Taweap Sanghangthum, PhD
Department of Radiology, Faculty of Medicine
Chulalongkorn University�
Advances in radiation oncology and QM
in RT practice • To become familiar with different radiation
types used for external beam radiotherapy • To understand the basic principle of
teletherapy machines and support equipment used for EBT delivery
• To describe the methods of brachytherapy • To briefly explain the QM in radiotherapy
Objectives
• One of the main treatment modalities for cancer (often in combination with chemotherapy and surgery)
• Minor role in other diseases
Aim of Radiotherapy
Radiotherapy
Teletherapy S. far from TM
Brachytherapy S. near by TM
Simulation� Tx Planning� Tx Delivery�Tx Field Veri.�Planning Veri.�
5 �
Treatment Couch
86.60 cm
Chamber holder
2.85 cm inherent buildup (equivalent to 3.28g/cm 2)
Acrylic insertionDiode detector
100 cm
External Beam Radiotherapy Process
Diagnostic X-ray tube
Imager
Radiation beam defining system
Simulator exact couch Rotating couch
Rotating gantry
1. Conventional Simulator
Limitation 2D image
1. Conventional Simulator
A CT-simulator consists of a CT-scanner with a flat table top, laser patient positioning and marking system, CT-simulation software, and hardcopy output.
2. CT Simulator
Special design of CT scanner
• Large aperture • Flat couch top • External lasers • Virtual simulation
software
Virtual Simulation
CT image is the gold standard for treatment planning - Electron density information - standard dose calculation - Good bone definition - Accurate geometry - Improved target definition for some cases (e.g.lung) - Established motion management technique (4DCT) - Fast scan & low cost (compared with MRI)
CT-Sim Advantages Limitation of CT
Brain stem? Lesion?
Brain tumor
3. MRI simulator • Excellent soft tissue contrast
- accurate target definition
• Use of non-ionizing radiation
Advantages of a MRI-based treatment process
(many sequences selection)
• GE Signa HDxt 1.5T with oncology package Open Bore
3. MRI simulator
Consideration
• MRI bore size - image patient in treatment position with immobilization devices
• MRI-compatible immobilization devices
• Flat couch top similar to treatment couch
• Image distortions
• No electron density relationship
MRI-based patient simulation
CT/MR Registration
CT • Good bone definition • Standard for Dose Calulation • Accurate geometry
MR • Good lesion definition • Nerves and misc. info • No density Information • Distorsion Issues
= +
Good for plan
4. PET-CT simulator
imaging of glucose metabolism using 18F-FDG as a radiopharmaceutical
HipFix System
• Used to reduce the patient setup uncertainty
Immobilization
Simulation� Tx Planning� Tx Delivery�Tx Field Veri.�Planning Veri.�
20 �
Treatment Couch
86.60 cm
Chamber holder
2.85 cm inherent buildup (equivalent to 3.28g/cm 2)
Acrylic insertionDiode detector
100 cm
External Beam Radiotherapy Process
Treatment & Planning Techniques�
• 2D (conventional radiotherapy) • 3D-CRT (conformal radiation therapy) • Advanced Technique
– IMRT (Intensity Modulated Radiation Therapy) – VMAT (Volumetric Modulated Arc Therapy) – SRS/SRT and SBRT�
- 3D-CRT - IMRT - VMAT - SRS/SRT, SBRT
22�
Treatment Techniques
- 3D-CRT - IMRT - VMAT - SRS/SRT, SBRT
23�
Treatment Techniques
23
- 3D-CRT - IMRT - VMAT - SRS/SRT, SBRT
24�
Treatment Techniques
Modulate beam from - MLC movement - Dose rate variation - Gantry speed variation
222222222224444444444444
- 3D-CRT - IMRT - VMAT - SRS/SRT, SBRT
25�
Treatment Techniques
• SRS/SRT: intracranial • SBRT: extracranial
– Small PTV – Large dose/fraction – Less fraction number
222222222222225
Simulation� Tx Planning� Tx Delivery�Tx Field Veri.�Planning Veri.�
26 �
Treatment Couch
86.60 cm
Chamber holder
2.85 cm inherent buildup (equivalent to 3.28g/cm 2)
Acrylic insertionDiode detector
100 cm
External Beam Radiotherapy Process
Patient simulation: CT, MR…
Planning treatment -Determination of interest
volumes: GTV, CTV, PTV, OR -Conformation-beams
Treatment
Differences in target position
Simulation to Treatment�
• How can we know the position of the target?
IGRT is the use of the image in the actual treatment room as a tool for tracing and verification of the tumor
volume immediately before or during treatment.
■ What is IGRT for field verification?
IGRT
Image-guided Radiation Therapy �
Complex region & High dose gradients
Why do we need IGRT? �
Daily set up variation
DRR (Ref) IGRT (kV)
Why do we need IGRT? �
Cervix cancer with effect of bladder & rectum filling
Chan, Dinniwell, et al,
Why do we need IGRT? �
Pt Weight Loss
Why do we need IGRT? �
Tumor shrinkage
• 14 cervical cancer patients • MRI prior to RT and after 30 Gy • GTV decreased (on average) by 46%
Why do we need IGRT? �
EPID real-time
verification
The technology can identify patient positioning errors so corrective action can be taken before the dose of radiation is delivered.
- Based on bony landmarks - 1 isocenter
2D MV; Electronic Portal Imaging Device �
Floor-mounted system
Gantry-mounted system (OBI)
2D Orthogonal kV X-rays �
Ceiling-mounted system
CBCT Varian CBCT
Elekta SynergyTM VolumeView
Cone-Beam Computed Tomography (CBCT) �
ViewRay system (3Co sources + 0.35T MR scanner)
FDA approved �
90s ViewRay MR kV-CBCT
Inroom-MRI
- 6 MV PET-linac - BgRT - Release ASTRO 2018
refleXion
PET-Linac�
PET-Linac
Simulation� Tx Planning� Tx Delivery�Tx Field Veri.�Planning Veri.�
39 �
Treatment Couch
86.60 cm
Chamber holder
2.85 cm inherent buildup (equivalent to 3.28g/cm 2)
Acrylic insertionDiode detector
100 cm
External Beam Radiotherapy Process
The most common RT machines are
- Co-60 - Linear accelerator
External Treatment Therapy Machines
1. Source head�2. Collimator�3. Gantry�4. Couch�
High specific activity and exposure rate constant
Cobalt-60 machine
Radioactive source
• The 60Co source is produced by irradiating ordinary stable 59Co with neutrons in a reactor
• The nuclear reaction can be represented by
59Co (ηη,γ) 60Co
Cobalt-60 machine
Cobalt-60 decay Cobalt-60 machine
The linac is a device that used high-frequency electromagnetic waves to accelerate charged particles (electron) to high energies through accelerator tube
Linear Accelerator Machine
Linac Electron
For superficial TM X-rays
For deep TM
4-25 MeV 4-18 MV
6 & 10 MV photon
10-22 MeV electron
Percentage Depth Dose Comparison Dose Distribution
Photon Electron
Standard Linac�Varian Elekta Siemens
• FFF mode for SRS/SRT, SBRT
Special Design Linac�
• FFF mode for SRS/SRT, SBRT
• 6 MV beams • 2 orthogonal x-rays
CyberKnife
Special Design Linac�
• FFF • Conventional tx.
• 6 MV beams • 3.5 MV-CBCT
Tomotherapy
• Relatively low entrance dose (plateau)
• Maximum dose at depth (Bragg peak)
• Rapid distal dose fall-off (has finite range)
Particle Beam Radiotherapy
187 MeV
Proton or carbon depth dose distribution
Chulalongkorn Hospital Proton Treatment Process
100%
60%
10% PROTONS
PHOTONS �dose bath�
Medulloblastoma
Image from Greco C. Current Status of Radiotherapy With Proton and Light Ion Beams. American CANCER society April 1, 2007 / Volume 109 / Number 7
• The dose to 90% of the cochlea was reduced from 101% with standard photons, to 33% with IMRT, and to 2% with protons
cochlea
Insert applicator�
X-ray with dummy�
QA source position�
Loading source�
Tx planning�
Brachytherapy Process Brachytherapy Types
Short half life with low energy:
- I-125 (60 days; 28 keV)
- Pd-103 (17 days; 21 keV)
Temporary Implants
Ra-226, Cs-137, Co-60, Ir-192
Permanent Implants
Long half life with high energy
Ir-192 source
γ-rays
energy 0.38 MeV
T1/2 = 74.2 days
Small tumor - primary - after teletherapy
Not too close to vital structure
Brachytherapy Machine
Most common brachytherapy - cervix cancer
Intracavitary
Surface Mould Implantation
63�
Linac QA AAPM TG142 - Daily - Monthly - Annually
• Dosimetry • Safety • Mechanical
64 �
3.4 QA program for teletherapy machines
Procedure Limit
Mechanical Non-IMRT IMRT SRS/SRT
- Laser localization 2 mm 1.5 mm 1 mm
- ODI 2 mm
- F.S. indicator 2 mm 2 mm 1 mm
Daily
65 �
QA program for teletherapy machines
Daily Linac condition
66�
Daily Linac QA
- Door interlock
- Audiovisual monitor
- Beam on indicator
Safety
67 �
Procedure Limit
Dosimetry
- Output constancy (x-ray/electron) 2%
- Typical dose rate OP constancy 2%
Monthly Linac QA
FC 65P in plastic phantom at 10 cm depth for photon; T&P correction
68
FC 65P in plastic phantom at 2 cm depth for photon; T&P correction
69 70
Monthly OP constantly check
71 �
Procedure Limit
Mechanical - ODI with front pointer 1 mm - Gantry/Collimator angle indicators 1o
- Jaw position indicator (Symmetric) 2 mm - Jaw position indicator (Asymmetric) 1 mm - Cross-hair centering (Walkout) 1 mm - Wedge placement accuracy 2 mm
Monthly Linac QA
72 �
Distance indicator
Laser
Cross-hair
Monthly Linac QA
Laser alignment �
Tolerance : ± 2 mm diameter�
Result : accept not accept �
Action : not adjust adjust �
Monthly Linac QA
74 �
Procedure Limit
Mechanical
Crosswire rotation 1 mm diameter
Monthly Linac QA
75 �
Gantry angle indicator
Use digital level � read on monitor
Collimator angle indicator
Monthly Linac QA
76 �
Couch position indicator
• Move couch W known value • Then, read value from monitor
Monthly Linac QA
77 �
F.S. indicator Various F.S. - Symmetry - Asymmetry
Field Size (cm2) X (cm) Y (cm)
5x5
10x10
28x28 �
Monthly Linac QA
78 �
Light/Rad field coincidence
Monthly Linac QA
79 �
Procedure Limit
Safety - Laser guard-interlock test Functional
Monthly Linac QA
80 �
kV-MV isocenter
80
MV image
kV image
Monthly Linac QA
kV-MV isocenter
Monthly Linac QA
82 �
Radiation isocenter
Winston Lutz test
Monthly Linac QA
83 �
Procedure Limit
Dosimetry
- X-ray flatness change from baseline 1%
- X-ray symmetry change from baseline ±1%
- Electron flatness change from baseline 1%
- Electron symmetry change from baseline ±1%
Annually QA
84 �
� Depth Dose & Profile
- Beam flatness & symmetry
8888888888888884444444444444444444444444
Annually QA
85 �
Annually QA Output Calibration
11.70 ม.�9.80 ม.�
45.9 μSv/hr (behind tree)� 0.25 μSv/hr�
108.1 μSv/hr�
0.18 μSv/hr (ทางเดิน
)�
ทางเดิน iX� 3.1 μSv/hr�
0.15 μSv/hr�
0.32 μSv/hr�
LUDLUM Model 9DP�
Measured Conditions�
- Max FS (40x40 cm2, 45o coll)�
- Highest energy (10FFF)�
- Highest dose rate (2400 MU/min)�
- 30 cm from wall�
- W/O phantom for 1o beam�
- W phantom for 2o beam� ** 104.0 μSv/hr @ 2nd floor**�
15 January, 2016�
External Audit
ESTRO Small fields OF
Annually Output (IROC)
RPC H&N RPC Prostate Output Check every 2 years
(IAEA)
QUATRO
QUality Assurance Team for Radiation Oncology
A peer-review of a radiotherapy service by a team of three experts in RT • radiation oncology (RO) • radiotherapy medical physicist (MP) • radiation therapy technologist (RTT)
ThThank You for Your Attention
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