There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

CA : A Cancer Journal for Clinicians

Introduction to linear and nonlinear programming

Bilateral teleoperation: An historical survey

Prostate brachytherapy is a form of radiotherapy for treating prostate cancer where the radiation sources are seeds
inserted into the prostate. Accurate localization of seeds during prostate brachytherapy is essential to the success of
intraoperative treatment planning. The current standard modality used in intraoperative seeds localization is transrectal
ultrasound. Transrectal ultrasound, however, suffers in image quality due to several factors such speckle, shadowing, and
off-axis seed orientation. Photoacoustic imaging, based on the photoacoustic phenomenon, is an emerging imaging
modality. The contrast generating mechanism in photoacoustic imaging is optical absorption that is fundamentally
different from conventional B-mode ultrasound which depicts changes in acoustic impedance. A photoacoustic imaging
system is developed using a commercial ultrasound system. To improve imaging contrast and depth penetration,
absorption enhancing coating is applied to the seeds. In comparison to bare seeds, approximately 18.5 dB increase in
signal-to-noise ratio as well as a doubling of imaging depth are achieved. Our results demonstrate that the coating of the
seeds can further improve the discernibility of the seeds.

Improving photoacoustic imaging contrast of brachytherapy seeds

Time domain cross correlation with prior estimates (TDPE) has been recently introduced for high frame rate real-time speckle tracking. TDPE uses prior displacement estimates of neighboring windows to speed up computation. A correlation monitoring technique is then used to verify the estimated displacement and if needed a recovery search is triggered to find the correct displacement. In this paper we extend the idea of TDPE to 2D motion tracking to estimate both the axial and the lateral component of the motion in real-time

P1A-3 Real-Time Estimation of Lateral Displacement Using Time Domain Cross Correlation with Prior Estimates

Delineation of the prostate from transrectal ultrasound images is a necessary step in several computer-assisted clinical interventions, such as low dose rate brachytherapy. Current approaches to user segmentation require user intervention and therefore it is subject to user errors. It is desirable to have a fully automatic segmentation for improved segmentation consistency and speed. In this paper, we propose a multi-atlas fusion framework to automatically segment prostate transrectal ultrasound images. The framework initially registers a dataset of a priori segmented ultrasound images to a target image. Subsequently, it uses the pairwise similarity of registered prostate shapes, which is independent of the image-similarity metric optimized during the registration process, to prune the dataset prior to the fusion and consensus segmentation step. A leave-one-out cross-validation of the proposed framework on a dataset of 50 transrectal ultrasound volumes obtained from patients undergoing brachytherapy treatment shows that the proposed is clinically robust, accurate and reproducible.

/pdf/an-automatic-multi-atlas-segmentation-of-the-prostate-in-42zm7o0oxp.pdf

An automatic multi-atlas segmentation of the prostate in transrectal ultrasound images using pairwise atlas shape similarity.

Biomechanical models of the prostate have a number of potential applications in the diagnosis and management of prostate cancer. Most importantly, it has been shown in several studies that cancerous prostate tissue has different viscoelastic properties than normal prostate tissue: it is typically stiffer (higher storage modulus) and more viscous (higher loss modulus). If a strong correlation can be obtained between malignant tissue and its viscoelastic properties, then all commonly practiced prostate cancer procedures—biopsies, surgery and radiation treatment—can be improved by elasticity imaging. The elastic properties of the prostate and peri-prostatic tissue can also be used in procedure planning, even if such elastic properties do not show strong correlation to cancer. This chapter starts with an introduction to the prostate anatomy, prostate cancer, and a description of the most common procedures and their clinical needs. It continues by presenting the potential impact of elasticity imaging on these procedures. A brief survey of elastography techniques is presented next, with a sampling of some prostate elastography results to date. We describe two of the systems that we developed for the acquisition of prostate ultrasound and magnetic resonance elastography images and summarize our results to date. We show that these elasticity images can be used for prostate segmentation and cross-modality image registration. Furthermore, we show how prostate region deformation models can be used in the development of a prostate brachytherapy simulator which can also be used in the planning of needle insertions that account for deformation.

Biomechanical Modeling of the Prostate for Procedure Guidance and Simulation

This paper presents an approach for providing realistic force feedback to users manipulating serial-chain virtual mechanisms. In the proposed approach, a haptic device controller is designed that penalizes users’ motion along the directions resisted by the virtual joints. The resisted directions span the nullspace the Jacobian of the virtual mechanism computed at the users’ hand, and are derived via a singular value decomposition-based algorithm. Haptic numerical performance is achieved by computing the resisted directions on the graphics processor, and by using them on the haptics processor to derive the control signal that restricts users’ motion as required by the virtual joints. The performance of the proposed approach is validated through experimental manipulations of links with unrestricted and with restricted motion within a planar virtual world.

/pdf/haptic-manipulation-of-serial-chain-virtual-mechanisms-t9a8lqntm2.pdf

Septimiu E. Salcudean

Papers

Improving photoacoustic imaging contrast of brachytherapy seeds

P1A-3 Real-Time Estimation of Lateral Displacement Using Time Domain Cross Correlation with Prior Estimates

An automatic multi-atlas segmentation of the prostate in transrectal ultrasound images using pairwise atlas shape similarity.

Biomechanical Modeling of the Prostate for Procedure Guidance and Simulation

Haptic Manipulation of Serial-Chain Virtual Mechanisms