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J Trübenbach

Publications and source records attributed to J Trübenbach.

At least 19 recordsLinked to original sources
PubMed2003

[Radiofrequency ablation: basic principles, techniques and challenges].

Radiofrequency (RF) thermal ablation is a promising and rapidly evolving technique for the minimal invasive treatment of liver malignancies. Until a few years ago, conventional RF treatment performed with a single monopolar electrode produced thermal necrosis lesions not exceeding 1.6 cm in diameter. Substantial improvements in the RF technique included the development of high-power generators (up to 250 watts) combined with open-perfused electrodes, internally cooled-tip electrodes or expandable electrode needles, capable of ablating an area of over 5 cm in diameter. Moreover, angiographically and pharmacologically assisted strategies were introduced for expanding the volume of RF-induced coagulation necrosis. This article presents a synopsis of current RF techniques and reviews the basic principles of RF ablation with the goal of providing guidance for optimal results.

Animals↗
PubMed2003

Radiopaque markers in endovascular stents--benefit and potential hazards.

AIM: The primary objective of this study was to evaluate the impact of radiopaque markers on stent visibility. The secondary objective was to investigate the impact of such radiopaque markers on localized corrosion at the stent corpus-marker interfaces. MATERIAL AND METHODS: The radiopacity of the following stents was evaluated at different fluoroscopy modes (spotfilm, continuous fluoroscopy, 15 p/s, 7.5 p/s, 3 p/s): Memotherm Flexx (FX), Memotherm Luminexx (LX)(Bard), SMART (SM), SMARTeR (SMR)(Cordis). Four readers evaluated a total of 3200 images (160 per stent per fluoro mode) according to the following radiopacity score (RS): 0 = no stent visible, 1 = poor, 2 = acceptable, 3 = good, and 4 = very good stent visibility. LX and SMR stents (n = 5/group) were subjected to potentiodynamic polarization testing in de-aerated Hanks salt solution at 37 degrees C using a potentiostat. Palmaz-Schatz stents (n = 3) were used as the control group for comparative evaluation. The corrosion current density (I corr ) and the breakdown value (E bd ) were compared parameters of interest. RESULTS: At the spotfilm mode the LX, the SM and the SMR were rated well to very well visible in 99 %, 96 %, 96 %, and the FX only in 64 %. At 7.5 p/s (standard fluoro mode) the LX was considered to be well to very well visible in 77 %, followed by the SMR in 12.5 %, the SM in 1 %, and the FX in 0 %. The SMR stents exhibited the highest E bd values (802 +/- 112 mV vs SCE), while the LX stents exhibited the lowest E bd values (155 +/- 38 mV vs SCE). Also, the average E bd values for the SMR stents were better than those exhibited by the PS stents (503 +/- 107 mV vs SCE). CONCLUSION: Stent radiopacity can be increased significantly with the help of radiopaque markers (p < 0,0001 LX vs. FX). However, the surface condition of the stent corpus and the mode of attachment of the marker onto the corpus may have a significant impact on the uniformity of the final corrosion behavior. It is not feasible to determine the clinical impact of this localized corrosion behavior from this in vitro study. Further experimentation is recommended to ascertain the same.

Coated Materials, Biocompatible↗
PubMed2003

[Radiofrequency ablation ex vivo: comparison of the efficacy of impedance control mode versus manual control mode by using an internally cooled clustered electrode].

PURPOSE: To compare the effectiveness of pulsed (impedance control mode) and non-pulsed (manual control mode) radiofrequency ablation (RFA) by using an internal cooled-clustered electrode. MATERIALS AND METHODS: Ex vivo RF ablations (n = 93) were performed with a 200 W RF generator (Model-Cooled Tip, Radionics, USA) in 10 bovine livers, using the impedance and manual control mode. In the impedance control mode, the generator automatically adjusted the applied RF power to the tissue impedance measured during RF ablation. In the manual control mode, the application of the RF power was constant. Both applications were investigated in a capacity range between 5 and 200 W. The duration for each RF ablation was between 2 and 60 minutes. After RF ablation, the short axis diameter of the necrosis was determined macroscopically and the peripheral zone of the necrosis histologically. RESULTS: The impedance control mode produced lesions with short axis diameters of 5.3 +/- 0.3 cm at a power of 200 W after 60 minutes of RF ablation and the manual control mode lesions with short axis diameters of 4.1 +/- 0.4 cm at a power of 70 W after 8 +/- 2 minutes of RF ablation. The impedance control mode increased significantly the time of RF ablation with higher power and the size of necrosis (p < 0.01). CONCLUSION: In comparison to non-pulsed RF ablation, pulsed RF ablation with internal cooled-clustered electrodes significantly increases the size of the lesions and represents a methodical optimization in our opinion.

Animals↗
PubMed2001

MR cholangiography in the diagnosis of sclerosing cholangitis in Langerhans' cell histiocytosis.

Langerhans' cell histiocytosis (LCH) is a disorder of histiocytic proliferation that primarily affects infants. Imaging findings of a rare case of lung and liver involvement in an adult are presented. High-resolution computed tomography (HRCT) of the lungs showed confluent thin-walled cystic air spaces compatible with advanced LCH. Liver CT and MRI revealed unspecific signs of fatty infiltration. Irregular widening of peripheral bile ducts was displayed in breath-hold MR cholangiography. This pattern is considered characteristic for sclerosing cholangitis and should support the diagnosis of LCH in case of concomitant cystic pulmonary disease, even in adult patients.

Aged↗
PubMed2001

Biphasic spiral CT of the liver: automatic bolus tracking or time delay?

The aim of this study was to evaluate the value of automatic bolus tracking for biphasic spiral CT of the liver in comparison with time delay examinations. Forty patients scheduled for a biphasic spiral CT of the liver randomly were examined either with time delay of 25 s for the arterial phase and 55 s for the portal-venous phase (n = 20), or with an automatic scan start triggered by contrast enhancement in the aorta (n = 20). Examinations were performed with 120 ml of contrast material and a flow rate of 4.0 ml/s. Density measurements of the aorta, of the liver parenchyma, and of the spleen were obtained by means of regions of interest (ROI). The end of the arterial phase was considered when hepatic parenchymal enhancement was greater than 20 HU. In all patients of the group with automatic bolus tracking arterial scanning was completed in the arterial phase of the liver. In 25 % of patients with fixed time delay, however, an enhancement of liver parenchyma during arterial phase greater than 20 HU was observed. During the portal-venous phase there was no significant difference in parenchymal enhancement between both groups. Automatic bolus tracking allows an individualized timing of the arterial phase in biphasic spiral CT of the liver. The timing is more accurate than in time delay scanning.

Adult↗
PubMed2001

Automatic bolus tracking in monophasic spiral CT of the liver: liver-to-lesion conspicuity.

The aim of this study was to evaluate the value of automatic bolus tracking for monophasic spiral CT of the liver and to assess the liver-to-lesion conspicuity in comparison with time-delay examinations. In 40 patients scheduled for therapy control of known hypovascular hepatic metastases a monophasic spiral CT was completed either with time delay of 65 s (n = 20) or with automatic bolus tracking in the liver parenchyma (n = 20). Examinations were performed with 120 ml of contrast material and a flow rate of 3.0 ml/s. For automatic bolus tracking a parenchymal enhancement threshold of 40 HU was used. Contrast enhancement in the liver parenchyma and in liver lesions was obtained by means of regions of interest (ROI). Mean parenchymal enhancement was not significantly different between time delay and bolus-tracking group. In 4 of 20 patients in the bolus-tracking group the threshold level of 40 HU was not reached. With automatic bolus tracking a significantly higher liver-to-lesion density difference was observed (P < 0.0001). Automatic bolus tracking allows a better liver-to-lesion conspicuity in monophasic spiral CT. Contrary to recent studies, a significantly higher parenchymal enhancement was not found using automatic bolus tracking.

Adult↗
PubMed2001

[MR-venography using manual flow augmentation in an open low field MR system].

OBJECTIVE: To evaluate the feasibility of signal enhancement in the deep veins by means of manual compression of the calf (flow augmentation) as a new approach to MR venography in open configuration, low-field systems. METHODS: 10 healthy volunteers underwent MR venography of the calf unconstrained and during short localized manual compression. Gradient recalled echo sequences (FLASH, FISP) with repeated single slice acquisition and first-order gradient motion refocussing were tested in four protocols with and without arterial presaturation slabs (scan time 2.2 - 5.0 s per slice). The effect on flow enhancement was rated by means of a signal score. Interventional accessories, particularly an in-room LCD screen, were required for interactive application of compression manoeuvres. RESULTS: Sequences with arterial presaturation slabs were superior to those without regardless of the longer acquisition times. Careful targeting of compression to the mid-time of data acquisition was crucial to obtain marked flow acceleration. Enhancement was best in the case of proximally applied calf compression. Signal improvement was consistently achieved in the proximal parts of the posterior tibial and peroneal veins, but was only seen in 4/10 volunteers in the distal part of the anterior tibial vein. CONCLUSION: Flow augmentation by means of manual calf compression is a simple and effective complementary approach to MR venography in open configuration, low field MR systems.

Adult↗
PubMed2001

[Primary tumors of the liver: radiologic interventional procedures].

Primary liver tumors are one of the most common malignant tumors worldwide. Surgical resection of the tumors is considered the only potentially curative therapy. It has been estimated that only 20%-30% of patients with HCC (hepatocellular carcinoma) are surgical candidates. For this reason a number of alternative therapies have been used for the treatment of HCC. These include transarterial chemoembolisation (TACE), percutaneous alcohol instillation (PAI) and thermal ablative techniques. Thermal ablation for the treatment of HCC include both freezing (cryoablation) and heating (radiofrequency, microwave, laser and high-intensity focussed sonography) techniques. Of these techniques, percutaneous radiofrequency ablation (PRFA) is increasingly used for the local tumor destruction. The low rate of complications and the technical development increasing the efficacy of PRFA have shown that this is a very promising and safe technique.

Angiography↗
PubMed2000

[Animal experiment studies on the effectiveness of permanent occlusion of the hepatic artery in transarterial chemoembolization].

PURPOSE: To evaluate the effect of permanent occlusion of the hepatic artery on the efficacy of transarterial chemoembolization (TACE) in an animal model. MATERIAL AND METHODS: 12 days after inoculation of the Morris hepatoma 3924 A in 15 male ACI rats, TACE with Mitomycin C (0.25 mg/kgBW) + Lipiodol (0.2 ml/kgBW) without (n = 5) and with permanent occlusion of the hepatic artery (n = 5) was performed. Control group consisted of 5 rats. Tumor volume was determined by MRI (1.0 T, T1 [TR/TE, 400/14 ms]) before and 12 days after therapy. RESULTS: Compared to the control group, TACE without and with permanent occlusion of the hepatic artery showed a significant reduced tumor growth after 12 days (p = 0.017 and p = 0.005). However, permanent occlusion did not improve the retarding effect on tumor growth (p = 0.9). CONCLUSION: The effectiveness of TACE in an animal model using a cytostatic-/lipiodol-emulsion is not improved by permanent occlusion of the hepatic artery.

Animals↗
PubMed2000

[MRI-guided percutaneous radiofrequency ablation of hepatic neoplasms--first technical and clinical experiences].

PURPOSE: To evaluate the safety and efficacy of MR-guided radiofrequency ablation (RFA) of hepatic neoplasms. MATERIAL AND METHODS: 16 hepatic neoplasms (1.3-3.0 cm in diameter) in 11 patients were treated by 22 percutaneous RFA sessions during a prospective study. 16 G, MR-compatible cooled-tip electrodes with active lengths of 2 cm and 3 cm, respectively, were placed under MR-guidance in an open 0.2 Tesla MR system (Magnetom Open, Siemens, Erlangen) using fast T1-weighted sequences. Pretreatment studies, evaluation of tumor necrosis (one week after last RFA), and further follow-up studies every 3 months were performed using 1.5 Tesla MR systems. RESULTS: The mean procedure time was 2.8 (1.5-3.3) h. Complications related to percutaneous treatment were not encountered. 14 of 16 neoplasms (87%) showed no CM enhancement during MRI after the last RFA and were judged to be completely necrotic. In 11 tumors one treatment session was necessary, in 4 tumors two and in one tumor three. Follow-up studies revealed persistent complete necrosis in 13 of 14 (93%) tumors during a period of 3-18 (median: 11.8) months. In 5 patients new intrahepatic tumors developed that were not suitable for further RFA treatment because of their number, size and location. CONCLUSION: MR-guided RFA using single cooled tip electrodes is safe and technically effective for treatment of hepatic neoplasms up to 3 cm in size, however further improvements are necessary.

Adult↗
PubMed2000

[Percutaneous radiofrequency ablation of hepatic neoplasms using a "cluster" electrode--first clinical results].

PURPOSE: To evaluate feasibility, safety and efficacy of percutaneous radiofrequency ablation (RFA) of hepatic neoplasms using a clustered electrode. MATERIAL AND METHODS: Percutaneous, CT-guided RFA using a clustered electrode was performed in 12 patients with a total of 15 hepatic neoplasms (2.0-6.0 cm in diameter). RESULTS: A total of 17 percutaneous RFA was performed. The mean total procedure time was 2.0 h (1.5-2.5 h). Placement of the clustered electrode within the neoplasms using a inter- or subcostal approach under local anesthesia was possible in all cases. Complications related to percutaneous treatment and technical problems were not encountered. Diameter of the ablated areas ranged between 3.0-7.0 cm. Technical success was observed in 13 of 15 neoplasms (86.6%). During a mean follow-up of 7.25 months (range 3-12 months) 8 of 12 neoplasms showed a complete necrosis. CONCLUSION: Percutaneous RFA using a clustered electrode is a feasible, safe and effective procedure for the treatment of hepatic neoplasms up to 6 cm in size.

Adult↗
PubMed2000

Magnetic resonance imaging guided corticosteroid injection of the sacroiliac joints in patients with therapy resistant spondyloarthropathy: a pilot study.

OBJECTIVE: To evaluate magnetic resonance imaging (MRI) guided corticosteroid injections of inflamed sacroiliac (SI) joints in patients with spondyloarthropathy with therapy resistant sacroiliitis. METHODS: We performed 16 injections in 9 patients on an outpatient basis (6 men, 3 women, mean age at onset 24.7 +/- 7.5 yrs). All patients had MRI guided injection of 40 mg triamcinolone acetonide into SI joints using an open 0.2 Tesla unit. Before and 3 months after corticosteroid injection they underwent an MRI examination with a closed 1.5 Tesla unit. RESULTS: Seven of 9 patients reported subjective improvement that lasted at least a mean of 10.8 +/- 5.6 months. Subchondral bone marrow edema on fat suppressed images resolved in 8 patients after corticosteroid injection. CONCLUSION: MRI guided corticosteroid injection of SI joints appears to be an effective and safe procedure without exposure to radiation. It is a useful therapeutic modality, especially in young patients with severe isolated sacroiliitis.

Adolescent↗
PubMed2000

[Corticosteroid injections of the sacroiliac joint during magnetic resonance: preliminary results].

PURPOSE: The aim of this study was to evaluate the advantages of MRguided injections of corticosteroids into the sacroiliac joints (SIJ) in patients suffering from refractory sacroiliitis despite appropriate oral therapy. MATERIALS AND METHODS: At a lowfield open MR, we performed twentyfour infiltrations in 12 patients suffering from persistent buttock pain. Clinical followup and laboratory findings were evaluated every 4 up to 6 weeks. A subjective rating using a dolorimetry scale (0= no pain, up to=10 for most severe pain) was assessed prior to intervention and at three months followup. Morphological changes of the SIJ were examined on a 1.5 Tesla imager before and three months after steroid injections. RESULTS: Adequate positioning of the needle was obtained in all but one case due to a software defect. Clinical improvement was observed in 10 patients with a mean painfree period of 9.6 months. Dolorimetry index decreased from 7.6 +/- 1.5 to 2.9 +/- 1.5. Nonsteroidal antiinflammatory drugs could be discontinued in 4 patients and reduced in 4 others. CONCLUSION: We therefore conclude that MRguided injection of the SIJ is feasible and could be preferred to more conventional methods when technical equipment is available.

Adult↗