HEAD AND NECK MELANOMA LYMPH SWELLING SPECT/CT

Head and Neck Melanoma Lymph Swelling SPECT/CT

Head and Neck Melanoma Lymph Swelling SPECT/CT

Introduction

Hybrid imaging techniques allow the direct fusion of morphologic information and functional information. PET/CT has become the fastest growing imaging modality. CT coregistration has led to definite diagnoses by PET and more acceptance of functional imaging. Recently, integrated SPECT/CT scanners have been made available. With SPECT/CT, lesions visualized by functional imaging can be correlated with anatomic structures. The addition of anatomic information increases the sensitivity as well as the specificity of scintigraphic findings (Fig. 1). SPECT/CT has an additional value in sentinel lymph node (SLN) mapping, especially in head and neck tumors and tumors draining into pelvic nodes. In addition to improved anatomic localization of scintigraphic findings, SPECT/CT offers the opportunity to add true diagnostic information derived from CT imaging. Given the growing number of studies demonstrating the added value of hybrid SPECT/CT relative to single imaging modalities, it appears likely that this promising technique will play an increasingly important role in clinical practice. The broad spectrum of existing SPECT tracers and their widespread availability suggest that SPECT/CT can be complementary to PET/CT.

Objective

The additional value of single photon emission computed tomography with CT (SPECT/CT) for detection and localization of sentinel nodes in patients with a melanoma of the head and neck will be determined.

Literature Review

The tumor status of the sentinel node constitutes relevant prognostic information for patients with melanoma, and preliminary information suggests that there is a survival benefit if a node dissection is carried out early on the basis of a positive sentinel node biopsy (Even-Sapir et al, 2003, pp 1413-1420). Patients with melanoma are offered a sentinel node biopsy in many centers, although the therapeutic consequences that should follow the finding of a positive sentinel node are a subject of discussion. Sentinel node biopsy in the head and neck is often more difficult than in other nodal basins, due to the complex anatomy and the variable drainage patterns in this region. Elsewhere in the body, patent blue is used in addition to a radiotracer to visualize the lymphatic channel that leads to the sentinel nodes. In the head and neck, a blue channel is more difficult to find because of the inconsistent drainage pathways. Sentinel nodes in this region are less often stained blue (Khafif et al, 2009, pp 874-879). This makes the use of the radiotracer even more important. The conventional method for preoperative sentinel node detection consists of dynamic and successive static planar lymphoscintigraphy. Dynamic images can visualize the lymph duct from the primary tumor and allows a sentinel node to be distinguished from nodes further downstream. Sequential static images provide an overview of the injection area and the radioactive nodes. Anatomic referencing on these images is limited to orientation in relation to the body contour, which can be visualized using a flood-field source. The site of a sentinel node can be marked on the skin with the aid of an external radioactive marker ...