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Essay, 19 pages (5000 words)

The use of radiotherapy biology essay

1. 1. Introduction:

Recently, the usage of radiation therapy has grown quickly due to increasing demand. One of the most utilized Fieldss is in handling malignant neoplastic disease because radiation therapy has the advantage in that it has been claimed to be superior to other malignant neoplastic disease interventions such as chemotherapy and surgery. However, one of the chief issues related to radiation intervention is the degree of uncertainness which is still ambitious radiologists. This is partially related to the prescribed dosage and intervention consequences, as the uncertainness of the delivered dosage is agreed to be up to 3 % . Although much of the uncertainness has been overcome by using a modern 3D intervention planning system, excessively many dose computation mistakes occur in the environing heterogenic tissues. The most common cause of these mistakes is the estimates of the computation algorithm used ( Krieger and Sauer 2005 ) .

Several novel techniques have been introduced to this field to get the better of these jobs, such as Photon beams, pencil beams ( PB ) and superposition/convolution techniques, such as collapsed cone, and are the most modern-day computation algorithms used in 3D planning systems. However, In the instance of PB algorithms, it has been shown that incompetency sometimes occurs when utilizing PB algorithms in nonuniform tissues. One account for this is that in PB algorithms, one dimension is normally used to rectify the denseness, which evidently does non take into history precisely the distribution of secondary negatrons in the country of nonuniform tissues. In the delivered beam, the computation considers the per centum deepness dosage from the radiation beginning to the mark, while the effects of spread or side radiation are non taken into consideration ( Krieger and Sauer 2005 ) . Therefore, farther probes and apprehension of the consequence of the radiation on the tissues is still greatly required. This survey aims to research the consequence of the ionising radiation beam on the meiotic oocyte spindles.

The monolithic developments in computing machine engineering have introduced farther progresss in the medical field. One of the chief applications of the computing machine is the Monte Carlo technique, which has been agreed upon as being one of the best methods for dose computations in the radiation therapy planning system. It has been claimed that utilizing the Monte Carlo simulation chiefly for strength modulated radiation therapy could better the truth of radiation therapy intervention. Presently, the Monte Carlo codifications can be used for many different intents, including for radiotherapy simulation such as Electron Gamma shower version4 ( EGS4 ) . The EGS4 codification system is good known as a really accurate tool for dosimetry in radiation intervention. ( Li and et Al. 2000 ) . This survey was carried out foremost, by using Monte Carlo codification simulation to formalize the processs which are confirmed to be the really best criterion in dose computation ( Krieger and Sauer, 2005 ) .

A apparition with the point beginning from the forepart with rectangular collimation was used. Following, the apparition was constructed based upon the proposed existent apparition by utilizing graphical user interface 1. 1 GUI package. Subsequently on, after accomplishing satisfactory proofs and building, readyings were made for the oocytes to be irradiated. They were so examined under a confocal optical maser scanning microscope ( CLSM ) to analyze the consequence of the prescribed doses on the oocytes spindles. By and large, it has been reported that any dose above 0. 5 Gy could do cell proliferation and induce cell programmed cell death, while less than 0. 5 Gy could perchance heighten the proliferation ( see fig 1 ) .

( Li and et Al. 2000 ; Liu 2002 )Figure ( 1 ) Proliferation of cells after irradiationAnterior surveies note the consequence of the radiation on the spindle, and province that the ionizing radiation may forestall the synthesis of a protein that organizing the mitotic spindle ( Walters & A ; Petersen, 1968 ; Rustad et al. , 1975 ; Dubravsky et al.

, 1976 ; Dubravsky & A ; Withers, 1976, 1978 ) . In contrast, Noland et Al. ( 1974 ) suggest that there is no clear consequence on protein synthesis, shown by microtubules of Chinese hamster ovary cells irradiated by X ray. Another study explains that the formation of the microtubules does non ask protein production, other than playing a dynamic equilibrium function between the microtubule and a pool of its fractional monetary unit. As a consequence, the depolymerisation of the microtubules occurs when the radiation strikes the microtubular protein that appears in the pool, which could take to dynamic instability.

Further probe has shown that the radiation does non ensue in obvious harm in doing microtubular protein debasement on molecular degree. A survey carried out by Zaremba and Irwin ( 1981 ) has shown that irradiation of the tubule spindles by gamma radiation leads to conformational change through cut downing the capableness of the tubulin dimmer to lend to the nucleation and elongation procedure of polymerization ( Zaremba and Irwin 1981 ) . Furthermore, it has been suggested that if microtubules have been broken by radiation, so compared with the control microtubules sample, the undermentioned fluctuations can be noticed.

The length of the irradiated microtubules should be shorter than the control. Furthermore differences in the viscousness degree are perchance more in the unirradiated sample ( Coss, Bamburg et Al. 1981 ) .

Outline of the thesis:

This undertaking has been divided into four chapters. The first chapter is the Introduction ; The Monte Carlo method follows following, and includes background, methodological analysis, consequences and treatment subdivisions. The 3rd chapter will cover cell irradiation in the same layout as the old chapter, and in the concluding chapter, a decision will be given.

Chapter two

Monte Carlo method

Section one

2. 1.

The Background of the Monte Carlo codification

2. 1. 1 History of DOSXYZnrc

DOSXYZ started out as a codification, in March 1986, when Dave Rogers wrote it to show to Ralph Nelson that coding of rectilineal voxels could be performed faster than with Ralph ‘ s more general macros.

The chief purpose of Dave Roger ‘ s presentation was to execute an appraisal of the clip needed to wholly run a Monte Carlo intervention be aftering appraisal, and this went on to be published in a book. That was considered to be the foundation of the Monte Carlo codification. Subsequently on, it was modified and updated often and became accessible via one web site until 2000. Following, the codification was taken up by the MMEGA undertaking which added more versions and updated beginning modus operandis. Updating the codification went still farther, such as cut downing the array infinite used by the codification and presenting beam characteristic input. Blake Walter made great attempts to develop the codification ; in 1996, he added CT reading ability and the DOSXYZ codification was made smaller by dividing out the ctcreate codification in 1997.

Another option which was added in 1998 was to understate the modeling period for deepness dosage curve and dose profiles dose, in add-on to infixing a codification for parallel simulation. In 2001, DOSXYZ codification was ported by Blake Walters with aid of Iwan Kawrakow on the EGSnrc system- so called DOSXYZnrc. Besides, the standard batch attack was replaced with much developed statistical analysis modus operandis.

In 2004, to utilize DOSXYZnrc in a Windows based operating system for the first clip, while it was entirely run under Linux/Unix after porting of DOSXYZnrc to the EGSnrcMP system by Blake Walters and Iwan Kawrakow.

2. 1. 2. Radiation Dosimetry

Any radiation dosimetry in a patient requires consideration of a figure of factors that are involved in the whole procedure ; for case, distribution of the energy charge, location and way of the beam. There are many ways that have been used to characterize the distribution of the atoms: “ usage of empirical or semiempirical beginning theoretical accounts with parametric quantities determined from measurings merely ; usage of compact representations of phase-space informations obtained from full intervention caput simulations, perchance incorporating free parametric quantities adjustable to fit measurings ; and direct usage of the full phase-space informations from intervention caput simulations typically stored in phase-space files ” ( Kawrakow and Walters 2006 )A farther method, which may hold the most accurate beam characteristics, is by following the scenes of the negatron beam hitting the bremsstrahlung mark or vacuity issue window, and this has been detected by comparing the experiments.

However, the utilising of phase-space files is unwieldy in a practical sense for many grounds. First, there is a demand for immense disc infinite to hive away atom informations when more than one beginning of atoms is required, for illustration to accomplish low uncertainness when choosing little voxels. Second, when doing any alterations in the geometry, such as jaws or multileaf collimator, it is necessary to animate phase-space files. One of the most ambitious issues involves recovering phase-space informations through a web file system. ( Kawrakow and Walters 2006 ) .

2.

1. 3. Use of Megavoltage Beams

The usage of megavoltage beams in radiation therapy has become widely used. With such energy beams, it is important to cognize about the energy spectra and angular distribution of the beam. This consciousness is indispensable for radiation dosimetry. One of the chief advanced methods for dosimetry intents is the usage of the Monte Carlo codification. The Monte Carlo method enables the radiologist to obtain angular measures and distributions which can non be measured in experiment. Besides, it facilitates bring forthing an energy spectrum in an country off from the Centre of the beam, instead than the cardinal country.

Another of import characteristic of using Monte Carlo is the fact that it has been possible to accomplish nest eggs in the labour force due to much of the work being carried out on a Personal computer. For case, put ining Monte Carlo package on a computing machine means it can be used for all gas pedals with the same geometries. In fact, it is possible to obtain accurate energy spectra by trusting on the Monte Carlo method, and the form of the intervention caput can be accurately simulated. Monte Carlo package can be used to bring forth energy spectra and angular distributions, and so to cipher dose distributions. Accuracy is obtained in dose computations by sing the transit of the photon and negatron. ( Mohan, Chui et Al.

1985 )Furthermore, one of the most accurate tools for ionizing radiation dosimetry is the Monte Carlo simulation. Hence, it has been extensively considered and used by radiologist for clinical radiation interventions.

2. 1.

4. Advantages of Monte Carlo

The innovation of new novel dose measuring methods is really much needed because of the drawbacks of analytical methods when utilizing 3-D execution of the pencil beam algorithm, as it suffers from unacceptable uncertainness ( about 10 % ) from a radiologist ‘ s point view- peculiarly in heterogenous tissues. Therefore, there is a inclination to use Monte Carlo codifications for radiation dosimetry.

There are two chief phases involved in utilizing Monte Carlo simulation in radiation therapy interventions. These are simulation of the additive gas pedal caput, and simulation of the patient. The modeling of the additive gas pedal caput varies because each machine has different detailed devices, and the negatron beam characteristics may change every bit good. Consequently, these fluctuations could play an of import function in the concluding beam word picture and dose distribution. The National Research Council of Canada has developed a codification which is an EGS4 user codification ( Rogers et al. , 1995, ( Lin, Chu et Al.

2001 ) and ( Mesbahi 2007 )

2. 1. 5. Restriction of DOSXYZ codification

The DOSXYZ codification does non back up advanced multiple-source theoretical accounts to be used as a beginning input for negatrons and photons. Besides, the figure of beam qualifiers in patient simulation excludes, for illustration, cuneus, compensator and jaws. There is no assortment for taking the geometry coordinates from two definitions as in the MCDOSE codification.

Furthermore, the DOSXYZ codification can non do dose volume histograms. Monte Carlo inverse be aftering can non be achieved by the DOSXYZ codification, either for photon or negatron beams ( Li and et Al. 2000 ) .

2. 1.

6. Types of the Monte Carlo codification

One of the chief codifications based on EGS4 Monte Carlo simulation is DOSXYZ. Besides, it is considered to be a really utile method for the computation of dose distribution in apparition rectilineal voxels. However, the chief disadvantage of the DOSXYZ codification is that the simulations are non fast plenty on current Personal computers ‘ hardware ; hence, it takes a long clip for a simulation to be completed. Even so, there are many codifications that have been introduced and are available to heighten the DOSXYZ codification velocity, for case Voxel Monte Carlo ( VMC and XVMC ) and Super Monte Carlo ( SMC ) , although more careful verification and development might be required for radiation intervention dosimetry. The chief characteristics of the DOSXYZ codification are the capableness to imitate the transportation of both the negatron and photon beams in a three dimensional apparition. The volume of the apparition is counted in voxel units, which is rectilineal, and the form of the apparition can change in three dimension.

Besides, the stuff of the apparition can be determined by the user, and the beginning theoretical account is supported in DOSXYZ codification simulation. Several researches have involved utilizing the Monte Carlo codification for analyzing the influence of the linac caput constituents on the beam characteristics. Monte Carlo simulation has proved to be a dependable method in radiation intervention dosimetry. ( Li and et Al.

2000 )

2. 1. 7. Compilation and running DOSXYZnrc

The DOSXYZnrc files are chiefly located in the directory $ HEN HOUSE/user codes/dosxyznrc. It is possible to roll up and run DOSXYZnrc codification from graphical user interface ( GUI ) by choosing Compile from the Run bill of fare, but before running the codification, it has to lade make an input file.

Besides, there is an option to transport out an single tally or parallel run by choosing tally or subjecting waiting line ( Walter and et Al. 2009 ) .

2. 1. 8.

DOSXYZnrc Input Parameters

2. 1. 8. 1. Descriptions in DOSXYZnrc Source Code

2. 1.

8. 1. 1.

Point Source Rectangular Beam Incident from Front

The radiation point beginning is located on the Z-axis. The incident of the beam is assumed to be from the front side of the apparition. However, it is allowed to put the distance between the beginning and the apparition and it can be either symmetric or asymmetric.

In Monte Carlo codification simulation, the media between the beginning and the apparition is assumed to be a vacuity for the beginning. Fig 2 illustrates the simulation of incident for the point beginning beam on the apparition ( Walter and et Al. 2009 ) .

. Figure ( 2 ) Point beginning incident from the forepart ( isource= 3 ) . The isotropically-radiating point beginning is located on the Z-axis at distance ssd above the apparition. The beginning is collimated to a rectangular field ( Walter and et Al. 2009 ) ..

2. 1. 9. Other Input Variables

This subdivision provides descriptions of chief DOSXYZnrc input variables non covered above.

2. 1. 9. 1.

IPHANT

The DOSXYZnrc creates phantom informations to an egsphant file if the IPHANT is set to one. After taking a CT apparition, this option is unavailable because the option is an input file from ctcreate ( Walter and et Al. 2009 ) ..

2. 1. 9. 2. MAX20

To end product a summery on the screen of a maximal 20 doses in the apparition so MAX20 has to be set to one.

This option is utile for timing/efficiency surveies ( Walter and et Al. 2009 ) ..

2. 1. 9.

3. NCASE

This option shows the value of the histories for running a simulation where the minimal figure for simulation is 100, which is the default ( Walter and et Al. 2009 ) ..

2.

1. 9. 4. IWATCH

This option controls consequences to the show during execution of the beam. The input can be from zero to four ( Walter and et Al.

2009 ) ..

2. 1.

9. 5. TIMMAX

This choice is to put the maximal simulation clip allowed to run in hours by CPU clip ( Walter and et Al. 2009 ) .

.

2. 1. 9. 6. INSEED1, INSEED2

These Fieldss refer to random value seeds utilised to calculate the random figure Godhead ( Walter and et Al. 2009 ) .

.

2. 1. 9. 7. ESAVE GLOBAL

This option is the highest megavolts energy to be run.

This is utile when it is possible to make bremsstrahlung from high energy negatrons as it can forestall surcease of such high energy ( Walter and et Al. 2009 ) ..

2. 1.

9. 8. n split

This is used to pull off the photon splitting option.

2. 1.

9. 9. ihowfarless

HOWFAR is the geometric coding portion of EGS4 ( Nelson et al. , 1985 ) from a Monte Carlo simulation of a clinical additive gas pedal. It is recommended to utilize HOWFARLESS in all not heterogonous apparition computations.

To utilize the HOWFARLESS algorithm for conveyance in the apparition, it is necessary to put ihowfarless to one. The benefit of utilizing the algorithm is to better the efficiency of dose computations. However, this efficiency is influenced by many factors, such as energy apparition voxel size and the beginning type. For case, the effectivity could make 30 % when utilizing photon beams ( Walter and et Al. 2009 ) .

.

2. 1.

9. 10. ECUTIN

This is utilized beside the planetary ECUT input to find the planetary negatron cut-off energy in MeV. Puting of ECUT varies depending on the type of computation needed.

In the instance of radiation therapy, for intervention beams due to low energy negatrons utilizing a little dosage in the apparition, the ECUT can be really high. For most work considered, it uses ECUT= 0. 700 MeV, but a lower figure can be used when the dosage of the proctor chamber is important in computation ( Walter and et Al. 2009 ) .

2. 1. 9. 11. PCUTIN

Similar to ECUTIN, this is utilized beside the Global PCUT to stipulate the planetary photon cutoff energy in MeV. It is the photon peer of ECUTIN.

Nevertheless, it may pretermit the exact figure of the planetary PCUT because such low sums do non take long. It is recommended to utilize the value 0. 01MEv ( Walter and et Al. 2009 ) .

2. 1. 9. 12.

Dose Standardization

This depends on the type of beginning that is being used. For any beginning ( such as point beginning from the forepart with rectangular collimation ) with a chiseled beam field size on the phantom surface side, dose standardization can be calculated by the incident particles fluence ( Ainflu ) by: Ainflu = ( NCASE + ncaseold a?’ nmissm ) / ( ( xinu a?’ xinl ) * ( yinu a?’ yinl ) )Where: NCASE: value of the current histories. ncaseold: value of the old histories. nmissm: the entire sum any lost atoms from the beginning, every bit good as in any old tallies.( xinu – xinl ) * ( yinu – yinl ) is the beam size. However, if the incident beam size is equal to zero, dose standardization is calculated by: NCASE+ncaseold-nmissm ( Walter and et Al. 2009 ) .

.

2. 1.

9. 13. Cross-Section Data – PEGS4

“ Cross-section informations for many commonly-used media are included in EGSnrc installing in the files 521icru. pegs4dat and 700icru. pegs4dat, both located in the $ HEN_HOUSE/pegs4/data directory. The file 521icru. pegs4dat consists of cross-section informations from a lower negatron energy, AE, of 0. 521 MeV to an upper negatron energy, UE, of 55 MeV, while 700icru.

pegs4dat contains informations from AE= 0. 700 MeV to UE= 55 MeV. In both files the lower photon energy, AP, is 0. 01 MeV and the upper photon energy, UP, is 55 MeV.

These informations are based on the denseness consequence corrections in ICRU Report 37 ” ( Walter and et Al. 2009 ) .

2. 1. 9. 14. Photon splitting

This algorithm technique was proposed by Kawrakow and Fippel and is found to heighten the efficiency of photon beam simulation by a factor of about 5, utilizing xVMC. Besides, a photon splitting algorithm has been utilised in DOSXYZnrc in 2002 and found to better the dose efficiency by around 20 % .

( Kawrakow and Walters 2006 )Efficiency CalculationsThe efficiency of a Monte Carlo simulation is defined as: E= 1/ ( S2 * T )Where: Second: the uncertainness on the measure of involvement. Thymine: the CPU clip required to accomplish this uncertainness.

Section Two

Methodology

All Monte Carlo simulations were carried out on a 2. 2 GHz Intel Core 2 Duo CPU supplied with 3. 00 GB RAM under Microsoft Windows 7 Ultimate 64-bit version. The hardware used was Fujitsu Siemens AMILO Si 2636 notebook produced by Fujitsu Siemens computing machine.

2. 2. 1. Validation of point beginning theoretical account:

As a portion of any scientific experiment, it is critical to formalize the process.

There is no exclusion in radiation therapy research. Therefore, one of the chief parts of this research is to formalize the process. The proof procedure was carried out by utilizing the Monte Carlo simulations and so comparing the deepness dosage profile for 20 * 20 cm2 filed with existent informations ( Table no. ) , which was obtained from Singleton infirmary Medical Physics and Clinical technology quality system.

Depth ( centimeter )

Equivalent square Field size at surface ( centimeter ) 20

Depth ( centimeter )

Equivalent square Field size at surface ( centimeter ) 20

1. 51001167. 2298. 61264. 1395. 31361. 2491.

51458. 2587. 91555. 5684. 21652. 8780. 71750. 3877.

11847. 9973. 71945.

61070. 42043. 4Table ( 1 ) Central Axis per centum deepness dosage ( % DD ) for unfastened ( Plain ) Fieldss at 100cm SSD 6MV TenIn brief, the computation for 6MV photons was carried out utilizing the DOSXYZnrc codification.

The beginning surface distance ( SSD ) was set at 100cm, and point beginning was used in this simulation. The Dosxyznrc graphical user interface 1. 1software was used to run this proof. After running the package, a new inputs file was started as follows: a. Choice of 512icru.

pegs. 4dat from Browse Hen_House PEGS4 day of the monthB. Naming of the files with rubrics such as “ proof ” c. Specifying the Apparition: A H2O media was used as a apparition, along with air media in this simulation. The phantom dimensions ( X, Y, Z, where Ten is the length, Y is the breadth and Z is the deepness ) are 30 * 30 *40 cm3 where for field size they are 20 * 20 cm2. I. Global negatron cutoff energy: 0.

521 MeVtwo. Global photon cutoff energy: 0. 001 MeVthree. Print summery of highest 20 doses: nofour. Non CT informations inputv.

Define the apparition by: 1. specifying ten voxel separately. Number of X voxel 3. Then come ining the x voxel spacing in centimeter as follow: -20: -1: 1: 202. specifying y voxel as separately. Number of Y voxel 3. Then come ining the Y voxel spacing in centimeter as follow: -20: -1: 1: 203.

specifying Z voxel as separately. Number of Z voxel 4. Then come ining the minimal omega value ( = nothing ) and come ining the breadth of each group spacing in centimeter as follows tabular array ( 2 ) :

Z breadth

Number in group

120.

511289. 51six. Define medium: 1. choice of media figure: 12. taking medium type: H2O521ICRU3.

Set media of voxels table ( 3 ) :

From ten

To x

From Y

To y

From omega

To z

Density

1201201201. 0seven. End product: Choose the voxel for which to this list the dosage tabular array ( 4 ) :

From ten

To x

From Y

To y

From omega

To z

Scan

2222120Y scan per paged. Source parametric quantity: I.

Incident atoms: photontwo. Source type: point beginning from the forepart with rectangular collimation: 1. Lower ten edge: -10 centimeter2. Upper x edge: 10 centimeter3. Lower Y edge: -10 centimeter4.

Upper Y edge: 10 centimeter5. Beginning to come up distance SSD: 100 centimeter6. Then taking spectrum file name: mohan6.

spectrume. Simulation parametric quantity: I. Number of histories: It was changed until 2 % uncertainness was obtained in the consequences file in the omega bound figure 10. To acquire 2 % uncertainness, the % in the omega bound figure 10 was divided by 2 % before multiplying the consequences with the current histories. Repeated if necessary to acquire 2 % uncertainness.

two. IWATCH end product: nonethree. Maxim CPU clip ( hr ) : 0. 99four. RNG seed1: 33v. RNG seed2: 97six. Incident beam size: 100.

0seven. Run option: first clipeight. Howfarless: offnine. Output restart informations: after every spot: ten. Range rejection: offeleven.

Photon dividing figure: 1twelve. Run occupation analogue: no2- Runing the simulation after salvaging the input parametric quantity. 3- After completing the tally: Open the file named proof with MS excel and expression at the consequences in the omega bound figure4- After that Normalisation was done. 5- Then the deepness value was plotted against the tantamount square field size at the surface6- Plot the informations obtained from Singleton Hospital in the same graph to see the proof.

2. 2. 2.

Construction of the apparition

After finishing the proof procedure, the undertaking began to build the apparition. It was foremost made utilizing a manual drawing of a apparition, including spliting the apparition and the media by voxels unit in x, Y and axis ( attached in the appendices ) . It so used in Dosxyznrc graphical user interface 1.

1software for the building. The computation of 6MV photons was performed utilizing DOSXYZnrc codification. The beginning surface distance ( SSD ) was set at 95cm. The point beginning on the z-axis was used to execute the simulation of the original beam. The inside informations of the building were carried out after get downing with making new input files, as follows: a. Choice of 512icru. pegs.

4dat from Browse Hen_House PEGS4 day of the monthB. Naming of the file titles “ building ” c. Specifying the Apparition: A H2O media was used as a phamtom, every bit good as air media, in this simulation. The phantom dimensions ( X, Y, Z, where Ten is the length, Y is the breadth and Z is the deepness ) are 40 * 40 * 17. 5 cm3 where for field size they are 30 * 30 cm2. I. Global negatron cutoff energy: 0. 521 MeVtwo.

Global photon cutoff energy: 0. 001 MeVthree. Print summery of highest 20 doses: nofour. Non CT informations inputv. Define the apparition by: 1.

Specifying ten voxel as groups. Number of X voxel 3. Then come ining the lower limit ten value ( -15 ) and come ining the breadth of each group spacing in centimeter as follows tabular array ( 5 ) :

Ten breadth

Number in group

131141312. Specifying y voxel as groups. Number of Y voxel 3. Then come ining the lower limit Y value ( -15 ) and come ining the breadth of each group spacing in centimeter as follows tabular array ( 6 ) :

Y breadth

Number in group

111181113. Specifying Z voxel as groups. Number of Z voxel 4.

Then come ining the minimal omega value ( zero ) and come ining the breadth of each group spacing in centimeter as follows tabular array ( 7 ) :

Z breadth

Number in group

51210. 252101six. Define medium: 1. choice of media figure: 22. taking medium type: H2O521ICRU and AIR521ICRU3.

Set media of voxels table ( 8 ) :

From ten

To x

From Y

To y

From omega

To z

Medium

Density

1611014H2O521ICRU02511011AIR521ICRU0251123AIR521ICRU025101023AIR521ICRU0seven. End product: Choose the voxel for which to name the dosage tabular array ( 9 ) :

From ten

To x

From Y

To y

From omega

To z

Scan

252934z-scan per paged. Source parametric quantity: I. Incident atoms: photontwo. Source type: 3-point beginning from the forepart with rectangular collimation: 1. Lower ten edge: -9.

5 centimeter2. Upper x edge: 9. 5 centimeter3. Lower Y edge: -9. 5 centimeter4. Upper Y edge: 9. 5 centimeter5. Beginning to come up distance ssd: 95 centimeter6.

Then taking spectrum file name: mohan6. spectrume. Simulation parametric quantity: I. Number of histories: This was changed until 2 % uncertainness was obtained in the consequences. To acquire 2 % uncertainness, the % in the Y bound figure 10 was divided by 2 % so the consequences were multiplied with the current histories.

Repeat if necessary to acquire 2 % uncertainness. two. IWATCH end product: nonethree. Maxim CPU clip ( hr ) : 0. 99four. RNG seed1: 33v.

RNG seed2: 97six. Incident beam size: 100. 0seven. Run option: first clipeight.

Howfarless: offnine. Output restart informations: after every spot: ten. Range rejection: offeleven.

Photon dividing figure: 1twelve. Run occupation analogue: no7- Runing the simulation after salvaging the input parametric quantity. 8- After completing the tally, open the file named building with MS excel and expression at the consequences in the Y bound figure. 9- Plot the consequences to acquire the dose distribution.

Figure ( 3 ) shows a simple schematic of the DOSXYZnrc apparition geometry

Section three

Consequences and treatment

Depth ( centimeter )

Measured informations by Med. Phys

M C simulation of

Percentage deepness dosage

Depth ( centimeter )

Measured informations by Med. Phys

M C simulation of

Percentage deepness dosage

1. 5100. 00 %100. 00 %1167. 20 %69.

14 %2. 2599 %106. 35 %1264. 10 %65.

98 %395. 30 %99. 46 %1361.

20 %62. 94 %491. 50 %93. 44 %1458. 20 %57. 79 %587. 90 %94. 09 %1555. 50 %58. 76 %684. 20 %84. 69 %1652. 80 %54. 10 %780. 70 %83. 80 %1750. 30 %52. 35 %877. 10 %79. 09 %1847. 90 %48. 56 %973. 70 %75. 63 %1945. 60 %47. 82 %1070. 40 %73. 16 %Table ( 10 ) Comparison of per centum deepness dosage of MC simulation with measured informations by Singleton Hospital medical natural philosophies for Central Axis per centum deepness dosage ( % DD ) for unfastened ( Plain ) Fieldss at 100cm SSD 6MV TenFigure ( 10 ) Comparison of per centum deepness dosage of MC simulation with measured informations by Singleton infirmary medical natural philosophies for Central Axis per centum deepness dosage ( % DD ) for unfastened ( Plain ) Fieldss at 100cm SSD 6MV TenThese consequences could propose that, rating of measured and calculated information shows acceptable understanding. Besides, Monte Carlo simulation has been reported as a gilded criterion for radiation dosimetry. These consequences agreed with old surveies that considered a MC as one of the most accurate tool for radiation measurings ( Li and et Al. 2000 ) . Figure ( 11 ) Dose distribution calculated by Monte Carlo. The consequences of dose distribution the relationship between measured and calculated informations. The MC shows acceptable consequences compared with measured informations because the divergences were in the needed per centum.

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