Bernd Frericks

Influence of intrahepatic vessels on volume and shape of percutaneous thermal ablation zones: in vivo evaluation in a porcine model.

Objectives:Aim of the study was to evaluate the precise influence of different intrahepatic vessels, vessel sizes, and distances from the applicator on volume and shape of hepatic laser ablation zones in an in vivo porcine model. Materials and Methods:The study was approved by the institutional animal care and use committee. Eighteen computed tomography-guided Nd:YAG laser ablations were performed in the livers of 10 pigs at varying distances from hepatic veins and portal fields. After hepatectomy the livers were cut into 2-mm slices perpendicular to the laser applicator axes. For each ablation zone the maximum achievable (ideal) volume, the segmented (real) volume, the maximum radius, and the radius at the position of adjacent hepatic vessels were determined. The shapes of the ablation zones were evaluated qualitatively. Comparative statistics using the unpaired t test and a multiple linear regression analysis were performed. Results:Ideal and real ablation zone volumes differed by 27.3% (8.6 ± 1.5 mL vs. 6.4 ± 1.1 mL; P < 0.0001). Thirty-eight of 60 (63%) hepatic veins versus 28 of 31 (90%) portal veins within the central slices of the 18 ablation zones led to a reduction of the ablation zones radius, depending on the distance between the vessel and the applicator and the vessel type. Portal fields revealed stronger effects than hepatic veins. The vessel diameter showed no independent effect (P > 0.05). When influencing, all hepatic veins showed a focal indentation whereas portal fields always showed broad flattening of the ablation zone. Conclusions:Portal fields lead to more heat sink than hepatic veins. The effects decreased with the distance between vessel and applicator tip, but less so for portal fields. The 2 vessel types induced considerably different shape alterations of the ablation zones. These results were not dependent on vessel size. This should be considered in the planning of thermal tumor ablations.

Comparison of 1.0 M gadobutrol and 0.5 M gadopentetate dimeglumine-enhanced magnetic resonance imaging in five hundred seventy-two patients with known or suspected liver lesions: results of a multicenter, double-blind, interindividual, randomized clinical phase-III trial

Objective:To evaluate the diagnostic efficacy (accuracy, sensitivity, specificity) of 1.0 M gadobutrol versus 0.5 M gadopentetate for the classification of lesions as either benign or malignant in patients with known or suspected liver lesions. Methods and Materials:A multicenter, phase-III, randomized, interindividually controlled comparison study with blinded reader evaluation was performed to investigate the diagnostic efficacy of a bolus injection of 1.0 M gadobutrol compared with 0.5 M gadopentetate at a dose of 0.1 mmol Gd/kg BW. The imaging protocol included a dynamic 3D-evaluation, static conventional, and fat saturated T1-weighted sequences. MR datasets were evaluated by 3 independent radiologists. The standard of reference was defined by an independent truth panel (radiologist or hepatologist). The safety evaluation included adverse events, vital signs, and physical examination. Results:A total of 497 of 572 patients were eligible for the final efficacy analysis. Noninferiority of gadobutrol-enhanced magnetic resonance imaging (MRI) for the classification of liver lesions was demonstrated on the basis of diagnostic accuracy determined by the on-site investigators (−0.098, 0.021) as well as for the average reader of the blinded evaluation (−0.096, 0.014) (95% confidence interval), compared with the predefined standard of reference. Very similar increases in sensitivity (ranging from ∼10% to ∼55%) and specificity (ranging from ∼1%–∼18%) compared with precontrast MRI were also observed for the 2 contrast agent groups, with maximum differences of 4%.Very similar, low rates of adverse events were recorded for each of the 2 groups. No clinically relevant changes in vital signs or the results of the physical examination were observed in any patient. Conclusion:This study documents evidence for the noninferiority of a single i.v. bolus injection of 1.0 M gadobutrol (0.1 mmol/kg body weight) to 0.5 M gadopentetate (0.1 mmol/kg body weight) in the diagnostic assessment of liver lesions with contrast-enhanced MRI. The known excellent safety profile of gadobutrol was confirmed in this clinical trial and is similar to that of gadopentetate.

Magnetic resonance imaging of experimental inflammatory bowel disease: quantitative and qualitative analyses with histopathologic correlation in a rat model using the ultrasmall iron oxide SHU 555 C.

Objectives:To quantitatively and qualitatively characterize the MR findings of inflammatory bowel disease in a rat model after i.v. injection of the reticuloendothelial system cell specific ultrasmall iron oxide SHU 555 C. Materials and Methods:Colitis was induced in 15 rats using dinitrobenzene sulfonic acid instillation. Five rats served as controls. T1- and T2-weighted spin-echo- and T2*-weighted gradient-echo-sequences were acquired at 2.4 Tesla before and immediately, 15, 45, 60, and 90 minutes, and 24 hours after i.v.-injection of SHU 555 C (0.1 mmol Fe/kg). MR images were evaluated quantitatively regarding thickness and signal-to-noise ratio (SNR) of the bowel wall and qualitatively regarding overall bowel wall signal intensity and the occurrence of bowel wall ulcerations. MR findings were correlated to histology. Results:The inflamed bowel wall was significantly thicker than the noninflamed bowel wall and 90 minutes after contrast injection it showed a significant reduction of SNR in T1- (94 ± 27 vs. 61 ± 29; P < 0.01), T2- (67 ± 26 vs. 28 ± 17; P < 0.05), and T2*- (92 ± 57 vs. 10 ± 7; P < 0.05) weighted images as compared with unenhanced images. At 24 hours, the respective SNR values remained significantly reduced. The signal loss was homogeneous in 12 and focal in 3 of the 15 rats with colitis. Nine rats showed colonic wall ulcerations. In all but one animal (missed focal ulceration) MR findings correlated to the histologic findings. Conclusions:SHU 555 C leads to a significant signal intensity loss of the inflamed bowel wall in T1-, T2- and T2*-weighted images. SHU 555 C enhanced MRI findings correlate well with histologic findings.

Minimal vascular flows cause strong heat sink effects in hepatic radiofrequency ablation ex vivo.

The present paper aims to assess the lower threshold of vascular flow rate on the heat sink effect in bipolar radiofrequency ablation (RFA) ex vivo.

Biphasic blood pool contrast agent-enhanced whole-body MR angiography for treatment planning in patients with significant arterial stenosis.

Objective:To prospectively evaluate diagnostic accuracy of first pass and combined first pass and steady state high-spatial-resolution whole-body magnetic resonance (MR) angiography with a blood pool contrast agent for quantification of arterial stenosis in different vascular territories. Materials and Methods:After Institutional Review Board approval and informed consent, 50 patients with known 50% or greater stenosis in at least one vascular territory; as shown by the standard-of-reference (14 digital subtraction angiographies, 4 computed tomographies, 32 ultrasound examinations), were included. The patients underwent MR angiography at 1.5 Tesla, using a standardized nonbody-weight-adapted i.v. bolus injection of 11 mL gadofosveset trisodium. First pass imaging with 4 different table positions in a whole-body MR scanner (MAGNETOM Avanto, Siemens Healthcare), using individual circulation time determined by a test bolus, was performed. Steady state imaging was performed using an isometric spatial resolution of 1.0 mm. Image quality was rated. Each vascular segment in MR angiography was evaluated by 2 independent and blinded reviewers and the stenosis degree was compared with the preferred standard-of-reference, using a 5-point scale. Differences between first pass and combined MR angiography were assessed with a 95% confidence interval (CI) by applying the adjusted modified &khgr;2 test. Changes in therapy based on the whole-body examination strategy were evaluated. Results:The number of nondiagnostic territories was 24 of 197 (12.2%) for first pass MR angiography and decreased to 3 of 197 (1.5%) after addition of steady state MR angiography. The diagnostic accuracy for quantification of arterial stenosis in combined MR angiography (94.7%; 95% CI: 92.4–97.1) was superior to first pass MR angiography (81.7%; 95% CI: 73.7–89.8; statistically significant). Patient management was changed in 12 of 49 patients, in 7 of 12 patients the change was applied to an additional lesion detected by the whole-body examination strategy. Conclusion:The quantification and detection of arterial stenosis is improved by the steady state high-resolution gadofosveset trisodium-enhanced MR angiography. Additional lesions detected by whole-body examination strategy or differences in stenosis quantification may lead to changes in therapy.

Hepatic transit time analysis using contrast enhanced MRI with Gd-BOPTA: A prospective study comparing patients with liver metastases from colorectal cancer and healthy volunteers.

To find out if the hepatic transit time (HTT) shortening, which was already proven in patients with liver metastases by other modalities, can also be detected with MRI.

Periphere MRA mit einem Blutpool-Kontrastmittel: Vergleich der alleinigen First Pass-MRA mit der kombinierten First Pass und Blutpool-MRA

Ziele: Vasovist (Bayer Schering) ist ein Blutpool-Kontrastmittel fur die MRA. Zusatzlich zur konventionellen First Pass (FP) MRA in der arteriellen Phase erfolgt mit diesem KM die Akquisition hoch aufgeloster Steady State (SS) Bilder wahrend der Blutpoolphase. Ziel unserer prospektiven Studie war der intraindividuelle Vergleich der FP-MRA kombiniert mit SS-Bildgebung im Vergleich zur alleinigen FP-MRA mit Vasovist im Hinblick auf die diagnostische Beurteilbarkeit der arteriellen Segmente unter- und oberhalb des Knies. Methode: Bei 82 Patienten mit pAVK erfolgte zunachst eine „step by step“ FP-MRA (9ml Vasovist @ 1ml/s sowie 30ml Kochsalzlosung @ 0,5ml/s) mit einem 1,5T Scanner (Avanto, Siemens) und 3D T1w-Sequenzen mit einer Voxel-Grose von 0,9×0,9×1,5mm. Anschliesend erfolgte die hoch auflosende SS-Bildgebung bei 0,65×0,65×0,65mm Voxelgrose. Ein verblindeter externer Beobachter beurteilte zunachst nur die FP-MRA und anschliesend die kombinierte FP+SS-MRA. Ergebnis: Es wurden 820 Unterschenkelsegmentarterien beurteilt. In der First Pass-MRA wurden 97,6% dieser Segmente als diagnostisch eingeschatzt, diese Rate konnte durch FP+SS 99,2% gesteigert werden (p<0,05). Oberhalb des Knies waren in der FP-MRA 97% der 403 arteriellen Segmente diagnostisch, fur FP+SS erreichte dieser Wert 100% (p<0,05). In 9,6% der Segmente ergab die SS-Bildgebung zusatzliche diagnostische Informationen (bessere Beurteilbarkeit der Stenosemorphologie oder des Lumens im Stent). Ergebnisse eines zweiten Beobachters werden vorgestellt. Schlussfolgerung: Die Kombination aus FP+SS-MRA mit Vasovist ergab eine volle diagnostische Beurteilbarkeit von 99,2% der Unterschenkelarteriensegmente und 100% der Arterien oberhalb des Knies. Der zusatzliche Einsatz der SS-Bildgebung erhohte die Anzahl der als diagnostisch beurteilbaren Segmente bei einem relativ geringen, aber statistisch signifikanten Anteil. In knapp 10% ergaben sich auserdem zusatzliche diagnostische Informationen. Korrespondierender Autor: Albrecht T Vivantes-Klinikum Neukolln, Institut fur Radiologie und interventionelle Therapie, Rudower Str. 48, 12354 Berlin E-Mail: thomas.albrecht@vivantes.de

Evaluierung von Gefäßanalyse und Volumetrie für die Planung von Leberlebendspenden

Vor einer Leberlebendspende ist eine sorgfaltige Untersuchung des potenziellen Spenderorgans, sowie eine detaillierte Planung und Risikoabschatzung des Eingriffes notwendig. In diesem Artikel werden Methoden der Gefasanalyse und Volumetrie vorgestellt, deren Ergebnisse einen wesentlichen Einfluss auf die Spenderauswahl und Planung der Transplantation haben. Zur Evaluierung der Verfahren wurden an der Medizinischen Hochschule Hannover 29 potenzielle Spender praoperativ untersucht und die Resultate der computergestutzten Auswertung mit den intraoperativen Befunden verglichen. Sowohl die Gefasanatomie als auch die Resektatvolumina zeigten eine sehr gute Ubereinstimmung bzw. Korrelation.