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Biomedical subjects

D Paulus

Publications and source records attributed to D Paulus.

14 recordsLinked to original sources
PubMed2005

Automated segmentation of the optic nerve head for diagnosis of glaucoma.

Glaucoma is the second most common cause of blindness worldwide. Low awareness and high costs connected to glaucoma are reasons to improve methods of screening and therapy. A well-established method for diagnosis of glaucoma is the examination of the optic nerve head using scanning-laser-tomography. This system acquires and analyzes the surface topography of the optic nerve head. The analysis that leads to a diagnosis of the disease depends on prior manual outlining of the optic nerve head by an experienced ophthalmologist. Our contribution presents a method for optic nerve head segmentation and its validation. The method is based on morphological operations, Hough transform, and an anchored active contour model. The results were validated by comparing the performance of different classifiers on data from a case-control study with contours of the optic nerve head manually outlined by an experienced ophthalmologist. We achieved the following results with respect to glaucoma diagnosis: linear discriminant analysis with 27.7% estimated error rate for automated segmentation (aut) and 26.8% estimated error rate for manual segmentation (man), classification trees with 25.2% (aut) and 22.0% (man) and bootstrap aggregation with 22.2% (aut) and 13.4% (man). It could thus be shown that our approach is suitable for automated diagnosis and screening of glaucoma.

Algorithms↗
PubMed2004

Evaluation of computer-assisted image enhancement in minimal invasive endoscopic surgery.

OBJECTIVES: This paper focuses on the evaluation of the usage of computer-aided image processing methods for minimal invasive surgery. During video endoscopy of visceral cavities the images are displayed directly on the monitor without further processing. In the course of the operation the former good quality of the images decreases due to typical disturbances like bleeding, smoke or flying particles. These disturbances can be reduced by using image processing methods like color normalization, temporal filtering or equalization. METHODS: In this double-blinded analysis, 14 surgeons with different levels of experience evaluated 120 image pairs and 5 image sequences, directly comparing original and processed images or movies. RESULTS: Color normalization and equalization proved to significantly enhance video endoscopic images. With regard to temporal filtering, an improvement could be seen in the image sequences with filter size 5 being a greater enhancement than filter size 3. Comparing the state of experience and its influence on the results, it occurred that the experienced surgeons preferred the original color while altogether agreeing that the color-normalized images were better. CONCLUSIONS: The results obtained in the present evaluation show that the image processing methods which were used can significantly improve the quality of video endoscopic images. As a result of this, necessary lavages of the operated area are reduced and a better overview and orientation for the surgeon can be reached.

Humans↗
PubMed2004

Light fields for minimal invasive surgery using an endoscope positioning robot.

OBJECTIVES: To generate a fast and robust 3-D visualization of the operation site during minimal invasive surgery. METHODS: Light fields are used to model and visualize the 3-D operation site during minimal invasive surgery. An endoscope positioning robot provides the position and orientation of the endoscope. The a priori un-known transformation from the endoscope plug to the endoscope tip (hand-eye transformation) can either be determined by a three-step algorithm, which includes measuring the endoscope length by hand or by using an automatic hand-eye calibration algorithm. Both methods are described in this paper and their respective computation times and accuracies are compared. RESULTS: Light fields were generated during real operations and in the laboratory. The comparison of the two methods to determine the unknown hand-eye transformation was done in the laboratory. The results which are being presented in this paper are: rendered images from the generated light fields, the calculated extrinsic camera parameters and their accuracies with respect to the applied hand-eye calibration method, and computation times. CONCLUSION: Using an endoscope positioning robot and knowing the hand-eye transformation, the fast and robust generation of light fields for minimal invasive surgery is possible.

Algorithms↗
PubMed2001

[Image analysis system for detection facial paralysis].

BACKGROUND: Evaluation of facial nerve paresis depends on visual assessment and naturally differs from examiner to examiner. An objective measurement instrument is presented. PATIENTS AND METHOD: Facial features are automatically localized by a parametric face model in videos of a face during relaxation and exercises. Gray-level information is analyzed by a special steerable filter and used to identify symmetries. The computer system was tested in 19 individuals. RESULTS: Automatic localization of facial features such as the upper arc of the head and ears was correct in 95%, the eyes in 82%, and the mouth in 73%. Lid paresis was correctly recognized in seven of ten (70%) and oral paresis in 10 of 12 (83%) cases. Unaffected eyelid movements were identified in eight of nine (89%) and healthy oral regions in all seven (100%) cases. CONCLUSION: The computer system presented is able to automatically localize facial features and to identify facial nerve paresis. It is a considerable step toward automatic and objective grading of facial nerve paresis.

Diagnosis, Computer-Assisted↗
PubMed2001

Dietary habits during adolescence--results of the Belgian Adolux Study.

UNLABELLED: OBJECTIVE OF THE PRESENT STUDY: To analyse the usual dietary habits of Belgian adolescents from a high cardiovascular risk population. METHODS: A food frequency questionnaire (57 items) was administered to the whole sample. Complementary questions specified some types of food (eg fat content). A subgroup of 234 adolescents gave detailed information on portion size (picture book and food samples). SETTING: Twenty-four secondary schools in the Belgian province of Luxembourg. SUBJECTS: A total of 1,526 adolescents (12-17y) selected by a multiclustered stage sampling (participation: 83.6%). RESULTS: Respectively 46% and 60% of the adolescents did not eat fruit and vegetables daily. Most of the adolescents (72%) consumed at least one dairy product daily. The frequent consumption of chocolate and French fries indicated the strong cultural influence on dietary habits while imported foods (like hamburgers) had little success. One-third of the adolescents (33%, n = 509) drank alcohol at least once a week and this proportion rose to 57% in the oldest age group. Boys and girls differed significantly in their diet, with girls choosing healthier foods. Dietary habits, in particular drinking habits, differed also significantly between education levels, assessed by the learning option of the participants. The semi-quantitative questionnaire showed that two-thirds of the adolescents had a lipid intake (mainly saturated fatty acids) which exceeded 35% of the total caloric intake. Complex carbohydrates represented less than half of the total carbohydrates intake. CONCLUSION: The study of the diet of Belgian adolescents confirmed the strong influence of tradition, in particular on the consumption of high fat content foods. The promotion of healthy diet in adolescents should consider the cultural influence, even for this young age group.

Adolescent↗
PubMed2000

Oral contraception and cardiovascular risk factors during adolescence.

The objective of the present study was to analyze the pattern of oral contraceptive (OC) use in teenagers and to examine the relationship between OC use and other cardiovascular risk factors. The study was conducted in 24 Belgian secondary schools. Most students (1526 adolescents aged 12-17 years) agreed to participate (participation rate: 83.6%). Smoking, physical activity habits, menarche, and OC use were assessed by a self-administered questionnaire. Total cholesterol level, blood pressure and anthropometric measurements were also measured. Fourteen per cent of mature girls (14%, n = 92) were OC users. Two-thirds of them (66.3%, n = 61) were taking OC which contained either gestodene or desogestrel. Blood pressure and BMI were similar for OC users and non-users. Total cholesterol level was significantly higher in OC users than in non-users (191 mg/dL versus 172 mg/dL). Logistic regression model confirmed the significant influence of OC use on total cholesterol level (OR = 3.08). OC users were also often smokers (39% versus 20% for non-users). In conclusion, the present study has found significant relationships between OC use and cardiovascular risk factors i.e., high total cholesterol and smoking. The first implication is a need for further research on lipoprotein profile in young OC users. Secondly, the combined use of OC and smoking in teenagers calls for preventive actions.

Adolescent↗
PubMed1999

Combination therapy with tacrolimus and mycophenolate mofetil following cardiac transplantation: importance of mycophenolic acid therapeutic drug monitoring.

BACKGROUND: Interest has recently been expressed in tacrolimus and mycophenolate mofetil (MMF), two potent immunosuppressants, for a variety of transplant indications. The efficacy of this combination was assessed as primary therapy following cardiac transplantation. METHODS: Forty-five patients were enrolled; 15 into Phase I and 30 to Phase II of the study. Intravenous tacrolimus was administered for 2-3 days to all patients prior to conversion to oral therapy; target blood concentrations were 10-15 ng/mL. Treatment also consisted of steroids and MMF. During Phase I, a fixed 2 g/day dose of MMF was given whilst doses were adjusted according to mycophenolic acid (MPA) plasma levels during Phase II (target range 2.5-4.5 microg/mL). Mean follow-up was 696 +/- 62 days and 436 +/- 88 days for Phases I and II, respectively. RESULTS: Phase I: Patient survival was 100%. Rejection was diagnosed in 66.7% of patients (mean number of episodes per patient 1.33 +/- 1.18). Retrospective analyses indicated that whereas mean MPA plasma levels >3.0 microg/mL were not associated with rejection, no correlation was found with tacrolimus blood concentrations. Phase II: A survival rate of 96.7% was evident, one patient having died from aspergillosis. Diagnoses of rejection were made in 10.0% of patients (0.10 +/- 0.31 episodes per patient) and confounding factors were present in all 3 cases. MPA trough levels were 1.0 +/- 0.3 microg/mL at this time. Resolution was apparent following pulse steroid therapy. Steroids were successfully withdrawn from all patients who completed 6 months' treatment. CONCLUSIONS: Combination therapy with tacrolimus and MMF is associated with suppression of acute myocardial rejection; however, this is dependent upon routine therapeutic drug monitoring.

Adolescent↗
PubMed1999

Three-dimensional computer vision for tooth restoration.

If a person with carious lesions needs or requests crowns or inlays, these dental fillings have to be manufactured for each tooth and each person individually. We survey computer vision techniques which can be used to automate this process. We introduce three particular applications which are concerned with the reconstruction of surface information. The first one aims at building up a database of normalized depth images of posterior teeth and at extracting characteristic features from these images. In the second application, a given occlusal surface of a posterior tooth with a prepared cavity is digitally reconstructed using an intact model tooth from a given database. The calculated surface data can then be used for automatic milling of a dental prosthesis, e.g. from a preshaped ceramic block. In the third application a hand-made provisoric wax inlay or crown can be digitally scanned by a laser sensor and copied three dimensionally into a different material such as ceramic. The results are converted to a format required by the computer-integrated manufacturing (CIM) system for automatic milling.

Adolescent↗
PubMed1999

Blood pressure during adolescence: a study among Belgian adolescents selected from a high cardiovascular risk population.

INTRODUCTION: The Belgian province of Luxembourg has a high incidence of cardiovascular (CV) disease according to the MONICA register. Surveys conducted in adults and children have also found high CV risk factor levels in this province. DESIGN: cross-sectional study. OBJECTIVE OF THE PRESENT STUDY: To collect data about blood pressure (BP) and its determinants in adolescents from this high CV risk population and to analyse their relationship. PARTICIPANTS: 1526 adolescents (12-17 years) in 24 secondary schools of the province. RESULTS: Mean systolic BP levels were 125 mm Hg (sd = 12 mm Hg) and 122 mm Hg (sd = 11 mm Hg) for boys and girls, respectively. Mean diastolic BP was equal to 74 mm Hg (sd = 10 mm Hg) in both genders. Systolic BP increased with age and differed significantly between genders from 15 years onwards. Body fatness indices increased with age except waist-to-hip ratio in girls and triceps skinfold in boys. Regression models including age, anthropometric indices and physical activity explained a small percentage of BP variance (for systolic BP, r2 = 0.21 and 0.12 for boys and girls, respectively). Weight was the first parameter related to BP in correlation and regression analyses. CONCLUSIONS: This study showed high BP and body fatness indices in adolescents from a high CV risk population. The model under study showed a moderate relationship between body fatness and BP. This finding suggests other influences as a genetic component to account for the high levels observed.

Adolescent↗
PubMed1998

Single-center randomized trial comparing tacrolimus (FK506) and cyclosporine in the prevention of acute myocardial rejection.

BACKGROUND: To compare the efficacy and safety of tacrolimus and cyclosporine in heart transplantation, this single-center, prospective, randomized, open-label clinical trial was undertaken. METHODS: Seventy-three adult patients were randomly assigned at the time of transplantation to receive either tacrolimus (n=43) or cyclosporine (n=30) as the primary immunosuppressant. Ten of the 43 patients in the tacrolimus group received the drug intravenously in the perioperative period; all other patients received only oral tacrolimus. RESULTS: With a mean follow-up of 27 months, patient survival rates (tacrolimus 83%, cyclosporine 81%) were similar. Fewer patients experienced acute rejection in the tacrolimus group (79%) than in the cyclosporine group (100%), but the difference was not statistically significant. The number of infections and dialysis and insulin requirements were similar for the 2 treatment groups, but the proportion of patients requiring multidrug antihypertensive regimens was lower in the tacrolimus group (12.5% vs 50.0% at month 6; p=.025). The interpatient variance in pharmacokinetic parameters in a subset of 10 patients was much higher after the first oral dose of tacrolimus than at steady-state (eg, first-dose time at which maximal concentration is reached (t(max)): 3.5+/-2.5h, steady-state t(max): 2.0+/-0.7h), and patients treated with intravenous tacrolimus (n=13) rather than oral tacrolimus (n=30) reached target concentrations faster and with less interpatient variability (eg, at day 0: 9.72+/-10.9 ng/mL intravenously vs 3.31+/-8.1 orally). CONCLUSIONS: Tacrolimus was associated with similar efficacy and safety profiles compared with cyclosporine. The higher interpatient variance in absorption associated with oral tacrolimus during the first few days after transplantation would suggest that intravenous tacrolimus should be used during the perioperative period.

Administration, Oral↗
PubMed1988

Management of stage III primary breast cancer with primary chemotherapy, surgery, and radiation therapy.

One hundred seventy-four evaluable patients with noninflammatory Stage III (both operable and inoperable) breast cancer were treated with a combined modality strategy between 1974 and 1985. All patients received combination chemotherapy with 5-fluorouracil, Adriamycin (doxorubicin), and cyclophosphamide (FAC) as their initial form of therapy. After three cycles of chemotherapy, local treatment in the form of a total mastectomy with axillary dissection, or radiotherapy, or both, was completed. Subsequently, adjuvant chemotherapy was continued. There were 48 patients with Stage IIIA, and 126 patients with Stage IIIB disease. A complete remission was achieved in 16.7% of the patients, and 70.7% achieved a partial remission after the initial three cycles of FAC. The complete response rate was higher for patients with Stage IIIA, than for patients with Stage IIIB disease. All but six of the 174 patients treated were rendered disease-free after induction chemotherapy and local treatment. The median follow-up of this group of patients is 59 months. The 5-year disease-free survival rates were 84% for patients with Stage IIIA, and 33% for patients with Stage IIIB disease. The 5-year survival rate for, patients with Stage IIIA was 84%, and for patients with Stage IIIB 44%. At 10 years, 56% of patients with Stage IIIA and 26% of patients with Stage IIIB disease are projected to be alive. Younger patients, and those with estrogen receptor-positive tumors, had a trend for better survival than older patients and those with estrogen receptor-negative tumors. The quality of response to induction chemotherapy correlated prominently with prognosis, as did compliance with treatment. Twenty-six patients (15.3%) had locoregional recurrence. This multidisciplinary approach to locally advanced breast cancer rendered most patients disease-free and produced an excellent local control rate. Modifications of this treatment strategy may result in further improvement of survival rates.

Adult↗
PubMed1980

Pseudohypertension due to medial calcific sclerosis.

A hypertensive crisis requires rapid diagnosis and treatment to prevent serious sequelae. A patient with medial calcific sclerosis, however, may appear to have extremely elevated blood pressure values but, in effect, be normotensive. Consideration should be given to this condition when the patient's clinical appearance does not reflect the extremely elevated blood pressure values as measured.

Aged↗