Advances in radiation Objectives oncology and QM in RT practice · 2019-05-29 · Advances in radiation oncology and QM in RT practice • To become familiar with different radiation

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


20 �

Treatment Couch

86.60 cm

Chamber holder



100 cm


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


23�


23


24�


Modulate beam from -  MLC movement -  Dose rate variation -  Gantry speed variation

222222222224444444444444


25�


•  SRS/SRT: intracranial •  SBRT: extracranial

–  Small PTV –  Large dose/fraction –  Less fraction number

222222222222225


26 �

Treatment Couch

86.60 cm

Chamber holder



100 cm


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)


Cervix cancer with effect of bladder & rectum filling

Chan, Dinniwell, et al,


Pt Weight Loss


Tumor shrinkage

•  14 cervical cancer patients •  MRI prior to RT and after 30 Gy •  GTV decreased (on average) by 46%


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


39 �

Treatment Couch

86.60 cm

Chamber holder



100 cm


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

Documents

Advances in radiation Objectives oncology and QM in RT practice · 2019-05-29 · Advances in radiation oncology and QM in RT practice • To become familiar with different radiation