[CT-guided radiofrequency (RF) ablation of osteoid osteoma: clinical long-term results]. / CT-gesteuerte Radiofrequenz (RF)-Ablation von Osteoidosteomen: klinische Langzeitergebnisse.

PURPOSE: To evaluate CT-guided radiofrequency (RF) ablation of osteoid osteoma using internally cooled monopolar RF electrodes for technical success, complications and clinical long-term success. MATERIALS AND METHODS: Between April 1999 and July 2006, 23 patients were treated under general anesthesia with CT-guided RF ablation using an internally cooled monopolar single RF electrode (Cool-tip, Valleylab, TycoHealthcare, Boulder, USA; active tip: 10 mm). For the removal of the nidus, we used either a manual or an automated drill. The technical success was evaluated by a CT scan (MSCT, Siemens Medical Solutions, Forchheim). The clinical long-term success was investigated by questioning patients prior to discharge, and after 6, 12 and 18 months. After 18 months, patients were interviewed on an annual basis. RESULTS: The technical success rate was 100 %. The nidus was located in n = 19 cases at the lower extremity and in n = 4 cases at the upper extremity. Minor complications were observed for n = 2 patients. The mean hospitalization time was 1.5 d (1-2 d). The mean follow-up was 75.9 months (18-120 months) for n = 23 patients. No local recurrence was observed. One patient had intermediate pain one week after RF ablation without recurrent symptoms. CONCLUSION: CT-guided RF ablation using an internally cooled monopolar single RF electrode is an effective and safe minimally invasive method for the treatment of osteoid osteoma with excellent clinical long-term success.

A monoallelic double mutation as a cause for TNF receptor-associated periodic fever syndrome.

Hereditary periodic fever syndromes (HPFSs) are a subset of human autoinflammatory diseases characterized by periodic episodes of fever and signs of inflammation with or without involvement of inner organs. In this paper, we report phenotypic features of an index patient and affected family members that present a previously not described mutation type in the TNFRSF1A gene. The phenotype of a HPFS of affected family members was shown to be associated with two monoallelic mutations in TNFRSF1A. Primarily, the index patient was clinically diagnosed as being affected by familial Mediterranean fever (FMF). However, with molecular genetic analyses, it could be shown that the patient was in fact affected by tumor necrosis factor receptor-associated periodic syndrome, which requires a different therapy when compared with FMF. Thus, molecular genetic analyses of currently known disease loci enable the most precise diagnosis presently available and are consequently the basis for the most effective therapeutic intervention.

Preoperative embolization of cervical spine osteoblastomas: report of three cases.

Our aim was to describe the technique and clinical results of preoperative embolization of cervical spine osteoblastomas. We treated 3 patients with these tumors with transarterial embolization and subsequent surgical excision. In all 3 patients, distal access to the tumor-supplying vessels was gained with a microcatheter and embolization was performed with polyvinyl alcohol particles. No complications occurred. Surgical resection was performed in all patients without relevant bleeding. The postoperative course was uneventful in all patients. Preoperative embolization is a valuable adjunct to the surgical treatment of osteoblastomas of the cervical spine.

Mutation screening for the prothrombin variant G20210A by melting point analysis with the Light Cycler system: atypical results, detection of the variant C20209T and possible clinical implications.

In the differential diagnosis of thrombophilic disorders genotyping of prothrombin and factor V are nowadays performed as a routine analysis. In the following we describe the unusual results of the mutation screening using melting point analysis for two patients and the consecutive detection of the mutation C20209T by sequencing the corresponding gene fragments. The molecular result is discussed with special respect to the medical history, ethnic background and clinical findings of both patients.

Contrast enhanced MR-guided biopsy of hepatocellular carcinoma.

Magnetic resonance (MR)-guided liver biopsy was performed in three patients with hepatocellular carcinoma. The tumor was considered (n = 2) or proven (n = 1) inaccessible with ultrasound or computed tomographic guidance. Because all lesions were poorly delineated on nonenhanced MR imaging, contrast agents (Gd-BOPTA, n = 1; ferucarbotran, n = 2) were applied to facilitate biopsy in an open low-field scanner. Postcontrast tumor conspicuity was fair in the patient receiving Gd-BOPTA and excellent in both patients receiving ferucarbotran, and biopsy was successful in all cases.

[Percutaneous treatment of liver metastases]. / Interventionell-radiologische Therapie bei Lebermetastasen.

Thermal coagulation therapy is a rapidly evolving technique for the treatment of primary and secondary hepatic tumors. Radiofrequency is gaining most of the attention of these techniques due to its superior effectiveness. This article outlines technical considerations, indications and clinical results with RF ablation in the liver.

[Radiofrequency ablation ex vivo: comparison of the efficacy of impedance control mode versus manual control mode by using an internally cooled clustered electrode]. / Radiofrequenzablation ex-vivo: Vergleich der Effektivität von impedance control mode versus manual control mode unter Verwendung einer geschlossen perfundierten Cluster-Ablationssonde.

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.

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.

[Radiofrequency ablation: basic principles, techniques and challenges]. / Radiofrequenzablation: Grundlagen, Techniken und Herausforderungen.

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.

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.

[MR-venography using manual flow augmentation in an open low field MR system]. / MR-Venographie am offenen Niederfeldtomographen unter Verwendung manueller Flussaugmentation.

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.

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.

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.

[Primary tumors of the liver: radiologic interventional procedures]. / Primäre Tumore der Leber: Radiologisch-Interventionelle Verfahren.

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.

[MRI-guided percutaneous radiofrequency ablation of hepatic neoplasms--first technical and clinical experiences]. / MRT-gestützte perkutane Radiofrequenzablation hepatischer Neoplasien--Erste technische und klinische Erfahrungen.

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.

Growth characteristics and imaging properties of the morris hepatoma 3924A in ACI rats: a suitable model for transarterial chemoembolization.

PURPOSE: For experimental studies investigating modalities and efficacy of transarterial chemoembolization (TACE) in hepatocellular carcinoma (HCC) an animal model resembling the human situation as closely as possible would be appropriate. Specifically, reproducible tumor growth characteristics with the capability for appropriate in vivo imaging to monitor treatment efficacy are required. METHODS: Morris hepatoma 3924A was implanted into the liver of 30 ACI rats. Tumor growth was followed by angiography (n = 10), ultrasound (US, n = 30), native computed tomography (CT, n = 16), and native magnetic resonance imaging (MRI, n = 30) between day 8 and day 36 after implantation. The radiological morphological characteristics were compared with the macroscopic and microscopic histological findings of the explanted tumors. RESULTS: In all 30 animals a solitary liver tumor was found and macroscopically no signs of metastases, ascites, or peritoneal tumor were visible. On histopathological examination tumor sizes ranged between 27 +/- 3 mm(3) (day 8) and 3468 +/- 79 mm(3) (day 36). The first signs of tumor necrosis occurred at day 16. US allowed tumor visualization from day 8, MRI from day 8, angiography from day 10, and CT from day 14. CONCLUSIONS: The tumor model has the potential to be used for the visualization of tumor growth by MRI and US. The potential for monitoring therapeutic effects of TACE needs to be investigated.