Cone-Beam CT Collimator for Scattered Radiation Reduction

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Solution Overview

Problem

Cone-beam computed tomography (CBCT) systems face inaccuracies due to radiation scattering, leading to artifacts, loss of resolution, and blurring in images, as radiation intended for central pixels often reaches surrounding detectors, causing errors in pixel data.

Innovation Solution

The method involves obscuring portions of the radiation source to reduce radiation scattering by limiting the cone beam's coverage to less than 85% of the pixel array, using collimators like fan blades to focus radiation on specific areas of interest, and employing truncated reconstruction methods to generate accurate three-dimensional CT data sets.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the cone beam covers the entire pixel array, then the field of view is maximized, but radiation scattering increases causing image inaccuracies

Engineering Contradiction:

Improvefield of viewVSAvoidimage accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The pixel array is divided into a first region (central area) and a second region (surrounding area). The collimator selectively blocks radiation to the second region while allowing radiation to reach the first region. This segmentation allows the system to maintain a reasonable field of view through the first region while eliminating scattered radiation effects in the second region, thereby improving image accuracy without completely sacrificing coverage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the pixel array are treated differently: the first region receives full radiation coverage for maintaining field of view, while the second region is selectively obscured to eliminate scattering effects. This local differentiation allows the system to optimize for image accuracy in the first region while preserving adequate coverage through the second region.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If collimators are used to obscure portions of the radiation source, then radiation scattering is reduced, but the field of view is limited

Engineering Contradiction:

Improveimage accuracyVSAvoidfield of view

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

Instead of obscuring the entire radiation source or using full collimation, the system applies partial obscuration only to the second region of the pixel array. This partial action is sufficient to eliminate scattered radiation effects while preserving radiation coverage for the first region, thereby achieving improved image accuracy without completely limiting the field of view.

Inventive Principle:

Principle #16Partial or excessive action

3Area of stationary object

If radiation is scattered by object components, then surrounding pixels receive erroneous signals, but using the full pixel array provides better coverage

Engineering Contradiction:

Improvedetector coverageVSAvoidpixel data accuracy

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The system extracts or removes the problematic second region from the data processing pipeline. By identifying pixels in the second region as unreliable due to scattered radiation, the system excludes these pixels from contributing to the final image reconstruction. This extraction of unreliable data ensures that only accurate measurements from the first region are used, thereby maintaining high reliability without requiring complete detector coverage.

Inventive Principle:

Principle #2Taking out (Extraction)

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 enhances image accuracy by reducing radiation scattering, improving the precision of Hounsfield units and providing higher contrast for finer details, thereby improving diagnostic capabilities in CBCT imaging.

Implementation Method 1

obscuring one or more portions of the cone beam of radiation such that direct rays of the radiation cover less than 85 percent of the area of the pixel array

Methodology Applied

Scientific EffectRadiation absorption: Absorption (EM radiation)

Implementation Method 2

a source of radiation that emits a cone-beam of radiation

Methodology Applied

Scientific EffectX-ray radiation: X-Ray

Implementation Method 3

radiation scattering, leading to artifacts, loss of resolution, and blurring in images, as radiation intended for central pixels often reaches surrounding detectors

Methodology Applied

Scientific EffectRadiation scattering: Scattering

Data Source

PatentUS8320518B2Methods, apparatus, and computer-program products for increasing accuracy in cone-beam computed tomography

Publication Date: 2012.11.27 VARIAN MEDICAL SYSTEMS INC

AI summary

Portions of the radiation source are obscured so that the radiation only passes through the specific areas of the patient related to the regions-of-interest to the doctor. Scattered radiation received by detector pixels that are obscured by direct-line of sight radiation are used to estimate the scattered radiation in the un-obscured portion, which can be used to increase the accuracy of the image taken through the un-obscured portion.