Ultrasound-CT registration of vertebrae without reconstruction

Abstract

The slices-to-volume ultrasound-CT registration significantly reduces the total registration time per vertebra, making this automated technique more practical intraoperatively.

Registration of MR to Percutaneous Ultrasound of the Spine for Image-Guided Surgery

“…Some groups have used lower frequencies, which enable good imaging of deeper structures such as the transverse processes of the spine [15,9,13,14,6]. However, this makes imaging of superficial structures, such as the spinous processes and the sacrum, challenging.…”

“…We therefore used the latter as input to our segmentation method. In order to extract the bone surfaces from these images, we used a combination of the bone probability maps introduced by Jain et al [7] and Foroughi et al [4], and the backward scan line tracing presented by Yan et al [15]. In ultrasound images, reflections from bone surfaces are seen as bright ridges perpendicular to the ultrasound beam.…”

“…Segmentation of the bone surface from ultrasound images of the spine is still a challenging topic due to noise, artifacts and difficulties in imaging surfaces parallel to the ultrasound beam. A few methods have been described in the literature, ranging from simple ray tracing techniques [15] to more advanced methods based on probability measures [7,4,9] or phase symmetry [13]. Following surface extraction, the segmented bone surfaces are registered using the Iterative Closest Point (ICP) algorithm [2] or the unscented Kalman filter [9].…”

“…In intensity-based registration, a similarity metric based on the image intensities is optimized to find the spatial transformation that best maps one image onto the other [14,8,6,15]. As MR/CT and ultrasound images present very different intensity and noise characteristics, a common approach is to create simulated ultrasound images from the pre-operative data and register the simulated image to the real ultrasound image.…”

Hierarchical CT to Ultrasound Registration of the Lumbar Spine: A Comparison with Other Registration Methods

“…More recently, intensity-based registration techniques have been developed to eliminate the need of segmenting bone surfaces from ultrasound data. 2,28,33,36 These techniques assume that the brightest pixels in ultrasound images are most often caused by the reflection of ultrasound waves on bone surfaces, and hence, extracted bone surfaces from CT images may be registered with an ultrasound dataset by maximizing the average intensity of the overlapping pixels. However, due to speckle noise and other artifacts, intensity of some regions within the overlying soft tissue can be brighter than bone surfaces in B-mode ultrasound, making the in situ application of pure intensity-based CT-ultrasound registration approach 2 problematic.…”