A phantom based evaluation on the effects of patient breathing motion on Stereotactic Body Radiotherapy treatment volumes
| dc.contributor.advisor | Burger, Hester | |
| dc.contributor.advisor | Joubert Nanette | |
| dc.contributor.author | Coetzee, Nicolene | |
| dc.date.accessioned | 2020-09-09T09:12:51Z | |
| dc.date.available | 2020-09-09T09:12:51Z | |
| dc.date.issued | 2020 | |
| dc.date.updated | 2020-09-09T06:34:30Z | |
| dc.description.abstract | Aim: The aim of the study was to design an upper body phantom to mimic the movement of the lesion inside the lungs during a breathing cycle. Phantom design included an assessment of the motion observed for lung lesions, identification of suitable phantom materials as well as design of a motorized arm to mimic the movements observed inside the lung area of the phantom. Introduction: Expansion margins are added to clinical target volumes contoured by Oncologists in order to safeguard against under- or over-treatment of the target volume. They are designed to account for errors during setup, inaccuracies on the linear accelerator, and movement of targets inside the patient. If the margins are too small, there is a risk that the lesion/target may not receive the necessary dose, due to being partially missed. On the other hand, if the margins are too wide, the lesion will be covered, but normal tissue may receive unnecessary dose, resulting in additional side effects to the patient. Assessment of the impact of these margins is not possible in a static phantom and the availability of a low-cost motorized phantom would assist in the validation of these margins. Method: Previously treated patients' 4D CT scanning data were used to quantify the amount of movement seen for lesions within the lung. A phantom was then designed and built in an attempt to mimic both patient anatomy and movement. Materials were identified to replicate anatomical shape and densities of various organs in the thorax, as seen on CT scan data. Two treatment planning systems (Monaco, (Elekta) and Eclipse (Varian)) were used to determine the dosimetric characteristics of the materials. This was compared to actual dose as delivered by a linear accelerator (Elekta Synergy). Results: Paths were calculated from the breathing cycles during the 4D-CT scan sets and templates designed to mimic these movements. A thorax phantom was built with the appropriate materials suitable and matched densities to replicate a human thorax. Comparing transmission for these materials on a linear accelerator for 6MV and 10MV energy, the deviation from planned versus measured dose varied between 1.67% to 3.32% and 0.45% to 2.30%, respectively for the silicon material and between 0.77% to 3.22% and 0.17% to 2.57% for the 3D printed bone for 6MV and 10MV. iv Conclusion: The measurements done on the linear accelerator matched closely with the calculated values on the treatment planning system for transmission through the materials in the customised phantom. Various proposals were put forward to mimic the movement of the targets within the lung regions. However, it was not possible to manufacture a mechanically based working model due to the small movements observed (<5mm). It is recommended that a robotic solution be investigated as alternative to mimic these small movements. | |
| dc.identifier.apacitation | Coetzee, N. (2020). <i>A phantom based evaluation on the effects of patient breathing motion on Stereotactic Body Radiotherapy treatment volumes</i>. (). ,Faculty of Health Sciences ,Division of Radiology. Retrieved from http://hdl.handle.net/11427/32181 | en_ZA |
| dc.identifier.chicagocitation | Coetzee, Nicolene. <i>"A phantom based evaluation on the effects of patient breathing motion on Stereotactic Body Radiotherapy treatment volumes."</i> ., ,Faculty of Health Sciences ,Division of Radiology, 2020. http://hdl.handle.net/11427/32181 | en_ZA |
| dc.identifier.citation | Coetzee, N. 2020. A phantom based evaluation on the effects of patient breathing motion on Stereotactic Body Radiotherapy treatment volumes. . ,Faculty of Health Sciences ,Division of Radiology. http://hdl.handle.net/11427/32181 | en_ZA |
| dc.identifier.ris | TY - Master Thesis AU - Coetzee, Nicolene AB - Aim: The aim of the study was to design an upper body phantom to mimic the movement of the lesion inside the lungs during a breathing cycle. Phantom design included an assessment of the motion observed for lung lesions, identification of suitable phantom materials as well as design of a motorized arm to mimic the movements observed inside the lung area of the phantom. Introduction: Expansion margins are added to clinical target volumes contoured by Oncologists in order to safeguard against under- or over-treatment of the target volume. They are designed to account for errors during setup, inaccuracies on the linear accelerator, and movement of targets inside the patient. If the margins are too small, there is a risk that the lesion/target may not receive the necessary dose, due to being partially missed. On the other hand, if the margins are too wide, the lesion will be covered, but normal tissue may receive unnecessary dose, resulting in additional side effects to the patient. Assessment of the impact of these margins is not possible in a static phantom and the availability of a low-cost motorized phantom would assist in the validation of these margins. Method: Previously treated patients' 4D CT scanning data were used to quantify the amount of movement seen for lesions within the lung. A phantom was then designed and built in an attempt to mimic both patient anatomy and movement. Materials were identified to replicate anatomical shape and densities of various organs in the thorax, as seen on CT scan data. Two treatment planning systems (Monaco, (Elekta) and Eclipse (Varian)) were used to determine the dosimetric characteristics of the materials. This was compared to actual dose as delivered by a linear accelerator (Elekta Synergy). Results: Paths were calculated from the breathing cycles during the 4D-CT scan sets and templates designed to mimic these movements. A thorax phantom was built with the appropriate materials suitable and matched densities to replicate a human thorax. Comparing transmission for these materials on a linear accelerator for 6MV and 10MV energy, the deviation from planned versus measured dose varied between 1.67% to 3.32% and 0.45% to 2.30%, respectively for the silicon material and between 0.77% to 3.22% and 0.17% to 2.57% for the 3D printed bone for 6MV and 10MV. iv Conclusion: The measurements done on the linear accelerator matched closely with the calculated values on the treatment planning system for transmission through the materials in the customised phantom. Various proposals were put forward to mimic the movement of the targets within the lung regions. However, it was not possible to manufacture a mechanically based working model due to the small movements observed (<5mm). It is recommended that a robotic solution be investigated as alternative to mimic these small movements. DA - 2020_ DB - OpenUCT DP - University of Cape Town KW - Medicine LK - https://open.uct.ac.za PY - 2020 T1 - A phantom based evaluation on the effects of patient breathing motion on Stereotactic Body Radiotherapy treatment volumes TI - A phantom based evaluation on the effects of patient breathing motion on Stereotactic Body Radiotherapy treatment volumes UR - http://hdl.handle.net/11427/32181 ER - | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11427/32181 | |
| dc.identifier.vancouvercitation | Coetzee N. A phantom based evaluation on the effects of patient breathing motion on Stereotactic Body Radiotherapy treatment volumes. []. ,Faculty of Health Sciences ,Division of Radiology, 2020 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/32181 | en_ZA |
| dc.language.rfc3066 | eng | |
| dc.publisher.department | Division of Radiology | |
| dc.publisher.faculty | Faculty of Health Sciences | |
| dc.subject | Medicine | |
| dc.title | A phantom based evaluation on the effects of patient breathing motion on Stereotactic Body Radiotherapy treatment volumes | |
| dc.type | Master Thesis | |
| dc.type.qualificationlevel | Masters | |
| dc.type.qualificationlevel | MSc |