Imaging technology in radiotherapy

1. Overview

This course provides a foundational understanding of the physics and technology behind medical imaging in modern radiotherapy, specifically focusing on its application in treatment planning and verification. It details how Computed Tomography (CT) is essential for Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT), exploring the critical role of Hounsfield Units and relative electron density in accurate dose calculation. Finally, the session introduces Image-Guided Radiation Therapy (IGRT) systems like Electronic Portal Imaging Devices (EPIDs) for ensuring precision during treatment delivery.

2. Key Learning Objectives

After this course, you will be able to:

• Explain the basic physics principles of X-ray imaging and how a rotating source/detector system generates 3D volumetric data in a CT scanner.

• Justify the necessity of using CT for simulation and treatment planning in advanced techniques like IMRT and VMAT over conventional 2D simulation.

• Analyze the impact of Hounsfield Units (HU) and relative electron density (RED) on dose calculation accuracy across different tissues, such as air, bone, and soft tissue.

• Identify and strategize solutions for common inverse planning issues, including dose dumping in air cavities and dosimetric cold spots near high-density materials.

• Differentiate the applications, advantages, and limitations of various image verification technologies, specifically MV-based and KV-based systems like Electronic Portal Imaging Devices (EPIDs).
  
  

3. Why You Should Attend (The Benefits)

• Gain a deeper technical understanding of the imaging modalities fundamental to advanced radiation treatment planning and delivery.

• Develop the knowledge to troubleshoot and mitigate dosimetric uncertainties caused by varied tissue densities and metal artifacts.

• Improve your ability to contribute to accurate, high-quality IMRT and VMAT treatment plan verification.

• Prepare for more in-depth study on the principles and practice of Image-Guided Radiation Therapy (IGRT).
  
  

4. Topics Discussed

• How Imaging Technology has Changed Simulation and Treatment Planning

• Basic Physics of X-ray Image Creation and Absorption

• The Mechanism of CT Scanners and 3D Volumetric Image Generation

• The Essential Role of CT Scanning for IMRT and VMAT Planning

• Defining and Using Hounsfield Units (HU) and Relative Electron Density (RED)

• The Impact of Tissue Density on Radiation Dose Distribution (Air vs. Bone)

• Inverse Planning Challenges: Dose Dumping, Cold Spots, and PTV Contouring Adjustments

• Uncertainty and Artifact Management with High-Density Materials (e.g., metal implants)

• The Necessity of Imaging for Treatment Verification (Inter- and Intra-fraction Motion)

• Overview of Verification Options: MV-Based, KV-Based, and Surface Guidance

• Electronic Portal Imaging Devices (EPIDs): Functionality and Advantages
  
  

5. Keywords

#IMRT, #VMAT, #CT, #HounsfieldUnits, #ElectronDensity, #Dose, #EPID, #Artifacts, #IGRT