Cross-Calibration for Functional Imaging Accuracy

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Solution Overview

Problem

Current methods for quantitative functional imaging, such as PET and SPECT, face inaccuracies due to detector sensitivity and dose variability, making it challenging to provide accurate activity concentration and uptake values, especially when using isotropic point sources with anisotropic factory-calibrated sealed sources.

Innovation Solution

The method involves cross-calibration by measuring system-specific sensitivity to a factory-calibrated long-lived point source and a liquid radiotracer source, calculating a cross-calibration factor to correct the injected dose and activity concentration, and using this factor to estimate accurate uptake values, thereby reducing variability from detector and dose sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If class standard sensitivity is used for detector calibration, then the calibration process is simplified, but the activity concentration measurements become inaccurate due to detector specific sensitivity variations

Engineering Contradiction:

Improvecalibration process simplicityVSAvoidactivity concentration accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by transitioning from using class standard sensitivity values to using system-specific sensitivity values measured for each individual detector. The method measures the actual sensitivity of each detector to long-lived point sources and uses these measured parameters in the reconstruction algorithm, thereby adapting the calibration parameters to match the specific characteristics of each detector system and improving measurement accuracy.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If factory calibrated sealed sources are used for sensitivity measurement, then the calibration is standardized, but inaccuracies arise due to anisotropy of sealed sources versus isotropic liquid radiotracer distribution

Engineering Contradiction:

Improvecalibration standardizationVSAvoiduptake value accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary correction approach by using long-lived point sources as intermediaries for calibration. The method measures system-specific sensitivity using these point sources and then applies correction factors to account for the differences between point source geometry and actual liquid radiotracer distribution in patients. This intermediary calibration approach bridges the gap between standardized calibration sources and clinical reality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the calibration parameter approach by measuring system-specific sensitivity to long-lived point sources and using these measured values instead of relying on manufacturer-provided sensitivity values. The method also incorporates correction for attenuation and scatter specific to each patient scan, dynamically adjusting parameters to improve uptake quantification accuracy.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If dose value from dose calibrator is used directly, then the dosing process is straightforward, but inaccuracies in injected dose propagate to uptake calculations

Engineering Contradiction:

Improvedosing process simplicityVSAvoiduptake value accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements feedback by using the measured system-specific sensitivity values to correct the injected dose information. The method incorporates the actual detector response to the specific radiotracer and geometry into the reconstruction process, creating a feedback loop where measured system characteristics are used to adjust and correct the quantitative results, thereby compensating for initial dosing inaccuracies.

Inventive Principle:

Principle #23Feedback

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 accurate activity concentration and uptake values by eliminating camera and dose calibrator variability, allowing for comparable quantitative measures across different scans and patients, focusing on metabolic changes rather than detector or dose-related variance.

Implementation Method 1

The emissions from the radiotracer are detected in the functional imaging

Methodology Applied

Scientific EffectGamma emission detection: Absorption (EM radiation)

Implementation Method 2

Functional imaging uses a radioisotope or radiotracer to determine metabolic function within a patient

Methodology Applied

Scientific EffectRadioactive decay: Radioactive Decay

Data Source

PatentUS10588582B2Cross-calibration for quantitative functional imaging

Publication Date: 2020.03.17 SIEMENS MEDICAL SOLUTIONS USA INC

AI summary

Cross-calibration is provided for functional imaging. In PET or SPECT, the inaccuracies from the dose and detector sensitivity may be reduced or removed in both activity concentration and uptake. By using measures from both the radiotracer for the patient and factory calibrated sources, the variability due to dose may be removed. In SPECT, a measurement of system specific sensitivity to a factory calibrated point source is used to improve the accuracy of uptake values, not just activity concentration.