Left Breast Deep Inspiration
Breath Hold Treatment Based on
3D Surface Matching
X Tang, J Lian, S Chang, Z Xu, J Halle,
E Jones, and L Marks
Department of Radiation Oncology
University of North Carolina Chapel Hill
xiaoli_tang@med.unc.edu
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UNC School of Medicine
Outline
• Respiratory gating at the DIBH mode
♦ Motivation
♦ External gating
• AlignRT Beam Hold—a VisionRT gating
software
• DIBH clinical flow in UNC
♦ At CT SIM
♦ Daily treatment
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Deep inspiration
• Moves the heart
inferior & posterior
• Displacing it from
the left breast
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Why gate breast patient?
• DIBH can maximize the distance between
chest wall and heart—to reduce cardiac
toxicity
Breath
hold
DIBH
CT
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Free breathing
Regular
CT
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Heart DVH comparison
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Literature review
Toronto Sunnybrook regional cancer centre
• 5 patients: Decreased
volume
irradiated
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Literature review (cont.)
• 5 patients: Achieved a mean absolute
reduction of
in heart volume
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External gating
• External surrogate systems
♦ Varian RPM system—track a block on abdomen
♦ Siemens Anzai system—track abdomen amplitude
♦ VisionRT GateRT system—track one point on breast
surface
• Direct breast surface matching system
♦ VisionRT AlignRT Beam Hold system—track breast
surface
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External surrogate systems
• Indirect tracking
• A block, a belt, or a point on a surface
RPM
Photos courtesy of P Keall,
VisionRT Ltd., and Siemens
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Anzai
GateRT
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AlignRT Beam Hold
• 3D imaging solution for patient setup
and real time tracking during RT
• Non-invasive
• Does not require any markers
• Does not require additional radiation
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VisionRT system in treatment room
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3D surface rendering
CT skin rendering
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Real patient surface
Patient surface
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Surface matching algorithm
• Gating based on real-time deltas
• R stands for reference 3D image
(either CT surface rendering or
patient surface image)
• V stands for verification 3D image
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Real time deltas
• Real time register V to R
• The following deltas have to meet the preset threshold in order to BEAM ON
| VRTR  VRTV |
| LONGR  LONGV |
| LATR  LATV |
| VRTR  VRTV |2  | LONGR  LONGV |2  | LATR  LATV |2
| VRT  VRT |

R
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
V
| LONGR  LONGV |
| LATR  LATV |
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Surface matching based
DIBH in UNC
• Started July 2010—first in the US
• Treated more than 30 patients
• 15 min slot for daily treatment
• 6 DIBH patients this week
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AT CT SIM
• Obtain one set of regular CT
• Obtain one set of deep inspiration
breath hold CT
• Tattoo patient the conventional way
(free breathing)
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Threshold selection
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Patient setup
• Align patient based on tattoos
• Adjust couch position when patient holds
her breath at DIBH mode—to meet all
AlignRT Beam Hold tolerance (threshold)
• On port film days, take films while patient
holds her breath and all tolerances are met
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Reference images
Non-bolus days
CT skin rendering
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Bolus days
Surface capture at DIBH
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Real-time delta
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Gated treatment
• Coach patient to hold her breath
♦ Audio coaching
♦ Video coaching
• Beam ON automatically when all
tolerances met
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Real-time delta example
BEAM ON
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BEAM OFF
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Port film example—with and without
breath hold (BH)
Port w/o BH
Port w/ BH
DRR
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Port film example—with bolus
DRR
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Port with BH and bolus
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Future clinical application
• Head and Neck
Photos courtesy of CDR systems
• All other sites—surface is better than
3 tattoos
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Acknowledgment
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