# Quasi-ideal photon counting x-ray CT with multi-energy inter-pixel coincidence counter (MEICC)

> **NIH NIH R21** · JOHNS HOPKINS UNIVERSITY · 2021 · $197,348

## Abstract

Project Summary
We propose a technical solution that enables nearly ideal photon counting detectors (PCDs) for x-ray
computed tomography (CT), which will bring most of clinical dreams surrounding PCD-CT into reality. We call
the solution multi-energy inter-pixel coincidence counter (MEICC) and it is feasible to implement the design
and algorithm of MEICC using today’s electronics technology. We plan to provide a proof of concept that will
“move the needle” by working on the detail of MEICC, optimizing the design and studying the performance of
MEICC using Monte Carlo (MC) simulations. PCD-CT is expected to be the next generation of x-ray CT. It has
great potentials such as improve the current CT images but also to enable new clinical applications, such as
higher spatial resolution, better soft tissue contrast, stronger contrast agent enhancement, radiation dose
reduction, quantitative CT imaging and biomarkers, accurate soft tissue material characterization, K-edge
imaging, and simultaneous multi-contrast agent imaging. Studies showed that latest PCDs were sufficiently
fast for clinical x-ray CT and several groups developed prototype whole-body PCD-CT systems and installed
them for a beta test in 2014–2018. Studies have shown great potential of PCD-CT. But, the performance of the
prototype PCD-CT did not meet high expectations. In fact, the performance was sometimes comparable to that
of dual-energy CT because of a phenomenon called “charge sharing” between PCD pixels. It increases noise
variance by a factor of 4, degrades the spatial resolution, degrades the energy response, and weakens the
spectral signals. Overall, it has a significantly negative impact on the performance of PCD-CT. Charge sharing
is inherent to the detection physics and the probability of charge sharing is ~70%. Thus, it is impossible to
avoid and is a very critical issue that needs to be addressed. MEICC will address both noise and bias added by
charge sharing. MEICC uses energy-dependent coincidence counters, keeps the book of charge sharing
events during the data acquisition, and corrects them using the exact number of the occurrences after the
acquisition is completed. MEICC does not interfere with the primary counting process; thus, PCDs with MEICC
will remain as fast as those without MEICC. MEICC can be implemented using today’s electronics technology
because its inter-pixel coincidence counters are simple and digital. We hypothesize that MEICC can eliminate
the effect of charge sharing, decrease noise to the minimal level, enhance signals, improve the energy
response, and over all, enable nearly ideal x-ray PCD-CT. We plan to test the hypothesis by accomplishing the
following 3 specific aims: (SA1) Develop MEICC designs and algorithms; (SA2) develop MC simulation
programs; (SA3) assess the task-specific performance of MEICC and other completing technologies using
Cramér–Rao lower bound as the primary figure of merit.

## Key facts

- **NIH application ID:** 10117252
- **Project number:** 5R21EB029739-02
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** Katsuyuki Taguchi
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $197,348
- **Award type:** 5
- **Project period:** 2020-04-01 → 2024-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10117252

## Citation

> US National Institutes of Health, RePORTER application 10117252, Quasi-ideal photon counting x-ray CT with multi-energy inter-pixel coincidence counter (MEICC) (5R21EB029739-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10117252. Licensed CC0.

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