Geographically weighted methods for estimating local surfaces of overall,user and producer accuracies

The confusion matrix is the standard way for reporting the accuracy of land cover and other information classified from remote-sensing imagery. This letter describes a geographically weighted method for generating spatially distributed measures of accuracy (overall, user and producer accuracies) from a logistic geographically weighted regression. A kernel-based approach defines the data and weights that are used to calculate the accuracies at each location in the study area. The results compare the global accuracy measures from a standard confusion matrix with those that have been allowed to vary locally. Maps of spatially varying user and producer accuracies describe the spatial autocorrelation of error. The use of geographically weighted models in the context of land cover accuracy is discussed and suggested as a generic approach for examining how and where error processes vary.     

Rigid-body point-based registration: The distribution of the target registration error when the fiducial registration errors are given

Medical guidance systems often employ several data sources using different coordinate systems. In order to map positions from one coordinate system to the other, these guidance systems usually employ rigid-body point-based registration, using pairs of fiducial points: pairs which describe the same physical positions, but in different coordinate systems. The customary test for the quality of the registration is the fiducial registration error (FRE), which is the root-mean-square of the mismatch between the fiducials in each pair (after the registration). The FRE, however, does not give an answer to the question which is usually of interest, and that is the accuracy at a "target" point which is not part of the set of fiducial points. The statistics of the target registration error (TRE) have been studied before and approximate expressions were derived, but those expressions require as input the unknown true fiducial positions. In the present paper, it is proven that by replacing these unknowable true positions with the known measured positions in the expression for mean-square TRE, a higher order approximation is achieved. In other words, it is shown that more accurate estimates are obtained by using less accurate, but available, inputs. Furthermore, in previous approximations FRE and TRE were shown to be statistically independent, whereas here, due to the higher approximation level, it is shown that a slight dependence exists. Thus, the knowledge of FRE can in fact be employed to improve predictions of the TRE statistics. These results are supported by simulations and hold even for fiducial localization error (FLE) distributions with large standard deviations.     

Drug errors and patient safety: the need for a change in practice

Concerns regarding drug errors and public safety have recently been raised in the British national newspapers and professional nursing journals. This literature review considers why nurses may continue to make drug errors in their practice. The findings suggest that drug errors are not caused by any one factor, but are multifaceted in nature. Factors include calculation error, overdosing/underdosing of drug dosages, covert drug administration in food and drink, and an increasingly relaxed attitude among professional nurses with regard to ensuring that drugs are administered to the standard required by law. This article considers the notion that nurses may breach the legal "duty of care" they owe patients by being complacent in their drug administration practice. Consideration of a system's approach to minimize drug error through proactive action planning, risk identification, and implementation of an anonymous incident-reporting framework is briefly explored.     

Drug administration errors: a study into the factors underlying the occurrence and reporting of drug errors in a district general hospital

Drug administration is one of the highest risk areas of nursing practice and a matter of considerable concern for both managers and practitioners The aim of this study, earned out in a district general hospital, was to identify any common themes that underlie the occurrence and reporting of drug administration errors Data were collected from a variety of sources drug error reports, questionnaires to nurses and nurse managers, and interviews with nurses who had been involved in drug errors Several areas of particular concern emerged, including the nurses' confusion regarding the definition of drug errors and the appropriate actions to take when they occurred, their fear of disciplinary action, their loss of clinical confidence, the variation in managerial response, and a possible lack of nurses' mathematical skills The results from the study demonstrated that it was likely that many drug errors were not reported, for a variety of reasons It is recommended that all of these issues are addressed as a matter of urgency, for the sake of both patients and nurse practitioners     

Prevalence of errors in a pediatric hospital medication system: implications for error proofing

The purpose of this study was to determine the prevalence of errors in the medication system of a pediatric teaching hospital. Error was defined broadly to capture all deviations in the process from medication order through administration of the dose. The long-term goal was to provide direction to efforts to error-proof the system. The sample was 3,312 medication orders written during 669 patient-days for which a total of 11,978 doses were passed. Errors were categorized as intercepted errors (intercepted through the normal processes of the medication system) or administration errors (errors that involve the patient with or without adverse sequelae). Errors were also categorized as errors in primary activities (e.g., prescribing or preparing the medication for administration) or supporting activity (e.g., transferring the order to another record). A total of 784 errors were identified; 98% were intercepted and 2% were administration errors. More errors (71%) occurred in supporting activities than in primary activities. Medication systems are complex processes. Errors are imbedded in the medication system and are typically intercepted before patients are involved. Intercepting errors involves additional work that adds to an already cumbersome process. Error proofing will be different for errors in primary activities and for supporting activities.     

Electronic error-reporting systems: A case study into the impact on nurse reporting of medical errors

BackgroundUnderreporting of errors in hospitals persists despite the claims of technology companies that electronic systems will facilitate reporting. This study builds on previous analyses to examine error reporting by nurses in hospitals using electronic media.PurposeThis research asks whether the electronic media creates additional barriers to error reporting, and, if so, what practical steps can all hospitals take to reduce these barriers.MethodThis is a mixed-method case study nurses’ use of an error reporting system, RiskMan, in two hospitals. The case study involved one large private hospital and one large public hospital in Victoria, Australia, both of which use the RiskMan medical error reporting system.ConclusionInformation technology–based error reporting systems have unique access problems and time demands and can encourage nurses to develop alternative reporting mechanisms. This research focuses on nurses and raises important findings for hospitals using such systems or considering installation. This article suggests organizational and technical responses that could reduce some of the identified barriers.     

Living at the sharp end: moral obligations of nurses in reporting and disclosing errors in health care

Nurses are mandated to keep patients safe. When that safety is threatened by a nursing error, the nurse as a moral agent has the obligation to report and disclose the error to the appropriate people honestly and fully. Telling the truth should be a closely held value by all nurses. Nurses must continue to act as advocates for their patients while recognizing their own human frailties. Human errors are inevitable in the practice of nursing. They cannot completely be eradicated, although they can be reduced. Nursing's ethical imperative is to exhaust our efforts in correcting the processes and situations that lead to error.     

Disclosure of medical errors: ethical considerations for the development of a facility policy and organizational culture change

The Institute of Medicine report, To Err Is Human: Building a Safer Health System, has spurred public concern over hospitals' ability to deliver safe care. The health care industry continues to struggle to address these concerns. These efforts have driven the growing expectation that health care practitioners or systems disclose unanticipated outcomes to patients and family members. Although the tort system has been cited as an impediment to medical error disclosure, some organizations and systems have successfully implemented policies calling for full disclosure of errors and unanticipated outcomes. However, most organizations have yet to develop policies concerning error disclosure. This article provides an overview of error disclosure and a model framework for an error disclosure policy. The ethical principle of respect for patient autonomy is emphasized as the driving force in developing an institutional disclosure policy and changing the organizational culture to one that supports development and implementation of such a policy.     

体素内不相干运动扩散加权成像及T1mapping评价自身免疫性胰腺炎的临床研究

目的探讨磁共振体素内不相干运动扩散加权成像(intravoxel incoherentmotion diffusion weighted imaging,IVIM-DWI)及T1 mapping在评价自身免疫性胰腺炎(autoimmune pancreatitis,AIP)中的价值。材料与方法 26例AIP患者及18例健康志愿者、39例胰腺癌(pancreatic cancer,PC)患者行IVIM-DWI及T1 mapping检查,b值分别为0、25、75、100、150、200、500、800及1000 s/mm^2,AIP以病理诊断或临床证实,PC均由手术及病理证实,分析正常胰腺、PC及AIP之间的T1值、IVIM-DWI成像参数[真实扩散系数(D),假性扩散系数(D^*)和灌注分数(f)]差异,采用受试者工作曲线(receiveroperating characteristic curve,ROC)评价D、D^*、f值鉴别AIP及PC、AIP与正常胰腺的效能。结果 f值在志愿者、PC及AIP三组的值分别为(20.6±4.2)%、(12.0±3.7)%及(9.1±3.1)%,三组差异有统计学意义(P<0.001)。f值在鉴别志愿者与AIP,AIP与PC的曲线下面积(area under curve,AUC)分别为0.970和0.747,均高于T1值(AUC=0.949,0.685)、D^*(AUC=0.825,0.493)和D (AUC=0.513,0.582)。结论采用磁共振IVIMDWI灌注分数f鉴别诊断AIP具有良好的前景。     

Adverse effects and medication errors: incidence and role of the organization of drug distribution

The true incidence of adverse drug events is controversial and there are few data concerning the percentage of potentially preventable adverse drug events. Over 2 months, in two internal medicine units, we asked the staff to report adverse drug events. All incidents were evaluated: adverse drug events (preventable and non-preventable) and potential adverse drug events (non-intercepted potential adverse drug events and intercepted potential adverse drug events). The severity, the stage in the process at which the error occurred and the type of error were evaluated by a physician reviewer. Over the 240 admissions, the incidence of adverse drug events is 18 per 1000 patient-days. The system design caused 77 per cent of the incidents. The medication errors occurred at all stages from ordering to administration. Adverse drug events resulting in medication errors (n = 22) were more serious than non-preventable adverse drug events (n = 26) (p = 0.003). A prevention strategy by pharmacovigilance centres (Centres Régionaux de Pharmacovigilance) should target all stages of the drug delivery process.     

Quantitative analysis of spatial sampling error in the infant and adult electroencephalogram

The purpose of this report was to determine the required number of electrodes to record the infant and adult electroencephalogram (EEG) with a specified amount of spatial sampling error. We first developed mathematical theory that governs the spatial sampling of EEG data distributed on a spherical approximation to the scalp. We then used a concentric sphere model of current flow in the head to simulate realistic EEG data. Quantitative spatial sampling error was calculated for the simulated EEG, with additive measurement noise, for 64, 128, and 256 electrodes equally spaced over the surface of the sphere corresponding to the coverage of the human scalp by commercially available "geodesic" electrode arrays. We found the sampling error for the infant to be larger than that for the adult. For example, a sampling error of less than 10% for the adult was obtained with a 64-electrode array but a 256-electrode array was needed for the infant to achieve the same level of error. With the addition of measurement noise, with power 10 times less than that of the EEG, the sampling error increased to 25% for both the infant and adult, for these numbers of electrodes. These results show that accurate measurement of the spatial properties of the infant EEG requires more electrodes than for the adult.     

Neural mechanisms involved in error processing: a comparison of errors made with and without awareness

The ability to detect an error in one's own performance and then to improve ongoing performance based on this error processing is critical for effective behaviour. In our event-related fMRI experiment, we show that explicit awareness of a response inhibition commission error and subsequent post-error behaviour were associated with bilateral prefrontal and parietal brain activation. Activity in the anterior cingulate region, typically associated with error detection, was equivalent for both errors subjects were aware of and those they were not aware of making. While anterior cingulate activation has repeatedly been associated with error-related processing, these results suggest that, in isolation, it is not sufficient for conscious awareness of errors or post-error adaptation of response strategies. Instead, it appears, irrespective of awareness, to detect information about stimuli/responses that requires interpretation in other brain regions for strategic implementation of post-error adjustments of behaviour.     

MRI anatomical mapping and direct stereotactic targeting in the subthalamic region: functional and anatomical correspondence in Parkinson’s disease

Object Relationships between clinical effects, anatomy, and electrophysiology are not fully understood in DBS of the subthalamic region in Parkinson’s disease. We proposed an anatomic study based on direct image-guided stereotactic surgery with a multiple source data analysis. Materials and Methods A manual anatomic mapping was realized on coronal 1.5-Tesla MRI of 15 patients. Biological data were collected under local anesthesia: the spontaneous neuron activities and the clinical efficiency and the appearance of adverse effects. They were related to relevant current values (mA), the benefit threshold (bt, minimal current leading an clear efficiency), the adverse effect threshold (at, minimal current leading an adverse effect) and the stimulation margin (sm = at − bt); they were matched with anatomy. Results We found consistent relationships between anatomy and biological data. The optimal stimulation parameters (low bt + high sm) were noted in the dorsolateral STN. The highest spontaneous neuron activity was found in the ventromedial STN. Dorsolateral (sensorimotor) STN seems the main DBS effector. The highest spontaneous neuron activity seems related to the anterior (rostral) ventromedial (limbic) STN. Conclusion 1.5 Tesla images provide sufficiently detailed subthalamic anatomy for image-guided stereotactic surgery and may aid in understanding DBS mechanisms.