Radiographic Apparatus Respiration Synchronization
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Solution Overview
Problem
Cone beam computed tomography (CBCT) scanners face image degradation and artifacts due to patient movement, particularly during respiration and cardiac cycles, leading to increased radiation exposure without improved image quality or acquisition time with higher frame rates.
Innovation Solution
A radiographic apparatus with a controlled radiation beam and detector system that selects images at specific phases of the breathing cycle, activating the beam at a frequency between 0.5 and 5 Hertz, ideally matching the breathing cycle frequency, to minimize image discard and radiation dose.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the frame rate is increased to collect more images in a shorter time, then the acquisition time is reduced, but the number of images discarded by the selection algorithm increases, resulting in no improvement in image quality and increased radiation dose
Solution Approach 1:
The patent applies periodic action by synchronizing the radiation beam activation with the periodic breathing cycle of the patient. The beam is activated at specific phases of the breathing cycle (e.g., end-inspiration or end-expiration) rather than continuously or at high frame rates. This periodic synchronization ensures that images are acquired only when the patient is at a stable anatomical phase, minimizing motion artifacts and reducing the number of discarded images while maintaining image quality and reducing radiation exposure.
2Measurement precision
If the frame rate is increased to obtain more images, then the number of available images increases, but the number of images discarded by the selection algorithm increases, resulting in no improvement in image quality
Solution Approach 1:
The system uses periodic action by activating the radiation beam at specific phases of the breathing cycle, ensuring that only images acquired at stable anatomical phases are collected. This approach maximizes the utility of each acquired image by synchronizing with the physiological cycle, thereby improving image quality without increasing the total number of images needed, as each acquired image is more likely to be usable.
Solution Approach 2:
The system employs self-service by using the image content itself to determine the breathing phase and select appropriate images for reconstruction. The algorithm automatically identifies images acquired at the desired phase (e.g., end-inspiration) based on anatomical features within the images, eliminating the need for external respiratory monitoring equipment and automatically discarding images from incorrect phases, thus improving image quality through intelligent selection.
3Measurement precision
If the beam is activated at a frequency between 0.5 and 5 Hertz corresponding to 6-10 times the breathing cycle frequency, then images can be selected at like points in the cycle, but the system complexity increases
Solution Approach 1:
The system uses self-service by leveraging the image content itself to determine the breathing phase and synchronize subsequent acquisitions. The algorithm automatically identifies characteristic anatomical positions (such as the diaphragm or lung boundaries) in the acquired images to infer the breathing phase, eliminating the need for complex external respiratory monitoring systems. This self-determined synchronization achieves high positional verification accuracy while keeping the control system relatively simple.
Data Source
AI summary
For Respiration Correlated Cone Beam CT scanning, we have observed that improvements in the frame rate are in fact undesirable. We therefore propose a radiographic apparatus comprising a beam of radiation and a detector therefor, adapted to obtain a two dimensional image of the beam after passing through a cyclically varying object to be investigated, a processor adapted to review the images and select images at like points in the cycle, and a control means for the beam of radiation adapted to activate the beam periodically. The control means can activate the beam at a frequency of between 0.5 and 5 Hertz, more preferably between 1 and 3 Hertz, which corresponds (roughly) to a frequency that is between 6 and 10 times the frequency of the cyclical variation. It will assist if the selected point of the cycle is an extremity thereof, as the rate of change in these areas is at a minimum. Thus, slight mismatches between the two cycles will then have only a small effect. Typically, the object will be a patient and the cyclical variation will be the patient's breathing cycle.