Design and performance evaluation of a whole-body Ingenuity TF PET–MRI system

Abstract

The Ingenuity TF PET–MRI is a newly released whole-body hybrid PET–MR imaging system with a Philips time-of-flight GEMINI TF PET and Achieva 3T X-series MRI system. Compared to PET–CT, modifications to the positron emission tomography (PET) gantry were made to avoid mutual system interference and deliver uncompromising performance which is equivalent to the standalone systems. The PET gantry was redesigned to introduce magnetic shielding for the photomultiplier tubes (PMTs). Stringent electromagnetic noise requirements of the MR system necessitated the removal of PET gantry electronics to be housed in the PET–MR equipment room. We report the standard NEMA measurements for the PET scanner. PET imaging and performance measurements were done at Geneva University Hospital as described in the NEMA Standards NU2-2007 manual. The scatter fraction (SF) and noise equivalent count rate (NECR) measurements with the NEMA cylinder (20 cm diameter) were repeated for two larger cylinders (27 cm and 35 cm diameter), which better represent average and heavy patients. A NEMA/IEC torso phantom was used for overall assessment of image quality. The transverse and axial resolution near the center was 4.7 mm. Timing and energy resolution of the PET–MR system were measured to be 525 ps and 12%, respectively. The results were comparable to PET–CT systems demonstrating that the effect of design modifications required on the PET system to remove the harmful effect of the magnetic field on the PMTs was negligible. The absolute sensitivity of this scanner was 7.0 cps kBq−1, whereas SF was 26%. NECR measurements performed with cylinders having three different diameters, and image quality measurements performed with IEC phantom yielded excellent results. The Ingenuity TF PET–MRI represents the first commercial whole-body hybrid PET–MRI system. The performance of the PET subsystem was comparable to the GEMINI TF PET–CT system using phantom and patient studies. It is conceived that advantages of hybrid PET–MRI will become more evident in the near future.

Accelerated time-of-flight (TOF) PET image reconstruction using TOF bin subsetization and TOF weighting matrix pre-computation

“…The time-of-flight technology has recently dominated the design concept of commercial PET/CT scanners by providing higher image quality and improved lesion detectability. As the prevalence of TOF technology especially in PET/MRI scanners is growing (Zaidi et al 2011, Deller et al 2014, the importance of efficient TOF implementation and development of convergent model-based image reconstruction algorithms is increasing. In this work, we elaborated the practical aspects of TOF PET image reconstruction implementation using the pre-computation of TOF weighting coefficients matrix in conjunction with the base-geometric symmetries.…”

A Pivotal Time for Hybrid PET/MR Imaging Technology

“…The Ingenuity TF PET/MRI (Philips Healthcare, Best, the Netherlands), equipped with time-of-flight Gemini TF PET and Achieva 3T X-series MRI scanners, falls in this category and uses a rotating patient handling system to enable sequential PET and MR imaging. Full characterization demonstrated no significant interference between the 2 systems or compromise of PET subsystem performance in the presence of the strong MR magnet [6]. A similar design concept was also developed for high-resolution neuromolecular imaging in high magnetic field by docking separate PET (Siemens' high-resolution research tomograph) and 7-T MR imaging units together with a shared common bed to integrate both modalities [7].…”

Novel Quantitative Techniques in Hybrid (PET-MR) Imaging of Brain Tumors

“…14,19 Combining PET and MR for simultaneous acquisition of spatially and temporally correlated PET-MR data sets is technically challenging owing to the strong magnetic fields in the MR subsystem. Despite the challenges and technical difficulties, a clinical PET-MR prototype (BrainPET, Siemens Medical Solutions, Erlangen, Germany) dedicated for simultaneous PET-MR brain imaging was developed and installed in a few institutions for validation and testing.…”

“…2 shows representative clinical brain PET-CT and PET-MR images of a healthy subject acquired sequentially on 2 combined systems, namely the Biograph TrueV (Siemens Healthcare, Erlangen, Germany) 22 and Ingenuity TF PET-MRI (Philips Healthcare, Eindhoven, The Netherlands). 19 The PET-CT study was started 30 minutes following injection of 370 MBq of 18 F-FDG followed by PET-MR imaging, which started about 80 minutes later. The better soft tissue contrast observed on MR imaging is obvious and further emphasizes the ineffectiveness of PET-CT for this indication and the potential role of PET-MR imaging.…”