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Biomedical subjects

J Tacke

Publications and source records attributed to J Tacke.

At least 19 recordsLinked to original sources
PubMed2007

B-flow and B-flow with 3D and SRI postprocessing before intervention and monitoring after stenting of the internal carotid artery.

OBJECTIVE: To investigate the extent to which B-flow and B-flow with 3D postprocessing and speckle reduction imaging (SRI) have advantages in appraising the morphology of a high-grade stenosis of the internal carotid artery (ICA) for preinterventional planning and for postinterventional ultrasonographic follow-up. MATERIALS/METHODS: A comparative appraisal of flow with CCDS, power Doppler, B-flow and 3D B-Flow with SRI were carried out prospectively in 50 patients with >70% stenosis according to NASCET criteria in contrast medium-enhanced MRA before and after the intervention. After stenting of the internal carotid artery (ICA), i.a. digital substraction angiography (DSA) served as an additional reference method. RESULTS: In >70% ICA stenosis, simultaneous imaging of the pre-stenotic, intra-stenotic and post-stenotic flow was attained with B-flow in 45/90 cases (90%), with power Doppler in 39/50 cases (78%) and with CCDS in only 31/50 cases (62%). After intervention, a complete detection of flow without overwriting or blooming artifacts was achieved in all 50 patients only by B-flow. The intrastenotic flow (p<0.05) could be better demarcated against the lumen and the vessel wall before the intervention, whereas the flow within the stent could be very much better appraised after the intervention (p<0.01) using 3D postprocessing of B-flow with additional SRI. Re-stenoses with hypoechoic vascular wall changes (3/50 patients) were detected at an early stage using B-flow. CONCLUSIONS: B-flow technique with SRI and 3D postprocessing can facilitate the intrastenotic detection of flow in >70% ICA stenosis with fewer flow artifacts. After stenting, the perfused vascular lumen shows less flow artifacts compared with CCDS and power Doppler. In order to elucidate hemodynamic changes, additional Doppler examinations are still necessary.

Aged↗
PubMed2006

[Digital ultrasonic diagnosis of lower leg venous thrombosis using harmonic imaging and cross beam technology].

PURPOSE: To evaluate the extent to which Tissue Harmonic Imaging (THI) and spatial averaging (Sono-CT, Cross Beam) facilitate the diagnosis of lower leg venous thrombosis. MATERIALS AND METHODS: In 100 cases of lower leg venous thrombosis, the conventional B-scan, THI, and ultrasonic CT technology (Cross Beam) in examinations using a multi-frequency transducer head (9 - 14 MHz, Logiq 9, GE) were compared during follow-up studies using compression sonography over at least 6 weeks. Two independent examiners performed digital image documentation (PACS connection) without modifying the gray level parameters optimized in the B-scan. A thrombosis was considered to be proven sonographically if at least one ultrasonic modality yielded findings reproducible in follow-up checks at a comparable site in accordance with both examiners. RESULTS: Thromboses in the V. tibialis posterior category (97 %) and the fibular category (81 %) were found most often, followed by muscular venous thromboses (48 %). Thromboses in the V. tibialis anterior category were rare (12 %). The procedure comparison showed an advantage for ultrasonic CT technology in terms of the demarcation of thromboses of the deeper veins (sensitivity 98 %), as compared to THI (sensitivity 87 %, specificity 91 %, PPV: 99 %) and the B-scan (sensitivity 81 %). CONCLUSION: If a high-resolution linear transducer is used, THI and ultrasonic CT-Technology can facilitate the diagnosis of a lower leg venous thrombosis.

Adult↗
PubMed2005

[Percutaneous thermal ablation of renal neoplasms].

Due to modern examination techniques such as multidetector computed tomography and high-field magnetic resonance imaging, the detection rate of renal neoplasms is continually increasing. Even though tumors exceeding 4 cm in diameter rarely metastasize, all renal lesions that are possible neoplasms should be treated. Traditional treatment techniques include radical nephrectomy or nephron-sparing resection, which are increasingly performed laparoscopically. Modern thermal ablation techniques such as hyperthermal techniques like radiofrequency ablation RFA, laser induced thermal ablation LITT, focused ultrasound FUS and microwave therapy MW, as well as hypothermal techniques (cryotherapy) may be a useful treatment option for patients who are unfit for or refuse surgical resection. Cryotherapy is the oldest and best known thermal ablation technique and can be performed laparoscopically or percutaneously. Since subzero temperatures have no antistyptic effect, additional maneuvers must be performed to control bleeding. Percutaneous cryotherapy of renal tumors is a new and interesting method, but experience with it is still limited. Radiofrequency ablation is the most frequently used method. Modern probe design allows volumes between 2 and 5 cm in diameter to be ablated. Due to hyperthermal tract ablation, the procedure is deemed to be safe and has a low complication rate. Although there are no randomized comparative studies to open resection, the preliminary results for renal RFA are promising and show RFA to be superior to other thermal ablation techniques. Clinical success rates are over 90 % for both, cryo- and radiofrequency ablation. Whereas laser induced thermal therapy is established in hepatic ablation, experience is minimal with respect to renal application. For lesions of more than 2 cm in diameter, additional cooling catheters are required. MR thermometry offers temperature control during ablation. Microwave ablation is characterized by small ablation volumes and plays a role as a coagulation tool during resection. Focused ultrasound is the only non-invasive method, but it is still experimental.

Catheter Ablation↗
PubMed2004

[Percutaneous radiofrequency ablation of renal cell cancer].

Renal cell cancer is the most frequent malignant tumor of the kidney. Depending on tumor size, extension and general condition, radical or partial nephrectomy, which meanwhile can be performed laparoscopically, is still the therapy of choice. Patients with an increased surgical risk, or suffering from additional renal tumors or tumor in a single kidney, percutaneous tumor ablation is a helpful therapeutical option. Among all thermal ablation procedures, most experiences exist with radiofrequency ablation (RFA). A significant advantage of this technique is the possibility of direct puncture of the tumor without Seldinger technique and track ablation. This helps to reduce the risk of bleeding and tumor seeding within the puncture track. By use of modern ablation probes, lesions of up to 5 cm in diameter can be created without repositioning of the probe. Initial superselective particle embolization is recommended in tumors beyond 3 cm in size, because renal cell cancer is often hypervascularized and devasularization helps to reduce ablation time. Furthermore, the tumor location within the kidney is influencing the ablation result. Exophytically growing lesions or tumors within the renal parenchyma can be treated with a safety margin. Tumors in a central location or with broad contact to the collecting system are no candidates for thermal ablation, because of an increased risk of thermal collateral damage. Computed tomography is an optimal imaging modality and crucial to planning, performing and controlling of a successful percutaneous RFA. Based on the previous experiences of 300 published cases, renal RFA results in an over 90% success rate associated with a low complication rate. A randomized controlled study comparing RFA and surgery is necessary to answer the question whether RFA can be considered therapy of first choice even for patients, who are according to the actual evidence surgical candidates.

Carcinoma, Renal Cell↗
PubMed2004

Multipolar radiofrequency ablation: first clinical results.

Common systems of radiofrequency ablation (RFA) are monopolar devices which require grounding pads on the thighs in order to close the electrical circuit. Bipolar RFA does not require grounding pads, because both electrodes are located on one probe and alternating current circuit is confined within the target tissue. In this paper we report on the first clinical application of a new ablation device which enables both, bipolar (1 probe) and multipolar (up to 3 internally cooled probes simultaneously) radiofrequency ablation. We report on bi- and multipolar applications in liver tumors (9 patients), osteoid osteoma (2 patients) and renal cell cancer (1 patient).

Adult↗
PubMed2004

[Local lysis with alteplase for the treatment of acute embolic leg ischemia following the use of the duett closure device: preliminary results].

PURPOSE: To analyze retrospectively the result of the alteplase lysis therapy of embolic complications following the use of the Duett closure device. METHODS AND MATERIALS: For 3.5 years, the Duett closure device was used in 1,398 angiographies to close the femoral puncture site. The Duett device consists of a balloon and a liquid procoagulant containing collagen and thrombin, which is injected into the puncture tract under endovascular balloon protection of the arterial puncture site. In 9 patients (0.64 %), the procoagulant was incidentally injected into the femoral artery causing acute leg ischemia. Eight patients received local lysis therapy with alteplase via a contralateral femoral access. One patient underwent surgery. On average, 21 mg alteplase (4 - 35 mg) were administered within 14 h (4 - 21 h). The course of the lysis was followed angiographically and clinically. All patients were interviewed by telephone 23 months (4 - 35 months) later. RESULTS: In 3 patients, lysis was complete. In 5 patients, only little thrombotic material remained. In all patients, symptoms of ischemia resolved completely within the first hours after initiation of lysis. In 5 cases, bleeding occurred at the puncture site closed with the Duett device during lysis, including development of a false aneurysm in 2 cases. Complications led to premature termination (n = 2) or interruption of the lysis (n = 3). All complications were treated conservatively. Clinically, long-term sequelae were paresthesia and hypoesthesia in the lower leg and foot in 2 patients treated with lysis, and in the patient who underwent surgery. CONCLUSION: Very rarely occurring embolic complications after use of the Duett closure device can be effectively treated with alteplase lysis. A high rate of complications is to be expected at the puncture site closed with the Duett device.

Acute Disease↗
PubMed2003

[Percutaneous radiofrequency ablation -- clinical indications and results].

Percutaneous interstitial tumor ablation therapy is a relatively new and steadily growing field within interventional radiology. Radiofrequency ablation (RFA) became one of the most accepted techniques among hyperthermal ablation procedures, presumably due to its superior relation between probe diameter and efficacy. The first part of this review provided an overview of the underlying principles, technical background and application techniques. This second part describes the indications, techniques and results of clinical RFA applied to primary and secondary liver tumors as well as experiences with extrahepatic RFA applied to kidney, bone and lung, together with a discussion of the current literature.

Carcinoma, Hepatocellular↗
PubMed2002

[Percutaneous radiofrequency ablation of liver malignancies: first experience with a 200-W radiofrequency generator].

PURPOSE: To evaluate the effectiveness of a percutaneous radiofrequency ablation device, consisting of a LeVeen probe and a newly developed 200-W radiofrequency generator. MATERIAL AND METHOD: In 20 patients (9 male, 11 female), 30 primary and secondary liver malignancies were treated by CT-guided percutaneous radiofrequency ablation. The patients were separated in a potentially curable (n = 10) and a palliative (n,= 10) treatment group. The treatment was performed using an umbrella-shaped LeVeen probe with a diameter of 3.5 cm or 4 cm and a 200-W generator (Radiotherapeutics, Mountain View, CA, USA). All interventions were performed under general anesthesia by a standardized treatment protocol. The size of the lesions treated ranged from 2.2 x 2 x 2 cm to 10.8 x 10.1 x 10.5 cm. RESULTS: In all patients, the correct placement of the probe and radiofrequency ablation was technically successful. In two patients more than one treatment session was necessary to achieve the intended treatment result. In all patients of the potentially curable group a complete tumor necrosis could be achieved, whereas in the palliative treatment group complete tumor necrosis was only achievable in one patient. The achieved necrosis size ranged from 2.4 x 2.8 x 2.5 cm to 9.2 x 8 x 10.5 cm. In one patient a colon fistula was observed 4 weeks after treatment. No further complications were observed. The follow-up period ranges from 1 to 15 months (mean 4.5 months). CONCLUSION: By use of a powerful generator in combination with a LeVeen probe percutaneous treatment of even large liver tumors is possible. Radiofrequency ablation is a safe procedure for the minimal-invasive therapy of non resectable liver neoplasms.

Adult↗
PubMed2002

[Selective CT mesentericography in the diagnostics of obscure overt intestinal bleeding: preliminary results].

AIM: To evaluate intra-arterial CT mesentericography (CTM) in the diagnostics of severe obscure overt intestinal bleeding in comparison with conventional mesentericography (MG) and surgery. METHODS: In 8 patients (23 - 82 years, mean 59 years), CTM was performed via the catheter left in the superior mesenteric artery after MG to detect the source of bleeding. Early and late-phase spiral CT scans were acquired after administration of contrast medium. Active bleeding was considered to be present if extravasation of contrast medium into the bowel was found. The results of MG and CTM were compared with the results of surgery. RESULTS: With MG active bleeding was found in one patient, with CTM in five patients. In three patients, both MG and CTM were negative. Six patients underwent surgery. Five cases of bleeding detected with CTM were confirmed by surgery. In one case, bleeding found with CTM was not confirmed by surgery. One patient underwent surgery although all imaging procedures were negative. The source of bleeding remained unknown. Surgically, the site of bleeding was located in the jejunum in 3 patients (jejunitis, jejunal ulcers, carcinoid), one patient had a diverticulum in the ascending colon. The colonic bleeding site was correctly localized with CTM, whereas the small bowel bleeding could only roughly be assigned to the proximal or distal jejunum or jejunoileal transition area. CONCLUSION: Preliminary results indicate that selective CTM is superior to MG in the evaluation of severe obscure overt intestinal bleeding.

Adult↗
PubMed2001

Cross-sectional imaging of primary osseous hemangiopericytoma.

The aim of this study was to assess cross-sectional imaging features and the value of CT and MRI in primary hemangiopericytoma of bone. In five patients with histologically proven primary osseous hemangiopericytoma CT and MR scans were evaluated retrospectively. Both CT and MRI were available in four patients each. In three patients both imaging techniques were available. On CT primary hemangiopericytoma of bone presents as an expansive lytic lesion with bone destruction and inhomogeneous contrast enhancement. Magnetic resonance imaging depicts osseous hemangiopericytoma as hyperintense lesion on T2-weighted images with intermediate signal intensity on T1-weighted images. Curvilinear tubular structures of signal void in the tumor matrix on T1-weighted images and corresponding hyperintense structures on T2-weighted and on fat-suppressed short tau inversion recovery images were present in three patients. Although cross-sectional imaging findings are non-specific, they add to the diagnosis and provide valuable information about the extent of bone destruction and local tumor spread in patients with primary osseous hemangiopericytoma. While CT demonstrates the extent of bone destruction best, MRI better visualizes medullary and soft tissue extension of the tumor. Curvilinear signal abnormalities support the diagnosis of hemangiopericytoma of bone. This imaging pattern is best visualized on fat-suppressed or contrast enhanced T1-weighted MR images.

Adult↗
PubMed2001

MR-guided percutaneous cryotherapy of the liver: in vivo evaluation with histologic correlation in an animal model.

The purpose of this study was to evaluate the feasibility of MR-guided percutaneous cryotherapy of the porcine liver and to correlate the resulting tissue necrosis with MR imaging and histology. Using an MR-compatible, argon-based cryotherapy system (CryoHit; Galil Medical Ltd., Israel) with 2- and 3-mm diameter tapered cryotherapy probes, MR-guided percutaneous cryotherapy was performed in seven pigs (mean body weight, 40 kg) under general anesthesia in a short-bore magnet (1.5 T ACS NT; Philips, The Netherlands) using an ultrafast T2-weighted single-shot LoLo TSE sequence and a T1-weighted gradient-echo sequence. The frozen liver tissue was depicted accurately on fast T2- and T1-weighted sequences, providing precise delineation of the ablated tissue volume. On follow-up postcontrast MR controls, the cryolesions appeared avascular. They decreased in size compared with the initially frozen volume down to 70% at a 2-week follow-up. Histologically, a coagulation necrosis with a close correlation to the MR follow-up examinations was objectified. No cryotherapy-related complications occurred. J. Magn. Reson. Imaging 2001;13:50-56.

Animals↗
PubMed2001

[MRI-controlled percutaneous cryotherapy of liver metastases].

The prognosis for patients with liver metastases depends on the therapeutic options regarding the treatment of the primary tumor, co-existing extrahepatic metastases and the extent and treatment possibilities of the hepatic metastases themselves. Numerous curative or palliative oncological therapeutic concepts have been introduced in case of non-resectable liver metastases to prolong survival while maintaining a highest possible quality of life. Cryotherapy, which can be performed percutaneously and under magnetic resonance guidance, is one of these manifold therapeutic modalities, combining the inherent advantages of MRI with minimal invasiveness. Excellent visualization of the frozen liver tissue, precise tumor ablation, as well as an almost painless intervention due to the analgetic effect of the ice are implicating percutaneous cryotherapy as an attractive alternative to other ablation techniques. First clinical results are promising. However, meticulous and extensive long-term evaluation on a broad clinical scale is required.

Animals↗
PubMed2001

Diuretic-enhanced gadolinium excretory MR urography: comparison of conventional gradient-echo sequences and echo-planar imaging.

The aim of this study was to investigate the utility of different gadolinium-enhanced T1-weighted gradient-echo techniques in excretory MR urography. In 74 urologic patients, excretory MR urography was performed using various T1-weighted gradient-echo (GRE) sequences after injection of gadolinium-DTPA and low-dose furosemide. The examinations included conventional GRE sequences and echo-planar imaging (GRE EPI), both obtained with 3D data sets and 2D projection images. Breath-hold acquisition was used primarily. In 20 of 74 examinations, we compared breath-hold imaging with respiratory gating. Breath-hold imaging was significantly superior to respiratory gating for the visualization of pelvicaliceal systems, but not for the ureters. Complete MR urograms were obtained within 14-20 s using 3D GRE EPI sequences and in 20-30 s with conventional 3D GRE sequences. Ghost artefacts caused by ureteral peristalsis often occurred with conventional 3D GRE imaging and were almost completely suppressed in EPI sequences (p < 0.0001). Susceptibility effects were more pronounced on GRE EPI MR urograms and calculi measured 0.8-21.7% greater in diameter compared with conventional GRE sequences. Increased spatial resolution degraded the image quality only in GRE-EPI urograms. In projection MR urography, the entire pelvicaliceal system was imaged by acquisition of a fast single-slice sequence and the conventional 2D GRE technique provided superior morphological accuracy than 2D GRE EPI projection images (p < 0.0003). Fast 3D GRE EPI sequences improve the clinical practicability of excretory MR urography especially in old or critically ill patients unable to suspend breathing for more than 20 s. Conventional GRE sequences are superior to EPI in high-resolution detail MR urograms and in projection imaging.

Adult↗
PubMed2001

US-guided nephrostomy with the aid of a magnetic field-based navigation device in the porcine pelvicaliceal system.

PURPOSE: To assess the technique and feasibility of ultrasound (US)-guided nephrostomy performed with the aid of a magnetic field-based navigation device. MATERIALS AND METHODS: Twelve percutaneous nephrostomy procedures were performed in seven domestic pigs under real-time US guidance employing a navigation system. Two magnetic field sensors registered the actual position of the puncture needle and the US transducer. The actual needle position and the aimed puncture tract were graphically projected into the real-time US images, allowing exact navigation of the needle. After placement of the needle into the renal pelvis, the nephrostomy tube was inserted by means of the Seldinger technique. RESULTS: The puncture procedure was successfully performed in each case. The renal pelvis was punctured in a single attempt in 10 of 12 cases. In two cases, multiple attempts were necessary because bending of the puncture needle led to inaccuracies of the navigation system. With exception of two small perirenal urinomas, no complications were seen. CONCLUSIONS: The magnetic field-based navigation device allows easy and accurate performance of nephrostomy guided solely by US.

Animals↗
PubMed2001

[Magnetic resonance tomography imaging of the inner ear of patients with sensorineural hearing loss or vertigo].

BACKGROUND: Progress in surgical techniques in the temporal bone has lead to the demand of exact delineation of this complex anatomical region for preoperative planning. The aim of this study was to assess the potential of a three-dimensional T2 weighted turbo-spin-echo-sequence to depict anatomical details and pathological changes of the inner ear. METHODS: Twenty-five patients presenting with sensori-neural hearing loss and/or vertigo were included in this study. A T2 weighted turbo-spin-echo-sequence was carried out on a 1.5 T imager, employing a surface coil with a diameter of 8 cm. The scan parameters were set as follows: TR 2000, TE 500, scan matrix 128 x 128, field of view 90 mm, slice thickness 0.66 mm, NSA 4. In addition, 3D maximum-intensity-projections (MIP) were created, using these data as source images. RESULTS: Image quality was excellent in all 25 cases. The 2.5 cochlear windings, modiolus, vestibule with saccule and utricle all three semicircular canals, crus commune and the facial nerve and vestibulocochlear nerve in the inner auditory canal were clearly delineated in all patients. The cochlear aqueduct was seen in 32% (8 cases), while the vestibular aqueduct was delineated in 16% (4 cases) in this series. In MIP, the entire labyrinth was shown in a single view. In 22 patients regular morphology was found, while in three cases pathological changes were detected (an enlarged vestibular aqueduct and saccus in one patient, partial fibrous obliteration of the labyrinth in two patients). CONCLUSIONS: The introduced TSE sequence can be used to delineate the anatomy of the inner ear as well as pathological changes. The technique appears to be useful for preoperative planning.

Adolescent↗
PubMed2001

Implantation of a new access device for hemodialysis (Dialock): initial experience in 5 patients.

PURPOSE: A new hemodialysis access port system was implanted. METHODS: The Dialock consists of a port-like double-valve, implanted subcutaneously below the clavicle, which is attached to two catheters, placed in the right atrium via the jugular vein. The device has been implanted in 5 patients (4 female, 1 male). RESULTS: In all 5 patients the implantation of the catheters and the port was technically successful. Total average duration of dialysis was 3.6 months. Two patients developed a port pocket hematoma 10-14 days post implantation, one of them required surgical revision. One port was explanted due to septicemia, whereas a port infection was not confirmed. One patient showed a thrombotic occlusion of both catheter tips 8 days after implantation, fixed by catheter exchange. Another patient presented with slight migration of the port catheters, which was managed by refixation of the port within the pocket. Beside these complications, the devices were working well. CONCLUSION: The Dialock system offers an interesting alternative to external catheters for hemodialysis. With respect to the complications it deserves further studies to determine its future role in the field of vascular access.

Catheters, Indwelling↗
PubMed2001

[Panorama ultrasonography of the abdominal wall for delineation of the anatomy and diagnosis of pathological findings].

PURPOSE: To assess extended field-of-view sonography for delineation of the anatomic structures of the abdominal wall and for the diagnosis of hernia. MATERIAL AND METHODS: In 34 cases (24 probands, 10 patients with abdominal wall defects) extended field-of-view sonography of the abdominal wall was performed with a 7.5 MHz transducer. Dynamic alignment of real-time images allows for depiction of regions of up to 60 cm in a single extended field-of-view image. A standardized axial image was obtained above and below the arcuate line and at the level of the defect, respectively. All images were evaluated by two blinded readers regarding the visibility of the anatomic structures and the delineation and extent of pathological changes. RESULTS: The abdominal wall was delineated with extended field-of-view sonography in all patients with a good image quality. The linea alba, the rectus muscle and the three lateral abdominal muscles, the rectus sheath, the peritoneum, and the subcutaneous fatty tissue were visible. In the patients with abdominal wall defects, the hernial sac with its contents, the extension of the defect, and the surrounding structures were clearly delineated. CONCLUSION: Extended field-of-view sonography allows for easily surveyed and reproducible documentation of the ultrasound examination of the abdominal wall. It is especially useful for the preoperative planning in patients with abdominal wall defects.

Abdominal Muscles↗