Cherenkov Imaging Phantom for MR-Linac Isocenter Verification

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Solution Overview

Problem

MR-Linac systems face challenges in verifying mechanical, imaging, and radiation isocenter coincidence due to the magnetic environment, with existing methods being cumbersome and time-consuming, particularly the vendor-recommended film-based methods which are not suited for daily use.

Innovation Solution

A Cherenkov imaging-based quality assurance system using a cylindrical phantom with a conical structure that emits Cherenkov radiation, combined with a camera for time-gated imaging, allows for efficient and immediate measurement of isocenter coincidence by capturing Cherenkov light distribution, providing 3D positional information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If film-based methods are used for isocenter verification, then measurement accuracy is improved, but time consumption and operational complexity increase

Engineering Contradiction:

Improveisocenter coincidence verification accuracyVSAvoidpost-processing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the mechanical film-based measurement system with an optical Cherenkov imaging system. The conical structure emits Cherenkov radiation when exposed to therapeutic beams, and a camera captures the light distribution to directly determine isocenter position in 3D space, eliminating the need for film development and manual coordinate analysis.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates an optical copy of the dose distribution through Cherenkov light emission. The conical structure converts absorbed radiation energy into visible Cherenkov photons, which are captured by the camera to form an optical representation of the beam geometry and isocenter position, replacing the physical film copy method.

Inventive Principle:

Principle #26Copying

2Reliability

If traditional detector arrays are used in magnetic environment, then radiation detection capability is maintained, but compatibility and measurement accuracy deteriorate

Engineering Contradiction:

Improvedetector functionalityVSAvoidmagnetic environment compatibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent replaces traditional electrical detectors with an optical detection system. Cherenkov radiation is captured by a camera that operates outside the magnetic field's direct influence, converting the problem of magnetic incompatibility into an optical measurement approach that is inherently compatible with the MR-Linac environment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The conical structure acts as an intermediary that converts therapeutic radiation into Cherenkov light. This intermediary process allows indirect measurement of beam geometry and isocenter position without requiring detectors to be directly exposed to the therapeutic beam within the magnetic field, thereby resolving the compatibility issue.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of information

If complex post-processing analysis is performed on film data, then measurement completeness is improved, but operational simplicity and productivity decrease

Engineering Contradiction:

Improve3D isocenter information completenessVSAvoiddaily QA throughput

Core Design Contradiction:

Loss of informationVSProductivity

Solution Approach 1:

The patent uses the conical geometry to encode 3D spatial information into a 2D image projection. The angled surfaces of the cone create distinct Cherenkov light patterns that allow simultaneous determination of isocenter position in all three dimensions from a single camera view, eliminating the need for multiple measurements and complex post-processing.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The conical structure is designed to self-encode the 3D isocenter information through its geometry. The angled surfaces automatically create distinguishable Cherenkov patterns that directly reveal spatial relationships, allowing the measurement system to extract complete 3D information without requiring external calibration or complex computational analysis.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The system enables simplified and efficient daily verification of isocenter coincidence with near-real-time analysis, achieving sub-millimeter accuracy and overcoming the limitations of traditional film-based methods.

Implementation Method 1

A Cherenkov imaging-based quality assurance system includes an enclosed cylindrical plastic phantom containing a conical structure that emits Cherenkov radiation when exposed to therapeutic ionizing radiation

Methodology Applied

Scientific EffectCherenkov radiation: Cherenkov Effect

Data Source

PatentUS12427342B2Cherenkov imaging-based solution for MR-Linac quality assurance

Publication Date: 2025.09.30 TRUSTEES OF DARTMOUTH COLLEGE THE

AI summary

A system includes a cylindrical phantom and a conical structure disposed in the phantom. The conical structure is shaped as a frustum and emits Cherenkov radiation when exposed to ionizing radiation. The system can be used for calibration of an MR-Linac system by exposing the system to ionizing radiation. The Cherenkov radiation can be imaged during exposure to ionizing radiation.