Theodoros N. Arvanitis

Identification and characterisation of childhood cerebellar tumours by in vivo proton MRS.

1H MRS has great potential for the clinical investigation of childhood brain tumours, but the low incidence in, and difficulties of performing trials on, children have hampered progress in this area. Most studies have used a long‐TE, thus limiting the metabolite information obtained, and multivariate analysis has been largely unexplored. Thirty‐five children with untreated cerebellar tumours (18 medulloblastomas, 12 pilocytic astrocytomas and five ependymomas) were investigated using a single‐voxel short‐TE PRESS sequence on a 1.5 T scanner. Spectra were analysed using LCModelTM to yield metabolite profiles, and key metabolite assignments were verified by comparison with high‐resolution magic‐angle‐spinning NMR of representative tumour biopsy samples. In addition to univariate metabolite comparisons, the use of multivariate classifiers was investigated. Principal component analysis was used for dimension reduction, and linear discriminant analysis was used for variable selection and classification. A bootstrap cross‐validation method suitable for estimating the true performance of classifiers in small datasets was used. The discriminant function coefficients were stable and showed that medulloblastomas were characterised by high taurine, phosphocholine and glutamate and low glutamine, astrocytomas were distinguished by low creatine and high N‐acetylaspartate, and ependymomas were differentiated by high myo‐inositol and glycerophosphocholine. The same metabolite features were seen in NMR spectra of ex vivo samples. Successful classification was achieved for glial‐cell (astrocytoma + ependymoma) versus non‐glial‐cell (medulloblastoma) tumours, with a bootstrap 0.632 + error, eB.632+, of 5.3%. For astrocytoma vs medulloblastoma and astrocytoma vs medulloblastoma vs ependymoma classification, the eB.632+ was 6.9% and 7.1%, respectively. The study showed that 1H MRS detects key differences in the metabolite profiles for the main types of childhood cerebellar tumours and that discriminant analysis of metabolite profiles is a promising tool for classification. The findings warrant confirmation by larger multi‐centre studies. Copyright

An algorithm for the automated quantitation of metabolites in in vitro NMR signals.

The quantitation of metabolite concentrations from in vitro NMR spectra is hampered by the sensitivity of peak positions to experimental conditions. The quantitation methods currently available are generally labor intensive and cannot readily be automated. Here, an algorithm is presented for the automatic time domain analysis of high‐resolution NMR spectra. The TARQUIN algorithm uses a set of basis functions obtained by quantum mechanical simulation using predetermined parameters. Each basis function is optimized by subdividing it into a set of signals from magnetically equivalent spins and varying the simulated chemical shifts of each of these groups to match the signal undergoing analysis. A novel approach to the standard multidimensional minimization problem is introduced based on evaluating the fit resulting from different permutations of possible chemical shifts, obtained from one‐dimensional searches. Results are presented from the analysis of 1H proton magic angle spinning spectra of cell lines illustrating the robustness of the method in a typical application. Simulation was used to investigate the biggest peak shifts that can be tolerated. Magn Reson Med, 2006.

Uses of accelerometer data collected from a wearable system

This paper presents work, assessing the use of accelerometers in wearable systems for a number of applications. It discusses and demonstrates how body mounted accelerometers can be used in context aware computing systems and for measuring aspects of human performance, which may be used for teaching and demonstrating skill acquisition, coaching sporting activities, sports and human movement research, and teaching subjects such as physics and physical education. Analysis is restricted to considerations as to how raw data can be used, and how simple calculations of quantities of data in the time domain, can be used. The limitations of the use of such data are discussed.

Objective surgical performance evaluation based on haptic feedback.

In order to develop effective virtual reality training systems for surgery there is a need to provide appropriate sensory and performance feedback to the user. This paper aims to demonstrate a method by which performance data can be collected. This is used to investigate the effect of haptic feedback on performance. A PHANTOM desktop device was used in conjunction with a suturing simulation A pair of needle-holders was instrumented with strain gauges and attached to the stylus of the PHANTOM allowing the measurement of force application and time. Suturing performance was evaluated in terms of stitch completion time, peak force application, and the length and straightness of the stitch. The effect of the level of force feedback provided by the simulation and performance over time was considered. The results indicate that the presence of force feedback affected task completion time, peak force application and the straightness of the stitch. Task completion time was shown to increase with the level of force feedback provided. Performance was seen to improve over time in terms of task completion time and the accuracy ofthe stitch. The work has examined how the presence and level of force feedback affects performance of a simple task. The accuracy of haptic feedback is important in the design of surgical simulation systems to ensure effective training transfer. A data collection method by which objective performance evaluation can be made is demonstrated. The method can be applied to training using bench models, simulations and potentially in the operating theatre.

Assessing the Wearability of Wearable Computers

In terms of mounting a computer on the body, the computers weight, size, shape, placement and method of attachment can elicit a number of effects. Inappropriate design may mean that the wearer is unable to perform specific tasks or achieve goals. Excessive stress on the body may result in perceptions of discomfort, which may in turn affect task performance, but ultimately raises issues of health and safety. This paper proposes a methodology for assessing the affects of wearing a computer in terms of physiological energy expenditure, the biomechanical effects due to changes in movement patterns, posture and perceptions of localised pain and discomfort due to musculoskeletal loading, and perceptions of well- being through comfort assessment. From ratings of these effects the paper proposes 5 levels to determine the wearability of a computer.

Objective metrics for the evaluation of simple surgical skills in real and virtual domains

Surgical skills are traditionally assessed through subjective evaluation with experienced surgeons observing and rating trainee activity. However, this process can be expensive, particularly in terms of the time required of expert surgeons. Subjective assessment may also suffer from problems of intersubject variation in the application of evaluation criteria. Computer-based training, in particular systems combining virtual reality interfaces with haptic displays, offers a means of providing both automated and objective assessment of performance. In this paper we propose that, prior to the development of such systems, there is a need to determine measures that can adequately differentiate levels of performance. The paper therefore discusses the evaluation of surgical technique using objective metrics. Two main questions are addressed. How can surgical technique be assessed? What metrics prove useful in defining and modifying surgical skills and techniques?

An intranet database for pacemaker patients.

A database system, incorporating smartcard technologies, was designed to hold the personal and pacing details of pacemaker patients, who attended a clinic at the Royal Sussex County Hospital (RSCH), Brighton, UK. Following an initial period of a 12 month clinical trial, with the database running on a standalone personal computer, the Pacemaker Patient Database has been redesigned and implemented as an intranet-based system. This paper describes the issues relating to the development of the new prototype system and identifies the design principles for intranet-based electronic health care (EHCR) record database systems.

Reject analysis: a pilot programme for image quality management

The radiographic film wastage and the different parameters affecting this wastage were analysed for a 9-week period at a 600-bed University Hospital. An overall reject rate of 7.6% was found. The different reasons for rejection were evaluated, while retake rate, relation between working experience of the personnel, amount of rejected films and total film wastage in surface (m2), were registered and analysed.

A comparative study of feature extraction and blind source separation of independent component analysis (ICA) on childhood brain tumour 1H magnetic resonance spectra

Independent component analysis (ICA) has the potential of determining automatically the metabolite signals which make up MR spectra. However, the realiability with which this is accomplished and the optimal approach for investigating in vivo MRS have not been determined. Furthermore, the properties of ICA in brain tumour MRS with respect to dataset size and data quality have not been systematically explored. The two common techniques for applying ICA, blind source separation (BSS) and feature extraction (FE) were examined in this study using simulated data and the findings confirmed on patient data. Short echo time (TE 30 ms), low and high field (1.5 and 3 T) in vivo brain tumour MR spectra of childhood astrocytoma, ependymoma and medulloblastoma were generated by using a quantum mechanical simulator with ten metabolite and lipid components. Patient data (TE 30 ms, 1.5 T) were acquired from children with brain tumours. ICA of simulated data shows that individual metabolite components can be extracted from a set of MRS data. The BSS method generates independent components with a closer correlation to the original metabolite and lipid components than the FE method when the number of spectra in the dataset is small. The experiments also show that stable results are achieved with 300 MRS at an SNR equal to 10. The FE method is relatively insensitive to different ranges of full width at half maximum (FWHM) (from 0 to 3 Hz), whereas the BSS method degrades on increasing the range of FWHM. The peak frequency variations do not affect the results within the range of ±0.08 ppm for the FE method, and ±0.05 ppm for the BSS method. When the methods were applied to the patient dataset, results consistent with the synthesized experiments were obtained. Copyright

WWW creates new interactive 3D graphics and colIaborative environments for medical research and education

Virtual Reality Modelling Language (VRML) is the start of a new era for medicine and the World Wide Web (WWW). Scientists can use VRML across the Internet to explore new three-dimensional (3D) worlds, share concepts and collaborate together in a virtual environment. VRML enables the generation of virtual environments through the use of geometric, spatial and colour data structures to represent 3D objects and scenes. In medicine, researchers often want to interact with scientific data, which in several instances may also be dynamic (e.g. MRI data). This data is often very large and is difficult to visualise. A 3D graphical representation can make the information contained in such large data sets more understandable and easier to interpret. Fast networks and satellites can reliably transfer large data sets from computer to computer. This has led to the adoption of remote tale-working in many applications including medical applications. Radiology experts, for example, can view and inspect in near real-time a 3D data set acquired from a patient who is in another part of the world. Such technology is destined to improve the quality of life for many people. This paper introduces VRML (including some technical details) and discusses the advantages of VRML in application developing.