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At least 649 records · Page 36Linked to original sources

PubMed2006

End-user survey for digital sensor characteristics: a pilot questionnaire study.

OBJECTIVE: To survey end-user opinions on dental digital sensor characteristics for the design of a new X-ray imaging sensor. MATERIALS AND METHODS: 100 questionnaires were sent out to dentists and dental radiologists. The questionnaire consisted of six parts related to dental sensors. A: Details about the respondent; B: Prioritization of most important aspects of digital sensors; C: Rating advantages and D: disadvantages of digital sensors; F: Dental features that need to be enhanced by digital sensors; G: End-user comments. RESULTS: Fifty-six questionnaires were returned. Contrast resolution and imaging time were assessed as the most and the least important aspects, respectively. Aspects considered as advantages by approximately 80% of respondents were: optimal contrast resolution, increased specificity, increased discrimination between diseased and healthy tissue, increased sensitivity, lower dose to the patient by more than 20%; as a disadvantage, increased patient dose was given. Dental features considered important by over 80% of the respondents were for intraoral radiographs: the visibility of caries, periapical, periodontal, and bone lesions; for panoramic radiographs: reduction of ghost images, image sharpness and bone. Bone and soft tissues on cephalograms and bone on temporomandibular joint (TMJ) tomograms were mentioned by over 70%. CONCLUSION: The most desired characteristic for a new sensor is contrast resolution. Dose saving is not considered as important unless it is more than 20%. Examination time is not a major issue. Caries, periapical and periodontal, and bone lesions for intraoral radiographs, reduction of ghost images, image sharpness and bone for panoramic radiographs were the most frequently mentioned dental features that should be enhanced by digital sensors.

Artifacts↗

PubMed2001

The National Bladder Cancer Group's experience: invasive and metastatic bladder cancer selected reports.

The National Bladder Cancer Group, a multidisciplinary organization that was originally the therapeutic arm of the National Bladder Cancer Project, reported the results of trials using cisplatin with and without cyclophosphamide in patients with advanced bladder cancer. The objective response rate in both arms was 16% of 109 patients with no difference between the arms. Other studies included cisplatin and irradiation for patients who had comorbid conditions that prevented cystectomy (local response--cT2 11/13 patients; cT3 & cT4 2/4 patients). Seventy patients were treated on the same protocol, and 33 were alive 4 years later. Complete response versus local failure produced 57% versus 11% at 4 years. After cessation of funding, the clinicians at the Massachusetts General Hospital agreed to follow a potentially bladder-sparing multimodality protocol, which stipulated that visible tumor be resected following which the patient received methotrexate, vinblastine and cisplatin (MCV), small-volume irradiation, and more cisplatin with midcourse cystectomy if local tumor persisted. Overall survival was 45%. The Radiation Therapy Oncology Group conducted a similar study omitting MCV from one arm. The 5-year survival rate was 38% with no advantage for either arm.

Humans↗

PubMed1999

Evaluation of radiofrequency pulses and contrast agent doses for use in 3D pulmonary magnetic resonance angiography.

Ten healthy volunteers were imaged with breath-hold, three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) using single-variable-angle uniform signal excitation (VUSE), double-VUSE, and flat radiofrequency (RF) pulses with various doses of contrast agent. The ability of each technique to display pulmonary vasculature was evaluated. Images were segmented to isolate lungs, and maximum intensity projections (MIPs) were computed. All MIPs were assigned an image quality (IQ) rating, and signal-to-noise ratios (SNRs) were measured in pulmonary vessels. Without contrast agent, subsegmental vessels were displayed in single- and double-VUSE images while no vessels were visible in flat images. With equal doses of contrast agent, SNRs and IQ ratings were comparable for images obtained with VUSE and flat pulses. In addition, single-VUSE pulses produced more uniform signal from vessels than flat pulses in contrast-enhanced images. The results indicate that non-contrast-enhanced 3D TOF pulmonary MRA with VUSE RF pulses may be a useful screening tool. In addition, contrast-enhanced 3D TOF MRA with VUSE pulses may be useful as a stand-alone technique for assessing the pulmonary vasculature or as an adjunct to contrast-enhanced 3D TOF MRA with flat pulses. J. Magn. Reson. Imaging 10:929-938, 1999.

Adult↗

PubMed1991

Analysis of texture in macroradiographs of osteoarthritic knees using the fractal signature.

Texture of regions of macroradiographs (x5) of six normal and five osteoarthritic knee joints, taken on a high resolution microfocal x-ray unit, are examined using mathematical morphology. Radiographs of bones are two-dimensional projections of attenuation coefficient through the three-dimensional (3D) joint structure. Visible texture represents the summation of the attenuation from numerous thin plates of bone. Where there is no organization in the trabeculae, resultant radiographs approximate a fractal surface. Varying structuring element size in mathematical morphology allows estimation of fractal dimension over a range of resolution. Variation of fractal dimension with resolution, the fractal signature, indicates how images deviate from fractal surfaces. By correct choice of structuring element, a texture analysis method using the fractal signature has been developed, tolerant to changes in image acquisition and digitization. Texture in regions of radiographs of normal tibia approximates a fractal surface with dimension 2.8 as does vertical structure in arthritic patients. In osteoarthritic knee joints, horizontal tibial trabeculae thicken. Horizontal structure in the tibia on radiographs of arthritic patients deviates from the fractal model. This is indicated by peaks in the fractal signature whose height and position match a visual assessment of the degree of arthritic change.

Humans↗

PubMed1994

Shaping and positioning the nasal tip without structural disruption: a new, systematic approach.

This paper presents a new, comprehensive, and systematic approach to analysis, planning, and techniques of primary nasal tip rhinoplasty, emphasizing techniques that limit uncontrollable variables before proceeding to techniques which increase uncontrollable variables and risk secondary deformity, including (1) maintenance of structural integrity of the alar rim strips, limiting use of scoring or morselization techniques which reduce support and introduce potential secondary deformities, (2) shaping and positioning the lateral and medial crura in a reversible, nondestructive manner using permanent suture and nonvisible control graft techniques, (3) minimizing uncontrollable postoperative variables by decreasing the need for visible grafts to shape the tip complex in primary rhinoplasty, achieving the same results with existing alar structural elements, (4) integrating these concepts with specific sequences of surgical techniques--bilateral alar arch components individually positioned, then shaped and unified for symmetry, and finally positioned for rotation and projection--and (5) introducing an integrated set of surgical techniques and sequencing of tip surgery to achieve the objectives listed above in most primary and some secondary rhinoplasties. The concepts and techniques of this approach are based on the principle that preservation of structural integrity of alar complex elements (medial and lateral crural arch elements) preserves support and reduces the incidence of secondary deformities (kinking, buckling, discontinuity) that can result from shaping techniques which disrupt that integrity. If shaping and positioning of the tip can be achieved with reversible, nondestructive techniques, the need for placement of visible grafts (with their additional variables) is greatly reduced. Shaping and positioning can be performed incrementally and reversibly without jeopardizing structural integrity and support in the surgical process. Ten fresh cadaver dissections were utilized in the development of the surgical techniques. A total of 233 rhinoplasties (220 primary and 13 secondary) with 1 to 9 years of follow-up have been performed using this approach. Only two secondary procedures for tip deformity have been performed.

Cadaver↗

PubMed2003

Anatomy and frequency of large pontomesencephalic veins on 3D CT angiograms of the circle of Willis.

BACKGROUND AND PURPOSE: The pontomesencephalic veins (PMVs), especially the anterior PMV, are sometimes large enough that they could potentially affect the interpretation of CT angiograms of the circle of Willis. We investigated the frequency and anatomy of visible PMVs on 3D CT angiograms. METHODS: CT angiograms of 211 consecutive patients who underwent CT angiography for a variety of clinical indications were evaluated retrospectively. Images evaluated by consensus between two neuroradiologists were maximum intensity projection and volume-rendered 3D CT angaiograms. RESULTS: Visible PMVs were present on 3D CT angiograms in 11 (5.2%) of 211 patients. Eight of 11 patients had a visible anterior PMV behind the basilar artery. In four patients, the venous caliber of the anterior PMV was sufficiently large enough to be potentially confused with arterial structures. In one patient, 3D CT angiography revealed a large anterior PMV (approximately 2.6 mm in diameter) in the interpeduncular cistern, which had been mistaken for subarachnoid hemorrhage on a nonenhanced CT scan. Two patients had interpeduncular veins of the anterior PMV draping over the dome of a basilar tip aneurysm. In only one patient was the anterior PMV visible possibly owing to arteriovenous malformation. One patient had visible lateral mesencephalic veins, and four patients had visible transverse pontine veins. In one case, on certain views, the transverse pontine veins appeared to arise from the basilar artery. CONCLUSION: Because of their small size, PMVs were seen only infrequently on 3D CT angiograms, but neuroradiologists should be familiar with the normal variants of large PMVs to avoid diagnostic and anatomic confusion.

Artifacts↗

PubMed1993

Classification in slipped capital femoral epiphysis. Sonographic assessment of stability and remodeling.

In a prospective study of 26 hips in 21 patients with slipped capital femoral epiphyses (SCFEs), serial sonography was more sensitive than radiography in showing epiphyseal displacement and reduction. Reductions were associated with grossly visible hip joint effusions. The initial slips were reduced by treatment in seven of 11 hips with effusion. The 15 hips without effusion were unreduced. After stabilization and pinning, the effusion did not recur in any case. Sonography is sensitive and free from projectional errors in the assessment of metaphyseal remodeling. If any remodeling is present, the SCFE is at least three weeks in duration. A new classification into acute, acute-on-chronic, and chronic SCFEs is proposed, based on the objective sonographic data. Joint effusion represents physeal instability or recent progression, and remodeling is a sign of chronicity. An acute SCFE is characterized by effusion, whereas a slip without effusion but with remodeling is designated as chronic. An acute-on-chronic SCFE is associated with both effusion and remodeling. Joint effusion suggests that SCFEs should be operatively fixed and that displacement may diminish with traction or intraoperative positioning of the hip.

Adolescent↗

PubMed2000

3D reconstruction method from biplanar radiography using non-stereocorresponding points and elastic deformable meshes.

Standard 3D reconstruction of bones using stereoradiography is limited by the number of anatomical landmarks visible in more than one projection. The proposed technique enables the 3D reconstruction of additional landmarks that can be identified in only one of the radiographs. The principle of this method is the deformation of an elastic object that respects stereocorresponding and non-stereocorresponding observations available in different projections. This technique is based on the principle that any non-stereocorresponding point belongs to a line joining the X-ray source and the projection of the point in one view. The aim is to determine the 3D position of these points on their line of projection when submitted to geometrical and topological constraints. This technique is used to obtain the 3D geometry of 18 cadaveric upper cervical vertebrae. The reconstructed geometry obtained is compared with direct measurements using a magnetic digitiser. The order of precision determined with the point-to-surface distance between the reconstruction obtained with that technique and reference measurements is about 1 mm, depending on the vertebrae studied. Comparison results indicate that the obtained reconstruction is close to the actual vertebral geometry. This method can therefore be proposed to obtain the 3D geometry of vertebrae.

Cervical Vertebrae↗

PubMed2006

[Correction of ear malformations with autologous rib cartilage].

INTRODUCTION: Ear malformations are mainly isolated deformations but exist also in combination with various syndromes. A visible malformation in cases of microtia is a problem for the entire family. Auricular reconstruction with autologous cartilage has been well established in the last decade. Optimization of the technique has led to improved and reliable results. OPERATION AND RESULTS: Based on the experience of 120 cases we developed a concept that allows total ear reconstruction in two operative steps. In the first operation autologous rib cartilage is harvested and a natural framework is created following the template from the opposite ear. The ear remnant is transposed and the framework placed in a subcutaneous pocket on the mastoid plane. After a healing period of around 6 weeks the second operation reconstructs the auricular projection and the retroauricular fold. CONCLUSION: Based on an individualized surgical treatment, auricular reconstruction with autologous rib cartilage are possible from the age of around 8 to the advanced period of life with reproducibly good results.

Adolescent↗

PubMed1978

A biomechanical invariant for gait perception.

Viewers can determine the gender of a walker from sagitally projected, dynamic displays of point-lights attached to prominent joints. This article explores three interrelated approaches in search of a biomechanical invariant that viewers might use. The first, an index of torso structure, accounts for the data handsomely but seems inappropriate because it is not directly revealed in the dynamic stimuli. The second, a dynamic index of visible torsion in the trunk of a walker, also fits the data well but seems to have a logical problem and a difficulty in accounting for performance in certain conditions of several previous studies. The third has the strengths of the first two indices, and it can account for some other data as well. It is the center of moment and is a "deeper", more general description of the invariant. This center is a point around which all movement occurs. It can be thought of as one specification of the gestalt law of common fate and may be helpful for the study of movement perception in general.

Biomechanical Phenomena↗

PubMed2001

Variations of the basal vein: identification using three-dimensional CT angiography.

BACKGROUND AND PURPOSE: The basal vein of Rosenthal (BVR) presents with many variations because of its origin in the secondary longitudinal anastomoses between embryonic veins. The variations were evaluated by 3D CT angiography imaging. METHODS: Three-dimensional CT angiograms in the axial stereoscopic view and other directions constructed by the voxel transmission method and maximum intensity projection (MIP) images were obtained in 500 sides of 250 patients. RESULTS: The BVR flowed into the great vein of Galen in 87.8%, but the anastomoses between the first and second segments were not confirmed in 36.9% of this type. The first segments with hypoplastic or aplastic anastomoses flowed into the cavernous sinus or the sphenoparietal sinus. Therefore, typical BVRs with these anastomoses accounted only for 55.4% of all sides. More than one fourth of the typical type also entered the anterior veins such as the cavernous sinus. Drainage was to the lateral mesencephalic vein in 5.6%, peduncular vein in 1.6%, and lateral or medial tentorial sinus in 5.0%. CONCLUSION: Variations of the BVR can be classified on the basis of the five drainage pathways formed during the early embryonic stage. Three-dimensional CT angiography can show the stereoscopic anatomy and the main drainage routes, but not hypoplastic veins, which are only visible on MIP images.

Adult↗

PubMed2005

Low-dose megavoltage cone-beam CT for radiation therapy.

PURPOSE: The objective of this work was to demonstrate the feasibility of acquiring low-exposure megavoltage cone-beam CT (MV CBCT) three-dimensional (3D) image data of sufficient quality to register the CBCT images to kilovoltage planning CT images for patient alignment and dose verification purposes. METHODS AND MATERIALS: A standard clinical 6-MV Primus linear accelerator, operating in arc therapy mode, and an amorphous-silicon (a-Si) flat-panel electronic portal-imaging device (EPID) were employed. The dose-pulse rate of 6-MV Primus accelerator beam was windowed to expose an a-Si flat panel by using only 0.02 to 0.08 monitor unit (MUs) per image. A triggered image-acquisition mode was designed to produce a high signal-to-noise ratio without pulsing artifacts. Several data sets were acquired for an anthropomorphic head phantom and frozen sheep and pig cadaver head, as well as for a head-and-neck cancer patient on intensity-modulated radiotherapy (IMRT). For each CBCT image, a set of 90 to 180 projection images incremented by 1 degree to 2 degrees was acquired. The two-dimensional (2D) projection images were then synthesized into a 3D image by use of cone-beam CT reconstruction. The resulting MV CBCT image set was used to visualize the 3D bony anatomy and some soft-tissue details. The 3D image registration with the kV planning CT was performed either automatically by application of a maximization of mutual information (MMI) algorithm or manually by aligning multiple 1D slices. RESULTS: Low-noise 3D MV CBCT images without pulsing artifacts were acquired with a total delivered dose that ranged from 5 to 15 cGy. Acquisition times, including image readout, were on the order of 90 seconds for 180 projection images taken through a continuous gantry rotation of 180 degrees. The processing time of the data required an additional 90 seconds for the reconstruction of a 256(3) cube with 1.0-mm voxel size. Implanted gold markers (1 mm x 3 mm) were easily visible or all exposure levels without artifacts. In general, the presence of high Z materials such as tooth fillings or implanted markers did not result in visible streak artifacts. The registration of structures such as the spinal canal and the nasopharynx in the MV CBCT and kV CT data sets was possible with millimeter and degree accuracy as assessed by displacement simulations and subsequent visual evaluation. CONCLUSIONS: We believe that the quality of these images, along with the rapid acquisition and reconstruction times, demonstrates that MV CBCT performed by use of a standard linear accelerator equipped with a flat-panel imager can be applied clinically for patient alignment.

Animals↗

PubMed1992

Computer assisted localizer for planning of surgery and intra-operative orientation.

There is discrepancy between the exact representation of anatomical structures and tumours in the CT or MRI scan and the more or less accurate intra-operative localisation methods based mostly upon landmarks of the skull and extracerebral space and visible abnormalities of the cerebral surface. To overcome these problems of exact intra-operative localisation a Computer Assisted Localizer (CAL) is presented which allows precise intra-operative orientation without these aids. It consists of a mechanically articulated arm with six degrees of freedom with a high precision digital incremental and an image processor for 3 D data of the head. MRI and/or CT investigation is done pre-operatively with four reference markers fixed on the patient's head. They are visible on the CT or MRI slices and are used as reference points during surgery for adjustment of the device. The co-ordinates of the digitalizer arm tip are projected into the corresponding axial, sagittal and coronal CT slices so that the system simultaneously presents three orthogonal multiplanar CT reconstructions with a reticule indicating the position of the tip of the arm. As the surgeon directs the arm to the region of interest the corresponding CT slices are displayed on the monitor at a rate of 20 slices/sec determined by the motion of the arm. The accuracy of measurement of the device itself lies within 1 mm. The accuracy is somewhat reduced however by the thickness of CT or MRI slices (routinely 2 mm slices were taken) and by deviations of the reference markers on the skin surface which amount up to 3 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1997

Subcortical aphasia.

We critically review the literature on subcortical aphasia, suggest that a number of traditional concepts regarding mechanisms of aphasia are inconsistent with now abundant data, and propose several new hypotheses. The absence of aphasia in 17 reported cases of dominant hemisphere striatocapsular infarction and the finding of nearly every conceivable pattern of language impairment in 33 different reported cases of striatocapsular infarction provide strong evidence against a major direct role of the basal ganglia in language and against disconnection or diaschisis as mechanisms of nonthalamic subcortical aphasia. However, detailed consideration of the vascular events leading to striatocapsular infarction strongly suggests that associated linguistic deficits are predominantly related to sustained cortical hypoperfusion and infarction not visible on structural imaging studies. Thalamic disconnection, as may occur with striatocapsular infarcts with extension to the temporal stem and putamenal hemorrhages, may also contribute to the language deficits in some patients. Review of the literature on thalamic infarction, in conjunction with previously unreported anatomic details of four cases, suggests that what infarcts in the tuberothalamic artery territory and the occasional infarcts in the paramedian artery territory associated with aphasia have in common is damage to the frontal lobe-inferior thalamic peduncle-nucleus reticularis-center median system that may be involved in regulating the thalamic gate in attentional processes. Disruption of attentional gating in the pulvinar and lateral posterior nuclei resulting from such lesions may impair selection of specific neuronal networks in the projection field of these nuclei that serve as the substrate for lexical-semantic function, which is in effect a disruption of a type of working memory, as defined by Goldman-Rakic. We define this as a defect of selective engagement.

Aphasia, Wernicke↗

PubMed2005

Politicizing dominant discursive constructions about teenage pregnancy: re-locating the subject as social.

Authors of research examining the issue of teenage pregnancy represent authoritative social voices, in strong positions of warrant that participate in shaping dominant social attitudes towards the subject. Their research projects are used to develop policies, information, service provision and practices that are major forces in shaping the actual experience of being pregnant as a teenager. This article examines local examples of such research and locates interpretation of these alongside other international studies. Prevalent in the research is the taken for granted assumption that pregnancy in adolescence is undesirable, and that research knowledge can, and should be, applied to reduce rates of teenage pregnancy. Despite clear indications of social issues being a major source of negative impacts of being pregnant in adolescence, the dominant theme is of teenage pregnancy as an individual health or behavioural problem in need of a psychological solution. This article would like to draw attention to and make visible the contingent, political and potentially problematic nature of those constructions. The suggestion is made that future work could benefit from genuine attention to: 1) social issues, especially in relation to resources and access; 2) work that explores meanings around pregnancy for young people, and 3) the application of politically engaged reflexivity in research.

Adolescent↗

PubMedDate not supplied

The Michigan Clinical Research Collaboratory: following the NIH Roadmap to the community.

PURPOSE: This case study describes a successful National Institutes of Health (NIH) Roadmap application that has created a new and innovative translational science partnership at the University of Michigan. METHODS: We describe the institution within which the grant application was developed, the role played by the Department of Family Medicine, the role of prior successes in translational and community-based research, the associated infrastructure development, the application development process, and some features of the final project. RESULTS: A partnership among 2 clinical and research centers of excellence at the University of Michigan, 3 practice-based research networks, and a clinical research center was created as the platform to support an NIH Roadmap. The result was a funded 3.3 million dollar, 3-year project supporting the creation of the Michigan Clinical Research Collaboratory (MCRC), a research infrastructure that will support the design, conduct, and dissemination of community-based clinical translation research. The MCRC depends to a considerable degree on the experience, expertise, and infrastructure in community-based translational research of the Department of Family Medicine. CONCLUSIONS: The successful funding of the MCRC grant will support influential translational research programs of high impact and visibility that would not otherwise have occurred. The MCRC grant is an acknowledgment of the important research to be done in the community, the critical nature of infrastructure investment and prior work in competing successfully for such funding, and the personnel and information technology investments required for success. Collaboration between practice-based family medicine investigators and traditional clinical investigators at the University of Michigan has led to successful competition for an NIH Roadmap grant, which has led in turn to greater institutional recognition for the importance and legitimacy of community-based translational research.

Academic Medical Centers↗

PubMed1990

Anatomical study of the temporal lobe. Correlations with nuclear magnetic resonance.

Following a brief review of embryogenesis and phylogenesis, the different anatomical structures of the temporal lobe of the brain are described. This lobe has 4 surfaces: lateral, inferomedial, superomedial and superior. The first 2 surfaces, visible on the lateral and inferior aspects of the cerebral hemisphere, are composed of 5 temporal gyri. The superomedial and superior surfaces do not show and must be made visible by a digital or instrumental manipulation. The hippocampal formation, surrounded by the temporal horn of the lateral ventricle medially, the choroid and transverse fissures laterally and the amygdaloid complex anteriorly, forms the superomedial surface and represents the "rhincendephalic" part of the temporal lobe. The superolateral surface, which is the superior surface of the first temporal gyrus, is buried deeply in the fissure of Sylvius and is divided into 3 parts: the planum polare, the gyri of Heschl and the planum temporale. Two categories of fibres are present in the white matter of the temporal lobe: projection fibres (acoustic radiation, optic radiation, temporo-pontine tract, temporo-thalamic fasciculus) and association fibres (cingulum, anterior longitudinal, uncinate, superior occipitofrontal, superior longitudinal fasciculi). The anatomical temporal lobe exploration by MRI was carried out with inversion-recovery sequences performed in all three dimensions. The authors describe the advantages and limitations of MRI and indicate the most appropriate plane(s) for the study of the various temporal structures, with emphasis on coronal on coronal and sagittal sections.

Adult↗

PubMed1999

Exocentric pointing in three-dimensional space.

A study is reported of an exocentric pointing task in all three dimensions, in near space, with only two visible luminous objects--a pointer and a target. The task of the subject was to aim a pointer at a target. The results clearly show that visual space is not isotropic, since every set direction appeared to consist of two independent components--one in the projection onto a frontoparallel plane (tilt), the other in depth (slant). The tilt component shows a general trend across subjects, an oblique effect, and can be judged monocularly. The slant component is symmetrical in the mid-sagittal plane, requires the use of binocular information, and shows considerable differences between subjects. These differences seem to depend on the amount of binocular information used by each subject. There was a remarkably high level of consistency in the exocentric pointing, despite the absence of environmental cues. The within-subject consistency in the settings of the pointer corresponds to a consistency of about 1 min of arc in disparity of its tip, even though the pointer and target are separated by more than 5 deg.

Adolescent↗