Direct Conversion X-ray Detector Leakage Current Compensation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Direct-conversion detectors for SPCCT suffer from count instability due to changing background currents caused by charge injection, leading to image artefacts and limiting the selection of sensor samples based on maximum current capacity, which increases cost.

Innovation Solution

A combined passive and active leakage current compensation system for direct conversion X-ray detectors, where passive leakage current compensation (pLCC) and active leakage current compensation (aLCC) are applied simultaneously to increase the maximum total current that can be compensated, allowing the use of CZT crystals with higher dark currents and reducing detector cost.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If only active leakage current compensation (aLCC) is used to compensate for dark current, then the system is ready for measurement immediately without calibration, but the maximum current capacity is limited and reduces the range of usable sensor samples

Engineering Contradiction:

Improvereadiness for measurementVSAvoidrange of usable sensor samples

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The compensation system is segmented into two independent parts: pLCC for dark current compensation and aLCC for background current compensation. This segmentation allows each circuit to be optimized for its specific function and enables the use of sensor samples with higher dark currents that would be incompatible with aLCC-only systems.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent merges pLCC and aLCC circuits into a single detector system, allowing both compensation mechanisms to operate simultaneously. This combination enables the system to handle both dark current and background current effectively, expanding the range of usable sensor samples.

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If passive leakage current compensation (pLCC) is used to compensate for dark current, then the maximum total current capacity increases, but a calibration procedure is required before measurements

Engineering Contradiction:

Improvemaximum total current capacityVSAvoidcalibration time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The pLCC circuit performs preliminary compensation of dark current during a calibration phase before measurements begin. This preliminary action establishes a stable baseline and allows the system to handle higher total currents during subsequent measurements without requiring repeated calibration.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the maximum current capacity is limited by aLCC, then sensor specification requirements are stricter and CZT sensor cost increases, but using higher dark current CZT samples would reduce cost

Engineering Contradiction:

Improvesensor costVSAvoidcount stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

By segmenting the compensation function into pLCC and aLCC, the system can use sensor samples with higher dark currents that would be rejected by aLCC-only systems. This relaxation of sensor specifications lowers CZT sensor cost while maintaining count stability through combined compensation.

Inventive Principle:

Principle #1Segmentation

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 combined compensation system enhances the range of current compensation, enabling the use of higher dark current CZT crystals, thereby reducing detector cost and improving image stability by minimizing noise and simplifying baseline restoration.

Implementation Method 1

a passive leakage current compensation circuit comprising a first current source for generating a dark-current compensation current

Methodology Applied

Scientific EffectElectrical current generation:

Implementation Method 2

an active leakage current compensation circuit comprising a second current source (40) for generating a background-current compensation current

Methodology Applied

Scientific EffectElectrical current generation:

Implementation Method 3

charge generated by the conversion X-ray photons into electron-hole pairs

Methodology Applied

Scientific EffectDirect conversion of X-ray photons to charge: Photoelectric Effect

Data Source

PatentEP4575585A1Direct conversion x-ray detector

Publication Date: 2025.06.25 KONINKLIJKE PHILIPS NV

Figure 1
Figure 2
Figure 3

AI summary

A system processes a pixel signal received from a direct conversion X-ray detector. An output signal is generated by an analog front end comprising an amplifier circuit representing the pixel signal. A passive leakage current compensation circuit comprises a first current source for generating a dark-current compensation current and injecting the dark-current compensation current to the input of the amplifier. An active leakage current compensation circuit comprises a second current source for generating a background-current compensation current and injecting the background-current compensation current to the input to the amplifier. By combining active and passive baseline compensation at the same time, compensation is possible over a wider range, and a lower cost detector with larger baseline current can be used.