Sensation seeking and executive deficits in relation to alcohol, tobacco, and marijuana use frequency among university students: Value of ecologically based measures.

INTRODUCTION: The development of substance use and addiction has been linked to impaired executive function which relies on systems that converge in the prefrontal cortex. This study examined several measures of executive function as predictors of college student alcohol, tobacco, and marijuana use frequency and abuse. METHODS: College students (N=321) were administered the Delis-Kaplan Executive Function System (D-KEFS) test battery, the Sensation Seeking Scale V (SSSV), the Frontal Systems Behavioral Scale (FrSBe), the Perceived Stress Scale (PSS), the Michigan Alcohol Screening Test (MAST), the Fagerstrom Test of Nicotine Dependence (FTND). RESULTS: Alcohol use frequency was predicted by sensation seeking and FrSBe Disinhibition scores, but the latter only emerged as a unique predictor for binge drinking frequency. Sex and Disinhibition, Apathy and Executive Function FrSBe subscales predicted the frequency of tobacco use. FrSBe scores uniquely predicted tobacco use among daily users. Marijuana use frequency was predicted by sensation seeking, sex, perceived stress, and FrSBe Disinhibition scores, but only sensation seeking predicted daily use after controlling for other variables. FrSBe Disinhibition scores reached levels considered to be clinically significant for frequent binge drinkers and daily marijuana users. Sensation seeking emerged as the predominate predictor of the early stages of alcohol and tobacco related problems. CONCLUSIONS: These results suggest ecologically based self-report measures of frontal lobe function and sensation seeking are significant predictors of use frequency among college students and the extent of frontal dysfunction may be clinically significant among some heavy users.

Megavoltage quality control, resources and demand: a pragmatic review.

OBJECTIVE: Satisfactory radiotherapy treatment requires quality control (QC) of the equipment as well as patient-specific checks. Increased complexity and extended use of equipment plus greater demand for complex treatment has brought pressure on QC resources. The benefits of integrating patient-specific checks and QC and the efficient use of resources is examined. METHODS: A non-linear model for the probability of undetected machine failure is proposed which enables the comparative efficiency of resource to be assessed. Benefits of adopting an integrated view of patient-specific and treatment machine QC is considered, considering performance tolerance levels in the context of measurement uncertainty and patient-specific tolerances. RESULTS: Essential, machine-only QC is identified. A realistic approach to equipment-only QC is identified for 70% efficient use of resources and a relationship established to determine resource required for a QC programme. Integration of patient-specific and equipment QC is shown to half the resource required for equipment QC. CONCLUSION: Increasing benefit from QC requires greater resource, working at lower efficiency. A pragmatic approach is having guaranteed checks supplemented with additional, non-guaranteed checks performed within an integrated approach to machine- and patient-specific QC, bearing in mind the occasions when machine-only QC is essential. ADVANCES IN KNOWLEDGE: The work reveals on a quantitative basis a rational approach to accommodating the QC requirements for safe and effective treatment.

IGRT/ART phantom with programmable independent rib cage and tumor motion.

PURPOSE: This paper describes the design and experimental evaluation of the Methods and Advanced Equipment for Simulation and Treatment in Radiation Oncology (MAESTRO) thorax phantom, a new anthropomorphic moving ribcage combined with a 3D tumor positioning system to move target inserts within static lungs. METHODS: The new rib cage design is described and its motion is evaluated using Vicon Nexus, a commercial 3D motion tracking system. CT studies at inhale and exhale position are used to study the effect of rib motion and tissue equivalence. RESULTS: The 3D target positioning system and the rib cage have millimetre accuracy. Each axis of motion can reproduce given trajectories from files or individually programmed sinusoidal motion in terms of amplitude, period, and phase shift. The maximum rib motion ranges from 7 to 20 mm SI and from 0.3 to 3.7 mm AP with LR motion less than 1 mm. The repeatability between cycles is within 0.16 mm root mean square error. The agreement between CT electron and mass density for skin, ribcage, spine hard and inner bone as well as cartilage is within 3%. CONCLUSIONS: The MAESTRO phantom is a useful research tool that produces programmable 3D rib motions which can be synchronized with 3D internal target motion. The easily accessible static lungs enable the use of a wide range of inserts or can be filled with lung tissue equivalent and deformed using the target motion system.

Couch-based motion compensation: modelling, simulation and real-time experiments.

The paper presents a couch-based active motion compensation strategy evaluated in simulation and validated experimentally using both a research and a clinical Elekta Precise Table™. The control strategy combines a Kalman filter to predict the surrogate motion used as a reference by a linear model predictive controller with the control action calculation based on estimated position and velocity feedback provided by an observer as well as predicted couch position and velocity using a linearized state space model. An inversion technique is used to compensate for the dead-zone nonlinearity. New generic couch models are presented and applied to model the Elekta Precise Table™ dynamics and nonlinearities including dead zone. Couch deflection was measured for different manufacturers and found to be up to 25 mm. A feed-forward approach is proposed to compensate for such couch deflection. Simultaneous motion compensation for longitudinal, lateral and vertical motions was evaluated using arbitrary trajectories generated from sensors or loaded from files. Tracking errors were between 0.5 and 2 mm RMS. A dosimetric evaluation of the motion compensation was done using a sinusoidal waveform. No notable differences were observed between films obtained for a fixed- or motion-compensated target. Further dosimetric improvement could be made by combining gating, based on tracking error together with beam on/off time, and PSS compensation.

Hallucinogens as hard science: the adrenochrome hypothesis for the biogenesis of schizophrenia.

Working in a psychiatrically innovative environment created by the Government of Saskatchewan, Canada, Abram Hoffer and Humphry F. Osmond enunciated the adrenochrome hypothesis for the biogenesis of schizophrenia in 1952, slightly later proposing and, apparently, demonstrating, in a double-blind study, that the symptoms of the illness could be reversed by administering large doses of niacin. After placing the hypothesis within its ideological framework, the author describes its emergence and elaboration and discusses the empirical evidence brought against it. Hoffer's idiosyncratic diagnostic procedures, especially his creation and use of a supposed biochemical marker for schizophrenia, are examined. The author argues that Hoffer's conceptualization of schizophrenia, as well as his treatment approach, depended on a tautology. Following David Healy, the author treats the adrenochrome hypothesis as a version of a transmethylation theory, thus incorporating it into mainstream psychopharmacology.

An analysis of the origin of differences between measured and simulated fields produced by a 15-element ultrasound phased array.

Modeling provides an attractive approach for the design of phased array ultrasound transducers for hyperthermia. However, measurements on physical transducers reveal differences from the idealized field profiles predicted by simulation. In this paper we report a method of analyzing the origins of these differences. The measured performance of a 15-element sparse phased array is described and compared with simulated fields calculated using the point source method. It highlighted two notable differences: First, that the focal region was located closer to the surface of the physical transducer than in the simulated fields; and second, that numerous intensity maxima were present between the surface of the transducer and the focal zone in the experimental data, but not in the simulated fields. We identified six factors that could potentially affect the field but were not taken into account by the default simulations, and we performed a sensitivity analysis on these: (i) Variation in the amplitude of the output from each element, (ii) the presence of square-wave harmonics in the drive signals, (iii) nonpistonlike vibration of elements, (iv) quantization of the applied phases, (v) errors in the spatial positioning of each element; and (vi) interelement cross-coupling. Both the independent impact of each factor and the interactions between multiple factors were analyzed by using a full-factorial experimental design composed of 64 (2(6)) simulations. The results indicated that nonpistonlike motion of elements is likely to be the primary cause of differences between the measured and modelled fields. Determination of the precise vibrational modes of elements in an array is complex and would require full finite element analysis. However, the simple vibrational mode considered within the present work, corresponding to the addition of a surface Rayleigh wave originating at the element center and propagating radially, produced simulation results that were in good agreement with the measured data.

Trust amply recompensed: psychological research at Weyburn, Saskatchewan, 1957-1961.

During the 1950s and 1960s professionals intensely debated the prospect of changes in the mental health system, largely as a result of the introduction of new therapies, revised theories of mental disorder, and shifting policies governing mental health accommodation. As well as giving rise to new subspecialties within medicine, psychiatrists in some jurisdictions at this time worked closely with psychologists in an attempt to offer a more comprehensive set of options that merged theory with practice. In Saskatchewan, mental health professionals worked closely with government officials and bureaucrats and produced a variety of innovative strategies that addressed changing priorities in this system. This article examines the role played by psychologists in Saskatchewan during this period as they worked cooperatively with psychiatrists and bureaucrats to merge medical, psychological, and political perspectives in a system aimed at accommodating mental illness in the wake of new theories and treatments that questioned the efficacy of care in institutionalized settings in the wake of growing suggestions for care in the community.

The design and characterization of an ultrasound phased array suitable for deep tissue hyperthermia.

In this paper we describe the design and evaluation of a planar phased-array ultrasound transducer suitable for producing localized hyperthermia in solid tumors deep within the body. Simulation using a customized version of Ultrasim has been used to determine the relationship between the size and position of the focus and parameters of the array. These parameters include the overall size of the array and the size, shape and distribution of the individual elements. A 15-element prototype array has been constructed using the results of the simulation. Beam profile measurements on this transducer made in an acoustic tank were compared with the beam profile predicted by simulation. The results showed good agreement in the shape of the focal region, but with the focus closer to the surface of the physical transducer when compared with the simulation and with small high-intensity areas between the surface of the transducer and the focus in the measured profile. A sensitivity analysis using a simulated factorial experiment indicated that the presence of a secondary vibrational mode within the elements of the array was the principal cause for both the shift in the position of the focus and for the unwanted maxima close to the surface of the array. The results also showed that the array was tolerant of a large variation in output intensity of the individual elements in the array in producing a focal region. Extrapolation of the results obtained in this study indicate that an array of 60 elements, based on the design described, driven by 550 V peak-to-peak pulses would be capable of producing a peak focal intensity of 50 Wcm(-2) at a depth of 60 mm in tissue, which would be appropriate for hyperthermia used as an adjunct to radiotherapy or chemotherapy.

An assessment of GafChromic film for measuring 50 kV and 100 kV percentage depth dose curves.

Percentage depth dose (PDD) curves were obtained for 50 kV and 100 kV x-rays on a Gulmay Medical D3000 DXR unit. Different dosimetry systems were compared including a Scanditronix Wellhofer small volume cylindrical ion chamber, a Wellhofer photon PFD diode, a PTW soft x-ray parallel plate chamber (N23342) and two types of radiochromic film: GafChromic EBT and GafChromic MD55. The PDD curves were also compared to BEAMnrc Monte Carlo predictions. GafChromic film was found to be a valid choice of dosimeter for measuring percentage depth dose curves at 100 kV and 50 kV. All the dosimeters showed agreement with predictions at depths greater than 10 mm, while near the surface GafChromic film and PFD diodes give the best agreement to Monte Carlo values.

A multiple model approach to respiratory motion prediction for real-time IGRT.

Respiration induces significant movement of tumours in the vicinity of thoracic and abdominal structures. Real-time image-guided radiotherapy (IGRT) aims to adapt radiation delivery to tumour motion during irradiation. One of the main problems for achieving this objective is the presence of time lag between the acquisition of tumour position and the radiation delivery. Such time lag causes significant beam positioning errors and affects the dose coverage. A method to solve this problem is to employ an algorithm that is able to predict future tumour positions from available tumour position measurements. This paper presents a multiple model approach to respiratory-induced tumour motion prediction using the interacting multiple model (IMM) filter. A combination of two models, constant velocity (CV) and constant acceleration (CA), is used to capture respiratory-induced tumour motion. A Kalman filter is designed for each of the local models and the IMM filter is applied to combine the predictions of these Kalman filters for obtaining the predicted tumour position. The IMM filter, likewise the Kalman filter, is a recursive algorithm that is suitable for real-time applications. In addition, this paper proposes a confidence interval (CI) criterion to evaluate the performance of tumour motion prediction algorithms for IGRT. The proposed CI criterion provides a relevant measure for the prediction performance in terms of clinical applications and can be used to specify the margin to accommodate prediction errors. The prediction performance of the IMM filter has been evaluated using 110 traces of 4-minute free-breathing motion collected from 24 lung-cancer patients. The simulation study was carried out for prediction time 0.1-0.6 s with sampling rates 3, 5 and 10 Hz. It was found that the prediction of the IMM filter was consistently better than the prediction of the Kalman filter with the CV or CA model. There was no significant difference of prediction errors for the sampling rates 5 and 10 Hz. For these sampling rates, the errors of the IMM filter for 0.4 s prediction time were less than 2.1 mm in terms of the 95% CI criterion or 1.1 mm in terms of the standard deviation (SD) or root mean squared errors (RMSE) criterion. For the prediction time of 0.6 s the errors were less than 3.6 mm in terms of the 95% CI criterion or 1.8 mm in terms of the SD/RMSE criterion. The prediction error analysis showed that the average percentage of the target lies outside the 95% CI margin was 5.2% and outside the SD/RMSE margin was 24.3%. This indicates the effectiveness of the 95% CI criterion as a margining strategy to accommodate prediction errors.

A new approach to quantify the mechanical and radiation isocentres of radiotherapy treatment machine gantries.

In this paper a new method is proposed to quantify and reduce the radiation beam position uncertainty due to the radiotherapy treatment machine gantry deflection. A new tool has been designed and manufactured to provide the means to measure the alignment of the collimator axis and of the beam central axis in space, using the NDI Polaris optical tracking system and Gafchromic films. The tool can be mounted onto the accessory tray of the linacs from different manufacturers. The approach has been demonstrated with measurements of the mechanical isocentre being performed on ten linacs from three major manufacturers at four clinical sites. Measurements of the radiation isocentre were performed on a single linac. The collimator axis trajectory is modelled using a vector-end effector in order to provide more information than standard mechanical assessment methods. The method uses a mathematical optimization technique to calculate the position of the mechanical isocentre and the 'size' of the collimator axes intersection locus. Deviations of the collimator axes from the isocentre are expressed in terms of systematic and random error. The effects of measurement uncertainties are evaluated both via simulations and experimentally. The use of optical tracking and optimization techniques combined with an operator-induced measurement error compensation algorithm leads to a faster measurement of the mechanical isocentre (20 min for 24 angles) and eliminates operator-induced uncertainties. The uncertainty of the measurement of the mechanical isocentre was between 40 microm and 70 microm in terms of standard deviation. For some of the linacs assessed, the mechanical isocentre obtained using a standard approach with an adjustable pointer was displaced by over 1 mm from that found with the proposed method. The radii of the collimator axes intersection locus found with the proposed method were between 0.4 mm and 0.72 mm for the linacs assessed. Film measurement revealed a misalignment of the mechanical isocentre and the radiation isocentre by 0.4 mm. The proposed method potentially enables a reduction of the beam position uncertainty. This may be achieved at the planning stage by compensating for the identified systematic collimator axes deviations which were found to be reproducible. The method also creates a potential for using different setup margins independently for each axis and for each gantry angle, calculated specifically for a given linac.

John Rickman, Wilfred Ruprecht Bion, and the origins of the therapeutic community.

The history of psychiatric therapeutic communities is complex and obscure. Nevertheless, one can make a reasonable case for saying that the first true therapeutic community was created at Northfield Military Hospital, Birmingham, England, in 1945. That community had its origins in the thought and practice of two British psychoanalysts, John Rickman and Wilfred Ruprecht Bion. Accordingly, in the present article their careers and the social and intellectual influences bearing on them are discussed. The article then continues by describing Rickman's work as a military psychiatrist, Bion's prototype of a therapeutic community, and the therapeutic community that was eventually created at Northfield. It is hoped that the article will provide some of the groundwork for an adequate history of the therapeutic community.

Lessons from the periphery: psychiatry in Saskatchewan, Canada, 1944-68.

The government of the Saskatchewan Co-Operative Commonwealth Federation, when elected in 1944, established programmes for the state-funded care of all those suffering from mental illness. It enacted legislation covering the care and treatment of the mentally ill and created a division of the Department of Public Health, the Psychiatric Services Branch (PSB), which both recruited and trained psychiatric staff, meeting the need for nonmedical staff by creating a programme for the training of psychiatric nurses in Saskatchewan. The PSB devised the Saskatchewan Plan for the delivery of rural services, centred on small mental hospitals of a revolutionary design. Even though never fully instantiated, the Plan commanded worldwide attention. Saskatchewan was also remarkable for its research programmes, covering almost all aspects of psychiatry.