Surreal digital illustration of PET scan accuracy

Unlock Precision in PET Scans: A Simple Guide to Reliable Timing

Jordan Keane in Health & Wellness December 2025 • 4 min read.

"Achieving accurate coincidence resolving time (CRT) measurements is crucial for high-quality PET imaging. Discover how to optimize your setup for reliable results."

Positron Emission Tomography (PET) is a cornerstone of modern medical imaging, allowing doctors to see how your body functions at a cellular level. One of the key factors influencing the clarity and accuracy of PET scans is something called coincidence resolving time, or CRT. Think of CRT as the PET scanner's ability to pinpoint exactly when and where a radioactive tracer emits signals. When CRT is optimized, it helps doctors to better detect small lesions and subtle changes that might otherwise go unnoticed.

The quest to improve CRT has led researchers to explore various detector designs and high-performance front-end readout circuits. Many facilities use multichannel waveform digitizers to assess PET detectors because these tools enable versatile data analysis of detector output signals. But recent research reveals that using these digitizers inappropriately can throw off CRT measurements, leading to potentially misleading results.

This article breaks down how to avoid common pitfalls and achieve reliable CRT measurements. Drawing from a study published in Physics in Medicine & Biology, we'll explore practical tips for optimizing your PET scanner setup and ensuring the most accurate results. Whether you're a seasoned technician or new to the field, this guide will empower you to enhance the precision of your PET imaging.

The DRS4 Chip Challenge: Avoiding Common Pitfalls

Surreal digital illustration of PET scan accuracy

At the heart of many multichannel waveform digitizers lies the Domino Ring Sampler 4 (DRS4) chip. This chip rapidly samples electrical signals, turning them into digital data that can be analyzed. However, the study highlights that incorrect data acquisition (DAQ) setups using a DRS4-based digitizer can lead to significant errors in CRT determination. The issue isn't the chip itself, but rather how its input channels are configured.

To illustrate the problem, the researchers conducted experiments using a pair of Hamamatsu R9800 photomultiplier tube (PMT) based PET detectors. They found that the way input channels were combined significantly affected the CRT measurements. Specifically, they looked at intra-chip and inter-chip sampling:

Intra-chip sampling: This involves using input channels that are on the same DRS4 chip.
Inter-chip sampling: This involves using input channels that are on different DRS4 chips.

The results were revealing. Intra-chip CRT measurements produced unusual streak patterns on 2D CRT maps, artificially lowering CRT values. On the other hand, inter-chip CRT measurements provided a much more reliable estimate of timing resolution. This suggests that the way signals are processed within the DRS4 chip can introduce errors if not carefully managed.

Practical Implications and Next Steps

The study's findings offer valuable guidance for facilities using multichannel waveform digitizers with DRS4 chips. By carefully selecting input channels for inter-chip measurements, high-frequency signal crosstalk can be minimized, ensuring a more reliable estimation of timing resolution. This translates to more accurate PET scans and improved diagnostic capabilities. Future research could delve deeper into the origins of on-chip signal crosstalk and explore mitigation strategies, paving the way for even more precise PET imaging technologies.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

What is Coincidence Resolving Time (CRT) and why is it important in PET scans?

Coincidence Resolving Time (CRT) is the PET scanner's ability to accurately pinpoint when and where a radioactive tracer emits signals. It's crucial because it directly impacts the clarity and accuracy of PET scans. Optimized CRT allows doctors to better detect small lesions and subtle changes, leading to improved diagnoses and patient care. Without precise CRT measurements, the images produced by the PET scanner could be less clear, potentially missing crucial details that affect treatment decisions.

How can the Domino Ring Sampler 4 (DRS4) chip affect the accuracy of CRT measurements?

The DRS4 chip, used in many multichannel waveform digitizers, can introduce errors in CRT determination if the data acquisition (DAQ) setup is not configured correctly. The study highlights that incorrect use can lead to inaccurate CRT values. The key issue is how the input channels are configured, specifically whether intra-chip or inter-chip sampling is used. Intra-chip sampling, where input channels are on the same DRS4 chip, can produce unusual streak patterns on 2D CRT maps, artificially lowering CRT values. Inter-chip sampling, using channels on different DRS4 chips, generally provides a more reliable estimate of timing resolution.

What is the difference between intra-chip and inter-chip sampling, and how does it impact CRT measurements?

Intra-chip sampling involves using input channels on the same DRS4 chip, while inter-chip sampling uses channels on different DRS4 chips. The study found that intra-chip sampling can lead to significant errors in CRT measurements, producing misleading results like artificial lowering of CRT values and streak patterns. This occurs because the signal processing within a single DRS4 chip can introduce errors. Inter-chip sampling, on the other hand, minimizes these errors, providing a more accurate estimate of the timing resolution by avoiding the internal signal crosstalk issues associated with a single chip.

How can I ensure reliable CRT measurements when using a DRS4-based digitizer?

To ensure reliable CRT measurements, focus on using inter-chip sampling. The study advises carefully selecting input channels for inter-chip measurements to minimize high-frequency signal crosstalk. This approach provides a more reliable estimation of timing resolution, leading to more accurate PET scans. This is a practical step, that anyone using a multichannel waveform digitizer with DRS4 chips can implement to improve the precision of their PET imaging.

What are the implications of inaccurate CRT measurements, and what are the future directions for improving PET imaging technology?

Inaccurate CRT measurements can lead to lower image quality and potentially misdiagnosis or delayed diagnosis. In other words, it might be more difficult to see small lesions and subtle changes at a cellular level. The study suggests a focus on inter-chip measurements to mitigate these issues. Future research could delve deeper into the origins of on-chip signal crosstalk within the DRS4 chip and explore mitigation strategies. This can pave the way for even more precise PET imaging technologies, improving patient outcomes and enhancing the capabilities of medical imaging.