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Biomedical subjects

B Krug

Publications and source records attributed to B Krug.

At least 37 records · Page 2Linked to original sources
PubMed2001

Image quality of digital chest X-rays: wet versus dry laser printers.

The aim of this study was to compare the image quality of digital chest x-rays (Thoravision) obtained with 2 "wet" laser imagers of different matrix sizes and a "dry" system. Fifty chest x-rays in 2 planes were printed out in normal (100%) and reduced (61%) format using 3 different systems: 2 "wet" laser imagers (Agfa Matrix LR 3300, 4256 x 5174 pixels, 315 dpi; Agfa Scopix LR 5200, 8512 x 10348 pixels, 630 dpi), and one "dry" system (Agfa Drystar 3000,4352 x 5295 pixels, 330 dpi). All tests yielded normal findings. Anonymous images were evaluated by 4 independent reviewers on record forms rating the detectability of predefined anatomic structures. When the image quality of diagnosis-relevant, anatomic structures was evaluated on digital chest x-rays reproduced in normal and reduced format, the wet laser imagers did not show significant advantages over the dry system, Agfa Drystar 3000. The Agfa Drystar 3000 system is a feasible alternative for reproducing digital images, particularly for decentralized archives.

Adult↗
PubMed2001

Functional magnetic resonance imaging of human pontine auditory pathway.

The purpose of this study is to visualize brainstem auditory pathways by functional magnetic resonance imaging (fMRI). Eighteen healthy volunteers (age 28 to 42 years) with normal hearing function underwent fMRI examination on a 1.5 Tesla imaging system (Philips, Best, The Netherlands) with periodic click stimulation. Blood oxygen level dependent images were obtained using a three-dimensional EPI sequence with shifted echo technique (principles of echo shifting with a train of observations). Control scans without click stimulation were obtained in the identical setting. Cross correlation activation maps were calculated using a postprocessing tool (Philips). They were matched with anatomic slices of identical orientation and thickness. Five of 18 subjects were excluded because of motion artifacts. In 4/13 significant activation was observed at the root entry zone of the ipsilateral acoustic nerve corresponding to the cochlear nuclei. In 11/13 subjects, significant activation was found in the same slice contralaterally close to the floor of the 4th ventricle, corresponding to the expected region of the superior olivary nucleus. Activation of the rostral parts of the auditory pathway (inferior colliculus, medial geniculate body) was not found. In the absence of the stimulus no activation occurred in these structures. It was concluded that activation of the brainstem auditory pathways by click stimuli can be visualized by fMRI.

Acoustic Stimulation↗
PubMed2001

Use of an image-guided navigation system in dental implant surgery in anatomically complex operation sites.

INTRODUCTION: Recent developments in computer assisted surgery have brought major improvements to maxillofacial surgery. Computer systems for intra-operative navigation have been introduced enabling the surgeon to locate the continually updated position of the instruments and the operation site on the patient's three-dimensional reconstructed image data set displayed on a monitor in the operating room. Complex surgical procedures can be performed according to the preoperative plan based on CT and/or MRI data minimizing surgical risks and optimizing clinical results. Nowadays computer-assisted-surgery has also proved effective in dental implantology. AIM: The objective of this study was to compare the accuracy of conventional and computer-assisted dental implantation planning and surgery. Analyzing our early experiences, we aimed to evaluate the benefit from utilising computer assisted surgery (CAS). PATIENTS: Five patients were treated with the aid of CAS, a total of 18 dental implants being placed. Only difficult operation sites, e.g. following bone augmentation or anatomically malformed jaws were included in this study. METHOD: An infra-red light based navigation system (Vector Vision 2, BrainLAB, Munich, Germany) including a three-dimensional planning approach for maxillofacial surgery was used. Placement of dental implants in the maxilla included direct visualization when drilling the implant socket according to the axis previously planned on radiographs and CT scans. RESULTS: In two cases the conventionally planned implant location had to be changed due to insufficient bone being available. With four implants, it proved possible to insert longer fixtures after the CAS system had evaluated all parameters of the surgical region. In one case a shorter implant was installed due to insufficient bone at the designated location. CONCLUSION: The use of an image-guided navigation system provides a valuable tool in implant dentistry and proved superior to conventional implant surgery especially in difficult anatomical regions.

Alveolar Ridge Augmentation↗
PubMed2001

Image guided surgical navigation for removal of foreign bodies in the head and neck.

INTRODUCTION: The removal of foreign bodies in the head and neck area is often a surgical challenge due to a combination of difficult access and a close anatomical relationship of the foreign body to vital structures. Recent developments in computer-assisted surgery (CAS) have brought major improvements to the operating rooms for maxillofacial surgeons. The purpose of this paper is to report our experience in computer assisted removal of foreign bodies from the head and neck area, based on various clinical cases. PATIENTS: Computer assisted removal of foreign bodies from the head and neck area was performed in 11 patients. Three patients sustained gun shot wounds with remaining projectiles or fragments in the soft tissue. In six cases, objects related to a preceding surgical intervention were removed. Two patients presented with dislocated teeth in the facial or cervical soft tissues after 3rd molar surgery. METHOD: For surgical planning and intra-operative navigation, a computer based image guided surgery system (VectorVision(2), BrainLab) was used. RESULTS: In 10 of 11 cases the foreign bodies could be removed without major complications by a minimal invasive manner. More than 40 % of surgery time could be saved compared to similar interventions operated upon using conventional methods. CONCLUSION: In our opinion, the use of a computer based image guided surgical system is of great benefit when removing foreign bodies from the head and neck area. The minimally invasive access helps to prevent major complications such as injury to vital structures and allows a quicker operation.

Adolescent↗
PubMed2001

[Comparison of digital selenium radiography with an analog screen-film system in the diagnostic process of pneumoconiosis according to ILO classification].

UNLABELLED: Comparison of digital selenium radiography with an analog screen-film system in the diagnostic process of pneumoconiosis according to ILO classification. PURPOSE: The aim of the study was to determine the diagnostic value of digital selenium radiography in patients with pneumoconiosis. For this purpose chest x-rays by digital selenium radiography and analog screen-film system were compared according to the ILO classification of pneumoconiosis. METHOD: After approval of the study by the local ethic commission and the Federal German Office for Radiation Protection 50 patients were subjected to x-rays by digital selenium radiography (Thoravision; Philips Medical Systems, Hamburg, Germany) and analog screen-film system of the same day within the scope of an industrial medicine preventive checkup. Four investigators rated the chest x-rays according to the ILO classification of pneumoconiosis. RESULTS: The findings demonstrated by chest x-rays according to ILO classification were rated similar by digital selenium radiography and analog screen film systems. Image quality of the digital pictures was rated significantly better. CONCLUSION: The use of digital selenium radiography in evaluating chest x-rays according to the ILO classification does not result in over- or underestimation of pulmonary pathologies. Hence, in the diagnosis of pneumoconiosis, digital selenium radiography can replace the tested analog screen-film system.

Adult↗
PubMed2001

[Artifacts in MR Imaging due to ventilation tubes].

UNLABELLED: Artifacts in MR Imaging due to ventilation tubes. PURPOSE: MR examinations may be necessary in patients under artificial ventilation. Possible imaging artifacts originating from ventilation tubing made from silicone are demonstrated. MATERIALS AND METHODS: In silicone carbohydrate residues are bound to silicon atoms. In silicone gels they give strong signals in MR imaging. MR signals from more solid silicone rubber are only possible if the carbohydrate residues in the molecular chain retain a sufficient mobility. To investigate whether silicone tubes give signals in MR images, different tubes for ventilation made from silicone and polyester were examined at 1.5 T (Gyroscan ACS NT, Powertrak 6000 gradients) with MR imaging and spectroscopy (MRS: PRESS, TE = 20 ms; relaxation time measurements: MIXED sequence; imaging: FFE [gradient echo] and TSE sequences). RESULTS: Using short TE (</= 4 ms), tubes and sockets made from silicone could be imaged with FFE and SE sequences. An SE sequence with a short TE = 4 ms provided a sufficient signal intensity to depict the tube clearly besides brain tissue of a volunteer. When foldover occurred, the signal of the tube was projected onto the brain tissue. MR spectra confirmed that the image signal originated from the carbohydrate residues of the silicone molecule chains, not from residual water in the tube wall material. T(2) determinations indicate a multiexponential relaxation including a large component with a short TE (</= 15 ms). Tubes made from a polyester elastomere did not show up in MR images. CONCLUSION: In MR images acquired with very short echo times silicone in ventilation tubes may produce significant artifacts.

Adult↗
PubMed2001

Detection of porcine bone lesions and fissures: comparing digital selenium, digital luminescence, and analog film-screen radiography.

OBJECTIVE: The purpose of our study was to compare the diagnostic performance of a digital selenium detector (Thoravision) with that of analog film-screen systems and digital luminescence radiography in skeletal radiography for the detection of fissures and lesions in porcine bones. MATERIALS AND METHODS: One hundred bones taken from domestic pigs (50 ribs and 50 femurs) were divided into two equal groups. Fissures and bone lesions were created in 50 bones and 50 served as controls. The bones were examined using film-screen systems, digital luminescence radiography, and digital selenium radiography at various doses. Digital selenium radiography exposure values were adapted to the image geometry differing from the reference methods with a detector focus distance of 2.15 m. Four radiologists independently evaluated image quality and detectability of fissures and lesions on a five-point scale of confidence. Statistical evaluation was based on receiver operating characteristic curve analysis. RESULTS: Fissures and bone lesions were detected most reliably using the mammography film-screen system, but the difference in the results of the analog and digital reference images did not achieve statistical significance. CONCLUSION: Compared with analog film-screen systems, the lower spatial resolution of the digital selenium and digital luminescence radiography systems does not affect detectability of fissures and bone lesions in porcine bone. Selenium is effective in skeletal radiography for detecting fissures and bone lesions. With digital selenium and digital luminescence radiography, the surface dose can be cut to half that required for 200-speed film-screen systems without losing any diagnostically relevant information.

Animals↗
PubMed2001

Inadequacies of repeated radiological examinations in a university hospital.

PURPOSE: To establish why 16% of 1,045 patients undergoing abdominal and/or vascular surgery referred to the University Department of Radiology for a B-image sonogram reported that a US of the same regions of the body had been conducted during the previous 6 weeks without any changes in the clinical status. STATEMENT OF THE PROBLEM: Evaluation of the reasons for these superfluous examinations and analysis of the consequences that the US follow-up examinations implied for the patient. MATERIAL AND METHODS: One senior resident radiologist and one senior resident surgeon reviewed the medical records of the patients reporting previous examinations and examinations scheduled at the time of the questioning of the patients. RESULTS: One hundred and eight (63%) of the 171 medical records were available. Data on previous examinations mentioned in the report forms were incorrect in 14 cases (13%). Therefore, further evaluations were based on 94 patients. Ten (8%) out of 121 sonograms, 4 (10%) out of 40 CT and 2 (20%) out of 10 MR investigations documented in the medical records had not been mentioned by the patients. As many as 41 (75%) of the 55 preliminary sonograms performed by general practitioners and specialists in private practice were not documented in the medical records. Even though records existed of clinically plausible findings, 36 (84%) of the 43 preliminary US investigations performed by doctors in the University Hospital were repeated to verify the diagnosis without any further diagnostic benefit. CONCLUSION: A cross-speciality consensus over the diagnostic value of B-image sonography and management of the findings obtained is of paramount importance.

Abdomen↗
PubMed2000

[Treatment outcomes in primary and secondary retroperitoneal fibrosis].

Retroperitoneal fibrosis (RPF) is an uncommon inflammatory disease of the retroperitoneum leading to extensive fibrosis with consecutive obstruction of adjacent organs, namely the ureters. Since no consensus on the standard therapy exists, aim of the current study was to evaluate the outcome of 39 patients with RPF. Between 1986 and 1997 39 cases of RPF were diagnosed: 21 cases had primary RPF and 18 patients had secondary RPF after aortofemoral graft (n = 13), radiation (n = 2), or prior retroperitoneal surgery (n = 2). 21 patients demonstrated unilateral and 16 cases had bilateral hydronephrosis, in 2 patients no dilatation was observed. In 28 cases (n = 12 primary RPF, n = 16 secondary RPF) initial management consisted of DJ-stent placement, whereas in 11 cases (n = 9 primary RPF, n = 2 secondary RPF) percutaneous nephrostomy had to be placed. All patients received oral immunosuppressive agents (prednisolone 1 mg/kg, azathioprine 1 mg/kg/day) for 3 months before reevaluation was performed. In case of complete remission, immunosuppressive medication was continued for another 3 months, in case of stable disease or progression surgery was performed. In 26 cases (n = 15 primary RPF, n = 11 secondary RPF) ureterolysis with intraperitoneal displacement and omental wrapping was performed. 3 patients demonstrated complete remission after oral prednisolone/azathioprine; in 2 cases RPF presented as pelvic mass and was resected followed by immunosuppressive therapy, in another 2 cases bilateral ileal replacement of the ureters had to be performed and 4 cases remained on DJ-stents and nephrostomy, resp. Postoperatively, all patients with primary RPF were continued on immunsuppressive medication for another 3 months. After a follow-up of 6 to 120 months only 3 patients developed a retroperitoneal recurrence and were treated by unilateral nephrectomy or DJ stent placement (n = 2). Our data suggest that the combination of both immunosuppressive medication and surgical management results in an excellent longterm outcome in idiopathic retroperitoneal fibrosis with a recurrence rate of only 8%. Combination therapy should be considered as therapeutic option early in the course of the disease. Primary reconstructive surgery appears to be the most promising approach in secondary retroperitoneal fibrosis with a recurrence rate of only 5%; short external compression of the ureter might be managed by endoluminal balloon dilatation.

Adult↗
PubMed2000

[Indications and rate of repeat studies in the color duplex department of a radiology university clinic].

PURPOSE: Who refers patients for a color duplex ultrasonography (CDUS) in the routine work of a radiological university department and how frequent are repeat examinations? MATERIAL AND METHODS: 1110 patients had at least one CDUS examination between 5/97 and 5/98. The specialities of the referring physicians/primary examiners and the inpatient or outpatient status of the patients were documented at the first consultation. Additionally the patients were asked by the medical staff, whether, how often, and by whom ultrasonographic, CT, or MR examinations of the same organ system had been carried out during the last 4 weeks without evidence of any clinical changes. RESULTS: 97% of the 1118 patients were referred by one of the university departments. The arterial system was exclusively investigated in 58% and the venous system in 29% of the cases. 81% of the 651 arterial examinations were requested by the Departments of Vascular/Cardiac Surgery and Radiology. 75 repeated ultrasonographic examinations were documented in 67 (6%) of the 1118 consultations. Repetitions were documented in 8% of the arterial and in 3% of the venous examinations. X-ray angiographies were already done or planned in 105 of the 625 arterial CDUS (16%). Ultrasonographic referrals with parallel phlebographies (1% of 320 venous indications) as well as parallel CT and MR examinations (1% of the 1118 consultations, respectively) were the exception. CONCLUSIONS: In the described setting, CDUS was mainly used to assess the arterial vascular system prior to vascular surgery and radiological interventions. Repeat ultrasonographies alone (6%) and parallel examinations altogether (14%) were observed less frequently than expected.

Adolescent↗
PubMed2000

[Precision of MRI-guided needle placement--experimental results].

PURPOSE: To estimate the accuracy of the determination of tip position of MR compatible biopsy needles based on signal voids and artifacts in MR guided biopsies. METHOD: In a nylon grid phantom an MR compatible 18G needle (E-Z-EM) was measured in a 1.0 T imager using TSE- and FFE-sequences of 20 s and 40 s duration in 34 different orientations of needle versus B0, frequency and slice selection gradient. 4 radiologists with no experience in the evaluation of signal void artifacts estimated the needle tip positions from needle tip artifacts. The readers determined the needle tip before and after a 15 minute training session based on high resolution images with explanation of size and shape of specific artifacts of biopsy needles in 12 different orthogonal or parallel orientations to B0 and frequency encoding gradient that are possible if the needle lies parallel to the slice, i.e. orthogonal to the slice selection gradient. The values obtained before and after the training session were compared to the real position of the needle tip. RESULTS: Mean distance of actual needle tip and tip position as determined from images was 1.8 +/- 2.3 mm in TSE-versus 2.5 +/- 1.2 mm in FFE-images, with the needle length overestimated. After a 15 minute training session the positioning error decreased significantly to 0.2 +/- 1.8 mm for TSE-sequences and to 1.0 +/- 1.8 mm for FFE-sequences. A higher accuracy of tip localization was obtained with TSE sequences. CONCLUSION: In MR guided biopsies using FFE- and TSE-sequences the needle position can be more accurately determined if the reader is familiar with the 12 orthogonal or parallel positions of the needle with respect to B0 and frequency encoding gradient and the corresponding artifacts.

Artifacts↗
PubMed2000

Fluor-18-fluorodeoxyglucose positron emission tomography (FDG-PET) in malignant melanoma. Diagnostic comparison with conventional imaging methods.

PURPOSE: To assess the diagnostic value of fluor-18-fluorodeoxyglucose positron emission tomography (FDG-PET) in screening for melanoma metastases. MATERIAL AND METHODS: The case records of 94 melanoma patients who had been examined by whole-body FDG-PET between 1995 and 1999 were evaluated retrospectively. Forty patients showed evidence of lymphogenous and 42 of hematogenous metastasis. The maximal interval between PET and the diagnostic procedure under comparison was 2 weeks. Confirmation of the findings was based on histology or the clinical or radiological course. RESULTS: In 24 patients, all diagnostic examinations including CT had been performed within 2 weeks from PET. In no case did PET change the staging. In 13 patients, PET agreed with morphological diagnosis in the number of metastatically invaded organs. This included 3 patients without metastases. The estimated number of organs invaded by metastases was higher with PET in 5 patients and higher with morphological imaging techniques in 6 patients. Among the PET findings with higher or equivocal counts of organs with metastases there were 2 confirmed false-positive findings. CONCLUSION: In a selected patient population, FDG-PET was found to be inferior to CT for diagnosing lung and liver metastases. The supplementary use of FDG-PET is not generally of value once metastasis has been established.

Abdomen↗
PubMed2000

MRA in patients with cerebrovascular disease. Considerations of clinical effectiveness.

OBJECTIVE: To establish in which clinical contexts cerebral MR angiography (MRA) is routinely carried out in a neurological university department and to describe its clinical impact. MATERIAL AND METHODS: Medical records, reports of findings and documentation of imaging examinations carried out in all 69 patients referred to the Department of Radiology from the Department of Neurology between 1995 and 1998 for cerebral MRA were evaluated. The clinical impact of all imaging findings was assessed on the basis of the medical records. RESULTS: Circulatory disturbances in the vertebrobasilar arteries (n = 34) were the most frequent indication for investigation. MRA followed CT or duplex sonography in 66 of the 69 patients with a mean delay of 8 days. MRA was considered diagnostically inferior to conventional MR in 11 cases, comparable in 30 and superior in 25. Comparing MRA and duplex sonography, the corresponding figures were 12, 29 and 23. In retrospect, 56 MRAs were judged unnecessary. CONCLUSION: Controlled clinical studies on optimal use of MRA are needed to avoid wasting resources and to exploit the method's full diagnostic potential in appropriate cases.

Adult↗
PubMed1999

[Frequency of repeated examinations in the ultrasonographic section of a radiological university department].

PURPOSE: What is the percentage of repeat examinations in the ultrasonographic section of a radiological university department? METHODS: All 4116 patients, who were first examined in the sonographic section of the Radiologic Department of the University of Cologne from 5/97 to 5/98, were asked by the medical staff, whether, how often and by whom ultrasonographic, CT or MR examinations of the same organ system had been carried out during the last 4 weeks without evidence of clinical changes. The data were documented using a structured questionnaire. RESULTS: Sonographic repeated examinations documented in 443 (10.8%) of the 4116 consultations. The proportion of in- to outpatients with repeat examinations was 26.0% to 74.0%. Contrarily, the repeated ultrasonographies were done by practitioners in 62.3% and by the university staff in 33.2% (radiology 48.2%). With regard to the 4116 consultations, the abdomen (81.1%) was the organ system most often examined repeatedly. Computed tomographies were already done or planned in 305 of 4116 patients (7.4%) and MR-tomographies were already done or planned in 57 patients (1.4%). CONCLUSION: The rate of repeated ultrasonographic examinations in a radiological university hospital was 19.6%.

Abdomen↗
PubMed1999

Positron emission tomography using 18F-fluorodeoxyglucose in advanced stages of malignant melanoma: a comparison of ultrasonographic and radiological methods of diagnosis.

The diagnostic and therapeutic impact and the cost-effectiveness of positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) will depend on the role for which the tests are used. In 68 patients with advanced malignant melanoma, original sets of FDG-PET images from various institutes were compared with findings obtained by ultrasonography, conventional radiology, computed tomography (CT) and magnetic resonance imaging. In 22 patients, all examinations were undertaken within 2 weeks and strategies of staging were analysed. In 46 patients, only some of these examinations were performed within this time period, and comparison of methods was restricted to the examined organs. The occurrence of metastasis, without specifying the number of foci, was detected by either conventional staging with CT or by PET in 20 of 22 patients. None of these patients were up- or down-staged by FDG-PET compared with CT staging. In the 68 patients as a whole, FDG-PET detected fewer pulmonary and hepatic metastases and fewer cerebral foci, but more lymph node and bone metastases than conventional radiology or CT. For the detection of lymph node or skeletal metastases, false-positive FDG-PET findings were taken into account when compared with follow-up data. In advanced melanoma, FDG-PET did not influence the pattern of subsequent diagnostic testing. Thus, indications for FDG-PET include pre-metastatic melanoma, localized lymph node metastases and monitoring of the response to treatment.

Adolescent↗
PubMed1999

[The lymph node staging of malignant testicular germ-cell tumors].

Imaging procedures are important in the initial staging and subsequent management of testicular germ cell tumors on account of the differing stage-dependent options for therapy. While the diagnosis of advanced tumors gives no cause for controversial discussion the situation in the clinical stage 1 of germ cell tumors is more ambiguous. The lymph node status is only assessed correctly in about 70% of the patients using the currently available methods since metastases in normally large lymph nodes are not detected on slice images. Although most clinical experience has been gained with computed tomography (CT), magnetic resonance imaging (MRI) offers an equally efficient diagnostic procedure. The significance of positron emission tomography with 18-fluorodeoxyglucose (FDG-PET) appears to be limited on account of the absence of accumulation in lymph node metastases of the differentiating teratoma. Sonography and lymphography have not proved to be useful for retroperitoneal lymph node diagnosis. The present review presents and discusses the current value of the available imaging procedures for staging and follow-up of malignant testicular germ cell tumors in relation to modern therapy regimens.

Adolescent↗
PubMed1999

[The Cologne Guidelines Conference: computer-assisted clinical practice guidelines in clinical diagnosis].

Eighteen clinical practice guidelines on interdisciplinary diagnostic issues were developed at the University Hospital of Cologne, Germany. The guideline committee is organized and directed by the quality control program, which also includes the local Cochrane initiative and a wide range of organizational topics. During guideline development, questions of differential diagnosis were addressed to the same extent as the organizational and financial realization. Broad consideration was given to medicolegal implications, but need for interspecialty cooperation was judged to be more critical and even more relevant in this regard. Guidelines were primarily developed as algorithms and translated to text versions secondarily. Critical steps in the decision tree were supported by rated literature and recommendations weighte by criteria as used in evidence-based medicine. For implementation, guidelines were presented to colleagues in a series of short lectures, as print versions containing all literature used in the developing process, and in hypertext format, which is accessible via intranet. Three levels of presentation were chosen in the html-version: algorithm, decision, and information. The former is due to orientation in the guideline, the second displays the binary question, and the latter makes the scientific background available, together with literature and links for more information. Efforts to check effectiveness are currently been made, questions of efficiency will be addressed in future.

Algorithms↗