Ex vivo and in vivo evaluation of laser-induced thermotherapy for nodular thyroid disease.
OBJECTIVE
The prevalence of thyroid nodules ranges between 2% and 60% depending on the population studied. However, minimally invasive procedures like laser-induced thermotherapy (LITT) are increasingly used to treat tumors of parenchymatous organs and seem to be suitable for singular thyroid nodules as well. Their successful clinical application depends on the induction of sufficiently large lesions and a knowledge of the energy parameters required for complete thermal ablation. The aim of this study was to establish a dose-response relationship for LITT of thyroid nodules.


METHODS
Thermal lesions were induced in healthy porcine thyroid glands ex vivo (n = 110) and in vivo (n = 10) using an Nd:YAG laser (1,064 nm). Laser energy was applied for 300 seconds in a power range of 10-20 W. During the ablation, continuous temperature measurement at a distance of 5 and 10 mm from the applicator was performed. The lesions were longitudinally and transversally measured, and the volume was calculated. Furthermore, enzyme histochemical analysis of the thyroid tissue was performed.


RESULTS
The maximum inducible lesion volumes were between 0.74 +/- 0.18 cm(3) at a laser power of 10 W and 3.80 +/- 0.41 cm(3) at 20 W. The maximum temperatures after ablation were between 72.9 +/- 2.9 degrees C (10 W) and 112.9 +/- 9.2 degrees C (20 W) at a distance of 5 mm and between 49.5 +/- 2.2 degrees C (10 W) and 73.2 +/- 6.7 degrees C (20 W) at a distance of 10 mm from the applicator. The histochemical analysis demonstrates a complete loss of NADPH dehydrogenase activity in thermal lesions as a sign of irreversible cell damage.


CONCLUSIONS
This study is the first to demonstrate a dose-response relationship for LITT of thyroid tissue. LITT is suitable for singular thyroid nodules and induces reproducible clinically relevant lesions with irreversible cell damage in an appropriate application time.
Ritz
Jörg-P
JP
Department of General, Vascular, and Thoracic Surgery, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, 12200 Berlin, Germany.
Lehmann
Kai S
KS
Zurbuchen
Urte
U
Knappe
Verena
V
Schumann
Thomas
T
Buhr
Heinz J
HJ
Holmer
Christoph
C
D000818:Animals; D004195:Disease Models, Animal; D006979:Hyperthermia, Induced / Q000379:methods; D007150:Immunohistochemistry; D053685:Laser Therapy / Q000379:methods*; D019060:Minimally Invasive Surgical Procedures / Q000379:methods; D011336:Probability; D011897:Random Allocation; D012307:Risk Factors; D013552:Swine; D013959:Thyroid Diseases / Q000473:pathology / Q000601:surgery; D016606:Thyroid Nodule / Q000473:pathology* / Q000601:surgery*