Nuclear medicine and the surgeon

Multimodal fusion imaging ensemble for targeted sentinel lymph node management: initial results of an innovative promising approach for anatomically difficult lymphatic drainage in different tumour entities

PURPOSE

There are situations where exact identification and localisation of sentinel lymph nodes (SLNs) are very difficult using lymphoscintigraphy, a hand-held gamma probe and vital dye, either a priori or a posteriori. We developed a new method using a simultaneous injection of two lymphotropic agents for exact topographical tomographic localisation and biopsy of draining SLNs. The purpose of this prospective pilot study was to investigate the feasibility and efficacy of this method ensemble.

METHODS

Fourteen patients with different tumour entities were enrolled. A mixture of (99m)Tc-nanocolloid and a dissolved superparamagnetic iron oxide was injected interstitially. Dynamic, sequential static lymphoscintigraphy and SPECT served as pathfinders. MR imaging was performed 2 h after injection. SPECT, contrast MRI and, if necessary, CT scan data sets were fused and evaluated with special regard to the topographical location of SLNs. The day after injection, nine patients underwent SLN biopsy and, in the presence of SLN metastasis, an elective lymph node dissection.

RESULTS

Twenty-five SLNs were localised in the 14 patients examined. A 100% fusion correlation was achieved in all patients. The anatomical sites of SLNs detected during surgery showed 100% agreement with those localised on the multimodal fusion images. SLNs could be excised in 11/14 patients, six of whom had nodal metastasis.

CONCLUSION

Our novel approach of multimodal fusion imaging for targeted SLN management in primary tumours with lymphatic drainage to anatomically difficult regions enables SLN biopsy even in patients with lymphatic drainage to obscure regions. Currently, we are testing its validity in larger patient groups and other tumour entities.

The labelling of Nanocoll® with [111In] for dual-isotope scanning

Visualization and biopsy of sentinel lymph nodes play an important role in planning and controlling the therapy of breast cancer. Hitherto two methods-scintigraphy or gamma probe detection after injection of [99mTc]-nanocolloids and visual detection after injection of patent blue dye-are used routinely. There are no conclusive publications elucidating such important parameters as injection site, injection method and colloidal parameters. The present work aims to label Nanocoll with [111In] to provide an alternative method, a simultanous one-compound dual-isotope application.

METHODS

[111In]-Indiumchloride was buffered with acetate and transferred to the nanocolloid. The colloid labelling reaction was complete after 30 min and filtrated through 100 nm Nuclepore filters.

RESULTS

Incorporation yield of [111In]-Indium into the nanocolloid was nearly quantitative, the step associated with the major loss of activity was the particle sizing with a mean yield of 55%.

CONCLUSION

The presented method allows for the routine supply of [111In]-nanocolloids. Size-filtered [111In]-Nanocoll shows the same particle size range as [99mTc]-Nanocoll.

Sestamibi scintigraphy for the application of minimally invasive surgery of hyperfunctioning parathyroid lesions

Complete surgical resection of hyperfunctioning parathyroid tissue is essential for the curative treatment of hyperparathyroidism. It is very important to identify the accurate location of the affected parathyroid glands by imaging tests to successfully achieve this surgical treatment. Tc-99m labeled sestamibi is a radiopharmaceutical with high affinity for endocrinologically active parathyroid tissue, and scintigraphic evaluation using this radioactive agent is very useful in confirming the location of the affected parathyroid glands. The recent remarkable development of hand-held gamma-ray detectors makes it easy to perform radio-guided surgery, which is a combination of a preoperative intravenous injection of sestamibi and intraoperative navigation by the gamma-rays radiating from the pathological sites. This strategy can be easily applied to the resection of the ectopically located gland and is also useful to confirm the absence of endocrinologically active tissue after the operation. Additional chest SPECT imaging might be effective in the risk assessment of cardiac incidence in the perioperative period, as sestamibi was originally developed for the evaluation of myocardial perfusion. In conclusion, Tc-99m sestamibi will be more popularly applied to the treatment of hyperparathyroidism as minimally invasive surgery increases in favor.

Influence of fast lymphatic drainage on metastatic spread in cutaneous malignant melanoma: a prospective feasibility study

The concept of sentinel lymph node biopsy in cutaneous malignant melanoma is widely established. Preoperative cutaneous lymphoscintigraphic mapping is a reliable method for identifying the nodal basins at risk of metastases in melanomas. In this prospective study we investigated the correlation between the scintigraphic appearance time and the metastatic involvement of sentinel lymph nodes. In 276 malignant melanoma patients (137 women, 139 men; age 16-93 years), dynamic and static lymphoscintigraphy was performed after strict intracutaneous application of technetium-99m nanocolloid (40-150 MBq; 0.05 ml/deposit) around the tumour or biopsy scar. Analysis of dynamic scans primarily focussed on the appearance time of sentinel lymph nodes. Sentinel lymph node visualisation </=20 min post injection was defined as fast drainage, and visualisation >20 min as slow drainage. Fast lymphatic drainage was found in 236 patients, of whom 34 (14.4%) had sentinel lymph node metastases. Twenty-two patients showed hybrid (fast and slow) lymphatic drainage, and eight (36.4%) of them had sentinel lymph node metastases. Seven of the latter demonstrated fast lymphatic drainage, while one showed one positive sentinel lymph node with fast and another with slow drainage. The melanomas of 18 patients demonstrated exclusively slow lymphatic drainage, in all cases without sentinel lymph node metastases. This prospective study indicates that the scintigraphic appearance time of sentinel lymph nodes seems to be a clinically relevant factor for prediction of metastatic spread of cutaneous malignant melanoma. Larger numbers of patients need to be examined to truly assess the benefit of the scintigraphic appearance time compared with other predictors of sentinel lymph node tumour positivity.