[Molecular imaging of head and neck cancers : Perspectives of PET/MRI]. / Molekulare Bildgebung bei Kopf-Hals-Tumoren : Perspektive der PET-MRT.

BACKGROUND: The (18)F-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG-PET/CT) procedure is a cornerstone in the diagnostics of head and neck cancers. Several years ago PET-magnetic resonance imaging (PET/MRI) also became available as an alternative hybrid multimodal imaging method. OBJECTIVE: Does PET/MRI have advantages over PET/CT in the diagnostics of head and neck cancers? MATERIAL AND METHODS: The diagnostic accuracy of the standard imaging methods CT, MRI and PET/CT is depicted according to currently available meta-analyses and studies concerning the use of PET/MRI for these indications are summarized. RESULTS: In all studies published up to now PET/MRI did not show superiority regarding the diagnostic accuracy in head and neck cancers; however, there is some evidence that in the future PET/MRI can contribute to tumor characterization and possibly be used to predict tumor response to therapy with the use of multiparametric imaging. CONCLUSION: Currently, (18)F-FDG-PET/CT is not outperformed by PET/MRI in the diagnostics of head and neck cancers. The additive value of PET/MRI due to the use of multiparametric imaging needs to be investigated in future research.

Simultaneous [18F]FDG-PET/MRI: Correlation of Apparent Diffusion Coefficient (ADC) and Standardized Uptake Value (SUV) in Primary and Recurrent Cervical Cancer.

OBJECTIVES: Previous non-simultaneous PET/MR studies have shown heterogeneous results about the correlation between standardized uptake values (SUVs) and apparent diffusion coefficients (ADCs). The aim of this study was to investigate correlations in patients with primary and recurrent tumors using a simultaneous PET/MRI system which could lead to a better understanding of tumor biology and might play a role in early response assessment. METHODS: We included 31 patients with histologically confirmed primary (n = 14) or recurrent cervical cancer (n = 17) who underwent simultaneous whole-body 18F-FDG-PET/MRI comprising DWI. Image analysis was performed by a radiologist and a nuclear physician who identified tumor margins and quantified ADC and SUV. Pearson correlations were calculated to investigate the association between ADC and SUV. RESULTS: 92 lesions were detected. We found a significant inverse correlation between SUVmax and ADCmin (r = -0.532, p = 0.05) in primary tumors as well as in primary metastases (r = -0.362, p = 0.05) and between SUVmean and ADCmin (r = -0.403, p = 0.03). In recurrent local tumors we found correlations for SUVmax and ADCmin (r = -0.747, p = 0.002) and SUVmean and ADCmin (r = -0.773, p = 0.001). Associations for recurrent metastases were not significant (p>0.05). CONCLUSIONS: Our study demonstrates the feasibility of fast and reliable measurement of SUV and ADC with simultaneous PET/MRI. In patients with cervical cancer we found significant inverse correlations for SUV and ADC which could play a major role for further tumor characterization and therapy decisions.

Combined PET/MR: The Real Work Has Just Started. Summary Report of the Third International Workshop on PET/MR Imaging; February 17-21, 2014, Tübingen, Germany.

This paper summarises the proceedings and discussions at the third annual workshop held in Tübingen, Germany, dedicated to the advancement of the technical, scientific and clinical applications of combined PET/MRI systems in humans. Two days of basic scientific and technical instructions with "hands-on" tutorials were followed by 3 days of invited presentations from active researchers in this and associated fields augmented by round-table discussions and dialogue boards with specific themes. These included the use of PET/MRI in paediatric oncology and in adult neurology, oncology and cardiology, the development of multi-parametric analyses, and efforts to standardise PET/MRI examinations to allow pooling of data for evaluating the technology. A poll taken on the final day demonstrated that over 50 % of those present felt that while PET/MRI technology underwent an inevitable slump after its much-anticipated initial launch, it was now entering a period of slow, progressive development, with new key applications emerging. In particular, researchers are focusing on exploiting the complementary nature of the physiological (PET) and biochemical (MRI/MRS) data within the morphological framework (MRI) that these devices can provide. Much of the discussion was summed up on the final day when one speaker commented on the state of PET/MRI: "the real work has just started".

Initial clinical results of simultaneous 18F-FDG PET/MRI in comparison to 18F-FDG PET/CT in patients with head and neck cancer.

PURPOSE: The aim of this study was to evaluate the diagnostic capability of simultaneous (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/MRI compared to (18)F-FDG PET/CT as well as their single components in head and neck cancer patients. METHODS: In a prospective study 17 patients underwent (18)F-FDG PET/CT for staging or follow-up and an additional (18)F-FDG PET/MRI scan with whole-body imaging and dedicated examination of the neck. MRI, CT and PET images as well as PET/MRI and PET/CT examinations were evaluated independently and in a blinded fashion by two reader groups. Results were compared with the reference standard (final diagnosis determined in consensus using all available data including histology and follow-up). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated. RESULTS: A total of 23 malignant tumours were found with the reference standard. PET/CT showed a sensitivity of 82.7%, a specificity of 87.3%, a PPV of 73.2% and a NPV of 92.4%. Corresponding values for PET/MRI were 80.5, 88.2, 75.6 and 92.5%. No statistically significant difference in diagnostic capability could be found between PET/CT and PET/MRI. Evaluation of the PET part from PET/CT revealed highest sensitivity of 95.7%, and MRI showed best specificity of 96.4%. There was a high inter-rater agreement in all modalities (Cohen's kappa 0.61-0.82). CONCLUSION: PET/MRI of patients with head and neck cancer yielded good diagnostic capability, similar to PET/CT. Further studies on larger cohorts to prove these first results seem justified.

Placental localization and expression of the cell death factors BNip3 and Nix in preeclampsia, intrauterine growth retardation and HELLP syndrome.

OBJECTIVE: BNip3 and its homologue Nix are pro-apoptotic factors of the Bcl-2-family and are expressed in malignant tumors. In vitro, this expression was shown to be mediated by hypoxia. Recently, it has been shown that placental hypoxia as well as apoptosis are pathogenetic factors for pregnancy-induced hypertensive diseases and intrauterine growth retardation (IUGR). The aim of the study was to analyze placental expression of BNip3 and Nix in pregnancies complicated by preeclampsia, hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome and IUGR. MATERIAL AND METHODS: Placental tissue was sampled from 10 pregnancies each with preeclampsia, HELLP syndrome, IUGR and gestational age-matched controls. The placental expression of BNip3/Nix has been investigated with immunohistochemistry by the use of specific human BNip3/Nix antibodies. RESULTS: In cytotrophoblastic cells, the BNip3 expression was strong in the control placentas, but only mediate in the placentas from pregnancies with preeclampsia, IUGR or HELLP syndrome. The intensity of the Nix staining showed a similar pattern. In the syncytiotrophoblast, there was a weak BNip3 staining observable in the control as well as IUGR samples, whereas BNip3 was undetectable in preeclamptic placentas or those with HELLP syndrome. For Nix, only in the preeclampsia a weak staining was detectable, whereas all other probes were negative. CONCLUSIONS: Our study shows for the first time that the pro-apoptotic proteins BNip3 and Nix are expressed in the human placenta. Pregnancies with placental dysfunction and hypertensive pregnancy disorders with different clinical manifestations are characterized by a significantly decreased expression of BNip3 and Nix. These results suggest that the hypothesis of generally increased placental apoptosis in pregnancy-induced hypertensive disorders caused by disturbed trophoblast invasion has to be partly reconsidered.