33
RADIATION ONCOLOGY First Experience on Real-Time Motion Synchronization with the Radixact® System X. Allen Li Professor and Chief Physicist Accuray AERO, Amsterdam, Feb 8th, 2020
RADIATION ONCOLOGY
First Experience on Real-Time Motion Synchronization with the Radixact® System
X. Allen Li
Professor and Chief Physicist
Accuray AERO, Amsterdam, Feb 8th, 2020
Disclosure
FH-MCW receive research funding from Accuray
Incorporated
DisclaimerThe views expressed in this presentation are those of the presenters and do not
necessarily reflect the views or policies of Accuray Incorporated or its subsidiaries.
No official endorsement by Accuray Incorporated or any of its subsidiaries of any
vendor, products or services contained in this presentation is intended or should
be inferred.
Organ motion can
be complex and is
a major problem in
radiation therapy!
Irregular Motion in Pelvis
RADIATION ONCOLOGY
Accuray Motion Tracking and Correction: Synchrony® on Radixact ®
Synchrony® is real-time adaptive delivery of a treatment plan
Schnarr et al, Med Phys. 2018 45:1329
Image Credit:
J. Smilowitz,
UW Madison
kV
Detector
kV
Source
RADIATION ONCOLOGY
Synchrony® on Radixact®
▪ Sequential kV x-rays radiography during
helical delivery to detect lung targets or
fiducials
▪ Dynamic jaws and fast binary MLC “re-
point” the beam to known position of the
target with sub-mm accuracySchnarr et al, Med Phys. 2018 45:1329
RADIATION ONCOLOGY
Synchrony®• Respiratory motion: LED markers
detected by camera
• Tracking modalities
– Quasi-static:
irregular motion + fiducial(s)
– Respiratory with fiducials:
respiration motion + fiducial(s)
– Respiratory without fiducial:
respiration motion + trackable
target
• Plan type settings
– Helical
– Fixed/dynamic jaws
– Jaw width: 1.0 cm, 2.5 cm
RADIATION ONCOLOGY
Synchrony® Clinical implementation @ F-MCW
➢ Software upgrade (3 days)
▪ Radixact® Treatment Delivery System v2.0 (Console Software
V7.0)
▪ iDMS® Data Management System v3.0
▪ Precision® TPS v3.0
➢ Hardware installation (3 days)
▪ Camera system
▪ kV imaging system
➢ Commissioning and QA (over 3 weeks)
➢ 7/24/2019: First patient treatment
RADIATION ONCOLOGY
Synchrony
RADIATION ONCOLOGY
Accuracy of tracking LED motion
RMS error (mm)
Synchrony® Fiducial Tracking 0.67
Synchrony Fiducial Tracking with Respiratory Modelling 0.25
Synchrony Lung Tracking 0.43
RADIATION ONCOLOGY
DQA: Effect of Motion Tracking on 3D Dosimetry
Tracking mode Gamma Passing Rate (%)
Irregular motion with fiducials 97.2
Respiration motion with fiducials 99.5
Respiration motion without fiducials 100.0gamma criteria: 3 mm 3% with 5% threshold
RADIATION ONCOLOGY
Effect of Motion Correction on 2D Dose Measurement
With motion, correction
No motion, no correction
With motion, correction
No motion, no correction
Motion amplitude of ±12mm, frequency of 2.5s.
With motion, no correction
No motion, no correction
With motion, no correction
No motion, no correction
RADIATION ONCOLOGY
kV radiography dose
Quantity
Cen
ter 0˚ 90˚ 180˚ 270˚
average (pC)
145.
69
185.
52
226.
55
177.
39
222.
72
Average (mGy) 1.20 1.53 1.86 1.46 1.83
CTDI100 (mGy) 1.20 1.53 1.86 1.46 1.83
CTDI100(peripheral) (mGy) 1.67
CTDIw (mGy) 1.51
CTDIw/projection (mGy) 0.084
For a typical Synchrony® tracking treatment, ~ 50 radiographic imaging projections may be used, which corresponds to 4.2 mGy
RADIATION ONCOLOGY
DQA: Effect of Motion Tracking on 3D Dosimetry
gamma criteria: 3 mm 3% with 5% threshold
Tracking respiration motion (±10 mm) without fiducials
Checklists
Synchrony®
The First Case Treated with Synchrony® on Radixact®
❑ 45 year old male with
stage IV colorectal
cancer with pulmonary
metastases in lung.
❑ Max GTV diameter:
2.7cm
❑ Respiration motion of 7
mm in superior-inferior
direction
❑ SBRT of 54 Gy in 3
fractions.
Two Plans:1) GTV from mid-position CT for Motion Synchronization plan
2) ITV from 10-phase 4DCT for non-correction plan
ITV
GTV
Two Plans:1) PTVSync = GTV+5mm for Motion Synchronization plan
2) PTV = ITV+5mm for non-correction plan
PTVSync
PTV
Motion Synchronization vs. Non-Correction
Plans
Motion correction
enabled higher
GTV dose
Motion Synchronization vs. Non-Correction Plans
Motion
correction plan
No correction
plan
% Diff
PTV 18.3cc 26.3cc -30%
Max Dose in GTV/ITV 69.7 66.6 +5%
Lung V20 3.3% 3.5% -6%
Lung V5 15.9% 17.9% -11%
Mean lung dose 2.79Gy 3.13Gy -12%
The motion correction enabled a higher tumor
dose with no cost to the normal tissue doses.
Pre-Tx DQA
Passing
rate:
100%
Determining/verifying radiography angles
Selecting
appropriate
tracking
parameters
PreciseART®
Dose trending from PreciseART®
Motion correction plan No correction plan
Motion
correction
plan
No
correction
plan
% Diff
GTV=2.5cc ITV=4.0cc -60%
Lung V20 2.3% 3.2% -28%
Lung V5 14.3% 17.9% -20%
Mean lung
dose
2.38Gy 3.00Gy -20%
Max Cord
dose
12.8Gy 14.3Gy -12%
The motion correction reduced the
dose to spinal cord
2nd case: Lung SBRT, 3x18Gy
4th case, lung, 5x10Gy, SBRT
Observations from initial experience
➢ Carefully selecting patients (target size, location, motion,
visibility on kV radiography…)
➢ Proper tracking parameter setting
➢ Appropriate LED placement
➢Delivery time with motion correction: 16-30 min (10-20Gy)
(door to door)
➢Synchrony® jaw-MLC motion tracking is an effective
motion management strategy
Acknowledgements
• Guangpei Chen, PhD
• An Tai, PhD
• Tim Keiper, PhD
• Sara Lim, PhD
• Elizbeth Gore, MD
• Lindsay Puckett, MD
• Colleen Lawton, MD
• Chris Schultz, MD Technical support from
Accuray
