Table 2.

Merits and drawbacks per technique.

Technique	Advantages	Drawbacks
Conventional lymphoscintigraphy & SPECT-CT	Widely investigated and implemented Allows intraoperative localization of depicted SLNs Differentiation in intensity of radioactive signal Allows (intraoperative) differentiation between SLNs and HENs	Subject to shine-through phenomenon Requires nuclear facilities Low spatial resolution (~5 mm) Poor soft tissue contrast
MR Lymphography (Gd3+)	High spatial resolution (~1 mm) High signal-to-noise ratio and few artifacts Accurate anatomical detail Eliminates shine-through phenomenon Visualization lymphatic vessels May facilitate more targeted radiotherapy No nuclear facilities required Free of radiation exposure	Lacks intraoperative localization of depicted SLNs Rapid lymphatic transportation tracer No retention of tracer in SLNs Gd3+-based contrast agents not registered for lymphography
MR Lymphography (SPIO)	High spatial resolution (~1 mm) Accurate anatomical detail Allows intraoperative localization of depicted SLNs Eliminates shine-through phenomenon May facilitate more targeted radiotherapy No nuclear facilities required Free of radiation exposure	Limited clinical experience in OSCC Retention in SLNs depends on particle size Excess amounts of iron leads to signal voids Negative contrast may confound effectivity SLN detection Local inflammation following administration Metal elements interfere with magnetometer
CT Lymphography	High spatial resolution (~0.5 mm) High temporal resolution Eliminates shine-through phenomenon Visualization lymphatic vessels Visualization of lingual SLNs May facilitate more targeted radiotherapy No nuclear facilities required Widely available and low costs	Lacks intraoperative localization of depicted SLNs Rapid lymphatic transportation tracer No retention of tracer in SLNs Prone to artifacts Poor soft tissue contrast
PET lymphoscintigraphy	High spatial resolution (~2 mm) High temporal resolution Diminishes shine-through phenomenon Visualization lymphatic vessels Visualization of lingual SLNs Differentiation in intensity of radioactive signal Can be performed with known radiotracers Tri-model agent: IRD-800CW-[68Ga]-[99mTc]-tracer Allows intraoperative localization of depicted SLNs	Requires nuclear facilities Poor intraoperative localization of SLNs with PET-probe Poor soft tissue contrast
Contrast-enhanced lymphosonography	Good safety profile of microbubbles High spatial resolution (~0.5 mm) High temporal resolution and real-time imaging Eliminates shine-through phenomenonPossibly no uptake of microbubbles in HENs Can be combined with USgFNA May be extended to other head and neck sites Widely available and low costs Free of radiation exposure	Limited clinical experience in OSCC Suspected low reproducibility High operator dependency Rapid lymphatic transportation tracer Challenging to mark SLNs for biopsy

SPECT-CT; single photon emission computed tomography—computed tomography, SLN; sentinel lymph node, HEN; higher echelon node, MR; magnetic resonance, Gd³⁺; gadolinium, SPIO; superparamagnetic iron oxide, OSCC; oral squamous cell carcinoma, CT; computed tomography, PET; positron emission tomography, IRD; infrared dye, ⁶⁸Ga; gallium-68, ^99mTc; technetium-99m, USgFNA; ultrasound guided fine-needle aspiration.