MR Linac Radiotherapy: A New Personalized Treatment Approach

Front Cover
MR Linac Radiotherapy: A New Personalized Treatment Approach
Copyright
Contents
Contributors
Preface
Chapter 1: Rationale for the MR-linac
Optimal radiotherapy
MR-guided radiotherapy
Opportunities of MR-guided radiotherapy
Concluding remarks
References
Chapter 2: Basics of MR imaging for the radiation oncologist
Introduction
Image fusion
MRI in radiation oncology
MR imaging
Basics of MR imaging
MRI tissue characterization
T1-weighting
T2-weighting
Diffusion-weighted imaging
Fat suppression and saturation
Modern and other common sequences
Contrast enhancement
Hardware considerations and field strength
Artificial intelligence in MRI
MR linac (MRL) in radiation oncology
Dose escalation
Toxicity
Current trends in MRL
ViewRay system
Elekta Unity system
University of Alberta MRI-Linac
Australian MRL system
Benefits and challenges
Outlook of MRI in radiation oncology
Concluding remarks
References
Chapter 3: Technical concepts of MRI-Linac (MRL)
Introduction: The challenges of a hybrid MRI-Linac system
Perpendicular systems
ViewRay MRIdian: Pioneering MRgRT
The major milestones of the project are summarized below
The specifications of the system can be summarized as follows
Significant advantages of the ViewRay system include
Elekta Unity: The first in-man use of an MRL
The specifications of the system are summarized below
The major milestones of the Unity system are summarized as follows
Significant advantages of the unity system include
Inline systems
The Australian MRL: Flexibility and adaptability
The major milestones of the project are summarized below
The specifications of the system are summarized below
Significant inherent advantages of the AMRL system include:
Alberta Aurora-RT: Rotating BiPlanar Linac-MR
The major milestones can be summarized by the following
The specifications of the system can be summarized as follows
Significant advantages of the Alberta system include
Concluding remarks
References
Chapter 4: Linac dosimetry in a magnetic field
Introduction
Physics
Lorentz force
Dose distribution in a magnetic field
Systems and configurations
Measurements in B-fields
Phantoms, materials, and setup
Detectors
Reference dosimetry
Need for accurate reference dosimetry
Codes of practice for reference dosimetry
Reference conditions and influence quantities
Measurement of absorbed dose to water
Beam quality specification
Measurement conditions and ionization chambers to be used
Linac reference conditions
Uncertainty
Additional concepts
Concluding remarks
References
Chapter 5: MR safety considerations for MRI-guided radiotherapy
Introduction
Magnetic field-induced hazards
Main magnetic field-induced issues
Time-varying gradient magnetic field-induced issues
Time-varying radiofrequency magnetic field-induced issues
Safety considerations for MR in RT
Safety screening for patients and personnel
Planning for the site and personnel access
Device considerations
Patient implants
Immobilization and accessory devices
QA equipment
Concluding remarks
References
Chapter 6: Robust online adaptive planning: Toward a uniform MR-LINAC treatment planning technique
Introduction
Initial approach to treatment planning
Dose calculation settings
The early use of dummy structures in creating a plan
VMAT-like IMRT
Chasing further efficiencies and MPT
Principles of a uniform MR-LINAC planning technique
Why the MR-LINAC asks for a different planning technique
The principles of a uniform planning technique robust to adaptation
The use of flexible volumes
The intrinsic dose fall-off (IDF) margin
Providing the optimizer with sufficient degrees of freedom
Building isotoxic normalization into the base plan
MPT: A uniform, simple, and fast approach to treatment planning on an MR-LINAC
Making the MPT base plan (SBRT for pancreas)
A basic set of rules
A basic set of objectives and isotoxic normalization
Adapting an MPT plan (SBRT for pancreas)
Creating the volumes for plan adaptation
Recalculation and normalization
Incorporating MPT-An evaluation
MPT and the use of dummy structures
Qualitative improvements incorporating MPT
Quantitative improvements incorporating MPT
Concluding remarks
Acknowledgment
References
Chapter 7: Immobilization and patient positioning considerations when using MRI for radiotherapy treatment planning
Introduction
Utilizing magnetic resonance imaging (MRI) for radiotherapy treatment planning (RTP)
General principles and equipment
MRI systems
MRI scanning protocols
Workforce and training
Patient communication
Coil bridges
Safe and efficient patient setup
Site-specific considerations
Brain
Head and neck
Thorax and abdomen
Breast
Pelvis
Spine
Limbs
Concluding remarks
References
Chapter 8: Treatment planning and delivery workflow steps in MR-guided adaptive RT
Introduction
Reference treatment planning workflow steps
Pretreatment imaging, fusion, and structure delineation
Electron density handling
Reference dose planning
Treatment delivery
Patient handling
Online MR imaging and image registration
Plan adaptation process
Physical or virtual couch shift
Deformable image registration, contour propagation, and editing
Electron density handling
Online dose replanning and adaptive plan evaluation
Verification imaging
Cine imaging for motion monitoring and gating
Quality assurance of daily replanning
Workflow timing
Concluding remarks
References
Chapter 9: QA of MR-linac
Geometric machine QA of MR-linac
Impact of magnetic field
Iso-centers
Rotational check of MLC/Jaw and EPID
Mechanical QA of the treatment couch
Vertical beam direction
Size of the radiation iso-center
Gantry angle validation
Radiation iso-center
MLC and jaw calibration
Dosimetric QA of MR-linac
Commissioning/3D water phantom
Absolute dosimetry
Gantry-dependent output
Output constancy
Autobeam Gating
QA of MR-linac images and center position
Visual image quality
Geometric accuracy
MR versus radiation iso-center alignment
End-to-end QA of MR-linac
Patient-specific QA
Pretreatment patient-specific QA
Online patient-specific QA during adaptive delivery
EPID dosimetry
Concluding remarks
References
Chapter 10: Changing role of radiation therapy technologists in magnetic resonance-guided radiotherapy
Introduction
Implementation
``Business as usual´´
Image acquisition (prior to treatment and online)
Delineation (prior to treatment)
Treatment planning (prior to treatment)
Online fraction
Online fraction: (Re)delineation of OAR and tumor
Online treatment plan
Plan QA
Intrafraction monitoring
Training
Conditions and infrastructure
Concluding remarks
References
Chapter 11: Central nervous system tumors
Introduction
Multiparametric MRI for MR Linac neuroimaging
Anatomic MRI
Relaxometry
Diffusion
Perfusion
Spectroscopy and metabolic imaging
MRI analysis and radiomics
Benefits of low-field MR Linac
Clinical applications for MR Linac therapy in the CNS
Glioblastoma
Brain metastases
Spinal metastases
Concluding remarks
References
Chapter 12: Esophageal cancer
Introduction
Staging
Evidence-based treatment approaches for locoregional disease
Selection for nonoperative management
Rationale for MR-guided radiotherapy in esophageal cancer
Interfraction tumor shape adaptation
Intrafraction tumor motion
Treatment-related toxicity
Targeted selected dose escalation
Target volume determination and delineation guidelines
Simulation
Treatment planning
Concluding remarks
References
Chapter 13: Lung tumors
Concluding remarks
References
Chapter 14: Breast cancer: Role of MR-guided radiation therapy
Introduction
External beam radiotherapy
MRI-guided APBI
CT and MRI simulation
Treatment planning
Treatment delivery
Published treatment outcomes
Concluding remarks
References
Chapter 15: MR-guided radiotherapy for liver tumors: Hepatocarcinomas, cholangiocarcinomas, and liver metastases
Introduction
Stereotactic body radiotherapy for liver tumor before MRI-guided radiotherapy (MRgRT) era
Liver metastases
Hepatocellular carcinoma
Cholangiocarcinomas
MRI-guided radiotherapy (MRgRT) for primary and secondary hepatic malignancies
Advantages of MRgRT for hepatic tumors
Visualization of liver lesions
Motion management
Adaptive procedure
Aspects of liver tumors on MR-linac images
Liver MRgRT-physics and treatment
Patient immobilization and simulation
Contouring/margins
Treatment planning
Technique
Ballistic
Optimization
Dose constraints
Treatment delivery
Published studies on MRgRT for liver tumors
Appendix: Supplementary material
Concluding remarks
References
Chapter 16: Pancreatic cancers
Introduction
General management
Resectable pancreatic cancer
Borderline resectable pancreatic cancer (BRPC)
Locally advanced pancreatic cancer (LAPC)
Metastatic pancreatic cancer
Radiation therapy
Stereotactic radiation therapy (SBRT)
Magnetic resonance image-guided radiation therapy (MRgRT)
Concluding remarks
References
Chapter 17: MR linac radiation therapy: A real-time personalized approach for prostate cancer
Introduction
Rationale for MRgRT
Practical considerations
MRgRT platforms
MRgRT logistics and workflow
Definitive radiotherapy
MR-guided definitive radiotherapy for definitive prostate cancer-Overview
Definitive treatment intro
Patient selection
Planning and treatment delivery
Current clinical evidence
Other considerations
Fraction reduction
Rectal spacer
Focal boost
Salvage reirradiation
Postoperative radiotherapy
Imaging considerations for PORT
MR guidance for treatment delivery and planning
Hypofractionation in PORT
Limitations
Future directions
Dose escalation
Integration with functional imaging
Integration with artificial intelligence
Trial endpoints and expectations
Concluding remarks
References
Chapter 18: Online MR-guided radiotherapy in rectal cancer-Dose escalation and beyond
Evolution of the current standard multimodality treatment of rectal cancer: From blunt resection to total neoadjuvant therapy
Role of magnetic resonance imaging in the staging of rectal cancer
Potential benefit of online MR-guided radiotherapy in rectal cancer
Organ preservation in case of a clinical complete response to radiotherapy
Data available on online adaptive MR-guided radiotherapy
Concluding remarks
References
Chapter 19: Oligometastatic disease: Adrenal, lymph nodes, bone
Introduction
Oligometastatic state
Definition and classification of oligometastases
Stereotactic body radiotherapy trials (SBRT): Success and toxicity
Overall survival benefit
Toxicity
MR-guided SBRT for metastatic disease: Dosimetric data and case reports
Bone oligometastasis
Lymph node oligometastasis
Adrenal oligometastasis
MR-guided SBRT for oligometastatic disease: Clinical data
Future perspectives
Concluding remarks
Appendix: Supplementary material
References
Chapter 20: Gynecological tumors
Introduction
The use of MRg-RT in cervical cancer
Introduction
Potential gains of MRg-RT in cervical cancer patients
Inter- and intra-fraction movements of the cervix
Target volume in cervical cancer: Whole uterus vs. high-risk CTV
MR-guided SBRT instead of BRT
Functional imaging dose painting
The use of MRg-RT in endometrial cancer
Introduction
Role of MRg-RT in inoperable endometrial cancer
Role of MRg-RT in vaginal vault recurrences
Role of MRg-RT in pelvic and abdominal wall recurrences
The use of MRg-RT in ovarian cancer
Introduction: ovarian cancer treatment and the role of radiotherapy in ovarian cancer patients
Role of MRg-RT in recurrent ovarian cancer
Role of MRg-RT in oligometastatic ovarian cancer
Special conditions
MRg-RT for local recurrences from gynecological tumors
MRg-RT for oligometastatic gynecological cancer
MRg-RT for nodal recurrences
Examples of MRg-RT for gynecologıcal tumors
Case 1
Case 2
Concluding remarks
References
Further reading
Chapter 21: Magnetic resonance-guided radiotherapy in pediatric cancers
Introduction
Major tumor types, local approaches, and outcomes
Brain tumors
Solid tumors
Hematologic tumors
Radiotherapy-related toxicity profile for major pediatric tumor types
Is late toxicity avoidable by MRgRT?
Survey on the potential role of MRgRT in pediatric radiotherapy among future users
The ideal niche for MRgRT in pediatric patients
Case 1. Daily online adaptive radiotherapy to meet OAR constraints
Case 2. Intrafraction motion management-Moving target soft-tissue visualization
Case 3. Superior tumor visualization and OAR sparing-Simulation and daily IGRT soft-tissue visualization
Case 4. Weekly QA MRI-Soft tissue visualization for offline adaptive replanning or MR simulation
Current challenges for MRgRT in pediatrics
Concluding remarks
References
Chapter 22: MR-guided SBRT for unusual tumors (cardiac, kidney, bladder)
Cardiac and pericardiac tumors
Case no. 1
Case no. 2
Bladder cancer
Kidney
Oligometastatic RCC
Concluding remarks
References
Chapter 23: Patient reported outcomes in the use of MR-guided radiotherapy
Patient experience
PROMs
Introduction to PROMs
Adverse event reporting
PROMS in MRgRT
Concluding remarks
References
Chapter 24: Use of artificial intelligence in MR-guided RT
Artificial intelligence in the MR-guided RT workflow
AI1: Automatic segmentation
AI2: Synthetic CT
AI3: Automatic planning
AI4: Automatic QA
AI5: Motion management
Concluding remarks
References
Chapter 25: Radiomics for MR-Linacs: State of the art and future directions
The radiomics concept
Radiomics experiences on MR-Linac
0.35-T MR Linac
1.5-T MR Linac
Concluding remarks
References
Index
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