© copyright UEAmhf@cmp.uea.ac.uk Image Guided Radiation Therapy Dr. Mark Fisher School of Computing...

Image Guided Radiation Therapy

Dr. Mark FisherSchool of Computing SciencesUEA Norwich UK

• Introduction/Motivation• Background• State of the Art• Current Research• Conclusions

Introduction/Motivation

Introduction

• Cancer is currently the cause of 12% of all deaths world wide; 10 million new cases diagnosed annually.

• Within the European union over 1,5 million new cancer cases are diagnosed every year and over 920000 people die of cancer.

• Most scientists are confident that in the long term significant improvement in cancer cure will come from systematic treatments such as immunotherapy and/or gene therapy and drug targeting.

• For the time being the surgical removal of the tumour tissue followed by radiotherapy remains the main method of treatment.

Source: MAESTRO 2004

New cases and deaths from cancer - US 2004

Site % New Cases Est. Deaths

Digestive System 19% 134,840

Prostate 17% 29,900

Breast 16% 40,580

Respiratory System 14% 165,130

Source: American Cancer Society, 2005

Radiation treatment equipment per million population

Background

Ionising Electromagnetic Radiation interacts with cells destroying their DNA

None-malignant cells can repair themselves but high doses of radiation to healthy tissue can

induce secondary malignancies.

Both malignant and non-malignant tissue is destroyed

BUT...

Aim of Radiotherapy Treatment I

• To deliver a high dose of Radiation to the tumour whileand a low dose to healthy tissue and organs at risk.– Possible through the use of multiple treatment fields (beams).

Radiation Therapy Treatment Delivery

Wilhelm Conrad Roentgen saw the bones of his own hand when held between cathode tube and fluorescent screen.

The Coolidge Tube. William Coolidge of GE with his "hot" cathode tube,The Coolidge tubes also made possible the development of orthovoltage kV X-ray therapy.

Varian brothers develop first klystrontube, initially used in Radar

Mullard (Philips) 4 MV double gantry linac. First installed at Newcastle Hospital, This unit featured a nearly isocentric mount, a 1 meter traveling wavetube, MV magnetron, and a false floor.

Varian Clinac treatment unit, Today's integrated medical linac has been enhanced by computerized controls and easier operation in the quest for optimal treatment in cancer.

Radiation Therapy Treatment Planning

• In the early days of radiotherapy, the X-ray beams were rectangular or square in shape and were directed at the tumor from two to four different angles.– Since the dosages delivered were uniform in strength there was

some damage to healthy tissue.

• In the 1970’s conformal RT was developed. This approach used lead-alloy blocks to shape the beam.– The dose was ‘conformed’ to the shape of the tumour, healthy

tissue is spared.

ICRU 50/62

ICRU 50 (1993) and ICRU 62 (1999)define relationships and marginsbetween treatment volumes

Report of BIR working party (2003),established in 1999 followinginitial work by Euen Thompson, NNH

State-of-the-Art

Intensity Modulated Radiotherapy Treatment

(IMRT)Conceptualised in 1980’s

Uses Multi-leaf collimator to vary the dose density within the treatment volume.

Allows for much higher dose delivery to malignant tissue.

Needs higher precision volumetric planning systems

Currently the most widely deployed method in clinical use.

Beam shaping using MLC

• treatment planning software with inverse treatment planning capability

Total Cost approx. £3M each system

To treat each patient

• a medical linac with a multi-leaf collimator ($1.6M)

• simulation devices and software for establishing patient positioning as well as pre-testing and refining treatment plans

Comparisons between IMRT and 3D-CRT Treatment Costs

mhf@cmp.uea.ac.uk© copyright UEASource: Alison Vinall, HHUH

Source: NNUH

Data Acquisition

mhf@cmp.uea.ac.uk© copyright UEA

Treatment Planning

Computer Planning

Plan Simulation/Verification

Five field IMRT beam arrangement for treating prostate

Treatment Delivery

Treatment is delivered over 30-40 fractions

Patient makes several visits to hospital over a period of weeks

Accounting For Organ Movement

• “Most of the development of IMRT has taken place assuming that the organs don't move from fraction to fraction and are well represented by their positions determined from some pre-planning 3D imaging study, be it x-ray CT, MR or functional imaging. As the ability to conform to the target has now reached near perfection, attention is now turning to not accepting this limitation and attempting to quantitate organ movement and account for it in IMRT planning and delivery”.

• “IMRT of the moving patient is like completing a jigsaw on a jelly”

Prof. Steve Webb, Royal Marsden Hosp.

Types of Motion

• Patient set-up errors– Position-related organ motion which can be minimised if the

patient's planning scan is performed while the patient is immobilised and in the treatment position.

• Inter-fraction motion– i.e. motion that occurs when the target volume changes from

day to day. This is a problem for organs that are close to or part of the digestive/excretory system. This work is collated under various headings: gynaecological tumours, prostate (the largest group), bladder and rectum.

• Intra-fraction– generally due to respiratory and cardiac functions which disturb

other organs. This work is collated under headings: liver, diaphragm, kidneys, pancreas, lung tumours and prostate.

Patient Set-up Errors

Stereotactic surgeryuses mechanical fixationsimplanted in the skullto ensure alignment.

Gold markers may be implantedin soft tissue

Passive infra-red reflective marker block used to track chest wall motion during data acquisition, simulation, and treatment.

Intra-Fraction Motion: Current Approaches

Varian RPM respiratory gating

Gated 4D CT

Beam’s Eye Views of gated and non-gated treatment volumes

Gated 4-D CT Movie showing Lung Motion

MotionView™: addresses intra-fraction deformation

This offers particular advantages for targeting lung tumors which move and deform during respiration.

Flat panel Amorphous Silicon Detector

• Traditionally, imaging technology has been used to produce three-dimensional scans of the patient’s anatomy to identify the exact location of the cancer tumor prior to treatment.

• However, difficulty arises when trying to administer the radiation, since cancer tumors are constantly moving within the body • IGRT combines a new form of scanning technology, which allows planar or X-ray Volume Imaging (XVI), with IMRT. This enables physicians to adjust the radiation beam based on the position of the target tumor and critical organs, while the patient is in the treatment position.

Inter-fraction Motion: Current Approaches

Image Guided Radiation Therapy (IGRT)

Elekta Synergy™

Source: Elekta

Elekta Synergy™

Synergy allows for co-registration of Cone-Beam CT and RTP data in real-time immediately before treatment delivery

“For the first time the cone beam system lets us see what we want to hit with our treatment by giving us a continuous set of detailed 3-D X-ray images of the patient when the patient is lyingdown on the treatment couch. This means we can even move towards better cure rates by safely increasing the doses we deliver in radiotherapy.”(Professor Chris Moore, Consultant Physicist, Christie Hospital)

Available from August 2004

Current Research

“The future is motion” - Varian annual report 2003

Even when patients are placed in precisely the same position fortheir daily treatments, some tumors can shift by as much as twoto three centimeters over six to eight weeks of therapy. Inaddition, normal physiological processes like breathing causesome organs and tumors to move significantly during a dailytreatment session.

As we understand more about tumormotion, we have had to realize that we cannot position patientsjust on the basis of marks or tattoos on their external anatomy. Asthe treatments have become more conformal, and as we try toconfine the high dose area much more strictly just to where thetumor is, we have to be all the more diligent in knowing exactlywhere the tumor is, every day.

MAESTRO WP1.3 - Dynamic RT

• Objective– To compensate for intra-fraction organ motion by dynamically

shaping the beam in real-time (UEA + UCLM).

Currently researchers are able to track implanted gold markers

Portal Video: Respiratory Motion

WP1.3 Aims to infer motion without using markers

Ultimately we hope to simulateDynamic MLC Control

ASM: Motion Tracking

Building & Fitting ASM Models

Image Registration via Graph Matching

Conclusions

• Several Studies have shown IMRT improves quality of RT– IMRT showed a 92 percent three-year survival rate for early stage

prostate patients and a better than 80 percent three-year survival rate for those with an initially unfavorable prognosis.

• Set-up error and organ motion interferes with the accuracy of radiotherapy,– The important goal of shrinking the treatment margin can only

be achieved with better patient positioning techniques.

• Improvements in electronic portal image devices are needed before widespread use of Dynamic Image Guided RT is possible– WP1.3 should demonstrate it is feasible in a limited number of

cases• e.g Lung

Acknowledgements

• Alison Vinall - Head of Radiotherapy Physics, NNUH• Dr. Yu Su, Computing Sciences, UEA• Yanong Zhu, Computing Sciences UEA• Muhannad Al-Hasan, Computing Sciences, UEA• MAESTRO

© copyright UEAmhf@cmp.uea.ac.uk Image Guided Radiation Therapy Dr. Mark Fisher School of Computing...

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