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(بسم الله الرحمن الرحيم). ( قالوا سبحانك لا علم لنا إلا ما علمتنا انك أنت العليم الحكيم ) . صدق الله العظيم . سورة البقرة أية ( 32 ). Evaluation of Three-dimensional Dose Distribution in Radiotherapy Treatment Planning. - PowerPoint PPT Presentation

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Evaluation of Three-dimensional Dose Distribution in Radiotherapy Treatment Planning

( )( ) ( 32 )Evaluation of Three-dimensional Dose Distribution in Radiotherapy Treatment Planning

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-areeqiAdvisors Committee:Prof. Dr. Fatima I .NasrProfessor of Medical BiophysicsMedical Biophysics Department Medical Research InstituteAlexandria UniversityProf. Dr. Sohir Mahmoud El-KholyProfessor of Medical BiophysicsMedical Biophysics Department Medical Research InstituteAlexandria UniversityProf. Dr. Mohamed Farid Noaman Professor of Medical Physics and Radiation ProtectionRadiology Department Faculty of MedicineAlexandria UniversityDr. Azza Mahmoud. M. HelalLecturer of Medical PhysicsFaculty of MedicineRadiology DepartmentAlexandria UniversityKhaled Saeed al-areeqiExaminers committeeProf. Dr. Mohamed Farid Noaman (Head of examiners committee)Professor of Medical Physics and Radiation Protection Radiology DepartmentFaculty of MedicineAlexandria UniversityProf. Dr. Samia Abd Algauad Pofessor of Medical Physics and Radiation Protection Radiology DepartmentFaculty of MedicineAlexandria UniversityProf. Dr. Sohir Mahmoud El-Kholy Professor of Medical Biophysics Head of Medical Biophysics Department Medical Research InstituteAlexandria University Prof. Dr. Ehab Ebrahim AbdoProfessor of Medical BiophysicsDepartment of Medical BiophysicsMedical Research Institute Alexandria UniversityKhaled Saeed al-areeqiWill Be Present The Following:Introduction: Aim of the WorkMaterials:Methods:Results Conclusion andRecommendations

Khaled Saeed al-areeqiIntroductionRadiotherapy 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-areeqi3DCRT: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. ,Khaled Saeed al-areeqi3DCRT 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 .

Khaled Saeed al-areeqiAim 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. Khaled Saeed al-areeqiMaterialsPatients:

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 radiotherapyAsymmetric jaws and motorized wedge is also present.

Treatment planning systemLinear AcceleratorKhaled Saeed al-areeqiMethods3D 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.

Khaled Saeed al-areeqi3D Treatment PlanningSelection 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.

Khaled Saeed al-areeqiResults

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 andOAR sparing in all radiation techniques.Khaled Saeed al-areeqi Head Tumors Central Brain TumorTwo 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 (15, 30) 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.

Khaled Saeed al-areeqi

Khaled Saeed al-areeqiTechnique A Technique B Central Brain Tumor In Technique A : The CTV is covered by 95% of the prescribed dose but The dose is not conformal to tumor and The right and left optic nerves received higher maximum dose.

In Technique B : The CTV is covered and The dose is more conformal to tumor compared to technique A. The brain received higher maximum dose compared with technique A. The dose received by eyes and lenses was similar low dose in both techniques.

So Technique B is the best16

Khaled Saeed al-areeqiCentral Brain TumorTable show comparison of DVP for GTV, CTV and OAR in techniques A and B.

DVH show the technique A is better than technique B in PTV coverage by 95% of the prescribed dose with acceptable doses to OAR in technique B.17Chest 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 (60 and 45) 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 (30, 30) 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 (30) was used in Lt post oblique beam.

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

Khaled Saeed al-areeqi18

Khaled Saeed al-areeqiLeft Lung Cancer

Technique ATechnique BTechnique CIn Technique A : The PTV is covered by 95% of the prescribed dose The dose is more conformal to the tumor and The surrounding tissues received low dose

In Technique B : The PTV is covered and The dose is not conformal to the tumor and Right lung received higher maximum dose

In Technique C : The PTV coverage is better compared to techniques A and B. The dose is not conformal to tumor and Heart and spinal cord received higher maximum dose compared to techniques A and B.

So Technique A is the best19

Khaled Saeed al-areeqiLeft Lung Cancer

Table show comparison of DVP for GTV, PTV and OAR in techniques A, B and C.

DVH show the PTV coverage by 95% of the prescribed dose is better in technique C compared to techniques A and B and show acceptable doses to OAR in technique A.

20Abdomen 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 (15, 20) 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 (45, 25) were used in Ant and Lat beams respectively.

The energy was 6MV.

In Technique CThe same beam parameters were used as in technique B with change in gantry angle in Ant beam from zero to (15)

Khaled Saeed al-areeqi

Khaled Saeed al-areeqiHCCTechnique ATechnique BTechnique CIn Technique A : The PTV is covered by 95% of the prescribed dose The dose is more conformal to the tumor but Liver, Left kidney and spinal cord received higher maximum dose

In Technique B : The PTV is covered . The dose is conformal to the tumor and Liver received higher maximum dose

In Technique C : The PTV coverage is similar in all techniques. The dose is not conformal to the tumor and Right kidney received higher maximum dose compared to techniques A and B.

So Technique A is the best22

Khaled Saeed al-areeqiHCCTable show comparison of DVP for GTV, PTV and OAR in techniques A, B and C.

DVH show PTV coverage of the prescribed dose is similar in all techniques with acceptable doses to OAR in technique A.

23Pelvis Tumors Prostate CancerFour 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

Khaled Saeed al-areeqiProstate CancerTechnique ATechnique BTechnique CTechnique DIn Technique A : The PTV is covered by 95% of the prescribed dose but Rectum received higher maximum doseIn Technique B : The PTV is covered but Femoral heads received higher maximum doseIn Technique C : The PTV is covered and The surrounding tissues received low doseIn Technique D : The PTV is covered. The dose is more conformal to tumor and The surrounding tissues received low dose compared with others techniques.

So Technique D is the best25

Khaled Saeed al-areeqiProstate CancerTable show comparison of DVP for PTV and OAR in techniques A, B, C and D.

DVH show PTV coverage by 95% of the prescribed dose is better in technique A compared to other techniques and show acceptable doses to OAR in technique D.

26Pelvis Tumors Cancer CervixThree 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 (20) 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.

Khaled Saeed al-areeqi

Khaled Saeed al-areeqiCancer CervixTechnique ATechnique BTechnique CIn Technique A : The dose is more conformal to the tumor and The head of femurs received higher maximum dose and the dose received by rectum is high In Technique B : PTV coverage is better in technique A compared to technique B. The dose is more conformal and the surrounding tissues received low dose in technique A compared with technique B The head of femurs received higher maximum dose in technique A compared to technique B and the dose received by rectum is highIn Technique C : PTV coverage is similar in techniques B and C compared to technique A. The dose is more conformal in technique A compared with techniques B and C. The head of femurs received higher maximum dose in technique A compared to techniques B and C. and The dose received by rectum is high in all techniques.

So Technique C is the best28

Khaled Saeed al-areeqiCancer CervixTable show comparison of DVP for GTV, PTV and OAR in techniques A, B and C.

DVH show PTV coverage by 95% of the prescribed dose is similar in techniques B and C compared to technique A with acceptable doses to OAR in technique C.

29Conclusion3DCRT 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.

Khaled Saeed al-areeqiRecommendationsIn 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( 60) 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 (55, 55) 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 (60, 55) 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 (20) wedge in two lateral beams and 6MV energy in all beams.

Khaled Saeed al-areeqiFinally:

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 Khaled Saeed al-areeqi

Thank youYemen in my Heart Khaled Saeed al-areeqiSeber Mountain Cairo CastleTaiz Citymy web site: Medical Physics in Radiotherapy and Nuclear Medicine www.khaled-radiotherapy-physicist.webs.com

AmrMohamed