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Radiation Therapy Image-guidance Interventions and Treatment Re-planning Activities

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Descriptive Study of Radiation Therapy Image-guidance Interventions
and Treatment Re-planning Activities

Michal Stankiewicz BSc1,2, Tara Rosewall PhD MRT(T)1,3, Michael Velec PhD MRT(T)3

1Dept. Radiation Oncology, University of Toronto, Toronto, Canada; 2The Michener Institute of Education at UHN, Toronto, Canada; 3Princess Margaret Cancer Centre, Toronto, Canada


•During radiation therapy treatment, anatomical changes seen on daily CBCT are noticed by Radiation Therapists.
•If these observed changes are thought to compromise the original plan, a query may be instigated in order to assess treatment integrity.
•These investigations may give cause for a re-plan, in order to adapt to the change in question.
•A clear understanding of the image-guidance interventions and re-planning activities at Princess Margaret Cancer Centre would be a preliminary step in initiating future discussion within the department.
•The purpose of this study was to perform a chart review of treatment plans in 2015 that were queried for a re-plan consideration and investigate why the decision to re-plan or not was made.


•Treated with CBCT-guided radiation therapy in 2015
•CBCT flagged for investigation
•All cancer sites & treatment intents


•Patients flagged due to patient care issues
•Patients re-planned due to QA rounds
•Patients re-planned due to a non-Image guidance related issue
•Capturing a preliminary list of patients required selectively filtering through the department’s electronic clinical systems

Fig 1. Graphical representation of the captured patients based on search method. Patients with queried plans but not
re-planned (blue
) are of great interest.

•Treatment unit e-mails regarding queried patients were captured using selective keywords (CBCT, images, imaging, cone beam, screenshot, screen capture).
•Treatment plans marked as ‘discontinued’ were captured in the department’s published plan database and further filtered to match inclusion/exclusion criteria.
•Patients that had more than 1 CT simulation were captured and further filtered to match inclusion/exclusion criteria.

Fig 2. Image-guidance investigations by disease site. Site-specific frequency of queries compared to the number of estimated treatment plans is shown in brackets. ‘Other’ includes sites with ≤ 1% of all queries.

Fig 3. Proportion of treatment plans investigated due to image-guidance intervention with respect to the time during treatment. Queries are grouped into either being re-planned or continued original treatment plan.

Fig 4. Reasons for treatments plans being queried grouped by disease site. ‘Other’ includes the lymphoma, sarcoma, central nervous system and endocrine disease sites.

Fig 5. Comparing the outcome of queried treatment plans based on treatment intent.


•Radiation Therapists queried CBCT results most frequently for H&N, lung and pelvis radical RT patients for different reasons although only a small number are re-planned.
•Reasons for querying CBCT, including the language used, is not standard across sites.
•The implementation of tools that enable rapid assessment of the dose impact of CBCT results on the treatment unit may allow Therapists to assess which patients need adaptive re-planning.

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