Product Development
On this page:
- Technology Overview
- Dosimeter Research and Technology
- X-ray Storage Phosphor Research and Technology
- Patents
Technology Overview
The technology of imaging plates involves the exposure of an object to ionising radiation (e.g. X-rays, gamma-rays, neutrons) where an image is created on the plate by the excitation of electrons and holes that become trapped. The image is read-out at a later time by exposure to a scanning laser spot and the optically stimulated luminescence (OSL) is detected. To accommodate the readout delay, the image must remain stable and free of thermal fading for times preferably of the order of hours.
A similar technology is used in OSL dosimeters. However, in this case the trapped electrons and holes must remain trapped for periods that exceed 30 days. The density of trapped electrons and holes is proportional to the dose. The dose can also be reset by optical bleaching.
Scintillators are used for immediate and real-time radiation imaging (e.g. dual energy X-ray scanners for security screening of baggage, positron emission tomography for medical imaging). The technology involves radiation being converted to light in the scintillator and the light is detected (e.g. by a CCD array, photomultiplier array, etc.). The potential applications include border security (e.g. imaging of packages and containers), non-destructive testing (e.g. detection of cracks in metal and plastic structures), veterinary (e.g. on-site X-ray imaging of animals), medical (e.g. X-ray imaging for emergency services, research, replacing conventional film X-ray images, dose verification and validation for radiation therapy), water content monitoring (e.g. soil moisture, timber water content, etc.), energy (e.g. coal/ash content), and agricultural (e.g. imaging of apples etc.).
We are already developing prototypes that take advantage of our materials patents. These include a portable X-ray imaging plate reader and a fibre optic dosimeter system.
Dosimeter Research and Technology
We are researching a group of materials that have potential as OSL dosimeters. We have a USA patent and we have submitted a New Zealand provisional patent.
There are a number of existing small volume dosimeters for medical applications where a continuous or periodic dose readout is required. These include OSL dosimeters, MOSFET dosimeters, and scintillation dosimeters.
The advantages of the materials that we are researching include, transparency, nearly tissue equivalent, and a high saturation dose. We are also researching materials that have a sensitivity that appears to be significantly greater than that from the only commercial OSL dosimeter Al2O3:C and the saturation dose is higher. This allows for lower doses and an extended linear dose range.
We have developed a fibre optic dosimeter prototype and we have submitted a patent application. We are working with medical physicists at Wellington Hospital New Zealand to characterize the materials and refine the dosimeter prototype. The measurements at Wellington Hospital include dose verification and validation with high energy linear accelerators that are used for radiation therapy and this is being done with the assistance of a PhD student and a joint MSc medical physics student employed at Wellington Hospital. They have also recently obtained external funding to support their research.
We are developing a 2D dosimeter that can potentially be used to replace gafchromic film for dose verification and validation for radiotherapy applications.
Fibre Optic Dosimeter Prototype
X-ray Storage Phosphor Research and Technology
We are researching glass-ceramics (micron sized crystallites in a glass matrix) and crystallite/polymer mixes. The glass-ceramic research is covered by our US patent, and has been liscensed to Materials Development Inc.
The medical imaging market is dominated by indirect imaging via x-ray storage phosphors and direct imaging (e.g. via a-Se detectors from Siemens). However standard radiation imaging plates from Siemens, GE and AGFA have moderate pixel sizes (to 0.07 mm) but the spatial resolution is >0.1mm. We have shown that a spatial resolution of at least 0.01mm is possible with our materials.
We have developed a cost-effective portable X-ray read-out unit for digital computed radiography. The potential applications include non-destructive testing, farm vets, and emergency services. This system works extremely well with existing commercial imaging plates for any application (e.g. non destructive testing, security) which does not involve human exposure, as the dose required for medical and dental imaging is not acceptable with regard to current standards and best practices.
However, we are currently developing very promising new materials which have the sensitivity required for medical and dental applications. The materials are also being optimised for dual energy imaging and multi-mode (ie, X-ray/gamma ray and neutron) imaging. IP protection is being sought for these.
Portable X-Ray Readout Prototype
Patents
Fluoroperovskite radiation dosimeters and storage phosphors
Christian Josef Dotzler, Andrew Edgar and Grant Victor McLelland Williams
Provisional patent application in the USA, AJ Park reference 564401 DDG, filed 5 July 2007. US filing number 60/929,626.
Pub. No. US2010/0200741 A1, 12 August, 2010.
Radiation dosimeter detection system and methods
Grant Williams
New Zealand Provisional Patent Application No. 588050, filed 17 September 2010.
Fluoro glass ceramic showing photostimulable properties
Peter Willems, Johann-Martin Spaeth, Stefan Schweizer, Andrew Edgar, Luc Struye and Paul Leblans
United States Patent No. US 6352949 B1, 5 March 2002