Detection and quantification of focal uptake in head and neck tumours: 18F-FDG PET/MR versus PET/CT

Purpose: Our objectives were to assess the quality of PET images and coregistered anatomic images obtained with PET/MR, to evaluate the detection of focal uptake and SUV, and to compare these findings with those of PET/CT in patients with head and neck tumours. Methods: The study group comprised 32 consecutive patients with malignant head and neck tumours who underwent whole-body 18F-FDG PET/MR and PET/CT. PET images were reconstructed using the attenuation correction sequence for PET/MR and CT for PET/CT. Two experienced observers evaluated the anonymized data. They evaluated image and fusion quality, lesion conspicuity, anatomic location, number and size of categorized (benign versus assumed malignant) lesions with focal uptake. Region of interest (ROI) analysis was performed to determine SUVs of lesions and organs for both modalities. Statistical analysis considered data clustering due to multiple lesions per patient. Results: PET/MR coregistration and image fusion was feasible in all patients. The analysis included 66 malignant lesions (tumours, metastatic lymph nodes and distant metastases), 136 benign lesions and 470 organ ROIs. There was no statistically significant difference between PET/MR and PET/CT regarding rating scores for image quality, fusion quality, lesion conspicuity or anatomic location, number of detected lesions and number of patients with and without malignant lesions. A high correlation was observed for SUVmean and SUVmax measured on PET/MR and PET/CT for malignant lesions, benign lesions and organs (ρ = 0.787 to 0.877, p < 0.001). SUVmean and SUVmax measured on PET/MR were significantly lower than on PET/CT for malignant tumours, metastatic neck nodes, benign lesions, bone marrow, and liver (p < 0.05). The main factor affecting the difference between SUVs in malignant lesions was tumour size (p < 0.01). Conclusion: In patients with head and neck tumours, PET/MR showed equivalent performance to PET/CT in terms of qualitative results. Comparison of SUVs revealed an excellent correlation for measurements on both modalities, but underestimation of SUVs measured on PET/MR as compared to PET/CT

Spatio-temporal sampling strategies and spiral imaging for translational cardiac MRI

Magnetic Resonance Imaging is a reference tool to assess myocardial function and viability, the two key measurements in clinics. However, several technical challenges remain. This thesis focuses on the development of new strategies to provide an efficient characterization of the myocardium. Using tools provided by MR physics and image processing a translational "bench-to-bedside" approach was adopted. Concerning the "bench", Manganese was studied as a contrast agent for myocardial viability assessment. A new cine sequence, "interleaved cine", was also developed to increase the time resolution and opens up the possibility of stress studies in mice on clinical scanners. In parallel, spiral imaging was applied to the "bedside". In the context of real-time imaging, the proposed reconstruction method, k-t SPIRE, takes into account the temporal information of data which helps to resolve the undersampling artifacts and showed important improvements compared to the classical method both in numerical simulations and in-vivo

90Yttrium PET/MR-based dosimetry after liver radioembolization (SIRT)

Biodistribution and dosimetric aspects are important issues in the preparation realization of radionuclide therapies and thus play an emerging role in radioembolization of liver malignancies. Biodistribution assessment of liver selective internal radiotherapy (SIRT) has been shown feasible using PET/CT PET/magnetic resonance (MR). Whereas prospective dosimetry using 99mTc macroaggregated albumin SPECT/CT is discussed controversially, retrospective 90Y PET/CT has been shown feasible for dosimetry of SIRT in recent studies. Considering the advantages of PET/MR with regard to lesion detection radiation dose reduction compared to PET/CT, especially when repeated scanning is intended, we investigated the use of PET/MR for dosimetry of liver SIRT

Comparing dynamic susceptibility contrast perfusion post-processing with different clinically available software among patients affected of a high-grade glioma

The main purpose of this retrospective study was to evaluate inter-software variability in patients affected of a high-grade glioma for the post-processing of dynamic susceptibility contrast (DSC1) perfusion imaging in MRI.2 MATERIALS AND METHODS: The included patients were either anaplastic astrocytoma (WHO3 grade III) or glioblastoma (WHO grade IV) located in the cerebral parenchyma. The postprocessing of 54 MRI-DSC imaging from 46 patients using both Intellispace© (Philips) and Olea© (Olea Medical) software was performed. The hemodynamic parameter studied was the normalised relative cerebral blood volume corrected for the T1 leakage effect (nrCBVc4). The inter-operator variabilities were also evaluated

Hybrid PET/MRI as a tool to detect brown adipose tissue: Proof of principle

The purpose of this study was to assess the performance of (18)F-FDG hybrid PET/MRI to detect and localise the presence of metabolically active brown adipose tissue (BAT)