6 research outputs found
Fluid preinjection for microwave ablation in an ex vivo bovine liver model assessed with volumetry in an open MRI system
PURPOSEWe aimed to detect possible differences in microwave ablation (MWA) volumes after different fluid preinjections using magnetic resonance imaging (MRI).MATERIALS AND METHODSMWA volumes were created in 50 cuboid ex vivo bovine liver specimens (five series: control [no injection], 10 mL water, 10 mL 0.9% NaCl, 10 mL 6% NaCl, and 10 mL 12% NaCl preinjections; n=10 for each series). The operating frequency (915 megahertz), ablation time (7 min), and energy supply (45 watts) were constant. Following MWA, two MR sequences were acquired, and MR volumetry was performed for each sequence.RESULTSFor both sequences, fluid preinjection did not lead to significant differences in MWA ablation volumes compared to the respective control group (sequence 1: mean MWA volumes ranged from 7.0±1.2 mm [water] to 7.8±1.3 mm [12% NaCl] vs. 7.3±2.1 mm in the control group; sequence 2: mean MWA volumes ranged from 4.9±1.4 mm [12% NaCl] to 5.5±1.9 mm [0.9% NaCl] vs. 4.7±1.6 mm in the control group). The ablation volumes visualized with the two sequences differed significantly in general (P < 0.001) and between the respective groups (control, P †0.001; water, P < 0.001; 0.9% NaCl, P < 0.001; 6% NaCl, P †0.001; 12% NaCl, P < 0.001). The volumes determined with sequence 1 were closer to the expected ablation volume of 8 mL compared to those determined with sequence 2.CONCLUSIONFor the fluid qualities and concentrations assessed, there is no evidence that fluid preinjection results in larger coagulation volumes after MWA. Because ablation volumes determined by MRI vary with the sequence used, interventionalists should gain experience in how to interpret postinterventional imaging findings (with the MR scanner, sequences, and parameters used) to accurately estimate the outcome of the interventions they perform
Applications for diagnostic noninvasive and therapeutically-invasive imaging in an open 1.0 tesla MRI
Einleitung: Die in dieser Promotionsschrift vorgelegten Originalarbeiten
wurden allesamt in einem 1,0-Tesla-MRT mit offenem Scannerkonzept
durchgefĂŒhrt. Es handelt sich um Studien sowohl zu diagnostischer (1.+2.)
sowie interventionell-therapeutischer (3.) Bildgebung. 1.+2.: Ein nicht
invasives 2D-Time-of-Flight-Magnetresonanz-Angiographie-Protokoll ohne
Kontrastmittel (TOF-MRA) bzw. ein triggered-angiography-non-contrast-enhanced-
Protokoll (TRANCE-MRA) wurden fĂŒr die arterielle Darstellung der unteren
ExtremitÀt mit der digitalen Subtraktionsangiographie (DSA) als Goldstandard,
verglichen. 3.: Die ErgebnisqualitÀt der im oMRT in nahezu Echtzeit-Bildgebung
durchgefĂŒhrten minimalinvasiven Zystenaspiration wurde an Patienten mit
symptomatischen, nervenkomprimierenden lumbosakralen Zysten untersucht.
Methodik: 1.+2.: Es wurden 1134 bzw. 1782 GefĂ€Ădurchmesser (TOF-MRA bzw.
TRANCE-MRA) in jeweils 81 definierten Segmenten prospektiv gemessen und mit
der entsprechenden DSA patientenspezifisch bei 7 (4 Frauen, 3 MĂ€nner;
Durchschnittsalter: 68 Jahre) bzw. 11 Patienten (8 MĂ€nner, 3 Frauen;
Durchschnittsalter: 66 Jahre) verglichen. Aufgrund evidenter Symmetrie
(rechts/links) wurden die 81 Segmente zu 41 Segmenten fĂŒr eine höhere
statistische Aussagekraft konsolidiert. 3.: 11 Patienten mit symptomatischen
lumbosakralen Zysten wurden mittels interventioneller Freihand-
Zystenaspiration behandelt. Ergebnisse: 1.: FĂŒr die 41 symmetrischen Segmente
konnten 25 ausgezeichnete, sehr gute und gute (n=11 > 0,8; n=4 > 0,7; n=10 >
0,5), 7 mĂ€Ăige bis geringe (n=4 > 0,3 und n=3 †0,3), sowie 2 statistisch
nicht aussagekrÀftig korrelierbare, 3 inverse und 4 nicht messbare
Korrelationen verzeichnet werden. Die arterielle Becken- und Oberschenkel-
Hauptstrombahn erzielte die besten Korrelationen und lieĂ sich am solidesten
darstellen. 2.: Insgesamt wurden 34 ausgezeichnete, sehr gute und gute (n=13 >
0,8, n=0 > 0,7; n=11 > 0,5), sowie 4 mĂ€Ăige bis geringe (n=2 > 0,3; n=2 †0,3)
Korrelationen erhoben. In der Becken-Bein-Etage wurden alle Segmente in der
DSA vergleichsweise etwas gröĂer gemessen als in der TRANCE-MRA. In der
Oberschenkeletage maĂen 6 Segmente kleiner, 3 gleich und 2 gröĂer als in der
DSA. In der Unterschenkeletage waren bis auf den Tractus tibiofibularis die
gemessenen Segmente in der TRANCE-MRA gröĂer. Schlussfolgerung: 1. Die TOF-MRA
ist im oMRT in ca. 60-90 Minuten durchfĂŒhrbar und fĂŒhrt zu guten Ergebnissen
in der Visualisierung der arteriellen Hauptstrombahn des Beckens sowie der
Oberschenkeletage, wÀhrend die Visualisierung der Unterschenkeletage
optimierungsbedĂŒrftiger ist. 2. Die TRANCE-MRA ist in ca. 50 Minuten
durchfĂŒhrbar. GefĂ€Ădurchmesser werden im Vergleich zur DSA in gröĂeren
Arterien dabei tendenziell etwas kleiner, in kleineren etwas gröĂer gemessen.
3. Jeder Patient verspĂŒrte eine Besserung nach erfolgreicher Zystenaspiration.
Im Follow-up nach einem Jahr konnten keine Rezidive verzeichnet werden.Introduction: All original studies presented in this doctorate thesis were
implemented in an open MRI at 1.0 Tesla. They deal with diagnostic (1+2) and
interventional-therapeutic (3) imaging. 1+2: A non-invasive non-contrast-
enhanced 2D-time-of-flight-magnetic-resonance-angiography-protocol (TOF-MRA)
respectively triggered-angiography-non-contrast-enhanced-protocol (TRANCE-MRA)
were compared for the arterial imaging of the lower extremity using the
digital subtraction angiography (DSA) as the gold standard. 3: The quality of
the almost real-time imaging results of minimally invasive cyst aspiration
performed in an oMRI was investigated on patients suffering from nerve-
compressing lumbosacral cysts. Methods: 1+2: 1134 respectively 1782 vascular
diameters (TOF-MRA respectively TRANCE-MRA) in 81 defined segments each were
prospectively measured in 7 patients (4 women, 3 men; average age 68),
respectively 11 patients (8 men, 3 women; average age 66) and compared with
the corresponding DSA. For symmetry considerations (right/left), 81 segments
were consolidated to 41 segments for a higher statistical validity. 3: 11
patients with symptomatic lumbosacral cysts were treated using interventional
freehand cyst aspiration. Results: 1: For the 41 symmetric segments, a total
of 25 excellent, very good and good correlations (n=11 > 0.8; n=4 > 0.7; n=10
> 0.5), 7 mediocre to low (n=4 > 0.3 and n=3 †0.3), 2 statistically
insignificantly correlatable, 3 inverse and 4 non-measurable correlations were
determined. The pelvic and femoral arteries achieved the best correlations
with the most reliable images. 2: A total of 34 excellent, very good and good
(n=13 > 0.8, n=10 > 0.7; n=11 > 0.5), as well as 4 mediocre to low (n=2 > 0.3;
n=2 †0.3) correlations were ascertained. At pelvis-leg-level, the results of
the DSA-measured segments were slightly larger compared to TRANCE-MRA. At
thigh level, the measurements of 6 segments were smaller, 3 the same and 2
larger than measured with DSA. At lower leg level, segments measured with
TRANCE-MRA were larger except the tractus tibiofibularis. 3: Seven of eleven
cysts in the lumbosacral area were aspirated successfully. Four cysts (8.8±3.8
mm) could not be aspirated. Conclusion: 1. The TOF-MRA in the oMRI takes
approximately 60-90 minutes with good visualization results for the pelvic and
femoral arteries. The visualization results of the lower leg level require
improvement. 2. The TRANCE-MRA takes approximately 50 minutes. Compared to the
DSA, the measurements of vascular diameters tend to be slightly smaller in
larger and slightly larger in smaller arteries. 3\. All patients felt better
after successful cyst aspiration. No relapses were recorded during the follow-
up one year later