SLN SPECT/CT 3D display with bone co-registration

Abstract

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Objectives: One of the promising clinical uses of integrated SPECT/CT in breast cancer is in the detection of the sentinel lymph node (SLN). We improved the SLN mapping by superimposed the SLN on bone frame extraction from CT information for better localization.

Methods: For SLN mapping, SPECT/CT was performed at 40 minutes after Tc-99m S-solloid peri-tumoral injection. The CT image was acquired with a 2.5mA low dose CT, 10 mm slice thickness (Hawkeye 4, GE Healthcare). After OSEM imaging reconstruction, four steps of imaging processing were applied: (1) applying pre-processing to remove noise and to segment the body contour and bone frame; (2) applying isodata thresholding to suppress the soft tissue portion in every CT axial image; (3) applying direct imaging fusion between SPECT and CT axial images; (4) applying 3D volume rendering processing to enhance anatomical information of the SLNs visual impression. Total 25 SLN SPECT/CT studies were included to test of the program.

Results: The fused slices formed a volume data, which can be displayed as transaxial, sagittal, and coronal views, and a 3D volume rendering image. From the 3D display, SLNs were localized and recorded according to the rib space and the lateral, middle, or medial zones of the each side thoracic cage. All of the 25 SLN SPECT/CT images were successfully processed and localized before surgical operation.

Conclusions: Although the 2.5mA low dose CT with a 10 mm slice thickness provided only barely anatomical information, this processing with adequate CT segmentation and tissue thresholding can provide useful SLN anatomical information for better surgical planning.