Liquid Xenon Argon Positron Detector for Hadrotherapy
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Solution Overview
Problem
Current positron emission tomography (PET) and Time Of Flight (TOF-PET) units have limited radial resolution, high tracer doses, poor image contrast and brightness, and inefficient γ-ray detection due to sub-optimal scintillators and detectors, leading to increased radiation exposure, especially in pediatric patients, and inability to accurately monitor dose delivery to cancer cells versus healthy tissues.
Innovation Solution
A detector unit with a hollow body containing a scintillating material like liquid argon or xenon with fast decay time, high atomic number, and high scintillation yield, paired with photo-detecting units and shielding to enhance radial resolution and Signal-to-Noise Ratio, allowing for reduced tracer doses and improved image clarity, and integration with hadrotherapy machines for precise dose monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic scintillators (LSO, LYSO) are used in commercial TOF-PET units, then detection sensitivity is improved, but radial resolution deteriorates to a few cm due to slow scintillation decay times (40-80 ns)
Solution Approach 1:
The patent changes the key parameter of scintillation decay time from 40-80 ns (inorganic scintillators) to less than 10 ns (liquid scintillators), enabling both high detection sensitivity and excellent radial resolution (4-5 mm) to be achieved simultaneously
2Loss of information
If tomographic reconstruction is used to produce three-dimensional images, then image completeness is improved, but radiation dose increases due to the need for high tracer activity (10 mCi, 12 mSv per procedure)
Solution Approach 1:
The patent replaces the indirect tomographic reconstruction method with direct three-dimensional imaging capability, allowing complete spatial information to be obtained without requiring high tracer activities, thereby reducing radiation dose to patients
3Reliability
If inorganic scintillators with thick crystals are used, then gamma-ray detection efficiency is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent uses liquid scintillators (fluid state) instead of solid inorganic scintillator crystals, simplifying the detector structure while maintaining high gamma-ray detection efficiency through the fluid's ability to fully contain interaction volumes
Data Source
AI summary
Disclosed is a detector for a positron imaging unit, comprises a hollow body with an inner cylindrical wall and an outer wall spaced apart from the inner cylindrical wall. The hollow body includes a scintillating material, suitable to emit photons once hit by a 511 keV γ-ray, and one or more pairs of photo-detecting units (e.g. comprising PMTs or SiPM) for detecting photons emitted by the scintillating material; each photo-detecting unit of a pair being placed at opposite ends of the inner cylindrical wall along a radial direction. The scintillating material has scintillation decay time τ lower than 10 ns, an atomic number greater than 10, and a high scintillation yield greater than 8,000 photons/MeV, and comprises a mixture of xenon and argon. An imaging unit including the detector and a method to estimate the differential of the dose of radiation provided in a subject to cancer cells and to surrounding tissues in the course of hadrotherapy is also disclosed.