124I-PET/CT images of differentiated thyroid cancer patients. Distinguishing lymph node metastases from thyroid remnants using kinetic quantities.
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.


METHODS
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.


CONCLUSIONS
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.
Klinik für Nuklearmedizin, Universitätsklinikum Duisburg-Essen, Hufelandstr. 55, 45122 Essen, Germany.
S
S
Rosenbaum-Krumme
J
J
Nagarajah
M
M
Ruhlmann
A
A
Bockisch
W
W
Jentzen
D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008198:Lymph Nodes / Q000000981:diagnostic imaging*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D018365:Neoplasm, Residual; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000556:secondary*; D014057:Tomography, X-Ray Computed
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals