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Session: Multi-Disciplinary General ePoster Viewing [Return to Session]

Initial Clinical Experience with Surface Guidance for Treating Breast Patients On Halcyon

K Kisling*, L Padilla, G Kim, UC San Diego, La Jolla, CA


PO-GePV-M-217 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: Traditional setup approaches for breast radiotherapy cannot be used when treating with the Varian Halcyon linac, which has no light field, optical distance indicator, or portal imaging. Additionally, the couch has only three degrees-of-freedom, therefore patient rotations must be manually adjusted. To address these issues, we implemented a Surface-Guided Radiotherapy (SGRT) system to assist with patient setup. This system also has a specialized InBore camera for intra-fraction monitoring and deep-inspiration breathhold (DIBH) treatments. Our initial experience is described herein.

Methods: Our Halcyon treatment vault has an AlignRT SGRT system with two main modules: patient setup mode, which uses traditional ceiling-mounted cameras pointed at the Halcyon’s virtual isocenter (outside the treatment bore), and treatment mode, which uses an InBore camera that enables intra-fraction monitoring and DIBH treatments. We implemented a workflow to streamline setup and intra-fraction monitoring of breast patients treated with Halcyon.

Results: To date, we have treated 13 breast patients on Halcyon (6 with tangent fields, 7 with VMAT for partial breast irradiation) for a total of 112 fractions. We used SGRT to correct rotational errors prior to kV-CBCT which resulted in minimal need to repeat CBCT (<4% of fractions). Average and standard deviation of shifts from CBCT were 0.4±0.3cm vertical, 0.3±0.3cm lateral, and 0.3±0.2cm longitudinal. Average treatment time from start of CBCT to beam-off was 3.1±1.5minutes, which allows for 10-minute appointment slots for all breast treatments, including first fraction and DIBH. We recently treated our first patient using DIBH.

Conclusion: We have used SGRT to enable reliable setups and fast treatments for breast cancer using a Halcyon. SGRT minimized the need for repeat CBCTs compared to values reported from other clinics (45 vs. 10-20%), which reduces unnecessary dose to patients and allows for faster setup. Finally, we successfully used the InBore AlignRT system to enable DIBH treatments.

Funding Support, Disclosures, and Conflict of Interest: Kelly Kisling acknowledges Honoraria and speaker fees from Varian Medical Systems. Grace Kim acknowledges consultant work for Vision RT. Laura Padilla acknowledges speaker fees from VisionRT.


Breast, Surface Matching, Image Guidance


TH- RT Interfraction Motion Management: setup errors, immobilization, localization

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