¹²⁴I-PET/CT images of differentiated thyroid cancer patients

Summary

For an adequate therapy planning and staging of patients with differentiated thyroid cancer (DTC), the correct assignment of thyroid remnants (TRs) and lymph node metastases (LMs) is important. Patients, method: We retrospectively analyzed whether kinetic quantities can help improving LM assignment using serial ¹²⁴I-PET/CT data. 127 patients with a total of 317 lesions (TR: n = 265; LM: n = 52) received pre-therapy ¹²⁴I-PET/CT lesion dosimetry using images 24 h and > 96 h after ¹²⁴I administration. For each lesion, maximum activity concentration (MAC) at 24 h and effective half-life (EHL) were determined. Moreover, the product of MAC and EHL was also investigated as a quantity and is referred to CAQ (cumulated activity proportional quantity). In addition, differences between endogenous and exogenous thyroid-stimulating hormone (TSH) stimulation and between papillary (PTC) and follicular thyroid cancer (FTC) were investigated. Results, conclusion: The median MAC, EHL, and CAQ values in TR were significantly higher than in LM but a clinically relevant cut-off value could not be determined because of high overlapping regions. No significant differences for the three quantities were found for the mode of TSH stimulations, but a significant difference for MAC and CAQ between PTC and FTC.

Zusammenfassung

Die genaue Differenzierung von Schilddrüsenrest (TRs) und Lymphknotenmetastasen (LMs) ist für Therapieplanung und Staging bei Patienten mit differenziertem Schilddrüsenkarzinom (DTC) wichtig. Patienten, Methode: Bei 127 Patienten mit insgesamt 317 Läsionen (TR: n = 265; LM: n = 52) wurden quantitative Größen retrospektiv analysiert. Die Patienten wurden einer ¹²⁴I-Dosimetrie unterzogen, die PET/ CT-Aufnahmen nach 24 h und > 96 h be - inhaltete. Für jede Läsion wurden die maximale Aktivitätskonzentration bei der 24-h-Aufnahme (MAC) und die effektive Halbwertzeit (EHL) ermittelt. Als weitere Größe wurde das Produkt aus MAC und EHL, das proportional zur kumulierten Aktivität ist, untersucht. Dieses Produkt wird als CAQ bezeichnet. Zusätzlich wurden die Unterschiede zwischen endogener und exogener Stimulation sowie zwischen papillären (PTC) und follikulären Schilddrüsenkarzinomen (FTC) untersucht. Ergebnisse, Schlussfolgerung: Obwohl die Mediane für MAC, EHL und CAQ für TRs signifikant höher waren als für LMs, konnte kein klinisch relevanter Cut-off- Wert ermittelt werden, da die Überlappungsbereiche zu groß waren. Zwischen endogener und exogener Stimulation konnte kein signifikanter Unterschied in den Größen festgestellt werden, aber für PTC und FTC.

Keywords

Differentiated thyroid carcinoma - iodine-124 - PET - PET/CT - iodine kinetics

Schlüsselwörter

Differenziertes Schilddrüsenkarzinom - Iod-124 - PET - PET/CT - Iodkinetik

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