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At least 361 records · Page 20Linked to original sources
PubMed2001

Polyurethane real-size models used in planning complex spinal surgery.

STUDY DESIGN: The application of polyurethane real-size models for planning and performing complex spinal surgery is described. OBJECTIVE: To determine the feasibility of using polyurethane real-size models to plan osteotomies, resections, and designs of custom-made spinal implants in complex spinal surgery. SUMMARY OF BACKGROUND DATA: In selected patients with complex spinal pathology, exact planning of the surgical procedure is not possible using current imaging methods. In these cases, real-size spinal models would be desirable to enhance pre- and perioperative planning by visual and tactile feedback, and to improve the production of custom-made spinal implants. METHODS: A real-size spinal model of six patients was produced from hardened polyurethane foam on the basis of data from contiguous computer tomography slices. In two patients, the models were used to plan correction osteotomies and resections, with the assistance of image-guided surgery in one of the patients. In four patients, the models were used to plan tumor resections and to produce custom-made spinal implants. RESULTS: In all the patients, the surgical procedure could be performed exactly according to the preplanned intervention. The polyurethane real-size models provided essential and additional information by direct visual and tactile feedback. They allowed in vitro testing of custom-made spinal implants with a perfect fit. CONCLUSIONS: Real-size spinal models made from polyurethane foam can be used to provide excellent understanding of the complex spinal pathology in highly selected patients. These models allow complex spinal surgery with a more predictable outcome.

Adolescent↗
PubMed2000

Electrical impedance tomography (EIT) in applications related to lung and ventilation: a review of experimental and clinical activities.

This review article is a summary of the publications dealing with the pulmonary applications of electrical impedance tomography (EIT). Original papers on EIT lung imaging published over 15 years are analysed and several aspects of the performed EIT measurements summarized. Information on the type of the EIT device and electrodes used, the studied transverse thoracic planes, the data acquisition rate, the number of studied animals, normal subjects or patients, the kind of lung pathology, the performed ventilatory manoeuvres and other interventions, as well as the applied reference techniques, is given. The type of the generated pulmonary EIT images and the quantitative analysis of the EIT data are described. Finally, the major results achieved are presented, followed by an analysis of the perspectives of EIT in clinical applications. A comparative analysis of the EIT hardware and the quality of the evaluation tools was not performed.

Animals↗
PubMed2006

High-level virtual reality simulator for endourologic procedures of lower urinary tract.

OBJECTIVES: To analyze the limitations of existing simulators for urologic techniques, and then test and evaluate a novel virtual reality (VR) simulator for endourologic procedures of the lower urinary tract. Surgical simulation using VR has the potential to have a tremendous impact on surgical training, testing, and certification. Endourologic procedures seem to be an ideal target for VR systems. METHODS: The URO-Trainer features genuine VR, obtained from digital video footage of more than 400 endourologic diagnostic and therapeutic procedures, as well as data from cross-sectional imaging. The software offers infinite random variations of the anatomy and pathologic features for diagnosis and surgical intervention. An advanced haptic force feedback is incorporated. Virtual cystoscopy and resection of bladder tumors were evaluated by 24 medical students and 12 residents at our department. RESULTS: The system was assessed by more than 150 international urologists with varying experience at different conventions and workshops from March 2003 to September 2004. Because of these evaluations and constant evolutions, the final version provides a genuine representation of endourologic procedures. Objective data are generated by a tutoring system that has documented evident teaching benefits for medical students and residents in cystoscopy and treatment of bladder tumors. CONCLUSIONS: The URO-Trainer represents the latest generation of endoscopy simulators. Authentic visual and haptic sensations, unlimited virtual cases, and an intelligent tutoring system make this modular system an important improvement in computer-based training and quality control in urology.

Computer Simulation↗
PubMed2001

A general framework for the fusion of anatomical and functional medical images.

The collection of various data coming from anatomical and functional imagery is becoming very common for the study of a given pathology, and their aggregation generally allows for a better medical decision in clinical studies. A fusion process is described in this article for the modeling of this aggregation. The process is illustrated in the case of anatomical and functional images of the brain, but the general principle may be extended to other organs. The whole three-step fusion process based on possibilistic logic is detailed and a new class of fusion operator is introduced. The use of fuzziness in the process in general and in the operator in particular allows for the management of uncertainty and imprecision inherent to the images. The fusion process is illustrated in two clinical cases: the study of Alzheimer's disease by MR/SPECT fusion and the study of epilepsy by MR/SPECT/PET fusion. Results are presented and evaluated, and a preliminary clinical validation is achieved. The assessment of the method is encouraging, allowing its application on several clinical problems.

Adult↗
PubMed2000

Quantitative gadopentetate-enhanced MRI of breast tumors: testing of different analytic methods.

This study assessed several proposed imaging strategies and analytic methods based on gadopentetate-enhanced MRI to differentiate benign from malignant breast tumors in a blinded experimental animal study. Steady-state dynamic MRI and first-pass imaging, performed with either T(1)- or T*(2)- weighted sequences, were compared. Semiquantitative and quantitative analysis methods, based on empirical measures of the data or physiological models, were subsequently applied to the imaging datasets. Comparative measures provided pathologic distinction of benign from malignant tumors, tumor grading, and histologic determination of microvascular density. Of the eight tested methods, only one, an estimate of first-pass perfusion using T *(2)-weighted imaging, showed an almost significant (P = 0.05) difference between benign and malignant tumors and correlated almost significantly (r =.3, P = 0.06) with the tumor grade. All other tests, performed either with steady-state imaging or with T(1)-weighted first-pass imaging, failed to differentiate benign from malignant tumors. In addition, they yielded poor correlations with tumor grade and microvascular density.

Alkylating Agents↗
PubMed1994

Localized brain proton NMR spectroscopy in young adult phenylketonuria patients.

Localized proton magnetic resonance spectroscopy with short echo time (TE = 20 ms) was used to investigate biochemical changes in the cerebral white matter of 20 young adult patients (median 19 years) with phenylketonuria (PKU). Results were compared with those of a group of 12 age-matched healthy volunteers (median 25 years). Concentrations of N-acetyl-aspartate (NAA) and choline (Cho) relative to creatine (Cr) were unchanged. However, concentrations of inositol (Ins) relative to creatine were found to be significantly lower (P < 0.001) in the PKU patients (0.30 +/- 0.09 versus 0.57 +/- 0.17). Individual inositol concentrations did not correlate with age, diet, serum phenylalanine (Phe) levels or extent of pathological regions in the T2-weighted images. The lack of correlation with individual data suggests that the decreased inositol concentration could be related to a metabolic deficiency during fetal development. No signal from the phenyl ring protons of phenylalanine was detected in the PKU patients (phenylalanine serum concentration < or = 1.27 mM), which suggests that concentration of phenylalanine may be lower in brain than in serum.

Adolescent↗
PubMed1999

MRI of three siblings with Sjögren-Larsson syndrome.

Sjögren-Larsson syndrome (SLS) is a rare disorder with autosomal recessive inheritance. Its clinical, pathological, genetic, and biochemical manifestations have been thoroughly evaluated, but there is little imaging data, especially regarding MRI. We present brain MRI of three siblings with SLS and discuss our findings.

Brain↗
PubMed2005

Value of high spatial and high temporal resolution magnetic resonance angiography for differentiation between idiopathic and thromboembolic pulmonary hypertension: initial results.

Differentiation between different forms of pulmonary hypertension (PH) is essential for correct disease management. The goal of this study was to elucidate the clinical impact of high spatial resolution MR angiography (SR-MRA) and time-resolved MRA (TR-MRA) to differentiate between patients with chronic thromboembolic PH (CTEPH) and idiopathic pulmonary arterial hypertension (IPAH). Ten PH patients and five volunteers were examined. Twenty TR-MRA data sets (TA 1.5 s) and SR-MRA (TA 23 s) were acquired. TR-MRA data sets were subtracted as angiography and perfusion images. Evaluation comprised analysis of vascular pathologies on a segmental basis, detection of perfusion defects, and bronchial arteries by two readers in consensus. Technical evaluation comprised evaluation of image quality, signal-to-noise ratio (SNR) measurements, and contrast-media passage time. Visualization of the pulmonary arteries was possible down to a subsegmental (SR-MRA) and to a segmental (TR-MRA) level. SR-MRA outperformed TR-MRA in direct visualization of intravascular changes. Patients with IPAH predominantly showed tortuous pulmonary arteries while in CTEPH wall irregularities and abnormal proximal-to-distal tapering was found. Perfusion images showed a diffuse pattern in IPAH and focal defects in CTEPH. TR-MRA and SR-MRA resulted in the same final diagnosis. Both MRA techniques allowed for differentiation between IPAH and CTEPH. Therefore, TR-MRA can be used in the clinical setting, especially in dyspneic patients.

Diagnosis, Differential↗
PubMed1995

Ethical issues in the application of virtual reality to medicine.

Virtual reality (VR) will be increasingly used as a research tool in medicine. Examples include the computer modelling of complex pathological regulatory systems in disease; the integration of massive data bases derived from structural imaging of diseased organs and simultaneous functional mapping of the same organ; the development of neural prosthetic devices in sensory and/or mental impairment and the assessment or modification of major behavioural abnormalities in selected individuals. In time, advances in VR will lead to increasing pressure to introduce patients to a virtual reality environment and it is here that ethical problems will most frequently be encountered. Early examples would include the monitoring of anaesthesia and intensive care procedures but may extend to the support and enrichment of life of those patients who suffer chronic disabilities. In the setting of virtual reality, they may be able to experience much improved educational, recreational or pleasurable pursuits. Whilst the ultimate goal of improvement of the human condition will be cited to justify any human costs encountered in the development, testing and introduction of VR machines to patient care, pertinent ethical problems must simultaneously be addressed. These include the possibility that some researchers place their own advancement above the interests of a particular patient. Some other researchers may be unduly paternalistic especially when making decisions about patients who because of mental impairment or illness are unable to give their informed consent. Potentially, VR machines may be prone to errors such that they introduce into the mental life of susceptible individuals specific distortions that serve to exacerbate the symptoms of mental illness or induce such symptoms when none were previously present.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral Research↗
PubMed2004

Outcomes for patients with an aortopulmonary window, and the impact of associated cardiovascular lesions.

An aortopulmonary window is a communication between the ascending aorta and pulmonary trunk in the presence of two separate arterial valves, and is often complicated by other associated defects. We sought to determine management and related outcomes in patients with this malformation. We identified those patients presenting between 1969 and 1999 from the databases held in our Departments of Cardiology, Pathology and Cardiovascular Surgery. We obtained data relating to issues concerning demography, clinical findings, imaging, management and outcome. The median age at presentation for the 42 patients identified, of whom 23 were female, was 62 days, with a range from birth to 6 years. Associated cardiac defects were present in 34 patients, including interruption of the aortic arch in 6 patients. The correct diagnosis was initially missed in 13 patients. Of the patients, six died without surgical repair, and 1 patient was lost-to-follow-up. Repair was performed in 35 patients, subsequent to repair of other defects in 4, in association with repair of other defects in 17, of whom 3 died, and as an isolated procedure in 14 patients, one of the latter being treated by transcatheter closure. Overall, there were 9 deaths, all in patients with complex associated defects, except 1 patient with a missed aortopulmonary window after repair of aortic coarctation. Kaplan-Meier estimates of survival were 81% at 3 months until 11.5 years, and 69% up to 21 years. Only the presence of interrupted aortic arch was independently associated with increased time-related mortality, the hazard ratio being 5.87 (p = 0.009). The outcome for an isolated lesion is excellent. Mortality occurs mainly before repair, mostly with complex associated lesions, particularly interruption of the aortic arch.

Aorta↗
PubMed1999

Ethnic differences in incidence of stroke: prospective study with stroke register.

OBJECTIVE: To identify ethnic differences in the incidence of first ever stroke. DESIGN: A prospective community stroke register (1995-6) with multiple notification sources. Pathological classification of stroke in all cases was based on brain imaging or necropsy data. Rates were standardised to European and world populations and adjusted for age, sex, and social class in multivariate analysis. SETTING: A multi-ethnic population of 234 533 in south London, of whom 21% are black. RESULTS: 612 strokes were registered. The crude annual incidence rate was 1.3 strokes per 1000 population per year (95% confidence interval 1.20 to 1.41) and 1.25 per 1000 population per year (1.15 to 1.35) age adjusted to the standard European population. Incidence rates adjusted for age and sex were significantly higher in black compared with white people (P<0.0001), with an incidence rate ratio of 2.21 (1.77 to 2.76). In multivariable analysis increasing age (P<0.0001), male sex (P<0.003), black ethnic group (P<0.0001), and lower social class (P<0.0001) in people aged 35-64 were independently associated with an increased incidence of stroke. CONCLUSIONS: Incidence rates of stroke are higher in the black population; this is not explained by confounders such as social class, age, and sex. Ethnic differences in genetic, physiological, and behavioural risk factors for stroke require further elucidation to aid development of effective strategies for stroke prevention in multi-ethnic communities.

Adolescent↗
PubMed2005

Autofluorescence characteristics of normal foveas and reconstruction of foveal autofluorescence from limited data subsets.

PURPOSE: To develop mathematical and geometric models of the nonuniform autofluorescence (AF) patterns of foveas of normal subjects and to reconstruct these models from limited subsets of data. METHODS: Confocal scanning laser ophthalmoscope (cSLO) AF fundus images of normal maculae were obtained from both eyes of 10 middle-aged subjects. They were filtered and contrast enhanced, to obtain elliptical isobars of equal gray levels (GLs) and determine the isobars' resolutions, eccentricities, and angles of orientation. The original image data were fit with a mathematical model of elliptic quadratic polynomials in two equal zones: the center and the remaining annulus. RESULTS: The AF images segmented into nested concentric GL isobars with GLs that increased radially from the least-fluorescent center. The mean isobar resolution was 31 +/- 7 mum. The geometric eccentricity of the ellipses increased from 0.42 +/- 0.12 centrally to 0.52 +/- 0.14 peripherally (P = 0.0005), with mean axes of orientation peripherally 97.12 +/- 15.46 degrees . The model fits to the complete image data had mean absolute normalized errors ranging from 3.6% +/- 3.7% to 7.3% +/- 7.1%. The model fits to small subsets (1% to 2% of total image data) had mean absolute errors ranging from 3.7% +/- 3.8% to 7.3% +/- 7.2%. CONCLUSIONS: Normal AF fundus images show finely resolved, concentric, elliptical foveal patterns consistent with the anatomic distribution of fluorescent lipofuscin, light-attenuating macular pigment (MP), cone photopigment, and retinal pigment epithelial (RPE) pigment in the fovea. A two-zone, elliptic, quadratic polynomial model can accurately model foveal data. This model may be useful for image analysis and for automated segmentation of pathology.

Adult↗
PubMed1994

Development of the bi-directional ultrasound system for base of tongue imaging.

The use of conventional ultrasound systems to image the upper airway has been limited because ultrasound energy is attenuated by the air column. In an attempt to study upper airway geometry, we developed a computer controlled bi-directional ultrasound system which combines two conventional ultrasound devices with computer image processing to yield images of upper airway structures. Human studies and cadaver studies were performed to evaluate the system. Images acquired by the bi-directional ultrasound system were comparable to images from 3D volume rendered CT scans. This system may provide valuable data in the study of upper airway physiology and pathology.

Calibration↗
PubMed1994

Value of volume weighted mean nuclear volume in grading and prognosis of renal cell carcinoma.

AIMS: To perform stereological quantitation of volume weighted mean nuclear volume in renal cell carcinomas; and to correlate the data obtained with recognised clinical and pathological variables and determine their prognostic value. METHODS: The point-sampled intercepts method was used to estimate mean nuclear volume in 63 cases of clear cell renal carcinoma diagnosed between 1980 and 1988. New paraffin wax embedded histological sections were analysed after systematic sampling and the test systems superimposed on a projected microscopic image to measure nuclear intercept lengths. After mathematical estimation of mean nuclear volume, statistical analyses of the data in relation to clinical and pathological variables as well as the prognostic impact were investigated. RESULTS: The mean nuclear volume was significantly associated with tumour dedifferentiation. However, mean nuclear volume showed no statistical differences with sex, age, and clinical stage. The prognostic value of mean nuclear volume, nuclear grading, and clinical stage in renal cell carcinomas was high: mean nuclear volume greater than 140 micron3 was associated with short term survival. CONCLUSIONS: Measurement of mean nuclear volume was useful as a guide to objective grading of renal cell carcinomas, though there was an overlap between tumour grades. Based on the limited number of cases analysed, the mean nuclear volume is proposed as an additional prognostic indicator.

Adult↗
PubMed2000

Diagnosis of congenital heart malformations--possibilities for the employment of telepathology.

GOAL: In a study of 10 autopsy cases with congenital cardiac malformations we investigated whether obtaining a second opinion by means of telepathology could satisfy quality standards for the diagnosis of cardiac malformations and what the advantages and disadvantages of such a procedure might be. MATERIAL: The investigatory samples were 10 formalin-fixed hearts with complex malformations from 9 fetuses and one newborn on which autopsies had been performed at the Pathological Institute of the Charité Hospital. The requests for a second opinion, which included text and image data, were sent in the form of Microsoft PowerPoint presentations to 5 experts in 4 countries. Per case the number of images that were sent was between 3 and 7. The size of the files was between 439 and 942 kb. The time required for preparation of the cases for sending them to the specialists was between 1 and 2 hours: this encompassed the time for putting the notation on the images, compressing them, creating a file that included both the images and the clinical data and then sending the case file. RESULTS: All 10 cardiac malformations were correctly identified. In 8 of the 10 cases at least one expert had questions. After these questions had been answered and further images had been sent final correct diagnoses were made in all cases. All experts said that the quality of the images was very good. Use of a standardized findings questionnaire, which also included the marking of anatomic structures and of pathological findings in the images, proved useful. Standardized findings forms facilitate orientation during interpretation of the cases and should be used generally to avoid misunderstandings in telepathological communication. CONCLUSIONS: In general it is possible to obtain an effective and reliable diagnosis of congenital heart malformations by means of telepathology. It is far quicker to get a second opinion by this means than by conventional means.

Autopsy↗
PubMedDate not supplied

Neoplastic vs inflammatory meningeal enhancement with Gd-DTPA.

We studied 40 consecutive patients clinically suspected of having meningeal disease, in whom both Gd-diethylenetriamine pentaacetic acid (DTPA)-enhanced magnetic resonance (MR) examinations and CSF or surgical pathologic samples were obtained. The MR examinations were retrospectively reviewed for the presence of abnormal meningeal enhancement, as well as pattern and site of enhancement. The MR findings correctly correlated with pathology results in 15 of 19 patients with suspected tumor involvement (including one true negative) and in 18 of 21 patients with suspected inflammatory meningeal conditions (including 2 true negatives). Pial enhancement was demonstrated in 62% (10 of 16) of patients with meningitis and in 29% (4 of 14) of patients with meningeal neoplastic involvement. A diffuse meningeal distribution was commonly present with inflammatory conditions (69%, 11 of 16). A nodular appearance was seen in two patients with tumor involvement of the meninges as well as in a single case of sarcoidosis but was not seen with infectious meningitis. Our data suggest that Gd-DTPA-enhanced MR imaging is sensitive to the presence of meningeal pathology but is nonspecific as to disease entity. Recognition of certain MR patterns in conjunction with clinical presentation may improve diagnosis and management of patients with suspected meningeal disease.

Contrast Media↗
PubMed2006

The comparative study of magnetic resonance angiography diagnosis and pathology of blunt vertebral artery injury.

STUDY DESIGN: Observational and comparative study of the vertebral artery injury detected by 2-dimensional (2-D) time-of-flight magnetic resonance angiography (MRA) for admitting patients. Construct a strike-induced flexion injury model of cervical spine with blunt vertebral artery injury in dogs. OBJECTIVES: To evaluate the value of MRA for diagnosing vertebral artery injury in cervical spinal trauma patients, and conduct a comparative study of MRA image and pathology of blunt vertebral artery injury in an animal experiment. SUMMARY OF BACKGROUND DATA: The 2-D time-of-flight MRA is the most important method for diagnosing vertebral artery injury. However, there is still controversy over MRA's accuracy in detecting vertebral artery injury of varying degrees. In addition, to our knowledge, no animal studies regarding this subject have been found in the literature so far. METHODS: In a clinical study, 319 patients with close cervical spinal trauma underwent 2-D time-of-flight MRA prospective examination. The 2-D time-of-flight MRA detected vertebral artery injury in 52 of the 319 subjects. Of the 52 patients, 51 had unilateral vertebral artery injuries, including 22 injuries on the left vertebral artery and 29 on the right vertebral artery. One case involved bilateral vertebral artery injury. In an animal experiment, the strike-induced flexion injury model of cervical spine was constructed based on an animal experiment with 26 adult dogs. A radiograph was taken immediately after injury, and 2-D time-of-flight MRA was taken in 24-36 hours. The vertebral artery sample was then harvested for pathologic examination. RESULTS: In the animal experiment, cervical facet dislocation occurred in 14 of the 26 dogs. Of the 26 dogs, 7 had unilateral vertebral artery injury as detected by MRA. There were 2 dogs that had incomplete blood flow imaging on one side of the vertebral artery, which MRA diagnosed as suspect positive. There were no vertebral artery injuries in the other 17 dogs. The vertebral artery sample of all 26 dogs underwent the pathologic study. Of the 7 dogs with positive MRA, 4 had disruption of the intima and media, and 3 had disruption of the intima. Of the 2 dogs with suspicious positive MRA diagnosis, 1 had no intima injury, while the other had intima disruption and late mural thrombus. There was no intima injury in the 17 dogs with negative MRA findings. CONCLUSIONS: The 2-D time-of-flight MRA is an effective diagnostic method for blunt vertebral artery injury. It may have difficulties differentiating spasm, small disruption of the intima from others under certain conditions.

Adolescent↗