Stacked Anti-Scatter Grid for Spectral CT

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Solution Overview

Problem

Current anti-scatter grids for pixel detectors have a high aspect ratio, limiting their acceptance angle and making it difficult to achieve high spectral performance, especially for photon counting spectral CT, where smaller pixel sizes and efficient absorption of scattered radiation are necessary.

Innovation Solution

A stacked anti-scatter grid assembly with a first grid of thinner lamellas and a second grid of thicker lamellas, arranged with a lateral shift, creating effective holes with smaller pitches and larger sizes, improving absorption efficiency and manufacturing ease.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a single ASG with high aspect ratio is used, then scattered radiation absorption is improved, but acceptance angle is reduced and spectral performance is limited

Engineering Contradiction:

Improvescattered radiation absorptionVSAvoidacceptance angle

Core Design Contradiction:

Object-affected harmful factorsVSLength of moving object

Solution Approach 1:

The single ASG is divided into multiple stacked ASGs with different lamella thicknesses. The first ASG has thinner lamellas (e.g., 50 μm) and the second ASG has thicker lamellas (e.g., 100 μm), creating a segmented structure that improves spectral performance while maintaining scattered radiation absorption capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from a single-plane ASG to a stacked multi-plane configuration with lateral shifts. The second ASG is laterally shifted by half the pitch relative to the first ASG, creating an extended effective hole pattern in three dimensions that increases acceptance angle while maintaining spectral discrimination

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If ASG is scaled to smaller pixel size, then spectral performance is improved, but manufacturing difficulty increases

Engineering Contradiction:

Improvespectral performanceVSAvoidfabrication difficulty

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The fine-pitch ASG requirement is segmented into two coarser-pitch ASGs stacked together. Each individual ASG can be manufactured with standard pitch dimensions, avoiding the need to fabricate a single ASG with extremely fine pitch corresponding to small pixel sizes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of reducing the pitch of a single ASG to match small pixel sizes (which is manufacturingally difficult), the invention uses two ASGs with larger pitches stacked with lateral shift. The effective hole pitch becomes smaller than either individual ASG pitch, achieving fine spectral resolution through spatial arrangement rather than fine fabrication

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of manufacture

If uniform lamella thickness is used in stacked ASGs, then manufacturing is simplified, but dose efficiency is reduced

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoiddose efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

Different regions of the stacked ASG structure have different lamella thicknesses. The first ASG has thinner lamellas optimized for reducing primary radiation absorption, while the second ASG has thicker lamellas optimized for scattered radiation absorption. This local differentiation improves dose efficiency

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The lamella thickness parameter is changed between different ASGs in the stack. By varying the thickness parameter (thinner in first ASG, thicker in second ASG), the system optimizes both dose efficiency and scattered radiation rejection performance

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 configuration enhances spectral performance by effectively absorbing scattered radiation while maintaining dose efficiency and simplifying fabrication, allowing for improved energy resolution and higher dose efficiency in CT imaging.

Implementation Method 1

Each opening in the ASG is centered above one detector pixel. The lamellas have typically a thickness of 100 μm... radiation scattered in the scanned object largely hits the ASG from other directions and is effectively absorbed before reaching the detector

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

the second grid is arranged on top of the first grid with a lateral shift in at least one lateral direction... creating effective holes with smaller pitches and larger sizes

Methodology Applied

Scientific EffectGeometric filtering:

Data Source

PatentUS11232881B2Anti-scatter grid assembly for detector arrangement

Publication Date: 2022.01.25 KONINKLIJKE PHILIPS NV

AI summary

The present invention relates to an anti-scatter grid (ASG) assembly comprising a first and a second grid, wherein the second grid is arranged on top of the first grid and comprises a lateral shift. The lamella thickness of the first grid is smaller than the lamella thickness of the second grid. The present invention further relates to a detector arrangement comprising a pixel detector and an ASG assembly arranged on top of the pixel detector.