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Image Guided Radiation Therapy

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Presentation on theme: "Image Guided Radiation Therapy"— Presentation transcript:

1 Image Guided Radiation Therapy
Dr. Mark Fisher School of Computing Sciences UEA Norwich UK © copyright UEA

2 Plan Introduction/Motivation Background State of the Art
Current Research Conclusions © copyright UEA

3 Introduction/Motivation
© copyright UEA

4 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 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 © copyright UEA

5 New cases and deaths from cancer - US 2004
Source: American Cancer Society, 2005 © copyright UEA

6 Radiation treatment equipment per million population
© copyright UEA

7 Background © copyright UEA

8 Background Ionising Electromagnetic Radiation interacts with cells destroying their DNA BUT... 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 © copyright UEA

9 Aim of Radiotherapy Treatment I
To deliver a high dose of Radiation to the tumour while and a low dose to healthy tissue and organs at risk. Possible through the use of multiple treatment fields (beams). © copyright UEA

10 Radiation Therapy Treatment Delivery
1895 Wilhelm Conrad Roentgen saw the bones of his own hand when held between cathode tube and fluorescent screen. © copyright UEA

11 Radiation Therapy Treatment Delivery
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. 1912 © copyright UEA

12 Radiation Therapy Treatment Delivery
1937 Varian brothers develop first klystron tube, initially used in Radar © copyright UEA

13 Radiation Therapy Treatment Delivery
1953 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. © copyright UEA

14 Radiation Therapy Treatment Delivery
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. 1990s © copyright UEA

15 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. © copyright UEA

16 ICRU 50/62 ICRU 50 (1993) and ICRU 62 (1999)
define relationships and margins between treatment volumes Report of BIR working party (2003), established in 1999 following initial work by Euen Thompson, NNH © copyright UEA

17 State-of-the-Art © copyright UEA

18 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. © copyright UEA

19 Beam shaping using MLC © copyright UEA
The radiation beam passes through and is shaped by a device called a multileaf collimator so that it conforms to the shape of the tumor. © copyright UEA

20 To treat each patient a medical linac with a multi-leaf collimator ($1.6M) treatment planning software with inverse treatment planning capability simulation devices and software for establishing patient positioning as well as pre-testing and refining treatment plans Total Cost approx. £3M each system © copyright UEA

21 Comparisons between IMRT and 3D-CRT Treatment Costs
© copyright UEA

22 © copyright UEA Source: Alison Vinall, HHUH

23 Data Acquisition Source: NNUH © copyright UEA

24 Treatment Planning © copyright UEA

25 Computer Planning © copyright UEA

26 Plan Simulation/Verification
© copyright UEA

27 Five field IMRT beam arrangement for treating prostate
© copyright UEA

28 Treatment Delivery Treatment is delivered over 30-40 fractions
Patient makes several visits to hospital over a period of weeks © copyright UEA

29 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. © copyright UEA

30 Types of Motion Patient set-up errors Inter-fraction motion
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. © copyright UEA

31 Patient Set-up Errors Stereotactic surgery uses mechanical fixations
implanted in the skull to ensure alignment. Gold markers may be implanted in soft tissue © copyright UEA

32 Intra-Fraction Motion: Current Approaches
Passive infra-red reflective marker block used to track chest wall motion during data acquisition, simulation, and treatment. © copyright UEA

33 Varian RPM respiratory gating
© copyright UEA

34 Gated 4D CT © copyright UEA
Tumors and organs can move up to 3 cm with respiration, so CT data for planning must target the tumor position at would be during treatment. Traditional CT images show respiratory motion as artifacts. Consequently, target volumes based on these images may end up being distorted and larger than necessary. To account for and to visualize tumor motion, information is needed from a fourth dimension— time. The capabilities of 3D CT are extended through four-dimensional (4D) CT technology, which allows clinicians to view volumetric CT images changing over time. The acquisition of 4D-CT data can be synchronized with a respiratory phase signal, such as that provided by the RPM Respiratory Gating System. The system sorts, or bins, the images based on the point in the respiratory cycle at which they were acquired. Using the binned images, the system can reconstruct volumetric CT images that minimize the motion artifacts appearing in the traditional CT images. [25] [26] © copyright UEA

35 Beam’s Eye Views of gated and non-gated treatment volumes
© copyright UEA

36 Gated 4-D CT Movie showing Lung Motion
© copyright UEA

37 MotionView™: addresses intra-fraction deformation
This offers particular advantages for targeting lung tumors which move and deform during respiration. Flat panel Amorphous Silicon Detector © copyright UEA

38 Inter-fraction Motion: Current Approaches
Image Guided Radiation Therapy (IGRT) 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. © copyright UEA

39 Elekta Synergy™ © copyright UEA
Elekta Synergy™ is an innovative digital linear accelerator integrated with a suite of advanced imaging tools, specifically designed for image guided radiation therapy (IGRT) Source: Elekta © copyright UEA

40 Elekta Synergy™ Synergy allows for co-registration of Cone-Beam CT and RTP data in real-time immediately before treatment delivery © copyright UEA

41 © copyright UEA

42 (Professor Chris Moore, Consultant Physicist, Christie Hospital)
“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 lying down 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 © copyright UEA

43 Current Research © copyright UEA

44 “The future is motion” - Varian annual report 2003
Even when patients are placed in precisely the same position for their daily treatments, some tumors can shift by as much as two to three centimeters over six to eight weeks of therapy. In addition, normal physiological processes like breathing cause some organs and tumors to move significantly during a daily treatment session. As we understand more about tumor motion, we have had to realize that we cannot position patients just on the basis of marks or tattoos on their external anatomy. As the treatments have become more conformal, and as we try to confine the high dose area much more strictly just to where the tumor is, we have to be all the more diligent in knowing exactly where the tumor is, every day. © copyright UEA

45 © copyright UEA

46 © copyright UEA

47 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 © Harvard Medical School © copyright UEA

48 Portal Video: Respiratory Motion
WP1.3 Aims to infer motion without using markers © copyright UEA

49 Ultimately we hope to simulate Dynamic MLC Control
© copyright UEA

50 ASM: Motion Tracking © copyright UEA
© Yu Su , School of Computing Sciences, UEA © copyright UEA

51 Building & Fitting ASM Models
© Yanong Zhu, School of Computing Sciences, UEA © copyright UEA

52 Image Registration via Graph Matching
© Muhannad Al-Hasan, School of Computing Sciences, UEA © copyright UEA

53 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 © copyright UEA

54 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 UEA

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