Stereotactic Body Radiation Therapy: The Report of AAPM Task Group 101 - PowerPoint PPT Presentation

View by Category
About This Presentation
Title:

Stereotactic Body Radiation Therapy: The Report of AAPM Task Group 101

Description:

The Report of AAPM Task Group 101 JOURNAL CLUB Slides prepared By Dr Wang Fuqiang, Registrar, Radiation Oncology, NCCS Daniel Tan Course Director – PowerPoint PPT presentation

Number of Views:961
Avg rating:3.0/5.0
Date added: 7 August 2020
Slides: 43
Provided by: sbrtsinga
Learn more at: http://sbrtsingapore.files.wordpress.com
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Stereotactic Body Radiation Therapy: The Report of AAPM Task Group 101


1
Stereotactic Body Radiation Therapy The Report
of AAPM Task Group 101
JOURNAL CLUB
Slides prepared By Dr Wang Fuqiang, Registrar,
Radiation Oncology, NCCS Daniel Tan Course
Director Associate Consultant Department of
Radiation Oncology National Cancer Centre
Singapore
2
Stereotactic Body Radiation Therapy The Report
of AAPM Task Group 101
  • Aims
  • Know the existence of this resource
  • Know the contents of this resource
  • Briefly run through this resource to make a
    mental note

3
Stereotactic Body Radiation Therapy The Report
of AAPM Task Group 101
4
I. Introduction and Scope
5
I. Introduction and Scope
Contents
6
I. Introduction and Scope
  • SBRT
  • emerging RT procedure for the treatment of early
    stage primary and oligometastatic cancer
  • delivery of large doses in few fractions
    resulting in high biological effective dose
  • to minimise normal tissue toxicity, need to
    ensure high conformity and rapid fall-off doses
    away from the target
  • therefore high level confidence in accuracy of
    treatment is required for SBRT
  • this is achievable by integrating modern imaging,
    simulation and treatment planning and delivery
    technologies

7
I. Introduction and Scope
  • In SBRT, confidence in this accuracy is
    accomplished by the integration of modern
    imaging, simulation, treatment planning, and
    delivery technologies into all phases of the
    treatment process from treatment simulation and
    planning, and continuing throughout beam
    delivery.

8
(No Transcript)
9
II. History and Rationale of SBRT
  • outcomes of SBRT for both primary and metastatic
    disease compare favourably to surgery
  • many conceptual theories
  • sites of gross disease containing highest number
    of clonogenic cells not eliminated by
    chemotherapy
  • oligometastatic disease which can be eradicated
    if numbers are limited
  • Norton-Simon hypothesis whereby cancer increases
    from low undetectable level to a phase of
    exponential growth and a lethal plateau,
    therefore SBRT may aid in the reduction of
    systemic burden to delay lethal tumour burden

10
II. History and Rationale of SBRT
  • immunomodulation
  • palliative treatment
  • clinical patient outcomes first published in 1995
  • initially focused on liver and lung lesions
  • subsequently other studies included spinal
    lesions

11
III. Patient Selection Criteria
  • mostly lung/ liver/ spinal lesions
  • well circumscribed tumours up to 5cm
  • SBRT has been used as a boost in addition to
    regional nodal irradiation
  • careful evaluation of normal tissue function and
    dose distribution (typically pulmonary function
    and volume of liver irradiated)
  • important structures should be avoided

12
III. Patient Selection Criteria
  • Recommendations
  • formal group trials with appropriate protocols
  • or an institution treatment protocol/ guidelines
    as developed by radiation oncologists and
    physicists

13
IV. Simulation Imaging and Planning
  • A. Simulation Imaging
  • CT/ 4D CT/ MRI/ PET
  • Recommendation
  • simulation done in treatment position
  • cover target and all OARs
  • 5-10cm superior and inferior of normal treatment
    borders (15cm if non-coplanar treatment
    techniques)
  • tomographic slice thickness of 1-3mm

14
IV. Simulation Imaging and Planning B
  • B. Data Acquisition
  • Multiple sources for organ/ tumour motion during
    simulation
  • Population based margins may be incorrectly
    applied
  • refer to AAPM Task Group 76 report on various
    tumour motion strategies

15
IV. Simulation Imaging and Planning
  • C. Imaging Artifacts
  • If target and radiosensitive critical structures
    cannot be localised on section imaging modality
    with sufficient accuracy because of motion and/
    or metal artifacts, SBRT should not be pursued as
    a treatment option

16
IV. Simulation Imaging and Planning
  • D. Treatment Planning
  • Limited volume of tissues containing the gross
    tumour and close vicinity are targeted for high
    dose per fraction treatment, hot spots within the
    target are deemed acceptable
  • Volume of normal tissue receiving high doses
    should be minimised by a sharp dose fall-off
    outside of the target

17
IV. Simulation Imaging and Planning
  • D. Treatment Planning
  • ICRU 50/ 62
  • GTV/CTV considered identical
  • Variation in CTV due to motion/ organ filling
    accounted for by ITV
  • PTV

18
IV. Simulation Imaging and Planning
  • D. Treatment Planning
  • 1. Dose Heterogeneity, gradient and fall-off and
    beam geometry
  • dose prescription specified at lower isodose with
    small or no margins for penumbra
  • hotspots within target deemed acceptable and
    clinically desirable
  • use of multiple nonoverlapping beams to achieve
    sharp dose fall-off
  • beam energy (6MV smaller penumbra)
  • resolution of beam shaping (as determined by MLC
    leaf width-gt 5mm adequate)

19
IV. Simulation Imaging and Planning
  • D. Treatment Planning
  • 2. Beam selection and beam geometry
  • restricting entrance dose to lt30 of cumulative
    dose and avoiding beam overlaps to prevent acute
    skin reactions
  • increased number of beams yield better conformity
    but not practical (VMAT may overcome this issue)

20
IV. Simulation Imaging and Planning
  • D. Treatment Planning
  • 3. Calculation grid size
  • 2mm grids required for IMRT
  • Recommendation 2mm of finer for SBRT, gt3mm not
    acceptable
  • a 2.5 mm isotropic grid produces an accuracy of
    about 1 in the high-dose region of an IMRT plan
    consisting of multiple fields
  • Another report indicated an accuracy of /- 5
    for an isotropic grid resolution of 4 mm.
  • Chung et al. found a dose difference of 2.3 of
    the prescribed dose for 2 mm calculation grids as
    compared to 1.5 mm grids, rising to 5.6 for 4 mm
    grids.
  • conclusion is that 2 mm grids are required for
    IMRT procedures, especially in high-dose gradient
    areas.

21
IV. Simulation Imaging and Planning
  • D. Treatment Planning
  • 4. Bioeffect-based treatment planning
  • NTD derived from conventional RT unlikely to be
    applicable to SBRT
  • Bioeffect measures (BED/ NTD/ EUD) required to
    rank and compare SBRT plans with conventional
    plans

22
(No Transcript)
23
IV. Simulation Imaging and Planning
  • D. Treatment Planning
  • 5. Normal Tissue Dose Tolerance
  • Recommendation Normal tissue dose tolerance in
    the context of SBRT still evolving , limited
    experiences to draw recommendations

24
IV. Simulation Imaging and Planning
25
IV. Simulation Imaging and Planning
26
IV. Simulation Imaging and Planning E
  • E. Treatment plan reporting
  • prescription dose/ ICRU reference point / number
    of fractions/ total treatment delivery period/
    target coverage
  • plan conformity
  • heterogeneity index
  • dose fall-off outside of target
  • notable areas of high/ low dose outside of PTV
  • dose to OARs

27
V. Patient Positioning, Immobilisation, Target
Localisation and Delivery
28
V. Patient Positioning, Immobilisation, Target
Localisation and Delivery
  • B. Image-guided localisation
  • For SBRT, image guided localisation techniques
    should be used to guarantee the spatial accuracy
    of delivered dose distribution
  • gantry mounted kV units capable of fluoroscopy,
    radiographic localisation and cone beam imaging
  • implantation of fiducials
  • ultrasound imaging
  • radiofrequency tracking

29
V. Patient Positioning, Immobilisation, Target
Localisation and Delivery
  • C. localisation, tumour tracking and gating
    techniques for respiratory motion management
  • 1. Image-guided techniques
  • Cone beam imaging with acquisition time gt60s
  • fast CT less ideal because position of tumour may
    be captured at random

30
V. Patient Positioning, Immobilisation, Target
Localisation and Delivery
  • C. localisation, tumour tracking and gating
    techniques for respiratory motion management
  • 2. Optical tracking techniques
  • stereoscopic infrared cameras and video
    photogrammetry used to track 3D coordinates of
    points on patients skin

31
V. Patient Positioning, Immobilisation, Target
Localisation and Delivery
  • C. localisation, tumour tracking and gating
    techniques for respiratory motion management
  • 3. Respiratory gating techniques
  • delivery of dose at certain phases of breathing
  • issue of reproducibility
  • recommend patient-specific tumour motion
    assessment for thoracic/ abdominal targets

32
V. Patient Positioning, Immobilisation, Target
Localisation and Delivery
  • D. Delivery data reporting
  • report that QA process is in use and proper
    documentation for accurate treatment delivery

33
VI. Special Dosimetry Considerations
  • A. Problems associated with dosimetry of small/
    narrow field geometry
  • an appropriate dosimeter with a spatial
    resolution of 1mm or better
  • maximum inner diameter of a detector should be
    lthalf the FWHM of smallest beam measure

34
VI. Special Dosimetry Considerations
  • B. Problems associated with small-field
    heterogeneity calculations
  • when target is surrounded by low-density tissue
  • Monte Carlo precalculated dose-spread kernels and
    employing convolution/ superposition techniques
  • AAPM Task Group 65 recommend inhomogeneity
    corrections be used for patient dose calculation

35
VII. Clinical Implementation of SBRT
  • Critical steps involved
  • establish scope of program
  • determine treatment modality
  • equipment requirements
  • personnel needed
  • acceptance/ commissioning
  • establish work flow guidelines/ reporting/ QA
  • conduct personnel training

36
VII. Clinical Implementation of SBRT
  • A. Establishing the scope and clinical Goals
  • 1. Equipment considerations
  • integration of treatment machines with
    pre-existing planning system and imaging
    localisation

37
VII. Clinical Implementation of SBRT
  • A. Establishing the scope and clinical Goals
  • 2. Time and personnel considerations
  • additional physicist involvement

38
VII. Clinical Implementation of SBRT
  • B. Acceptance, commissioning and QA
  • acceptance test procedures by vendors
  • commissioning tests developed by physicists
  • QA procedures for both treatment and patient

39
VII. Clinical Implementation of SBRT
  • C. Patient safety and the medical physicist
  • recommend one medical physicist to be present
    throughout first treatment fraction and available
    for subsequent fractions

40
VII. Clinical Implementation of SBRT
  • D. Quality process improvement Vigilance in the
    error reduction process in the treatment planning
    and delivery process
  • regular review of existing QA procedures with the
    objective of assessing and critiquing the current
    QA practice

41
VIII. Future Directions
  • incorporation of strategies for the adaptive
    conformation of treatment fields
  • incorporation of bioeffect knowledge into
    treatment process
  • incorporation of improvements in small field
    dosimetry performance in clinical treatment
    planning system
  • incorporation of chemotherapy
  • incorporation of molecular imaging
  • incorporation of tumour-motion effects into the
    treatment planning and the methods of evaluation
    for the delivered SBRT dose to a dynamic target
  • volumetric modulated arc therapy
  • proton and heavy ion therapies

42
Goldmine
About PowerShow.com