DWI und PET/MRT nach Strahlentherapie bei malignen Kopf-Hals-Tumoren^[1]

Zusammenfassung

Die Interpretation von Bildgebungsbefunden des bestrahlten Halses stellt wegen der durch die Strahlentherapie induzierten (radiogenen) Gewebeveränderungen, des variablen Erscheinungsbilds von Tumorrezidiven sowie funktions- und stoffwechselbezogener Phänomene, die dem Erscheinungsbild einer Krankheit zum Verwechseln ähnlich sind, eine Herausforderung dar. Zur Erleichterung der Diagnose werden daher in der klinischen Praxis immer häufiger folgende Verfahren angewendet: die morphologisch orientierte MRT (Magnetresonanztomografie), die DWI (diffusionsgewichtete Bildgebung), die PET/CT (Positronenemissionstomografie mit Computertomografie) sowie die Fusion von PET- und MRT-Befunden mithilfe einer entsprechenden Software. Da MRT und PET in vielen Fällen komplementäre Informationen liefern, lässt die kombinierte PET/MRT-Bildgebung auf eine Erleichterung der Unterscheidung zwischen Tumorrezidiven, radiogenen Veränderungen und Komplikationen hoffen. Im Mittelpunkt dieses Review stehen die klinischen Anwendungen von DWI und PET/MRT am bestrahlten Hals und die Erörterung des Zugewinns bei der Lösung diagnostischer Probleme durch die multiparametrische Bildgebung. Radiologen sollten wissen, welche DWI- und PET/MRT-Befunde kennzeichnend für die wichtigsten strahlentherapieinduzierten Gewebeveränderungen und die potenziellen Komplikationen sind: für Ödeme, Fibrosen, Vernarbungen, Weichgewebenekrosen, Knochen- und Knorpelnekrosen, Hirnnervenlähmungen und radiogene Arteriosklerose, Hirnnekrosen und Schilddrüsenerkrankungen. DWI und PET/MRT ergänzen sich auch bei der Fahndung nach residualem Tumorgewebe und Rezidiven. Mögliche technik-, funktions- oder stoffwechselbedingte Fehlerquellen bei der Interpretation sollten erkannt und vermieden werden. Vertrautheit mit den Charakteristika der zu erwartenden DWI- und PET/MRT-Befunde, mit potenziellen Komplikationen und Therapieversagen nach Strahlentherapie erhöht die diagnostische Sicherheit bei der Interpretation von Aufnahmen des bestrahlten Halses.

Abstract

Interpreting imaging studies of the irradiated neck constitutes a challenge because of radiation therapy-induced tissue alterations, the variable appearances of recurrent tumors, and functional and metabolic phenomena that mimic disease. Therefore, morphologic magnetic resonance (MR) imaging, diffusion-weighted (DW) imaging, positron emission tomography with computed tomography (PET/CT), and software fusion of PET and MR imaging data sets are increasingly used to facilitate diagnosis in clinical practice. Because MR imaging and PET often yield complementary information, PET/MR imaging holds promise to facilitate differentiation of tumor recurrence from radiation therapy-induced changes and complications. This review focuses on clinical applications of DW and PET/MR imaging in the irradiated neck and discusses the added value of multiparametric imaging to solve diagnostic dilemmas. Radiologists should understand key features of radiation therapy-induced tissue alterations and potential complications seen at DW and PET/MR imaging, including edema, fibrosis, scar tissue, soft-tissue necrosis, bone and cartilage necrosis, cranial nerve palsy, and radiation therapy-induced arteriosclerosis, brain necrosis, and thyroid disorders. DW and PET/MR imaging also play a complementary role in detection of residual and recurrent disease. Interpretation pitfalls due to technical, functional, and metabolic phenomena should be recognized and avoided. Familiarity with DW and PET/MR imaging features of expected findings, potential complications, and treatment failure after radiation therapy increases diagnostic confidence when interpreting images of the irradiated neck.

¹ © 2015 The Radiological Society of North America. All rights reserved. Originally puplished in English in RadioGraphics 2015; 35: 1502 – 1527. Online published in 10.1148 /rg.2015140029. Translated and reprinted with permission of RSNA. RSNA is not responsible for any inaccuracy or error arising from the translation from English to German.

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