Comparison of Interfacility Implementation of Essential SBRT Components Keith Neiderer B.S. CMD RT(T) VCU Health System
Disclosures None
Objectives Review essential components that characterize SBRT Compare and Contrast different institutional philosophies in regards to the SBRT planning and treatment process Provide information for attendee to form their own opinion on an optimal model for a SBRT program
SBRT Components Secure Immobilization Proper Accounting of Internal tumor and organ motion Accurate repositioning Creation of highly conformal dose distributions Registration of patient s anatomy, created dosimetry, and treatment delivery to a 3D coordinate system referenced to fiducials Biologically potent dose prescriptions
Secure Immobilization Body Conformal Bags - Vacuum-Lock Bags (+/- Wingboard) - Alpha Cradles
Secure Immobilization SBRT Body Frames
Accounting for Internal Tumor and Organ Motion Free Breathing ITV based Planning (encompassing entire range of tumor motion) Gating (Targeting a phase of the breathing cycle) Breath Hold Targeting either inhalation or exhalation Tumor Tracking
Accounting for Internal Tumor and Organ Motion ITV Based Planning - contour on MIP (maximum intensity projection) Maximum Intensity Projection Maximum Expiration Maximum Inspiration
Accounting for Internal Tumor and Organ Motion ITV Based Planning -create ITV based on contours from all 10 Phases
Accounting for Internal Tumor and Organ Motion Respiratory Gating
Accounting for Internal Tumor and Organ Motion Breath Hold Voluntary AV Biofeedback ABC (active breathing control)
Accurate Repositioning Indexing of Immobilization devices to patients and couch Imaging CBCT kv OBI Pretreatment Isocenter localization and correct patient position Intrafraction To correct for any patient movement if necessary
Creation of Conformal Dose Distributions
Creation of Conformal Dose Distributions 3D Conformal Coplanar / Noncoplanar No parallel opposing beams Block margins 0 margin Negative margin Inhomogeneous distribution 3 7 mm margin Forward Planning Conformality and Normal Tissue Sparring Beam angles chosen Manual optimization of beam weights Adjustment of MLC positions
Creation of Conformal Dose Distributions IMRT / VMAT IMRT Parameters Interplay effects between MLC and target motion 1 3 Segments per beam (minimal modulation) Minimum segment size 2cm x 2cm Optimization Parameters Inhomogeneous Distribution No max dose constraint for target Conformality Use rings to keep distribution tight and create steep dose gradients
Potent Dose Prescriptions SBRT in early stage NSCLC achieving a BED of > 100 Gy leads to improved survival 20 Gy x 3 18 Gy x 3 12 Gy x 5 12 Gy x 4 10 Gy x 5 7.5 Gy x 8 180 Gy 151.2 Gy 132 Gy 105.6 Gy 100 Gy 105 Gy Onishi et al, Cancer, 2004
Site A Academic Institution Simulation Physicist is present at time of simulation Immobilization Vac-loc Bag Abdominal Compression Plate Plate is compressed to position of uncomfort, then dialed back slightly
Site A Accounting for Motion 4DCT Scan ITV planning AVG Scan for dose calculation and normal tissue contouring MIP (0 90%) for ITV delineation
Site A Accurate Repositioning Patient is indexed to table using compression frame with paddle just inferior to sternal notch Pretreatment CBCT to verify patient positioning and isocenter localization No intrafraction imaging Potent Dose Prescriptions 18 Gy x 3 Fxs 10 Gy x 5 Fxs 5 Gy x 10 Fxs (for retreats) Treat patient every day
Site A Conformal Dose Distributions 10 13 beam noncoplanar arrangement Approximately 5 of the 13 beams would be noncoplanar Block Margin 0 margin in Ant, Post, Lt and Rt directions 2mm 5mm margin Sup and Inf Optimization No modulation of dose within field Isodose Optimization Number of beams, beam location, beam weight Manual manipulation of MLC to help with conformality and normal tissue sparring
Site A Patient 1: RUL Lung
Site A Patient 1: RUL Lung
Site A Patient 2: RLL Lung
Site A Patient 2: RLL Lung
Site A Patient 3: LUL Lung
Site A Patient 3: LUL Lung
Site B Dedicated Stereotactic Center Simulation Physicist is present at time of simulation Immobilization and 4DCBCT are done on treatment machine Vac-loc Bag Patient is given an anti-anxiety medication to help stay relaxed for both simulation and treatment Simulation on the treatment machine allows for testing of gantry and couch angles if necessary Patient is then taken to Radiology where a diagnostic CT is done in the treatment position for planning purposes
Site B Accounting for motion 4DCBCT ITV planning Diagnostic CT used for dose calculation and normal tissue contouring ITV delineation from 4DCBCT MIP Potent Dose Prescription 10 Gy x 5 15 Gy x 4 Patients treat once a week
Site B Accurate Repositioning Vacloc bag is indexed to table Patient is scheduled for a verification day Setup in Treatment position KV imaging orthogonals CBCT Test parameters for treatment fields On treatment day Pretreatment kv and CBCT Repeat CBCT half way through treatment
Site B Conformal Dose Distributions 20 or more noncoplanar arrangement Approximately half of the beams would be noncoplanar No heterogeneity corrections Block Margin Patient specific based on location and dose objectives Optimization No modulation of dose within field Isodose optimization Number of beams, beam location, beam weight Manual manipulation of MLC to help with conformality and normal tissue sparring
Site B Patient 1: RUL Lung
Site B Patient 1: RUL Lung Only 4 couch angles ~ 45 min treatment slot
Site B Patient 1: RUL Lung
Site B Patient 2: RLL Lung
Site B Patient 2: RLL Lung
Site B Patient 3: LUL Lung
Site B Patient 3: LUL Lung
Site B Heterogeneity Corrections On / Off
Site B Heterogeneity Corrections On / Off
Site C Academic Institution Simulation Physicist is not present at time of simulation Immobilization Vac-loc Bag with wing board
Site C Accounting for Motion 4DCT and Free Breathing Motion evaluation 0 0.5cm motion use free breathing scan 0.5 1.5cm motion ITV Planning (AVG and MIP) > 1.5cm motion rescan using breath hold (ABC) or
Site C Accurate Repositioning Wing board and vac-loc bag are indexed to the couch Pretreatment imaging kv OBI orthogonal images bony alignment CBCT soft tissue alignment Intrafraction imaging CBCT soft tissue alignment (midway through tx) Potent Dose Prescriptions 12 Gy x 4 Fx 18 Gy x 3 Fxs Patients treated every other day or twice a week depending on physician
Site C Conformal Dose Distributions 8 10 coplanar IMRT beams No parallel opposing beams IMRT Parameters 1 3 segments per beam Minimum segment size of 2cm x 2cm Optimization Parameters Inhomogeneous Distribution Max dose constraint = prescription dose / 0.8 Conformality Use rings to keep distribution tight and create steep dose gradients
Site C Patient 1: RUL Lung
Site C Patient 1: RUL Lung
Site C Patient 2: RLL Lung
Site C Patient 2: RLL Lung
Site C Patient 3: LUL Lung
Site C Patient 3: LUL Lung
Site D Academic Institution Simulation Physicist is present at time of simulation Immobilization Vac-loc Bag Alphacradle Potent Dose Prescriptions 18 Gy x 3 Fxs 12.5 x 4 Fxs 7.5 Gy x 8 Fxs
Site D Accounting for Motion Free Breathing, 4DCT, Breath Hold (if feasible) Motion Evaluation ITV Planning Avg dose calculation and normal tissue contouring MIP ITV delineation Consider Gating if motion is greater than 1cm Breath Hold
Site D Accurate Repositioning Vac-loc bag indexed to couch Pretreatment imaging kv OBI orthogonal images apply shifts CBCT apply shifts Retake CBCT if shift is greater than 1mm in any direction Verify motion with kv fluoro imaging Intrafraction imaging Cine images are taken for each field to monitor motion Not all fields will reveal tumor motion CBCT
Site D Conformal Dose Distributions 7 to 9 coplanar beams Block Margin 5mm margin in Ant, Post, Lt, and Rt directions 7mm margin Sup and Inf Optimization Wedges Manual manipulation of MLC and Jaws to help with conformality and normal tissue sparring
Site D Patient 2: RLL Lung
Site D Patient 2: RLL Lung
VMAT Patient 1: RUL Lung
VMAT Patient 1: RUL Lung
VMAT Patient 2: RLL Lung
VMAT Patient 2: RLL Lung
VMAT Patient 3: LUL Lung
VMAT Patient 3: LUL Lung
Patient 1: RUL Lung Conformity Index (CI) <1.2 R50 for 39cc PTV 4.3 minor 5.3 RTOG 0813
Patient 1: RUL Lung Lung DVH
Patient 1: RUL Lung Chestwall DVH
Patient 2: RLL Lung Conformity Index (CI) <1.2 R50 for 35cc PTV 4.3 minor 5.3 RTOG 0813
Patient 2: RLL Lung Lung DVH
Patient 2: RLL Lung Chestwall DVH
Patient 3: LUL Lung Conformity Index (CI) <1.2 R50 for 22cc PTV 4.5 minor 5.5 RTOG 0813
Patient 3: LUL Lung Lung DVH
Patient 3: LUL Lung Chestwall DVH
Summary You Tell me, how would you do it?
Acknowledgements VCU Health System Geoff Hugo, PhD Josh Evans, PhD Duke University Health System Rodney Hood, CMD Lei Ren, PhD Chesapeake Regional, Riverside and University of Virginia Radiosurgery Center K. Martin Richardson, MS Kelly Spencer, MS Wake Forest Baptist Health Jim Ververs, PhD Alton Fleming, BS, CMD William Andy Dezarn, PhD William H. Hinson, PhD University of Virginia Health System David Schlesinger, PhD
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