The winning paper – Physical and clinical performance of the mCT time-of-flight PET/CT scanner – (Phys. Med. Biol. 56 2375) was written by researchers from the University of Tennessee Medical Center, the University of Surrey and Siemens Molecular Imaging. The team characterized the performance of Siemens' Biograph mCT TOF PET/CT scanner, and compared this with its predecessor, the Biograph TruePoint TrueV. In particular, they defined the improvements that could be achieved with time-of-flight (TOF) capability.

TOF PET works by recording the time difference between detection of the two coincidence photons. This value is used to infer the most likely location of the annihilation event along the line-of-response, with accuracy dependent on the system's time resolution. As such, TOF measurements help to improve the signal-to-noise ratio (SNR) of the resulting PET image. In the winning paper, the authors tested this premise using the mCT scanner, which measures TOF and incorporates this information into the image reconstruction process.

"The mCT had just been released and the clinical availability of TOF at the time was rather novel and unexplored," explains first author Bjoern Jakoby from Siemens. "Therefore, it was an obvious scientific motivation to investigate the performance of the scanner, including this 'novel feature'. This paper was the first thorough performance analysis of the mCT PET/CT and served other scientists as a research basis/reference for their work."

Jakoby and co-authors first examined a torso-shaped image-quality phantom containing different sized spheres filled with tracer solution. Images recorded with the mCT and TruePoint TrueV exhibited similar spatial resolution. With the addition of TOF, however, the mCT produced substantially higher image contrast recovery and SNR.

The researchers also examined two clinical cases from prior PET oncology studies. Image quality analysis of the patient data sets revealed that using TOF information in the image reconstruction improved the contrast, noise and SNR. In patient 1, the lesion SNR improved by a factor of 1.7, with a contrast increase of 19% and a 22% noise reduction. For patient 2, SNR improved by a factor of 1.2, with a 3% contrast increase and a 16% noise reduction. "Overall, significant performance improvements were obtained on the mCT in comparison with the TruePoint TrueV," they wrote.

Since the paper was published, the team has studied the clinical applicability and feasibility of TOF. The mCT has proved a highly successful scanner, and now has a large installed base. Advances in PET detector technology over recent years have also improved the time resolution of TOF. "This development expanded the area of applications in which TOF is being employed and further explored," says Jakoby, who is currently working on various MR/PET research topics.

Rotblat medal

The PMB citations prize is marked with the presentation of the Rotblat medal, named in honour of Professor Sir Joseph Rotblat (PMB's second and longest-serving editor). The medal was presented to Jakoby and co-authors by PMB Editor-in-Chief Simon Cherry, at last week's IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) in Strasbourg.

"I feel very honoured to receive such a prize," says Jakoby. "It does demonstrate that the effort that we as a team put into this work was worthwhile and appreciated by other scientists."

• The winner of the 2016 Physics in Medicine & Biology citations prize is: Physical and clinical performance of the mCT time-of-flight PET/CT scanner B W Jakoby, Y Bercier, M Conti, M E Casey, B Bendriem and D W Townsend Phys. Med. Biol. 56 2375.

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