Einsatz von MR/PET in der onkologischen Bildgebung

Zusammenfassung

Der folgende Übersichtsartikel präsentiert die Möglichkeiten, die sich mit der Hybridbildgebung an einem Magnetresonanz-Positronenemissionstomografen (MR/PET) ergeben. Mit den seit Kurzem zur Verfügung stehenden Ganzkörper-MR/PET-Scannern ist es möglich, die Vorteile beider Modalitäten außerhalb des Kopfes zu kombinieren. Dabei sind beide Modalitäten gefordert: auf Seiten des MRT ist die Bereitstellung hochaufgelöster anatomischer Bilder essenziell. Zusätzlich spielen funktionelle Methoden wie die diffusionsgewichtete Bildgebung (DWI), Spektroskopie und die Kontrastmitteldynamik eine wichtige Rolle. Auf Seiten der PET besteht die technische Herausforderung v. a. in der Bereitstellung einer geeigneten MR-basierten Schwächungskorrektur für die PET-Daten. Mit der Hybridbildgebung an einem MR/PET gelingt es, in einer Untersuchung sowohl morphologische als auch funktionelle Parameter zu erfassen. Es zeichnet sich ab, dass von diesem neuen hybriden Bildgebungsverfahren bei onkologischen Fragestellungen insbesondere Kinder und jüngere Erwachsene mit mehreren Verlaufskontrollen profitieren werden. Zum anderen werden sich für bestimmte Krankheitsbilder, bei denen regelhaft eine MRT- und eine PET/CT-Untersuchung durchgeführt werden, Vorteile ergeben. Dennoch ist zu erwarten, dass die MR/PET die PET/CT nicht ersetzen wird, da die PET/CT aufgrund ihrer Kosteneffizienz und der guten Verfügbarkeit weiter führend bleiben dürfte. Zudem existieren in der Lungendiagnostik nach wie vor Einschränkungen in der MRT. Für Forschungsbelange eröffnet insbesondere die simultane MR/PET neue Möglichkeiten, sei es in der Herzbildgebung, in funktionellen Hirnstudien oder bei der Erprobung neuer Tracer in Korrelation mit speziellen MR-Techniken. Die MR/PET stellt ein vielversprechendes Verfahren dar, mit dem in einer Strahlendosis-sparenden Untersuchung multimodal 2 Untersuchungen kombiniert durchgeführt werden können. Welche Krankheitsbilder konkret von dieser neuen Technik profitieren können, wird in prospektiven Studien zu klären sein.

Abstract

The present review aims to depict the possibilities offered by hybrid imaging with magnetic resonance positron emission tomography (MR/PET). Recently, new whole-body MR/PET scanners were introduced allowing for the combination of both modalities outside the brain. This is a challenge for both modalities: For MRI, it is essential to provide anatomical images with high resolution. Additionally, diffusion-weighted imaging (DWI), proton spectroscopy, but also dynamic contrast-enhanced imaging plays an important role. With regard to PET, the technical challenge mainly consists of obtaining an appropriate MR-based attenuation correction for the PET data. Using MR/PET, it is possible to acquire morphological and functional data in one examination. In particular, children and young adults will benefit from this new hybrid technique, especially in oncologic imaging with multiple follow-up examinations. However, it is expected that PET/CT will not be replaced completely by MR/PET because PET/CT is less cost-intensive and more widely available. Moreover, in lung imaging, MRI limitations still have to be accepted. Concerning research, simultaneous MR/PET offers a variety of new possibilities, for example cardiac imaging, functional brain studies or the evaluation of new tracers in correlation with specific MR techniques.

Key words

MR imaging - PET/CT - PET - MR/PET

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