r (f+d)/f Where f is source to surface distance. r is field size at surface and d is treatment depth. Percentage blocked and Multi leaf collimator (MLC) The multileaf collimator is basically only for photon beam and use for beam shaping. A multileaf collimator for photon beams consists of a large number of collimator blocks or leave that can be driven automatically, independent from each other. Generally the field size has percentage of blocked area. So the blocked area minimizes the field size and gives small field size. The all parameters will be calculated as per the blocked area. MLC is not only the means to block the field size and sometime for complex field size the custom block can be used and makes change in field size. The factor is going to change as MLC off but custom block on. 15

18 Techniques Mainly the MU calculation are done under two basic techniques 1. SAD(Source and axis distance or iso-centric technique ) 2. SSD(Source to surface distance) SAD Technique: TMR value is chosen for dosimetric calculations involving other factors. Monitor unit is calibrated in iso-center as 1 cgy/mu from the TG 51 protocol. All values are calculated and standardized to its specific field size (10x10). At the reference depth, the required monitor units are calculated from the following formula and MU calc program is also developed under the following formula. MU = Tumor Dose (1) K x TMR (d, rd) x S c (r c ) x S p (r d ) x (SAD) factor x OAD factor x Oawcf Where SAD factor = (SCD/SAD) 2 TMR = tissue maximum ratio d = Treatment depth r d = Field size in depth d Sc = it is ratio of dose for the given field at reference depth to the dose rate at the same point for the reference field size (ro), with the same collimator opening. Sp = it is the change in scatter radiation originating in the phantom at the reference depth as the field size is changed. K = conversion factor (cgy/mu) 16

19 Tumor dose = the dose prescribed by the oncologist and has a unit of cgy or Gy or rad SSD Technique: Other technique is involved to calculate the monitor unit for photon energy. In this technique, percentage depth values are selected to calculate the MU calculation. The machine is generally calibrated on SSD technique with the field size 10x10 cm 2 The following formula is used to calculate the dose at reference depth. MU = Tumor Dose (2) K x %DD d x S c (r c ) x S p (r) x (SSD) factor x OAD factor x Oawcf Where K is 1 cgy per monitor unit, r c is the collimator field size, given by rc = r(sad/ssd) Or SSD factor = (SCD/ SSD + dmax) 2 Prescribed Dose According to the prescription, the prescribed dose will be delivered to the patient monitor unit (MU). During dose calculation, we can have the normalization which is also getting from physician s signature as the approval of plan. The normalization is also responsible for changing the monitor unit. Off axis distance correction factor: The off axis distance correction factor also equally important during the monitor unit calculation. The off axis factor is used if the calc point is off from the central axis. By the time under the consideration of factor the monitor unit can be close to the required value. This is not very often we use to calculate the monitor unit. All factors for various distance have been taken from the wellhofer scan. 17

20 Wedge and off axis wedge correction factor This value is factor only when the wedge is using in the plan. It also shows the direction of wedge. The wedge has hill and toy side, each side has different blocking factor to the beam or the stopping power changes as per the thickness of wedge. For oblique beam or curved surface for the contour can be approximated with a straight line, standard compensating wedges are very convenient. Compensating wedge is fabricated from the metal such as copper, brass, lead. They are designed to compensate for the missing volume of tissue. Wedge filter can be used effectively as a compensator. It is primarily designed to change the shape of isodose line through the certain wedge angle. The wedge can be used to improve the dose uniformity in the fields. Type of block: MLC is not only the means to block the field size and sometime for complex field shape a custom block is used. The block factor is going to change as MCL off but custom block used. The MLC moves along the x-axis or cross-plane. For y-axis the independent jaw or back up jaw moves to block the field size. For complex field shape one uses a custom irregular block second its block factor. Tissue maximum ratio (TMR): TMR is the ratio of the dose at the given point in the phantom to the dose at the reference point of maximum dose. TMR = dose at given point/ dose at reference point where the dose is maximum The depth where the dose is calculated should not be in build up region and should be more depth than the depth where the maximum dose deposited. TMR is based on the assumption that the fractional scatter contribution to the depth dose at a point in independent of the divergence of the beam and depends only on the field size at the point and the depth of the medium. 18

21 For many treatment planning systems tissue maximum ratios (TMR) are required as input. These TMR can be measured with a 3D computer-controlled water phantom; however, a TMR measurement option is not always available on such a system. Alternatively, TMR values can be measured 'manually' by lowering the detector and raising the water phantom with the same distance, but this makes TMR measurements time consuming. Therefore, TMR values can be derived from percentage depth dose (PDD) curves Percentage depth dose (PDD): As the beam enters into the phantom or any medium then the absorbed dose or energy fall as the depth increase after the dmax point. Before dmax point the build up region the dose deposited rises with depth and reached its maximum deposited dose point and the distance from surface to that point called dmax. Beyond dmax the deposited dose ratio falls with depth. The fall in dose deposition depends upon various factors,includes beam energy, depth, field size, and distance from source and beam collimation system. Thus the calculation of the dose in the patient involves considerations in regard to these parameters and others as they affect depth dose distribution. The quantity of the percent depth dose is defined as the percentage ratio of the dose deposited in given point to the dose at dmax along the central axis. Or PDD = Dd/Ddo x 100% The percentage depth dose beyond the depth of maximum dose increases with the beam energy. Higher energy beams have greater penetrating power and thus deliver a higher dose at depth. If the scatter beam does not consider, the dose deposition fall as exponential attenuation. SAD and SSD factors: The photon energy decayed by point source of radiation varies inversely as a square of the distance from the source. Percent depth dose increases with SSD because of the effect of 19

22 the inverse square law. Although the actual dose rate at a point decreases with increase in distance from the source, the percent depth dose, which is the relative dose with respect to a reference point, increases with SSD. In clinical radiotherapy, the SSD is a very important parameter. Since percent depth dose determines how much dose will be delivered at depth relative to the surface dose or dmax, the SSD needs to be as large as possible. Since the dose rate decreases with distance the SSD is set at a distance which provides compromises between dose rate and percent depth doses. The SSD factor is given by the SSD factor = SSD factor = (SCD/ SSD + dmax) 2 Clinically, the SAD factor is very important. The SAD factor is calculated from the dmax of the beam energy and point where the beam has been calibrated. The source to surface distance is always less than 100 cm, and the dmax is taken from beam energy. The depth d is taken where the reading is taken. SAD factor = (SCD/SAD) 2 Sp (Phantom scatter factor): Photon beam treatment planning systems (TPS) typically split the total output factor, Scp, into two components, namely the collimator scatter factor Sc the phantom scatter factor, Sp. The standard method for determining Sp is to measure Sc and Scp for symmetric fields and then divide the measured Scp by Sc. Split of Scp into the two components Sc and Sp is important for dose and monitor unit calculations. Currently many TPS require entry of Scp, Sc and Sp data at the depth of maximum dose (dmax). In addition, hand calculations and in-house developed computer programs also use these data at dmax. 20

23 It is known as a ratio of the backscatter factor (BSF) for the given field to that for the reference field. Or Sp = BSF(r)/ BSF (ro) Where r is the field size in given depth and ro is the reference field to that depth. It is hard to calculate independently so it is calculated from the more practical way. Sp at given depth at reference field = Scp/ Sc where the Sc is collimator scatter factor and Scp is total output factor. Collimator Scatter Factor (Sc) Commonly called output factor and can be measured with an ion chamber. It is the factor taking by the ratio of the output in air for a given field to that for a reference field i.e. 10x10 cm 2. Generally it is measured at the source to axis distance (SAD). Treatment depth and its field size: The field size increase as the depth increases. Thus the factor for TMR is going to change with field size and depth. Surface field is not the final field size to choose the TMR or PDD value. To find out the field size at depth d the following formula can be used, r d = r(f+d)/f Where f is SSD d. is depth from surface r is field size For the MU calculation of electron beams, following equation is used MU = Prescribed dose (3) Applicator factor x blocking factor x SSD factor x normalization 21

24 For the monitor unit calculation of stereotactic radiosurgery, following equation is used MU = Dose per arc (4) (TMR) at avg depth x 1.03 x output factor 2. AAPM TASK GROUP 51 (TG-51) The window basically describes the general procedure for clinical reference dosimetry. It applies to photon beams with nominal energies up to 50 MV and electron beams up to 50Mev. This software application needs various requirements while measuring the beam consistency as well as the beam calibration. The TG-51 protocol is main source of general formula and derivation during the beam calibration by this software. The ion chambers used in this window application is calibrated in terms of absorbed dose to water in a 60Co beam. It is to ensure uniformity of reference dosimetry in external beam radiation therapy. In order to achieve this result, it requires a common starting point and this is accomplished by starting with an ion chamber calibration factor which is directly traceable to national standards of absorbed dose to water maintained by NIST. Much of the data used in this application apply only under certain well-defined reference conditions and taken from TG51 protocol. These conditions are specified below for photon and electron beams, and include such factors as the depth of measurement, field size, and source-to-surface distance, SSD. The calibration factor from the NIST laboratory is major factor denoted by N 60 Co D,w should not exceed by 2 years from the date of calibration. N 60 Co D, w = N 60 Co w /M (Gy/C,Gy/rdg) D Q w = M N Q D, w Where D Q w is the absorbed dose to water at the point of measurement of the ion chamber when it is absent. M is fully corrected electrometer reading in coulombs (C) which has 22

25 been corrected from ion recombination, polarity and electrometer calibration of the temperature and pressure. There is also one more factor should be considered during the calibrating beam that is k Q. N Q D,w = k Q. N 60 Co D, w (Gy/C or Gy/rdg) k Q is used to convert the absorbed-dose to water calibration factor for a cobalt beam into the calibration factor for an arbitrary beam of quality Q which can be for photon or electrons. The quality conversion factor for photon beam is chamber specific. D Q w = M. k Q. N co60 D,w..(4) For photon beams, the quality conversion factor is given in protocol. The protocol uses ion chamber with absorbed-dose-to-water calibration factors, N co60 D,w, which are traceable to the National Primary Standard. Where Q is the beam quality of the clinical beam, D Q w is the absorbed dose to water at the point of measurement of the ion chamber placed under the reference condition, M is fully corrected ion chamber reading and kq is quality conversion factor. The corrected M is given by Pion x Ptp x Pele x Ppol x Mraw. Where Mraw is uncorrected reading. Pion corrects the ion recombination, Ptp is temperature and pressure correction factor, Pele is inaccuracy of the electrometer reading, Ppol is chamber polarity correction factor. The reference depth of measurement is 10 cm for photon beam and field size is 10x 10 cm 2 3. PROSTRATE SEED IMPLANT The seed implants with iodine-125 and palladium-103 are used for treatment of early stage prostate cancer sometime combined with teletherpay. There are two types of seed implants used for prostate glands, one is temporary and other is permanent. The temporary seed implant the half life of the source is high and with sufficient dose rate to deliver the 23

26 prescribed dose to the target. The sources are removed after the certain number of days. But for permanent seed implants the sources have a short half life and deliver the dose over a long term with enough low photon energy. From the above seed implants the permanent seed implant is reliable and available. The seed of the iodine-125 or palladium-103 are inserted into the prostate gland with the guidance of the ultrasound pictures and perineal template. The procedure is not surgical and is performed on an outpatient basis. A treatment planning system designed for prostate gland implant allows the target outlines from the volume study to be digitized into the computer. The implant is planned with an inter-seed distance 1 cm and seed is 0.5 cm length. The computer software allows inserting the seed in each slide of the ultrasound images. The individual seed can be inserted or deleted in each slides of image. The worksheet, specifying about the seed location, number of seed and number of needles, can be produced by the approved plan. From the DVH, the total dose strength to the prostate, isodose lines, percentage of the dose to the prostate volume, urethra volume, rectum and bladder can be determined. 24

27 MATERIAL AND METHODOLOGY Materials used 1. PowerBuilder 6.0 version CD and deployment kit tool 2. ADAC treatment planning system 3. Task Group protocol TG51 and TG Prostate seed implant slices. 5. Software module for application(application platform and Database table) 6. Dosimetry Book from Physics Department for various data 7. TMR and PPD, wedge factor, Sp, Sc, Scp, OAD factor, OAWCF and British Journal table and relevant values required for measuring the factors and value on different field size. 8. 3D conformal planning reports from various cases. 9. TG 51 protocol beam output check for photon 10. Plan reports from prostate seed implant 25

28 METHOD A. Monitor Unit Calculation for Photon Beam The monitor units calculation program was done in PowerBuilder, Version 6.0 programming tools. The software tools were installed on a personal computer the database created as required shown in figure 1 to 16. The basic working principle follows the algorithm of the radiotherapy system. After the software was installed, the various software interfaces were developed. The required scripts are listed in the appendices. For MU calculation software development, the main calculating principle followed the formula given by Khan (10). The various factors were taken into consideration during software development. These factors included beam energy, field size or equivalent field size, percentage blocked (MLC), technique, prescribed dose, OAD factor, wedge and Oawcf, type of block, TMR, PDD, beam output factor (Sc) and phantom scatter factor (Sp), treatment depth and its field size. The monitor units for photon beam were calculated by using the software tools and were compared with the plan done in ADAC planning system. 26

29 Fig 1: Power Builder installation window and database connection platform(fig taken during the software installation) 27

30 Fig2. PB has various modules and one the module shown in figure. The module selects the development environment and database connection path. 28

31 Fig3. Menu window 29

32 Fig4. The list of the library files showing all the application windows. 30

33 Fig5. Database tables 31

34 Fig6. The relational database system, the one table is connected to other by its primary key. 32

35 Fig7. The data in table, the data can be manipulated by the database administrator. 33

36 Fig8. The library file where all application are located with additional information 34

37 Fig9. The datawindow library file where all datawindow library files are located. 35

38 Fig10. Database connection window. 36

39 Fig11. Creating new datawindow for application 37

40 Fig12. Creating new window from painter bar 38

41 Fig13. General method to create the window and datawindow 39

42 Fig14.The database profile window is to select the module of interest. 40

43 Fig15. The pbl library files where all applications are located. 41

44 Fig16. The application tool 42

45 B. MU Calculation for Electron Beam For MU calculation of electron beam, different factors such as applicator factor, blocking factor, SSD correction factor and normalization percentage were used (eq. 3) C. Monitor Unit Calculation for Stereo-tactic Radio surgery (SRS) The other interface developed was the monitor unit for SRS. The interface used the SRS algorithm and found out the monitor units under different depth and cone size variation. The monitor unit per arc was calculated depending upon the beam weight per arc (eq. 4) D. TG 51 Interface: All factors and values were based on the TG51 protocol. The algorithm used in application was taken from the worksheet of TG51 protocol. This protocol uses the ion chamber with absorbed dose to water calibration factor. The various factor such as ion recombination factor, electrometer correction factor, polarity correction factor and temperature and pressure correction factor were used to find the fully corrected electrometer reading. The fully corrected reading was multiplied by other factors such as beam quality conversion factor and chamber calibration factor and then fully corrected dose per monitor unit was calculated. For the photon the standard depth was taken as 10 cm. Coding for the development of TG-51 is shown in appendix. E. Prostate Seed Implant Dose Calculation for Second Check The ultrasound images that were used for prostate seed implant planning from seed computer were taken into personal computer as bitmap file and tried to be accurate in the concern of slide resolution and size. Altogether 10 patients images were stored in local folder. The images were browsed by assigning path to that folder along with name of the patient. The distance was calculated from the coordinates system. From the coordinates of 43

46 each point, the distance between the seed to reference point could be calculated with the help of pixel values. 44

47 RESULTS Fig 17 shows login window. The login interface is first window developed in PB6.0 visual environment. It initiates the whole program and connect to the database by assigning the connect string and database. This window is mainly used to login to main menu window and it also assigns the user rights to the individual. fig17. Login window 45

48 fig18. Photon beam info interface fig19. Retrieving data from PDD for 6MV energy and interpolation window. 46

49 fig20. Monitor unit calc window for photon beam fig21. Query window for photon beam 47

50 fig22. Photon beam monitor unit calc window for Varian machine fig23. Monitor unit calc window for SL25 electron beams. 48

51 fig 24. Monitor unit calc window for SL15 electron beams fig 25. Monitor unit calc window for Varian s electron beam 49

52 Fig26. Simple query window about applicator factor 50

53 fig27.electron beam monitor unit calculation interface. fig28. Monitor unit calculation interfaces for stereotactic radio surgery 51

54 fig29.prostate seed implant secondary hand calculation interface 52

55 fig30. Equipment enroll window for beam calibration 53

56 fig31. Window for photon beam calibration 54

57 fig32. Electron beam calibration interface 55

58 fig33. Creating user and deleting user interface 56

59 fig34. Interface utilities tools for mathematical calculation The comparison between measured and computed monitor unit from ADAC planning system is expressed as the percentage of the measured dose at the point of interest. The difference between measured and calculated monitor unit is small and generally less than 2%. But some time in wedged beam gives more deviation to the measured value. The measurement and calculation are shown for the clinac Varian machine 2100C, 6 and 18 MV beam. This beam was commissioned in ADAC planning system. Absolute measurement was taken from the real plan. The irradiation conditions include treatment 57

60 fields that were open, wedge, and oblique, asymmetric, centrally blocked, opposed lateral, extended SSD, and heterogeneities. Table1. The monitor units calculated for photon beam with various field sizes, treatment area, SSD, depth, energy, technique, wedge and blocking area. S.N. Beam En/Tech F.S. Wg/Block Depth SSD Dose/wt. Meas. ADAC %Error 1 AP 18MV 15x30 15 w/21% % 2 PA 18MV 15x30 15w/21% % 4 AP 18MV 18x % % 5 Lat 6MV 7x % % 6 AP 6MV 16x % % 7 AP 6MV 11.8x7.0 15w22%Cu %c 8 Ltmed 6MV 10x16 30w/0.0% % 9 Lat 6MV 7.0x % % 10 AP 18MV 15x % % 11 Axilla 6MV 11.1x % % 12 Ltmed 6MV 9.2x w/21.4% 10calc % 13 AP 18MV 16.8x % % 14 RAO 18MV 14.5x % o/a % 15 Lat 6MV 5x4.5 45w/0.0% % The treatment are selected from the various plan module with different criteria such as various field size, energy, treatment site, average treatment depth, with wedge and without wedge 58

61 Table2.Comparison between real plan and software output under the basis of treatment area. S. N. Treatment Site Measured ADAC %Error 1 Brain % 2 H&N % 3 Pelvis % 4 Lung % 5 Prostate % 6 Breast % 7 Spine(15x39) % Table3.Comparison between the real plan point dose and secondary check reference point dose. ID Strength Slices/seed Pt1 Pt2 Pt1(V) Pt2(V) %Error %Error / % -4.1% / % 9.9% / % 1.19% / % 8.33% / % 27% 59

62 Table4. Comparison between SL25 interface with hand calculation. S.N. Energy Appl Cutout Prescribed Measured Regular %Error in Mev size size dose/ssd 1 6 6x6 3.5x % x10 5x6 200/ % x14 10x5 180/ % x20 6x % x25 10x % Table5. TG51 comparison table Nominal Energy Chmr/elemtr. Ctp/pion %dd TG51 Dose/MU Measured %Error 10MV MCOCh/Victo 1.026/ % 6MV 1.028/ % 18MV 1.022/ % 60

63 Table 6: comparison between ADAC and Interface monitor unit for SRS Sno Energy/Dose/wgt Coll. Size Avg SSD Depth TMR Measured ADAC %Error 1. 6/720/ % 2 6/960/ % 3 6/860/ % 4 6/960/ % 5 6/960/ % 6 6/720/ % 7 6/530/ % 8 6/860/ Table6, comparison between ADAC and Interface monitor unit. The calculated data values in tables 6 are close to the plan values. In the MU calculation program the percentage difference does not exceed than 5.0 % except the special cases. On the basis of treatment site, the results are also close to the computer planning system. There is good agreement between the calculated values and the software values. Similarly, the MU calculated for stereo-tactic radio-surgery is close to the computer planning system calculation. The dose calculated for prostate seed implant are also close to the dose taken from Veriseed planning system since the doses are calculated on two arbitrary reference points. Moreover the readings for beam calibration are also close to TG51 protocol. 61

64 DISCUSSION The MU calculation window was basically used as a common method of calculating monitor unit for all machines. The basic algorithm for calculating the monitor units is same for all machines. Only the basic database table has to be updated. The case study was done for various plans with different field size, different depth, different treatment area and different energies. The highest percentage error was found to be 5.12 % in beams with custom block and wedge. The higher discrepancy was found in wedge beam because it needed to have off-axis factor. The beam without wedge gave varies close monitor unit value to the ADAC pinnacle planning system. The monitor units were calculated from small field size to maximum possible field size. Similarly, the monitor units were calculated for various treatment areas such as H & N to femur. The result was quite close to the ADAC pinnacle treatment planning system. The reading from the table II was quite close to the treatment planning system rather than random choice or data from Table I. The Table III data were compared the prostate seed implant data verification with the real time plan. Basically the two points were located to the top of the ultrasound pictures and calculated the contribution from all seed to those points. The software was developed for calculating dose to outer area of the prostate in order to minimize the gradient effect and increase the accuracy to the plan values. The higher percentage of error occurred at higher number of seed used during treatment, bigger size of prostate. The effect of resolution and error during importing image from seed computer could have generated significant error. For TG 51 interfaces, the reading were taken from saved files and compared to those readings. There was no significant difference with existing TG51 software readings. The monitor units calculated in SRS interface was much closed to ADAC planning system. The only the changing factors are depth and beam weighting so the result was much close to the planning system. The TMR values were taken from the Wellhoffer reading. There is 62

65 some limitation that is this software can not calculate the monitor unit for 1 cm cone size because there is no TMR Value in database table for 1 cm cone size. 63

66 CONCLUSION The interfaces have been developed as an alternative of hand calculation. The hand calculation might take longer time and can have more mistakes during calculation. The computerized method is recommended to minimize the human error. It also saves time for medical physicist and dosimetrist during hand calculation. The MU calculation windows are very accurate and can be used for real clinical plan as a second check. The data were tested with treatment plans generated in ADAC pinnacle system. The MU calculated by GUI software was in good agreement with the MU given by treatment plan. The highest percent error was only 5.1 % on beams with custom block and such a plan where the dose calculated on other than isocenter point. Other reports were developed from where we can get dosimetry data. The software also keeps the record in a database allows query whenever required. These software tools allow one to select a record from the database within microsecond, minimize the redundancy of records in the table, interlink between tables with unique parameter and proverb easy access to the out folder into local drive in any computer. Similarly, TG51, MU calculation for SRS, and dose calculation for prostate seed implant software gave very accurate results. This software is very useful in clinical radiation therapy for MU calculation, dose verification, machine calibration and quality assurance. 64

67 REFERENCES 1. Calandrino R, Cattaneo GM, Del Vecchio A, Fiorino C, Longobardi B, Signorotto P.; Human errors in the calculation of the Monitor Unit in radiotherapy. Radiol Med (Torino) Oct;86(4): Almond PR, Biggs PJ, Coursey B.M., Hanson W.F., Huq MS, Nath R, Rogers DW, AAPM TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys 1999;26 (9) C-M Ma, R A Price Jr., J S Li, L chen, L wang, E. Fourkal, L qin and J yang; Monitor unit calculation for Monte Carlo treatment planning, C-M Ma et al 2004 Phys. Med. Biol Chan J, Russell D, Peters VG, Farell TJ; Comparison of Monitor unit calculations performed with a 3 D computerized planning system and independent hand calculation: result of three years clinical experience; J Appl Clin Med Phys Autumn;3(4): Leszczysnki KW, Dunscombe PB;Independent corroboration of monitor unit calculations performed by 3D computerized planning system, J Appl Clin Med Phys Autumn;1(4): Ayyangar K.M, Saw CB, Gearheart D, Shen B, Thompson R; Independent calculation to validate monitor units from ADAC treatment planning system, Med Dosim Summer;28(2): Mark A. Holmas, Ph. D.Photon Monitor unit calculations in pinnacle 8. Radiosurgery Quality Assurance test manual, Medical University of Ohio. 9. Rivard M J, Coursey B.M., Deward L A, Hanson W F, Huq M S, Ibbott G S, Mith M G, Nath R, Williamson J F,Update of AAPM Task Group No. 43 Report: A revised AAPM Protocol for brachytherapy dose calculations. Med Phys 31(3), March Khan F. M., Physics of Radiation Therapy,3 rd Edition,

68 ABSTRACT This software has been developed for various package including monitor unit calculation programming, TG51, prostate seed implant double check interface, stereotactic radio surgery (SRS) monitor unit calc programming and various query and report windows. This application has diversified package for radiation therapy applications. The main aim of this GUI software is: a. To develop the software tool for hand calculation for photon and electron beam and compare the results with ADAC planning system. b. To develop the interfaces for external beam calibration under the basis of TG51 protocol. c. To find out the dose to arbitrary reference points for prostate seed implant and compare the result to the real time plan. d. To develop the interface for calculating monitor units as a second check to the SRS. e. To develop the various reports pertaining to the patient information, monitor unit hand calc application. The results shown on this thesis are close to planning system output. It also checks certain type of restriction and limit. The reports built in this program make lot easier to user finding out the various dosimetry book values in a minute, which also minimize the chance of human error and mathematical error. The record keeping system also mainly focuses on the data verification and saves to the database and can query anytime whenever we need. It is mainly user friendly to those people who want to work on visual environment. Every report and query gives the lot of information and help to reduce the redundancy of the data stored in database. 66