PET-CT Image Alignment via Couchtop Sag Correction
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Solution Overview
Problem
Conventional medical image diagnosis apparatuses, such as PET-CT systems, face precision issues due to positional gaps between images taken using different image acquisition methods, like step-and-shoot and helical scanning, caused by couchtop sagging under patient weight, leading to inaccurate attenuation correction and fusion image interpretation.
Innovation Solution
The PET-CT apparatus incorporates a correcting unit with position calculating, revising, estimating, and correction processing units to align images by calculating couchtop positions in X-ray CT images and estimating them in PET images, using gradients and correction amounts to adjust image positions and correct gaps, thereby maintaining image precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different image taking methods (step-and-shoot and helical scanning) are used for PET and X-ray CT imaging, then functional and morphological information can be obtained, but positional gaps occur between images due to couchtop sagging
Solution Approach 1:
The system performs preliminary actions by calculating the couchtop position in X-ray CT images and estimating the corresponding positions in PET images before fusion. The correction amounts are computed in advance based on the relationship between couchtop positions and image data, allowing subsequent precise alignment without real-time mechanical adjustment.
Solution Approach 2:
The couchtop position serves as an intermediary parameter that links X-ray CT and PET image spaces. By using the couchtop position relationship as a mediator, the system establishes correspondence between images taken by different methods, enabling accurate fusion despite positional gaps caused by sagging.
2Measurement precision
If couchtop sagging is corrected by mechanical adjustment, then image alignment improves, but imaging time and system complexity increase
Solution Approach 1:
The system replaces mechanical adjustment of the couchtop with computational correction. Instead of physically adjusting the couchtop position during or after imaging, the invention uses image processing techniques to calculate correction amounts based on couchtop position relationships, thereby eliminating time-consuming mechanical interventions.
Solution Approach 2:
The system creates a virtual model of the couchtop position relationship from X-ray CT images and applies this copied positional information to correct PET images. By working with digital copies and calculations rather than physical adjustments, the method maintains precision while reducing imaging time.
3Productivity
If couchtop position is not corrected, then imaging process remains simple and fast, but attenuation correction and fusion image interpretation become inaccurate
Solution Approach 1:
The system performs preliminary calculation of correction amounts based on couchtop positions in X-ray CT images before conducting PET image correction. This preliminary action ensures that accurate attenuation correction is applied without requiring time-consuming iterative adjustments during the imaging process.
Solution Approach 2:
The system uses feedback from the calculated couchtop position relationship to automatically determine correction amounts for PET images. This feedback mechanism ensures that attenuation correction accuracy is maintained by continuously referencing the established positional relationship between imaging modalities.
Data Source
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AI summary
In an embodiment, an image diagnosis apparatus includes a first image taking device that takes an image of a patient placed on a couchtop by using an X-ray emission; a second image taking device that takes images in positions by moving an image taking position of the patient by a predetermined distance at a time, along the body-axis direction; a position estimating unit (46c); and a correction processing unit (46d). The position estimating unit (46c) estimates a couchtop position for each of the image taking positions of the second image taking device, based on information about warping of the couchtop of the first image taking device. The correction processing unit (46d) uses information about the couchtop positions estimated by the position estimating unit (46c), for performing a position correcting process on the images obtained by the image taking devices.