10 9 8 6 IMRT with static MLC 5 4 3 - SASRO · Elekta ABC ABC=Active Breathing Coordinator...

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Institut für Radiotherapie

-5cm -4 -3 -2 -1 0 +1 +2 +3 +4 +5cm

10

9

8

7

6

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1

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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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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500

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cGy

010203040 0 10 20 30 40

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1000

2000

3000

4000

5000

6000

cGy

01020304050 0 10 20 30 40 50

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„Outer“ vs. „inner“ target motion

Breast cancer Lung cancer

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4

4

• Movements not known

• Target outside treatment field

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2

3

3

5

5Exspiration

1 Inspiration

2

2

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Static CT with untriggered treatment

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4

4

1

2

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3

5

5Exspiration

1 Inspiration

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• Target definition is all-inclusive

4D-CT with triggered treatment

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2

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3

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5

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

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10 9 8 6 IMRT with static MLC 5 4 3 - SASRO · Elekta ABC ABC=Active Breathing Coordinator...

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