Biomedical subjects
Publications and source records attributed to N Holzknecht.
For the first time we describe a sclerosing mesenteritis that appeared acutely after abdominal operations. The patient suffered from diffuse abdominal symptoms. There was a hard tumour in the left middle and lower abdomen. Histological analysis revealed fibrosis and bone tissue. Symptoms improved after application of prednisone and high-calorie infusions.
PURPOSE: To compare the efficacy and quality of conventional and MR enteroclysis with different filling methods regarding the assessment of extension and extraluminal manifestations in Crohn's disease. MATERIAL AND METHODS: 190 patients with known Crohn's disease were studied following small bowel enteroclysis, after oral administration or direct transduodenal filling in the MRI-department.T1- and T2-weighted breathhold MRI-scans w/o spectral fat suppression w/o i.v. Gd-DTPA were applied using negative oral superparamagnetic contrast media. RESULTS: Typical findings were marked bowel wall thickening with laminated wall contrast enhancement. In 135 patients 98,2% of affected bowel segments, 97,5% of stenoses and all 16 fistulas were detected, when conventional enteroclysis was employed as standard of reference. Additional important extraluminal findings such as ileoileal (n = 18), ileosigmoidal adhesions (n = 12), extraluminal abscesses (n = 35) and pseudotumors (n = 8) were visualized in 73/135 patients. Concerning the distension of jejunum and ileum, oral filling was rated significantly inferior to transduodenal filling in all small bowel segments,whereas filling in the MRI-unit was rated superior to fluoroscopic, mostly due to a mean transport time of 20 min to the MRI-unit. CONCLUSION: No clinically important findings of enteroclysis were missed when using MRI. Therefore, in patients with Crohn's disease, conventional enteroclysis can be replaced by MRI. For optimal bowel distension oral contrast administration is inferior to transduodenal filling, if a larger time delay between filling and the MRI-scan can be avoided.
OBJECTIVE: The aim of our study was to compare the signal-to-noise ratio and the diagnostic accuracy of moving-table MR angiography of the peripheral arteries with body coil and dedicated phased array coil systems. SUBJECTS AND METHODS: Forty patients were examined with digital subtraction angiography and moving-table MR angiography with a 1.5-T MR imaging system either with a body coil (n = 20) or with a dedicated phased array coil (n = 20). The timing of contrast material was performed with real-time MR fluoroscopy. RESULTS: For the iliac artery, upper leg, and lower leg, the mean values for signal-to-noise ratios were 56, 51, and 17, respectively, for the body coil, and 54, 74, and 64, respectively, for the dedicated phased array coil. For the body coil, sensitivity and specificity in identifying stenosis greater than 50% and occlusions were 100% and 96%, respectively, for the iliac arteries, and 100% and 96%, respectively, for the upper leg. For the dedicated phased array coil, sensitivity and specificity for stenosis greater than 50% and occlusions were 100% and 96%, respectively, for the iliac arteries, and 100% and 98%, respectively, for the upper leg. Sensitivity and specificity were inferior for the body coil (88% and 85%) compared with the dedicated phased array coil (100% and 96%) in the lower leg. A significant difference of the mean values of contrast-to-noise ratio was found before and after subtraction for the dedicated phased array coil and body-coil techniques (Student's t test, p < 0.01). CONCLUSION: In comparison with the body coil, the dedicated peripheral phased array surface coil system improves signal-to-noise ratio for the upper and lower leg and diagnostic accuracy in the lower leg.
PROBLEM: Health care delivery in Germany has to face severe challenges that will lead to a closer integration of services for in- and out-patients. University hospitals play an important role due to their activities in research, education and health care delivery. They are requested to promote and evaluate new means and ways for health care delivery. METHODS: The Institute of Clinical Radiology at the University Hospital of the Ludwig-Maximilians-University started teleradiological services for hospitals and general practices in January 1999 in the framework of the "Imaging services--teleradiological center of excellence". Legal, technical and organizational prerequisites were analyzed. RESULTS: Networks between university hospitals and general practices are not likely to solve all future problems. They will, however, increase the availability of the knowledge of experts even in rural areas and contribute to a quality ensured health care at the patients home. Future developments may lead to international co-operations and such services may be available to patients abroad. CONCLUSION: Legal, technical and organizational obstacles have to be overcome to create a framework for high quality telemedical applications. University hospitals will play an important role in promoting and evaluating teleradiological services.
PROBLEM: How are improvements in productivity in connection with RIS/PACS to be defined? What do they cost? To limit the problem to the relevant topics, we first describe the objectives of a radiology department and the identified bottlenecks in the workflow. How to define and assess the improvements is discussed. METHODS: The case in question for this study is the RIS/PACS project at the "Klinikum der Universität München, Campus Grosshadern". The goals of the project and its present status are reviewed. The project is not yet completed, so this is a "midterm" report. RESULTS AND DISCUSSION: We describe the status of the achieved and not yet achieved goals and of the eliminated bottlenecks. On the plus side, for example, nearly 100% of all digitally generated images (except mammogramms) are digitally archived. They are accessible to the same percentage in radiology via PACS and in the hospital via the webbased intranet image distribution system when needed. In some radiology areas, such as multislice CT, already the reporting can no longer be performed without softcopy image interpretation. However, the full elimination of hardcopy images is still not reality, since the distribution to DICOM viewers for selected requesters with demands for almost reporting quality, high cost image displays is still in the testphase. To reduce film costs, images are being printed on a high resolution paper printer in addition to the intranet distribution during this transition period. On the negative side, due to a lack of job positions in the transcription rooms, about 40% of the reports are still being handwritten by radiologists. Furthermore, the dictated and transcribed reports are usually still not available early enough in the RIS and thereby in the intranet report distribution of the hospital. Here only a speech recognition system can remedy the situation. As soon as this problem is solved and the image distribution to the DICOM viewers works routinely, the reports and the images will be accessible within minutes to maximally within some hours after the examination. CONCLUSION: The goals reached so far suffered delays due to unforeseen problems and pitfalls. Altogether, a quieter operation and workflow in radiology has already been achieved, due to less inquiries from the requestors for unfinished examinations, images and/or image copies.
There is little information about the effects of extracorporeal shock-wave application (ESWA) on normal bone physiology. We have therefore investigated the effects of ESWA on intact distal rabbit femora in vivo. The animals received 1500 shock-wave pulses each of different energy flux densities (EFD) on either the left or right femur or remained untreated. The effects were studied by bone scintigraphy, MRI and histopathological examination. Ten days after ESWA (0.5 mJ/mm2 and 0.9 mJ/mm2 EFD), local blood flow and bone metabolism were decreased, but were increased 28 days after ESWA (0.9 mJ/mm2). One day after ESWA with 0.9 mJ/mm2 EFD but not with 0.5 mJ/mm2, there were signs of soft-tissue oedema, epiperiosteal fluid and bone-marrow oedema on MRI. In addition, deposits of haemosiderin were found epiperiosteally and within the marrow cavity ten days after ESWA. We conclude that ESWA with both 0.5 mJ/mm2 and 0.9 mJ/mm2 EFD affected the normal bone physiology in the distal rabbit femur. Considerable damaging side-effects were observed with 0.9 mJ/mm2 EFD on periosteal soft tissue and tissue within the bone-marrow cavity.
The purpose of this study was to evaluate the performance of standard-dose and low-dose cesium iodide (CsI)-doted amorphous silicon (a-Si) flat-panel detector technology (FDT) as compared with storage-phosphor technology (SPT) in the depiction of relevant anatomical structures in chest radiography. In 75 patients referred for thoracic CT, digital chest radiographs were randomly obtained with either SPT at a standard dose (speed class S400, n=25), standard-dose FDT (S400, n=25) or FDT at a low dose (S800, n=25). Five radiologists evaluated the visibility of eight pulmonary and mediastinal anatomical structures using a five-point rating scale. To determine statistically significant differences between the three groups, the Mann-Whitney U-test was employed. No statistically significant differences were found in the depiction of eight criteria between SPT and standard-dose or low-dose FDT chest radiographs. The performance of FDT S400 was equal to SPT for most criteria and better for retrocardiac structures and soft tissue. FDT S800 was inferior to both SPT and FDT S400. Standard-dose FDT is equivalent to SPT in the depiction of relevant anatomical structures of the chest. Our results also indicate that a dose reduction of 50% with FDT may result in small but not significant decrease of image quality.
The aim of this study was to investigate the value of a contrast-enhanced 3D MR angiography in detecting postoperative vascular complications after kidney transplantation in comparison with digital subtraction angiography (DSA). Forty-one patients who underwent a kidney transplantation were examined with MR angiography and DSA. Contrast-enhanced MR angiography was performed as a dynamic measurement with one precontrast and three postcontrast measurements. Maximum intensity projection reconstructions were performed for all postcontrast data sets after DSA. The results were evaluated by two independent observers who were unaware of the DSA results. Twenty-three hemodynamically significant arterial stenoses were identified with DSA in the iliac arteries ( n=7), the renal allograft arteries ( n=12), and in their first branches ( n=4). For a patient-based analysis the sensitivity and specificity, respectively, for observer 1 were 100 and 97%, and for observer 2, 100 and 93%. Respective data were 100 and 100% after a consensus evaluation by two observers. Complications involving the renal veins were detected in 2 cases and perfusion defects of the kidney parenchyma were detected in 4 cases. Contrast-enhanced MR angiography is a reliable method in identifying postoperative arterial stenoses after kidney transplantation. In addition, dynamic MR angiography can be helpful in detecting venous complications and perfusion defects in kidney allografts.
Primary and secondary malignant hepatic tumors are the most common tumors with a much more higher incidence of hepatic metastases. Chemotherapy and radiation therapy are in general ineffective. Therefore, surgical resection is considered the method of choice in the treatment of malignant hepatic lesions. Due to systemic disease, general medical or procedure-related reasons hindering surgery, only 25 to 45% of the patients with metastatic disease of the liver are suitable for a curative surgical therapy. In resectable lesions thermoablative methods can offer an alternative to the surgical therapy. The most experience exists in radiofrequency ablation techniques. Technique, indications, contraindications, and limitations of the radiofrequency ablation will be discussed together with a presentation of own cases and a review of the literature. In 37 patients the primary technical success rate of the ablation was 97.3% (72 of 74 lesions). In 4 cases a hematoma of the liver capsule occurred. One of these had to be treated interventionally. During the limited follow-up period of 9 months no local recurrency was seen, however 4 patients developed new hepatic metastases. Beside differences in practicability it is not yet clarified if there are differences in the therapeutic efficacy of the different thermoablation methods. Nevertheless, the results of the ablation therapy may parallel the results of the surgical resection. Interstitial thermotherapy can provide a valuable contribution to local tumor control. However, the final significance of the thermoablation techniques within oncological therapy regimens has to be evaluated in further multidisciplinary studies.
PURPOSE: Evaluation of the accuracy of a new electromagnetic target system for interventional CT-guided procedures with virtual navigation in a previously acquired helical CT. MATERIAL AND METHODS: The new target system CT-Guide 1010 (Ultraguide, Tirat Hacarmel, Israel) for CT-guided interventions was adapted to the video signal of the Somatom Plus 4 and Volume Zoom (Siemens, Erlangen, Germany). A helical CT-dataset including skin-based sensor cubes was transferred to the integrated navigation system inside the scanner room. 50 image-guided interventions and biopsies were performed outside the gantry using virtual navigation to reach the lesion. The accuracy of the procedures was evaluated using documentation of the needle tip with CT-fluoroscopy, results of histology, and follow-up. RESULTS: The deviation between planned and documented needle tip was 2.2 +/- 2.1 mm in 50 procedures. Time between the end of planning-CT and needle positioning using the system was 13 minutes. There were no complications due to the use of the system. CONCLUSION: The CT-Guide allows for virtual real-time navigation with high accuracy. Advantages are the free needle angulation without gantry tilt, use of optimal CT perfusion phase for virtual navigation, and reduction of radiation exposure to the patient and interventionalist.
PURPOSE: To compare high resolution contrast-enhanced MR angiography (MRA) and digital subtraction angiography (DSA) in the assessment of supraaortic vessel stenosis. METHODS: 14 patients with suspicion of cerebrovascular disease or upper limb ischemia underwent selective DSA and high resolution contrast enhanced MRA employing a new Panoramic-Array coil. Stenosis assessment in comparison to DSA followed NASCET criteria. Additionally signal-/noise ratios (SNR) were evaluated to assess contrast enhancement. RESULTS: Diagnostic image quality was achieved in all patients. Sensitivity and specificity for assessing high-grade stenosis of the supraaortic vessels were 100% and 96% respectively. In the assessment of high-grade common or internal carotid artery stenosis sensitivity and specificity was 100%. CONCLUSION: High resolution contrast enhanced supraaortic MRA combined with new coil systems allow for a reliable assessment of stenoses along the whole vessel course including the aortic arch. Previous stent procedures limit its use in postinterventional follow-up.
PURPOSE: The value of elective PTA in stenoses of the supraaortic vessels and especially of the carotid artery is still under discussion. Stenoses after surgical and/or radiation therapy and a high cardio-vascular risk for a surgical procedure, however, justify minimal-invasive techniques. MATERIAL AND METHODS: In 31 patients with 24 symptomatic and 7 asymptomatic stenoses of the supraaortic arteries (3 Acc, 19 Aci, 5 Ascl, 4 Tr.brc, 2 Aax) minimal-invasive angioplasty and stent-placement was performed. The rationale for the interventional procedure was an elevated medical or technical risk of the respective surgical procedure. All procedures were performed using a coaxial technique with a guiding catheter. An open vascular access was necessary in 7 cases due to an unfavorable anatomical situation. RESULTS: The technical success rate was 100%. Peri-interventionally, a TIA occurred in 2 patients (1 spontaneous relieve, 1 complete remission after rt-PA lysis therapy). During the mean follow-up period of 13 months 3 patients died due to non-cerebrovascular reasons. In 2 patients a moderate restenosis, in 1 a high-grade stenosis, and in 1 and complete occlusion occurred without symptoms. After one year of follow-up, all treated stenoses were patent with a restenosis rate of 10.7% without further neurological symptoms. CONCLUSION: Interventional angioplasty with stent-placement of the supraaortic arteries is a safe and effective alternative in patients are at high risk for classical surgical procedures.
The risk involved in partial liver resections depends mainly on tumor localization, invasion of central vascular structures, and parenchymal function. The imaging techniques available today (computed tomography, magnetic resonance imaging) allow us to detect precisely the extent of tumor invasion and their relationship to central vessels. The various three-dimensional reconstruction techniques are helpful with regard to a virtual planning of liver resections. The calculation of remaining liver volumes subsequent to partial hepatectomies are considered to be an essential predictive parameter in terms for the development of postoperative liver failure. In a retrospective and a later consecutive, prospective clinical study we analyzed the postoperative risk in a series of 570 patients. In an univariate analysis 13 of 31 parameters showed significant values. In multivariate analysis only three parameters (partial hepatic resection rate, PHRR), gamma-glutamyltranspeptidase, and prothrombin activity) were independent parameters for predicting liver failure, generating the most significant values for the PHRR. In our experience the most comfortable and precise technique for evaluating PHRR is the b-spline technique.
AIM: The purpose of this study was to evaluate a large-area, flat-panel X-ray detector (FD), based on caesium-iodide (CsI) and amorphous silicon (a-Si) with respect to skeletal radiography. Conventional images were compared with digital radiographs using identical and reduced radiation doses. MATERIALS AND METHODS: Thirty consecutive patients were studied prospectively using conventional screen-film radiography (SFR; detector dose 2.5 microGy). Digital images were taken from the same patients with detector doses of 2.5, 1.25 and 0.625 microGy, respectively. The active-matrix detector had a panel size of 43 x 43 cm, a matrix of 3 x 3K, and a pixel size of 143 microm. All hard copies were presented in a random order to eight independent observers, who rated image quality according to subjective quality criteria. Results were assessed for significance using the Student's t -test (confidence level 95%). RESULTS: A statistically significant preference for digital over conventional images was revealed for all quality criteria, except for over-exposure (detector dose 2.5 microGy). Digital images with a 50% dose showed a small, statistically not significant, inferiority compared with SFR. The FD-technique was significantly inferior to SFR at 75% dose reduction regarding bone cortex and trabecula, contrast and overall impression. No statistically significant differences were found with regard to over- and under-exposure and soft tissue presentation. CONCLUSION: Amorphous silicon-based digital radiography yields good image quality. The potential for dose reduction depends on the clinical query.
PURPOSE: Evaluation of the diagnostic efficacy and cost-benefit of contrast enhanced CT (CT) and MRI pre- and post-SPIO-particles in focal hepatic disease with consideration of therapeutic outcome. METHODS: In 52 patients with the suspicion of primary or secondary hepatic malignancy, biphasic spiral CT and breath-hold gradient-echo T1- and fast spin-echo T2-weighted MRI pre- and post-iron oxide administration (1.5 T, body-phased-array coil) were compared. The number of hepatic lesions and the related diagnoses resulting from each imaging modality were recorded and statistically correlated to the final diagnoses established by biopsy/OP (34/52), long term follow-up of 12 months (18/52), and a consensus reading of all imaging modalities considering all clinical imaging information. The most likely induced therapy resulting from each imaging test was correlated to the final therapy. Based on data from the hospitals accountants, the therapy-related costs were estimated without hospitalization costs. RESULTS: In 34/52 (65.4%) of the cases the correct diagnosis was primarily stated by CT (sensitivity [se.] 85.2%, specificity [sp.] 44.0%). In additional 10/52 of the cases unenhanced MRI (se. 91.4%, sp. 75.0%) enabled correct diagnoses, and in another 6 cases the diagnosis was established only by SPIO-MRI (se. 100%, sp. 86.7%). Considering the possible therapeutic recommendation arising from each modality, CT would have induced needles therapy costs of 191,042 DM, unenhanced MRI of 171,035 DM, and SPIO-MRI of 7,311 DM. In comparison to the real therapy costs of 221,873 DM, this would have corresponded to an unnecessary increase of therapy costs of 86.1%, 77.1%, and 3.3%, respectively. In two cases (1 hemangioma, 1 regenerative nodule) all modalities failed, causing unnecessary surgery in one patient. DISCUSSION: In this problem-oriented scenario unenhanced and SPIO-enhanced MRI proved to be superior to CT regarding diagnostic efficacy. The cost-benefit resulted mainly due to preserving patients from unnecessary surgical procedures.
The purpose of this study was to evaluate a large-area, flat-panel X-ray detector, which uses cesium-iodide (CsI) and amorphous silicon (a-Si). Conventional images were compared with digital images acquired with equal dose (2.5 microGy) and with 50% dose reduction. Fifteen consecutive patients were studied prospectively using an asymmetric screen-film system (detector dose, 2.5 microGy). Digital images were taken from the same patients in a posteroanterior view with detector doses of 2.5 and 1.25 microGy, respectively. The CsI/a-Si active-matrix imager had a panel-size of 43 x 43 cm, a matrix of 3 x 3k, and a pixel-pitch of 143 microm. Hard copies were presented in a random order to eight independent observers, who rated image quality according to six subjective quality criteria. Statistical significance of differences was evaluated with Student's t test for paired samples (confidence level, 95%). Digital radiographs with 2.5 and 1.25 microGy were superior to conventional images regarding all quality criteria. Statistically significant differences were observed for five of six criteria at a detector dose of 2.5 microGy and for only one quality feature at 1.25 microGy. Flat-panel digital imagers based on CsI/a-Si technique have the potential to replace conventional systems and might allow a reduction of radiation dose by 50% without loss of image quality.
PURPOSE: To compare contrast agent-enhanced spiral and electron-beam computed tomography (CT) for the analysis of segmental and subsegmental pulmonary arteries. MATERIALS AND METHODS: CT angiography of the pulmonary arteries was performed in 56 patients to rule out pulmonary embolism. Electron-beam CT was performed in 28 patients. The other 28 patients underwent spiral CT with comparable scanning protocols. The depiction of segmental and subsegmental arteries was analyzed by three independent readers. The contrast enhancement in the main pulmonary artery was measured in each patient. RESULTS: Analysis was performed in 1,120 segmental and 2, 240 subsegmental arteries. One segmental (RA7, P =.010) and two subsegmental (LA7b, P =.029; RA6a+b, P =.038) arteries in paracardiac and basal segments of the lung were depicted significantly better with electron-beam CT. There was no statistically significant difference between electron-beam and spiral CT in the total number of analyzable peripheral arteries depicted. The mean contrast enhancement in the main pulmonary artery was 362 HU in electron-beam CT studies versus 248 HU in spiral CT studies. CONCLUSION: Detailed visualization of peripheral pulmonary arteries is well within the scope of advanced CT techniques. Electron-beam CT has minor advantages in analyzing paracardiac arteries, probably because of reduction of motion artifacts and higher contrast enhancement. Further studies are needed to establish whether electron-beam CT allows a more confident diagnosis of emboli in these vessels.
PURPOSE: To determine the value of magnetic resonance (MR) sialography for the diagnosis of sialolithiasis by comparing results prospectively with those of ultrasonography (US) and digital sialography. MATERIALS AND METHODS: MR sialography was prospectively performed with T2-weighted three-dimensional (3D) constructive interference in steady-state (CISS) and rapid acquisition with relaxation-enhancement (RARE) sequences in 24 patients suspected of having sialolithiasis. Evoked salivation was used as contrast material. T1-weighted spin-echo and T2-weighted turbo spin-echo MR imaging also were performed. The results were then compared with those of US and digital sialography, with the latter as standard of reference. RESULTS: The 3D CISS images were significantly (P: <.05) superior to RARE images for demonstrating the submandibular ductal system, followed by T2-weighted turbo spin-echo images (P: <.01) and T1-weighted spin-echo images (P: <.001). The sensitivity and specificity were 100% and 80%, respectively, for CISS MR sialography and 80% and 100%, respectively, for RARE MR imaging. The sensitivity and specificity of US were both 80%. CONCLUSION: MR sialography with evoked salivation is noninvasive and allows delineation of the submandibular ductal system and detection of sialoliths with accuracy that is similar to that of digital sialography and superior to that of US.