Action-related eye measures to assess surgical expertise.

BACKGROUND: Eye-tracking offers a new list of performance measures for surgeons. Previous studies of eye-tracking have reported that action-related fixation is a good measuring tool for elite task performers. Other measures, including early eye engagement to target and early eye disengagement from the previous subtask, were also reported to distinguish between different expertise levels. These parameters were examined during laparoscopic surgery simulations in the present study, with a goal to identify the most useful measures for distinguishing surgical expertise. METHODS: Surgical operators, including experienced surgeons (expert), residents (intermediate), and university students (novice), were required to perform a laparoscopic task involving reaching, grasping, and loading, while their eye movements and performance videos were recorded. Spatiotemporal features of eye-hand coordination and action-related fixation were calculated and compared among the groups. RESULTS: The study included five experienced surgeons, seven residents, and 14 novices. Overall, experts performed tasks faster than novices. Examining eye-hand coordination on each subtask, it was found that experts managed to disengage their eyes earlier from the previous subtask, whereas novices disengaged their eyes from previous subtask with a significant delay. Early eye engagement to the current subtask was observed for all operators. There was no difference in action-related fixation between experienced surgeons and novices. Disengage time was strongly associated with the surgical experience score of the operators, better than both early-engage time and action-related fixation. CONCLUSION: The spatiotemporal features of surgeons' eye-hand coordination can be used to assess level of surgical experience.

Evaluating different radiology workstation interaction techniques with radiologists and laypersons.

This paper presents a new methodology for evaluating radiology workstation interaction features, using lay subjects to perform a radiology look-alike task with artificial stimuli. We validated this methodology by evaluating two different workstation interaction techniques with two groups of subjects: laypersons and radiologists, using a set of artificial targets to simulate the reading of a diagnostic examination. Overall, the results from the two groups of subjects performing the same tasks were very similar. Both groups showed significantly faster response times using a new interaction technique, and the mouse clicks for both groups were very similar, showing that all the subjects mastered the style of interaction in a similar way. The errors made by both groups were comparable. These results show that it is possible to test new workstation interaction features using look-alike radiological tasks and inexperienced laypersons, and that the results do transfer to radiologists performing the same tasks.

Exploring presentation methods for tomographic medical image viewing.

This paper explores the presentation of tomographic medical images on a computer screen. Limitations of the computer screen are apparent, as even a very large computer monitor cannot display an entire study consisting of dozens of images at once. Our objective is to propose filmless computer presentation methods for these images, in particular for magnetic resonance images. First, we observe the magnetic resonance image analysis task in the traditional light screen environment where presentation of many images has always been possible. We then propose solutions for meeting requirements in the computer environment. After implementation of these solutions we obtain user feedback on alternatives in order to determine feasibility and preference. Observations reveal three requirement categories: user control of film management, navigation of images and image series, and simultaneous availability of detail and context. We developed a framework of detail-in-context-technique parameters for the purpose of viewing tomographic medical images and presented our solution directions to the radiologists for feedback. Results from the user feedback study support the feasibility of the proposed approaches and clearly indicate the importance of presentation issues in the development of medical imaging viewing systems.

Wavelet-based space-frequency compression of ultrasound images.

This paper describes the compression of grayscale medical ultrasound images using a recent compression technique, i.e., space-frequency segmentation (SFS). This method finds the rate-distortion optimal representation of an image from a large set of possible space-frequency partitions and quantizer combinations and is especially effective when the images to code are statistically inhomogeneous, which is the case for medical ultrasound images. We implemented a compression application based on this method and tested the algorithm on representative ultrasound images. The result is an effective technique that performs better than a leading wavelet-transform coding algorithm, i.e., set partitioning in hierarchical trees (SPIHT), using standard objective distortion measures. To determine the subjective qualitative performance, an expert viewer study was run by presenting ultrasound radiologists with images compressed using both SFS and SPIHT. The results confirmed the objective performance rankings. Finally, the performance sensitivity of the space-frequency codec is shown with respect to several parameters, and the characteristic space-frequency partitions found for ultrasound images are discussed.

Ancyromonadida: a new phylogenetic lineage among the protozoa closely related to the common ancestor of metazoans, fungi, and choanoflagellates (Opisthokonta).

Molecular and morphological evidence points to the ancyromonad Ancyromonas as a plausible candidate for the closest relative to the common ancestor of metazoans, fungi, and choanoflagellates (the Opisthokonta). Using 18S rDNA sequences from most of the major eukaryotic lineages, maximum-likelihood, minimum-evolution, and maximum-parsimony analyses yielded congruent phylogenies supporting this hypothesis. Combined with ultrastructural similarities between Ancyromonas and opisthokonts, the evidence presented here suggests that Ancyromonas may form an independent lineage, the Ancyromonadida Cavalier-Smith 1997, closer in its relationship to the opisthokonts than is its nearest protist relatives, the Apusomonadida. However, the very low bootstrap support for deep nodes and hypothesis testing indicate that the resolving power of 18S rDNA sequences is limited for examining this aspect of eukaryotic phylogeny. Alternate branching positions for the Ancyromonas lineage cannot be robustly rejected, revealing the importance of ultrastructure when examining the origins of multicellularity. The future use of a multigene approach may additionally be needed to resolve this aspect of eukaryotic phylogeny.

A survey of flagellate diversity at four deep-sea hydrothermal vents in the Eastern Pacific Ocean using structural and molecular approaches.

Eighteen strains of flagellated protists representing nine species were isolated and cultured from four deep-sea hydrothermal vents: Juan de Fuca Ridge (2,200 m), Guaymas Basin (2,000 m), 21 degrees N (2,550 m) and 9 degrees N (2,000 m). Light and electron microscopy were used to identify flagellates to genus and, when possible, species. The small subunit ribosomal RNA genes of each vent species and related strains from shallow-waters and the American Type Culture Collection were sequenced then used for comparative analysis with database sequences to place taxa in an rDNA tree. The hydrothermal vent flagellates belonged to six different taxonomic orders: the Ancyromonadida, Bicosoecida, Cercomonadida, Choanoflagellida, Chrysomonadida, and Kinetoplastida. Comparative analysis of vent isolate and database sequences resolved systematic placement of some well-known species with previously uncertain taxonomic affinities, such as Ancyromonas sigmoides, Caecitellus parvulus, and Massisteria marina. Many of these vent isolates are ubiquitous members of marine, freshwater, and terrestrial ecosystems worldwide, suggesting a global distribution of these flagellate species.

Adopted children's behavior problems: a review of five explanatory models.

Although the majority of adopted children are well-adjusted, adopted children evidence proportionately more behavior problems when compared to nonadopted children in both clinic and nonclinic populations. An extensive literature examining behavioral, diagnostic, and demographic characteristics of adopted children has provided several plausible explanations for the high rate of behavior problems among adopted children. In this review, the existing literature is organized into five explanatory models: (a) genetic or "biosocial" factors, (b) pathogenesis of the adoption process, (c) long-term effects of impaired preadoption childrearing, (d) referral bias in adoptive parents, and (e) impaired adoptive parent-adoptee relations. We conclude that evidence for each model is mixed at best. Especially noteworthy is the mixed results for genetic or biosocial studies and the relative absence of studies focused on identifying factors associated with disruptions in the adoptive parent-adoptee relationship. We propose that a psychosocial model to explain the high rate of behavior problems among adopted children is highly plausible and further suggest that it may be time for a new awareness and appreciation for the normative aspects of adoption. An overview of parenting and family characteristics associated with risk factors for antisocial behavior is provided as a guide for future research.

Fully automatic segmentation of the brain in MRI.

A robust fully automatic method for segmenting the brain from head magnetic resonance (MR) images has been developed, which works even in the presence of radio frequency (RF) inhomogeneities. It has been successful in segmenting the brain in every slice from head images acquired from several different MRI scanners, using different-resolution images and different echo sequences. The method uses an integrated approach which employs image processing techniques based on anisotropic filters and "snakes" contouring techniques, and a priori knowledge, which is used to remove the eyes, which are tricky to remove based on image intensity alone. It is a multistage process, involving first removal of the background noise leaving a head mask, then finding a rough outline of the brain, then refinement of the rough brain outline to a final mask. The paper describes the main features of the method, and gives results for some brain studies.

An ecological model for school-based mental health services for urban low-income aggressive children.

An ecological model for school-based mental health services that targets urban low-income aggressive children--a highly vulnerable and underserved population--is presented. The goals of the model are to increase children's and teachers' involvement in the delivery of services and to increase the integration of these services into existing school resources and activities. The model proposes that mental health service providers work in collaboration with teachers to deliver services that (1) can be managed by existing school resources and personnel, (2) are related to empirically based factors associated with reduced aggression and increased social functioning, and (3) are group administered to increase the number of children served and to reduce stigmatization associated with mental health services. The model is individualized and flexible by acknowledging that contexts for aggression differ across classrooms and children and by providing services specific to those contexts. Two studies are presented illustrating the application of this model to decrease aggression and increase academic engagement in low-income urban public schools.

A revised teacher rating scale for reactive and proactive aggression.

A teacher rating scale of reactive aggression, proactive aggression, and covert antisocial behavior was evaluated in a normative sample of third- to fifth-grade predominantly white lower middle class boys (N = 186). Factor analysis revealed independent and internally consistent Reactive Aggression (six reactive items), and Proactive Aggression (five proactive items, five covert items) factors. Although the factors were intercorrelated (r = .67), and each factor was significantly correlated with negative peer social status (r = .26 for each, controlling for grade), the independence of the factors was supported by the unique relation of Reactive Aggression with in-school detentions (r = .31), controlling for Proactive Aggression and grade. These results supported the reliability and validity of Reactive and Proactive Aggression as rated by teachers, which should facilitate further research of these constructs.

Segmentation of multiple sclerosis lesions in intensity corrected multispectral MRI.

To segment brain tissues in magnetic resonance images of the brain, the authors have implemented a stochastic relaxation method which utilizes partial volume analysis for every brain voxel, and operates on fully three-dimensional (3-D) data. However, there are still problems with automatically or semi-automatically segmenting thick magnetic resonance (MR) slices, particularly when trying to segment the small lesions present in MR images of multiple sclerosis patients. To improve lesion segmentation the authors have extended their method of stochastic relaxation by both pre- and post-processing the MR images. The preprocessing step involves image enhancement using homomorphic filtering to correct for nonhomogeneities in the coil and magnet. Because approximately 95% of all multiple sclerosis lesions occur in the white matter of the brain, the post-processing step involves application of morphological processing and thresholding techniques to the intermediate segmentation in order to develop a mask image containing only white matter and Multiple Sclerosis (MS) lesion. This white/lesion masked image is then segmented by again applying the authors' stochastic relaxation technique. The process has been applied to multispectral MRI scans of multiple sclerosis patients and the results compare favorably to manual segmentations of the same scans obtained independently by radiology health professionals.

A comparison of manual and automatic methods for registering scans of the head.

This article compares four widely utilized, yet fundamentally different, approaches for registering medical scans of the head. Comparisons are made on the basis of method, accuracy, robustness, computer requirements, and usability. This examination is intended to provide a means for determining an appropriate method for any given application. These approaches are: 1) an iterative method based on the repeated manual selection of 1-2 corresponding points, 2) an approach using the manual selection of 9-15 corresponding points, 3) an automatic surface matching method, and 4) an automatic approach based on voxel similarity. The methods are tested both on simulated data to provide a gold standard of accuracy, and on real data. All registrations are performed in the same visualization environment created for multipurpose image processing. Simulated data tests provided mean transformation errors and time requirements for the different methods, as well as the displacement errors for a set of anatomical landmarks. These results show all of the methods provide good accuracy when the data is not highly distorted and has a large amount of overlap. From the tests using real data both transformations and time requirements are tabulated for comparison. All of the techniques successfully aligned the real data with the exception of surface matching, which failed on the PET-MRI. Each method exhibits strengths and weaknesses that should be understood in order to utilize the most appropriate technique for a given problem. Based on the authors' examination, the voxel-similarity approach proved in general to be the method of choice.

Proton dose monitoring with PET: quantitative studies in Lucite.

The feasibility of using PET for proton dose monitoring is examined here in detail. First experimental studies in a Lucite phantom have been performed at the medical TRIUMF proton beamline for proton energies of 62 MeV and 110 MeV. The proton dose delivered to the phantom ranged from 16 Gy up to 317 Gy. The induced activity was analysed 20-40 min after the irradiation with a PET scanner. The obtained depth activity profiles were compared to our calculation based on a model using available isotope production cross-section data. Both the observed absolute count rates and the activity profiles were found to agree very well with this model. Effects such as proton range straggling, inelastic nuclear interactions and the energy spectrum of the emitted positrons were studied in detail and found to change the activities by 5-10%. The lateral deposition of dose in the phantom could be very well localized by the induced activity. However, the spatial correlation between dose depth profiles and depth activity profiles was found to be poor, hence the extraction of isodose profiles from activity profiles seems to be very difficult.

Distinguishing instrumental and hostile aggression: does it make a difference?

An analogue task of instrumental and hostile aggression during a competitive game, modified to minimize overlap between aggressive responses, was evaluated in 8- to 14-year-old clinically referred boys (n = 33). Postgame interviews indicated that the hostile response, an aversive noise, was perceived by over 80% of subjects as hostile and not instrumental. In contrast, the instrumental response, blocking the opponent's game, was perceived about equally as having instrumental and hostile functions. The hostile aggressive response was uniquely correlated with continuous performance task impulsive commission errors (r = .51), which supported the theoretical relation of hostile aggression to poor impulse control. These results suggest that instrumental and hostile aggression can be distinguished and when precisely defined are distinct in theoretically important ways.

Instrumental and hostile aggression in childhood disruptive behavior disorders.

An analogue task of instrumental and hostile aggression during a competitive game was evaluated in a sample of clinically-referred 8- to 12-year-old aggressive boys. Similar to a prior task in a normative sample (Hoving, Wallace, & La Forme, 1979), both types of aggression increased during provocation as compared to baseline, indicating the success of the provocation manipulation, with moderate correlations between the two aggressive responses. The aggressive group with attention-deficit hyperactivity disorder (ADHD) and the aggressive group without ADHD each had higher rates of instrumental aggression than controls. Only the aggressive/ADHD group had higher rates of hostile aggression than controls. Parent Child Behavior Checklist ratings indicated a modest but significant unique relationship between instrumental aggression and delinquency. The high rate of both types of aggression in the aggressive/ADHD group suggests that comorbid ADHD and aggression may result in qualitative differences in aggressive behavior. The high rate of hostile aggression in the aggressive-ADHD group supports theoretical assumptions regarding the relationship of hostile aggression to poor impulse control.

Assessing parents' willingness to pursue treatment for children with attention-deficit hyperactivity disorder.

OBJECTIVE: This study investigated parents' willingness to pursue treatment for attention-deficit-hyperactivity-disorder (ADHD). METHOD: A self-administered questionnaire (the ADHD Knowledge and Opinion Scale--AKOS) was developed and administered to a sample of 116 families attending an outpatient ADHD clinic. Socioeconomic status, parenting stress, family adaptability and cohesion, degree of child's externalizing behavior, and treatment history were obtained for each family. RESULTS: Parents' willingness to use medication or to pursue counseling were not related to family factors. History of the child receiving medication was mildly correlated with willingness to use medication. History of counseling was mildly correlated with willingness to use medication and to pursue counseling. Mothers who viewed their family as "enmeshed" reported significantly higher sense of competence than those viewing the family as "connected" or "disengaged." CONCLUSION: The AKOS is an instrument that may help clinicians identify and address parents' concerns about treatment for ADHD as well as parents' perceptions about their parenting skills.

School-based assessment of attention deficit-hyperactivity disorder.

Schools are uniquely situated to provide information relevant to the assessment and treatment of Attention Deficit-Hyperactivity Disorder (ADHD) across a variety of tasks, settings, and observers. The importance of the school setting to the assessment and treatment of ADHD has resulted in the development of numerous measures appropriate for such assessment, but few guidelines for their use. The purpose of this article is to describe school-based assessment procedures and their relationship to ADHD. These procedures include teacher rating measures, direct observations in classrooms and on playgrounds, peer rating and sociometric measures, and permanent product measures such as academic performance. It is recommended that school-based assessment of ADHD involve the concurrent use of multiple measures to assess adequately the wide variety of symptoms associated with this disorder. It is further recommended that assessment serve the purpose of determining treatment efficacy to avoid unwarranted preoccupation with diagnostic issues that are as yet unresolved. The components of a comprehensive school-based assessment of ADHD are described, and their relationship to school-based treatment is discussed.

Use of transputers in a 3-D positron emission tomograph.

The use of a VME-bus-based transputer network as a parallel processing engine for positron volume imaging (PVI) is discussed. The authors find that the speedups of parallel networks depend on two major factors, the ratio of computation to communication for a task and the size of the task, and give a simple model to explore the limits on speedups. Through actual implementation it is shown that real-time PVI data acquisition can be achieved with about 20 transputer nodes, and it is estimated that three-dimensional (3-D) image reconstruction can be achieved within 10 min using 200 nodes. Larger images and a larger number of histograms can readily be accommodated using the same parallel algorithms, as the model presented places no limits on the size of the images. The versatility and scalability of transputers makes them very suitable for use in PVI tomographs in that the same transputers can be used for speeding up data acquisition, image reconstruction, and display.

The differential validity of teacher ratings of inattention/overactivity and aggression.

The ability of school-based measures of child behavior to predict differentially the IOWA Conners teacher rating scale Inattention/Overactivity (IO) and Aggression (A) factors was evaluated in a sample of 71 school-aged boys. Multiple measures and multiple methods of assessment were utilized to provide a comprehensive assessment of social and academic behavior. These included direct observations of children in the classroom and on the playground, examination of the organization of children's desks, measures of academic performance, peer nominations of popularity and rejection, and sociometric ratings using the Pupil Evaluation Inventory. Despite moderately high correlations between the teacher rating factors (r = .60), considerable evidence was provided for differential validity on measures of academic performance, peer rating measures, and measures of disruptive or inappropriate classroom and playground behavior. These differences between IO and A factors indicated that the factors were logically independent in important ways, supporting prior work validating separate hyperactivity and aggression dimensions.

Post-traumatic stress in sexually abused, physically abused, and nonabused children.

This investigation compared the rates of post-traumatic stress disorder symptoms across sexually abused, physically abused, and nonabused psychiatrically hospitalized children matched for age, sex, and socioeconomic status. Among the sexually abused children, 20.7% met diagnostic criteria for post-traumatic stress disorder compared with 6.9% of the physically abused and 10.3% of the nonabused children. Although these overall rates were not significantly different across groups, they were significantly high to reinforce the need for further study of post-traumatic stress in childhood. Further, significant symptom rate differences across groups were found with respect to specific post-traumatic stress symptoms. Specifically, sexually abused children exhibited significantly higher rates of inappropriate sexual behaviors than either the physically abused or nonabused children. In addition, both the sexually abused and physically abused groups showed a tendency to exhibit more avoidant/dissociative symptoms as compared to the nonabused children. Results are discussed in terms of their clinical and research implications.