Feasibility of adaptive SBRT of prostate cancer: Investigating uncertainties in AI-driven and CBCT-guided online adaptive radiotherapy
(2020) MSFT01 20201Medical Physics Programme
- Abstract
- Purpose: Recent developments in external radiotherapy and its utilization with artificial in- telligence (AI) enables advanced treatment plans for a range of different disease sites. By adapting to the anatomy of the day, target coverage can be ensured while sparing more healthy tissue. The purpose of this project was to study the feasibility and benefits of daily cone beam computed tomography (CBCT)-based online adaptive radiotherapy (oART) for localised prostate cancer using the Varian Ethos™ treatment planning system (TPS). The possibility of increasing dose per fraction, while sparing organs at risk (OAR), was investi- gated.
Materials and method: Online adaptive stereotactic body radiotherapy (SBRT) (5 x 7.25 Gy/fr) was simulated... (More) - Purpose: Recent developments in external radiotherapy and its utilization with artificial in- telligence (AI) enables advanced treatment plans for a range of different disease sites. By adapting to the anatomy of the day, target coverage can be ensured while sparing more healthy tissue. The purpose of this project was to study the feasibility and benefits of daily cone beam computed tomography (CBCT)-based online adaptive radiotherapy (oART) for localised prostate cancer using the Varian Ethos™ treatment planning system (TPS). The possibility of increasing dose per fraction, while sparing organs at risk (OAR), was investi- gated.
Materials and method: Online adaptive stereotactic body radiotherapy (SBRT) (5 x 7.25 Gy/fr) was simulated in a pre-clinical release of the Ethos TPS for 10 prostate cancer pa- tients using retrospective data. The system used AI-generated influencers for structure- guided or elastic deformation of targets and OAR from the reference situation on the plan- ning computed tomography (CT) image to the online acquired CBCT images. For a lo- calised prostate cancer treatment, the influencers used were bladder, rectum, and prostate, as defined on CT, while the prostate target was defined on magnetic resonance (MR) images. Based on the propagated target, the system generated two plans: scheduled and adapted. The scheduled plan was re-calculated based on the anatomy of the day, whilst the adapted plan was both re-optimised. The influencer editing required to achieve accurate target prop- agation was evaluated. The absorbed dose to clinical target volume (CTV), planning target volume (PTV), and rectum for the scheduled and adapted plans was compared. A 5 mm isotropic CTV-PTV margin was used.
Results: The AI could propagate an MR-defined prostate target based on a CT-defined prostate influencer. However, of all propagated targets, 69.4% were larger in volume than the target on the planning CT (reference target). The propagated target position with re- spect to the reference target was satisfactory, where only 10% of all propagated targets were extending outside the reference PTV. The average absolute difference in position and its standard deviation were: 1.19 1.14 mm in the sagittal plane, 1.90 1.66 mm in frontal, and 1.06 1.26 mm in transversal planes. A statistically significant difference was seen between scheduled and adapted plans (n=49) in the absorbed dose to 99% of CTV volume (p=0.00) and to 99% of PTV volume (p=0.00). There was no significant difference in the maximum absorbed dose to the rectum (p=0.36) , in the rectum volume that received 28 Gy (p=0.67) and the rectum volume that received 32 Gy (p=0.10).
Conclusions: The Varian Ethos TPS was observed to deform an MR-defined prostate target when CT-defined prostate was used as influencer. The propagated target volume differed from the reference target, but its position was accurate. The system could be advantageous for daily online adapted SBRT prostate treatments with sufficient CTV and PTV coverage. The reduction of toxicity to rectum needs further investigation. (Less) - Popular Abstract (Swedish)
- Cancer kan drabba vem som helst och kan ha sitt ursprung i många olika områden i kroppen. Antalet nya cancerfall ökar varje år, men vissa typer av cancer har bättre prognos än andra.
Den vanligaste cancertypen i Sverige är prostatacancer och den drabbar framför allt äldre män. Prostatacancer har god prognos och det finns effektiva metoder att helt bota prostat- acancer om den behandlas i ett tidigt stadie. Ett sätt att behandla prostatacancer är genom strålbehandling, där prostatan bestrålas vid flera behandlingstillfällen genom en strålkanon. Vanligtvis behöver patienten få sin behandling under ca 39 tillfällen, vilka sträcker sig över en period av 8 veckor. Det är möjligt att förkorta behandlingen till enbart fem tillfällen genom att... (More) - Cancer kan drabba vem som helst och kan ha sitt ursprung i många olika områden i kroppen. Antalet nya cancerfall ökar varje år, men vissa typer av cancer har bättre prognos än andra.
Den vanligaste cancertypen i Sverige är prostatacancer och den drabbar framför allt äldre män. Prostatacancer har god prognos och det finns effektiva metoder att helt bota prostat- acancer om den behandlas i ett tidigt stadie. Ett sätt att behandla prostatacancer är genom strålbehandling, där prostatan bestrålas vid flera behandlingstillfällen genom en strålkanon. Vanligtvis behöver patienten få sin behandling under ca 39 tillfällen, vilka sträcker sig över en period av 8 veckor. Det är möjligt att förkorta behandlingen till enbart fem tillfällen genom att öka mängden strålning patienten får vid varje tillfälle.
Strålbehandling är en effektiv metod att behandla prostatacancer, men kan leda till biverkningar om man bestrålar de friska organen kring prostatan såsom ändtarmen och urinblåsan. En röntgenbild av patienten tas vid varje behandlingstillfälle för att kunna se hur prostatan lig- ger relativt strålkanonen och kunna rikta strålningen korrekt, varefter patientens position justeras för att överensstämma med positionen på datortomografibilderna som användes för planeringen av strålbehandlingen. Att ändra patientens position är dock inte alltid tillräckligt för att återskapa prostatans position som i planeringssituationen. Kroppen ändras hela tiden, och kan se olika ut vid de olika behandlingstillfällena. Den planerade behandlingen kan passa väl vissa dagar och betydligt sämre andra dagar. Så varför anpassas inte behandlingen till patienten istället för att anpassa patienten till behandlingen? Hittills har de tekniska förut- sättningarna inte funnits tillhands, men nyligen blev ny teknologi tillgänglig som möjliggör att en ny behandlingsplan skapas för patienten vid varje enskilt behandlingstillfälle inom en rimlig tidsram. Den här typen av behandling kallas för online adaptiv och används för att ge en behandling som passar patientens kropp just den dagen.
I detta projekt undersöktes om online adaptiv strålbehandling kan användas för att behandla prostatacancer med färre behandlingstillfällen än traditionellt genom ökad bestrålning vid varje tillfälle, utan att otillbörligen skada omkringliggande organ. Det utvärderades hur bra metoden är på att ge den ordinerade behandlingsdosen till prostatan, där cancern fanns, och hur mycket de omkringliggande friska organen påverkades.
Projektets resultat pekar mot att online adaptiv strålbehandling har fördelar när det kommer till mängden bestrålning prostatan får. Det kunde inte påvisas stora förändringar i bestrål- ningen av de friska organen, jämfört med en traditionell strålbehandling där planen inte anpassades vid varje behandlingstillfälle. Möjligheten att minska denna bestrålning kom- mer att undersökas vidare i framtida studier. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9034918
- author
- Emin, Sevgi LU
- supervisor
- organization
- course
- MSFT01 20201
- year
- 2020
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9034918
- date added to LUP
- 2021-01-17 13:02:49
- date last changed
- 2021-01-17 13:02:49
@misc{9034918,
abstract = {{Purpose: Recent developments in external radiotherapy and its utilization with artificial in- telligence (AI) enables advanced treatment plans for a range of different disease sites. By adapting to the anatomy of the day, target coverage can be ensured while sparing more healthy tissue. The purpose of this project was to study the feasibility and benefits of daily cone beam computed tomography (CBCT)-based online adaptive radiotherapy (oART) for localised prostate cancer using the Varian Ethos™ treatment planning system (TPS). The possibility of increasing dose per fraction, while sparing organs at risk (OAR), was investi- gated.
Materials and method: Online adaptive stereotactic body radiotherapy (SBRT) (5 x 7.25 Gy/fr) was simulated in a pre-clinical release of the Ethos TPS for 10 prostate cancer pa- tients using retrospective data. The system used AI-generated influencers for structure- guided or elastic deformation of targets and OAR from the reference situation on the plan- ning computed tomography (CT) image to the online acquired CBCT images. For a lo- calised prostate cancer treatment, the influencers used were bladder, rectum, and prostate, as defined on CT, while the prostate target was defined on magnetic resonance (MR) images. Based on the propagated target, the system generated two plans: scheduled and adapted. The scheduled plan was re-calculated based on the anatomy of the day, whilst the adapted plan was both re-optimised. The influencer editing required to achieve accurate target prop- agation was evaluated. The absorbed dose to clinical target volume (CTV), planning target volume (PTV), and rectum for the scheduled and adapted plans was compared. A 5 mm isotropic CTV-PTV margin was used.
Results: The AI could propagate an MR-defined prostate target based on a CT-defined prostate influencer. However, of all propagated targets, 69.4% were larger in volume than the target on the planning CT (reference target). The propagated target position with re- spect to the reference target was satisfactory, where only 10% of all propagated targets were extending outside the reference PTV. The average absolute difference in position and its standard deviation were: 1.19 1.14 mm in the sagittal plane, 1.90 1.66 mm in frontal, and 1.06 1.26 mm in transversal planes. A statistically significant difference was seen between scheduled and adapted plans (n=49) in the absorbed dose to 99% of CTV volume (p=0.00) and to 99% of PTV volume (p=0.00). There was no significant difference in the maximum absorbed dose to the rectum (p=0.36) , in the rectum volume that received 28 Gy (p=0.67) and the rectum volume that received 32 Gy (p=0.10).
Conclusions: The Varian Ethos TPS was observed to deform an MR-defined prostate target when CT-defined prostate was used as influencer. The propagated target volume differed from the reference target, but its position was accurate. The system could be advantageous for daily online adapted SBRT prostate treatments with sufficient CTV and PTV coverage. The reduction of toxicity to rectum needs further investigation.}},
author = {{Emin, Sevgi}},
language = {{eng}},
note = {{Student Paper}},
title = {{Feasibility of adaptive SBRT of prostate cancer: Investigating uncertainties in AI-driven and CBCT-guided online adaptive radiotherapy}},
year = {{2020}},
}