The aim of this study was to compare integrated PET/CT and PET/MRI for their usefulness in detecting and categorizing cervical iodine-positive lesions in patients with differentiated thyroid cancer using 124I as tracer.

SummaryAim: A theoretical dosimetry-based model was applied to estimate the lowest effective radioiodine activity for thyroid remnant ablation of low-risk differentiated thyroid cancer patients. Patients, methods: The model is based on the distribution of the absorbed (radiation) dose per administered radioiodine activity and the absorbed dose threshold of 300 Gy for thyroid remnants, the level believed to destroy most thyroid remnants. For this purpose, 124I PET/CT images of 49 thyroid-ectomised patients were retrospectively analysed to measure the distribution of the (average) absorbed doses to thyroid remnant per administered 131I activity. The fraction of thyroid remnants that received at least 300 Gy was determined for standard activities between 0.37 and 5.55 GBq. The lower activity was considered to be equally effective to that obtained with higher activity if the (absolute) fraction difference was below 5%. Results: A total of 62 thyroid remnants were included. The medians and ranges (in parentheses) for the absorbed dose per unit 131I activity were 359 Gy/GBq (34 to 1825 Gy/ GBq). The fractions of thyroid remnants receiving more than 300 Gy at different therapy activities (within parentheses) were 60% (1.11 GBq), 76% (1.85 GBq), 79% (2.22 GBq), and 81–82% for activities between 2.59 and 3.70 GBq. The therapy activity of 1.11 GBq is considerably less effective than that of 1.85 or 2.22 GBq; therapy activities were equally effective in the range between 2.22 to 3.70 GBq. Conclusion: On the basis of the model and the patients' data included, the lowest effective therapy activity appears to be approximately 2.2 GBq to ablate thyroid remnants. The results of this study may help to guide the design of prospective clinical studies.

Ziel der Studie war es zu untersuchen, ob die Therapieevaluation bei Patienten mit HCC nach SIRT mittels Gd-EOB MRT durch eine zusätzliche diffusionsgewichtete Bildgebung (DWI) verbessert werden kann.

Aim: Several studies described the ultrasound based real-time elastography (USE) having a high sensitivity, specificity and negative predictive value in the diagnosis of suspicious thyroid nodules. Recently published studies called these results into question. Until now the usefulness of USE in the diagnosis of scintigraphically hyperfunctional thyroid nodules is not examined. Patients, methods: This study included 135 hyperfunctional thyroid nodules of 102 consecutive patients. The following attributes of the nodules were analyzed: stiffness with the USE using scores of Rago or Asteria and ultrasound criteria using TIRADS. Results: 94 of the examined thyroid nodules (70%) were rated as hard (suspicious for malignancy) and 41 nodules (30%) as soft (not suspicious) with a specificity of 30%. The scoring systems of Rago and Asteria showed no significant difference. Applying the TIRADS criteria 44 nodules (33%) have a higher risk for malignancy (33 nodules TIRADS 4a, 11 nodules TIRADS 4b). Combining USE and TIRADS 32 nodules (24%) are categorized as suspicious (intersection of hard nodules that are categorized as TIRADS 4a or 4b). Conclusion: Ultrasound based real-time elastography cannot identify scintigraphically hyperfunctional thyroid nodules as benign nodules reliably. Its accuracy in the assessment of at least "hot" thyroid nodules is to be questioned.

Die Ganzkörper-MRT ist seit einigen Jahren technisch möglich und findet immer weitere Anwendungsgebiete in der Medizin. Hierzu zählen insbesondere Anwendungen in der Prävention und der Ausbreitungsdiagnostik bei neoplastischen Erkrankungen. Jedoch muss in einzelnen Feldern die genaue diagnostische Wertigkeit des Verfahrens noch evaluiert werden. Zudem darf die Ganzkörperbildgebung nicht kritiklos angewandt werden, sondern es muss zwischen der Ganzkörper-MRT und dedizierter sowie ausführlicher Untersuchung eines Organsystems abgewogen werden.

Ziele: Evaluierung des klinischen Einsatzes der neuen Methode der simultanen (18F)FDG PET/MRT bei Patienten mit Kopf-Hals Tumoren. Methode: 15 konsekutive Patienten mit histologisch gesicherten Tumoren der Kopf-Hals-Region wurden direkt im Anschluss an eine (18F) FDG PET-CT mit der simultanen (18F) FDG PET/MRT (Siemens MMR Biograph) untersucht. Das Sequenzprotokoll bestand aus einer STIR-Sequenz, nativen T1-gewichteten Sequenzen in coronaler und transversaler Schichtführung, nativen T2 gewichteten Sequenzen transversal, T1-gewichteten Sequenzen nach Kontrastmittel mit Fettsättigung transversal und coronal sowie einer diffusionsgewichteten Sequenz. Die simultane Akquisition der PET-Daten erfolgte mit LSO basierten AP-Dioden und einem FoV von 25,8 cm. Ergebnis: Alle Bilddatensätze waren von diagnostischer Qualität. Die simultane Akquisition der PET-Daten war in allen untersuchten Patienten störungsfrei möglich und zeigte eine sehr hohe Übereinstimmung mit den PET-Daten der vorher durchgeführten PET/CT. Die Nachverarbeitung inklusive Fusionierung erlaubte eine exakte anatomische Korrelation eines erhöhten Glukosemetabolismus. Schlussfolgerung: Die neue Methode der simultanen (18F) FDG PET/MRT von Kopf/Hals Tumoren eignet sich für den klinischen Routinebetrieb und erlaubt eine detaillierte anatomische Einordnung sowie Abgrenzung von Primärtumoren und Lymphknoten mit pathologischem Glukosemetabolismus.

Summary For an adequate therapy planning and staging of patients with differentiated thyroid cancer (DTC), the correct assignment of thyroid remnants (TRs) and lymph node metastases (LMs) is important. Patients, method: We retrospectively analyzed whether kinetic quantities can help improving LM assignment using serial 124I-PET/CT data. 127 patients with a total of 317 lesions (TR: n = 265; LM: n = 52) received pre-therapy 124I-PET/CT lesion dosimetry using images 24 h and > 96 h after 124I administration. For each lesion, maximum activity concentration (MAC) at 24 h and effective half-life (EHL) were determined. Moreover, the product of MAC and EHL was also investigated as a quantity and is referred to CAQ (cumulated activity proportional quantity). In addition, differences between endogenous and exogenous thyroid-stimulating hormone (TSH) stimulation and between papillary (PTC) and follicular thyroid cancer (FTC) were investigated. Results, conclusion: The median MAC, EHL, and CAQ values in TR were significantly higher than in LM but a clinically relevant cut-off value could not be determined because of high overlapping regions. No significant differences for the three quantities were found for the mode of TSH stimulations, but a significant difference for MAC and CAQ between PTC and FTC.