Acknowledgement
Online Adaptive Radiotherapy for Prostate Cancer:
Clinical Implementation and Initial Experience


X. Allen Li
E. Ahunbay, C. Peng, G. Chen,
F. Liu, C. Lawton


Doug Prah, Ph.D
Esther Chang, Ph.D
Andrew Godley, Ph.D
Dian Wang, MD




J. Frank Wilson, MD
Beth Erickson, MD
Chris Schultz, MD
Julia White, MD
Supports from Siemens OCS and Prowess Inc
AAPM, 10:30AM, Ballroom A, Aug. 4, 2011
Inter-fractional
variation:
Head & Neck: Daily Variation
Tumor of the day
Cord and
Tumor from
planning CT
Five days
1
Bladder: unpredictable inter-fraction change
Prostate: unpredictable inter-fraction change
On-line ART
On-line ART
Prostate daily maximum overlap rate
20 prostate cases
Histogram of Daily Prostate MOR
20
18
16

Repositioning
Re-planning
Frequency of online re-planning
Prostate (3 mm PTV margin):
Repositioning: 50-70% of fractions
Replanning: 25-40% of fractions
Frequency
14
12
Online Replanning frequency increases with smaller PTV margins
10
8
6
4
2
0
60%
65%
70%
75%
80%
85%
90%
95%
100%
Daily Prostate MOR (%)
2
Online Adaptive replanning
Online ART
Image Acquisition via CT-on-Rails
Contour generation (auto segmentation with manual editing) 2-5 min
A full-scope re-optimization with
available systesms is too slow to be
practical.
Need fast replanning methods !
Segment Aperture Morphing (SAM) & Segment Weight Optimization (SWO) 2 min
Dose/DVH evaluation and comparison
1 min
ART plan transferring & QA verification with software
2 min
Delivery and documentation
8-12 min for prostate, comparable to current repositioning !!!
Implemented in RealArt by Prowess Inc
Rapid contour delineation/modification
Software:
Hardware:
•auto segmentation
•drag and drop planning contours
• interpolate contours for skipped images
Fast plan modification:
Segment Aperture Morphing
user-friendly interactive Grip
pen display (Cintiq 21UX,
Wacom).
Dropping contours from planning CT
Drawing tablet
and pen
Implemented in RealART, Prowess Inc.
Moving in Sagittal/Coronal view
Decimating/Interpolating slices
3
Software tools for QA prior and after delivery:
Prostate case (2 fractions)
Planning CT
verifying MU#, plan data transferring and actual delivery
CT of Fr#1
Prostate (2 fractions)
Moderate Deformation
Overlap: 0.85
CT of Fr#2
Moderate Deformation
Large Deformation
Overlap: 85%
Overlap: 74%
Planning contour (pink) overlaid on daily CT
Large Deformation
Overlap: 0.74
Planning
PTV margin: 0 mm
4
Clinical case: prostate cancer
Rectum
Rectum
target
bladder
Dash: repositioning. Solid: online ART
PTV margin: 3 mm
Clinical case: bladder cancer, Fx#1
Projected
reduction in
rectal bleeding
5
Bladder cancer, Fx#1
Initial Clinical Experience
The online replanning has been used on 12 prostate
cancer cases and one bladder cancer case so far.
Rectum
target
The online replanning process, eliminating the need to
shift the patient, can be performed within the similar or
slightly longer time frame required for the current IGRT
repositioning and fits into the routine clinical workflow.
Large Bowel
Dash: repositioning. Solid: RealART replanning
Repositioning
Lumpectomy cavity volume and shape change
Replanning
Online ART
for PBI
PTV
PTV
PTV
Breast - PTV
1
1
0.9
0.9
0.8
Fractional Volume
Fractional Volume
0.8
0.7
Repositioning
Replanning
0.6
0.5
0.4
0.3
0.7
Replanning
0.6
Repositioning
0.5
0.4
0.3
0.2
0.2
0.1
0.1
0
0
0
20
40
60
Dose (%-prescription)
80
100
120
0
20
40
60
80
100
120
Dose (%-prescription)
6
Inter-fractional motion: pancreas
Online Adaptive Replanning
• ART allows smaller (3mm) PTV margin, compared to
repositioning with typical 10 mm margin)
AP Projections, based gated daily CT
Adaptive v.s. Repositioning
• Duodenum
10 cases
Dosimetric Impact of RT delivery
technologies on pancreas RT
Duodenum V50.4
L-Kidney V15
R-Kidney V15
Large Bowel V45
Stomach V45
Liver V30
Small Bowel V45
Online ART IGRT
gating
gating
IGRT
No gating
no IGRT
no gating
19%
8%
14%
0.4%
1%
2%
1%
66%
22%
32%
8%
9%
13%
10%
72%
19%
35%
11%
11%
17%
12%
42%
15%
23%
3%
4%
6%
4%
Average of 5 patients
7
Summary

The current standard of IGRT (repositioning) can not
address volume change, deformation and rotation.

Methods have been developed to perform online fast
replanning.

Online replanning can address translational and
rotational shifts and deformation, eliminating
repositioning.

The online replanning allows smaller PTV margins.

The online replanning enables “image-plan-treat”, the
future of RT practice, particularly important for
hypofractionations, SBRT
8