Digital PET Balances Scan Time and Resolution

Efficiency and effectiveness are inseparable in clinical medicine. Digital PET addresses them both. The key is the detector built into Philips Healthcare’s digital Vereos PET/CT.

Because photons generated during a PET exam are counted individually, digital detectors can record more such events per second than analog ones.

TheUniversity of Vermont Medical Center (UVMC)often leverages this on its Vereos to produce images with very high quality. Alternatively, UVMC uses Vereos to shorten scan time while still producing diagnostic quality images.

“When there is a big leap in sensitivity like you see from analog to digital, you have to look at what you are going to do with it,” saidJay Kikut, M.D., director of nuclear medicine and PET/CT at the UVMC. “For oncology patients, our decision is clear — we want to use it for improved image quality.”

This is paramount when clinicians use Vereos to make diagnoses and stage cancer patients. “Vereos provides us very accurate staging of our patients,” he said. “To have the best outcome, you have to match the treatments to the stage.” Exactly staging patients leads to a more individualized choice of therapy.

The 1 mm thick images reveal details in this PET/CT whole-brain volume acquired during a five-minute scan on the Vereos PET/CT. Images courtesy of Philips Healthcare.

Oncological applications account for about 80 percent of PET scans done at UVMC. (The remaining 20 percent of PET/CTs examine the heart or brain.)

当设置为提供最大的空间分辨率时，通过数字PET实现的增加的灵敏度用于检测非常小的病变。另外，一些在UVMC的患者最好通过扫描来减少在PET/CT孔内花费的时间。Such shorter exams might be chosen for children or patients who are uncomfortable in tight spaces to minimize the movement that can cause image artifacts.

Although the scans may be substantially shorter — five or even three minutes versus the 15 needed with an analog detector — Vereos’ PET acquisitions can still deliver high diagnostic quality, he said.

Development of theDigital Photon Counting (DPC) technology, which serves as Vereos’ backbone, is the latest pivotal moment in the history of PET/CT, according to Dhruv Mehta, a senior product manager at Philips Healthcare. The first occurred some 20 years ago with the hybridization of PET with CT. The second was the development of time-of-flight (introduced first-to-market by Philips Healthcare), which helps localize lesions and improves signal-to-noise. Fully digital PET with DPC technology is the latest advancement affecting this hybrid, Mehta said.

“It is really the next generation of PET/CT,” he said.

数字PET和模拟PET之间的区别类似于投影电视和液晶电视之间的区别。他说，液晶电视的数字架构可以提供更清晰的图像、更高的效率和更大的动态范围。数字PET在分子成像方面也有类似的功能。Mehta说，当试图超越当前基于fdg的肿瘤学应用，进入神经学、心脏病学和新兴示踪剂的新兴应用时，图像质量和动态范围之间的联系是重要的。

“With a shorter acquisition, the patient is less likely to move,” he said. “The clinical benefit is that you have a better study with less motion. As a result, you can visualize lesions better.”

The other aspect of efficiency is increased throughput. In the U.S., PET patient volumes typically hover around a dozen or so patients per day. In Europe or China, however, daily throughput may exceed 30.

Mehta cautions that many factors beyond the scanner may affect throughput at a facility. Chief among them are ones related to patient management. Cutting scan time to under five minutes, however, “is a substantial improvement.”

Very relevant when making purchasing decisions, he said, is the increased precision that digital PET offers and the hedge that Vereos provides against obsolescence. At present, PET is one of the few commercial modalities with high-end systems that are still analog, he said. That, however, could change.

“We envision a time in the future when all PET/CT is digital,” Mehta said.

Editor's note: This is the third blog in a series of four on digital PET/CT. The first blog, “How Digital PET/CT Can Improve Clinical Care,” can be foundhere. The second blog, “Why - And How - Digital PET Is Better Than Analog,” can be found here.

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