As a prerequisite to performing minimally-invasive spinal surgery (MISS) with technology-guided therapy (TGT), researchers at Vanderbilt University have proposed to mathematically align the physical space of the patient with preoperative images through a surface-based registration. In order to support closed-back spinal surgeries, we have selected a non-invasive, portable imaging modality for obtaining intra-operative images, namely ultrasound (U/S). The preliminary work for the application of TGT to spinal cases has been performed on a spine phantom, scanned with an optically-tracked U/S transducer. The lumbar vertebral surface was extracted from the U/S images, and the surface pixels were converted into 3D physical-space coordinates. This set of U/S surface points was divided into a test set and a target set to be used in registration and error measurement, respectively. The test set of U/S points was registered to segmented CT spinal images of the same phantom spine using a modification of the Besl-McKay Iterative Closest Point algorithm. In a qualitative analysis of the registration, the results look favorable. The U/S points closely align with the corresponding CT surface in every image slice. By incorporating TGT into minimally-invasive spinal surgeries, the procedures are expected to yield reduced injury to normal spinal tissue and hence quicker recovery time for the patient.