Immobilization from rigid
to non-rigid
Sanford Meeks
August 5, 2011
Disclosure
• Sanford Meeks is an inventor on a patent licensed by University
of Florida to Varian Medical Systems.
• MD Anderson Cancer Center Orlando has received research
funding from TomoTherapy and BrainLab.
• I attempted to be vendor neutral/vendor inclusive.
• All products discussed in this lecture have FDA clearance.
Learning Objectives
• Review general patient positioning and immobilization
devices.
• Review site-specific immobilization devices
• Interfraction uncertainties (Setup)
• Intrafraction uncertainties (motion during treatment)
Immobilization vs Localization
• Immobilization systems: reproducibly position patients
and help keep them still during treatment.
• Localization systems: locate patients relative to the
treatment unit. Mechanical, CT Fiducials + lasers, IGRT,
IR, RF, etc.
We are discussing immobilizers, but immobilization and
localization are often inextricably linked. Hence, some of
uncertainties I attribute to a particular immobilizer may
belong to the localization system...
Ideal immobilization
• Secures patient and constrains
motion in “comfortable position”
• Does not interfere with simulation or
treatment
• Size constraints for sim/IGRT
• no high Z materials
• Does not interfere with localization
• Maintains its integrity throughout
treatment course
• Easy to use
• Inexpensive
Ideal immobilization
• Secures patient and constrains
motion in “comfortable position”
• Does not interfere with simulation or
treatment
• Size constraints for sim/IGRT
• no high Z materials
• Does not interfere with localization
• Maintains its integrity throughout
treatment course
• Easy to use
• Inexpensive
• As with most things in life, there is a
compromise between ideal and
reality…
Generic positioning devices
While not strictly “immobilizers”, standard patient
positioning wedges, bolsters and pads can be used
to aid in patient comfort and reproducible
positioning.
Generic positioning devices:
head and neck
TIMO head and neck supports are made of molded
polyurethane foam. They come in six different heights
and contours to attain the desired head angulation and/or
neck position.
Generic positioning devices:
head and neck
Silverman head and neck supports have the same
geometry as TIMO head holders, but are made of thin
clear plastic to minimize build-up and beam attenuation.
Generic positioning devices:
chest/thorax
• Wing board is used to help position patient’s arms overhead.
• Breast board positions patient’s arm overhead to move it out of the
way for tangent fields. Also can be used to incline patient and
provide flat sternal angle.
Custom support: MoldCare Head Cushion
(Bionix Radiation Therapy, Toledo, OH) is a soft fabric bag containing
resin coated polystyrene beads that are coated in a moisture-cured
polyurethane resin. When sprayed with room temperature water the
cushion becomes moldable and can be molded to the patient’s head
and neck. After 5-10 minutes the cushion hardens to form a rigid
custom support.
Custom Casts: polyurethane foam
• When the two parts are combined
and mixed thoroughly, an
exothermic reaction expands the
foam’s volume up to 40 times and
it eventually hardens into a rigid,
closed cell polyurethane.
• Alpha Cradle (Smithers Medical Products)
• RediFoam (Civco Medical Solutions)
Custom Casts: polyurethane foam
• The two parts are mixed and poured into a bag. The
bag is placed under the patient (in the treatment
position) and allowed to harden for about 15 minutes.
Custom Casts: evacuated vacuum cushions
• Popular alternative because of
their reusablility.
• Vac-lok bags are filled with
small styrofoam balls. A
vacuum pump is used to
evacuate the air from the bag,
making it rigid. When bag is
placed under a patient and the
air is evacuated, the patient’s
form is left as an imprint in the
bag.
•
The most common brand is Vac-Lok
(Civco Medical Solutions).
Vacuum bags
Thermoplastic Masks
Thermoplastic Masks
(some) vendors:
Aktina Medical (Congers, NY),
Bionix Radiation Therapy (Toledo, OH),
Civco Medical Solutions (Orange City, IA),
Orfit Industries (Jericho, NY),
WFR-Aquaplast (Wyckoff, NJ).
Double vacuum system: BodyFix
Elekta
Site Specific Uncertainties: Disclaimers
• Many publications
• Difficult to make sense of, compare, and summarize
•
•
•
•
•
Population Mean? Mean of means? Directional or not?
Standard deviation?
Σ (systematic)?
σ (random)?
M?
• I included 64 references, so I missed about 1000 –
apologies for those I missed
Site Specific Uncertainties: Disclaimers
• Many publications (apologies for those missed)
• Difficult to make sense of, compare, and summarize
•
•
•
•
•
Population Mean? Mean of means? RMS or not?
Standard deviation?
Σ (systematic)?
σ (random)?
M?
• What is important?
• These numbers all
obtained on study…
What do they look like
at your institution?
The data don’t make any sense.
We will have to resort to statistics.
Site Specific: Intracranial
Stereotactic Headring – Most Rigid System
Intracranial: Stereotactic Head Ring
Stereotactic = three‐dimensional localization
Image space and treatment space are linked. Historically this has been accomplished using the rigid head ring
Stereotactic Head ring
Immobilization Device
Stereotactic Head Ring
Expected Uncertainty (mean setup
error)
1.0 mm 1
MC Schell, et al, AAPM Report No. 54: Stereotactic Radiosurgery - Report
of Task Group 42. (1995).
Nomos Talon
BJ Salter et al., "The TALON removable head frame system
for stereotactic radiosurgery/radiotherapy: measurement of
the repositioning accuracy," Int J Radiat Oncol Biol Phys 51,
555-562 (2001).
Nomos Talon
Immobilization Device
Expected Uncertainty
Talon
1.38 ± 0.48 mm
BJ Salter et al., "The TALON removable head frame system
for stereotactic radiosurgery/radiotherapy: measurement of
the repositioning accuracy," Int J Radiat Oncol Biol Phys 51,
555-562 (2001).
Gill-Thomas-Cosman Frame
Straps
Custom biteplate
Occipital support
G. Bednarz, et al., "Report on a randomized trial comparing two
forms of immobilization of the head for fractionated stereotactic
radiotherapy," Med Phys 36, 12-17 (2009).
Gill-Thomas-Cosman Frame
Immobilization Device
GTC Frame
Expected Uncertainty (mean setup
error)
2.00+1.04 mm
G. Bednarz, et al., "Report on a randomized trial comparing two
forms of immobilization of the head for fractionated stereotactic
radiotherapy," Med Phys 36, 12-17 (2009).
Bite plate/HeadFix
1. RA Sweeney, et al., "A simple and non-invasive vacuum mouthpiece-based head fixation system for
high precision radiotherapy," Strahlenther Onkol 177, 43-47 (2001).
2. R Sweeney, et al., "Repositioning accuracy: comparison of a noninvasive head holder with
thermoplastic mask for fractionated radiotherapy and a case report," Int J Radiat Oncol Biol Phys 41, 475483 (1998).
3. E. Kunieda, et al, "The reproducibility of a HeadFix relocatable fixation system: analysis using the
stereotactic coordinates of bilateral incus and the top of the crista galli obtained from a serial CT scan,"
Phys Med Biol 54, N197-204 (2009).
Bite plate/HeadFix
Immobilization Device
HeadFix Biteplate
Expected Uncertainty (mean setup
error)
< 2.0 mm 1, 2, 3
1. RA Sweeney, et al., "A simple and non-invasive vacuum mouthpiece-based head fixation system for
high precision radiotherapy," Strahlenther Onkol 177, 43-47 (2001).
2. R Sweeney, et al., "Repositioning accuracy: comparison of a noninvasive head holder with
thermoplastic mask for fractionated radiotherapy and a case report," Int J Radiat Oncol Biol Phys 41, 475483 (1998).
3. E. Kunieda, et al, "The reproducibility of a HeadFix relocatable fixation system: analysis using the
stereotactic coordinates of bilateral incus and the top of the crista galli obtained from a serial CT scan,"
Phys Med Biol 54, N197-204 (2009).
Intracranial Mask Systems
Reference
Immobilization Device
Mean 3D
error (mm)
Boda-Heggemann et al., 2006
Scotch-cast (head)
Thermoplastic (head)
Scotch-cast (head)
Thermoplastic (head)
Thermoplastic (head)
Thermoplastic (head) + bite block
Thermoplastic (head)
Thermoplastic (head) + body cast
Thermoplastic (head and shoulder)
Thermoplastic (head and shoulder) +
bite block
3.1± 1.5
4.7± 1.7
3.0± 1.7
4.6± 2.1
3.2± 1.5
2.9± 1.3
2.3 ± 1.5
2.2 ± 1.1
2.7±1.5
2.1±1.0
Guckenberger et al., 2007
Masi et al., 2008
Tryggestad et al., 2011
These are all recent studies using in-room image guidance as truth. Note that
there are big differences in errors using same device (thermoplastic head) at
different institutions.
Immobilizing
shoulders
slightlyMotion
reduces intrafraction
Intracranial
Intrafraction
motion.
Immobilization Device
Difference Pre to Post Tx
1. Type-S IMRT (head only) mask (Civco) with
head cushion
1.1± 1.2 mm
2. Uni-Frame mask (Civco) with head cushion,
coupled with a BlueBag body immobilizer
(Medical Intelligence)
1.1 ± 1.1 mm
3. Type-S head and shoulder mask with head
and shoulder cushion (Civco)
0.7±0.9 mm
4. Type-S head and shoulder mask with head
and shoulder cushion (Civco) with biteplate
0.7±0.8 mm
E. Tryggestad, et al."Inter- and Intrafraction Patient Positioning
Uncertainties for Intracranial Radiotherapy: A Study of Four
Frameless, Thermoplastic Mask-Based Immobilization
Strategies Using Daily Cone-Beam CT," Int J Radiat Oncol Biol
Phys. 80(1):281-90, 2011.
Head and neck
Immobilization Device
Type-S thermoplastic
Bear-claw board
Expected Uncertainty (mean
setup error)
3.1±1.6 (sup landmarks)
8.0±4.5 (inf landmarks)
2.8±0.9 (sup landmarks)
8.0±5.5 (inf landmarks)
RL Rotondo, et al., "Comparison of repositioning accuracy of two commercially available
immobilization systems for treatment of head-and-neck tumors using simulation computed
tomography imaging," Int J Radiat Oncol Biol Phys 70, 1389-1396 (2008).
Spine
• Fractionated radiotherapy used
for palliation of spinal lesions
has typically relied on simple
immobilization techniques.
• Immobilization techniques for
SBRT of spinal lesions are more
elaborate.
SBRT of Spinal Targets
• Historically, spine SBRT relied on body frames and
rigid spine immobilization.
• Invasive spinal frame provided ~2.0 mm accuracy.
Hamilton, Lulu et al. Neurosurg 36:311, 1995.
SBRT of Spinal Targets
Today, typically performed using standard immobilization
techniques (themoplastic masks, vacuum systems, etc.)
in conjunction with image guidance (x-ray, CBCT) and
real-time monitoring during treatment.
SBRT of Spinal Targets
Immobilization Device
Expected Uncertainty (mean setup error, mm)
Screw fixation of
spinous process
(Hamilton, 1995)
Body cast with
stereotactic frame
(Lohr, 1997)
Custom stereotactic
frame (Yenice, 2003)
Scotch cast torso and
head masks
(Stoiber, 2009)
2 mm
≤3.6 mm
2-3 mm positioning accuracy
Cervical: 0.3±0.8 AP, -0.1±1.1 Lat, 0.1±0.9 SI
Thoracic: 0.3±0.8 AP, 0.8±1.1 Lat, 1.1±1.3 SI
Lumbar: 0.0±0.9 AP, -0.7±1.3 Lat, 0.5±1.6 SI
Again, we are probably using IGRT for high-precision treatments, and set up
uncertainty using the immobilizer may not be the big deal here.
Spinal Targets: Intrafraction Motion
Uncertainty increases,
with treatment time and
is worse for prone than
supine – probably due
to increased respiratory
motion.
After 15 minutes, median
uncertainty is ~1.5-2
mm
Hoogeman et al., Int J Radiat Biol Phys,
70(2):609-618, 2008.
Thorax/Lung
For conventional lung radiotherapy, typically use wing
board and/or vacuum cushion/polyurethane bag. SBRT
uses more elaborate systems.
Immobilization Device
Alpha Cradle/Vac-loc
Expected Uncertainty (mean setup error)
5 – 9 mm
Rabinowitz. Int J Radiat Oncol Biol Phys 11, 1857-1867, 1985.
Bissonnette et al. Int J Radiat Oncol Biol Phys 73, 927-934, 2009.
Bissonnette, et al. Int J Radiat Oncol Biol Phys 75, 688-695, 2009.
Lung SBRT
Abdominal compression 3.4 mm AP, 3.3 mm Lat, 4.4 mm S
J Wulf et al.Stereotactic radiotherapy of extracranial targets: CT-simulation and
(Elekta body frame)
accuracy of treatment in the stereotactic body frame. Rad Onc 57, 225, 2000.
2 mm
R. Hara et al. Stereotactic single high dose irradiation of lung tumors under
respiratory gating, Radiother Oncol 63, 159-163, 2002.
Y Nagata, et al. Clinical outcomes of 3D conformal hypofractionated single highdose radiotherapy for one or two lung tumors using a stereotactic body frame.
IJROBP 52, 1041-1046, 2002.
~5 mm
R. Timmerman. Extracranial stereotactic radioablation: results of a phase I study
in medically inoperable stage I non-small cell lung cancer," Chest 124, 19461955, 2003.
Abdominal compression 1.8-4 mm
(Leibinger body frame) H Hof, et al. Stereotactic single-dose radiotherapy of stage I non-small-cell lung
cancer (NSCLC). Int J Radiat Oncol Biol Phys 56, 335-341 2003.
BodyFix
2.5 mm
M. Fuss, et al. Repositioning accuracy of a commercially available doublevacuum whole body immobilization system for stereotactic body radiation
therapy," TCRT 3, 59-67, 2004.
0.3±1.8 mm AP, −1.8±3.2 mm Lat, 1.5±3.7 mm SI
L Wang et al. Benefit of three-dimensional image-guided stereotactic localization
in the hypofractionated treatment of lung cancer, IJROBP 66, 738-747, 2006.
Thorax/Lung – Intrafraction Motion
Immobilization
Device
BodyFix
Abdominal
Compression
None (free breathe)
Respiratory Tumor
Motion (mm)
5.3
Mean intrafraction tumor
motion (mm)
2.3
4.7
2.0
6.1
Abdominal compression was slightly better than the BodyFix,
was faster/easier to use and rated more comfortable by
patients (statistically significant).
K Han et al. A comparison of two immobilization systems for
stereotactic body radiation therapy of lung tumors. Radiother
Oncol 95(1):103-8, 2010.
Thorax/Lung – Intrafraction Motion
Using abdominal compression for
any patient with tumor excursion >
10 mm on 4DCT.
Using Vac-Lok only, 67% of
patients within 3-mm tolerance at
end of treatment.
Using Vac-Lok + compression,
74% of patients within 3-mm
tolerance at end of treatment.
Using image guidance and either
method, a 5-mm treatment margin
is sufficient to account for
intrafraction motion. This can be
reduced using frequent image
guidance.
W Li et al., Effect of Immobilization and Performance Status on
Intrafraction Motion for Stereotactic Lung Radiotherapy:
Analysis of 133 Patients. Int J Radiat Biol Oncol Phys in press,
2011
Breast
Immobilization Device
Breastboard with arm support
Vac-Lok
Breastboard with arm support
(Shah et al. submitted) – using VisionRT to
determine shifts from conventional setup
Expected Uncertainty (mm)
-1.7±2.8 mm AP,1.2±3.7 mm SI
-1.8±2.9 mm AP,0.4±2.3 mm SI
4.1 ± 2.6 AP, 2.7 ±1.4 S/I, 2.6 ± 1.2 mm Lat
Random error (σ ): 3.2 AP, 2.2 S/I, 2.2 Lat
CA Nalder, et al., "Influence of a vac-fix immobilization
device on the accuracy of patient positioning during
routine breast radiotherapy," Br J Radiol 74, 249-254
(2001).
Breast Intrafraction Motion
Using pre and post-treamtnet
CT imaging, the average
maximum motion of the
external contour was 1.3 ±
1.6 mm, whereas the chest
wall was found to be 1.6 ±
1.9 mm. “setup errors
dominate the motion errors”
J. H. Strydhorst, et al. "Evaluation of a thermoplastic
immobilization system for breast and chest wall
radiation therapy," Med Dosim 36, 81-84 (2011).
Abdomen
Immobilization Device Expected Uncertainty (mean setup error)
BodyFix
~2 mm AP, ~2 mm Lat, ~6 mm sup-inf
B. Wysocka et al. Interfraction and respiratory organ motion during conformal
radiotherapy in gastric cancer. IJROBP 77, 53-59, 2010.
Elekta Body Frame
3.7 mm Lat, 5.7 mm SI
I. Lax et al. Stereotactic radiotherapy of malignancies in the abdomen.
Methodological aspects. Acta Oncol 33, 677-683, 1994.
Leigbinger body frame 1.8-4.4 mm
K. Herfarth et al.Extracranial stereotactic radiation therapy: set-up accuracy of
patients treated for liver metastases. IJROBP 46, 329-335, 2000.
Abdominal Intrafraction Motion
Using BodyFix – various abdominal organs relative to
bony anatomy. Median interfraction variability is ~
6 mm in sup-in direction. Median respiratory
amplitude is ~16 mm with individual dispersion
ranging from 0-60 mm. “… individual assessment of
respiratory motion is warranted.”
Older publications indicate that abdominal
compression can reduce motion to 5-8 mm…
B. Wysocka, et al. "Interfraction and respiratory organ motion
during conformal radiotherapy in gastric cancer," Int J Radiat
Oncol Biol Phys 77, 53-59 (2010).
Prostate Cancer
Prostate Uncertainty
Reference
S. Malone et al. A prospective
comparison of three systems of
patient immobilization for prostate
radiotherapy. Int J Radiat Oncol
Biol Phys 48, 657-665, 2000.
S. Frank, et al. Quantification of
prostate and seminal vesicle
interfraction variation during IMRT.
Int J Radiat Oncol Biol Phys 71,
813-820 , 2008.
T Rosewall et al. A randomized
comparison of interfraction and
intrafraction prostate motion with and
without abdominal compression.
Radiother Oncol 88(1):88-94, 2008.
Immobilization
Device
Generic leg support
Full alpha cradle
Hip Fix (thermoplastic)
mean setup error (mm)
6.5
6.0
4.6
VacLok
4.6±3.5 (prostate),
7.6±4.7 (seminal vesicles)
BodyFix
7.6 (median AP)
4.7 (median SI)
Prostate Immobilization: Endorectal Balloon
to reduce intrafraction motion
Prostate Immobilization: Endorectal Balloon
AP
SI
3D-vector
150 s
300 s
600 s
1050 s
150 s
300 s
600 s
1050 s
150 s
300 s
600 s
1050 s
> 1 mm
No ERB
ERB
2.0%
0.7%
4.8%
1.9%
9.4%
3.8%
10.2%
3.9%
3.2%
2.5%
7.2%
6.7%
13.3%
12.3%
14.2%
12.6%
14.7%
10.0%
34.8%
29.0%
70.2%
57.7%
74.6%
59.5%
> 3 mm
No ERB
ERB
0.4%
0.0%
1.0%
0.1%
2.6%
0.3%
3.0%
0.3%
0.3%
0.0%
1.0%
0.3%
2.5%
1.2%
2.7%
1.3%
1.4%
0.2%
5.4%
1.3%
18.1%
7.0%
20.4%
7.9%
Statistically significant differences in
motion with and without ERB at 1- and
3-mm thresholds
R. Smeenk et al., "The Influence of an endorectal
balloon on intrafraction prostate motion," Int J
Radiat Oncol Biol Phys 78, 2 (2010).
> 5 mm
No ERB
ERB
0.1%
0.0%
0.4%
0.0%
1.2%
0.0%
1.5%
0.0%
0.0%
0.0%
0.1%
0.0%
0.4%
0.2%
0.5%
0.2%
0.3%
0.1%
1.1%
0.2%
4.6%
0.7%
5.6%
0.9%
Little motion outside
of 5 mm window
with or without ERB
Prostate Motion: Prone vs. Supine
“Good” session
Prone
Prone Prostate Tracking
1
LEFT/RIGHT
SUP/INF
ANT/POST
3-D
0.8
0.6
Drift + periodic motion
Isocenter Offset (cm)
0.4
0.2
0
Supine
Supine Prostate Tracking
-0.2
1
LEFT/RIGHT
SUP/INF
ANT/POST
3-D
-0.4
0.8
-0.6
0.6
-0.8
Primarily drift
0.4
-1
100
200
300
400
500
600
Time (seconds)
Time
Isocenter Offset (cm)
0
70
0.2
0
-0.2
-0.4
Shah AP et al. An evaluation of intrafraction
motion of the prostate in the prone and supine
positions using electromagnetic tracking.
Radiother Oncol, 99(1):37-43, 2011.
-0.6
-0.8
-1
0
100
200
300
Time
400
Time (seconds)
500
600
700
Prostate Motion: Prone vs. Supine
“Bad” session
Prone
Prone Prostate Tracking
1
LEFT/RIGHT
SUP/INF
ANT/POST
3-D
0.8
0.6
Isocenter Offset (cm)
0.4
0.2
Drift + periodic motion
0
Supine
Supine Prostate Tracking
-0.2
-0.4
1
-0.6
0.8
-0.8
0.6
LEFT/RIGHT
SUP/INF
ANT/POST
3-D
Primarily drift
0.4
0
100
200
300
400
500
Time (seconds)
Time
Isocenter Offset (cm)
-1
600
0.2
0
-0.2
-0.4
Shah AP et al. An evaluation of intrafraction
motion of the prostate in the prone and supine
positions using electromagnetic tracking.
Radiother Oncol, 99(1):37-43, 2011.
-0.6
-0.8
-1
0
100
200
300
Time
400
Time (seconds)
500
600
Prostate Motion: Prone vs. Supine
Shah AP et al. An evaluation of intrafraction motion of the
prostate in the prone and supine positions using
electromagnetic tracking. Radiother Oncol, 99(1):37-43, 2011.
Prone Pelvis
Immobilization Device
Belly board
Expected Uncertainty (mean setup
error)
4.5 mm AP, 3.2 mm Lat, 4.2 mm SI
A. S. Allal, S. Bischof and P. Nouet, "Impact of the
"belly board" device on treatment reproducibility in
preoperative radiotherapy for rectal cancer,"
Strahlenther Onkol 178, 259-262 (2002).
Summary – Interfraction Uncertainty
Disclaimer: Sanford’s Summary
Anatomic Site
Expected Uncertainty
Intracranial
Head and Neck
Spine
Lung
Lung - SBRT
1.0 (most rigid) - 3.5 (least rigid) mm
~3 mm (base of skull)
~8 mm (low neck)
2 – 4 mm
5 – 9 mm
2.5-5 mm
Breast
Abdomen
Prostate
Prone Pelvis
~4 mm systematic, 4.4 mm random
4.5-7 mm
4.5-6.5 mm (7.5 for svs)
~7mm
1. Only relevant for conventional set-ups and
in a study… not necessarily same at home.
2. Using IGRT, uncertainty is defined by IGRT
system.
Summary – Intrafraction Uncertainty
Disclaimer: Sanford’s Summary
Anatomic Site
Expected Uncertainty (Difference pre/post)
Intracranial
Head and Neck
~1.0 mm (mask systems)
~1.5 mm
Spine
Lung
~1.5 (supine), ~2.5 (prone) mm – median at 15 minutes
~2.5 mm post treatment, ~ 6 mm respiratory motion
(i.e. expect 2.5 mm with resp. management, worse without)
~2 mm for external surface and chest wall (using thermoplast
overlay)
Median respiratory amplitude is 16 mm. 5-8 mm with
abdominal compression
~2 mm median at 15 min, reduced to < 1.5 mm with ERB
~2.5 mm median at 15 min (prostate)
Breast
Abdomen
Prostate
Prone Pelvis
Repeated use of IGRT or use of tracking
systems may reduce these uncertainties.
Thank You