Events

2022 IEEE NSS MIC RTSD

05 Nov - 12 Nov 2022 Milano Convention Centre, Milan, Italy

Hosted in Milan, Italy, the IEEE NSS-MIC-RTSD is a meeting held for all those involved in the field of radiation detectors and instrumentation. Presenters and attendees are welcomed from a range of applications, fields of study and levels of experience. Those attending receive the opportunity to share their ideas and knowledge with one another, and can attend either in person or virtually.

At the event, Kromek are involved in five presentations: two describing the collaborative, potentially life-saving work in the Low Dose MBI Project and three our Principal Physicist, Alexander Cherlin, is a co-author of.

Will we see you there?

For more information about the event and how to register, visit the IEEE website here 

Kromek Event Presentations

Low Dose MBI Project Presentations

 

1.  A feasibility prototype of a low-dose stationary tomographic Molecular Breast Imaging camera using 3D position sensitive CZT detectors

Presentation type:      RTSD Session (Oral)
Session:   R-15 — RTSD Closing session
Date:   Friday, 11 November, 2022, 10:50 AM – 12:38 PM

  1. Erlandsson2, A. Wirth1, I. Baistow1, K. Thielemans2, B. F. Hutton2

1 Kromek Ltd., Sedgefield, United Kingdom
2 University College London, Institute of Nuclear Medicine, London, United Kingdom

 

Abstract:

A novel Molecular Breast Imaging system (MBI) is being developed by Kromek and University College London. MBI systems have been shown to provide excellent results in patients with dense breasts, but higher than mammography patient dose and long imaging time of 40 min impede their wide adoption. The design is based on a pair of opposing CZT detector arrays and high density multi-pinhole (MPH) collimators. The new system combines superior energy and position resolution and depth of interaction (DOI) sensing of CZT detectors, wide range angular sampling of MPH collimators and novel de-multiplexing image reconstruction techniques to deliver tomographic images with stationary detectors. The new system is expected to mitigate the MBI drawbacks without compromising diagnostic content.
The characterisation of the proof-of-principle prototype along with the input from the system simulations allowed demonstration of the feasibility of the new principle for dose/time combination reduction. The experimental and simulation study results suggest that quantification of the reduction factor requires improving the DOI resolution and stability of DOI calibration. A new feasibility prototype using upgraded ASIC and new front-end electronics was designed, built, and characterised. New image reconstruction and de-noising algorithms were developed on simulated data to improve the Contrast-to-Noise (CNR) ratio and reduce the fluctuations in the correlated background noise associated with MPH image reconstruction. The collimator geometry was further optimised by including non-local means noise filtering which increased the CNR by almost a factor of 3. The current results indicate that we can achieve the dose reduction to the mammography level, reduce the minimum size of detected lesions to 5-6 mm and have an additional potential for reduction of the measurement time.

 

2.  Optimization of a Stationary Tomographic MBI System Including Non-Local Means Filtering

Presentation type:      MIC Poster Session (Poster)
Session:   MIC-04 — MIC Posters I
Date:   Wednesday, 9 November, 2022, 14:30 AM – 16:30 PM

 

  1. Erlandsson2, A. Wirth1, K. Thielemans2, I. Baistow1, A. Cherlin1, B. F. Hutton2

1 Kromek Ltd., Sedgefield, United Kingdom
2 University College London, Institute of Nuclear Medicine, London, United Kingdom

 

Abstract:

A novel stationary tomographic Molecular Breast Imaging (MBI) system is currently under development, with the aim of obtaining high image-quality with low dose and short scanning time. The system is based on dual opposing CZT detector arrays and multi-pinhole collimators. We have recently modified the iterative image reconstruction procedure by incorporating a novel relaxation scheme, in order to make the image contrast and noise properties more uniform throughout the field-of-view. In addition, we have introduced a post-reconstruction image de-noising step based on the non-local means (NLM) filter. In view of the significant effect that these steps had on the image quality, we decided that it would be appropriate to perform a new system parameter optimization. The parameters investigated were pinhole size, opening angle and separation, as well as the number of reconstruction iterations and the degree-of-smoothing (DOS) parameter of the NLM filter. The optimization was performed based on simulated data, by maximizing the contrast-to-noise ratio (CNR) in the final images. We found that the optimal system parameters were not so different with and without the NLM-filter, while the CNR was almost 3 times higher with the filter.

 

Co-author Presentations

 

1.  Sub-Voxel Position Resolution in Pixelated CZT Detectors through Pulse Shape Analysis

Presentation type:      RTSD Session (Oral)
Session:   R-02 — RTSD CdZnTe Detectors
Date:   Monday, 7 November, 2022, 4:50 PM – 6:38 PM

 

  1. Rintoul1, H. Brown1, C. T.A. Everett1, L. Harkness-Brennan1, D. Judson1, D. Wells1, A. Cherlin2

1 University of Liverpool, Department of Physics, Liverpool, United Kingdom
2 Kromek Group plc, Sedgefield, United Kingdom

 

Abstract:

Cadmium Zinc Telluride (CZT) detectors provide excellent energy resolution at room temperature operation and, through pixelisation, three-dimensional position sensitivity. At the University of Liverpool, a digital read-out system has been designed and built for the development and implementation of Pulse Shape Analysis (PSA) algorithms in pixelated CZT detectors. These algorithms may be used as an alternative to finer pixelisation to provide improved position resolution. Two CZT crystal geometries have been investigated using collimated gamma-ray scanning to characterise the signal response of 3×3 pixel clusters as a function of gamma-interaction position. The two crystal geometries studied are of dimensions 22x22x5 mm3 and 8.8×8.8×10 mm3, each pixelated into 11×11 anodes. Gamma-ray beams of energies 60 keV, 122 keV, and 662 keV have been used to parameterise the position-dependent image charge magnitudes and charge collection times, from which response maps have been produced. The maps have been used to improve the 2x2x5 mm3 position resolution of the 5 mm thick crystal to 0.65×0.69×1.37 mm3 at gamma energies of 122 keV using only the anode response and not accounting for the divergence of the collimated beam which dominated. This work reports on the position resolution achievable using analysis of digitised signal shapes as a function of gamma energy and detector geometry for two pixelated CZT detectors. The characterised signal response of the two CZT crystals will be used as a basis for validating a charge transport simulation, such that optimal application specific CZT geometry can be selected, based upon the requirements of cost, gamma energy, and desired position resolution.

2.  Novel Large Area 3D CdZnTe Drift Strip Detectors for Molecular Breast Imaging

Presentation type:      RTSD Session (Oral)
Session:   R-02 — RTSD CdZnTe Detectors
Date:   Monday, 7 November, 2022, 4:50 PM – 6:38 PM

 

  1. R.H. Owe1I. Kuvvetli1, A. Cherlin2, B. Harris3, I. Baistow2, D. Tcherniak1, C. Budtz-Jørgensen1

1 Technical University of Denmark, DTU Space, Kgs. Lyngby, Denmark
2 Kromek Ltd., Sedgefield, County Durham, United Kingdom
3 Kromek Ltd., Zelienople, Pennsylvania, United States of America

 

Abstract:

Molecular Breast Imaging (MBI) is a candidate for supplementary screening to the conventional X-ray mammography. On a mammogram, a tumor can be masked by dense breast tissue, leaving it undetected. However, the MBI technique does not depend on the breast density. The barriers for the widespread adoption of MBI technique are its currently higher patient dose, and longer imaging time. Emerging MBI technologies are countering these issues, and requires the sensor technology to display excellent spectral and spatial resolution (preferably sub-mm) in 3D. We will present the novel 3D CdZnTe (CZT) drift strip detector technology developed in a collaboration between Kromek and DTU Space, intended for future MBI systems. The detector is 4cm x 4cm x 0.5cm, which is currently the largest iteration of this specific detector technology ever produced. The specific electrode geometry and high voltage biasing allows for the anodes to be screened from hole movement, resulting in the detector to operate as single-polarity sensing. The unique electrode geometry allows for sophisticated pulse shape processing to; characterize distinct interaction types (Photoelectric absorption, Compton scattering, Pair production), determine the 3D position of a given interaction, and the deposited energy in 3D with correction for trapping or material impurities. The new large area 3D CZT drift strip detector electrode geometry is flexible such that the division between anodes and drift strips can be alternated easily, allowing for in depth analysis of the optimal configuration. The detector will display a sub-mm position resolution in the lateral direction, as well for the depth of interaction, making it a viable candidate for future MBI technologies.

 

3.  Characterization of a 5 mm thick CZT-Timepix3 pixel detector

Kromek were able to provide the CZT detector for this study

Presentation type:      RTSD Session (Oral)
Session:   R-12 — RTSD CdZnTe Detectors
Date:   Thursday, 10 November, 2022, 2:00 PM – 4:18 PM

 

  1. Smolyanskiy1, B. Bergmann1, P. Burian1, 2, A. Cherlin4, D. Maneuski3, V. O’Shea3, S. Pospisil1

1 Czech Technical University, Institute of Experimental and Applied Physics, Prague, Czech Republic
2 University of West Bohemia, Faculty of Electrical Engineering, Pilsen, Czech Republic
3 University of Glasgow, School of Physics and Astronomy, Glasgow, United Kingdom
4 Kromek Ltd., Sedgefield, United Kingdom

 

Abstract:

This paper describes the study of the hybrid pixel Timepix3 detector with a 5 mm CZT sensor operated at room temperature. The basic parameters of the detector (the IV curve and the energy resolution) were measured as well as, for the first time, the charge collection efficiency (CCE), and the charge carrier drift time in dependence on the interaction depth. It became possible by analyzing the detector response to charged particles entering the detector at a grazing angle to the sensor normal. The detector demonstrated a good performance providing almost constant CCE and the uniformity of the electric field across the sensor depth. An achieved resolution (FWHM) is 35 keV at 340 keV. The electron drift velocity was measured to be 2.27 * 106 cm/s at -1200 V. The sensor resistivity extracted from the IV curve measurement is 0.78 GOhm * cm. Further investigations of the mobility lifetime product and the diffusion coefficient are ongoing.

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