Whole-Body [18F]FDG-PET/MRI vs. [18F]FDG-PET/CT in Malignant Melanoma.

PURPOSE: To assess the diagnostic performance of simultaneous whole-body 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) positron emission tomography (PET)/magnetic resonance imaging (MRI) compared to [18F]FDG PET/x-ray computed tomography (CT) for detection of distant metastatic disease in patients with malignant melanoma. PROCEDURES: We included patients with malignant melanoma who underwent a single injection [18F]FDG dual-imaging protocol that included whole-body PET/CT and subsequent whole-body PET/MRI for staging or restaging purposes in a prospective setting. Images from both modalities were analyzed by two rater teams for the presence of metastatic lesions. PET/CT-PET/MRI overall agreement as well as region-based accuracies, sensitivities (Se), and specificities (Sp) were computed. RESULTS: Between July 2014 and December 2018, 22 patients were enrolled. Interrater agreement and overall accuracy (consensus reading) were 78.8 % (95 % CI 71-84.9) and 96.1 % (95 % CI 92.3-98) for PET/MRI and 78 % (70.2-84.3) and 97.4 % (95 % CI 93.7-98.9) for PET/CT, respectively (P = 0.42). PET/MRI reached a region-based Se of 89.1 % (95 % CI 79.4-94.5) and a Sp of 100 %, whereas PET/CT showed a region-based Se of 92.7 % (95 % CI 84-96.9) and a Sp of 100 % for the detection of metastatic disease in malignant melanoma. CONCLUSIONS: Whole-body [18F]FDG-PET/MRI appears to be comparable to [18F]FDG-PET/CT for lesion detection in patients with malignant melanoma.

Is there a reliable size cut-off for splenic involvement in lymphoma? A [18F]FDG-PET controlled study.

PURPOSE: Aim of present study was to determine whether the currently recommended 13-cm cranio-caudal diameter cut-off on CT for assessment of splenic involvement in lymphoma offers adequate sensitivity and specificity. MATERIALS AND METHODS: Patients with histologically proven lymphoma who had undergone [18F]FDG-PET/CT before therapy were included. Cranio-caudal diameters of the spleen were measured on the CT component of PET/CT, and ROC analyses with calculation of respective areas under the curve (AUC) were used to determine cut-off values of cranio-caudal measurements with their respective sensitivities and specificities, using [18F]FDG-PET as the reference standard. RESULTS: In 93 patients, we found a sensitivity of 74.1% and a specificity of 47% for the 13-cm splenic diameter cut-off. CONCLUSIONS: Our results show reasonable, though far from perfect sensitivities and specificities for the currently recommend 13-cm splenic diameter cut-off.

Tumour response of osteosarcoma to neoadjuvant chemotherapy evaluated by magnetic resonance imaging as prognostic factor for outcome.

PURPOSE: This study evaluated the feasibility of computed magnetic resonance imaging (MRI) volumetry in conventional osteosarcomas. Secondly, we investigated whether computed volumetry provides new prognostic indicators for histological response of osteosarcomas after neoadjuvant chemotherapy. METHODS: In a retrospective cohort study, data from the Vienna Bone Tumour Registry was used. MR images from 14 patients (male:female = 1.8, mean age 19 years) were analysed prior to and after neoadjuvant chemotherapy according to current therapy regimens. Histological response to chemotherapy was graded according to the Salzer-Kuntschik classification. Computed volumetry was performed for the intraosseous part, as well as the soft-tissue component and the tumour as a whole. RESULTS: In a setting of appropriate radiological equipment, the method has been considered to be well implementable into clinical routine. The mean tumour volume prior to chemotherapy was 321 (±351) ml. In good responders (n = 6), overall tumour volume decreased by 47% (p = 0.345), whereas poor responders (n = 8) showed a 19% decrease (p = 0.128). Neoadjuvant multidrug therapy remarkably changed the tumour composition. This is seen in a decrease of the mean ratio of soft-tissue to intraosseous tumour volume from 8.67 in poor responders and 1.15 in good responders to 1.26 and 0.45 (p = 0.065), respectively. Interestingly, the bony compartment of good responders showed a volume increase during neoadjuvant chemotherapy (p = 0.073). However, we did not find prognostic markers for histological tumour response to pre-operative chemotherapy. CONCLUSIONS: Separated volumetry of tumour segments revealed interesting insights into therapy-induced growth patterns. If verified in a larger study population, these results should be taken into account when planning ablative surgery.

Nucleophilic cross-linked, dextran coated iron oxide nanoparticles as basis for molecular imaging: synthesis, characterization, visualization and comparison with previous product.

We present a new synthesis protocol for a multivalent, multimodality, nucleophilic nanoparticle ideal for in vivo imaging. Stability requirements necessitated covalent cross-linking of the carbohydrate cage, easy functionalization the introduction of sterically accessible amine groups. The new protocol aimed at more uniform particle size, less clustering and superior magnetic properties compared with commercial nanoparticles. Particles were precipitated from Fe(2+) and Fe(3+) in the presence of 10 kDa dextran monodispersed from the aerosol phase. Cross-linking was achieved with epichlorhydrin, nuclophilication with NH3, purification with ultrafiltration and dialysis. Particles and a commercial product (Rienso®, Takeda Pharma) underwent physicochemical characterizations. Biocompatibility was assessed by Resazurin on LLC-PK1 cells; the internalization rate was measured for three cell lines (HAEC, HASMC, HT29). Core size was 5.61 ± 1.25 nm; hydrodynamic size was 49.56 ± 11.73 nm. The number of sterically accessible amine groups averaged 9.9. The cores showed cubic magnetite structure. Values of r1 and r2 were 10.9 and 148.17 mM(-1) s(-1). Cellular viability was unchanged after incubation. Introduction of aerosol phase dextran resulted in a reduction of the overall hydrodynamic diameter and a narrower size distribution of the synthesized particles. Electron tomography visualized for the first time the postulated 'hairy layer' of the dextran coating and enabled the measurement of the overall diameter of 100.2 ± 7.92 nm. The resulting nanoparticle is biocompatible, functionalizable and detectable at nanomolar concentrations with MRI and optical imaging. It can potentially serve as a platform for multimodal molecular imaging and targeted therapy approaches.