Impact of Using SGRT on Treatment Accuracy Based on Transit in Vivo Dosimetry Results
1. Impact of using SGRT in treatment
accuracy based on transit in vivo
dosimetry results
C. Ansón, N. Garcia, S. Bermejo, N. Jornet, P. Carrasco
Presented by: N. Garcia
Hospital de la Santa Creu i Sant Pau
1 December 2022
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2. ‒ Surface-based image guided
radiotherapy (SGRT) is a useful tool
that allows:
▪ Patient positioning
▪ Intrafraction motion monitoring
Introduction
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3. – Report the impact of introducing SGRT for breast treatments based on the results
obtained with 2D transit in-vivo dosimetry (iVD).
Objectives
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4. Methods and Materials
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– A TrueBeam unit provided with the optical
SGRT system Align-RT (VisionRT).
– For treatments on this linac:
– Postural Video → Patient positioning
Special attention to the position of the arms and
the affected breast.
– Intrafraction motion beam controlled by the SGRT:
– Translational: 5 mm
– Angular directions using Align-RT region of
interest (breast): 3º
5. IGRT
Positioning
Gating
Transit iVD
Visual: CCTV Optical sensors: Beam control
Laser: tattoos Surface monitoring: postural video
36 patients in linac without SGRT 36 patients in linac with Align-RT
Methods and Materials
5mm
3º
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6. – 2D transit in-vivo dosimetry (iVD) field by field: Once a week
Methods and Materials
Gamma analysis comparing
expected vs delivered dose (Gy)
Local gamma criteria:
• 5%-7mm
• 5%-5mm
• 3%-3mm
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7. – 2D transit in-vivo dosimetry (iVD) gamma analysis:
Results
1601 images from 276 fractions
were evaluated
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11. Conclusions
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‒ Real-time monitoring of patient surface and beam control during the whole
treatment session accounts for higher in-vivo dosimetry gamma rates using SGRT.
Increase in treatment accuracy
