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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - PCSCT (Photon Counting Spectral Computed Tomography)

Teaser

Summary

Computed Tomography (CT) has revolutionized the medical community by allowing the user to see inside a patient without surgery. From its introduction in the seventies, CT has been used for a continuously increasing variety of clinical applications, particularly over the last two decades. Due to its speed and versatility, CT is the workhorse imaging modality in the radiology department and diagnostic imaging centres; it is the top prescribed exam for such diverse indications as head trauma, acute chest pain, abdominal pain and aortic disease. Despite a significant development over the last decade however, current energy integrating CT detectors are unable to obtain sufficient spectral information and have a limited spatial resolution. This leads to image artefacts and limited visualization of important details. For some indications, such as initial characterization of liver lesions, magnetic resonance imaging (MRI) is therefore preferred due to its larger soft tissue contrast and for some types of lung exams, basic projection x-ray with flat panel detectors (DXR) is preferred because of its higher spatial resolution and lower dose.

The objective of this work is to introduce a novel photon counting spectrally resolved detector with multiple energy bins to the CT scanner market, which will deliver high customer value in terms of lower patient radiation dose and significantly improved image quality through increased spectral and spatial resolution, compared to current state-of-the-art. In addition, the spectral information can be used to determine the local area density of an objectÂ´s constituent materials (e.g. contrast agent). Looking ahead, since photon counting CT is quantitative, it enables the use of targeted contrast agent (potentially allowing non-invasive visualization and characterization of a variety of disease states by localizing to a particular tissue), thus enabling more personalized diagnostics compared to todayâ€™s technology.

Potential applications in health care diagnostics are wide and the first application will be validated to meet the strong clinical need for a substantial improvement in stroke diagnosis and treatment. The technology and the added clinical value will be validated and compared with state-of-the art in a clinical trial by radiologists at the Karolinska University Hospital. As an outcome, Prismatic Sensors expects the new patented detector technology to be the future choice for some or all the major global vendors. This will support Europe\'s position as a world-leader in medical innovation and healthcare technology, as well as improve hospital efficiency and save healthcare costs. Most importantly, it will have a positive impact for the survival odds for a large number of patients worldwide.

Work performed

Jan-2019
An overall objective of this project is to build and verify a full field of view spectral photon counting detector system and integrate into a state-of-the-art CT Gantry. The current period started with the creation of a complete system requirement specification, defining any changes or updates to the commercial gantry needed for successful integration. This included an overview of current thermal system, software and calibration, power, space, weight, data transfer etc. In addition, the specification for the photon counting system was approved.

Feb-2019
The new ASIC was evaluated and verified in benchtop measurements using a verification board, specifically developed for this purpose. A comparison to design targets was made. The changes compared to former ASIC version was documented to keep track of the development. The conclusion was that the new ASIC was ready for tape out.

March-2019
The new sensor design was verified in probe tests. The sensor design was evaluated against certain acceptance criteria, defined in a specific sensor acceptance test criteria document. The main results showed no significant defects or other problem identified, and the sensor concluded to be ready for production

April-2019
A first prototype for the new collimator specifically designed for the novel detector, was fabricated. Specifically, the collimator prototype plate positioning was evaluated against upper specification limits, defined with respect to risk of spectral artefacts. The results of plate position measurements for collimator prototype testing indicates that the current prototype could be used for continued evaluation.

July-2019
Production of detector tiles was started, including programming of automatic robot assembly and testing equipment. Several detector tiles were produced and verified using thickness measurements on robot and x-ray functional testing. In addition, reliability was evaluated using temperature-humidity-bias testing (THB), temperature cycling and radiation hardness testing. All detector tiles were measured for surface deviation from specification limits in robot. In summary, the majority of detector tiles fulfilled the thickness, THB, temperature cycling and radiation hardness requirements which indicates that the design is reliable.

July-2019
The results of the ASIC probe testing were delivered by wafer maps and only ASICs passing the production probe testing are now used for detector builds.

Aug-2019
Sensors from the second batch were evaluated by probing after singulation. To enable this, Prismatic Sensors developed a probe card. The results of sensor probe measurement indicated that the second sensor batch could be used for detector production.

Aug-2019
One full detector module was mounted in a CT gantry at Prismatic facilities. This included fabrication of new module boards, and improvements of gantry thermal system according to system specification. In addition, the mechanical interface (module-to-gantry) was updated. To evaluate the accuracy in mounting and assembly, an edge sweep was performed. The x-ray performance of the detector module was evaluated. In summary, the detector module is working and counting x-rays.
The main result of this period is that a full detector module including collimator has been evaluated in a CT gantry, including reliability testing, and confirmed working.

Final results

The project for the current period has resulted in a successful integration of a photon counting spectrally resolved detector module in a commercial CT gantry. To achieve this, several technical difficulties were solved (power, thermal, data rates etc.). For the continuation of the project, additional modules will be installed, enabling acquisition of image data. The expectation of the project is that the benefits of photon counting CT compared to state-of-the-art energy integrating systems will be demonstrated, as well as any technical hurdles overcome. This includes both hardware and algorithm development as the novel technology requires different calibration schemes. The goal is to show improved image quality â€“ the increased dose efficiency compared to conventional systems, as well as the increased spatial resolution and the prospect of beamhardening elimination and iodine quantification naturally has applications in many imaging areas such as cardiac and stroke imaging, where accurate characterization of plaque is important.