Der Nuklearmediziner 2015; 38(04): 275-282
DOI: 10.1055/s-0035-1564201
Normvarianten und Varianten bei PET/CT-Untersuchungen
© Georg Thieme Verlag KG Stuttgart · New York

Typische falsch negative und falsch positive Befunde bei der FDG-PET/CT

Typical False Negative and False Positive Findings on FDG PET/CT
B. Schmidbauer
1   Abteilung für Nuklearmedizin, Universitätsklinikum Regensburg, Regensburg
,
D. Hellwig
1   Abteilung für Nuklearmedizin, Universitätsklinikum Regensburg, Regensburg
› Author Affiliations
Further Information

Publication History

Publication Date:
15 December 2015 (online)

Zusammenfassung

Die FDG-PET/CT ist ein wichtiges diagnostisches Instrument bei onkologischen Fragestellungen und entwickelt sich immer mehr zur Standarddiagnostik. Darüber hinaus ist es ein zunehmend nachgefragtes Verfahren zur Entzündungsdiagnostik und Lokalisation eines Infektfokus. Umso bedeutsamer ist es daher, sich typischer Fallstricke bei der Befundung gewahr zu sein. Der folgende Beitrag soll daher eine Übersicht über typische erkrankungsbedingt falsch positive sowie falsch negative Befunde verschaffen. Hierzu erfolgt eine selektive Darstellung der aktuellen Literatur mit Illustration durch Bildbeispiele.

Differenzialdiagnostisch zu bedenken ist bei erhöhtem FDG-Uptake insbesondere ein entzündliches Geschehen. Daneben kann es auch im Rahmen der Therapie, bspw. nach Chemo- oder Immuntherapie, Bestrahlung oder durch Zytokine, zu Veränderungen der FDG-Aufnahme in Lymphknoten, Knochenmark oder sonstigen Organen kommen. Die Aktivierung von braunem Fettgewebe führt zu vermehrter FDG-Aufnahme. Auch die Aufnahmetechnik und Patientenvorbereitung bergen einige Fehlerquellen. Ungenauigkeiten der Koregistrierung von PET und CT, Artefakte durch röntgendichte Strukturen wie Metallimplantate sowie Atmungsartefakte können die Befundung erschweren. Oftmals ist hier die zusätzliche morphologische Information aus der computertomografischen Komponente der Untersuchung hilfreich.

Kleine Herde können dem Nachweis entgehen und Hyperglykämie kann falsch negative Befunde bedingen. Einige Tumorentitäten können FDG-negativ sein, insbesondere Bronchioloalveolarzell-Karzinome, muzinöse Tumoren, neuroendokrine Karzinome, Prostatakarzinome, hepatozelluläre Karzinome, Nierenzellkarzinome und niedriggradige maligne Gliome. Für einige dieser Erkrankungen stehen spezifische PET-Tracer zur Verfügung. Optimal ist die umfassende Bewertung aller Informationen aus Anamnese, Klinik und Bildmaterial.

Abstract

FDG PET/CT is a powerful diagnostic tool in oncology evolving to the diagnostic standard. Moreover it is increasingly ordered for the evaluation of inflammations and for the detection of infectious foci. So it is important to know characteristic pitfalls when reading the images. The following article provides an overview of characteristic false positive and false negative findings. To do so we surveyed recent relevant publications. Patient examples illustrate typical findings.

Inflammations must be considered as the main differential diagnosis for increased FDG uptake. Beside this, prior treatments like chemotherapy, radiotherapy or cytokins may also cause elevated FDG uptake in lymph nodes, bone marrow or further organs. The activation of brown adipose tissue leads to increased FDG uptake. Acquisition technique and improper patient preparation include several sources of error. Misregistrations between PET and CT, artifacts from radiopaque structures like metallic implants, or breathing artifacts may hamper image interpretation. Often, additional anatomical information from the CT component of the study is helpful.

Small lesions may be missed and hyperglycemia can cause false negative findings. Several tumor entities may be FDG negative. Examples are bronchioloalveolar carcinoma, mucinous tumors, neuroendocrine tumors, prostate cancer, hepatocellular carcinoma, renal cell carcinoma as well as low-grade glioma. For some of these malgnancies, specific PET tracers are clinically available. For the best results, all available information from history taking, physical examination and imaging findings is comprehensively assessed.

 
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