Automatic registration with continuous pose updates for marker-less surgical navigation in spine surgery

Established surgical navigation systems for pedicle screw placement have been proven to be accurate, but still reveal limitations in registration or surgical guidance. Registration of preoperative data to the intraoperative anatomy remains a time-consuming, error-prone task that includes exposure to harmful radiation. Surgical guidance through conventional displays has well-known drawbacks, as information cannot be presented in-situ and from the surgeon's perspective. Consequently, radiation-free and more automatic registration methods with subsequent surgeon-centric navigation feedback are desirable. In this work, we present a marker-less approach that automatically solves the registration problem for lumbar spinal fusion surgery in a radiation-free manner. A deep neural network was trained to segment the lumbar spine and simultaneously predict its orientation, yielding an initial pose for preoperative models, which then is refined for each vertebra individually and updated in real-time with GPU acceleration while handling surgeon occlusions. An intuitive surgical guidance is provided thanks to the integration into an augmented reality based navigation system. The registration method was verified on a public dataset with a median of 100% successful registrations, a median target registration error of 2.7 mm, a median screw trajectory error of 1.6°and a median screw entry point error of 2.3 mm. Additionally, the whole pipeline was validated in an ex-vivo surgery, yielding a 100% screw accuracy and a median target registration error of 1.0 mm. Our results meet clinical demands and emphasize the potential of RGB-D data for fully automatic registration approaches in combination with augmented reality guidance

Format-Compliant JPEG2000 Encryption in JPSEC: Security, Applicability, and the Impact of Compression Parameters

JPEG2000 encryption has become a widely discussed topic and quite a number of contributions have been made. However, little is known about JPEG2000 compression parameters and their influence on the security and performance of format, compliant encryption schemes. In this work, a thorough analysis of this topic is presented with a focus on format-compliant packet body encryption as sketched in the FCD 15444-8 (JPSEC). A proof for the reversibility of JPSEC format-compliant packet body encryption is given. As format-compliant packet body encryption preserves the JPEG2000 headers, which severely compromises the security, we additionally discuss packet header encryption with a special focus on format compliance and the influence of compression parameters on these schemes. Copyright © 2007 Dominik Engel et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

EVALUATION OF JPEG2000 HASHING FOR EFFICIENT AUTHENTICATION

In this paper we investigate the applicability of different parts of the JPEG2000 codestream for authentication. Apart from the packet body different classes of information contained in the packet header are investigated. We report on experimental results obtained with a large test set of natural images to assess how discriminative and how sensitive each class of information is. Specific attacks against authentication schemes, that use selective hashing of either packet bodies (as proposed in literature) or packet headers, are presented. 1

EURASIP Journal on Information Security / Assessing JPEG2000 encryption with key-dependent wavelet packets

We analyze and discuss encryption schemes for JPEG2000 based on the wavelet packet transform with a key-dependent subband structure. These schemes have been assumed to reduce the runtime complexity of encryption and compression. In addition to this "lightweight" nature, other advantages like encrypted domain signal processing have been reported. We systematically analyze encryption approaches based on key-dependent subband structures in terms of their impact on compression performance, their computational complexity and the level of security they provide as compared to more classical techniques. Furthermore, we analyze the prerequisites and settings in which the previously reported advantages actually hold and in which settings no advantages can be observed. As a final outcome it has to be stated that the compression integrated encryption approach based on the idea of secret wavelet packets can not be recommended.(VLID)218460

Concepts for E-Assessments in STEM on the Example of Engineering Mechanics

We discuss if and how it is possible to develop meaningful e-assessments in Engineering Mechanics. The focus is on complex example problems, resembling traditional paper-pencil exams. Moreover, the switch to e-assessments should be as transparent as possible for the students, i.e., it shouldn’t lead to additional difficulties, while still maintaining sufficiently high discrimination indices for all questions. Example problems have been designed in such a way, that it is possible to account for a great variety of inputs ranging from graphical to numerical and algebraic as well as string input types. Thanks to the implementation of random variables it is even possible to create an individual set of initial values for every participant. Additionally, when dealing with complex example problems errors carried forward have to be taken into account. Different approaches to do so are detailed and discussed, e.g., pre-defined paths for sub-questions, usage of students’ previous inputs or decision trees. The main finding is that complex example problems in Engineering Mechanics can very well be used in e-assessments if the design of these questions is well structured into meaningful sub-questions and errors carried forward are accounted for