(بسم الله الرحمن الرحيم)

)بسم الله الرحمن الرحيم(

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العظيم أية ) البقرة (32سورة

Evaluation of Three-dimensional Dose Distribution in Radiotherapy Treatment Planning

التخطيط في العالجية األشعة ُجرعات توزيع تقييمباإلشعاع للعالج األبعاد ثالثي

Thesis

Submitted to the Medical Research Institute

In partial fulfillment of the requirements for the

Master Degree of Medical Biophysics (Medical Radiation Physics)

By

Khaled Saeed Sallam Saeed

Radiation Therapy Technologist National Oncology Center Radiotherapy Department

Ministry of Health Sana'a –Yemen

Khaled Saeed al-areeqi

Advisors Committee:Prof. Dr. Fatima I .NasrProfessor of Medical Biophysics

Medical Biophysics Department

Medical Research Institute

Alexandria University

Prof. Dr. Sohir Mahmoud El-KholyProfessor of Medical Biophysics

Medical Biophysics Department



Prof. Dr. Mohamed Farid Noaman Professor of Medical Physics and Radiation Protection

Radiology Department

Faculty of Medicine


Dr. Azza Mahmoud. M. HelalLecturer of Medical Physics

Faculty of Medicine


Alexandria University Khaled Saeed al-areeqi

Examiners committeeProf. Dr. Mohamed Farid Noaman (Head of examiners committee)Professor of Medical Physics and Radiation Protection


Faculty of Medicine


Prof. Dr. Samia Abd Algauad Pofessor of Medical Physics and Radiation Protection


Faculty of Medicine


Prof. Dr. Sohir Mahmoud El-Kholy Professor of Medical Biophysics

Head of Medical Biophysics Department



Prof. Dr. Ehab Ebrahim AbdoProfessor of Medical Biophysics

Department of Medical Biophysics


Alexandria University Khaled Saeed al-areeqi

Will Be Present The Following: Introduction: Aim of the WorkMaterials:Methods:Results Conclusion andRecommendations


Introduction Radiotherapy is the treatment of patients with malignant and benign

diseases using ionizing radiation. It aims to:

Deliver a homogeneous dose of radiation to a tumor, while delivering a dose as low as possible to healthy surrounding tissues.

Radiotherapy could be either:

Internal ( brachytherapy) or External to the patient.

External beam radiotherapy is the most common form used. It is delivered to the patient by: Conventional or Advanced techniques.

Conventional two-dimensional (2D) technique Using small number of rectangular beams achieves a good dose

coverage to the tumor, but normal tissues close to tumor could be irradiated to more

than tissues tolerance

Three-dimensional Conformal Radiotherapy ( 3DCRT ): Which delivers a homogeneous dose of radiation to tumor volume, while delivers an acceptable low dose to surrounding normal

tissues. Khaled Saeed al-areeqi

3DCRT:

3DCRT used direction of multiple beams conformed to the shape of the target from each BEV.

Conformal shielding is provided by MLC , Which move across the beam to conform the radiation dose

exactly to target volume and to protect the normal tissues from radiation.

The treatment planning uses BEV, Which is able to view the patient in the same orientation as a

radiation beam pointed in that direction to provide adequate dosimetric coverage of the planning target volume (PTV) and optimal sparing of normal tissues.

Conformal treatment plans generally use number of radiation beams to shape to

conform dose to the target volume. 3DCRT is rapidly giving way to an inverse planning approach which

is referred to as (IMRT). IMRT is an advanced form of 3DCRT,

Which allows more precise treating of the tumor. The radiation dose is designed to conform to the volumes with

complex concave shapes by modulating the intensity of the radiation beam to focus a higher radiation dose to the tumor,

while minimizing radiation exposure to surrounding normal tissues.

,


3DCRT Treatment Planning Procedures

These include:

Establishing the patients treatment position. Delineation of the target volumes and critical normal organs. Determining the beams orientations and MLC leaf shaping.

Compute of the 3D dose distribution according to the dose prescription.

Evaluate the treatment plans and if needed modify the plan.

The approved plan must then be implemented on the treatment machine.

Treatment plan is verified and appropriate quality assurance (QA) procedures are used .


Aim of the work

To assess the optimization of dose distribution by determining the beam parameters necessary to achieve the best treatment plan for patients with different malignant tumors.


MaterialsPatients:

fifty patients with different malignant tumors selected from different organs in head, chest, abdomen and pelvis.

Study in Clinical Oncology and Nuclear Medicine Department, Faculty of Medicine, Alexandria University, Egypt.

Machines:

A - Computed Tomography )CT(: CT imaging (Siemens somatom 6

emotions, Germany).

B - Treatment planning system )TPS(: Electa precise treatment system, Crawly,

UK was used .

C - Medical linear accelerator: Electa precise treatment system, linear

accelerator was used .

It produces x-ray with different energies (4, 6 and 15 MV).

It contains MLC appropriate for conformal radiotherapy

Asymmetric jaws and motorized wedge is also present.

Treatment planning system

Linear Accelerator


Methods3D Conformal Treatment Planning Include:

Simulation :

Placing the patient on the CT simulator table in the same treatment position.

Patients were marked with a reference marker.

Patients were tattooed to help patient set-up on the treatment

machine.

A suitable immobilization device was used

Contouring :

The CT slices of selected patients were transferred to TPS.

Skin was contours to mid reference point and was defined with anterior and two lateral borders.

The radiation oncologist outlined the target volumes and OAR.

The next step was 3D treatment planning.


3D Treatment Planning Selection of beam directions in each technique was carried out.

PTV margin was added and the isocenter (SAD) was placed to center of the tumor.

The energy was selected for each beam.

Planning parameters were defined; they include: Beam directions (gantry, collimator and couch angle) Beam energy, Field size, Beam weight and Using the beam modifiers such as wedge and blocks .

The radiation beams were shaped to the PTV by MLC in all radiation techniques

Wedges angles and Bolus in some beams were used.

Multiple beams arrangements were carried out.

Prescription dose was assigned to the center of PTV.

The dose distribution was normalized to the isocenter.

The dose distributions were compared with ICRU criteria.

The results were evaluated. Khaled Saeed al-areeqi

Plan evaluation:

For each patient different 3DCRT techniques were carried out and compared.

Evaluations of these techniques were based on three modalities;

Visual inspection of isodose lines:

DVH

DVH parameters :

The dose coverage of the PTV should be kept as possible within +7% and -5% of the prescribed dose.


Results

3DCRT Techniques:

This study includes fifty patients with different malignant

tumors.

In each patient different techniques were carried out.

In this presentation will be show :

One case in head tumors, one case in chest tumors, one case in abdomen and two cases in pelvis tumors.

Study evaluation included :

PTV coverage by 95% of prescribed dose, The conformity of the dose to the tumor and OAR sparing in all radiation techniques.


Head Tumors Central Brain Tumor

Two radiation techniques A and B were carried out. The dose prescribed was 50 Gy.

In Technique A

Two beams were used (Rt Lat and Lt Lat).

Wedges (15º, 30º) were used.

The beam energy was 6MV in all beams

In Technique B

Non –coplanar beam (vertex beam) were added to Rt Lat, Lt Lat beams

The same wedges angle were used as in technique A

With decrease in energy from 6MV to 4MV in all beams.



Technique A Technique B

Central Brain Tumor


Central Brain Tumor

Chest Tumors Left Lung Cancer

Three radiation techniques A, B and C were carried out. The dose prescribed was 44 Gy.

In Technique A Five beams were used. Ant, Lt Lat, Lt ant oblique, direct post and

Lt post oblique beams

Wedges (60º and 45º) were used in Ant and Lt Lat beams.

The energy of all beams was 6MV photons.

In Technique B Number of beams were decrease to three beams(Two ant oblique

and Lt Post oblique)

Wedges angle (30º, 30º) were used in Rt Ant oblique and Lt post oblique beams.

The energy of all beams was 6MV photons.

In Technique C The beam directions were change to ( Ant, post and Lt post

oblique)

Wedge angle (30º) was used in Lt post oblique beam.

With increases in energy from 6MV to 15 MV in all beams.



Left Lung CancerTechnique A Technique B Technique C


Left Lung Cancer

Abdomen Tumors HCC Three radiation techniques A, B and C were carried out. The dose prescribed was 60 Gy.

In Technique A

Four beams were used. Lt post oblique, Lt ant oblique, Rt post oblique and Rt ant oblique beams

Wedges angles (15º, 20º) were used in Rt post oblique and Rt ant

oblique.

The beam energy was 6MV.

In Technique B The beams number were decrease to three beams, (direct Ant,

direct post and direct Lat )

Wedges (45º, 25º) were used in Ant and Lat beams respectively.

The energy was 6MV.

In Technique C The same beam parameters were used as in technique B with

change in gantry angle in Ant beam from zero to (15º)



HCCTechnique A Technique B Technique C


HCC

Pelvis Tumors Prostate Cancer Four radiation techniques A, B, C and D were carried out. The dose prescribed was 9 Gy.

In Technique A Three beams were used. Ant, Rt and Lt post oblique beams

without using wedge. The photon energy was 6MV.

In Technique B Beam number were increased to Five beams. Ant, Lt post

oblique, Rt post oblique, Rt ant oblique and Lt ant oblique beams without using wedge.

The same beam energy was used as in techniques A

In Technique C Three beams were used. Ant, Rt and Lt Lat beams without using

wedge. Photon energy was 6MV in all beams.

In Technique D Seven beams were used. Rt, Lt post oblique, Rt and Lt ant

oblique, Rt and left lat beams without using wedge. Photon energy was 6MV in all beams. Khaled Saeed al-areeqi


Prostate Cancer

Technique A Technique B Technique C Technique D


Prostate Cancer

Pelvis Tumors Cancer Cervix

Three radiation techniques A, B and C were used. The dose prescribed was 35 Gy.

In Technique A Seven beams were used. Ant, Lt ant oblique, Rt ant oblique, Rt

post oblique, Lt post oblique, Rt Lat and Lt Lat beams without using wedges.

The beam energy was 6MV.

In Technique B Three beams were used. Ant, Rt Lat and Lt Lat beams

Wedge angle (20º) was used in Rt and Lt Lat beams.

The beam energy was 6MV in all beams.

In Technique C The same beam directions were used as in technique B

With the change in beam energy from 6MV to 15MV in all beams.



Cancer Cervix

Technique A Technique B Technique C


Cancer Cervix

Conclusion 3DCRT plans were evaluated for 50 patients with different

malignant tumors. For each patient multiple techniques were carried out.

The treatment planning parameters affect the dose distribution outcome, so the correct selection improves the dose distribution.

Precise and correct selection of beam directions shows better

sparing of OAR. For smaller target volume, multiple radiation beams improve dose

distribution to PTV and reduced the dose to OAR.

On the other hand it is better to use few radiation beams for large target volume.

In some cases, different radiation directions could be used to avoid high exposure to the OAR. According to site of tumor, change beam energy could improve dose distribution. According to size of tumor and location of OAR, the change in the number of beams could improve dose distribution.

Non coplanar beams can improve the dose distribution for some brain lesions.

In designed techniques, acceptable coverage of dose distribution to

PTV with low dose to sensitive structures was achieved. On the other hand there were unacceptable dose distributions to PTV with high doses to OAR.

DVH is considered as a faster and excellent evaluator for all plans, so it is used to select optimum plan.

In some techniques, although the use of multiple radiation beams did not spare the OAR, it is used to improve the dose to PTV.


RecommendationsIn Head Tumors :

Better to use non- coplanar beams in some brain tumors to improve dose distribution to the PTV and reduce the dose to OAR.

In eye cancer better to use two anterior oblique beams to protect the other eye with use 4MV photon energy with 1 cm bolus to elevate the dose to tumor with( 60º) wedge in two beams.

In Chest Tumors : Five beams (Ant, Lt Lat, Lt ant oblique, direct post and Lt post oblique beams) in

Left lung cancer with use equal beam weighting and 6MV energy in all beams improve the dose distribution to PTV and OAR received acceptable dose.

In Abdomen Tumors : In HCC four beams (Lt post oblique, Lt ant oblique, Rt post oblique and Rt ant

oblique beams) is better to use with equal beam weighting and 6MV energy in all beams.

Pancreas cancer and stomach cancer better to use more than two beams to improve the dose distribution to the PTV and reduce the dose to surrounding tissues

In Pelvis Tumors : Multiple radiation beams in prostate cancer is better to use to conform the dose

to the tumor and reduce the dose to OAR with use 6MV energy without using wedge in all beams.

In bladder cancer better to use three beams (Ant, Rt ant oblique and Lt ant oblique beams ) with using wedge (55º, 55º) in two ant oblique beams with use 15MV energy in all beams to reduce the hot spot and improve the dose distribution to the PTV. So the same beam directions with 6MV photon energy and (60º, 55º) wedge in Rt ant oblique and Lt ant oblique beams also better to use in bladder cancer.

Multiple radiation beams in cancer cervix did not recommended because not spare the OAR , it is used to improve the dose to the PTV. So three beams (Ant, Rt Lat and Lt Lat beams ) is better to use with (20º) wedge in two lateral beams and 6MV energy in all beams.


Finally:

I express my deep thanks to

All my supervisors, and

Medical Physics Members, Faculty of Medicine

All friends,

All thanks to my family

Especially my wife

Who deserve more than a word of thanks


Thank you

Yemen in my Heart


Seber Mountain

Cairo Castle

Taiz City

my web site: Medical Physics in Radiotherapy and Nuclear

Medicine www.khaled-radiotherapy-

physicist.webs.com

Amr Mohamed

(بسم الله الرحمن الرحيم)

Documents

radiation dose

radiation beam

homogeneous dose of

ionizing radiation

normal tissues

good dose coverage

acceptable low dose

external beam radiotherapy