Surgical navigation for guidewire placement from intraoperative fluoroscopy in orthopaedic surgery.

Objective. Surgical guidewires are commonly used in placing fixation implants to stabilize fractures. Accurate positioning of these instruments is challenged by difficulties in 3D reckoning from 2D fluoroscopy. This work aims to enhance the accuracy and reduce exposure times by providing 3D navigation for guidewire placement from as little as two fluoroscopic images.Approach. Our approach combines machine learning-based segmentation with the geometric model of the imager to determine the 3D poses of guidewires. Instrument tips are encoded as individual keypoints, and the segmentation masks are processed to estimate the trajectory. Correspondence between detections in multiple views is established using the pre-calibrated system geometry, and the corresponding features are backprojected to obtain the 3D pose. Guidewire 3D directions were computed using both an analytical and an optimization-based method. The complete approach was evaluated in cadaveric specimens with respect to potential confounding effects from the imaging geometry and radiographic scene clutter due to other instruments.Main results. The detection network identified the guidewire tips within 2.2 mm and guidewire directions within 1.1°, in 2D detector coordinates. Feature correspondence rejected false detections, particularly in images with other instruments, to achieve 83% precision and 90% recall. Estimating the 3D direction via numerical optimization showed added robustness to guidewires aligned with the gantry rotation plane. Guidewire tips and directions were localized in 3D world coordinates with a median accuracy of 1.8 mm and 2.7°, respectively.Significance. The paper reports a new method for automatic 2D detection and 3D localization of guidewires from pairs of fluoroscopic images. Localized guidewires can be virtually overlaid on the patient's pre-operative 3D scan during the intervention. Accurate pose determination for multiple guidewires from two images offers to reduce radiation dose by minimizing the need for repeated imaging and provides quantitative feedback prior to implant placement.

C-arm orbits for metal artifact avoidance (MAA) in cone-beam CT.

Metal artifacts present a challenge to cone-beam CT (CBCT) image-guided surgery, obscuring visualization of metal instruments and adjacent anatomy-often in the very region of interest pertinent to the imaging/surgical tasks. We present a method to reduce the influence of metal artifacts by prospectively defining an image acquisition protocol-viz., the C-arm source-detector orbit-that mitigates metal-induced biases in the projection data. The metal artifact avoidance (MAA) method is compatible with simple mobile C-arms, does not require exact prior information on the patient or metal implants, and is consistent with 3D filtered backprojection (FBP), more advanced (e.g. polyenergetic) model-based image reconstruction (MBIR), and metal artifact reduction (MAR) post-processing methods. The MAA method consists of: (i) coarse localization of metal objects in the field-of-view (FOV) via two or more low-dose scout projection views and segmentation (e.g. a simple U-Net) in coarse backprojection; (ii) model-based prediction of metal-induced x-ray spectral shift for all source-detector vertices accessible by the imaging system (e.g. gantry rotation and tilt angles); and (iii) identification of a circular or non-circular orbit that reduces the variation in spectral shift. The method was developed, tested, and evaluated in a series of studies presenting increasing levels of complexity and realism, including digital simulations, phantom experiment, and cadaver experiment in the context of image-guided spine surgery (pedicle screw implants). The MAA method accurately predicted tilted circular and non-circular orbits that reduced the magnitude of metal artifacts in CBCT reconstructions. Realistic distributions of metal instrumentation were successfully localized (0.71 median Dice coefficient) from 2-6 low-dose scout views even in complex anatomical scenes. The MAA-predicted tilted circular orbits reduced root-mean-square error (RMSE) in 3D image reconstructions by 46%-70% and 'blooming' artifacts (apparent width of the screw shaft) by 20-45%. Non-circular orbits defined by MAA achieved a further ∼46% reduction in RMSE compared to the best (tilted) circular orbit. The MAA method presents a practical means to predict C-arm orbits that minimize spectral bias from metal instrumentation. Resulting orbits-either simple tilted circular orbits or more complex non-circular orbits that can be executed with a motorized multi-axis C-arm-exhibited substantial reduction of metal artifacts in raw CBCT reconstructions by virtue of higher fidelity projection data, which are in turn compatible with subsequent MAR post-processing and/or polyenergetic MBIR to further reduce artifacts.

Combining Hopfield neural networks, with applications to grid-based mathematics puzzles.

Hopfield neural networks are useful for solving certain constrained set-selection problems. We establish that the vector fields associated with general networks of this type can be combined to produce a new network that solves the corresponding combination of set-selection/constraint problems, provided a relatively simple condition is satisfied. That is, we establish that just this one condition needs to be verified in order to be able to combine such networks. We introduce some generalizations of networks that exist in the literature, and, to demonstrate the usefulness of the work, we combine these networks to solve two well-known grid-based math puzzles (i.e. constraint problems): Kakuro and Akari (called Cross Sums and Light Up in North America). We present examples to illustrate the evolution of the solution process. We find that the difficulty rating of a Kakuro puzzle is strongly connected to the number of iterations used by the neural network solver.

Set selection dynamical system neural networks with partial memories, with applications to Sudoku and KenKen puzzles.

After reviewing set selection and memory model dynamical system neural networks, we introduce a neural network model that combines set selection with partial memories (stored memories on subsets of states in the network). We establish that feasible equilibria with all states equal to ± 1 correspond to answers to a particular set theoretic problem. We show that KenKen puzzles can be formulated as a particular case of this set theoretic problem and use the neural network model to solve them; in addition, we use a similar approach to solve Sudoku. We illustrate the approach in examples. As a heuristic experiment, we use online or print resources to identify the difficulty of the puzzles and compare these difficulties to the number of iterations used by the appropriate neural network solver, finding a strong relationship.

Solving inverse problems for biological models using the collage method for differential equations.

In the first part of this paper we show how inverse problems for differential equations can be solved using the so-called collage method. Inverse problems can be solved by minimizing the collage distance in an appropriate metric space. We then provide several numerical examples in mathematical biology. We consider applications of this approach to the following areas: population dynamics, mRNA and protein concentration, bacteria and amoeba cells interaction, tumor growth.

[Compulsory treatment under legal uncertainty: part 1: the current legal situation on compulsory treatment of patients with psychiatric disorders incapable of consenting]. / Zwangsbehandlungen unter Rechtsunsicherheit : Teil 1: Die aktuelle Rechtslage zu Zwangsbehandlungen einwilligungsunfähiger Patienten mit psychischen Erkrankungen.

A series of recent court decisions have been concerned with the compulsory treatment of patients with mental disorders who are incapable of giving consent. This article describes the current legal situation on compulsory treatment for different cases to achieve the aim of internment, endangerment to third parties, self-endangerment, for intercurrent diseases and to achieve the aim of therapy. The verdicts contribute on the one hand to strengthen patient autonomy against governmental or medical paternalism. On the other hand the verdicts have effected a substantial legal uncertainty with the undesired indirect consequence that fixation will probably be used more often.

[Compulsory treatment under legal uncertainty: part 2: consequences of legal uncertainty in clinical practice - suggestions for improvement]. / Zwangsbehandlungen unter Rechtsunsicherheit : Teil 2: Folgen der Rechtsunsicherheit in der klinischen Praxis - Vorschläge zur Verbesserung.

The current legal uncertainty on compulsory treatment of mentally ill patient incapable of giving consent favors the practice of defensive treatment, such as the increased use of isolation and fixation instead of medication. Such a stance runs the risk of acute or chronic health damage for patients. The dissent between legal practitioners and psychiatrists on compulsory treatment is obviously based on a different understanding of autonomy and its prerequisites. We advocate an individual centered, preferably open form of treatment by medicinal and milieu therapeutic approaches in association with intensified relationships with the aim to restore or improve the ability for self-determination. We also call upon the legislative authorities to establish legal certainty. It is decisive that the characteristics of mental diseases and the possibilities of modern treatment are taken into consideration in order to suitably respect patient autonomy without neglecting the necessary help.

[Pay for performance in rehabilitation after stroke - results of a pilot project 2001-2008]. / Ergebnisorientierte Vergütung der Rehabilitation nach Schlaganfall - Entwicklungsschritte eines Modellprojekts 2001-2008.

The project aimed at developing and testing a new payment system which provides financial incentives for rehabilitation centers to achieve the best outcomes possible for their patients but does not create additional costs for the insurance funds. The system is conceived as a "quality competition" organized by the centers among themselves with a scientific institute acting as a "referee". Centers with outcomes above average receive a bonus financed by a corresponding malus from the centers below average. In a stepwise process which started in 2001 and was continually accompanied by a scientific institute, we developed the methodological and organizational prerequisites for the new payment system and tested them in two multicentric studies with large case numbers (n=1,058 and n=700, respectively). As a first step, a new assessment instrument (SINGER) was developed and validated in order to measure the outcomes in a reliable, valid, and change-sensitive way. In the second phase, we developed a regression analytic model which predicted the central outcome variable with >84% variance explained. With this model, the different case-mix in the participating centers can be controlled, so that comparisons of outcomes across centers can take place under fair conditions. In the recently completed third phase, we introduced an internet-based programme SINGER-online into which the centers can enter all relevant data. This programme ensures a high quality of all data and makes comparisons of outcomes across all centers possible at any chosen time. The programme contains a special module accessible to the medical services of the health insurance only, which allows sample checks of the data entered by the clinics and helps to ensure that all centers keep to the principles of a fair competition for better quality for their patients. After successful testing of these elements, a functioning model of pay-for-performance in rehabilitation after stroke is now available.

Forty-eight new cases with infertility due to balanced chromosomal rearrangements: detailed molecular cytogenetic analysis of the 90 involved breakpoints.

A molecular cytogenetic study was performed on 48 infertile patients who were identified as carriers of balanced translocations (40 cases), inversions (6 cases) or insertions (2 cases) by means of banding cytogenetics. Cases with a Robertsonian translocation or pericentric inversion 2 or 9 were not included. In summary, 100 break-events occurred in these patients, and 90 different chromosomal regions were involved. Thus, this study confirmed the presence of abnormal karyotypes in a subgroup of patients seeking infertility treatment. Breaks were demonstrated to appear preferentially in GTG-light bands in these patients. Furthermore, the observed breakpoints were associated with genomic regions prone to instability due to the presence of segmental duplications. Nonetheless, further detailed molecular analysis will be necessary in the future to characterize the mechanisms and genetic basis for this phenomenon.

Rayleigh scattering and redistribution of radiation in He I plasmas: measurements and calculations.

Conditions for which Rayleigh scattering and redistribution of radiation can be observed are examined. The competition between the relaxation processes and spontaneous emission is shown to determine the conditions for partial redistribution. We investigate specific cases in the singlet and triplet He I atomic system for plasma parameters reachable experimentally in a well diagnosed magnetic multipole source. Partial redistribution on the 2 1S-4 1P at 396.5 nm, 2 1P-5 1D at 438.8 nm, 2 3P-5 3D at 402.6 nm, 2 3P-4 3D at 447.2 nm and 2 3P-4 3S at 471.3 nm fine structure transitions is observed employing a dye laser pumping the He I plasma. We make use of a previously developed two-photon formalism based on the frequency fluctuation model to calculate radiative redistribution functions. Results of the partial redistribution measurements are presented, augmented by a comparison with calculations. This allows us to confirm available electron-atom elastic collision rates to within 20%.

Electrical conductivity of nonideal carbon and zinc plasmas: experimental and theoretical results.

Electrical conductivities of nonideal carbon and zinc plasmas have been measured in this paper. The plasma is produced by vaporizing a wire placed in a glass capillary within some hundred nanoseconds. In the case of carbon, vaporization occurs with good reproducibility when utilizing a preheating system. The particle density is in the range of n=(1-10) x 10(21) cm(-3). The plasma temperature, which is obtained by fitting a Planck function to the measured spectrum, is between 7-15 kK. Plasma radius and behavior of the plasma expansion were studied with a streak, a framing or an intensified charge coupled device camera. We compare the measured electrical conductivities with theoretical results, which were obtained solving quantum kinetic equations for the nonideal partially ionized plasmas. In this approach, the transport cross sections are calculated on the level of a T-matrix approximation using effective potentials. The plasma composition is determined from a system of coupled mass action laws with nonideality corrections.

Electrical conductivity measurements of strongly coupled W plasmas.

Nonideal plasmas of tungsten were produced by vaporizing thin wires of 0.1 mm and 0.3 mm in diameter in small glass capillaries (in air) by means of a short-pulse current from an electrical discharge. For a short period of time, the inner wall of the rigid glass capillary confines the plasma until the induced pressure shock wave disintegrates the capillary. Spectroscopic measurements were carried out on the ejected plasma close to the end of the capillary. The plasma temperature was obtained by fitting a Planck function to the measured continuum spectrum. The resistance was derived from the voltage across the plasma and the current through the plasma. The plasma radius was determined with an intensified charge-coupled device camera and a streak camera and allowed the derivation of the conductivity. Particle densities were of the order of 10(22) particle/cm(3) and electron temperatures were in the range from 10 kK to 22 kK. These measurements are compared with theoretical models and previous work.

Psychiatric reform in Germany.

OBJECTIVE: To describe the ongoing process of German psychiatric reform and the structure and functioning of mental health services. METHOD: Information sources used include official reports describing mental health services, relevant publications related to organization and functioning of services. RESULTS: There has been far-reaching change in mental health care since the late 1960s: psychiatric hospitals have lost about 50% of their beds and one psychiatric hospital has been closed. One hundred and sixty-five general hospital psychiatric units have been built up. Out-patient, community and residential services have been developed. There is a lack of diversified residential and rehabilitation services, particularly for the most severely ill. Co-ordination of care is not always ensured, transfer of patients to remote nursing homes has occurred in some places. Carers and service users articulate their views to an increasing degree. CONCLUSION: Political and professional enthusiasm have been important in implementation of the German reform. Evolving it further will require major efforts.

[Basic documentation: inpatient management in a region by a psychiatric hospital and a psychiatric department. Results of a joint evaluation]. / Basisdokumentation: Die stationäre Versorgung einer Region durch ein Psychiatrisches Krankenhaus und eine psychiatrische Abteilung. Ergebnisse einer gemeinsamen Auswertung.

A mental hospital and a psychiatric department of a general hospital in the region of Kassel have jointly analysed their basic documentation to produce an overview of hospital treatment of psychiatric patients in the region. Patients from the urban population occupy twice as many beds as those from the rural population which is a hint that standard bed-ratios per population are inadequate. Instead of the unsuitable official definition of duration of stay in hospital we used "days in hospital per person per year". Making allowance for groups of diagnoses this made possible interesting comparisons about the contributions of the two hospitals to the treatment of the psychiatric patients in the region. The two hospitals are not similar and the results show how the patients make use of the possibility of choosing the various specialities of the two hospitals.

Assessing the quality of psychiatric hospital care: a German approach.

OBJECTIVE: The German Ministry of Health commissioned a nonprofit organization to develop a tool for assessing the quality of psychiatric hospital care. METHODS: The authors were members of an expert group established to develop an assessment tool that could be used by professional caregivers, patients, patients' relatives, managers, purchasers, and mental health care planners. RESULTS: A three-dimensional model was developed in which 23 quality standards may be applied to 28 areas of practice. For each application, questions can be asked at four levels to stimulate ongoing quality management: the individual treatment process, the individual outcome, the treatment unit, and the hospital as a whole. The authors provide sample questions to illustrate the approach. CONCLUSIONS: The approach to quality assessment embodied in the model is comprehensive and addresses ethical issues, but it is also complicated and difficult to handle. Unlike models developed in the United States, it is not intended to be objective or standardized, and it does not yield a score. To some extent, the model's approach to assessment may reflect German cultural values and traditions.