immobilization from rigid to non-rigid

Immobilization from rigid to non-rigidSanford 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 devicesWhile 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 allobtained on study…What do they look likeat your institution?

The data don’t make any sense. We will have to resort to statistics.

Site Specific: IntracranialStereotactic Headring – Most Rigid System

Intracranial: Stereotactic Head Ring

Stereotactic = three‐dimensional localizationImage space and treatment space are linked. Historically this has been accomplished using the rigid head ring

Stereotactic Head ring

Immobilization Device Expected Uncertainty (mean setup error)

Stereotactic Head Ring 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

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).

Immobilization Device Expected Uncertainty

Talon 1.38 ± 0.48 mm

Gill-Thomas-Cosman Frame

Custom biteplate

Occipital support

Straps

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


GTC Frame 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, 475-483 (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

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, 475-483 (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).


HeadFix Biteplate < 2.0 mm 1, 2, 3

Intracranial Mask SystemsReference Immobilization Device Mean 3D

error (mm)Boda-Heggemann et al., 2006

Guckenberger et al., 2007

Masi et al., 2008

Tryggestad et al., 2011

Scotch-cast (head)Thermoplastic (head)Scotch-cast (head)Thermoplastic (head)Thermoplastic (head)Thermoplastic (head) + bite blockThermoplastic (head)Thermoplastic (head) + body castThermoplastic (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 ± 1.52.2 ± 1.12.7±1.5 2.1±1.0

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.

Intracranial Intrafraction Motion

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 BiolPhys. 80(1):281-90, 2011.

Immobilization Device Difference Pre to Post Tx

1. Type-S IMRT (head only) mask (Civco) with head cushion

2. Uni-Frame mask (Civco) with head cushion, coupled with a BlueBag body immobilizer (Medical Intelligence)

3. Type-S head and shoulder mask with head and shoulder cushion (Civco)

4. Type-S head and shoulder mask with head and shoulder cushion (Civco) with biteplate

1.1± 1.2 mm

1.1 ± 1.1 mm

0.7±0.9 mm

0.7±0.8 mm

Immobilizing shoulders slightly reduces intrafractionmotion.

Head and neckImmobilization Device Expected Uncertainty (mean

setup error)Type-S thermoplastic 3.1±1.6 (sup landmarks)

8.0±4.5 (inf landmarks)Bear-claw board 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.


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.


Immobilization Device Expected Uncertainty (mean setup error, mm)

Screw fixation of spinous process(Hamilton, 1995)

2 mm

Body cast with stereotactic frame(Lohr, 1997)

≤3.6 mm

Custom stereotactic frame (Yenice, 2003)

2-3 mm positioning accuracy

Scotch cast torso and head masks (Stoiber, 2009)

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

Immobilization Device Expected Uncertainty (mean setup error)Alpha Cradle/Vac-loc 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.

For conventional lung radiotherapy, typically use wing board and/or vacuum cushion/polyurethane bag. SBRT uses more elaborate systems.

Lung SBRTAbdominal compression (Elekta body frame)

3.4 mm AP, 3.3 mm Lat, 4.4 mm SJ Wulf et al.Stereotactic radiotherapy of extracranial targets: CT-simulation and accuracy of treatment in the stereotactic body frame. Rad Onc 57, 225, 2000.

2 mmR. 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 high-dose radiotherapy for one or two lung tumors using a stereotactic body frame.IJROBP 52, 1041-1046, 2002.

~5 mmR. Timmerman. Extracranial stereotactic radioablation: results of a phase I study in medically inoperable stage I non-small cell lung cancer," Chest 124, 1946-1955, 2003.

Abdominal compression (Leibinger body frame)

1.8-4 mmH 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 mmM. Fuss, et al. Repositioning accuracy of a commercially available double-vacuum 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 SIL 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

K Han et al. A comparison of two immobilization systems for stereotactic body radiation therapy of lung tumors. RadiotherOncol 95(1):103-8, 2010.

Abdominal compression was slightly better than the BodyFix, was faster/easier to use and rated more comfortable by patients (statistically significant).

Immobilization Device

Respiratory TumorMotion (mm)

Mean intrafraction tumor motion (mm)

BodyFix 5.3 2.3

AbdominalCompression

4.7 2.0

None (free breathe) 6.1

Thorax/Lung – Intrafraction Motion

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

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.

Breast

Immobilization Device Expected Uncertainty (mm)Breastboard with arm support -1.7±2.8 mm AP,1.2±3.7 mm SI Vac-Lok -1.8±2.9 mm AP,0.4±2.3 mm SI Breastboard with arm support(Shah et al. submitted) – using VisionRT to determine shifts from conventional setup

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 MotionUsing pre and post-treamtnetCT 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).

AbdomenImmobilization 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 SII. 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 mmK. 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 RadiatOncol Biol Phys 77, 53-59 (2010).

Prostate Cancer

Prostate UncertaintyReference Immobilization

Devicemean setup error (mm)

S. Malone et al. A prospective comparison of three systems of patient immobilization for prostate radiotherapy. Int J Radiat OncolBiol 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.

Generic leg support 6.5 Full alpha cradle 6.0 Hip Fix (thermoplastic) 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> 1 mm > 3 mm > 5 mm

No ERB ERB No ERB ERB No ERB ERB

AP

150 s 2.0% 0.7% 0.4% 0.0% 0.1% 0.0%300 s 4.8% 1.9% 1.0% 0.1% 0.4% 0.0%600 s 9.4% 3.8% 2.6% 0.3% 1.2% 0.0%1050 s 10.2% 3.9% 3.0% 0.3% 1.5% 0.0%

SI

150 s 3.2% 2.5% 0.3% 0.0% 0.0% 0.0%300 s 7.2% 6.7% 1.0% 0.3% 0.1% 0.0%600 s 13.3% 12.3% 2.5% 1.2% 0.4% 0.2%1050 s 14.2% 12.6% 2.7% 1.3% 0.5% 0.2%

3D-vector

150 s 14.7% 10.0% 1.4% 0.2% 0.3% 0.1%300 s 34.8% 29.0% 5.4% 1.3% 1.1% 0.2%600 s 70.2% 57.7% 18.1% 7.0% 4.6% 0.7%1050 s 74.6% 59.5% 20.4% 7.9% 5.6% 0.9%

Little motion outside of 5 mm window with or without ERB

R. Smeenk et al., "The Influence of an endorectal balloon on intrafraction prostate motion," Int J Radiat Oncol Biol Phys 78, 2 (2010).

Statistically significant differences in motion with and without ERB at 1- and 3-mm thresholds

Prostate Motion: Prone vs. Supine“Good” session

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 Prostate Tracking

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Prone

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Drift + periodic motion

Supine Prostate Tracking

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Primarily drift

Prostate Motion: Prone vs. Supine“Bad” session


Prone Prostate Tracking

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Supine Prostate Tracking

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Prostate Motion: Prone vs. Supine


Prone PelvisImmobilization Device Expected Uncertainty (mean setup

error)Belly board 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 UncertaintyDisclaimer: Sanford’s Summary

Anatomic Site Expected Uncertainty

Intracranial 1.0 (most rigid) - 3.5 (least rigid) mmHead and Neck ~3 mm (base of skull)

~8 mm (low neck)Spine 2 – 4 mm Lung 5 – 9 mm Lung - SBRT 2.5-5 mm

Breast ~4 mm systematic, 4.4 mm randomAbdomen 4.5-7 mmProstate 4.5-6.5 mm (7.5 for svs)Prone Pelvis ~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 UncertaintyDisclaimer: Sanford’s Summary

Anatomic Site Expected Uncertainty (Difference pre/post)

Intracranial ~1.0 mm (mask systems)Head and Neck ~1.5 mm

Spine ~1.5 (supine), ~2.5 (prone) mm – median at 15 minutesLung ~2.5 mm post treatment, ~ 6 mm respiratory motion

(i.e. expect 2.5 mm with resp. management, worse without)Breast ~2 mm for external surface and chest wall (using thermoplast

overlay)Abdomen Median respiratory amplitude is 16 mm. 5-8 mm with

abdominal compressionProstate ~2 mm median at 15 min, reduced to < 1.5 mm with ERBProne Pelvis ~2.5 mm median at 15 min (prostate)

Repeated use of IGRT or use of tracking systems may reduce these uncertainties.

Thank You

immobilization from rigid to non-rigid

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