Rotating CT X-ray Tube HVL Measurement Step-Wedge
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Solution Overview
Problem
Measuring the half-value layer (HVL) in CT scanners is challenging due to the requirement of 'parking' the x-ray tube, which is typically only accessible to service engineers, making routine HVL measurements difficult and inefficient.
Innovation Solution
A cylindrical 'step-wedge' device with increasing attenuating material thicknesses is used, allowing HVL measurement without stopping the x-ray tube, by positioning it centered on the x-ray tube's axis of rotation and advancing it incrementally during rotation, enabling direct measurement of effective energy absorption coefficients and subsequent calculation of HVL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the x-ray tube is parked (stopped) to measure HVL, then measurement accuracy is improved, but device complexity and operational difficulty increase
Solution Approach 1:
The patent transforms the static measurement approach (requiring tube parking) into a dynamic measurement approach where the detector rotates with the x-ray tube. This allows HVL measurements to be performed during normal tube rotation, eliminating the need to park the tube and making the measurement process accessible to routine users rather than requiring service engineer intervention.
Solution Approach 2:
The patent introduces a rotating detector as an intermediary element between the x-ray source and the measurement process. This detector rotates synchronously with the x-ray tube and collects attenuation data throughout the rotation, enabling accurate HVL measurement without interrupting the tube's normal operation and without requiring complex external measurement setups.
2Measurement precision
If serial measurements are made with multiple aluminum sheets, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent implements continuous measurement during the entire x-ray tube rotation cycle. The detector continuously records attenuation data at multiple angles and through multiple aluminum sheet thicknesses in a single uninterrupted rotation, eliminating the need for repeated serial measurements and significantly reducing the total measurement time while maintaining precision.
Solution Approach 2:
The patent performs all necessary attenuation measurements for multiple aluminum sheet thicknesses in advance during a single tube rotation. The rotating detector collects data for 0mm, 2mm, 4mm, 6mm, and 8mm aluminum sheets simultaneously throughout the rotation, so that all HVL calculation requirements are satisfied in one measurement cycle rather than requiring sequential measurements.
3Measurement precision
If the radiation meter is positioned 30-50 cm away from the attenuating material, then scatter radiation interference is reduced, but measurement complexity increases
Solution Approach 1:
The patent merges the detector positioning with the x-ray tube rotation mechanism. Instead of requiring a separate, fixed-position radiation meter positioned 30-50 cm from the attenuating material, the detector is integrated into the rotating assembly and moves with the tube, simplifying the measurement setup while maintaining scatter rejection through rotational averaging of the attenuation data.
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 efficient and cost-effective routine HVL measurements in CT scanners, allowing for early detection of equipment issues and improved patient dosimetry calculations, reducing the need for Monte Carlo simulations.
Implementation Method 1
The penetrating ability of photons is one of the characteristics of x-ray radiation that make them useful for medical imaging. Photons directed at an object are either attenuated by the object, completely absorbed, or scattered.
Implementation Method 2
Photons directed at an object are either attenuated by the object, completely absorbed, or scattered.
Implementation Method 3
Photon absorbing and filtering materials can preferentially remove lower-energy x-ray photons emitted by the x-ray source and thereby filter the beam.
Data Source
AI summary
Certain embodiments are directed to devices useful for determination of HVL or the QVL of an x-ray source. The device includes an elongated radio-opaque cylindrical body having an incremental or continuous decrease in circumference.