Kinetic analysis of experimental rabbit tumour and inflammation model with ¹⁸F-FDG PET/CT

Summary

Non-specific accumulation of ¹⁸F-FDG by both tumour and inflammatory lesions can make diagnostic analysis difficult. Our aim was to explore the difference in ¹⁸F-FDG uptake kinetics between tumour and inflammatory cells. To this end, we investigated VX2 tumour lesions and inflammatory lesions in rabbits. Methods: Six rabbits with VX2 tumour cells transplanted into one forelimb muscle and inflammatory lesions induced by turpentine oil in the contralateral forelimb were scanned for 60 minutes post ¹⁸F-FDG injection. Imaging data was analyzed with the standard 2-tissue-compartment model. Parameters, VB, Ki, K1, k2, k3, k4, were compared between tumour and inflammatory lesions. SUV and dual time scan methods were also compared in the experiment. Results: Time activity curves of VX2 tumour lesions showed a characteristic pattern of gradually increasing ¹⁸F-FDG uptake up to 60 min, whereas, ¹⁸F-FDG uptake in inflammatory lesions increased more slowly than in tumours. Parameters estimated from the uptake process showed that forward transport constant, K1, and influx constant, Ki, values in VX2 tumour lesions (0.186 ± 0.053 and 0.048 ± 0.014, respectively) was significantly higher than that in inflammatory lesions (0.129 ± 0.024 and 0.022 ± 0.007, respectively) (p < 0.05). In contrast, mean values of VB, k2, k3 and k4 derived from VX2 tumours were not significantly different from that of inflammatory lesions. SUVs at 60 minutes post ¹⁸F-FDG injection were also significantly higher in the VX2 tumor lesions than in the inflammatory lesions. Retention index (RI) was not significantly different between VX2 tumours and inflammatory lesions (1.134 ± 0.076 vs. 1.060 ± 0.058, p > 0.05). Conclusion: Different kinetic parameters (Ki, K1, k3) exist between inflammatory and tumour lesions.

Zusammenfassung

Die unspezifische Anreicherung von ¹⁸F-FDG in Tumoren und auch in entzündlichen Läsionen kann die Diagnostik erschweren. Ziel dieser Arbeit war es, Unterschiede in der Kinetik des ¹⁸F-FDG-Uptake zwischen Tumorund Entzündungszellen zu erforschen. Hierzu wurden VX2-Tumore und entzündliche Läsionen bei Kaninchen untersucht. Tiere, Methoden: Sechs Kaninchen, bei denen VX2-Tumorzellen in einen Muskel eines Vorderlaufes transplantiert und im kontralateralen Vorderlauf mittels Terpentinöl entzündliche Läsionen induziert wurden, wurden über 60 Minuten nach einer ¹⁸F-FDG-Injektion gescannt. Die Bilddaten wurden mittels standardisierten 2-Gewebe-Kompartment- Modells analysiert. Die Para - meter VB, Ki, K1, k2, k3, k4 wurden zwischen Tumor und entzündlicher Läsion verglichen. SUV und zweizeitige Scanmethoden wurden in dem Experiment ebenfalls verglichen. Ergebnisse: Die Zeit/Aktivitätskurven von VX2-Tumoren zeigten ein charakteristisches Muster mit schrittweise zunehmendem ¹⁸F-FDG-Uptake über bis zu 60 min, während der ¹⁸F-FDG-Uptake in entzündlichen Läsionen langsamer zunahm als in Tumoren. Die aus dem Aufnahmeprozess geschätzten Para meter zeigten, dass die Werte der Vorwärts transportkonstante K1 und der Einstromkonstanten Ki in Tumorgewebe (0,186 ± 0,053 bzw. 0,048 ± 0,014) signifikant höher waren als in entzündlichem Gewebe (0,129 ± 0,024 bzw. 0,022 ± 0,007) (p < 0,05). Dagegen unterschieden sich die Mittelwerte für VB, k2, k3 und k4, die aus VX2-Tumoren abgeleitet wurden, nicht signifikant von denen aus entzündlichen Läsionen. 60 Minuten nach ¹⁸F-FDGInjektion waren die SUVs in VX2-Tumoren ebenfalls signifikant höher als in den entzündlichen Läsionen. Der Retentionsindex (RI) war bei VX2-Tumoren und entzündlichen Läsionen nicht signifikant unterschiedlich (1,134 ± 0,076 vs. 1,060 ± 0,058, p > 0,05). Schlussfolgerung: Kinetische Parameter (Ki, K1, k3) zeigen Unterschiede bei entzündlichen Läsionen und Tumoren.

Keywords

¹⁸F-FDG-PET - VX2-carcinoma - inflammation - tumour

Schlüsselwörter

¹⁸F-FDG-PET - VX2-Karzinom - Entzündung - Tumor

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