Back-Illuminated Sensor for Low-Dose Dental X-Ray Imaging

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Solution Overview

Problem

Current dental and medical imaging technologies, such as intraoral and extraoral x-ray systems, PET/SPECT scans, face challenges in reducing radiation doses due to the reflection of light at the wiring layer in front-illuminated sensors, leading to decreased quantum efficiency and the need for increased radiation doses and larger pixel sizes.

Innovation Solution

The implementation of a back-illuminated sensor configuration where the light passes directly to the photocathode layer without going through the wiring layer, enhancing quantum efficiency and allowing for smaller pixel sizes and improved spatial resolution, as demonstrated by the use of a microlens array and thinned silicon wafers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a front-illuminated sensor configuration is used, then manufacturing is simplified, but quantum efficiency decreases due to light reflection at the wiring layer

Engineering Contradiction:

Improvesensor manufacturing simplicityVSAvoidquantum efficiency

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent inverts the traditional sensor illumination direction by using back-illuminated sensors where light enters through the back surface of the sensor chip, passing through the photocathode layer before reaching the wiring layer. This inversion eliminates the problem of light reflection at the wiring layer, significantly improving quantum efficiency while maintaining manufacturing feasibility through established back-illumination fabrication processes

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If front-illuminated sensors are used, then the active matrix can be placed on the front surface, but pixel size must be increased to compensate for reduced light capture

Engineering Contradiction:

Improvematrix placement simplicityVSAvoidpixel size

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

By inverting the sensor illumination direction to back-illuminated configuration, the patent allows the active matrix to remain on the front surface while light enters through the back, passing through the photocathode layer first. This eliminates the need to increase pixel size to compensate for light loss, maintaining both manufacturing simplicity and small pixel dimensions for high spatial resolution

Inventive Principle:

Principle #13The other way round (Inversion)

3Object-affected harmful factors

If low milliamperage settings are used, then radiation dose is reduced, but image quality deteriorates due to insufficient light signal

Engineering Contradiction:

Improveradiation doseVSAvoidimage quality

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The patent converts the previously harmful effect of light reflection at the wiring layer into a beneficial configuration by using back-illuminated sensors. This eliminates signal loss and actually enhances the already weak light signal from low-mA x-ray exposure, allowing reduced radiation dose while maintaining or improving image quality through the increased quantum efficiency of the back-illuminated detector

Inventive Principle:

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

Solution Approach 2:

The patent introduces a reflective layer as an intermediary element in the back-illuminated sensor configuration. This reflective layer, positioned behind the photocathode layer, redirects photons that would otherwise be lost through the substrate back toward the photocathode, enhancing light capture efficiency and improving image quality at low radiation doses

Inventive Principle:

Principle #24Intermediary (Mediator)

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 significantly reduces radiation dosage and improves image resolution by increasing the fill factor and quantum efficiency, enabling lower milliamperage settings while maintaining image quality, thus addressing the limitations of traditional front-illuminated systems.

Implementation Method 1

transforming the beam that is received into light

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

collecting and converting the light into electrical signals representative of digital images

Methodology Applied

Scientific EffectPhotoemission: Photoelectric Effect

Data Source

PatentUS10849586B2Low-dose x-ray imaging system

Publication Date: 2020.12.01 REAL TIME IMAGING TECHNOLOGIES LLC

AI summary

A back illuminated sensor preferably is included as a collector component of a detector for use in intraoral and extraoral 2D and 3D dental radiography, positron emission tomography (PET) and single-photon emission computed tomography (SPECT). The disclosed imaging method includes one or more intraoral or extraoral emitters for emitting a low-dose gamma ray or x-ray beam through a dental examination area; and one or more intraoral or extraoral detectors for receiving the beam, each detector including a back illuminated sensor. Within the detector, the beam preferably is converted into light and then focused and collected at a photocathode layer without passing through the wiring layer of the back illuminated sensor.