[A solution to add digital signatures to medical images according to the DICOM standard: embedded systems]. / Ein Lösungsweg, um medizinische Bilder mit digitalen Signaturen nach dem DICOM-Standard zu versehen: Embedded Systems.

Radiology departments often underestimate the importance of protecting medical data during transmission, including the precautions taken to ensure data protection. In teleradiology, transmitted as well as stored patient data have to be signed digitally according to the currently valid regulation (Rontgenverordnung, RoV). The DICOM standard facilitates a digital signature. So far, medical image manufacturers only announced to support this security feature. We introduce a solution that extends the feature of digital signing to older modalities.

Patient data security in the DICOM standard.

The DICOM committee added the section "Security Profiles" to the DICOM standard, in order to provide the opportunity of safe communication between health care system partners. Data complying with the DICOM standard--e.g. pictures, signals or reports of examinations can be provided with one or more digital signatures. Attention should be paid to the fact that these possibilities of the DICOM standard are available or can be supplied subsequently by new acquisitions of radiological modalities. The required information to check these prerequisites are given.

[Adhesions and interference images of unfixed erythrocytes]. / Adhäsions- und Interferenzfiguren unfixierter Erythrozyten.

For the analysis of deformability in microcirculatory investigations an exact understanding of red blood cell (RBC) geometry is required. To extend knowledge we introduce a new morphological feature of resting unfixed erythrocytes by means of an inverted reflection contrast microscope (RCM). By assessing the interference patterns caused by RCM erythrocytes can be classified according to the depth of their central concavity which depends on the flexibility of the RBC. Moreover, the RBC adhesion can be directly observed. We found out that: 1. Five types of normocytes can be distinguished in RCM. 2. In phase contrast the size distribution of RBC without central concavity (type 5, 11.53% of all normocytes) shows peaks at 48 microns2 and 52 microns2. 3. Image analysis reveals two size categories of relative adhesion areas. One category consists of type 1 and 2 (relative adhesion area 25.63%), the other of the types 3 to 5 (relative adhesion area 39.91%). Besides, RCM allows the reliable identification of pathologic erythrocytes in unstained specimens.

[New paths for Internet generated learning in anatomy]. / Neue Wege der Internet-gestützten Lehre in der Anatomie.

For the purposes of a functioning information and knowledge based medicine the conditions for the medical education are crucial. Although multimedia based courses and tutorials via the Internet seem to serve best for a more effective teaching and new didactics, respective anatomical offers in Germany are scarce and thus practice and experience are limited. Only simple digital equivalents of conventional contents and methods can be found, whereas the potencies of the new media are not realized in didactic concepts. Substantial advantages of web based tutorial systems are an intensive use of the feedback possibilities, the opportunity for continuous updating of the contents, the favourable distribution, and faster utilization of improved techniques. This paper introduces the adaptation of different techniques and the development of concepts and notions of modern Internet based teaching by the way of three different events in anatomical education for medical students and doctors. HistoNet 2000 was developed as an interface of lectures, seminars and practical courses in microscopy. The online transmission of a microscopical course as an interactive practical teleteaching was performed by the way of asymmetric data transfer via the ADSL-technology. Multicasting was used as well and has also been applied for the third project. In this multimedial online teaching different specialties were joined together for interdisciplinary courses via the Internet. These new technologies lead to enhanced efficiency in teaching and enlarge the educational offer. Specific Internet adapted teaching and learning projects have to be developed.

Evaluation on blood platelets by the image analysis system VIDAS 2.5.

This paper introduces a program written on the image analysis system VIDAS 2.5. It enables the automatic quantification of high numbers of adhesion areas of vital human platelets, thus allowing statistical analysis. These adhesion areas were observed by reflection contrast microscopy (RCM), which generates images of an intense contrast and serves as a prerequisite for an evaluation by image analysis. However, RCM-photographs of the observed platelets have highly varying mean greyvalues and greyranges. These common problems for self-operating identification are excluded by two procedures within the program: 1. calibration of the scanning process for an optimal use of the available greyvalues provided by the negative, camera, and the image analysis system; and 2. relation of the threshold for discrimination of adhesion areas to the statistic parameters of the histogram within each individual digitized image. Images processed according to these prerequisites were transferred to the VIDAS implemented routines for identification and measurement of areas. Thus, image analysis combined with RCM offers a tool for basic and clinical platelet research, which is shown by an example of stimulation and inhibited stimulation of platelet activation.

Live interdisciplinary teaching via the internet.

The independence of teachers and students is one of the main advantages of teleteaching. Specialties considered unsuitable for combined lessons are manageable using the internet. This study outlines simultaneous communication with students and lecturers over long distances between the anatomical dissection laboratory, the operating theatre, and the lecture hall. In several three-directional on-line lectures, different equipment was used. Students could also participate using personal computers from other locations. During the presentations, the participants have the opportunity to discuss problems with any lecturer. It was possible to demonstrate sufficient transmission capability for real-time application with the use of the new internet technology. No important qualitative differences can be reported between: hardware and software based solutions; or commercial and free offers. Although it is often difficult to reconcile the timetable of surgeries and lectures, multimedia on-line teaching via the internet provides new potential for interdisciplinary medical education.

[Clinical anatomy as an integrating element in teaching surgical subjects]. / Klinische Anatomie als integrierendes Element in der Lehre der operativen Fächer.

Different conceptions to revise the licensing regulations for physicians (Approbationsordnung für Arzte) aim to interlock preclinical and clinical subjects. Therefore a more practice-oriented anatomy has to be taught in basic and postgraduate medical education. At the Westfalian Wilhelms University of Münster we established an interdisciplinary anatomical education, executed by clinical lecturers in cooperation with the educational staff of the Department of Anatomy. The intergral element is the comprehensive constitution of clinical anatomy: clinical practitioners of different specialties together with anatomists give lessons in applied anatomy accompanying the dissection course. Clinically experienced lecturers of anatomy guide senior medical students in practical courses, refreshing their anatomical knowledge using particular prosections. These courses correlate with the topics of the distinct clinical tutorials. Conjointly clinical practitioners and anatomists plan, and perform meetings in postgraduate medical education.

[Precision and comparison of CT-, MRI- and DL-controlled interventions exemplified by lumbar facet infiltration--an experimental study]. / Präzision und Vergleich von CT-, MR- und DL-gesteuerten Interventionen am Beispiel der lumbalen Facetteninfiltration--eine experimentelle Untersuchung.

We evaluated the accuracy of the needle tip representation by different imaging techniques for the guidance of facet infiltrations. For visualisation of the lumbar facet joints we used a high-field magnetic resonance tomograph (MRT) with a 2.0 Tesla field and 3.5 mm slice thickness, an open low-field magnetic resonance tomography (MRT) with an 0.064 Tesla field and 9 mm slice thickness, and IMATRON electron beam computed tomograph (EBCT) with a slice thickness of 6 mm, and a mobile C-arm fluoroscope. The study was performed on 4 human cadaveric lumber spine preparations, each of which had 8 facet joints. Under imaging control, special injection needles were placed as close as possible to the facet joint space. Following placement of he needle, all specimens were scanned with the electron beam tomograph using a slice thickness of 1.5 mm. The thin-slice study served as the gold standard. The distance between the tip of the needle and the facet joint was measured in all the images. Comparison of the different modalities with the gold standard revealed the following results: 1) median values of the absolute differences were 1.25 mm for high-field MRI, 1.35 mm for 6 mm EBCT, 2.05 mm for low-field MRI, and 2.30 mm for X-ray fluoroscopy. 2) While there was no statistically significant difference in the accuracy of tip localization between high-field MRI and 6" EBCT (p = 0.293), both systems were more precise than low-field MRI (p = 0.04) and X-ray fluoroscopy (p = 0.009). When choosing the best imaging technique, such additional factors as radiation, costs and time, must also be considered. Provided necessary radiological precautions are taken, and assuming careful pre-interventional planning, CT. EBCT and X-ray fluoroscopy are currently more effective than the expensive, time-consuming and costly magnetic resonance tomography.

[Possibilities of spinal endoscopy within the scope of minimal invasive intervention--an experimental study]. / Möglichkeiten der Spinaloskopie im Rahmen der minimal invasiven Intervention--eine experimentelle Untersuchung.

The purpose of the present study was to evaluate, in vitro, a newly designed spinaloscope with a diameter of 1.8 mm, with integrated portals for instruments and irrigation. The 0 degree optical system has a resolution of 6,000 pixels. The instrument portals can be used for surgical lasers, biopsy forceps or burrs. We carried out our evaluations on fresh (unfixed) human lumbar spine specimens. The position of the endoscope was documented by CT scans. The endoscope was introduced into the spinal canal via the hiatus sacralis using a blunt trocar. The various structures and tissues were clearly identifiable and included the dura, the lig. flavum, the lig. long. posterior, spinal nerves, small pieces of disc material and various fibrous bands. The usefulness of the biopsy forceps was also shown.

[Percutaneous vertebral augmentation (PVA) in osteoporosis of the vertebrae--an experimental study]. / Perkutane vertebrale Augmentation (PVA) bei osteoporotischen Wirbelkörpern--eine experimentelle Unterschung.

The present study was conducted with the aim of establishing whether minimally invasive percutaneous techniques used to stabilize osteoporotic vertebrae are technically feasible. Two different methods were investigated in human thoracolumbar cadaveric vertebrae. In the first technique, special titanium implants were placed via a postero-lateral approach. With the second method, the vertebrae were filled with different types of cement of different viscosities. After each procedure, the vertebrae were examined with conventional X-ray and CT scans. The first technique proved quite unsuccessful--the insertion of the titanium implants proving difficult despite the use of special instruments. The results achieved with the second method were much better. The use of low-viscosity bone cement produced the best results. Despite a single lateral point of entry, the vertebrae were almost completely filled right into the contralateral side. Lumbar vertebrae required an average volume of cement of 7 ml (range: 6.5-10 ml) and thoracic vertebrae 5.5 ml (range: 4-7 ml). Specially developed cement application devices made possible problem-free, controlled introduction of the cement.

[Design features of an individual thrust plate prosthesis]. / Konstruktionsmöglichkeiten einer Individuellen Druckscheibenprothese (I-DSP).

The purpose of the present study was to document the osteotomy plane for the thrust plate prosthesis, and to evaluate the question whether the geometry of the thrust plate itself correlates with the range of motion after implantation and whether the osteointegration area can be optimised. For the first part of the study, the two-dimensional geometry of the osteotomy was demonstrated in 12 computer-reconstructed femurs after performing a virtual cut at a CCD angle of 135 degrees. In the second part we constructed a prototype of an I-TPP with an optimised thrust plate and corpus geometry. In a final step, we documented the range of motion with computer-aided movement mapping. The results showed a wide variance in osteotomy geometry in the 12 femurs. With the I-TAP we were able to obtain a much better surface adaptation of the thrust plate. Movement mapping showed a much lower range of motion in the I-TPP implant.

Reflection contrast microscopy (RCM): a forgotten technique?

Reflection contrast microscopy (RCM), which utilizes the optical phenomena caused by oblique epi-illumination in combination with a specific optical apparatus, provides an approach for exploring biological phenomena in greater detail. The lack of stray reflection makes it superior to other microscopes. It bridges light and electron microscopic capabilities by allowing the analysis of ultrathin sections beyond the usual light microscopic magnification. By using consecutive image analysis, quantitation can be achieved. The wide range of applications of RCM can be combined with most microscopical techniques, so extending the spectrum of information that can be gathered. Twenty-five years after the development of RCM, there is still scope for its application in modern cell biology.

Three-dimensional reconstruction of senile plaques in Alzheimer's disease.

So far, the three-dimensional approach to senile plaques, one of the principal histopathological hallmarks in Alzheimer's disease besides neurofibrillary tangles, has been scarce. Two main problems in three-dimensional reconstruction of histological specimens are the horizontal distortion during the preparation of serial thin tissue-slides and the need for consecutive vertical readjustment. This is greatly facilitated by the reflection contrast microscope (Leica, Germany) which is a light microscopical instrument causing interference patterns and reflections along interfaces by means of circularly polarized epi-illumination. Using this technique, one can obtain distinct optical sections of a depth of 1.5 microns within specimens up to 30 microns in thickness, thus preserving the integrity of the observed object and rendering a manual alignment superfluous. We applied the reflection contrast microscope (RCM) on thick tissue-slides of the cerebral cortex of a patient suffering from Alzheimer's disease which had been dyed according to Campbell. This is a silver-based staining method detecting beta A4-amyloid, the main component of senile plaques. Under the RCM, these silver-stained extracellular amyloid deposits cause reflections which allow the assessment of their three-dimensional distribution by focusing through the specimen. The optical sections obtained in this way were digitized, and the identified senile plaques reconstructed by the grey-scale image analysis system VIDAS 2.5 (Zeiss/Kontron, Germany).

Morphologic quantification of blood platelets by image analysis.

OBJECTIVE: For morphologic and functional investigations on the physiology and pathology of human blood platelets, their adhesion plays an important role. This feature is normally assessed concerning qualitative aspects, but there is a lack of quantitative investigations. STUDY DESIGN: We developed a model to quantify in vitro manipulations on thrombocytes by measuring their adhesion areas automatically. This was achieved by combining the VIDAS 2.5 image analysis system with reflection contrast microscopy (RCM). The evaluation was performed independent of the position of the grey value histogram by analyzing each digitized image corresponding to its individual mean grey value. RESULTS: The applicability and validity were verified from the example of a pharmacologic experiment administering the platelet stimulant oxidized low density lipoprotein (ox-LDL) to thrombocyte suspensions and confirming it by aggregometry. We assessed the temporal increase in adhesion area and mean total adhesion area of activated platelets, comparing unstimulated to stimulated ones. Ox-LDL accelerated the adhesion process and increased the adhesion area. CONCLUSION: The combination of RCM with consecutive image analysis provides useful parameters for in vitro examination on vital human platelets. Large amounts of data can be accumulated in a short time for an evaluation of influences of and on blood platelets.

Qualitative investigations on vital blood platelets by reflection contrast microscopy.

Light-microscopic visualization of vital human blood platelets is improved by reflection contrast microscopy. The light reflected from the specimen causes interference patterns which are used for the assessment of surfaces or adhesion areas. By means of this technique we studied the activation process of unstimulated platelets. During the observation the following two features were assessed: (1) Platelet adhesion areas and their shape change: two main types of adhesion patterns were found for activated platelets. Type A was characterized by flat spreading and extensive adhesion zones, whereas type B showed only focal contacts in the center and long and sometimes dichotomously split pseudopodia. Both adhesion types coexisted in each sample but did not change into one another during the observation period of 25 min. (2) Pseudopodia formation: initially, a rapid evagination of mobile pseudopodia could be observed which lasted for approximately 2 min. After reaching their final individual length, the pseudopodia adhered to the glass and remained stationary.

Entrapment of the lingual nerve due to an ossified pterygospinous ligament.

During a routine dissection course at the University of Muenster (Germany) an unusual course of the lingual nerve was found with entrapment of the nerve between a widely ossified pterygospinous ligament and the medial pterygoid muscle. Furthermore, the nerve's mobility was restricted by a more distal anastomosis with the inferior alveolar nerve. Although incomplete or complete ossification of the pterygospinous ligament is not uncommon, the combination with a medial course of the lingual nerve has not been described before. Besides practical importance for surgeons and anesthetists, the entrapment of the lingual nerve may lead to lingual numbness and pain associated with speech impairment.

Which joint position puts the axillary nerve at lowest risk when performing arthroscopic capsular release in patients with adhesive capsulitis of the shoulder?

The success of arthroscopic capsular release of the glenohumeral joint depends on complete incision of the inferior capsule. This study determined the distance between capsule and the axillary nerve in different joint positions. In 14 human shoulder specimens the anterior joint capsule and axillary nerve were dissected, and the anterior joint capsule was incised between the 1 and 5 o'clock positions. The shortest distance between the insertion of the inferior capsule and the axillary nerve was measured at the glenoid and humeral insertions in abduction, adduction, internal, and external rotation. The axillary nerve is surrounded from soft connective tissue and is closer to the humeral than to the glenoidal attachment of the joint capsule. During abduction and external rotation the nerve stays in its position while the glenohumeral capsule tightens, which increases the distance between the two structures. This results in the following distances: to the glenoidal/humeral capsule insertion: in adduction and neutral rotation, 21.2+/-4.2/14.2+/-2.6 mm; in abduction and neutral rotation, 24.0+/-4.9/15.0+/-5.0 mm; in abduction and internal rotation, 21.1+/-6.6/14.6+/-3.7 mm; and in abduction and external rotation, 24.9+/-3.8/16.4+/-4.4 mm. Thus, when performing arthroscopic capsular release the incision of the glenohumeral joint capsule should be undertaken at the glenoidal insertion in the abducted and externally rotated shoulder.

Decreased adhesion of oxidized LDL-stimulated platelets caused by cytochalasin D.

The adhesion of human blood platelets is studied with an in vitro model using reflection contrast microscopy and an image analysis system. The adhesive feature is promoted by oxidatively modified low density lipoprotein, which also induces functional morphological changes of platelets. However, when washed platelets are pretreated with 0.05 mM cytochalasin D, oxidized low density lipoprotein (100 micrograms/ml) causes a slower increase of the adhesion area (11.6 microns 2/min) compared to untreated platelets (15.7 microns 2/min) or platelets treated by oxidized low density lipoprotein alone (20.5 microns 2/min, P < 0.01). These results are supported by light transmission analysis and by transmission electron microscopy. Our experiments suggest that cytochalasin D inhibits the change of platelets in shape induced by oxidized low density lipoprotein, hinders the adhesion, but does not prevent the adhesion entirely.

[Does the digital signature of the DICOM standard meet the requirements of German law?]. / Entspricht die digitale Signatur des DICOM-Standards dem deutschen Signaturgesetz?

The DICOM standard offers the possibilities to generate electronic signatures, valid according to German laws. This enhances the reliability of the correlation between image and patient data. However, only so called qualified electronic signatures--conveniently issued by an accredited supplier--are permissible and not rejectable as evidence in German jurisdiction and are completely equivalent to the handwritten signatures. These qualified electronic signatures can be executed only by individuals, whereas the former are not applicable to technical apparatus like image generating modalities. In consequence, a modality is able to provide its pictures with a "common or advanced signature" solely. This limits the use of the digital signature of the DICOM standard for further applications, e.g. the verifiability within the teleradiology.

Reflection contrast microscopy within chrome-alum haematoxylin stained thick tissue-sections.

This paper introduces two innovations in reflection contrast microscopy (RCM): (1) an extended application for qualitative light microscopic investigations; and (2) a novel method for quantification in cytochemistry. (1) We found out that RCM cannot only be used for surface characterizations and in thin sections but also within thick tissue-sections. The use of the RCM technique is demonstrated on slides of the supraoptic nucleus (SON) of the rat stained with chrome-alum haematoxylin: Among all the stained structures only neurosecretory granules are found to cause reflections. The visualization of the neurosecretion and its distribution is more distinct and of sharper contrast than in bright field microscopy. (2) The improved differentiation allows the quantification of neurosecretion in tissue-sections by combining RCM with grey-scale image analysis.