CT and SPECT image fusion using external fiducial markers for detection of the sentinel lymph nodes in breast cancer

Abstract

Object: Hybrid single-photon emission computed tomography/computed tomography, which is recently developed, is useful for the sentinel node (SN) mapping in patients with breast cancer. However, this expensive new technology is only available at limited hospitals. The purpose of this study was to assess the feasibility of software-based computed tomography (CT) and single-photon emission tomography (SPECT) image fusion using external fiducial markers for visualization of SNs in breast cancer.

Methods: Preoperative lymphoscintigraphy using 99mTc-phytate colloid was performed in 70 consecutive patients (mean age, 55.3 ± 11.8). Continually, SPECT and low-dose chest CT were performed using an 241Am-containing button as an external fiducial marker attached to the skin surface of the patient’s chest wall. The acquired SPECT and CT images were rescaled, interpolated, reformatted, and registered point-by-point on a workstation.

Results: SPECT detected SN sites, including axillar (n = 96) and internal mammary lesions (n = 7). On fused images, precise overlap of hot spots shown at the corresponding lymph nodes on CT images was achieved in all but 2 cases. In cases with axillar lesions, rendering the fused images into 3D volumes with accentuation of the pectoralis minor muscle was helpful for diagnosis of SN locations in level II (n = 10). After surgery, all nodes were depicted as “hot nodes” on fused images, and 14 metastatic nodes were confirmed by histological examination.

Conclusions: External fiducial-based coregistration of SPECT lymphoscintigraphic and CT images depicted the precise location of SN drainage and may provide useful information for preoperative planning, without the need for hybrid SPECT/CT.