In radiotherapy the main goal is to kill cancer cells, prevent them from growing and reproducing, while healthy tissue is spared. One technique to treat cancer is to use external radiotherapy where a linear accelerator (linac) is used to generate a high energy radiation photon beam. An MRI-linac is a combined magnetic resonance imaging (MRI) and linac and is used to perform adaptive radiotherapy. However, in order to perform treatments on the MRI-linac commissioning measurements must be performed to acquire all radiation beam data, verify its accuracy, and enter all these data into a com- puterized treatment planning system (TPS). To acquire the radiation beam data absorbed dose, output factors, percentage depth dose (PDD) curves and cross- and inplane profiles are measured. This was done together with a gamma analysis by Elekta in connection with the installation of the Elekta Unity MRI-linac at the Uppsala University Hospital in the year 2019. In this project these commissioning measurements and gamma analysis have been recreated and compared with the expected dose distributions calculated in the TPS Monaco. In addition to this a comparison with the result from Elekta has been done. With a water phantom, PTW BEAMSCAN MR, and three different detectors, PTW Semiflex 3D, PTW microDiamond and Farmer chamber PTW30013, PDDs and profiles have been acquired at different field sizes at gantry angles 0° and 270°. The absorbed dose was measured under reference conditions, depth 10 cm and field size 10x10 cm2, to be 0.8656 cGy/MU and 1.1666 cGy/MU at gantry angle 0° and 270°, respectively. This yielded a difference between Elekta’s result of 0.02% and -0.24% for 0° and 270°, respectively. The output factors were measured at 0° and 270° and differed with Elekta’s result in a range from -2.45% to 0.04%. From these values the PDDs and profiles were created and compared with the calculated result from Monaco.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:umu-198839 |
| Date | January 2022 |
| Creators | Kvarnlöf, Olivia |
| Publisher | Umeå universitet, Institutionen för fysik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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