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Biomedical subjects

G W Kauffmann

Publications and source records attributed to G W Kauffmann.

At least 37 records · Page 2Linked to original sources
PubMed2002

Preoperative evaluation of living renal donors: value of contrast-enhanced 3D magnetic resonance angiography and comparison of three rendering algorithms.

The aim of this study was to assess the value of contrast-enhanced three-dimensional MR angiography (CE 3D MRA) in the preoperative assessment of potential living renal donors, and to compare the accuracy for the depiction of the vascular anatomy using three different rendering algorithms. Twenty-three potential living renal donors were examined with CE 3D MRA (TE/TR=1.3 ms/3.7 ms, field of view 260-320x350 mm, 384-448x512 matrix, slab thickness 9.4 cm, 72 partitions, section thickness 1.3 mm, scan time 24 s, 0.1 mmol/kg body weight gadobenate dimeglumine). Magnetic resonance angiography data sets were processed with maximum intensity projection (MIP), volume rendering (VR), and shaded-surface display (SSD) algorithms. The image analysis was performed independently by three MR-experienced radiologists recording the number of renal arteries, the presence of early branching or vascular pathology. The combination of digital subtraction angiography (DSA) and intraoperative findings served as the gold standard for the image analysis. In total, 52 renal arteries were correspondingly observed in 23 patients at DSA and surgery. Other findings were 3 cases of early branching of the renal arteries, 4 cases of arterial stenosis and 1 case of bilateral fibromuscular dysplasia. With MRA source data all 52 renal arteries were correctly identified by all readers, compared with 51 (98.1%), 51-52 (98.1-100%) and 49-50 renal arteries (94.2-96.2%) with the MIP, VR and SSD projections, respectively. Similarly, the sensitivity, specificity and accuracy was highest with the MRA source data followed by MIP, VR and SSD. Time requirements were lowest for the MIP reconstructions and highest for the VR reconstructions. Contrast-enhanced 3D MRA is a reliable, non-invasive tool for the preoperative evaluation of potential living renal donors. Maximum intensity projection is favourable for the processing of 3D MRA data, as it has minimal time and computational requirements, while having similar or superior accuracy for the depiction of vessel anomalies or pathology compared with VR and SSD, respectively.

Algorithms↗
PubMed2002

Radiation dose reduction in chest radiography using a flat-panel amorphous silicon detector.

AIM: The aim of this study was to evaluate the image quality and the potential for radiation dose reduction with a digital flat-panel amorphous silicon detector radiography system. MATERIAL AND METHODS: Using flat-panel technology, radiographs of an anthropomorphic thorax phantom were taken with a range of technical parameters (125kV, 200mA and 5, 4, 3.2, 2, 1, 0.5, and 0.25mAs) which were equivalent to a radiation dose of 332, 263, 209, 127, 58.7, 29, and 14 microGy, respectively. These images were compared to radiographs obtained by a conventional film-screen radiography system at 125kV, 200mA and 5mAs (equivalent to 252 microGy) which served as reference. Three observers evaluated independently the visibility of simulated rounded lesions and anatomical structures, comparing printed films from the flat-panel amorphous silicon detector and conventional x-ray system films. RESULTS: With flat-panel technology, the visibility of rounded lesions and normal anatomical structures at 5, 4, and 3.2mAs was superior compared to the conventional film-screen radiography system. (P< or =0.0001). At 2mAs, improvement was only marginal (P=0.19). At 1.0, 0.5 and 0.25mAs, the visibility of simulated rounded lesions was worse (P< or =0.004). Comparing fine lung parenchymal structures, the flat-panel amorphous silicon detector showed improvement for all exposure levels down to 2mAs and equality at 1mAs. CONCLUSION: Compared to a conventional x-ray film system, the flat-panel amorphous silicon detector demonstrated improved image quality and the possibility for a reduction of the radiation dose by 50% without loss in image quality.

Humans↗
PubMed2002

[Organ-sparing surgery of renal cell carcinoma - operative technique and findings in radiological follow-up].

Nephron-sparing surgery of renal cell carcinoma in the 1970's and 1980's in patients with bilateral renal tumors or reduced renal function (imperative indication) has shown a very low risk of recurrent cancer. Today, nephron-sparing surgery in renal cell carcinoma is considered in an increasing number of patients with expected sufficient renal function after nephrectomy (elective indication). Resection technique, the use of Tabotamp(R) to reduce bleeding, and pseudotumors do complicate the interpretation of the images. It has been not yet defined which diagnostic modality is best suited for follow-up after renal cell carcinoma resection. Follow-up protocols in different institutions show a wide variety. The follow-up of patients after nephron-sparing surgery is performed by annual sonography or MRI every three months. Up to now, CT and ultrasound are the standard methods. MRI with its multiplanar imaging and improved soft tissue contrast seems to have an equal diagnostic value. Additionally, MRI seems to be suited for patients with reduced renal function. The aim of this paper is to give guidelines for the radiologist to understand the different surgical procedures and to evaluate the postoperative findings. Different imaging modalities in the follow-up of patients and special radiological phenomena are discussed.

Adult↗
PubMed2002

[Prospective comparison of hydrosonography, endosonography and specimen sonography for TN staging of gastric carcinoma].

PURPOSE: To compare hydrosonography (HUS), endosonography (EUS) and experimental sonography (PUS) with respect to TN-staging accuracy of gastric carcinoma. MATERIAL AND METHODS: Thirty-six patients with gastric carcinoma underwent EUS (7.5/12 MHz transducer, Olympus GF-UM 20) and HUS (3.75 MHz transducer, Toshiba, Sonolayer SSA-270A) for TN-staging according to the UICC-classification. The resected specimens were reexamined (3.75/7.5 MHz transducer) and again TN-staging was performed. Findings were correlated with histopathological results. RESULTS: T- and N-staging accuracies were as follows: EUS 54 % (19/35) and 79 % (27/34); HUS 41 % (15/37) and 61 % (22/36); and PUS 51 % (19/37) and 72 %(26/36). Sensitivities and specificities for the detection of lymph node metastases were as follows: EUS 87 % and 54 %; HUS 57 % and 69 %; and PUS 83 % and 54 %. CONCLUSIONS: The accuracy of sonographic TN- staging is limited in patients with gastric carcinoma. Nevertheless, EUS may contribute to the preoperative management of patients with gastric carcinoma if indications are well defined. HUS is not suited for TN-staging of gastric carcinoma.

Adult↗
PubMed2001

[The vascular patient--diagnosis and minimally invasive therapy. Which technique for what illness?].

The non-invasive imaging modalities, color coded duplex sonography (CCDS), magnetic resonance tomography (MRT), and computed tomography (CT), have pushed conventional angiography out of most diagnostic fields. The experienced user will achieve fast, reliable answers with CCDS in dedicated clinical settings. MRT as well as CT are concurring imaging modalities for the most appropriate diagnostic answer. Not only pure image quality, but also patient management, and availability play a major role. Catheter based angiography will in the future still play a role in mesenteric ischemia (non occlusive disease) and for imaging of very small vessel pathology, e.g. on panarteritis nodosa. At the moment, peripheral leg run-offs are still best performed with conventional angiography, nevertheless, MR as well as CT seem to have the ability to perform diagnostic procedures. Ongoing studies will allow a solid judgement in the near future. The true value of catheter angiography is in the direct assessment, planning, and performance of interventional procedures, e.g. catheter based obliteration or revascularization. Implantation of stent devices and a whole range of different mechanical and pharmacological revascularization procedures have improved the interventional management of vascular stenoses and occlusions. The interventional radiologist is treating physician in the classical sense in this setting. Acute bleeding episodes, e.g. in the brain, thorax, abdomen, or pelvis, are best imaged with computed tomography. Conventional angiography still plays a major diagnostic and therapeutic role in bleeding into preformed cavities, such as the bile ducts or the intestine. In this setting, all available information including CT scans should be valued. For complex therapeutic regimens in oncology or in pure palliative situations, angiographic diagnosis followed by embolization and/or ablation therapy is established.

Angioplasty, Balloon↗
PubMed2001

[Characteristic perfusion pattern of osseous giant cell tumor in dynamic contrast-enhanced MRI].

PURPOSE: To describe the perfusion pattern of giant cell tumor (GCT) of bone with Gd-enhanced dynamic MR imaging. To compare time-intensity-curves in patients with local recurrence and postoperative alterations without recurrence. METHODS: Nine patients (5 women, 4 men) with GCT of bone underwent 19 dynamic MRI examinations. Mean age was 34 years (range 24-64 years). All diagnoses were proven by pathology. Dynamic contrast-enhanced MRI was performed at 1.0 T using T1-weighted gradient echo sequences. GCT was located in the distal radius (4x), tibia (3x), fibula (1x) and humeral head (1x). RESULTS: All giant cell tumors showed a uniform perfusion pattern with a steep slope and maximum intensity value followed by an early and rapid washout phase. The same pattern appeared in five local recurrences of GCT in four patients. In nine follow-up examinations without local recurrence dynamic MRI yielded in uncharacteristic perfusion patterns. CONCLUSION: These results demonstrate a uniform perfusion pattern of GCT of bone obtained by dynamic MRI. It is characterized by a steep slope followed by an early and rapid washout phase. This characteristic pattern can also be obtained in local recurrences. Dynamic contrast-enhanced MRI appears a helpful method for primary diagnosis of GCT of bone and detection of local recurrences after surgery.

Adult↗
PubMed2001

[Post-traumatic dissection of the abdominal aorta].

Dissections due to deceleration trauma are rarely limited to the infradiaphragmal aorta (only 2-3%) and are usually lethal. Here we report the unusual course of an abdominal aortic dissection with aneurysmatic enlargement of the false lumen. Based on diagnostic imaging, a therapeutic stent application was planned in order to close the entry and to prevent rupture. During the intervention sondation of the false lumen revealed that the left renal artery had a reentry. Due to the complexity of the entry-reentry situation of the left renal artery the intervention was not possible, and the patient had to undergo vascular surgery.

Abdominal Injuries↗
PubMed2001

[Prospective study to compare high-resolution computed tomography and magnetic resonance imaging in the detection of pancreatic neoplasms: use of intravenous and oral MR contrast media].

PURPOSE: To compare thin-section hydro-CT and MRI in the detection of pancreatic neoplasms. Evaluation of an oral, superparamagnetic contrast agent (OMP) for pancreatic MRI. MATERIAL AND METHODS: 45 patients with suspected pancreatic neoplasms were examined with consecutive thin-section helical CT (Hydro-CT, 3/6/3, 130 ml Ultravist, Schering) and MRI (1.0 T, breath-holding, T1w-GRE, T1w-GRE fat-sat, T2w-TSE). The MRI protocol included precontrast studies, studies after oral administration of OMP (Abdoscan, Nycomed Amersham) and studies after administration of OMP and Gadodiamide i.v. (Omniscan, Nycomed Amersham). All images were assessed by two independent radiologists in a blinded fashion. Radiologic diagnosis was correlated with histology or clinical follow-up (> or = 3 month). RESULTS: 39 patients could be included in analysis. In 13 cases a pancreatic neoplasm was proven by histology. Thin-section hydro-CT and MRI showed no statistically significant differences for the detection of pancreatic neoplasia. The sensitivity of helical hydro-CT was superior compared to MRI (88.5% vs. 65.44/73.1%/76.9%). The specificity of MRI was superior compared to helical hydro-CT (86.5% vs. 94.2%/90.4%/88.5%). CONCLUSION: Thin-section hydro-CT and MRI show similar results for the detection of pancreatic neoplasms. Compared to thin-section helical CT, MRI still has the drawbacks of much more time consumption and, still, lower spatial resolution. The use of an oral, superparamagnetic contrast agent added no advantage for pancreatic MRI.

Administration, Oral↗
PubMed2000

[Preoperative staging of renal cell carcinoma with caval thrombus: is staging in MRI justified? Prospective histopathological correlated study].

To evaluate whether MRI is usefull in staging renal cell carcinomas with caval thrombus the accuracy of computed tomography (CT) and magnetic resonance imaging (MRI) in staging renal tumors with caval thrombus were preoperatively examined. Tumor staging by CT and MR imaging were correlated with histopathological tumor stadium. In MRI 4 out of 7 thrombi were correctly diagnosed with high accuracy, in CT none. In advanced renal carcinoma MRI with Gadolinium was superior to CT imaging, especially in diagnosing tumor thrombus. Consequently the extent of tumor thrombus may be assessed by MRI which therefore may replace conventional cavography.

Aged↗
PubMed1999

Evaluation of angiogenesis and perfusion of bone marrow lesions: role of semiquantitative and quantitative dynamic MRI.

Magnetic resonance imaging (MRI) is a noninvasive technique that complements computed tomography (CT), conventional X-ray, and bone marrow biopsies by sampling a large volume of musculoskeletal bone and providing information that aids the diagnosis, staging, and follow-up of various lesions. Although less sensitive to the mineral components of bones, the MRI appearance of physiologic bone marrow is mainly a reflection of the relative amounts of red marrow, yellow marrow, and trabecular bone. Therefore, use of T1-and T2-weighted MR sequences with or without fat suppression currently remains the most common approach to musculoskeletal bone lesion imaging. An additional imaging strategy to characterize various bone lesions is the application of contrast-enhanced dynamic MRI. This article examines semiquantitative and quantitative dynamic imaging, evaluation, and postprocessing techniques in various benign and malignant musculoskeletal lesions. Practical guidelines for performing a dynamic contrast-enhanced MR examination are proposed.

Bone Marrow Neoplasms↗
PubMed1999

[Angiography and interventional radiology of the kidney].

For imaging of renal pathology a broad spectrum of radiologic diagnostic procedures are available which are, sometimes and particularly more recently, competing among each other in their diagnostic yield and relevance. For tumorous lesions ultrasound, computed tomography and magnetic resonance imaging are performed predominantly. Angiography is no longer required with the exception of highly selected cases and in some specific preoperative workup requirements. Until recently, catheter based digital subtraction angiography has been considered as gold standard. However, non-invasive techniques such as CT-angiography and MR-angiography are evolving parallel to their quantum leap of resolutions and readiness to use. Nevertheless, well accepted criteria for quality assessement of these new modalities are still lacking. More comparison studies are urgently warranted. Despite the availability of ultrashort pulse sequences applying the T1 relaxation reduction effect of gadolinium enhanced MR techniques overestimation of renal artery stenosis still poses a substantial problem. Renal intervention implies a variety of procedures such as plain angioplasty, stent placement, embolization of traumatic and both benign and malignant tumors. These methods have emerged over the last two decades from a more experimental nature to a fully accepted treatment option. When renal artery angioplasty is embedded in an aggressive approach including stenting as an adjunct for more complex cases, renal ostial lesions and a well organized follow-up regimen its therapeutic potential for treatment of renal insufficiency, malignant hypertension, for organ preservation bears a very high potential. Provided adequat periinterventional drug regimen restenosis rates may be as low as 10%. In highly selected cases capillary embolization might be used as an alternative to nephrectomy with a similar clinical outcome. Particularly the development of superselective small caliber embolization catheters parallel to further refinement of embolization material has aided to use superselective occlusion techniques in benign vascular lesions and renal trauma.

Adult↗
PubMed1999

[Radiodiagnosis following kidney transplantation].

Diagnostic imaging after renal transplantation is of high importance in the differential diagnosis of peri- and postoperative complications. Sonography with color duplex imaging is the method of choice in the diagnosis of acute transplant rejection. MRI is an additional method in the diagnosis of transplant dysfunction especially in diagnosis of perirenal fluid collections. MR angiography and MR urography are noninvasive diagnostic modalities with the potential to replace angiography and pyelography. Angiography, complemented by carbon dioxide angiography, still is the gold standard in the diagnosis of transplant artery stenosis.

Angiography↗
PubMed1999

[Renal tumor embolization].

Today the relevance of renal tumor embolization is not determined only by the technical and clinical success of the method. Progress in diagnosis of early stages of renal carcinomas as well as the improvement of both surgical techniques and anesthetic procedures have lead to a change in the selection of patients for embolization. Preoperative embolization of advanced renal cell carcinomas with tumor thrombus into the vena cava or of T4 tumors is now an established clinical procedure. The complete occlusion of the vascular bed of the tumors leads to a considerable reduction in intraoperative blood loss and to simplification of the surgical preparation. By using Ethibloc for embolization, palliation of a hemorrhage or of tumor-related pain in inoperable patients is usually successful. Although local control of the tumor disease, including complete tumor ablation, is achieved by embolization, the median survival rate of our palliatively embolized patients is only 3.5 months. This short life expectancy in the group of inoperable patients has to be acknowledged individually in patients considered for palliative embolization who are free of symptoms related the tumor.

Aged↗
PubMed1999

[Distal choledochal cyst in hydro-spiral CT].

Bile duct cysts are rare abnormalities of the biliary tract. Surgical therapy has been recommended because of possible complications such as cholestasis with jaundice and the risk of bile duct carcinoma. Accurate preoperative radiological imaging is available for surgical planning. In addition to direct imaging of the biliary system in ERCP, high-resolution axial computerized imaging techniques are necessary. The use of MRCP is becoming more frequent in diagnostic imaging of the biliary tract. Similar to the diagnosis of pancreatic tumors with hydro-spiral CT technique, we demonstrate the benefits of hydro-CT in imaging of a distal choledochal cyst, the problems of differential diagnosis and the classification in the generally accepted Todani system in a case in which accurate clarification with MRCP and ERCP was not possible.

Adult↗
PubMed1999

[Follow-up of TIPSS by color-coded duplex sonography using an ultrasonic signal enhancer. First results].

A study was performed to determine the visualization of the transjugular intrahepatic portosystemic stent shunt (TIPSS) and the detection of stenosis by the use of a capillary transversing signal enhancer. In 37 patients 37 colour-coded duplex sonographies were performed before and after intravenous injection of the ultrasound signal enhancer Levovist (Schering, Berlin). The examinations were evaluated using a four-category score. Special attention was paid to the detection of stenoses in the TIPSS. Transjugular portal venograms of the same day were used as gold standard. The use of Levovist provided better colour and flow signals for the portal vein end of the shunt in only 9 of 37 sonograms and for the hepatic vein end of the shunt in 37 of 39 sonograms. Eleven of 13 stenoses requiring reintervention in portal venography could be correctly identified with signal enhancer. Eleven of these 13 stenoses were located in the hepatic vein end of the shunt. Ultrasound signal enhancer can significantly improve the sonomorphological visualization especially of the hepatic vein end of TIPSS in colour-coded duplex sonography. Stenoses which usually occur in the hepatic vein end of the shunt may be better detected.

Constriction, Pathologic↗