C-Arm 3D Reconstruction With Absorption-Corrected Voxel Weighting
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Solution Overview
Problem
Existing X-ray imaging systems, particularly C-arms, suffer from non-uniformity in 3D image reconstruction due to varying X-ray absorption by patient and operating table, which is detrimental to image quality during minimally invasive surgeries.
Innovation Solution
A method involving a motorized C-arm with an anti-collision device to detect patient's body surface and compute a volumetric model, adjusting X-ray absorption levels for each voxel in the 3D image based on this model, ensuring uniformity by accounting for varying tissue absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If conventional cone-beam reconstruction techniques are used to obtain 3D images during surgery, then three-dimensional information becomes available, but image uniformity deteriorates due to varying X-ray absorption by patient body and operating table
Solution Approach 1:
The system performs a preliminary scanning phase before actual 3D reconstruction, where the C-arm acquires data without X-ray emission to map the patient's body surface and estimate absorption characteristics. This preliminary action allows the system to pre-calculate correction factors that compensate for varying absorption, thereby resolving the contradiction between obtaining 3D information and maintaining image uniformity.
Solution Approach 2:
The system dynamically adjusts reconstruction parameters based on the estimated absorption map. By changing the weighting parameters and correction factors applied to different X-ray beams during reconstruction, the system compensates for non-uniform absorption, thus maintaining image uniformity while preserving 3D information quality.
2Loss of information
If the C-arm rotates around the patient to acquire multiple 2D images for 3D reconstruction, then complete volumetric data is obtained, but X-ray absorption variability increases leading to non-uniform image quality
Solution Approach 1:
The system applies different correction factors and weighting parameters to different regions of the 3D volume based on local absorption characteristics. By segmenting the patient's body into regions with different absorption properties and tailoring the reconstruction parameters for each region, the system maintains uniform image quality across the entire volume despite the C-arm's rotation around the patient.
3Object-affected harmful factors
If the C-arm positioning is optimized to reduce patient irradiation, then radiation dose decreases, but detector positioning constraints increase affecting reconstruction quality
Solution Approach 1:
The system compensates for suboptimal detector positioning by dynamically adjusting reconstruction parameters such as weighting factors, correction terms, and integration weights. This allows the system to maintain high reconstruction quality even when the C-arm is positioned at angles that minimize patient irradiation, thus resolving the contradiction between radiation safety and image quality.
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
Enhances the uniformity of the reconstructed 3D medical image, improving image quality and reducing patient irradiation by optimizing detector positioning and adjusting X-ray contributions.
Implementation Method 1
at each angular position of the C-arm along said first path, detecting with the anti-collision device the external surface of the patient's body and recording volumetric data
Implementation Method 2
X-Ray imaging systems generally provide two-dimensional (2D) projection images with different anatomical structures superimposed along the path of the X-rays
Implementation Method 3
three-dimensional (3D) imaging techniques have become necessary over the past decades. Recent years have seen an increasing interest in tomographic reconstruction techniques, also known as cone-beam reconstruction techniques (CBCT)
Data Source
AI summary
The invention relates to a method for reconstructing a 3D medical image of a region of interest of a patient's body (P) lying on an operating table (200) with an X-ray imaging system comprising a motorized C-arm (100) supporting an X-ray source (101), an X-ray image detector (102) and an anti-collision device (104), comprising: —implementing a first path of the motorized C-arm without acquiring any X-ray image, said first path comprising at least two different angular positions around a rotation axis of the C-arm; —at each angular position of the C-arm along said first path, detecting with the anti-collision device (104) an external surface (S) of the patient's body and recording volumetric data of a patient's body portion enclosing the region of interest; —computing a volumetric model of the patient's body portion based on said volumetric data and on an estimation of X-ray absorption of patient's body tissues surrounding the region of interest, said volumetric model comprising a first part including the region of interest and at least one second part distinct from the first part, the first and second parts presenting different levels of X-ray absorption; —implementing a second path of the motorized C-arm and acquiring a 2D X-ray image at each angular position of the C-arm along said second path; —reconstructing a 3D medical image from the acquired 2D X-ray images, wherein said reconstructing comprises estimating, for each X-ray passing through a voxel of the 3D medical image, a level of X-ray absorption by the patient's body based on the volumetric model of the patient's body portion and adjusting a contribution of said X-ray to each voxel of the 3D medical image based on said estimated level.