Variable-Speed TDS Imaging for Undistorted X-Ray Raster Scans
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Solution Overview
Problem
Current bone densitometers face challenges in acquiring accurate patient anatomy images due to the limitations of frame-based data acquisition methods, which result in wasted x-ray dose and longer scan times during acceleration and deceleration phases, leading to mechanical vibrations and suboptimal image quality.
Innovation Solution
Implementing a time-delayed summation (TDS) method that adapts to variable scan speeds by synchronizing data acquisition with the motion of the x-ray source and detector, ensuring consistent pixel size and signal normalization, allowing data capture during acceleration and deceleration phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If frame-based data acquisition methods are used with constant scan speed, then data acquisition is straightforward and image formation is simple, but x-ray dose is wasted during acceleration and deceleration phases and scan times are prolonged
Solution Approach 1:
The patent applies dynamics by making the TDS shift frequency variable rather than constant. The system dynamically adjusts the shift frequency based on the instantaneous scan speed, allowing data acquisition during acceleration and deceleration phases while maintaining proper image formation. This resolves the contradiction by enabling dose-efficient variable speed scanning without overwhelming complexity.
Solution Approach 2:
The patent changes the parameter of TDS shift frequency from a fixed constant to a variable parameter that adapts to scan speed changes. By modifying this key parameter, the system can utilize data from all scan phases including acceleration and deceleration, thereby reducing wasted x-ray dose without requiring complete redesign of the acquisition system.
2Productivity
If acceleration and deceleration times are minimized to reduce wasted dose, then scan efficiency improves, but mechanical vibrations increase and image quality degrades
Solution Approach 1:
The patent implements feedback by using the actual measured scan speed to determine the appropriate TDS shift frequency. The system continuously monitors scan speed and adjusts the shift frequency accordingly, creating a closed-loop control that allows efficient acceleration and deceleration profiles while maintaining image quality by compensating for speed variations in real-time.
3Productivity
If variable scan speeds are used to reduce scan time and improve patient comfort, then productivity increases, but image pixel size consistency becomes difficult to maintain
Solution Approach 1:
The patent maintains pixel size consistency during variable speed scanning by dynamically adjusting the TDS shift frequency parameter. This parameter change ensures that the relationship between detector pixel motion and signal integration remains consistent, preserving image geometric accuracy even as scan speed varies to improve productivity and patient comfort.
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
This approach reduces wasted x-ray dose, shortens scan times, improves image quality, and enhances patient comfort by utilizing data from variable speed regions, enabling smoother acceleration profiles and reducing mechanical vibrations.
Implementation Method 1
Detector pixels integrate charge from absorbed x-rays during short time intervals
Implementation Method 2
an x-ray source that emits a collimated beam of dual-energy x-rays
Data Source
AI summary
TDS (Time-Delayed Summation) acquisition systems and methods may be used within various imaging device and systems, such as a densitometry system with highly pixelated 2-D detectors and compact x-ray fan beam that scans patients in a rastering pattern across the patient axis. An improved system and method is described for extending the usability of TDS data on each transverse sweep of the scan, by acquiring data when the scan speed is variable. In this method, the TDS shift strobe signal is no longer a constant periodic function. Instead the time between strobes is dependent on the scan velocity and the strobe sequence is generated to provide constant sampling distance between strobes. Thus, the TDS shift sequence insures a constant image pixel size, enabling undistorted images despite the variable speed occurring during the signal summation.