The Hybrid SPECT/CT as an additional lymphatic mapping tool in patients with breast cancer

Conventional lymphoscintigraphy does not always define the exact anatomic location of a sentinel node. The lymphatic drainage pattern may be unusual or may not be shown at all. The recently introduced hybrid SPECT/CT imaging could help overcome these difficulties. SPECT is a tomographic version of conventional lymphoscintigraphy and the images have better contrast and resolution. When fused with the anatomical details provided by CT into one image, a meaningful surgical "roadmap" can be created. So far, there is little literature on the use of hybrid SPECT/CT in lymphatic mapping in patients with breast cancer. The purpose of this review was to report on these publications, including our own experience, focusing on patient selection, SPECT/CT settings, anatomic localization, and the detection of additional sentinel nodes.

The majority of investigators did not formulate indications for additional SPECT/CT after conventional imaging but scanned all patients eligible for sentinel node biopsy. The SPECT/CT settings used in the studies of this review were mostly similar, but the methods used for conventional imaging were more variable.

All studies demonstrated an improved anatomical localization by performing additional SPECT/CT; sentinel nodes outside the axilla or nodes close to the injection site were especially easier to identify. Sentinel nodes were visualized in 89-100% by combined conventional imaging and SPECT/CT, with sentinel nodes depicted only by SPECT/CT in up to 14%.

It is concluded that SPECT/CT shows the exact anatomical location of sentinel nodes, detects sentinel nodes not depicted by conventional imaging, and therefore facilitates surgical exploration. The hybrid SPECT/CT has the potential to make image fusion a routine clinical tool that improves lymphatic mapping in patients with breast cancer.