Fast and Robust Registration Based on Gradient Orientations: Case Study Matching Intra-operative Ultrasound to Pre-operative MRI in Neurosurgery. In: Abolmaesumi P, Joskowicz L, Navab N, Jannin P, editors. Information Processing in Computer-Assisted Interventions. Berlin: Springer Berlin Heidelberg; 2012. pp. 125-34. [DOI: 10.1007/978-3-642-30618-1_13]

New US device versus imaging US to assess tumor-in-brain

Background

Applying ultrasonic imaging system during surgery requires the poring of saline, performing the measurement, and acquiring data from its display—which requires time and is highly “performer dependent,” i.e., the measure is of a subjective nature. A new ultrasonic device was recently developed that overcomes most of these drawbacks and was successfully applied during tumor-in-brain neurosurgeries. The purpose of this study was to compare the two types of US devices and demonstrate their properties.

Methods

The study was performed in the following stages: (i) an ex vivo experiment, where slices of the muscle and brain of a young porcine were laid one on top the other. Thicknesses and border depths were measured and compared, using the two types of US instruments. (ii) During human clinical neurosurgeries, tumor depth was compared by measuring it with both devices. (iii) Following the success of stages (i) and (ii), using solely the new US device, the tumor thickness was monitored while its resection.

Correlation, Pearson’s coefficient, average, mean, and standard deviation were applied for statistical tests.

Results

A high correlation was obtained for the distances of tissue borders and for their respective thicknesses. Applying these ultrasonic devices during neurosurgeries, tumor depths were monitored with high similarity (87%), which was also obtained by Pearson’s correlation coefficient (0.44). The new US device, thanks to its small footprint, its remote measurement, and the capability of monitoring intraoperatively and in real-time, provides the approach to tumor’s border before its complete resection.

Conclusions

The new US device provides better accuracy than an ultrasonic imaging system; its data is objective; it enables to control the residual tumor thickness during its resection, and it is especially useful in restricted areas. These features were found of great help during a tumor-in-brain surgery and especially in the final stages of tumor’s resection.

miLBP: a robust and fast modality-independent 3D LBP for multimodal deformable registration

Purpose

Computer-assisted intervention often depends on multimodal deformable registration to provide complementary information. However, multimodal deformable registration remains a challenging task.

Methods

This paper introduces a novel robust and fast modality-independent 3D binary descriptor, called miLBP, which integrates the principle of local self-similarity with a form of local binary pattern and can robustly extract the similar geometry features from 3D volumes across different modalities. miLBP is a bit string that can be computed by simply thresholding the voxel distance. Furthermore, the descriptor similarity can be evaluated efficiently using the Hamming distance.

Results

miLBP was compared to vector-valued self-similarity context (SSC) in artificial image and clinical settings. The results show that miLBP is more robust than SSC in extracting local geometry features across modalities and achieved higher registration accuracy in different registration scenarios. Furthermore, in the most challenging registration between preoperative magnetic resonance imaging and intra-operative ultrasound images, our approach significantly outperforms the state-of-the-art methods in terms of both accuracy (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2.15\pm 1.1 \hbox { mm}$$\end{document}2.15±1.1mm) and speed (29.2 s for one case).

Conclusions

Registration performance and speed indicate that miLBP has the potential of being applied to the time-sensitive intra-operative computer-assisted intervention.

The use of ultrasound in intracranial tumor surgery

BACKGROUND

As an intraoperative imaging modality, ultrasound is a user-friendly and cost-effective real-time imaging technique. Despite this, it is still not routinely employed for brain tumor surgery. This may be due to the poor image quality in inexperienced hands, and the well-documented learning curve. However, with regular use, the operator issues are addressed, and intraoperative ultrasound can provide valuable real-time information. The aim of this review is to provide an understanding for neurosurgeons of the development and use of ultrasound in intracranial tumor surgery, and possible future advances.

METHODS

A systematic search of the electronic databases Embase, Medline OvidSP, PubMed, Cochrane, and Google Scholar regarding the use of ultrasound in intracranial tumor surgery was undertaken.

RESULTS AND DISCUSSION

Intraoperative ultrasound has been shown to be able to accurately account for brain shift and has potential for regular use in brain tumor surgery. Further developments in probe size, resolution, and image reconstruction techniques will ensure that intraoperative ultrasound is more accessible and attractive to the neuro-oncological surgeon.

CONCLUSIONS

This review has summarized the development of ultrasound and its uses with particular reference to brain tumor surgery, detailing the ongoing challenges in this area.

Intra-operative correction of brain-shift

BACKGROUND

Brain-shift is a major source of error in neuronavigation systems based on pre-operative images. In this paper, we present intra-operative correction of brain-shift using 3D ultrasound.

METHODS

The method is based on image registration of vessels extracted from pre-operative MRA and intra-operative power Doppler-based ultrasound and is fully integrated in the neuronavigation software.

RESULTS

We have performed correction of brain-shift in the operating room during surgery and provided the surgeon with updated information. Here, we present data from seven clinical cases with qualitative and quantitative error measures.

CONCLUSION

The registration algorithm is fast enough to provide the surgeon with updated information within minutes and accounts for large portions of the experienced shift. Correction of brain-shift can make pre-operative data like fMRI and DTI reliable for a longer period of time and increase the usefulness of the MR data as a supplement to intra-operative 3D ultrasound in terms of overview and interpretation.

Global registration of ultrasound to MRI using the LC2 metric for enabling neurosurgical guidance

Automatic and robust registration of pre-operative magnetic resonance imaging (MRI) and intra-operative ultrasound (US) is essential to neurosurgery. We reformulate and extend an approach which uses a Linear Correlation of Linear Combination (LC2)-based similarity metric, yielding a novel algorithm which allows for fully automatic US-MRI registration in the matter of seconds. It is invariant with respect to the unknown and locally varying relationship between US image intensities and both MRI intensity and its gradient. The overall method based on this both recovers global rigid alignment, as well as the parameters of a free-form-deformation (FFD) model. The algorithm is evaluated on 14 clinical neurosurgical cases with tumors, with an average landmark-based error of 2.52 mm for the rigid transformation. In addition, we systematically study the accuracy, precision, and capture range of the algorithm, as well as its sensitivity to different choices of parameters.