Kj Wolf

Dual energy CT of peripheral arteries: Effect of automatic bone and plaque removal on image quality and grading of stenoses

PURPOSE To evaluate the effect of automatic bone and plaque removal on image quality and grading of steno-occlusive lesions in patients undergoing dual energy CT angiography (CTA) of lower extremity. MATERIALS AND METHODS Dual energy (DE) runoff CTA was performed in 50 patients using the following parameters: collimation 2 x 32 x 0.6; tube potentials, 80 kV and 140 kV; reconstructed slice thickness 1mm. 100 mL iomeprol 400 and 50 mL saline were injected at 4 mL/s. Separate datasets were calculated for each of the two tubes and used to generate automatically bone-subtracted images (ABS) as well as bone and plaque subtracted images (ABPS). Residual bone in the ABS dataset was removed manually (=ABS-B dataset). In addition, a weighted average dataset from both dual energy acquisitions resembling a routine 120 kV CT acquisition was used for standard manual bone subtraction (MBS). Operator time for bone removal was measured. Effectiveness of bone subtraction and presence of vessel erosions was assessed by two readers in consensus. Stenosis grading in plaque subtracted and unsubtracted images was assessed and correlated. RESULTS Residual bone fragments (ribs: 46%, patella: 25%, spine: 4%, pelvis: 2%, tibia 2% of patients) were only observed with ABS. The time needed to manually remove these residual bones was 2.1+/-1.1 min and was significantly lower than the duration of manual bone removal (6.8+/-2.0 min, p<0.0001, paired t-test). A total of 1159 arteries were analyzed. Compromising vessel erosions were observed less frequently in the ABS-B dataset (10.6%) than in the MBS dataset (15.2%, p<0.001, wilcoxons signed rank test). A total of 817 steno-occlusive lesions were assessed. While the agreement of grading of steno-occlusive lesions was good at the levels of the aorta and the pelvic arteries (kappa=0.70 in both, Cohens kappa statistics), it was moderate at the level of the thigh arteries (kappa=0.57) and poor at the level of the calf (kappa=0.16). CONCLUSION DE CTA has substantial advantages over conventional CTA. Automatic bone subtraction is more time efficient and reliable. Automatic plaque subtraction for the first time provides a true CTA-luminogram which is easy to interpret and reduces the need for further post-processing. DE CTA provides best results in arteries of the thigh; below the knee, plaque subtraction is less accurate.

MRI of the thorax during whole-body MRI: evaluation of different MR sequences and comparison to thoracic multidetector computed tomography (MDCT).

To evaluate the accuracy of four MR sequences used as part of a whole‐body MRI protocol to detect pulmonary lesions in cancer patients.

The value of combined soft-tissue and vessel visualisation before transarterial chemoembolisation of the liver using C-arm computed tomography

The purpose of the study was to prospectively evaluate intrahepatic vessel depiction on C-arm CT (CACT) and the influence of the additional combined tissue and three-dimensional vessel visualisation on the positioning of the TACE catheter in comparison to DSA alone. Thirty consecutive patients scheduled for their first transarterial chemoembolisation underwent biphasic CACT and DSA of the liver. After assessing the DSA images for procedure planning, the CACT images were reviewed. The number and origin of the tumour-feeding arteries and the ideal position of the catheter for TACE on both DSA and CACT were assessed and correlated. The number of vessels identified as tumour feeders in each patient was significantly higher using additional CACT than on DSA alone (CACT: 4.0 ± 1.7; DSA: 3.3 ± 1.4; P = 0.003, t-test). After considering CACT, in 50% of the patients the catheter position was changed for TACE. Segmental portal vein thrombosis was seen in three patients on CACT, but in only one on DSA. As CACT depicts soft tissue and small vessels with high spatial resolution, tumour vessel allocation is facilitated, and ideal catheter position for TACE can be more accurately identified. The high impact of CACT on the TACE procedure suggests the benefits of its routine use for all patients undergoing their first TACE.

Low contrast dose voiding urosonography in children with phase inversion imaging

Voiding urosonography (VUS) using a microbubble contrast agent has been introduced as an alternative technique in the diagnosis of vesicoureteral reflux (VUR). This study was undertaken to assess if phase inversion ultrasound (PIUS), a recent microbubble specific imaging technique, has advantages over fundamental in VUS and if it allows a reduction of contrast agent dose. Forty-three children with suspected VUR (aged 3 days–12 years, average of 3.9 years) with 92 kidney-ureter units (KUU) were included. Everyone obtained a baseline US scan that was followed by VUS using Levovist as the contrast agent. Constant switching between fundamental and PIUS performed the enhanced part for comparison. Every child underwent VCUG immediately afterwards. Contrast enhancement was stronger and longer lasting on PIUS than on fundamental US in all 43 cases. Reflux was detected in a total of 21 KUU, out of 92 KUU (23%). PIUS revealed VUR in 18; fundamental in 14 KUU and VCUG depicted 16 cases of reflux (p≥0.29). The mean volume of Levovist dose administered to the bladder was 7.4±3.4% of the bladder volume. VUS using PI mode provided considerably stronger and longer enhancement and slightly improved the detection of VUR. It allowed a reduction of contrast dose and cost by approximately 35% over current dose recommendations for fundamental US.

Do the cardiovascular risk profile and the degree of arterial wall calcification influence the performance of MDCT angiography of lower extremity arteries

ObjectivesTo retrospectively assess the influence of arterial wall calcifications on the accuracy of run-off computed tomographic angiography (CTA) and to analyse whether cardiovascular risk factors are predictors of compromising calcifications.MethodsIn 200 consecutive patients who underwent run-off CTA, calcifications were assessed in pelvic, thigh and calf arteries using a four-point scale. Fifty-nine patients with digital subtraction angiography (DSA) were assessed by both techniques to estimate a threshold of compromising calcifications, defined as a decrease of sensitivity, specificity, PPV or NPV below the lower 95% confidence interval of overall results. Regression analysis was performed to investigate a potential relationship between compromising calcifications and presence of cardiovascular risk factors, advanced patient age and severe peripheral arterial disease (PAD).ResultsThe highest Ca++-score was chosen as the cut-off for the regression analysis, as a relevant decrease of specificity (0.91; overall: 0.95) above the knee and of sensitivity (0.66; overall: 0.83), specificity (0.65; overall: 0.93), positive predictive value (PPV) and negative predictive value (NPV) below the knee was observed. In the pelvic and thigh arteries, severe PAD (Fontaine Stage ≥III) showed the highest odds ratio for compromising calcifications (2.9), followed by diabetes mellitus (2.4), renal failure (2.1) and smoking (1.7). In the calf, renal failure (12.2) and diabetes mellitus (3.3) were the strongest predictors.ConclusionsPatients with diabetes and renal failure should be considered as candidates for alternative vessel imaging in order to avoid inconclusive examination results.

[Dual energy CT of the peripheral arteries: a phantom study to assess the effect of automatic plaque removal on stenosis grading].

PURPOSE To evaluate the accuracy of dual energy (DE)-based plaque removal in a vessel phantom. MATERIALS AND METHODS Acrylic vessel phantoms of different diameters (3, 5, 8 mm), degrees of stenoses (25 - 100%) and plaque densities (300 - 750 HU) were filled with contrast-enhanced blood (150 - 450 HU). Dual source CT was used for simultaneous image acquisition at 80 and 140 kV. Beside a DE-based plaque-subtracted dataset (DE-PS), a virtual 120 kV non-plaque subtracted dataset (N-PS) was generated. Agreement between the known and measured luminal diameter in both datasets was determined using Lins concordance correlation coefficient (kappaLin). RESULTS A total of 8260 measurements were taken. The correlation of measured diameter in DE-PS images was excellent (kappaLin = 0.83 - 0.96) for 5 - 8 mm vessel phantoms with high luminal enhancement (300 - 450 HU) and plaque density (500 - 750 HU), moderate (kappaLin = 0.6 - 0.67) for 5 mm vessels with lower luminal enhancement and plaque density and poor (kappaLin = 0.10 - 0.64) in the 3 mm vessels. The correlation of N-PS-based stenosis quantification was excellent (kappaLin = 0.86 - 0.99) for 5 - 8 mm vessel phantoms if the contrast between lumen and plaque was above 100 HU. The correlation decreased in 3 mm vessels (kappaLin = 0.45 - 0.93), while the lowest correlation was observed for the lowest contrast between plaque and vessel lumen. CONCLUSION Automatic DE-based plaque removal is highly effective for heavily calcified plaques and high luminal enhancement in larger diameter vessels > or = 5 mm). However, accuracy is limited for low density calcified plaque, lower luminal enhancement and smaller caliber vessels mainly due to poor specificity.

[Effects of MRI-assayed microvascular permeability on the accumulation of vinorelbine in xenograft tumors].

PURPOSE To determine the effects of MRI-assayed vascular leakiness on the delivery of macromolecular therapeutics to tumors. MATERIALS AND METHODS MDA-MB 435 tumors, subcutaneously implanted into nude rats were treated with a single dose of bevacizumab at levels of 0.1 mg (n = 5) or 1.0 mg (n = 10) or received saline (control animals, n = 8). After 24 hours, albumin-(Gd-DTPA) (30)-enhanced MRI was performed. Just prior to MRI, the cytotoxic drug vinorelbine was administered intravenously. Upon completion of the MR experiment, tumor vinorelbine concentrations were quantified by high performance liquid chromatography (HPLC). Vascular leakiness (K (PS)) was calculated based on the MRI data using a pharmacokinetic model. RESULTS K (PS) was calculated as 3.70 +/- 1.12 (control tumors), 1.95 +/- 0.70 (0.1 mg group) and 0.75 +/- 0.46 microl min (-1)cm (-3) (1.0 mg group). K (PS) was significantly higher in the control group compared to the 1.0 mg bevacizumab group. Vinorelbine concentrations were measured as 409.4 +/- 109.7 (control tumors), 387.5 +/- 47.5 (0.1 mg group) and 250.7 +/- 71.9 (1.0 mg group). These differences were not significant. A moderate and significant correlation was found between K (PS) and Vinorelbine concentrations in tumors (r = 0.49, p < 0.05). CONCLUSION MRI-assayed K (PS) based on dynamic MRI enhanced by albumin-(Gd-DTPA) (30) correlated significantly with vinorelbine accumulation in experimental xenograft tumors under angiogenesis inhibition. Thus, the MRI technique applied in our study could potentially help to predict accumulation of macromolecular cytotoxic drugs and to optimize individual therapeutic regimes in tumors.

[Flat-detector CT-based electromagnetic navigation].

ZusammenfassungMit der Flachdetektor-CT (FD-CT) am Angiographiegerät steht zur Intervention eine bildgebende Technik zur Verfügung, die zur elektromagnetischen Navigation im Rahmen perkutaner Punktionen genutzt werden kann. Der vorliegende Beitrag stellt die Funktionsweise eines elektromagnetischen Navigationssystems dar und erläutert den Ablauf einer elektromagnetisch navigierten Punktion und die Einsatzmöglichkeiten eines solchen Systems in der klinischen Praxis.AbstractFlat-detector CT coupled to an angiography device provides an imaging technique for interventions which can be used for electromagnetically navigated percutaneous punctures. This report explains the functionality of an electromagnetic navigation system and describes the course of an electromagnetically navigated puncture and the capabilities of such a system in the clinical routine.

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

Auf Flachdetektor-CT basierende elektromagnetische Navigation@@@Flat-detector CT-based electromagnetic navigation

ZusammenfassungMit der Flachdetektor-CT (FD-CT) am Angiographiegerät steht zur Intervention eine bildgebende Technik zur Verfügung, die zur elektromagnetischen Navigation im Rahmen perkutaner Punktionen genutzt werden kann. Der vorliegende Beitrag stellt die Funktionsweise eines elektromagnetischen Navigationssystems dar und erläutert den Ablauf einer elektromagnetisch navigierten Punktion und die Einsatzmöglichkeiten eines solchen Systems in der klinischen Praxis.AbstractFlat-detector CT coupled to an angiography device provides an imaging technique for interventions which can be used for electromagnetically navigated percutaneous punctures. This report explains the functionality of an electromagnetic navigation system and describes the course of an electromagnetically navigated puncture and the capabilities of such a system in the clinical routine.