EPID Real-Time Dose Verification for Radiation Treatment Errors

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Solution Overview

Problem

Existing radiation therapy techniques, such as IMRT and VMAT, lack real-time monitoring for potential errors during treatment delivery, including system misalignment, patient positioning issues, and anatomical changes, which can lead to harmful radiation exposure.

Innovation Solution

Utilizing an electronic portal imaging device (EPID) to capture a continuous stream of megavoltage image frames, allowing real-time dose verification by comparing actual dose delivery to predetermined characteristics, generating error signals for non-compliance, and halting treatment if necessary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If pre-treatment verification is performed without the patient in place, then the treatment system capability can be confirmed, but patient-specific errors such as setup misalignment and anatomical changes cannot be detected

Engineering Contradiction:

Improvetreatment delivery accuracyVSAvoidpatient-specific information

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The system performs preliminary actions by acquiring reference portal images before treatment and establishing expected dose distribution characteristics in advance. These pre-acquired images and characteristics serve as a baseline for real-time comparison during actual treatment delivery

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by continuously acquiring portal images during treatment delivery and comparing them against the reference images and predetermined characteristics. This real-time feedback loop enables detection of deviations from the planned treatment delivery

Inventive Principle:

Principle #23Feedback

2Reliability

If real-time monitoring is implemented using EPID, then patient safety can be improved, but system complexity and processing requirements increase

Engineering Contradiction:

Improvepatient safetyVSAvoidreal-time verification system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system leverages the existing EPID, which is already part of the linear accelerator, to serve multiple functions: both its traditional imaging role and the new real-time dosimetric verification role. This eliminates the need for separate monitoring hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system creates a digital copy of the treatment field by acquiring portal images that represent the radiation beam's path through the patient. These image copies are then processed to extract dose information without requiring physical dosimeters in the treatment path

Inventive Principle:

Principle #26Copying

3Measurement precision

If continuous stream of image frames is acquired and processed in real-time, then dose verification accuracy is improved, but processing time and computational load increase

Engineering Contradiction:

Improvedose measurement accuracyVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system extracts only the essential dose-related information from the continuous stream of portal images by comparing them against predetermined characteristics. This selective extraction focuses computational resources on critical verification parameters rather than processing all image data equally

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system performs partial verification by focusing on key dose parameters and critical regions of the treatment field. This approach provides sufficient safety verification without requiring complete analysis of every aspect of the dose distribution

Inventive Principle:

Principle #16Partial or excessive action

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

Ensures safe and accurate radiation delivery by detecting deviations in real-time, preventing patient injury through immediate intervention.

Implementation Method 1

The EPID of a radiation therapy system can be extended behind the patient. Radiation from the treatment system that exits the patient can be detected by the EPID, which generates a cine stream of megavoltage (MV) image frames.

Methodology Applied

Scientific EffectMegavoltage radiation detection: X-Ray

Data Source

PatentUS12508447B2Systems, methods, and devices for real-time treatment verification using an electronic portal imaging device

Publication Date: 2025.12.30 SIEMENS HEALTHINEERS INTERNATIONAL AG

AI summary

A radiation dose received by a patient from a radiation therapy system can be verified by acquiring a cine stream of image frames from an electronic portal imaging device (EPID) that is arranged to detect radiation exiting the patient during irradiation. The cine stream of EPID image frames can be processed in real-time to form exit images providing absolute dose measurements at the EPID (dose-to-water values), which is representative of the characteristics of the radiation received by the patient. Compliance with predetermined characteristics for the field can be determined during treatment by periodically comparing the absolute dose measurements with the predetermined characteristics, which can include a predicted total dose in the field after full treatment and/or a complete irradiation area outline (CIAO). The system operator can be alerted or the irradiation automatically stopped when non-compliance is detected.