بسم الله الرحمن الرحيم

Simulation of Photon Beam Interaction with the ZUBAL

Head Phantom

Presented by: Mostafa Hossni El-Soubki

Plan-UNC-Image plotter

Outline

1. Preparing the phantom and Converting to MCNP using the MATLAB software

2. Commissioning the geometry

3. Dealing with MATLAB GI to view the output data.

4. Transfer the phantom to plan-UNC, and compare the same plan with MCNP

5. Conclusion

6. References.

Preparing the Phantom

• Maximum number of cells allowed is 99999• (#cells x-axis * #cells y-axis* #cells z-axis)<99999

Preparing the Phantom

• The voxels outside the head have been excluded

Fig-4 (By image-j)

Preparing the Phantom

• The slice matrix has to be resized

Slice 23 after resizing from 59*40 to 50*37

Preparing the Phantom

• Material indexing has to be adjusted for MCNP.

Fig-5

Preparing the PhantomMaterial # Organ Material # Organ

1 outside phantom 86 medulla oblongata2 skin 23 fat3 brain 24 blood pool4 spinal cord 27 bone marrow5 skull 92 pons6 spine 30 trachea

71 dens of axis 31 cartilage72 jaw bone 100 uncus (ear bones)10 skeletal muscle 105 sinuses/mouth cavity75 lachrymal glands 107 optic nerve76 spinal canal 114 cerebral falx77 hard palate 120 eye78 cerebellum 122 lens79 tongue 123 cerebral aqueduct16 pharynx 126 teeth17 esophagus    

Preparing the Phantom• Converting all slices to MCNP

Converting From material excel sheets to MCNP.

Validating the Geometry

Applied Beam:

• SSD =100cm

• Field size = 5x5 cm2.

• Photon Beam energy = 6 MV

Validation in a Water Phantom

Fig-11

Blue is air.

Blue sky is water

Primary collimator

Ion chambers

Light mirror

X-y jaws

Light field reticle (MYLER)

Voxel volume = 0.5*0.5*0.5 cm3

Phantom volume= 30* 30 * 30 cm3

Percent Depth Dose Comparison

Fig-21

PDD% for 6mv LINAK 5x5 cm2 at 100cm SSD

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MCNP 5x5 cm2 6MV PDD%

ion chamber 6mv 5x5

Diference

dmax=1.5 cm

Percent Depth Dose Comparison

6mv PDD 5x5 cm2 100cm SSD

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Depth cm

PD

D% MCNP 6MV 5x5 PDD %

planUNC PDD

Differnce

dmax=1.5cm

Fig-24

PDD Comparison

beam energy 6MV   dmax=1.5 cm

field size cm2 depth cm PDD% ±ΔPDD

5*5 1.5 100 0.70

5*5 5 85 0.60

5*5 10 63.8 0.48

10*10 1.5 100 1.018

10*10 5 86.9 0.92

10*10 10 67.5 0.77

Beam Profile Comparison

6MV beam Profile for 5x5 cm2 at differnt depths

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off axis cm

pro

file Profile at dmax 1.5cm

profile at 5cm depth

profile at 10cm depth

Measured and Simulated Profile at 1.5cm Depth (Field Size 5x5 cm2)

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6MV measured profile% at dmax

MCNP 6MV profile at dmax depth

Difference %

Measured and Simulated Profile at 5 cm Depth (Field Size 5x5 cm2)

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6MV measured profile% at 5cm depth

MCNP 6MV profile 5 cm depth

Diifernce %

Measured and Simulated Profile at 10 cm Depth (Field Size 5x5 cm2)

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6MV measured profile% at 10cm depth

6MV MCNP profile% at 10 cm depth

Difference %

6 MV Beam Interaction with Head Phantom

Applied Beam:

• SSD =100 cm

• Field size =5x5 cm2

• Photon Beam energy = 6 Mev

Transverse Cross Section

Fig-25 slice-8 (MCNP- MATLAB GUI)

Coronal Cross Section

Transfer the Phantom to Plan-UNC

MCNP

Plan-UNC

converting to dicom

converting to excel sheets

Beam Setup of Head Phantom in Plan-UNC

SSD = 100 cm at slice number 8.Field size = 5 x 5 cm2.Photon Beam energy = 6 Mev

Central PDD

PDD% for 6mv LINAK 5x5 cm2 at 100cm SSD for slice-8

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MCNP slice-8 6MV 5x5 PDD %

plan-UNC slice8 PDD

Differnce

Inhomogeneous region

Fig-27Central PDD of slice-8

Fig-28 the inhomogeneous region in slice 8

Skull bones at 2cm depth

Isodose Lines

Plan-UNC-Image plotter

MCNPPlan-UNC

ISO-Dose levels: [ 0.98 0.95 0.9 0.7 0.5 ]

MCNP surface dose distribution

Fig-30

Conclusions

• Validation of geometry – Good agreement in PDD in decay region– Need better agreement in dose profiles in

penumbra region

• There is disagreement between MCNP and Plan UNC in the inhomogeneous regions (transition from bone to soft tissue

• Need for better quantitative methods to compare dose distribution in the phantom

References

• Visual Basic 6 MSDN library.

• Matlab7 Help.

• http://noodle.med.yale.edu/phantom/getdata.htm (ZUBAL phantom).

Thank you