Abstract. The reconstruction of histology sections into a 3-D volume receives increased attention due to its various applications in modern medical image analysis. To guarantee a geometrically coherent reconstruction, we propose a new way to register histological sections simultaneously to previously acquired reference images and to neighboring slices in the stack. To this end, we formulate two potential functions and associate them to the same Markov random field through which we can efficiently find an optimal solution. Due to our simultaneous formulation and the absence of any segmentation step during the reconstruction we can dramatically reduce error propagation effects. This is illustrated by experiments on carefully created synthetic as well as real data sets.
Electromagnetic (EM) tracking is highly relevant for many computer assisted interventions. This is in particular due to the fact that the scientific community has not yet developed a general solution for tracking of flexible instruments within the human body. Electromagnetic tracking solutions are highly attractive for minimally invasive procedures, since they do not require line of sight. However, a major problem with EM tracking solutions is that they do not provide uniform accuracy throughout the tracking volume and the desired, highest accuracy is often only achieved close to the center of tracking volume. In this paper, we present a solution to the tracking problem, by mounting an EM field generator onto a robot arm. Proposing a new tracking paradigm, we take advantage of the electromagnetic tracking to detect the sensor within a specific sub-volume, with known and optimal accuracy. We then use the more accurate and robust robot positioning for obtaining uniform accuracy throughout the tracking volume. Such an EM servoing methodology guarantees optimal and uniform accuracy, by allowing us to always keep the tracked sensor close to the center of the tracking volume. In this paper, both dynamic accuracy and accuracy distribution within the tracking volume are evaluated using optical tracking as ground truth. In repeated evaluations, the proposed method was able to reduce the overall error from 6.64±7.86 mm to a significantly improved accuracy of 3.83±6.43 mm. In addition, the combined system provides a larger tracking volume, which is only limited by the reach of the robot and not the much smaller tracking volume defined by the magnetic field generator.
Until now, core needle biopsy of the axillary sentinel lymph nodes in early stage breast cancer patients is not possible, due to the lack of a proper combination of functional and anatomical information. In this work we present the first fully 3D freehand SPECT -ultrasound fusion, combining the advantages of both modalities. By using spatial positioning either with optical or with electromagnetic tracking for the ultrasound probe, and a mini gamma camera as radiation detector for freehand SPECT reconstructions, we investigate the capability of the introduced multi-model imaging system, where we compare both 3D freehand SPECT and 3D ultrasound to ground truth for a realistic breast mimicking phantom and further analyze the effect of tissue deformation by ultrasound. Finally, we also show its application in a real clinical setting.
To cite this article: N Aubry et al 2013 JINST 8 C04002 View the article online for updates and enhancements.
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