Comparison of ¹⁸F-FDG and ⁶⁷Ga-citrate in sarcoidosis imaging

Summary

Aim: ⁶⁷Ga citrate has been used long and successfully to diagnose and stage sarcoidosis. ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) has been suggested as a positron emission tomography (PET) tracer for sarcoidosis imaging. This study aimed to analyze possible advantages of ¹⁸F-FDG-PET over ⁶⁷Ga citrate scintigraphy during the primary assessment of patients with sarcoidosis. Patients and methods: Twentyfour patients (11 men, 13 women, aged 52 years ±12.4) with histologically proven sarcoidosis were investigated with ¹⁸F-FDG and ⁶⁷Ga citrate. Equipment included a fullring PET scanner (ECAT EXACT HR+, Siemens/CTI, Knoxville TN, USA) and a double-headed gamma camera (ECAM, Siemens, Illinois, USA) for scintigraphy. The mean time difference between the two studies was 6.5 days (range: 5–8 days). Results: There was a significant difference in the detection of pulmonary and nonpulmonary sarcoidosis lesions between planar ⁶⁷Ga citrate scans and ¹⁸F-FDG-PET images (<0.0021). A total of 64 lesions were detected with ⁶⁷Ga citrate scans in the thorax and elsewhere with a mean of 2.6 lesions (4%) per patient, while 85 lesions were found with ¹⁸F-FDG-PET, with a mean of 3.5 lesions (4.1%) per patient. There was complete agreement between ¹⁸F-FDG and ⁶⁷Ga citrate in thoracic manifestations in four (16.6%) patients, and in non-thoracic manifestations in five (20.8%) patients. The interobserver variability showed a kappa value of 0.79. Conclusion: ⁶⁷Ga citrate and ¹⁸F-FDG are useful tracers for diagnostic evaluation of thoracic sarcoidosis. ¹⁸F-FDG seems to be more suitable for imaging the mediastinum, the bi-hilar lymph nodes, the posterior regions of the lungs and non-thoracic lesions. Further prospective studies are needed to clarify the role of both tracers in early diagnosis and staging of sarcoidosis, and to resolve questions concerning medical treatment and follow-up.

Zusammenfassung

⁶⁷Ga-Zitrat wird seit Jahren erfolgreich zur Diagnose und zur Stadieneinteilung von Sarkoidose verwendet. ¹⁸F-Fluordeoxyglukose wird auch als Tracer zur Positronenemissionstomographie (PET) für die Diagnostik der Sarkoidose vorgeschlagen. Ziel dieser Studie ist es, die möglichen Vorteile von ¹⁸F-FDG-PET gegenüber ⁶⁷Ga-Zitrat-Szintigraphie bei Patienten mit Sarkoidose zu analysieren. Patienten und Methode: Vierundzwanzig Patienten (11 Männer, 13 Frauen: 52 ±12,4 Jahre) mit histologisch verifizierter Sarkoidose sind unter Verwendung von ¹⁸F-FDG und ⁶⁷Ga-Zitrat untersucht worden. Die Studie ist an einem dedizierten PET-Scanner (ECAT EXACT HR+, Siemens/CTI, Knoxville TN, USA) und an einer Doppelkopf Gammakamera (ECAM, Siemens, Illinois, USA) durchgeführt worden. Das Zeitintervall zwischen beiden Untersuchungen hat 6,5 Tage (fünf bis acht Tage) betragen. Ergebnisse: Es konnte ein signifikantes Ergebnis (<0,0021) in der Analyse pulmonaler und extrapulmonaler Läsionen zwischen planaren ⁶⁷Ga-Zitrat- und ¹⁸F-FDG-Aufnahmen gezeigt werden. Eine komplette übereinstimmung zwischen ¹⁸F-FDG und ⁶⁷Ga-Zitrat bei thorakalen Manifestationen kann bei vier (16,6%) Patienten, bei extrathorakalen Manifestationen bei fünf (20,8%) Patienten beobachtet werden. Die Interobservervariabilität beider Untersucher zeigt einen kappa Wert von 0,79. Schlussfolgerung: ⁶⁷Ga-Zitrat und ¹⁸F-FDG sind sensitive Tracer zur diagnostischen Evaluierung von Sarkoidose. ¹⁸F-FDG erscheint vorteilhaft in der Diagnostik des Mediastinums, bihilärer Lymphknotengruppen und pathologisch speichernder Herde der dorsalen Lungenregionen und extrathorakaler Manifestationen. Weitere prospektive Studien sind jedoch erforderlich, um die Rolle beider Tracer in der Frühdiagnose und Stadieneinteilung von Sarkoidose zu klären und die Fragen bezüglich Nachfolgeuntersuchungen unter medikamentöser Behandlung zu lösen.

Keywords

Sarcoidosis - 67 gallium citrate - ¹⁸F-FDG

Schlüsselwörter

Sarkoidose - Gallium-67-zitrat - ¹⁸F-FDG

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