Moving from computer simulation to patient images, researchers are now demonstrating the benefits that time-of-flight (TOF)/PET (positron emission tomography) imaging can provide for cancer patients.

Moving from computer simulation to patient images, researchers are now demonstrating the benefits that time-of-flight (TOF)/PET (positron emission tomography) imaging can provide for cancer patients. The result? Superior images and shorter patient scan times for starters, according to a study released at the 54th Annual Meeting of SNM, the world's largest society for molecular imaging and nuclear medicine professionals, June 2–6 in Washington, D.C.

"Our TOF/PET patient images exhibit superior image quality and suggest that shorter patient scan times could be performed in many cases," said Amy Perkins, a Philips Medical Systems clinical site scientist based at the University of Pennsylvania in Philadelphia. "Previously, we have studied TOF/PET with computer simulations and controlled experiments to approximate the behavior within the human body, showing that we can get very good image quality with shorter scanning times," she said. "We have now moved our investigation to clinical studies—using PET scans from patients with a wide range of body weight, with different types of cancer and with different size cancer tumors—to determine whether the scan time may be reduced significantly without sacrificing clinical content," added Perkins. "In our study, we are getting an excellent representation of what's going on in the body," she added.

Very simply, conventional PET scanners create images by detecting gamma rays produced by a radioisotope after it is administered to a patient. Conventional scans track where the rays go, but they don't take into consideration the precise time it takes for each ray to reach the PET detector. TOF/PET scanners measure this time difference with precision, enabling the images to be reconstructed with significantly improved image quality, said Perkins. PET combined with computed tomography (CT) imaging enables the collection of both biological and anatomical information during a single exam, with PET picking up metabolic signals of body cells and tissues and CT offering a detailed map of internal anatomy.

Using the Philips Gemini TF PET/CT—the only clinical PET/CT machine with TOF in the world—information was reconstructed for 30 patients, comparing images using the standard acquisition time of 30 minutes to scan times as short as ten minutes. "TOF/PET imaging can achieve better quality images than conventional PET imaging in less time," said Perkins. "Our preliminary results indicate that the benefit of TOF imaging is most significant for heavy patients for whom achieving high-quality images is often quite challenging even with acquisition times greater than 30 minutes. In contrast, lighter patients have higher quality images and can be scanned for less time than heavy patients. This gives doctors the flexibility to improve patient comfort and increase the number of patients scanned without jeopardizing the ability to detect and quantify cancer," she added. "In some cases, TOF/PET detected lesions that are missed with conventional PET," said Perkins.

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