Biomedical subjects

Ulrich Linsenmaier

Publications and source records attributed to Ulrich Linsenmaier.

9 recordsLinked to original sources

PubMed2006

Antitumoral activity of rapamycin in renal angiomyolipoma associated with tuberous sclerosis complex.

A 19-year old patient with tuberous sclerosis presented with a renal angiomyolipoma. Because animal trials of tuberous sclerosis showed an effect of rapamycin on renal tumors, our patient was administered rapamycin for 6 months. During this time, the renal angiomyolipoma shrank significantly, regrew during an 8-month period, and decreased in size again after readministration of rapamycin.

Adult↗

PubMed2004

Treatment of benign and malignant tracheobronchial obstruction with metal wire stents: experience with a balloon-expandable and a self-expandable stent type.

Over the last few years various types of metal wire stents have been increasingly employed in the treatment of both malignant and benign tracheobronchial obstruction. To date, however, few studies have investigated the in vivo properties of different stent types. We implanted 26 balloon-expandable tantalum Strecker stents (18 patients) and 18 self-expandable Wallstents (16 patients) into the tracheobronchial system of 30 patients with combined stenting in 4 patients. Mean age was 51 years (range: 0.5-79 years). Malignant disease was present in 23 patients, benign disease in seven patients. Both patients and individual stents were monitored clinically and radiographically. The probability of stents remaining within the tracheobronchial system, and of their remaining undislocated and uncompressed was calculated using Kaplan-Meier analysis for both stent types. Average stent follow-up time was 112 days until explantation and 115 days until patients' death or discharge. Kaplan-Meier analysis revealed a higher probability for the Wallstent to remain within the tracheobronchial system. Dislocation and compression occurred more rarely. Explantation, however, if desired, was more difficult compared to the Strecker stent. The Wallstent also led to the formation of granulation tissue, especially at the proximal stent end, frequently requiring reintervention. Both stent types proved to be effective therapeutic options in the management of obstructive tracheobronchial disease. The mechanical properties of the Strecker stent seem to be less favorable compared to the Wallstent but removal is easy. For benign disease, however, the Wallstent reveals limitations due to significant side effects.

Adolescent↗

PubMed2004

3D imaging with an isocentric mobile C-arm comparison of image quality with spiral CT.

The purpose of this study was to evaluate the image quality of the new 3D imaging system (ISO-C-3D) for osteosyntheses of tibial condylar fractures in comparison with spiral CT (CT). Sixteen human cadaveric knees were examined with a C-arm 3D imaging system and spiral computed tomography. Various screws and plates of steel and titanium were used for osteosynthesis in these specimens. Image quality and clinical value of multiplanar (MP) reformatting of both methods were analyzed. In addition, five patients with tibial condylar fractures were examined for diagnosis and intra-operative control. The image quality of the C-arm 3D imaging system in the cadaveric study was rated as significantly worse than that of spiral CT with and without prostheses. After implantation of prostheses an increased incidence of artifacts was observed, but the diagnostic accuracy was not affected. Titanium implants caused the smallest number of artifacts. The image quality of ISO-C is inferior to CT, and metal artifacts were more prominent, but the clinical value was equal. ISO-C-3D can be useful in planning operative reconstructions and can verify the reconstruction of articular surfaces and the position of implants with diagnostic image quality.

Artifacts↗

PubMed2004

C-arm-based mobile computed tomography: a comparison with established imaging on the basis of simulated treatments of talus neck fractures in a cadaveric study.

OBJECTIVE: To analyse the image quality and diagnostic effectiveness of a new C-arm-based 3D imaging method (C-arm-CT) for intraoperative evaluation of screw osteosyntheses adjacent to a peripheral joint. MATERIALS AND METHODS: Insertion of screws into four cadaveric specimens simulated the surgical treatment of talus neck fractures. Ten orthopedic surgeons and 10 radiologists evaluated X-ray, C-arm fluoroscopy, C-arm-CT and CT images. RESULTS: The best image quality was obtained with X-rays (p < 0.001), followed by C-arm fluoroscopy (2D) and CT, with the C-arm-CT (3D) being rated lowest (p < 0.001). The most correct diagnoses were obtained with CT and C-arm-CT (with no statistical difference between them), while C-arm-fluoroscopy was inferior (p < 0.001) and X-rays were the worst (p < 0.05). CONCLUSIONS: Even if the image quality of C-arm-CT is definitely inferior to that of CT, screw misplacements can be reliably detected using C-arm-CT. As compared to the current standard procedures (intraoperative fluoroscopy and postoperative radiography), C-arm-CT performed better. C-arm-CT is ideally suited to the intraoperative diagnosis of high-contrast inquiries like bone fragments and OS material, especially at the extremities. Coupling of the new 3D imaging to existing navigation systems is possible. C-arm-CT will support the further development and implementation of open and minimally invasive surgical procedures.

Bone Screws↗

PubMed2003

Classification of calcaneal fractures by spiral computed tomography: implications for surgical treatment.

The purpose of this study was to evaluate spiral computed tomography and multislice CT (SCT/MSCT) with multiplanar reconstructions (MPR) in the classification of calcaneal fractures according to a modified CT classification and to quantify fragment displacement to guide surgical treatment. Forty-eight calcaneal fractures were examined by spiral CT (1- to 2-mm slice thickness, pitch=1.5) with multiplanar reconstructions (MPR). Fractures were grouped according to a modified Munich classification scheme, differentiating six categories of fractures by joint involvement, number of fragments in the posterior facet, and the presence and extent of displacement. A qualitative and quantitative statement was made for the presence of clinical relevant displacement of the posterior articular facet (A: >2 mm), widening of the heel (B: crossing fibular reference line), reduction in calcaneal height (C: >10%), and axis shift of the calcaneocuboid angle (D: >10 degrees ). Treatment recommendations resulting from the CT classification were retrospectively compared with the treatment given by examining the patients' files. There were 10 extra-articular and 38 intra-articular fractures; 8 were in class I (extra-articular, nondisplaced), 2 in class II (extra-articular, displaced), 1 in class III (intra-articular, nondisplaced), 20 in class IV (two fragments), 9 in class V (three fragments), and 8 in class VI (>4 fragments), one of the latter being uncertain; 34 showed displacement of the articular facet, 35 widening of the heel, 35 reduction in calcaneal height, and 20 a shift of the axis. In 94% of the cases the procedure recommended by the Munich system of classification was followed; there was disagreement in 1 case in class I and 1 in class IV. Spiral CT allowed fracture classification and quantification of relevant displacement of fragments by radiologists. The implemented recommendations for treatment were adopted by surgeons in most cases.

Adolescent↗

PubMed2002

Gadolinium as an alternative contrast agent for diagnostic and interventional angiographic procedures in patients with impaired renal function.

BACKGROUND: The study was designed to investigate the safety and feasibility of gadopentetate dimeglumine, a gadolinium-based contrast medium, as an alternative angiographic contrast agent in patients with impaired renal function and high risk for iodinated contrast-induced nephropathy. METHODS: Gadopentetate dimeglumine was used as the radiographic contrast agent in 32 diagnostic or interventional angiographic procedures in 29 patients (59% diabetics) with severe renal insufficiency (average serum creatinine of 3.6+/-1.4 mg/dl). The average dose of gadopentetate dimeglumine was 0.34+/-0.06 mmol/kg body weight. Gadopentetate dimeglumine was used either alone (n=20) or in conjunction with carbon dioxide (n=12). RESULTS: Thirty-two angiographic procedures (24 diagnostic angiographies and 8 interventional procedures) were performed in 29 patients. For diagnostic purposes, eleven selective renal arteriographies, six angiographies of the iliac arteries and lower extremities, and seven venous angiographies of the upper extremity and central veins were performed. Interventional procedures consisted of two percutaneous transluminal renal angioplasties with stenting, four percutaneous peripheral vascular interventions, and two balloon angioplasties of a dialysis fistula. None of the patients, except one, had evidence of post-procedure contrast material-induced renal failure (increase in serum creatinine >0.5 mg/dl within 72 h) or other complications. This patient had a clinically important increase in serum creatinine level after percutaneous transluminal renal angioplasty and stenting, probably due to cholesterol embolism. Gadopentetate dimeglumine had sufficient radiographic density to allow adequate diagnostic visualization with digital subtraction equipment in all cases. CONCLUSIONS: Gadopentetate dimeglumine is an alternative and safe radiographic contrast agent for angiography and interventional procedures in patients with severe pre-existing renal impairment. In this population with high risk for contrast-induced acute renal failure, it is obviously less nephrotoxic than iodinated contrast media.

Adult↗

PubMed2002

Immediate S-100B and neuron-specific enolase plasma measurements for rapid evaluation of primary brain damage in alcohol-intoxicated, minor head-injured patients.

The neuroproteins S-100B and neuron-specific enolase (NSE) released into the circulation are suggested to be reliable markers for primary brain damage. However, safe identification of relevant post-traumatic complications after minor head injury (MHI) is often hampered by acute intoxication of the patients. The objective of this study was to determine the diagnostic validity of immediate plasma measurements of S-100B and NSE in comparison with neurological examinations and cerebral computed tomography (CCT) findings in alcohol-intoxicated MHI patients. One hundered thrity-nine MHI individuals were enrolled in this prospective study during Munich's Oktoberfest 2000. Plasma levels of S-100B and NSE as well as serum alcohol and glucose values were determined by fully automated assays immediately after admission. The results were compared with Glasgow Coma Scale score, a brief neurological examination, and the CCT findings. Without being influenced by alcohol, median S-100B levels of the CCT+ group were significantly increased compared with those of the CCT- group (P < 0.001). NSE, alcohol, and glucose levels showed no significant group differences. As calculated by the ROC analysis, a cutoff value of 0.21 ng/mL with an area under the curve of 0.864 clearly differentiates between CCT+ and CCT- patients at a sensitivity of 100%, a specificity of 50.0%, and a positive likelihood ratio of 2.0. Although acute alcohol intoxication did not confound plasma measurements of S-100B and NSE, only S-100B levels below the cutoff level of 0.21 ng/mL seem to indicate absence of primary brain damage. Thus, in addition to routine neurological examinations, S-100B measurements immediately after admission might help to reduce CCT scans in alcohol-intoxicated patients early after MHI.

Adult↗

PubMed2002

Three-dimensional CT with a modified C-arm image intensifier: feasibility.

A portable C arm was modified for cone-beam computed tomography (CT). This three-dimensional (3D) CT imaging system facilitated the acquisition of fluoroscopic images during a 190 degrees rotation and computed a 3D data cube (matrix, 256 x 256 x 256; scanning time, 100 seconds) with multiplanar image reformation. The high-contrast resolution, 0.9 line pairs per millimeter, was comparable; the low-contrast resolution, minimal; and the radiation dose, 60%-80% lower, as compared with these parameters at spiral CT. The normal anatomy of small joints could be depicted, and the osteosynthesis screws in the talus were correctly identified.

Bone Screws↗

PubMed2001

Whole-body computed tomography in polytrauma: techniques and management.

An interdisciplinary team should be involved in the diagnosis and management of severely injured patients. The adoption of criteria for starting treatment for multiple trauma avoids underestimation of seriousness of injury. These criteria are established by the circumstances of the accident, the patterns of trauma, and the vital findings. Basic diagnosis comprises a limited number of plain films in the trauma room, including supine chest, lateral cervical spine, and pelvis, and ultrasound of abdomen, pleura, and pericardium. Organ diagnosis using CT is complementary and depends on the clinical findings and findings from the basic investigations. We recommend spiral CT (skull base 2/2/4 mm, cerebrum 8/8/8 mm native) and after intravenous contrast medium thoracic (5/7.5/5 mm) and abdominal CT (8/12/8 mm). Image reconstruction of bony structures can be added. The CT and the trauma center should be in close proximity; time-consuming transfers must be avoided. If this is not possible, a CT can be integrated in the trauma room. Our hospital trauma registry contains over 2200 entries. A quality committee has been established and external quality control is implemented.

Humans↗