10 9 8 6 imrt with static mlc 5 4 3 - sasro · elekta abc abc=active breathing coordinator...
TRANSCRIPT
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-5cm -4 -3 -2 -1 0 +1 +2 +3 +4 +5cm
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Leaf A Leaf B
IMRT with static MLC
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Time
Time
Dose
DistanceMax. Speed
IMRT with dynamic MLC
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Segmental Approach: static MLC “step and shoot,” “stop and shoot”
� Radiate a segment� Radiation pauses � Leaves move to the next position � Radiate next segment� Radiation pauses …...
� Radiation is not on when the leaves are moving
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Institut für Radiotherapie
Dynamic approach: dynamic-MLC (DMLC)„sliding window“ or „moving gap“
Radiation is on when the leaves are moving
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Volumetric Arc Therapy: a new approach
� Simple trajectory – single 360ºgantry rotation
� Use full field “cone beam”� Dose calculation ~ every 1
degree� Constraints
� MLC motion - max. 5 mm/ deg
� Dose rate maximum
� Dose rate variation
� Intensity modulated ArcTherapy IMAT/Volumetricmodulated arc therapy VMAT
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Volumetric Modulated ARC Therapy: VMAT
� Single gantry rotation ARC treatment
� Cone beam treatment delivery
� Full intensity modulation during ARC
� Dose per gantry angle varies during the treatment
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VMAT Dose application
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VMAT: a fast delivery approach
� Delivery time < 2 minutes � Fully dynamic (beam is always “on”)� Minimal MU� Use maximum dose rate and leaf speed� Large volume of coverage� Requires no carriage moves
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Volumetric Arc
Comparison VMAT vs. multiple field IMRT:Prostate
Fixed Gantry IMRT
Courtesy Dr. K. Otto and
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Volumetric Arc
Comparison VMAT vs. multiple field IMRT:H&N
Fixed Gantry IMRT
Courtesy Dr. K. Otto and
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Respiration controlled delivery
� Increasing interest in respiration related organ mo tion and its management for the radiotherapy of cancer i n the thoracic region
� Patient movement may lead to overdosage of normal tissue or tumor underdosage
� Up to 3 cm of target motion in the thoracic region of the body
� Geographical misses will reduce the probability of cure and will increase the danger of radiation complicat ions
� Today: PTV for mobile or moving tumors is determine d with large margins
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How to protect the heart?
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4D-CT and heart movements
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Gated vs. Non-Gated Breast Cancer Treatment
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Gated vs. Non-Gated Breast Cancer Treatment
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Maximum doses to the anterior heart wall
� Mean dose to anterior heart wall� Non gated: 2.4 Gy� Gated: 1.2 Gy p=0.000
� Mean maximal dose to anterior heart wall� Non gated: 39.6 Gy� Gated: 10.1 Gy p=0.000
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cGy
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„Outer“ vs. „inner“ target motion
Breast cancer Lung cancer
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• Movements not known
• Target outside treatment field
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5Exspiration
1 Inspiration
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Static CT with untriggered treatment
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5Exspiration
1 Inspiration
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• Target definition is all-inclusive
4D-CT with triggered treatment
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5Exspiration
Inspiration1
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• Maximum coverage of the target• Optimized sparing of surrounding tissues
4D-CT with triggered treatment
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Varian RPM Gating
� Video camera based� Infrared is reflected� Detector box movement is
recorded� Audio- and/or Videocoaching� Free breathing or end
inspiration breath-hold� Videocoaching via LCD-Monitor,
LCD-Brille, Spiegel oderPrismen
� Instantaneous triggering of Varian Clinac’s: dephasing of injected electrons
Infrared diodes
Detector box
3 cm
Video camera
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Elekta ABC
� ABC=Active Breathing Coordinator
� Spirometric approach
� Spirometer actively blockes in deepinspiration
� Videocoaching (mirror image of an in-room monitor)
� Patient indirektly controls treatmentstart using a hand switch (Linaccontrol with predefined threshold valueor manually by operating personel)
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Siemens PMU Belt
� Measurement of the thorax movement
� Active triggering of CT
� Triggering of Linac
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Accuray Synchrony
� Dedicated system for Cyberknife
� Measurement of thoraxexcursion
� No gating but controlledmovements of the robot: tracking
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Brainlab ExacTrac Adaptive Gating
� Setup control with two orthogonal X-ray images
� Image verification with fluoroscopyduring treatment
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Verification: Basics
� Problem: verification of patient position relative to the
therapy field
� First approach: Portal films, i.e. film verificatio n of
treatment fields
� Limitation: Analogue Off-Line Process
� Image guided radiotherapy: Imaging modalities avail able
on the treatment couch i.e. in treatment position
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Historical background I
Portal imaging� Portal films
� Offline-Tool� Comparison using analogue ruler measurements (=> error
source)� Electronic Portal imaging devices (EPID)
� Online-Tool� Electronic Matching
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kV Radiography- and Fluoroscopy-Systems� Room basesd
� Shirato, 1999� Image intensifiers with CCD-cameras
� Gantry based� Takai, 2002� aSi-Panel (15x15 cm2)
Historical background II
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Cone beam CT at a Linac� kV-Approach
� Jaffray, 2002� US-Patent (11. Jan. 2005)
� MV-Approach� Poliot, 2003
� Ford, 2002� => Siemens Linac
Historical background III
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Special approaches� MD-Anderson
� combination of a CT on rails and a Linac in the same room
� one treatment couch
� Uematsu, 2002� Linac, Simulator and CT with
one single couch
Historical background IV
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� Different modalities
� Portal imaging: Digital x-ray (MV)
� Radiographic mode: Digital x-ray (kV)
� Fluoroscopic mode: Live fluoroscopy (kV)
� Cone-Beam-CT mode: Computed tomography (kV or MV)
� Aims
� Patient repositioning
� Tumor monitoring
� Adaptive radiotherapy (ART)
Modern Linacs with IGRT
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Commercially available IGRT technologies
1. Varian OBI
2. Elekta Synergy
3. Siemens Primatom/(Artiste)
4. Brainlab Exac Trac X-Ray
5. Tomotherapy Hi-ART
6. Accuray Cyberknife
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Varian Clinac IX/Trilogy
� PVI-System: PV aS1000
� Clinac plus OBI (on-board-imager)
� Trilogy with stereotactic Kit
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Elekta Synergy
� PVI: iVIEW GT
� Base: Precise Linac
� Synergy S withstereotactic kit
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Siemens Primatom/(Artiste)
� PVI-System: Beamview TI
� Siemens Somatom CT plus Primus Linac
� Announced at ASTRO 2004: Artiste => IGRT-solutionwith inline kV-System
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Brainlab ExacTrac X-Ray
� 2 Gantry-independent digital x-ray systems
� 2-axis couchtop upgrade => 6-axis couch