Light-Dependent Resistors as Dosimetric Sensors in Radiotherapy.

Safe quality control of radiotherapy treatments lies in reliable dosimetric sensors. Currently, ionization chambers and solid-state diodes along with electrometers as readout systems are accomplishing this task. In this work, we present a well-known and low-cost semiconductor sensor, the light-dependent resistor (LDR), as an alternative to the existing sensing devices for dosimetry. To demonstrate this, a complete characterization of the response to radiation of commercial LDRs has been conducted in terms of sensitivity, reproducibility and thermal correction under different bias voltages. Irradiation sessions have been applied under the common conditions in radiotherapy treatments using a hospital linear accelerator. Moreover, the same electrometer used for the ionization chamber has also been successfully used for LDRs. In comparison with the sensitivity achieved for the ionization chamber (0.2 nC/cGy at 400 V bias voltage), higher sensitivities have been measured for the proposed LDRs, ranging from 0.24 to 1.04 nC/cGy at bias voltages from 30 to 150 V, with a reproducibility uncertainty among samples of around 10%. In addition, LDR temperature dependence has been properly modeled using the simple thermistor model so that an easy thermal drift correction of dose measurements can be applied. Therefore, experimental results show that LDRs can be a reliable alternative to dosimetric sensors with the advantages of low size, affordable cost and the fact that it could be adopted with minimal changes in routine dosimetry quality control since the same readout system is fully compatible.

Pharmacy customers' experiences with the national online service for viewing electronic prescriptions in Finland.

OBJECTIVES: To investigate (1) Finnish pharmacy customers' familiarity with My Kanta, the national online service for viewing electronic prescriptions (ePrescriptions), (2) how commonly My Kanta is used, (3) who the typical users are, and (4) users' experiences of the usability of My Kanta. METHOD: A survey was conducted among pharmacy customers (aged ≥18) purchasing medicines for themselves. Questionnaires (N=2915) were distributed from 18 community pharmacies across Finland in autumn 2015. The data obtained was stored in SPSS for Windows and subjected to descriptive analysis, chi-square tests and logistic regression analysis. RESULTS: In total, 1288 respondents were included (response rate 44%). Most (62%) of the customers were familiar with My Kanta. The majority of them (78%) were using it to view their ePrescriptions. My Kanta was perceived as clear, easy to use and to provide a good overall picture of the prescribed medications. Familiarity with My Kanta was associated with a higher education than basic school, regular use of prescription medicines, and sufficient information received about ePrescriptions. Men used My Kanta more often than women. Respondents aged 75 or older were less likely to be familiar with and to use the service compared to 18-34year olds. CONCLUSIONS: Most of the Finnish pharmacy customers were familiar with the national online service, My Kanta, for viewing ePrescriptions. Service users perceived it as easy to use and beneficial in managing their overall medication. Customers under 75, those educated beyond basic school, those using prescription medicines regularly, and those who had obtained sufficient information about ePrescriptions were most likely to be familiar with My Kanta. Men and customers under 75 were the typical users of the service. Some customers, however, were unaware of the service, or unable or reluctant to use it.

Perioperative Management of Multiple Noncardiac Implantable Electronic Devices.

The number of patients with noncardiac implantable electronic devices is increasing, and the absence of perioperative management standards, guidelines, practice parameters, or expert consensus statements presents clinical challenges. A 69-year-old woman presented for latissimus dorsi breast reconstruction. The patient had previously undergone implantation of a spinal cord stimulator, a gastric pacemaker, a sacral nerve stimulator, and an intrathecal morphine pump. After consultation with device manufacturers, the devices with patient programmability were switched off. Bipolar cautery was used intraoperatively. Postoperatively, all devices were interrogated to ensure appropriate functioning before home discharge. Perioperative goals include complete preoperative radiologic documentation of device component location, minimizing electromagnetic interference, and avoiding mechanical damage to implanted device components.

Technique for interference reduction in battery powered physiological monitoring devices.

This paper presents a novel simple method to identify and remove systematic interference in battery powered physiological monitoring devices. This interference is very typically introduced via fluctuations in the power supply voltage, caused by the nonideal output resistance of small batteries, when a transceiver chip changes operating modes. The proposed method is designed to have low computational complexity in order to potentially allow for low cost, real-time implementations on low-power-based platforms, either in the system front or back end. Additionally, the paper provides guidelines on how to choose some of the operating conditions of the transceiver in order to minimize the effect of the interference through the application of the proposed method. Overall, successful performance is illustrated with experimental results obtained from an acoustic monitoring system, since this is considered to have specifications which are representative of most physiological monitoring devices.

Long-term two-dimensional pixel stability of EPIDs used for regular linear accelerator quality assurance.

The long-term stability of three clinical electronic portal imaging devices (EPIDs) was studied to determine if longer times between calibrations can be justified. This would make alternatives to flood-field calibration of EPIDs clinically feasible, allowing for more effective use of EPIDs for dosimetry. Images were acquired monthly for each EPID as part of regular clinical quality assurance over a time period of approximately 3 years. The images were analysed to determine (1) the long-term stability of the EPID positioning system, (2) the dose response of the central pixels and (3) the long term stability of each pixel in the imager. The position of the EPID was found to be very repeatable with variations less than 0.3 pixels (0.27 mm) for all imagers (1 standard deviation). The central axis dose response was found to reliably track ion chamber measurements to better than 0.5%. The mean variation in pixel response (1 standard deviation), averaged over all pixels in the EPID, was found to be at most 0.6% for the three EPIDs studied over the entire period. More than 99% of pixels in each EPID showed less than 1% variation. Since the EPID response was found to be very stable over long periods of time, an annual calibration should be sufficient in most cases. More complex dosimetric calibrations should be clinically feasible.

Reliability of goniometric measurements in children with cerebral palsy: a comparative analysis of universal goniometer and electronic inclinometer. A pilot study.

BACKGROUND: Even though technological progress has provided us with more and more sophisticated equipment for making goniometric measurements, the most commonly used clinical tools are still the universal goniometer and, to a lesser extent, the inclinometer. There is, however, no published study so far that uses an inclinometer for measurements in children with cerebral palsy (CP). The objective of this study was two-fold: to independently assess the intra and inter-examiner reliability for measuring the hip abduction range of motion in children with CP using two different instruments, the universal two-axis goniometer and electronic inclinometer. A pool of 5 examiners with different levels of experience as paediatric physiotherapists participated. The study did not compare both instruments because the measurement procedure and the hip position were different for each. METHODS: A prospective, observational study of goniometery was carried out with 14 lower extremities of 7 children with spastic CP. The inclinometer study was carried out with 8 lower extremities of 4 children with spastic CP. This study was divided into two independent parts: a study of the reliability of the hip abduction range of motion measured with a universal goniometer (hip at 0° flexion) and with an electronic inclinometer (hip at 90° flexion). The Intraclass Correlation Coefficient (ICC) was calculated to analyse intra and inter-examiner agreement for each instrument. RESULTS: For the goniometer, the intra-examiner reliability was excellent (>0.80), while the inter-examiner reliability was low (0.375 and 0.475). For the inclinometer, both the intra-examiner (0.850-0.975) and inter-examiner reliability were excellent (0.965 and 0.979). CONCLUSIONS: The inter-examiner reliability for goniometric measurement of hip abduction in children with CP was low, in keeping with other results found in previous publications. The inclinometer has proved to be a highly reliable tool for measuring the hip abduction range of motion in children with CP, which opens up new possibilities in this field, despite having some measurement limitations.

Implementation methodology for interoperable personal health devices with low-voltage low-power constraints.

Traditionally, e-Health solutions were located at the point of care (PoC), while the new ubiquitous user-centered paradigm draws on standard-based personal health devices (PHDs). Such devices place strict constraints on computation and battery efficiency that encouraged the International Organization for Standardization/IEEE11073 (X73) standard for medical devices to evolve from X73PoC to X73PHD. In this context, low-voltage low-power (LV-LP) technologies meet the restrictions of X73PHD-compliant devices. Since X73PHD does not approach the software architecture, the accomplishment of an efficient design falls directly on the software developer. Therefore, computational and battery performance of such LV-LP-constrained devices can even be outperformed through an efficient X73PHD implementation design. In this context, this paper proposes a new methodology to implement X73PHD into microcontroller-based platforms with LV-LP constraints. Such implementation methodology has been developed through a patterns-based approach and applied to a number of X73PHD-compliant agents (including weighing scale, blood pressure monitor, and thermometer specializations) and microprocessor architectures (8, 16, and 32 bits) as a proof of concept. As a reference, the results obtained in the weighing scale guarantee all features of X73PHD running over a microcontroller architecture based on ARM7TDMI requiring only 168 B of RAM and 2546 B of flash memory.

Lead cap localization using ultrasound in deep brain stimulation surgery: technical note.

In deep brain stimulation (DBS) surgery, after intracranial lead implantation, lead caps are tunneled into the subgaleal space for later connection to internal pulse generator (IPG) extension wires. In the subsequent IPG implantation procedure, the lead cap must be localized by palpation in order to plan an incision in the scalp to complete this connection. However, if the IPG implantation is done the same day as the intracranial lead implantation, palpation of the lead cap may be challenging in a thick or postoperatively edematous scalp. Manufacturers suggest using fluoroscopy in these instances, but fluoroscopy provides poor soft tissue visualization, requires further unnecessary radiation exposure to both the patient and the surgical team, and can be cumbersome. Portable ultrasound (US) machines are readily available in many operating rooms, and can be used to easily and accurately localize the lead cap prior to IPG implantation.

Strategies for pacemaker programming in acute heart failure.

In the past decade, cardiac pacing devices (either permanent pacemakers or Implanted Cardioverter Defibrillators) have become increasingly common in patients with heart failure. The manner in which the device is programmed to pace the heart can have significant implications on cardiac hemodynamics, both positive and negative. As such, in patients hospitalized with acute heart failure who have cardiac pacing devices, the clinician should note whether the programming of the device could be contributing to the patient's symptoms, and whether further programming changes could be made to improve the patient's clinical status. As of this date, there are no consensus guidelines available for the management of pacemaker programming in acute heart failure. This review article will discuss the physiologic implications of several parameters of pacemaker programming on heart failure, including the degree of RV pacing, the programmed atrioventricular (AV) interval, and the programmed interventricular pacing delay in patients with cardiac resynchronization therapy (CRT) devices. Based on the available data on the above parameters, this article will then propose a general algorithmic approach to the evaluation and management of patients with pacing devices who are hospitalized with acute heart failure.

Accuracy of diagnoses delivered by an automated hand-held nerve conduction device in comparison to standard electrophysiological testing in patients with unilateral leg symptoms.

INTRODUCTION: Automated hand-held nerve conduction study (NCS) devices are being marketed for use in the diagnosis of lumbosacral radiculopathy (LSR). In this study we compared the specificity and sensitivity of a hand-held NCS device for the detection of LSR with standard electrodiagnostic study (EDX). METHODS: Fifty patients referred to a tertiary referral electromyography (EMG) laboratory for testing of predominantly unilateral leg symptoms (weakness, sensory complaints, and/or pain) were included in the investigation. Twenty-five normal "control" subjects were later recruited to calculate the specificity of the automated protocol. All patients underwent standard EDX and automated testing. RESULTS: Raw NCS data were comparable for both techniques; however, computer-generated interpretations delivered by the automated device showed high sensitivity with low specificity (i.e., many false positives) in both symptomatic patients and normal controls. CONCLUSIONS: The automated device accurately recorded raw data, but the interpretations provided were overly sensitive and lacked the specificity necessary for a screening or diagnostic examination.

Analysis of nerve conduction block induced by direct current.

The mechanisms of nerve conduction block induced by direct current (DC) were investigated using a lumped circuit model of the myelinated axon based on Frankenhaeuser-Huxley (FH) model. Four types of nerve conduction block were observed including anodal DC block, cathodal DC block, virtual anodal DC block, and virtual cathodal DC block. The concept of activating function was used to explain the blocking locations and relation between these different types of nerve block. Anodal/cathodal DC blocks occurred at the axonal nodes under the block electrode, while virtual anodal/cathodal DC blocks occurred at the nodes several millimeters away from the block electrode. Anodal or virtual anodal DC block was caused by hyperpolarization of the axon membrane resulting in the failure of activating sodium channels by the arriving action potential. Cathodal or virtual cathodal DC block was caused by depolarization of the axon membrane resulting in inactivation of the sodium channel. The threshold of cathodal DC block was lower than anodal DC block in most conditions. The threshold of virtual anodal/cathodal blocks was about three to five times higher than the threshold of anodal/cathodal blocks. The blocking threshold was decreased with an increase of axonal diameter, a decrease of electrode distance to axon, or an increase of temperature. This simulation study, which revealed four possible mechanisms of nerve conduction block in myelinated axons induced by DC current, can guide future animal experiments as well as optimize the design of electrodes to block nerve conduction in neuroprosthetic applications.

Improving auscultatory blood pressure measurement with electronic and computer technology: the visual auscultation method.

BACKGROUND: The auscultatory method is used as the reference standard in all prevalent protocols for validation of noninvasive blood pressure measuring devices, and a validation study is essentially based on the comparison between the device and observer measurements. Thus, the objectivity and accuracy of observer measurements are crucial to the validation result. METHODS: To provide observers with more objective information about an auscultatory measurement so that sufficient information to make measurements with greater potential objectivity and accuracy can be available, a computerized data acquisition and analysis system has been developed. It cannot only acquire and store Korotkoff sound, cuff pressure, and oscillometric pulse signals, as well as the sphygmomanometer image, but it also can display the waveforms of the three signals and the sphygmomanometer video while playing the synchronous Korotkoff sounds. With this system, observers can make their measurements via the visual auscultation method, that is to say, by watching those waveforms, instead of the sphygmomanometer, while listening for synchronized Korotkoff sounds. The system was validated according to the International Protocol (IP). RESULTS: The result showed that all the differences between system measurements by the visual auscultation method and observer measurements by the conventional auscultatory method were within 4 mm Hg. CONCLUSIONS: The visual auscultation method achieved a high degree of accuracy, and human observers can be replaced by the system in the validation study of blood pressure measuring devices.

Technical analysis of dual channel pulse generators used in deep brain stimulation; a safety evaluation.

BACKGROUND: A sudden failure of implantable pulse generators (IPG) occurred in 15 out of 143 units during the last 4 years in our patients. This corresponds to a failure rate of 10.5%. In all cases, the connection between the causes of battery and electronic circuit was found defective in the destructive analysis. In order to better understand the failure causes we proceeded to an analysis of explanted IPGs which had reached their normal life span due to depletion of the battery. METHOD: A functional test and an intensive destructive analysis were carried out in 14 units. The internal parts of the IPG were inspected by light and electron microscopy. FINDINGS: Deformations of the connection between battery and electronic circuit could be found in 12 out of 14 IPGs. The epoxy bonds, which achieve the mechanical fixation between the two contact areas of the bond wires, were found separated in 86%. Additionally, in six out of 14 devices the bond wires were either found lifted or with cracks as a sign of material fatigue. CONCLUSION: Based on these results we conclude that the IPGs of the affected series did have a technical weak spot. We presume that this issue appears systematically and not randomly or triggered by an unusual action of the patient.

Data standards and improvement of quality and safety in child health care.

Progress in using information technology to achieve the goal of high-quality health care is hindered by the lack of coordinated data standards. To accelerate quality improvement in pediatrics, child health providers must participate actively in the creation of health care data standards. To do so will require far greater understanding on the part of pediatricians and other pediatric providers regarding the scope and role of data standards in advancing health information systems for children, as well as how data standards could improve quality in child health, what kinds of data standards hold the most promise for quality improvement in child health, and how child health professionals can engage in the work of creating data standards. Child health professionals in organized and academic medicine should participate in standards development organizations, to present the pediatric point of view as data standards emerge. They also should support efforts to certify electronic health record systems that include pediatric functionality. A major challenge to academic pediatrics is to prove that data standards can lead to improved health outcomes for children; this is only a compelling conjecture as of this writing.