Single-Ended PET Readout Using Light-Absorbing Coating for DOI Extraction

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Solution Overview

Problem

Current positron emission tomography (PET) systems face challenges in extracting depth of interaction (DOI) information for high-resolution imaging, particularly in small animal or organ-specific imaging, where photons enter scintillation crystals at oblique angles, requiring complex and costly dual-ended readout methods.

Innovation Solution

A single-ended readout method using a light absorbing coating on one end of the scintillation crystal to modulate pulse height based on photon depth of interaction, allowing DOI extraction with existing PET system designs and reducing the need for dual photodetectors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If dual-ended readout methods are used to extract DOI information, then measurement precision of DOI is improved, but device complexity and cost increase

Engineering Contradiction:

ImproveDOI measurement precisionVSAvoiddual photodetector system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts DOI information from a single photodetector signal by analyzing the relationship between pulse height and interaction depth. Instead of using two photodetectors (dual-ended readout), the method extracts the necessary depth information from the pulse height characteristics of a single photodetector, thereby reducing device complexity while maintaining DOI measurement capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces light absorbing coatings as an intermediary element applied to the scintillation crystal. These coatings modulate the light signal based on the depth of photon interaction, creating a relationship between pulse height and DOI that can be measured with a single photodetector. The coating acts as a mediator that encodes depth information into the pulse height signal

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If dual-ended readout methods are used to extract DOI information, then DOI detection capability is improved, but manufacturing cost increases

Engineering Contradiction:

ImproveDOI detection capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses light absorbing coatings that can be applied to the scintillation crystal surface. These coatings are relatively simple and inexpensive materials that can be applied through standard coating techniques, replacing the need for expensive dual photodetector assemblies while achieving comparable DOI detection performance

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Area of stationary object

If photons enter scintillation crystals at oblique angles, then imaging coverage is improved, but DOI extraction accuracy deteriorates

Engineering Contradiction:

Improveimaging coverage areaVSAvoidDOI extraction accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent applies light absorbing coatings with specific properties to the scintillation crystal surface. These coatings have localized light-absorbing characteristics that create a relationship between pulse height and interaction depth. The local quality of the coating (its light-absorbing property) enables DOI extraction by modulating the light signal based on interaction depth, which works effectively even for obliquely incident photons

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the optical parameters of the scintillation crystal surface by applying light absorbing coatings. This modification alters the light propagation and absorption characteristics, creating a pulse height signal that is sensitive to interaction depth. The parameter change in the surface optical properties enables DOI extraction capability that works for various photon incident angles

Inventive Principle:

Principle #35Parameter changes

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

This approach provides cost-effective DOI detection compatible with standard PET systems, improving image spatial resolution and reducing complexity, while maintaining acceptable DOI resolution performance.

Implementation Method 1

A single-ended readout method using a light absorbing coating on one end of the scintillation crystal to modulate pulse height based on photon depth of interaction

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

photons enter scintillation crystals at oblique angles

Methodology Applied

Scientific EffectScintillation: Scintillation

Data Source

PatentUS8993971B2High resolution positron emission tomography

Publication Date: 2015.03.31 THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIV

AI summary

A method for extracting photon depth of interaction information in a positron emission tomography system is provided. A pulse is detected in a photodetector. A height of the pulse is measured. A determination of whether the pulse height is within a set range is made. Photon depth of interaction is extracted from the pulse height. An energy of interaction is calculated from the pulse height and calibration data. The extracted photon depth and calculated energy spectrum are used in image reconstruction.