PET Detector Ring Tracking for Subject Motion During Imaging
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Solution Overview
Problem
Body part specific PET apparatus face challenges in subject positioning, long measurement times, high invasiveness, and data loss due to subject motion outside the detector ring's axial field of view, necessitating additional devices like cameras for motion correction.
Innovation Solution
A PET apparatus with a detector ring, position adjustment unit, processing unit, and control unit that adjusts the detector ring's position based on coincidence detection events to keep the subject within the axial field of view without requiring additional cameras, using the subject's motion data from gamma-ray detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the detector ring size is reduced for body part specific PET apparatus, then cost is reduced, but the degree of difficulty of adjustment of subject position increases and requires skill
Solution Approach 1:
The system automatically tracks the subject's position using coincidence detection events from the detector ring itself, eliminating the need for manual positioning adjustments by operators. The position adjustment unit autonomously moves the detector ring to maintain the subject within the field of view, making the system self-sufficient regarding position management.
Solution Approach 2:
The patent replaces manual mechanical positioning adjustments with an automated system that uses coincidence detection data to trigger position adjustments. The control unit processes detection events and automatically controls the position adjustment unit, substituting operator skill with an automated control system.
2Measurement precision
If body restraint is performed on the subject to prevent movement during measurement, then measurement precision is improved, but invasiveness increases and measurement time increases
Solution Approach 1:
Instead of restraining the subject to maintain position, the system inverts the approach by allowing the subject to move freely while automatically adjusting the detector ring position to track the subject. This reverses the conventional strategy of fixing the subject and instead fixes the detector ring to the moving subject.
Solution Approach 2:
The system transitions from a static measurement setup to a dynamic one where the detector ring continuously adjusts its position to follow the subject's movement. The position adjustment unit operates in real-time during measurement, making the system adaptable to subject motion rather than restrictive of it.
3Measurement precision
If body restraint is performed on the subject to prevent movement during measurement, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The system maintains continuous measurement capability by dynamically adjusting the detector ring position throughout the measurement process. Instead of requiring the subject to remain stationary for the entire measurement duration, the system continuously adapts to maintain optimal positioning, allowing measurement to proceed without interruption despite subject movement.
4Ease of operation
If the subject is allowed to move without body restraint, then ease of operation is improved, but data loss occurs when the subject goes out of the axial field of view
Solution Approach 1:
The system uses coincidence detection events as feedback to continuously monitor the subject's position relative to the detector ring. The processing unit analyzes the detection events to determine subject position, and the control unit uses this information to trigger position adjustments when the subject approaches the edge of the field of view, creating a closed-loop control system that prevents data loss.
Solution Approach 2:
The system performs preliminary position adjustments based on detected subject position changes before the subject completely exits the field of view. By continuously monitoring and proactively adjusting the detector ring position, the system prevents the subject from going out of view rather than reacting after data loss has occurred.
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
Enables motion-allowing measurements without body restraint, preventing data loss and measurement failure, applicable to both whole body and body part specific PET apparatus.
Implementation Method 1
a coincidence detection event in which any two radiation detectors out of the plurality of radiation detectors detect a pair of gamma-rays generated by a positron which is emitted from the RI source in the subject
Implementation Method 2
a drug which is labeled with a positron emitting radioisotope (an RI source) is injected
Implementation Method 3
a pair of gamma-rays generated by a positron which is emitted from the RI source in the subject
Data Source
AI summary
A PET apparatus includes a detector ring, a processing unit, a position adjustment unit, and a control unit. The position adjustment unit adjusts a position of the detector ring by moving the detector ring relative to a subject in a body axis direction. The processing unit repeatedly obtains and outputs a position or a position change amount of the subject relative to the detector ring based on a coincidence detection event in which any two radiation detectors out of a plurality of radiation detectors in the detector ring detect a pair of gamma-rays. The control unit instructs the position adjustment unit to adjust the position of the detector ring such that the subject is positioned within a predetermined range in the body axis direction in the measurement space based on the position or the position change amount of the subject output from the processing unit.