Microwave Ablation of Symptomatic Benign Thyroid Nodules: Energy Requirement per ml Volume Reduction

Abstract

Purpose: Microwave ablation (MWA) represents a novel thermal ablative treatment of benign thyroid nodules. The aim was to determine the energy required per ml volume reduction in order to match the required energy to the volume-of-interest (VOI).

Materials and Methods: 25 patients with 25 nodules (6 solid, 13 complex and 6 cystic) were treated by microwave ablation (MWA). The transmitted energy (E) was correlated with the volume change (∆ V) after 3 months. The energy required per ml volume reduction after 3 months was calculated by E/∆ V.

Results: MWA resulted in a significant (p < 0.0001) volume reduction (∆ V) with a mean of 12.4 ± 13.0 ml (range: 1.5 – 63.2 ml) and relative reduction of 52 ± 16 % (range: 22 – 77 %). There was a positive correlation between E and ∆ V (r = 0.82; p < 0.05). The mean E/∆ V was 1.52 ± 1.08 (range: 0.4 – 4.6) kJ/ml for all nodules and 2.30 ± 1.5 (0.9 – 4.6), 1.5 ± 0.9 (0.4 – 3.6), 0.75 ± 0.25 (0.4 – 1.2) kJ/ml, respectively, for solid, complex and cystic nodules with a significant difference in E/∆ V for solid and cystic (p < 0.03).

Conclusion: The energy required per volume depends on the nodule consistency. Solid nodules require more energy than cystic ones. The estimation of the energy needed per volume-of-interest as an additional parameter should help to avoid under- or overtreatment.

Key Points:

• The estimated required energy for a volume-of-interest depends on the nodule consistency

• In solid nodules a higher energy transmission than in cystic nodules is recommended

• The energy transmission as an additional marker to ultrasound is helpful for improving periprocedural monitoring

Citation Format:

• Korkusuz Y, Kohlhase K, Gröner D et al. Microwave Ablation of Symptomatic Benign Thyroid Nodules: Energy Requirement per ml Volume Reduction. Fortschr Röntgenstr 2016; 188: 1054 – 1060

Zusammenfassung

Hintergrund: Mikrowellenablationen (MWA) stellen eine neuartige thermoablative Behandlung für benigne Schilddrüsenknoten dar. Ziel war es, die benötigte Energie pro ml Volumenreduktion zu benutzen, um die benötigte Energie für ein volume-of-interest (VOI) abschätzen zu können.

Methode: 25 Patienten mit 25 Knoten (6 solide, 13 komplex und 6 zystisch) wurden durch MWA behandelt. Die übertragene Energie (E) wurde mit der Volumenveränderung (∆ V) nach 3 Monaten korreliert. Der Energiebedarf pro ml Volumenreduktion wurde durch E/∆ V bestimmt.

Ergebnisse: MWA zeigte eine signifikante (p < 0,0001) Volumenreduktion (∆ V) im Mittel von 12,4 ± 13,0 ml (range: 1,5 – 63,2 ml) und eine relative Reduktion von 52 ± 16 % (range: 22 – 77 %). Es zeigte sich eine positive Korrelation zwischen E und ∆ V (r = 0,82; p < 0,05). Die mittlere E/∆ V war 1,52 ± 1,08 (range: 0,4 – 4,6) kJ/ml für alle Knoten und 2,30 ± 1,5 (0,9 – 4,6); 1,5 ± 0,9 (0,4 – 3,6); 0,75 ± 0,25 (0,4 – 1,2) kJ/ml für solide, komplexe und zystische Knoten mit einer signifikanten Differenz der in E/∆ V zwischen soliden und zystischen Knoten (p < 0,03).

Schlussfolgerung: Die benötigte Energie pro Volumen ist abhängig von der Knotenkomposition. Solide Knoten benötigen mehr Energie als zystische. Die abgeschätzte Energie für ein volume-of-interest sollte als zusätzlicher Parameter helfen, eine Über- oder Unterbehandlungen zu vermeiden.

Kernaussagen:

• Die abgeschätzte benötigte Energie für ein Volume-of-interest ist abhängig von der Knotenmorphologie.

• In soliden Knoten ist eine höhere Energie-Transmission empfohlen als bei zystischen Knoten.

• Die Energietransmission als zusätzlicher Parameter neben dem Ultraschall ist nützlich, die periprozedurale Überwachung zu verbessern.

Key words

head/neck - thyroid - ablation procedures - interventional procedures

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