PET Coincidence Weighting for True Event Selection

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Solution Overview

Problem

In positron emission tomography (PET) scanners, the rejection of multi-photon coincidence events leads to a significant loss of true coincidence events, resulting in degraded image quality due to increased random and scatter events, necessitating a method to identify and select true coincidences from among multi-coincidences.

Innovation Solution

A nuclear medicine diagnosis device with an acquisition unit, determination unit, and generation unit that acquires gamma ray detection data, determines the weight of each coincidence based on events within a time window, and generates nuclear medicine image data using the weighted coincidences to enhance image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multi-photon coincidence events are rejected to reduce random and scatter events, then image quality is improved, but true coincidence events are lost and NECR decreases

Engineering Contradiction:

Improveimage qualityVSAvoidtrue coincidence events

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent segments multi-photon coincidence events into multiple possible two-photon coincidence pairs, evaluating each pair independently rather than rejecting the entire multi-photon event. This allows selective acceptance of true coincidences while filtering out random and scatter events through individual pair evaluation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different evaluation criteria to different pairs within multi-photon coincidence events based on their specific characteristics (energy, timing, spatial distribution). Each pair is assessed locally to determine if it represents a true coincidence, rather than applying a uniform rejection rule to all multi-photon events.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If all multi-photon coincidence events are accepted to increase NECR, then true coincidence events are retained, but random and scatter events increase and image quality degrades

Engineering Contradiction:

Improvetrue coincidence eventsVSAvoidimage quality

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent converts the previously harmful multi-photon coincidence events (which caused increased random and scatter events when accepted) into beneficial data sources by evaluating individual two-photon pairs within them. This transformation allows extraction of true coincidences while filtering out noise, turning a problematic event type into a useful signal source.

Inventive Principle:

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

3Measurement precision

If hardware coincidence circuitry with strict criteria is used to identify true coincidences, then random and scatter events are reduced, but multi-photon coincidence events are rejected and NECR decreases

Engineering Contradiction:

Improvecoincidence identification accuracyVSAvoidcoincidence events

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent replaces static hardware coincidence circuitry with fixed criteria with a dynamic software-based evaluation system that can adaptively assess each coincidence pair based on multiple parameters (energy, timing, spatial distribution). This dynamic approach allows flexible discrimination of true coincidences from random and scatter events without rigid rejection rules.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent substitutes hardware coincidence circuitry with a software-based evaluation method that processes coincidence events through computational algorithms. This replacement enables more nuanced evaluation of multi-photon events by considering multiple characteristics of each pair rather than relying on fixed hardware thresholds.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method effectively increases the noise equivalent count rate (NECR) by identifying and selecting true coincidences, resulting in improved nuclear medicine image data with enhanced image quality and reduced noise.

Implementation Method 1

an acquisition unit configured to acquire gamma ray detection data of an object

Methodology Applied

Scientific EffectGamma ray detection: Absorption (EM radiation)

Implementation Method 2

a determination unit configured to determine the weight of each of multiple coincidences based on three or more of events detected within a first time window, in the gamma ray detection data

Methodology Applied

Scientific EffectTime window filtering:

Implementation Method 3

a generation unit configured to generate first nuclear medicine image data based on the weight

Methodology Applied

Scientific EffectWeighted coincidence reconstruction:

Data Source

PatentEP4075168A1Nuclear medicine diagnosis device and nuclear medicine image data generation method

Publication Date: 2022.10.19 CANON MEDICAL SYST CORP

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Figure 2B

AI summary

A nuclear medicine diagnosis device according to an embodiment includes an acquisition unit 770a, a determination unit 770b, and a generation unit 770c. The acquisition unit 770a acquires gamma ray detection data of an object. The determination unit 770b determines the weight of each of multiple coincidences based on three or more of events detected within a first time window, in the gamma ray detection data. The generation unit 770c generates first nuclear medicine image data based on the weight.