Current status and future clinical applications of lymphatic mapping in gastrointestinal cancer

Nanoscale iodized oil emulsion: a useful tracer for pretreatment sentinel node detection using CT lymphography in a normal canine gastric model

BACKGROUND

Pretreatment identification of the sentinel lymph nodes (SLNs) in gastric cancer patients may have great advantages for minimally invasive treatment. No reliable method for the detection of SLNs during the pretreatment period in gastric cancer has been established. The aim of this study was to determine whether computed tomographic (CT) lymphography using nanoscale iodized oil emulsion via endoscopic submucosal injection can visualize LNs.

METHODS

Five dogs underwent CT lymphography after endoscopic submucosal injection of 2 ml of a nanoscale iodized oil emulsion. CT images were taken before and 30, 90, and 210 min after contrast injection. Intraoperative SLN detection was performed using endoscopically injected indocyanine green lymphography for comparison.

RESULTS

Computed tomographic lymphography with nanoscale iodized oil emulsion enabled the visualization of 19 enhanced LNs (mean = 3.8/dog, range = 3-6) with a 100% SLN detection rate. The locations of the SLNs were the lesser curvature (n = 7), greater curvature (n = 1), infrapyloric (n = 3), and left gastric (n = 8) areas. Contrast enhancement of SLNs continuously increased and peaked after 210 min at 142.4 ± 42.3 HU. No green LNs were visualized in the three locations that were detected by CT lymphography. However, no additional LNs were visualized using the dye method. The concordance rate based on the LNs between the SLNs on CT lymphography and the green LNs using the ICG method was 84% (16/19), whereas the concordance rate of the stations identified by CT lymphography and the dye method was 78.6% (11/14).

CONCLUSIONS

Computed tomographic lymphography using nanoscale iodized oil emulsion is a promising tool for preoperative SLN detection for early gastric cancer if the biological safety of the nanoscale iodized oil emulsion can be established.

Real-time imaging of the lymphatic channels and sentinel lymph nodes of the stomach using contrast-enhanced ultrasonography with Sonazoid in a porcine model

The contrast-enhanced ultrasound (CEUS)-guided method in combination with Sonazoid has not been clinically or experimentally evaluated with regard to its use for identifying sentinel lymph node (SLN) in the stomach. Therefore, we attempted to evaluate the usefulness of the CEUS-guided method with Sonazoid for imaging of the lymphatic channels and SLN of the stomach in a porcine model by comparing it with the conventional Evans blue dye-guided method. Twenty-eight 2 to 3-month-old swine weighing 17-30 kg were used in this experiment. Anesthesia was maintained with 2.0-3.0% isoflurane/O(2) inhalation. Sonazoid was injected into the intra- and sub-mucosal layers of the stomach. The intragastric or transcutaneous CEUS-guided method was used to identify the lymphatic channels and SLN of the stomach. Contrast imaging using the CEUS-guided method with Sonazoid enabled us to produce clear images of the afferent lymph vessel and SLN of the stomach until 2 h after the injection of Sonazoid. In addition, intranodal flow of the microbubble agent could be clearly identified using tissue linear harmonic images of the SLN. The SLN detection rate was not significantly different between the CEUS- and dye-guided methods. However, the Evans blue dye flowed out quickly (≈ 15 min after the injection) through the true SLN into the next LN of stomach. In conclusion, the use of the CEUS-guided method with Sonazoid might be the most useful clinical procedure for producing real-time images of the SLN of the stomach, and the linear harmonic images are also useful for evaluating intranodal structure within the SLN.