Dynamic PTV Generation for Motion-Compensated Radiation Therapy
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Solution Overview
Problem
Conventional radiation therapy methods irradiate significant amounts of healthy tissue due to the use of static planning target volumes that encompass all motion phases of a tumor, leading to unnecessary radiation exposure and reduced quality of life for patients, especially when the tumor moves during treatment.
Innovation Solution
A system and method that utilize real-time target volume tracking and 4D motion modeling to generate dynamic planned target volumes for each motion phase of a tumor, allowing for precise irradiation of the tumor at each phase, thereby reducing radiation dose to healthy tissue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If static planning target volumes are used to encompass all motion phases of the target, then the target is covered in all motion phases, but significant amounts of healthy tissue receive unnecessary radiation dose
Solution Approach 1:
The patent applies the dynamics principle by transitioning from static PTV to dynamic PTV that adapts to different motion phases. The system generates multiple PTVs corresponding to different respiratory phases (inhalation, exhalation, transition) and selects the appropriate PTV based on real-time tracking of target position and motion phase. This dynamic adaptation ensures the PTV accurately encompasses the target at each moment while minimizing healthy tissue exposure.
Solution Approach 2:
The patent implements parameter changes by modifying the PTV parameters (position, size, shape) based on motion phase parameters. The system uses 4D CT data to establish relationships between target position, motion phase, and optimal PTV parameters. During treatment, as motion phase parameters change, the system adjusts PTV parameters accordingly to maintain accurate target coverage while reducing healthy tissue dose.
2Reliability
If generic population-based margins are used to ensure target dosage in the presence of motion, then the target receives adequate dose, but normal tissue surrounding the target receives unnecessary dose
Solution Approach 1:
The patent applies local quality by creating PTVs with locally optimized margins for different motion phases and anatomical regions. Instead of using uniform population-based margins throughout, the system generates phase-specific PTVs with margins tailored to the local geometry and motion characteristics at each respiratory phase. This allows adequate target coverage with minimal margins where possible, reducing unnecessary normal tissue exposure.
3Productivity
If traditional static planning is performed as a one-time process, then the treatment plan can be delivered over multiple fractions, but target motion between and during treatment fractions hinders the ability to deliver treatment as planned
Solution Approach 1:
The patent implements feedback by continuously tracking target position and motion phase during treatment delivery using real-time imaging and motion monitoring systems. The tracked information is fed back to the treatment planning system, which dynamically selects or adjusts the PTV based on current motion phase. This closed-loop feedback ensures the treatment plan remains accurate despite target motion between and during treatment fractions.
Solution Approach 2:
The patent applies preliminary action by pre-generating multiple PTVs corresponding to different motion phases from 4D CT data before treatment begins. The system also pre-establishes the relationships between motion phase parameters and optimal PTV selections. During treatment, this pre-computed information enables rapid PTV selection without requiring real-time replanning, maintaining treatment efficiency while ensuring accuracy.
Data Source
AI summary
When reducing radiation dose to healthy tissue near a target volume, a 4D motion model (52) of a target volume is generated during CT scan data acquisition. The target volume is tracked, and tracked target volume position information (43) is provided to a motion estimation tool (48). Motion parameter information (60) output from the motion estimation tool is linked to motion phases of the target volume indicated by CT scan data. A dynamic planned target volume (PTV) (64) that covers the target volume in each motion phase is generated and linked to tracked motion parameters for each respective motion phase. A radiation dose is delivered to the PTV for each motion phase using the linked motion parameters and real-time tracking information.