Dynamic ⁶⁸Ga-DOTATOC PET/CT and static image in NET patients

Summary

Purpose: To investigate the relationship between the dynamic parameters (K_i) and static image-derived parameters of ⁶⁸Ga-DOTATOC-PET, to determine which static parameter best reflects underlying somatostatin-receptor-expression (SSR) levels on neuroendocrine tumours (NETs). Patients, methods: 20 patients with metastasized NETs underwent a dynamic and static ⁶⁸Ga-DOTATOC-PET before PRRT and at 7 and 40 weeks after the first administration of ⁹⁰Y-DOTATOC (in total 4 cycles were planned); 175 lesions were defined and analyzed on the dynamic as well as static scans. Quantitative analysis was performed using the software PMOD. One to five target lesions per patient were chosen and delineated manually on the baseline dynamic scan and further, on the corresponding static ⁶⁸Ga-DOTATOC-PET and the dynamic and static ⁶⁸Ga-DOTATOC-PET at the other time-points; SUV_max and SUV_mean of the lesions was assessed on the other six scans. The input function was retrieved from the abdominal aorta on the images. Further on, K_i was calculated using the Patlak-Plot. At last, 5 reference regions for normalization of SUV_tumour were delineated on the static scans resulting in 5 ratios (SUV_ratio). Results: SUV_max and SUV_mean of the tumoural lesions on the dynamic ⁶⁸Ga-DO-TATOC-PET had a very strong correlation with the corresponding parameters in the static scan (R²: 0.94 and 0.95 respectively). SUV_max, SUV_mean and K_i of the lesions showed a good linear correlation; the SUV_ratios correlated poorly with K_i. A significantly better correlation was noticed between K_i and SUV_tumour(_{max and mean}) (p < 0.0001). Conclusions: As the dynamic para meter K_i correlates best with the absolute SUV_tumour, SUV_tumour best reflects underlying SSR-levels in NETs.

Zusammenfassung

Das Ziel der Studie war das Verhältnis zwischen dem dynamischen Parameter (K_i) und statischen Parametern der ⁶⁸Ga-DOTATOC-PET zu untersuchen und den statischen Parameter zu definieren, der am besten mit der Somatostatinrezeptor (SSR) Expression von neuroendokrinen Tumoren (NET) korreliert. Patienten und Methoden: 20 Patienten mit metastasierten NET erhielten eine dynamische und statische ⁶⁸Ga-DOTATOC-PET vor der ersten PRRT und 7 und 40 Wochen nach der ersten Administration von ⁹⁰Y-DOTATOC (insgesamt wurden 4 Zyklen geplant); 175 Läsionen wurden auf den statischen und dynamischen Bildern definiert und ausgewertet. Die quantitative Analyse wurde mit der Software PMOD durchgeführt. Eine bis fünf Zielläsionen wurden pro Patient im ersten dynamischen Scan ausgewählt, mit einer VOI versehen, welche dann auf die weiteren dynamischen und statischen Scans transferiert wurde; sowohl SUV_max als auch SUV_mean wurden bestimmt. Die Input Funktion wurde aus der im Field-of-view liegenden Aorta generiert. K_i wurde mit Hilfe des Patlak-Plots berechnet. Zuletzt wurden 5 Referenzregionen für die Normalisation des SUV_tumo auf den statischen Scans bestimmt, zur Bestimmung von 5 Verhältnissen (SUV_ratio). Ergebnisse: SUV_max und SUV_mean der Tumorläsionen inden dynamischen ⁶⁸Ga-DOTATOC-PET zeigten eine sehr starke Korrelation mit den entsprechenden Parametern in den statischen Scans (R²: 0,94 bzw. 0,95). SUV_max, SUV_mean und K_i der Läsionen zeigte eine gute lineare Korrelation; die verschiedenen SUV_ratios korrelierten auf sehr niedrigem Niveau mit K_i. Eine signifikant bessere Korrelation zeigte sich zwischen K_i und SUV_{tumour(max and mean)} (p < 0.0001). Schlussfolgerung: Der dynamische Parameter K_i korreliert am besten mit dem absoluten SUV_tumour. SUV_tumour reflektiert am besten den Level der SSR-Expression in NET.

Keywords

⁶⁸Ga-DOTATOC PET - K_i - somatostatin receptor expression - PRRT - neuroendocrine tumour

Schlüsselwörter

⁶⁸Ga-DOTATOC PET - K_i - Somatostatinrezeptor-Expression - PRRT - neuroendokriner Tumor

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