CT Image FOV Extension via Iterative Mask Reconstruction

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Solution Overview

Problem

Current methods for extending the Field of View (FOV) of Computed Tomography (CT) scans are inadequate, often resulting in truncated images and artifacts, especially when patients have larger body dimensions or are positioned off-center, which limits the accuracy of attenuation correction for PET and SPECT images.

Innovation Solution

A method and apparatus that use masks to extend the CT image beyond its original FOV by reconstructing data within an inner boundary and extrapolating it to outer regions, potentially using PET or SPECT images to determine the outer boundary, reducing computational time and improving image accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the CT scanner uses a limited FOV to reduce scan time and computational load, then productivity is improved, but measurement precision deteriorates due to truncated images and artifacts

Engineering Contradiction:

Improvescan timeVSAvoidimage accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by performing FOV extension during the image reconstruction process rather than after acquisition. The extension is integrated into the iterative reconstruction algorithm, allowing the system to prepare and extend the FOV as part of the initial image processing workflow, thus avoiding additional scan time while maintaining image accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses an intermediary approach by introducing estimated projection data as a mediator between the limited measured data and the complete image reconstruction. The extension algorithm acts as an intermediary that fills in missing projection data based on available information, enabling accurate reconstruction without requiring additional physical measurements

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the CT scanner increases FOV to capture larger body dimensions, then measurement precision is improved, but device complexity increases and scan time increases

Engineering Contradiction:

Improveimage accuracyVSAvoidscanner configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies the copying principle by creating a virtual extension of the CT FOV through computational methods rather than physically expanding the scanner geometry. The extension algorithm generates additional projection data that copies and extrapolates from the measured data, effectively creating a larger FOV without modifying the physical scanner configuration

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical approach of physically increasing FOV with a computational method. Instead of expanding the scanner's physical dimensions or detector array, the system uses mathematical algorithms to extend the FOV during reconstruction, substituting mechanical complexity with information processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If iterative reconstruction is used to extend FOV and improve image accuracy, then measurement precision is improved, but loss of time increases due to computational intensity

Engineering Contradiction:

Improveattenuation correction accuracyVSAvoidreconstruction time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies segmentation by dividing the reconstruction process into distinct phases: measured data processing, extension data generation, and combined reconstruction. The FOV extension is performed on specific regions (truncated areas) rather than the entire image, and the algorithm processes different data components separately, reducing overall computational time while maintaining accuracy

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial action by performing FOV extension only in the regions where truncation occurs rather than processing the entire image uniformly. The extension algorithm focuses computational resources on the truncated areas where additional information is needed, avoiding unnecessary computation in already-complete regions

Inventive Principle:

Principle #16Partial or excessive action

4Loss of information

If FOV extension is applied to truncated regions, then loss of information is reduced, but device complexity increases due to additional processing requirements

Engineering Contradiction:

Improvemissing transmission dataVSAvoidprocessing system

Core Design Contradiction:

Loss of informationVSDevice complexity

Solution Approach 1:

The patent applies universality by designing a reconstruction algorithm that performs multiple functions: it processes measured projection data, generates extension data for truncated regions, and performs image reconstruction all within a single integrated framework. The same computational engine handles both standard and extended FOV cases, eliminating the need for separate processing systems

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8155415B2Extension of truncated CT images for use with emission tomography in multimodality medical images

Publication Date: 2012.04.10 SIEMENS MEDICAL SOLUTIONS USA INC

AI summary

An apparatus and method for expanding the FOV of a truncated computed tomography (CT) scan. An iterative calculation is performed on the original CT image to produce an estimate of the image. The calculated estimate of the reconstructed image includes the original image center and a estimate of the truncated portion outside the image center. The calculation uses an image mask with the image center as one boundary.