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PubMed1997

[Multi-media presentation of radiologic image data with the Internet].

AIM: Recent developments of the Internet (World Wide Web) allow the integration of audio, video, digital film sequences, and three-dimensional data. The applicability of these innovations for medical documentation is demonstrated. METHODS: Our existing software for medical image processing and 3D reconstruction was extended to provide images, film sequences, and complex 3D models in an Internet-compatible data format. RESULTS: The multimedia results of the image processing were integrated into Internet documents. Specialized programs are no longer necessary for visualization. The Internet software allows for user-friendly handling and interactive presentation of the 2D and 3D data. CONCLUSIONS: The Internet offers public-domain software for display of images, audio/video, and 3D data. Thus, the tools of the Internet represent an ideal basis for local hospital information systems, computer-aided medical education, and teleconferencing.

Computer Communication Networks↗
PubMed2000

[3D models for diagnosis and treatment planning in cardiology].

Due to the development new of imaging devices which produce a large number of tomographic slices, advanced techniques for the evaluation of the large amount of data are required. Computer supported extraction of dynamic 3D-models of the patients anatomy from temporal series thus is highly desirable. Since the diagnostician should be able to quickly make sensible decisions based on the models, high accuracy is required within a minimum of time. We present modeling and visualization techniques that are realized within the Cardiac Station. Results for the application of these techniques to cardiac image data demonstrate their usability. Besides giving information about the patients morphology functional parameters can be derived from the data and visualized together with the model. In order to verify the model with the original image data and for the planning of real intervention interaction techniques are presented.

Anatomy, Cross-Sectional↗
PubMed2000

[Basic principles of data acquisition and data processing for construction of high quality virtual models].

Creating models for virtual reality subdivides into several steps. The aim of the data acquisition is the extraction of nearly isotropic (same solution in all three axes) data sets with low noise content. An approximate isotropy can be achieved by suitable choice of scan parameters. For raw data reconstruction, the application of high-resolution reconstruction algorithms is prohibited due to increased noise. A missing isotropy can computationally be approximated by interpolation. Further noise suppression is achieved by applying filters. Additionally, the contrast of the object for segmentation can be increased by image processing operators. The correct choice of the segmentation method and the editing tools is essential for a precise segmentation with minimal user interaction. Prior to visualization, smoothing the shape of the segmented model (shape-based or morphological interpolation, polygon reduction of wire frame model) further improves the visual appearance of the 3D model.

Algorithms↗
PubMed2002

Ultrastructural analyses of pancreatic grafts preserved by the two-layer cold-storage method and by simple cold storage in University of Wisconsin solution.

The two-layer cold storage method (TLM) using University of Wisconsin (UW) solution supplies sufficient oxygen to pancreatic grafts during preservation and extends pancreas preservation time to up to 96 h in the canine model. Simple cold storage in UW (UWM) on the other hand, preserves canine pancreas grafts for up to 72 h by preventing cell swelling, mainly because of its high osmotic pressure. The aim of this study is to analyze morphologically dog pancreatic grafts preserved by these two methods with their different mechanisms. Immediately after preservation of canine pancreata by TLM for 72 h and 96 h (group 1 and group 3, respectively), and by UWM for 72 h and 96 h (group 2 and group 4, respectively), tissue ATP levels were determined using high-performance liquid chromatography (HPLC), and detailed morphological analyses of intragraft components were performed using light- and electron microscopy. The mean areas of one mitochondrion and rough endoplasmic reticulum (RER) vacuolization were calculated by computer-graphic analyses using NIH image 1.62 f soft. The tissue ATP levels were significantly higher in groups 1 and 3 than groups 2 and 4 ( P < 0.05). Light microscopy demonstrated no marked difference among the 4 groups. By electron microscopy however, mitochondrial swelling and RER vacuolization were observed in acinar cells to various extents in the 4 groups. They were significantly more evident in group 2 than group 1 ( P < 0.05), and in group 4 than group 3 ( P < 0.05). In conclusion, TLM demonstrated excellent protection of intracellular organelles, mitochondria, and RER, up to 72-96 h. Well-maintained graft ATP levels in TLM groups may result in maintaining the integrity of intracellular organelle membranes as well as cellular membranes.

Adenosine↗
PubMed1994

Induction of hepatic microsomal CYP4A activity and of peroxisomal beta-oxidation by two non-steroidal anti-inflammatory drugs.

The effects of the non-steroidal anti-inflammatory drugs fenbufen and ibuprofen on hepatic cytochrome P450 activities and peroxisomal proliferation were investigated in the rat, following intraperitoneal administration at three dose levels. At the two highest doses, 30 and 150 mg/kg, ibuprofen stimulated lauric acid hydroxylase activity but no other dose-dependent effects on cytochrome P450 activities were evident. Fenbufen, at the highest dose of 150 mg/kg, decreased cytochrome P450 content and related activities, and this effect was attributed to the toxicity of the drug at this dose. Immunoblot studies employing solubilized microsomes from ibuprofen-treated rats revealed that ibuprofen increased the apoprotein levels of CYP4A1, at the two higher doses. The same treatment with ibuprofen, at the highest dose only, increased the beta-oxidation of palmitoyl CoA, determined in liver homogenates, and immunoblott analysis showed an increase in the apoprotein levels of the trans-2-enoyl CoA hydratase trifunctional protein. Fenbufen did not influence palmitoyl beta-oxidation. Computer graphic overlays with clofibric acid showed that ibuprofen, when compared with fenbufen, displayed a better overall fit to clofibric acid. Finally, interaction energies between the two drugs and the putative peroxisome proliferator-activated receptor ligand domain revealed that ibuprofen had a higher affinity for the receptor than fenbufen, but the difference was modest. It is concluded that ibuprofen, at doses far exceeding those employed clinically, is a weak inducer of both CYP4A1 activity and peroxisomal proliferation and these effects may be attributed to the presence of an aryl propionic acid moiety.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Human postural responses to motion of real and virtual visual environments under different support base conditions.

The role of visual orientation cues for human control of upright stance is still not well understood. We, therefore, investigated stance control during motion of a visual scene as stimulus, varying the stimulus parameters and the contribution from other senses (vestibular and leg proprioceptive cues present or absent). Eight normal subjects and three patients with chronic bilateral loss of vestibular function participated. They stood on a motion platform inside a cabin with an optokinetic pattern on its interior walls. The cabin was sinusoidally rotated in anterior-posterior (a-p) direction with the horizontal rotation axis through the ankle joints (f=0.05-0.4 Hz; A (max)=0.25 degrees -4 degrees ; v (max)=0.08-10 degrees /s). The subjects' centre of mass (COM) angular position was calculated from opto-electronically measured body sway parameters. The platform was either kept stationary or moved by coupling its position 1:1 to a-p hip position ('body sway referenced', BSR, platform condition), by which proprioceptive feedback of ankle joint angle became inactivated. The visual stimulus evoked in-phase COM excursions (visual responses) in all subjects. (1) In normal subjects on a stationary platform, the visual responses showed saturation with both increasing velocity and displacement of the visual stimulus. The saturation showed up abruptly when visually evoked COM velocity and displacement reached approximately 0.1 degrees /s and 0.1 degrees , respectively. (2) In normal subjects on a BSR platform (proprioceptive feedback disabled), the visual responses showed similar saturation characteristics, but at clearly higher COM velocity and displacement values ( approximately 1 degrees /s and 1 degrees , respectively). (3) In patients on a stationary platform (no vestibular cues), the visual responses were basically similar to those of the normal subjects, apart from somewhat higher gain values and less-pronounced saturation effects. (4) In patients on a BSR platform (no vestibular and proprioceptive cues, presumably only somatosensory graviceptive and visual cues), the visual responses showed an abnormal increase in gain with increasing stimulus frequency in addition to a displacement saturation. On the normal subjects we performed additional experiments in which we varied the gain of the visual response by using a 'virtual reality' visual stimulus or by applying small lateral platform tilts. This did not affect the saturation characteristics of the visual response to a considerable degree. We compared the present results to previous psychophysical findings on motion perception, noting similarities of the saturation characteristics in (1) with leg proprioceptive detection thresholds of approximately 0.1 degrees /s and 0.1 degrees and those in (2) with vestibular detection thresholds of 1 degrees /s and 1 degrees , respectively. From the psychophysical data one might hypothesise that a proprioceptive postural mechanism limits the visually evoked body excursions if these excursions exceed 0.1 degrees /s and 0.1 degrees in condition (1) and that a vestibular mechanism is doing so at 1 degrees /s and 1 degrees in (2). To better understand this, we performed computer simulations using a posture control model with multiple sensory feedbacks. We had recently designed the model to describe postural responses to body pull and platform tilt stimuli. Here, we added a visual input and adjusted its gain to fit the simulated data to the experimental data. The saturation characteristics of the visual responses of the normals were well mimicked by the simulations. They were caused by central thresholds of proprioceptive, vestibular and somatosensory signals in the model, which, however, differed from the psychophysical thresholds. Yet, we demonstrate in a theoretical approach that for condition (1) the model can be made monomodal proprioceptive with the psychophysical 0.1 degrees /s and 0.1 degrees thresholds, and for (2) monomodal vestibular with the psychophysical 1 degrees /s and 1 degrees thresholds, and still shows the corresponding saturation characteristics (whereas our original model covers both conditions without adjustments). The model simulations also predicted the almost normal visual responses of patients on a stationary platform and their clearly abnormal responses on a BSR platform.

Adult↗
PubMed2002

Setting up and optimization of membrane protein simulations.

In this paper we describe a method for setting up an atomistic simulation of a membrane protein in a hydrated lipid bilayer and report the effect of differing electrostatic parameters on the drift in the protein structure during the subsequent simulation. The method aims to generate a suitable cavity in the interior of a lipid bilayer, using the solvent-accessible surface of the protein as a template, during the course of a short steered molecular dynamics simulation of a solvated lipid membrane. This is achieved by a two-stage process: firstly, lipid molecules whose headgroups are inside a cylindrical volume equivalent to that defined by the protein surface are removed; then the protein-lipid interface is optimized by applying repulsive forces perpendicular to the protein surface, and of gradually increased magnitude, to the remaining lipid atoms inside the volume occupied by the protein surface until it is emptied. The protein itself may then be inserted. Using the bacterial membrane proteins KcsA and FhuA as test cases, we show how the method achieves the formation of a suitable cavity in the interior of a dimyristoylphosphatidylcholine lipid bilayer without perturbing the configuration of the non-interfacial regions of the previously equilibrated lipid bilayer, even in cases of membrane proteins with irregular geometrical shapes. In addition, we compare subsequent simulations in which the long-range electrostatic interactions are treated via either a cut-off or a particle-mesh Ewald method. The results show that the drift from the initial structure is less in the latter case, especially for KcsA and for the non-core secondary structural elements (i.e. surface loops) of both proteins.

Bacterial Outer Membrane Proteins↗
PubMed2003

Depth cue reliance in surgeons and medical students.

BACKGROUND: Depth perception is reduced in endoscopic surgery, although little is known about the effect this has on surgical performance. METHODS: To assess the role of depth cues, 45 subjects completed tests of depth cue reliance. Surgical skill was assessed using the Minimally Invasive Surgical Trainer-Virtual Reality, a previously validated laparoscopic simulator. RESULTS: We could demonstrate no difference in cue reliance for three depth cues--namely stereo, texture, and outline--between surgeons and medical students. Greater dominance on stereo for medical students was a positive finding and a negative finding for the surgeons when correlated with surgical performance. CONCLUSIONS: We suggest that surgeons learn to adapt to the nonstereo environment in MIS, and this is the first study to show evidence of this phenomenon. This difference in stereo reliance is a reflection of the experience that surgeons have with laparoscopy compared with medical students, who have none.

Adult↗
PubMed2000

Changes of liver fibrosis in chronic hepatitis C patients with no response to interferon-alpha therapy: including quantitative assessment by a morphometric method.

The aim of this study was to evaluate the antifibrotic effect of interferon (IFN)-alpha in chronic hepatitis C (CH-C) patients with no response to IFN-alpha therapy. We studied 76 patients (46 men, 30 women; mean age, 55.6 years) who received IFN-alpha intramuscularly, at a total close of 480 to 880MU for 6 months (group A). As a control group, we studied 50 patients (32 men and 18 women; mean age, 58.5 years) with CH-C who received medication other than IFN (ie, Strong-Neo-Minophagen C, ursodeoxycholic acid, and a herbal medicine, Sho-saiko-to [TJ-9]) and who had persistent alanine aminotransferase (ALT) elevation (group B). All patients were subdivided into three subgroups according to different patterns of ALT changes during the observation period, ie, (a) persistent ALT level < 60IU/ 1 (below about twice the upper limit of the normal range), (b) persistent ALT level > or = 60IU/1, (c) ALT levels other than (a) and (b). Liver biopsy was performed within 6 months prior to IFN therapy and more than 6 months after IFN therapy, while two liver biopsies were performed during therapy in group B. Liver fibrosis was compared between two specimens by staging. When the fibrosis stage was the same in the two specimens, we determined whether the fibrosis had improved or worsened by comparing the fibrotic ratio, ie, the ratio of the area of fibrosis to the area of the entire liver tissue specimen, calculated using computed graphic software. Serum aminoterminal peptide of type III procollagen (PIIIP) levels were measured on the day of the liver biopsy and their mean yearly changes were compared between the two groups. Improvement of liver fibrosis was found in 12% to 30% of patients in each ALT subgroup and in 24% of all patients in group A and there were no significant differences in liver fibrosis in comparison with findings in of group B when assessed by staging alone. However, these percentages rose to 59% to 75% and 66%, respectively, when liver fibrosis was assessed by the fibrotic ratio together with staging, resulting in a significant difference in fibrosis between groups A and B in total (P < 0.01). The mean yearly changes in serum PIIIP levels in each subgroup and in all patients in group A were below zero, indicating a tendency to improvement of fibrosis after IFN therapy, while these changes in group B were all above zero, except for subgroup (c). Improvement of fibrosis after IFN therapy was found in 15 of 24 patients (64%) whose ALT changes had the same pattern before and after IFN therapy, although no significant difference was noted between improved and worsened patients. These results suggest that IFN-alpha may have an antifibrotic effect even in CH-C patients with no overt response to IFN-alpha therapy, compared with the effect of medications other than IFN.

Alanine Transaminase↗
PubMed2001

Changes in gastrointestinal lymph and blood vessels in patients with cirrhotic portal hypertension.

BACKGROUND: The aim of this study was to characterize the lymph vessels in different parts of the gastrointestinal tract and also to evaluate morphometric changes in these vessels during cirrhotic portal hypertension. METHODS: Sixteen patients with cirrhotic portal hypertension and 18 control subjects without portal hypertension were enrolled in the study. Tissue specimens were collected at autopsy or surgery, and were stained enzyme histochemically, using 5'-nucleotidase and alkaline phosphatase to distinguish lymph vessels and blood vessels, respectively. The numbers of vessels and their luminal areas were estimated using computer graphics software (National Institutes of Health [NIH] image program). RESULTS: The numbers and luminal areas of the lymph vessels varied considerably among the different organs of the gastrointestinal tract, both in controls and in the patients with cirrhotic portal hypertension. There was no significant difference in the numbers of lymph vessels between controls and patients with cirrhotic portal hypertension. However, the luminal area of the lymph vessels in the esophagus and stomach was significantly greater in the patients with cirrhotic portal hypertension than in the controls. These differences in lymph vessels were not seen in the small intestine and colon. CONCLUSIONS: These data indicate that dilatation of lymph vessels may be related to the absorption of excess interstitial fluid, resulting from congestion, in cirrhotic portal hypertension.

5'-Nucleotidase↗
PubMed2000

Three-dimensional morphological analysis of the proximal femoral canal, using computer-aided design system, in Japanese patients with osteoarthrosis of the hip.

An accurate three-dimensional morphological analysis of the femur is required to produce well fitting uncemented femoral implants. A computer-aided design system made it possible to produce three-dimensional femoral models and to accurately measure certain parameters with planes standardized for all subjects. The study subjects were Japanese; there were 89 patients (113 hips) with osteoarthrosis (OA) and 18 volunteers (36 hips) free of hip joint complaints and with no abnormal radiological findings (normal; N). The femoral canal was classified into three types, A-I, A-II, and B-II, based on the shape in the frontal and sagittal planes. Either triangular (type T) or circular (type C) shapes were identified at the proximal cross section. Type A-II, which is considered the standard type, accounted for 89% of the N hips, and 42% of the OA hips. Type A-I, with a posterior canal plane strongly inclined toward the anterior, accounted for 26% of the OA hips and 6% of the N hips; 96% of type A-I hips were triangular. Type B-II, which had a steep medial canal plane, accounted for 29% of the OA hips and 6% of the N hips; 63% of type B-II hips were circular.

Adult↗
PubMed2006

SOMMER: self-organising maps for education and research.

SOMMER is a publicly available, Java-based toolbox for training and visualizing two- and three-dimensional unsupervised self-organizing maps (SOMs). Various map topologies are implemented for planar rectangular, toroidal, cubic-surface and spherical projections. The software allows for visualization of the training process, which has been shown to be particularly valuable for teaching purposes.

Algorithms↗
PubMed2004

[Rapid prototyping in planning reconstructive surgery of the head and neck. Review and evaluation of indications in clinical use].

PURPOSE: The aim was to define the indications for use of rapid prototyping models based on data of patients treated with this technique. PATIENTS AND METHODS: Since 1987 our department has been developing methods of rapid prototyping in surgery planning. During the study, first the statistical and reproducible anatomical precision of rapid prototyping models was determined on pig skull measurements depending on CT parameters and method of rapid prototyping. RESULTS: Measurements on stereolithography models and on selective laser sintered models confirmed an accuracy of +/-0.88 mm or 2.7% (maximum deviation: -3.0 mm to +3.2 mm) independently from CT parameters or method of rapid prototyping, respectively. With the same precision of models multilayer helical CT with a higher rate is the preferable method of data acquisition compared to conventional helical CT. From 1990 to 2002 in atotal of 122 patients, 127 rapid prototyping models were manufactured: in 112 patients stereolithography models, in 2 patients an additional stereolithography model, in 2 patients an additional selective laser sinter model, in 1 patient an additional milled model, and in 10 patients just a selective laser sinter model. CONCLUSION: Reconstructive surgery, distraction osteogenesis including midface distraction, and dental implantology are proven to be the major indications for rapid prototyping as confirmed in a review of the literature. Surgery planning on rapid prototyping models should only be used in individual cases due to radiation dose and high costs. Routine use of this technique only seems to be indicated in skull reconstruction and distraction osteogenesis.

Computer Graphics↗
PubMed1999

[New possibilities of temporomandibular joint registration during orthodontic operations].

Repositioning osteotomies in a Le Fort I fashion can affect the position of the TMJ, which cannot be viewed directly during surgery. Using the computer-assisted navigation system SSN (Surgical Segment Navigator), the intraoperative position of the TMJ can be checked and unintentional malpositions can be detected. Positioning of the maxilla after Le Fort I osteotomy was carried out in a conventional fashion. Afterwards, the position of the maxilla was corrected in the same patients using the SSN. In this way, the precision of conventional and SSN-guided positioning of the maxilla and its effect on the TMJ has been compared.

Cephalometry↗
PubMed2003

Perception of depth from shading in infant chimpanzees ( Pan troglodytes).

We investigated the ability to perceive depth from shading, one of the pictorial depth cues, in three chimpanzee infants aged 4-10 months old, using a preferential reaching task commonly used to study pictorial depth perception in human infants. The chimpanzee infants reached significantly more to three-dimensional toys than to pictures thereof and more to the three-dimensional convex than to the concave. Furthermore, two of the three infants reached significantly more to the photographic convex than to the photographic concave. These infants also looked longer at the photographic convex than the concave. Our results suggest that chimpanzees perceive, at least as early as the latter half of the first year of life, pictorial depth defined by shading information. Photographic convexes contain richer information about pictorial depth (e.g., attached shadow, cast shadow, highlighted area, and global difference in brightness) than simple computer-graphic graded patterns. These cues together might facilitate the infants' perception of depth from shading.

Age Factors↗
PubMed2006

Towards a "virtual pigeon": a new technique for investigating avian social perception.

The purpose of the present study is to examine the applicability of a computer-generated, virtual animal to study animal cognition. Pigeons were trained to discriminate between movies of a real pigeon and a rat. Then, they were tested with movies of the computer-generated (CG) pigeon. Subjects showed generalization to the CG pigeon, however, they also responded to modified versions in which the CG pigeon was showing impossible movement, namely hopping and walking without its head bobbing. Hence, the pigeons did not attend to these particular details of the display. When they were trained to discriminate between the normal and the modified version of the CG pigeon, they were able to learn the discrimination. The results of an additional partial occlusion test suggest that the subjects used head movement as a cue for the usual vs. unusual CG pigeon discrimination.

Animals↗
PubMed2005

Solution for nonuniformities and spatial noise in medical LCD displays by using pixel-based correction.

Liquid crystal displays (LCD) are rapidly replacing cathode ray tube displays (CRT) for medical imaging. LCD technology has improved significantly in the last few years and has important advantages over CRT. However, there are still some aspects of LCD that raise questions as to the usefulness of liquid crystal displays for very subtle clinical diagnosis such as mammography. One drawback of modern LCD displays is the existence of spatial noise expressed as measurable stationary differences in the behavior of individual pixels. This type of noise can be described as a random stationary image superposed on top of the medical image being displayed. It is obvious that this noise image can make subtle structures invisible or add nonexistent patterns to the medical image. In the first case, subtle abnormalities in the medical image could remain undetected, whereas in the second case, it could result into a false positive. This paper describes a method to characterize the spatial noise present in high-resolution medical displays and a technique to solve the problem. A medical display with built-in compensation for the spatial noise at pixel level was developed and improved image quality is demonstrated.

Algorithms↗