PET Detector Time-Lag Calibration Using TOF Image Data

Solution Overview

Problem

Existing Time-of-Flight (TOF) Positron Emission Tomography (PET) systems require manual time calibration using external radiation sources, which is time-consuming and exposes technicians to radiation.

Innovation Solution

A PET apparatus that estimates time lag between detectors using TOF information and reconstructed images, allowing for automated and radiation-free calibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual time calibration using external radiation source is performed, then TOF calibration accuracy is improved, but calibration time and radiation exposure increase

Engineering Contradiction:

ImproveTOF calibration accuracyVSAvoidcalibration time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs self-calibration by automatically estimating time lag between detectors using TOF information from coincidence data and reconstructed images, eliminating the need for manual calibration with external radiation sources. The processing circuitry autonomously identifies time lag and adjusts detection timing without human intervention.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent uses TOF information from coincidence counting data as an intermediary to estimate time lag between detectors. Instead of directly measuring time lag with external equipment, the system uses the TOF data already collected during normal operation to indirectly determine and correct timing offsets.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If manual time calibration using external radiation source is performed, then TOF calibration accuracy is improved, but operator radiation exposure increases

Engineering Contradiction:

ImproveTOF calibration accuracyVSAvoidradiation exposure

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system performs self-calibration by automatically estimating time lag between detectors using TOF information from coincidence data and reconstructed images, eliminating the need for manual calibration with external radiation sources. The processing circuitry autonomously identifies time lag and adjusts detection timing without human intervention.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent converts the TOF information, which is normally used only for image reconstruction, into a useful resource for calibration. By repurposing the existing TOF data and coincidence information from patient scans, the system transforms routine operational data into a calibration tool, eliminating the need for separate calibration procedures involving radiation exposure.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If automated calibration using TOF information is implemented, then calibration efficiency is improved, but system complexity increases

Engineering Contradiction:

Improvecalibration efficiencyVSAvoidsystem complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The processing circuitry performs multiple functions: it reconstructs PET images from coincidence data, calculates TOF information for image quality, and simultaneously uses the same TOF information for time lag estimation and calibration. This multi-functionality eliminates the need for separate calibration hardware or procedures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system performs self-calibration by automatically estimating time lag between detectors using TOF information from coincidence data and reconstructed images, eliminating the need for manual calibration with external radiation sources. The processing circuitry autonomously identifies time lag and adjusts detection timing without human intervention.

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

Facilitates efficient and simplified TOF calibration, reducing manual effort and radiation exposure by using collected patient data for calibration, enabling accurate TOF reconstruction.

Implementation Method 1

a PET detector 101... detects a gamma ray that is emitted from living tissue in which positron-emitting radionuclide that is given to a subject P is captured

Methodology Applied

Scientific EffectGamma ray detection: Photoelectric Effect

Implementation Method 2

In recent years, in a Time-of-Flight (TOF)-Positron Emission computed Tomography (PET) apparatus, TOF resolution is improved and it becomes possible to perform reconstruction using TOF information with improved accuracy

Methodology Applied

Scientific EffectTime of Flight: Time of Flight

Data Source

PatentUS12471857B2Pet apparatus, method, and storage medium

Publication Date: 2025.11.18 CANON MEDICAL SYST CORP

AI summary

A PET apparatus according to one embodiment includes processing circuitry. The processing circuitry acquires list mode data. The processing circuitry reconstructs a PET image based on the list mode data. The processing circuitry identifies first coincidence data that is obtained by coincidence counting by a first detector and a second detector that is different from the first detector from among a plurality of pieces of coincidence data included in the list mode data. The processing circuitry estimates a time lag amount between the first detector and the second detector based on TOF information included in the first coincidence data and the PET image.