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Biomedical subjects

B Gebauer

Publications and source records attributed to B Gebauer.

At least 19 recordsLinked to original sources
PubMed2006

Intraoperative ductoscopy in women undergoing surgery for breast cancer.

BACKGROUND: Extensive intraductal disease represents an important clinical problem in the management of patients with invasive or in situ breast cancer. The purpose of this study was to determine the value of intraoperative ductoscopy for detection of intraductal neoplasia in women with breast cancer. METHODS: Intraoperative ductoscopy was performed in 54 women undergoing operation for breast cancer. A rigid gradient index microendoscope (0.7 mm) was used for all examinations. Ductoscopy findings were documented prospectively and correlated with preoperative mammography and histology of the resection specimen. RESULTS: Fifty of 54 (92%) patients were examined successfully. Ductoscopy identified intraductal lesions (ie, red patches, ductal obstruction, or microcalcifications) in 25 of 50 (50%) patients. Abnormal ductoscopic appearance was found in 19 of 23 patients with extensive intraductal disease (82%). Mammographic microcalcifications were observed in 15 of those 19 patients and in 3 patients with normal ductoscopy (78%). The combined sensitivity of both methods was 95%. Patients with an abnormal ductal appearance on ductoscopy, compared with those with a normal ductal appearance, had a greater incidence of extensive intraductal spread of cancer (76% vs 16%) and a greater incidence of positive surgical margins (44% vs 12%). CONCLUSIONS: High-resolution ductoscopy is able to detect extensive intraductal disease in a considerable number of women with breast cancer. In selected patients, a combination of both preoperative imaging and intraoperative ductoscopy may help to avoid incomplete resections and re-excisions.

Adult↗
PubMed2006

Magnetic resonance-guided biopsy of suspicious breast lesions with a handheld vacuum biopsy device.

PURPOSE: To evaluate a handheld vacuum-assisted device system for magnetic resonance image (MRI)-guided breast lesion biopsy. MATERIAL AND METHODS: In 32 patients, a total of 42 suspicious breast lesions (mean diameter 7.5 mm for mass lesions, 11.6 mm for non-masslike diffuse lesions) seen with MRI (no suspicious changes in breast ultrasound or mammography) were biopsied (27 lateral, 15 medial) using a 10G vacuum-assisted breast biopsy device under MR guidance. Histology of biopsy specimens was compared with final histology after surgery or follow-up in benign lesions. RESULTS: In all biopsies, technical success was achieved. Histology revealed 11 lesions with ductal carcinoma in situ (DCIS) or invasive cancer, three with intermediate lesions (LCIS) and 28 with benign breast lesions (adenosis, infected hematoma). In one patient with discordant results of MRI and histology, surgical excision revealed medullary cancer. In the follow-up (mean 18 months) of the histological benign lesions, no breast cancer development was observed. Besides minor complications (hematoma, n = 6), with no further therapeutic interventions, no complications occurred. CONCLUSION: MRI-guided breast lesion biopsy using a handheld vacuum-assisted device is a safe and effective method for the work-up of suspicious lesions seen with breast MRI without changes in mammography or ultrasound. In the case of discordant histology of vacuum biopsy and breast MRI appearance, surgical excision is recommended.

Adult↗
PubMed2006

Image guided respiratory gated hypofractionated Stereotactic Body Radiation Therapy (H-SBRT) for liver and lung tumors: Initial experience.

To evaluate our initial experience with image guided respiratory gated H-SBRT for liver and lung tumors. The system combines a stereoscopic x-ray imaging system (ExacTrac X-Ray 6D) with a dedicated conformal stereotactic radiosurgery and radiotherapy linear accelerator (Novalis) and ExacTrac Adaptive Gating for dynamic adaptive treatment. Moving targets are located and tracked by x-ray imaging of implanted fiducial markers defined in the treatment planning computed tomography (CT). The marker position is compared with the position in verification stereoscopic x-ray images, using fully automated marker detection software. The required shift for a correct, gated set-up is calculated and automatically applied. We present our acceptance testing and initial experience in patients with liver and lung tumors. For treatment planning CT and Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET) as well as magnetic resonance imaging (MRI) taken at free breathing and expiration breath hold with internal and external fiducials present were used. Patients were treated with 8-11 consecutive fractions to a dose of 74.8-79.2 Gy. Phantom tests demonstrated targeting accuracy with a moving target to within +/-1 mm. Inter- and intrafractional patient set-up displacements, as corrected by the gated set-up and not detectable by a conventional set-up, were up to 30 mm. Verification imaging to determine target location during treatment showed an average marker position deviation from the expected position of up to 4 mm on real patients. This initial evaluation shows the accuracy of the system and feasibility of image guided real-time respiratory gated H-SBRT for liver and lung tumors.

Aged↗
PubMed2005

[Potential advantages of the MRI for the radiofrequency ablation of liver tumors].

PURPOSE: To present first results of radiofrequency ablation of liver tumors using a new MR compatible applicator. MATERIALS AND METHODS: We performed 37 interventions in 20 patients (mean age 58.6 years) with primary intrahepatic malignancies or metastases: colorectal carcinoma n = 6, hepatocellular carcinoma n = 3, pancreatic carcinoma n = 4, sarcoma n = 2, cholangiocellular carcinoma n = 1, carcinoma of the tonsil n = 1, breast carcinoma n = 1, gastric carcinoma n = 1, and gastrointestinal stroma tumor n = 1. Interventions were performed under CT-guidance with CT fluoroscopy (n = 32) and under MR-guidance (n = 5) using fast T1-weighted sequences in breath-hold technique. RFA was performed with the RF-generator (150 W) under local anesthesia and sedation using MR compatible applicators (Starburst XL, Rita Medical Systems, USA) together with the appropriate Soft Tissue Introducer System. Intra-interventional control was performed with intrahepatically or intralesionally placed introducer system or applicator. MRI was performed with plain breath-triggered T2-weighted turbo spin echo sequences (TSE T2) with fat saturation. RESULTS: All interventions were performed without major events. The mean diameter of induced coagulation was 4.0 (+/- 0.7) cm. Repositioning was necessary in 8 interventions (21 %) after detection of residual tumor on an intra-interventional MRI. After a mean follow-up of 6.5 (+/- 1.2) months, the local tumor control rate was 92 %. CONCLUSION: MR-compatible RF applicators offer the opportunity for intra-interventional detection of residual tumor during RF ablations by use of sensitive MRI sequences. These procedures may lead to a higher confidence in tumour ablation and may reduce the number of re-interventions and local recurrences of intrahepatic tumors.

Catheter Ablation↗
PubMed2005

[Contrast media pressure injection using a portal catheter system--results of an in vitro study].

PURPOSE: Are implanted central venous port catheters suitable for contrast media pressure (power) injection in computed tomography? MATERIAL AND METHODS: In an in vitro study 100 ml of contrast medium (Ultravist 370, Schering, Berlin, Deutschland) was injected through 20 different port catheter systems using a power injector (Stellant, Medrad, Inianola, USA) with a pressure limit of 325 PSI. The injection rate was increased from 2 ml/s to 10 ml/s in increments of 2 ml/s. The maximum injection pressure and maximum injection rate were assessed. RESULTS: An injection rate of 2 ml/s was possible in all catheter systems. Injection rates of 4 ml/s in 18 systems, 6 ml/s in 13 systems and 8 ml/s in 6 systems were achieved. With a given pressure limit of 325 PSI an injection rate of 10 ml/s was not possible in any of the port catheter systems. There were no catheter ruptures, catheter disconnections or contrast extravasations noted. CONCLUSION: Power injection of contrast media with a pressure limit of 325 PSI seems to be tolerated by port catheter systems. Most of the evaluated port systems allow flow rates suitable for multislice computed tomography requiring rapid contrast injection.

Catheterization, Central Venous↗
PubMed2004

[Imaging modalities in the preoperative staging of rectal carcinoma].

Thorough clinical examination, endorectal ultrasound, and magnetic resonance tomography (MRI) are decisive tools in the pretherapeutic work-up of patients with rectal cancer. Depth of infiltration to the rectal wall as well as involvement of perirectal lymph nodes by the tumor are the key questions to be answered. To receive adequate information from imaging procedures, the right questions need to be asked. The extent of invasion of the rectal wall and exact location of tumor infiltration to neighboring structures can be demonstrated by MRI very well, particularly if imaging planes are acquired at 90 degrees to the position of the rectum. Recent developments in computed tomography (CT) using isotrope voxels allow three-dimensional reconstructions of tumors without loss of imaging quality. Assessment of the primary tumor and its nodal metastases after preoperative radio-(chemo-)therapy is still seriously limited. Fusion of positron emission tomography and CT could be a step towards solving the problem of response assessment in the near future.

Contrast Media↗
PubMed2004

[Soft tissue sarcoma].

Soft tissue sarcomas are characterized by their heterogeneity. With new diagnostic imaging techniques, low- and high-grade components of the tumor can be differentiated. Thus biopsies should be guided by imaging to assure representative specimens. Besides histopathology, the advent of chromosomal and gene expression analysis may allow more accurate classification in the near future. Gene expression profiling has already proven its value by finding new subclassifications in other tumor types. Furthermore, this technique is a promissing tool to predict the response of a tumor to neoadjuvant and adjuvant therapy. Up to now, response evaluation in neoadjuvant therapy is based on tumor size and not on vital tumor cells. Newer techniques (i.e., Magnetic-resonance-Spectroscopy, Molecular Imaging) can show the change of metabolism in neoadjuvant therapy and allow objective, comparative measurement of biological activity. The diagnostic of soft tissue sarcomas implies primarily a multidisciplinary approach for a stage associated therapy.

Biopsy↗
PubMed2004

[Ultrasound- and fluoroscopy-guided implantation of peripherally inserted central venous catheters (PICCs)].

PURPOSE: Evaluation of ultrasound- and fluoroscopy-guided implantation of peripherally inserted central venous catheters (PICCs). MATERIALS AND METHODS: In 32 patients (12 males, 20 females; mean age 64.1 +/- 11.9 years) with clinical indication for long term central venous catheter (chemotherapy: N = 5; parenteral nutrition and fluid substitution: N = 26; parenteral pain therapy: N = 1) a PICC was placed by an interventional radiologist using ultrasound guidance. RESULTS: The placement of the PICC was technically successful in 31 (96.9%) patients, with placement of 20 single-lumen 5F PICCs, 4 double-lumen 6F PICCs and 7 double-lumen 7F PICCs. The mean duration of catheter usage was 28.4 (2 - 161) days with a total of 910 catheter days. No catheter occlusions were recorded. Two patients developed a superficial venous thrombosis of the upper extremity. The resulting thrombotic rate was 2.2 per 1000 catheter days. No catheter associated infection was recorded. CONCLUSION: The ultrasound guided placement of peripherally inserted central venous catheters (PICCs) via a superficial vein of the upper extremity is a practical alternative to central catheters via central veins.

Adult↗
PubMed2004

[Long-term central venous lines and their complications].

The implantation of permanent (> 14 days) central venous catheters is constantly increasing, accelerated by a trend toward outpatient therapies. Subcutaneous tunneled and non-tunneled catheters as well as port systems are available. The interventional radiologist plays an important role in the implantation of central venous catheters as well as in detection and treatment of any complications. Various access ways via peripheral and central veins are described and the implantation techniques for the different systems explained. The use of peel-away sheaths allows the radiologist to implant subcutaneous tunneled catheters via the Seldinger technique without surgical preparation. Procedure-related early and late complications may occur, and the radiologist plays an important role in the surveillance and management of catheter-associated complications. This review demonstrates the different catheter systems and implantation techniques.

Catheterization, Central Venous↗
PubMed2004

New concepts of staging in gastrointestinal tumors as a basis of diagnosis and multimodal therapy.

The therapy of gastrointestinal tumors is becoming more and more sophisticated and complex. This is due to an improved understanding of the pathogenesis of tumors, a more detailed classification and increasing therapeutic options. The basis of optimized therapeutic concepts is the exact evaluation of tumor spread and exact staging. The following review describes some of the most recent staging concepts in gastrointestinal tumors. Multislice computed tomography (CT), positron emission tomography (PET) and new supraparamagnetic iron oxide contrast agents for magnetic resonance imaging enable an increasing quality of the visualization of tumors and metastases. 3D imaging will be used for planning of surgical interventions in the future. Optical coherence tomography may contribute to an improved tumor staging and, thus, to the safety of limited interventions in early oesophageal- and gastric cancer patients. Laparoscopy and laparoscopic ultrasound become increasingly important for the identification of small metastases in the peritoneum, in lymph nodes and in the liver. The sentinel lymph node concept will contribute to an improved staging and individualized therapy as well.

Combined Modality Therapy↗
PubMed2003

[Use of SPIO-enhanced T1- and T2-weighted images for the differentiation of liver lesions: an ROC analysis].

PURPOSE: The superparamagnetic iron oxide (SPIO) Resovist is a contrast media with shortening of both T(1) and T(2) relaxation time. This study evaluates the impact of SPIO-enhanced T(1)- and T(2)-weighted images for the differentiation of liver lesions. MATERIALS AND METHODS: SPIO-enhanced MRI examinations (1.5 T, Symphony Quantum) of 61 patients were analyzed. Thirty-seven patients had malignant liver lesions (metastases n = 32, HCC n = 5) proven by biopsy or laparotomy, 11 patients had benign liver lesions (FNH n = 2, hemangiomas n = 4, benign cysts n = 5, normal liver on laparoscopy n = 13). After unenhanced T(1)- and T (2)-weighted imaging, a bolus injection of 1.4 ml SPIO (Resovist) was given, followed by T(1)-weighted imaging at 20 s, 60 s, and 5 min and T(2)-weighted imaging at 10 min post injection. A score from 1 (benign) to 5 (malignant) was used by three blinded radiologist for the ROC analysis of the unenhanced T(1)-/T(2)-weighted images (set 1) and of the combinations of unenhanced T(1)/T(2)-weighted and SPIO T(1)-weighted images (set 2), unenhanced T(1)/T(2) and SPIO T(2)-w images (set 3) and all images (set 4). RESULTS: The accuracy of plain MRI (set 1: 56 %) was increased by SPIO-enhanced T(1)-weighted images (set 2: 81 %) and SPIO-enhanced T(2)-weighted images (set 3: 90 %). Best results were obtained using unenhanced T(1)-weighted, unenhanced T(2)-weighted and both SPIO T(1)-weighted and T(2)-weighted images (set 4: 93%). The accuracy of predicting histopathologic diagnosis was 91%. CONCLUSION: For the differentiation of liver lesions, SPIO-enhanced T(2)-weighted images had a greater impact on the accuracy of MRI than T (1)-weighted images, but SPIO-enhanced T(1)-weighted images provided additional information in some patients and should not be deleted.

Adult↗
PubMed2003

[Transjugular implantation of venous port catheter systems].

PURPOSE: Prospective analysis of success and complication rates of chest port implantation via the internal jugular vein. MATERIALS AND METHODS: In 50 consecutive patients (25 men, 25 women; mean age 61 +/- 14 years) the internal jugular vein was punctured under ultrasound guidance. Through this access, a port system was inserted and the catheter tip was placed at the cavoatrial junction. The port reservoir was implanted into a subcutaneous infraclavicular pocket and fixed to the fascia of the pectoralis muscle. Indications for port implantation were chemotherapy (n = 46), total parenteral nutrition (n = 2) or intravenous medication (n = 2). RESULTS: A chest port catheter system was successfully implanted in all 50 patients. The mean duration of placement was 90 +/- 65 catheter days. No complications occurred during implantation. In the post-interventional period a single catheter dysfunction occurred (0.22 per 1,000 catheter days). Two local infections occurred in the early post-interventional period (0.43 per 1,000 catheter days). One port system had to be explanted prematurely due to pain. CONCLUSION: The ultrasound guided puncture of the internal jugular vein enables a safe access for insertion of a central venous port catheter system and is associated with a very low complication rate. Port placement via this access vein should therefore be the primary treatment.

Adult↗
PubMed2003

[Flexible applicator systems for radiofrequency ablation (RFA) of hepatic tumors].

PURPOSE: To report our experience with flexible applicators in radiofrequency ablation (RFA) of hepatic tumors. MATERIALS AND METHODS: In 6 liver tumors in 6 patients, a flexible RFA-applicator system (RITA StarBurst FLEX, RITA Medical Systems, Mountain View, CA, USA) was placed under CT guidance. The Seldinger technique with an 11G access system (RITA StarBurst Access) was used to place the application system into the liver. Before and within a week after the ablation, all tumors were investigated with contrast-enhanced MRI. RESULTS: The Seldinger technique accommodated the placement of a thin 17.5-gauge needle for the initial puncture, enabling easy adjustment of the position of the needle. The flexible applicator of the RFA system could be placed in 4.5 (+/- 1.8) minutes on average. CONCLUSION: Flexible applicators facilitate CT-guided RFA and can be placed using the Seldinger technique.

Carcinoma, Hepatocellular↗
PubMed2002

Intraperitoneal distribution of ultrasound contrast medium imaged with B-mode ultrasound and colour-stimulated acoustic emission imaging.

Intraperitoneal port catheter systems for local delivery of cytotoxic drugs require imaging prior to chemotherapy to confirm homogenous distribution of an injected fluid in the entire peritoneal cavity. This study was performed to assess whether contrast-enhanced ultrasound (US) is a suitable imaging modality for this task. Twelve patients with peritoneal carcinosis and an implanted intraperitoneal port catheter system were studied before chemotherapy. Ultrasound examinations were performed after bolus injections of the microbubble contrast medium Levovist. Distribution of the contrast medium in the peritoneal cavity was imaged using B-mode US and colour-stimulated acoustic emission imaging (SAE). Contrast-enhanced CT imaging was used as term of reference for evaluating the US results. Distribution of the microbubbles in the peritoneal cavity was easily detected by both US methods. In 10 of 12 patients a free distribution in all abdominal quadrants was seen with both US techniques. In 2 of 12 patients, CT and US showed contrast medium limited to the perihepatic area. Therapy was stopped and surgical repositioning of the catheter was performed. Ultrasound after intraperitoneal injection of a microbubble contrast agent provides reliable information about the distribution of intraperitoneally injected fluid in the peritoneal cavity. This method is therefore well suited for imaging port catheter systems prior to chemotherapy.

Acoustics↗
PubMed2001

Survey of conventional and spiral ct doses.

PURPOSE: To investigate the radiation dose for conventional computed tomography (CT) and spiral CT during different CT examinations at various hospitals and practices. MATERIALS AND METHODS: CT dose index with an active length of 15 cm was measured in 16 different types of CT scanners by using ionization chamber dosimetry. Twenty-six holders (one who has legal responsibility under national law for a radiologic installation) operating a total of seven conventional and 20 spiral CT scanners were asked for their standard parameters for various CT examinations. Weighted CT dose index and dose-length product were determined for each examination. RESULTS: For most examinations, the tube current time product was significantly higher for conventional CT than for spiral CT (.002 </= P </=.05). The ratio of section distance to section thickness for conventional CT was significantly lower than the pitch for spiral CT (.001 </= P </=.05). The weighted CT dose index and dose-length product for spiral CT were about half of those for conventional CT. The third quartiles for weighted CT dose index and dose-length product for spiral CT were much lower than those recommended as reference doses. CONCLUSION: CT examinations with conventional CT scanners are often performed with unnecessarily high radiation dose. For the establishment of reference doses, the radiation dose with spiral CT scanners should be taken into account.

Humans↗