Combined PET/MRI: from Status Quo to Status Go. Summary Report of the Fifth International Workshop on PET/MR Imaging; February 15-19, 2016; Tübingen, Germany.

This article provides a collaborative perspective of the discussions and conclusions from the fifth international workshop of combined positron emission tomorgraphy (PET)/magnetic resonance imaging (MRI) that was held in Tübingen, Germany, from February 15 to 19, 2016. Specifically, we summarise the second part of the workshop made up of invited presentations from active researchers in the field of PET/MRI and associated fields augmented by round table discussions and dialogue boards with specific topics. This year, this included practical advice as to possible approaches to moving PET/MRI into clinical routine, the use of PET/MRI in brain receptor imaging, in assessing cardiovascular diseases, cancer, infection, and inflammatory diseases. To address perceived challenges still remaining to innovatively integrate PET and MRI system technologies, a dedicated round table session brought together key representatives from industry and academia who were engaged with either the conceptualisation or early adoption of hybrid PET/MRI systems. Discussions during the workshop highlighted that emerging unique applications of PET/MRI such as the ability to provide multi-parametric quantitative and visual information which will enable not only overall disease detection but also disease characterisation would eventually be regarded as compelling arguments for the adoption of PET/MR. However, as indicated by previous workshops, evidence in favour of this observation is only growing slowly, mainly due to the ongoing inability to pool data cohorts from independent trials as well as different systems and sites. The participants emphasised that moving from status quo to status go entails the need to adopt standardised imaging procedures and the readiness to act together prospectively across multiple PET/MRI sites and vendors.

18F-DOPA PET/CT unravels malignant paraganglioma mimicking temporomandibular joint disorder.

This report presents a 29-year-old patient with severe temporomandibular joint (TMJ) pain. Anamnesis and clinical examination led us to the diagnosis of TMJ disorder. He was also in control for a malignant paraganglioma originating from the right carotid body. After initial surgery 8.5 years ago and the removal of metastases 2 years ago he was deemed disease free. An (18)F-3,4-dihydroxyphenylalanine (DOPA) positron emission tomography (PET)/CT scan was obtained during follow-up 6 months before he was presented to our clinic. Suspicious of a connection between the actual pain and the tumour, we scrutinized these images. We found a tiny pathological tracer uptake in the right jugular foramen but no correlating finding in the matching CT. We repeated the DOPA PET/CT and found several metastases including the previously detected lesion. Further thin-slice CT and MRI showed a 5 mm paraganglioma located anteriorly to the jugular bulb within the jugular foramen. The lesion was in close relation to the Arnold's nerve, a branch of the vagus nerve which carries sensory information from the external tympanic membrane, external auditory canal and the external ear and explained the severe pain in our patient. He then underwent radiotherapy (45 Gy) during which the pain diminished considerably. In a variety of neuroendocrine tumours, including paraganglioma, DOPA PET/CT allows primary diagnosis, staging and restaging with a higher detection rate than conventional radiological imaging. Owing to low anatomical resolution however, high resolution contrast-enhanced CT and MRI are necessary to complete the investigations.

Arterial spin-labeling MRI perfusion in tuberous sclerosis: correlation with PET.

Neuroimaging using magnetic resonance imaging (MRI) is required for the investigation of surgically intractable epilepsy. In addition to the standard MRI techniques, perfusion sequences can be added to improve visualization of the underlying pathological changes. Also, as arterial spin-labeling (ASL) MRI perfusion does not require contrast administration, it may even be advantageous in these patients. We report here on three patients with epilepsy and tuberous sclerosis who underwent brain MRI with ASL and positron emission tomography (PET), both of which were found to correlate with each other and with electrophysiological data.

Three-phase 18F-fluorocholine PET/CT in the evaluation of prostate cancer recurrence.

AIM: Contribution of 3-phase 18F-fluorocholine PET/CT in suspected prostate cancer recurrence at early rise of PSA. PATIENTS, METHODS: Retrospective analysis was performed in 47 patients after initial treatment with radiotherapy (n=30) or surgery (n=17). Following CT, 10 minutes list-mode PET acquisition was done over the prostate bed after injection of 300 MBq of 18F-fluorocholine. Three timeframes of 3 minutes each were reconstructed for analysis. All patients underwent subsequent whole body PET/CT. Delayed pelvic PET/CT was obtained in 36 patients. PET/CT was interpreted visually by two observers and SUVmax determined for suspicious lesions. Biopsies were obtained from 13 patients. RESULTS: Biopsies confirmed the presence of cancer in 11 of 13 patients with positive PET for a total of 15 local recurrences in which average SUVmax increased during 14 minutes post injection and marginally decreased in delayed scanning. Conversely inguinal lymph nodes with mild to moderate metabolic activity on PET showed a clearly different pattern with decreasing SUVmax on dynamic images. Three-phase PET/CT contributed to the diagnostic assessment of 10 of 47 patients with biological evidence of recurrence of cancer. It notably allowed the discrimination of confounding blood pool or urinary activity from suspicious hyperactivities. PET/CT was positive in all patients with PSA>or=2 ng/ml (n=34) and in 4/13 patients presenting PSA values<2 ng/ml. CONCLUSION: 18F-fluorocholine 3-phase PET/CT showed a progressively increasing SUVmax in biopsy confirmed cancer lesions up to 14 minutes post injection while decreasing in inguinal lymph nodes interpreted as benign. Furthermore, it was very useful in differentiating local recurrences from confounding blood pool and urinary activity.