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Online Dose Monitoring in Proton Therapy using Positron Emission Tomography

Moshiri, Shirin | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57443 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Hosseini, Abolfazl
  7. Abstract:
  8. Proton therapy is an advanced method of cancer treatment that has the ability to provide better protons than other radiation therapy methods. Even though the charged particles have superior characteristics and their biological properties are more than the deviations in treatment design. In order to check the uncertainties in hadron therapy and reduce the side risks, there is a need for methods to monitor the range during radiation therapy. Considering that the charged particles are in the tissue, the monitoring method should be able to collect the secondary particles produced during the interaction of the primary beam with the tissue. Currently, positron emission tomography (PET) is the only practical method to record the flux of secondary particles produced during the interaction of the beam with the tissue in a non-invasive manner. PET imaging in online dose monitoring in proton therapy is a point scanning method using the Monte Carlo method. To achieve this goal, GATE simulator code based on Geant4 Monte Carlo software is used, whose capabilities have been studied in the field of imaging and proton therapy. To achieve the goal, first, a PET imaging system is simulated by GATE software, then proton irradiation is performed on a water phantom, and finally, with the expected results, proton irradiation is performed on a heterogeneous phantom. In this thesis, the geometry was validated as a Cylindrical PET with 4-HEAD modeling and some different powers including spatial resolution, real fraction, scattering fraction, random fraction and identification using springs with specific activities with NEMA standard. The value of FWHM for six point sources varies in the range of 3 to 5 mm and FWTM is reported to be around 5 to 7 mm. The amount of dispersion fraction for the maximum amount of real events in 100 Mbps activities is reported to be about 40%, and the evaluation rate of the system for the center point of the axial transect field of view is about 15 (cps/KBq) and for a distance of 10 cm. Its radius is about 6 (cps/KBq). After the validation, it reduces the geometry of the system to 2-HEAD, then the proton irradiation of a homogeneous water phantom in the energy range of 70 to 235 MegaelectronVolts is performed and the secondary particle flux produced by the PET imaging system with the results obtained from Proton production. In the context of comparison. The investigated lists are range, Bragg peak location and longitudinal profile. The range of secondary particles produced is estimated through a line that showed a maximum difference of about 5 mm with a range of 80% of the proton at low energies. The peak of the proton dose shown in the water phantom with a difference in the range of 0-3 mm in different energies has also been found through the element's fall location. Also, the accuracy in detecting the end of SOPB was 1.05% (corresponding to the range obtained from the nitrogen flux at the last selected energy). In the next step, PET was investigated and confirmed during proton therapy of a heterogeneous CT phantom of the head and neck region including the tumor (nasopharynx area) and using the PET system, registered models of secondary particles were registered and different names were valued and checked. Heavy weight including its projection was drawn and compared with proton dose analysis profiles, it was observed that by opening the energy window as much as possible, PET activity can be related to proton dose more accurately. By performing the above steps, a suitable tool for monitoring and online monitoring during proton therapy can be obtained, with the help of which the treatment can be evaluated and if necessary, the image can be corrected and revised
  9. Keywords:
  10. Monte Carlo Method ; Proton Therapy ; Cancer Treatment ; Positron Emission Tomography (PET) ; Online Dose Evaluation ; Spot Scan Proton Therapy ; Geant4 Application for Tomographic (GATE)Emission

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