Medical Imaging Apparatus Motion Model Alignment
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Solution Overview
Problem
Medical imaging systems face misalignment issues due to cardiac and respiratory motions of patients, even with highly accurate spatial calibration, when fusing ultrasound and pre-operative volume images.
Innovation Solution
A medical imaging apparatus and method that utilize an ultrasound acquisition unit, image interface, position determining unit, and image processing unit to determine a motion model and align ultrasound and medical image data based on anatomical features, allowing continuous adaptation and precise alignment even during patient motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spatial calibration of the tracking system is performed to align ultrasound image data and pre-operative volume image data, then alignment accuracy is improved, but misalignment occurs due to cardiac and respiratory motions of the patient
Solution Approach 1:
The system transitions from static spatial calibration to dynamic motion compensation. A motion model is determined based on a sequence of ultrasound images and used to compensate for tissue motion during image alignment. This allows the system to adapt to changing anatomical positions caused by cardiac and respiratory motions, maintaining alignment accuracy throughout the examination.
Solution Approach 2:
The system uses a feedback mechanism where motion is detected from a sequence of ultrasound images, a motion model is determined from this detected motion, and the alignment is adjusted based on the motion model. This closed-loop approach continuously corrects for motion artifacts, ensuring reliable alignment despite patient movement.
2Measurement precision
If pre-operative image scan is performed shortly before ultrasound scan to improve calibration accuracy, then alignment precision is improved, but this is not always feasible in clinical practice
Solution Approach 1:
The system performs preliminary motion analysis by determining a motion model from a sequence of ultrasound images acquired during the examination. This motion model is then used to compensate for motion in the alignment process, allowing accurate alignment even when the pre-operative scan was performed at a different time, thus providing clinical flexibility without sacrificing precision.
3Device complexity
If rigid transformation is used for alignment between ultrasound and pre-operative volume image coordinates, then computational simplicity is maintained, but alignment accuracy deteriorates due to anatomical motion
Solution Approach 1:
The system enhances the simple rigid transformation approach by incorporating dynamic motion compensation. A motion model determined from ultrasound image sequences is applied to adjust the transformation parameters, allowing the system to maintain computational efficiency while significantly improving alignment accuracy in the presence of anatomical motion.
Data Source
AI summary
A medical imaging apparatus (10) for inspecting a volume of a subject (12) is disclosed. The medical imaging apparatus comprises an ultrasound acquisition unit (14) including an ultrasound probe for acquiring ultrasound image data of the subject, an image interface (20) for receiving medical image data of the subject, a position determining unit (30) for determining a position of the ultrasound probe. An alignment unit is provided for aligning the ultrasound image data and the medical image data based on anatomical features (32) of the subject and the detected position of the ultrasound probe and for adapting the alignment of the ultrasound image data and the medical image data based on a motion model. An image processing unit (18) is provided for processing the ultrasound image data and the medical image data to fuse the ultrasound image data and the medical image data based on the alignment to combined image data.