Computer oriented image acquisition of the liver: Toward a better numerical model for radiofrequency ablation.

Simulating physiological interventions for planning purposes requires an accurate virtual liver model as computation input. To best meet the demands the data acquisition has to be oriented on image processing purposes. We provide a CT imaging protocol which makes it possible to extract much more vessels with the same segmentation algorithms than when using them on data sets from the clinical routine. Medical evaluation of physiological models demand a statistical evaluation in a pre-clinical study, that means in a first step reproducible results for a large number of subjects. So data acquisition should be as automatic as possible without neglecting modeling demands. Image quality should be reproducible to guarantee an ongoing high quality of image processing results. We evaluate the protocol by comparison of segmentation results with results achieved on standard data sets from clinical routine using the same segmentation methods. Results show that typically up to ten times more vessels can be extracted and the surface accuracy is improved.

Graz Endocrine Causes of Hypertension (GECOH) study: a diagnostic accuracy study of aldosterone to active renin ratio in screening for primary aldosteronism.

BACKGROUND: Primary aldosteronism (PA) affects approximately 5 to 10% of all patients with arterial hypertension and is associated with an excess rate of cardiovascular complications that can be significantly reduced by a targeted treatment. There exists a general consensus that the aldosterone to renin ratio should be used as a screening tool but valid data about the accuracy of the aldosterone to renin ratio in screening for PA are sparse. In the Graz endocrine causes of hypertension (GECOH) study we aim to prospectively evaluate diagnostic procedures for PA. METHODS AND DESIGN: In this single center, diagnostic accuracy study we will enrol 400 patients that are routinely referred to our tertiary care center for screening for endocrine hypertension. We will determine the aldosterone to active renin ratio (AARR) as a screening test. In addition, all study participants will have a second determination of the AARR and will undergo a saline infusion test (SIT) as a confirmatory test. PA will be diagnosed in patients with at least one AARR of >or= 5.7 ng/dL/ng/L (including an aldosterone concentration of >or= 9 ng/dL) who have an aldosterone level of >or= 10 ng/dL after the saline infusion test. As a primary outcome we will calculate the receiver operating characteristic curve of the AARR in diagnosing PA. Secondary outcomes include the test characteristics of the saline infusion test involving a comparison with 24 hours urine aldosterone levels and the accuracy of the aldosterone to renin activity ratio in diagnosing PA. In addition we will evaluate whether the use of beta-blockers significantly alters the accuracy of the AARR and we will validate our laboratory methods for aldosterone and renin. CONCLUSION: Screening for PA with subsequent targeted treatment is of great potential benefit for hypertensive patients. In the GECOH study we will evaluate a standardised procedure for screening and diagnosing of this disease.

Towards validation for physiological models in intervention planning.

Computer supported treatment planning systems aim at predicting treatment results. Recently attacked challenges base not only on anatomical findings, but include physiological processes. This way, interventions which are highly depending on patient physiology become predictable and can be supported in computer based planning. Though the necessity to validate computations used for treatment planning is unquestioned available models lack validation. This contribution discusses challenges for designing a validation study for the example intervention of radiofrequency ablation (RFA) in the liver.

Fatal hemobilia resulting from an iatrogenic arteriobiliary fistula as a rare complication of transjugular liver biopsy.

Transjugular liver biopsy is an important tool for diagnosing and/or staging of advanced liver disease. This procedure is considered safe even in the presence of severe coagulopathy, although rare fatal complications have been described. We herein report the first case of fatal hemobilia after transjugular liver biopsy. A patient with alcoholic liver cirrhosis developed hematemesis 1 day after transjugular liver biopsy. Upper gastrointestinal endoscopy revealed bleeding from the papilla of Vater. Despite early intervention by angiography and embolization of an arteriobiliary fistula, the patient deteriorated and ultimately died due to multiorgan failure.

Hepatic encephalopathy following transjugular intrahepatic portosystemic shunt (TIPS): management with L-ornithine-L-aspartate and stent reduction.

Hepatic encephalopathy (HE) is a common problem after insertion of a trans-jugular intrahepatic portosystemic shunt (TIPS), which may be difficult to manage. We present a case of severe post-TIPS HE unresponsive to high doses of L-ornithine-L-aspartate (LOLA) despite reduction of venous ammonia levels in a dose-dependent fashion. Ultimately, high-grade HE was successfully treated by a reduction stent and the patient subsequently underwent successful liver transplantation.

Routine use of three-dimensional contrast-enhanced moving-table MR angiography in patients with peripheral arterial occlusive disease: comparison with selective digital subtraction angiography.

PURPOSE: To compare the diagnostic accuracy of contrast-enhanced (CE) three-dimensional (3D) moving-table magnetic resonance (MR) angiography with that of selective digital subtraction angiography (DSA) for routine clinical investigation in patients with peripheral arterial occlusive disease. METHODS: Thirty-eight patients underwent CE 3D moving-table MR angiography of the pelvic and peripheral arteries. A commercially available large-field-of-view adapter and a dedicated peripheral vascular phased-array coil were used. MR angiograms were evaluated for grade of arterial stenosis, diagnostic quality, and presence of artifacts. MR imaging results for each patient were compared with those of selective DSA. RESULTS: Two hundred and twenty-six arterial segments in 38 patients were evaluated by both selective DSA and MR angiography. No complications related to MR angiography were observed. There was agreement in stenosis classification in 204 (90.3%) segments; MR angiography overgraded 16 (7%) segments and undergraded 6 (2.7%) segments. Compared with selective DSA, MR angiography provided high sensitivity and specificity and excellent interobserver agreement for detection of severe stenosis (97% and 95%, kappa = 0.9 +/- 0.03) and moderate stenosis (96.5% and 94.3%, kappa = 0.9 +/- 0.03). CONCLUSION: Compared with selective DSA, moving-table MR angiography proved to be an accurate, noninvasive method for evaluation of peripheral arterial occlusive disease and may thus serve as an alternative to DSA in clinical routine.

Crimping and repositioning of a maldeployed balloon-expandable arterial stent using a gooseneck snare.

PURPOSE: To describe a technique for repositioning a fully deployed iliac stent from the infrarenal aorta into the common iliac artery (CIA). CASE REPORT: A 58-year-old man was undergoing treatment for a significant right CIA stenosis when a 7x24-mm Palmaz Genesis medium stent was mistakenly deployed in the infrarenal aorta. With the stent still over the guidewire, an 8x60-mm balloon catheter was placed coaxially in the stent. Via a left groin access, a 6-F vascular sheath was introduced retrograde, and a 2.5-cm Amplatz gooseneck snare was advanced into the infrarenal abdominal aorta and pulled back over the stent. The snare was tightly closed to crimp the stent onto the collapsed balloon; this maneuver was repeated several times until the stent was contracted along its entire length. The balloon/stent assembly was carefully pulled back into the right CIA, and the stent was deployed across the target lesion, although there was overlap of the left CIA. Color duplex sonography at 1 year showed no signs of significant iliac arterial stenoses on either side. The patient reported no claudication. CONCLUSIONS: Using a gooseneck snare, fully deployed balloon-expandable iliac stents can be recrimped on a balloon.

Frequency and significance of lumbar and inferior mesenteric artery perfusion after endovascular repair of abdominal aortic aneurysms.

PURPOSE: To evaluate the frequency and influence of perfused side branches (lumbar arteries [LA] and inferior mesenteric artery trunks) on development of type II endoleaks (EL-II) and on volume changes of abdominal aortic aneurysms (AAA) after endovascular repair. METHODS: Of 114 patients undergoing EVR of AAA, 89 patients (83 men; mean age 72+/-7.5 years, range 51-88) with >6 months' follow-up and no type I endoleaks were retrospectively analyzed to determine any relationships between retrograde perfusion, endoleaks, and sac volume. Data were derived from computed tomographic angiographic (CTA) scans taken before and after intervention, at discharge, and at 1, 3, 6, and semi-annually thereafter in follow-up. Two groups were identified and compared based on their status at 6 months post EVR: without perfused side branches (group 1) and with perfused collaterals (group 2); group 2 was further divided according to the absence (2a) or presence (2b) of endoleak. RESULTS: Median follow-up was 24 months (range 6-36). Based on a total of 582 CTAs analyzed, 17 (19%) patients developed type II endoleaks (EL-II) during follow-up. There was a significant difference in the number of perfused LAs prior to EVR between groups 1 (n=44) and the 45 patients with postprocedural patent collateral arteries in group 2 (p<0.05); there was no significant difference between groups 2a and 2b (p=0.88) relative to the number of pre-existing patent collaterals. The number of pLAs preoperatively and the rate of type II endoleak were significantly correlated (p<0.05). No type II endoleak was seen in patients without perfused side branches (p=0.01). No significant differences in mean volumes were found between groups 1 and 2a (no EL-II), but significant differences between groups 1 and 2b were seen in later follow-up. CONCLUSIONS: A larger number of patent LAs before EVR was associated with a significantly higher rate of type II endoleak. Patent collateral vessels were common after aneurysm repair, but the frequency decreased during follow-up. Persistent side branch perfusion was associated with increased type II endoleak after endovascular AAA repair. Significant differences in volume changes in later follow-up were seen between patients with or without type II endoleak.

Multislice spiral CT angiography in peripheral arterial occlusive disease: a valuable tool in detecting significant arterial lumen narrowing?

The aim of this study was to evaluate the potential of multislice CT angiography (CTA) in detecting hemodynamically significant (> or =70%) lesions of lower extremity inflow and runoff arteries. Fifty patients (42 men, 8 women; mean age 68 years) with peripheral arterial occlusive disease underwent multislice spiral CTA and digital subtraction angiography (DSA) from the infrarenal aorta to the supramalleolar region. CT parameters were 4x2.5-mm collimation, 15-mm table increment/rotation (pitch 6), and 1.25-mm reconstruction increment. Semitransparent volume rendering technique (STVR) images with semitransparent display of the arterial lumen (opacity: 50%) and vascular calcifications (opacity: 20%), as well as maximum intensity projection (MIP), and MIP together with axial CT studies were independently reviewed for hemodynamically significant lesions (> or =70% cross-sectional area reduction). DSA was the standard of reference. In 46 patients, 260 lesions were found (95 stenoses, 165 occlusions). For detecting > or =70% lesions in all vessel regions, sensitivity and specificity were 84% and 78% (STVR), 89% and 74% (MIP), and 92% and 83% (MIP+axial CT), respectively, with a significantly lower sensitivity of STVR ( p<0.05) and a significantly lower specificity of MIP studies ( p<0.01). Sensitivity and specificity were, respectively, 81% and 93% (STVR), 88% and 75% (MIP). and 92% and 95% (MIP+axial CT) at aortoiliac arteries, 92% and 73% (STVR), 95% and 70% (MIP) and 98% and 70% (MIP+axial CT) at femoropopliteal arteries, as well as 82% and 64% (STVR), 86% and 74% (MIP), and 90% and 74% (MIP+axial CT) at infrapopliteal arteries. Specificity of MIP-CTA was significantly lower in the aortoiliac region ( p<0.01), whereas STVR revealed significantly lower specificity at infrapopliteal arteries ( p<0.05). In the infrapopliteal region, the particular CTA imaging modalities led to misinterpretation regarding stenoses and occlusions in 39-45 cases, whereas only 0-6 significant aortoiliac and femoropopliteal lesions were misinterpreted. Multislice CTA is helpful in detecting hemodynamically significant lesions in peripheral arterial occlusive disease. Since axial CT studies yielded the most correct results, they should always be reviewed additionally. In the infrapopliteal region, exact lesion assessment remains problematic due to small vessel diameters.

Aortoiliac enhancement during computed tomography angiography with reduced contrast material dose and saline solution flush: influence on magnitude and uniformity of the contrast column.

RATIONALE AND OBJECTIVES: To compare the magnitude and uniformity of aortoiliac contrast enhancement obtained from uniphasic contrast material injections versus contrast material injections with reduced iodine dose followed by a saline flush in aortoiliac multislice CT angiography (CTA). METHODS: Twenty-nine patients with abdominal aortic aneurysms underwent aortoiliac CTA using protocols A and B. With protocol A, 120 mL contrast material (300 mgI/mL), and with protocol B, 100 mL contrast material followed by a 40-mL saline solution flush were administered at a flow rate of 4 mL/s. Quantitative analysis was performed by calculating mean aortoiliac attenuation, mean plateau deviation, and mean difference between maximum and minimum attenuation value for both groups. Qualitative analysis was performed by visual assessment of vascular enhancement using 2-dimensional and 3-dimensional postprocessing techniques. RESULTS: The mean aortoiliac attenuation with protocol A was 291 +/- 62 HU, and with protocol B it was 285 +/- 61 HU. The difference of 6 HU was not statistically significant (P = 0.27). Mean plateau deviation was significantly smaller using protocol A than protocol B (16 +/- 9 HU vs. 20 +/- 10 HU, P = 0.03). In addition, the mean difference between maximum and minimum attenuation value was significantly smaller with protocol A than with protocol B (59 +/- 29 HU vs. 72 +/- 32 HU, P = 0.01). Visual analysis showed no difference in contrast material magnitude and homogeneity between the protocols. CONCLUSIONS: In aortoiliac CTA, a saline solution flush after contrast material bolus allows an iodine dose reduction of approximately 20 mL without impairing the magnitude of contrast enhancement but degrades the uniformity of the contrast column. However, the degradation does not affect visual analysis.

Semitransparent volume-rendering CT angiography for lesion display in aortoiliac arteriosclerotic disease.

PURPOSE: The potential of semitransparent volume-rendering (STVR) computed tomographic (CT) angiography was evaluated for the assessment of hemodynamically significant stenoses in aortoiliac arteriosclerotic disease. MATERIALS AND METHODS: In a prospective study, 76 patients (57 men, 19 women; mean age, 70 years) underwent single-detector (n = 26) or multidetector (n = 50) CT angiography of the aortoiliac region. Intraarterial digital subtraction angiography (DSA) was performed in each patient. STVR images with semitransparent display of arterial lumen (opacity, 50%) and vascular calcifications (opacity, 20%), as well as maximum-intensity projection (MIP), frontal/sagittal curved planar reformation (CPR), and MIP/axial studies were independently reviewed for hemodynamically significant lesions (> or =70% cross-sectional area reduction). DSA combined with invasive pressure measurement was used as the standard of reference. Vessel wall calcifications were classified according to a four-point scale (0, not calcified; 1, mildly calcified; 2, moderately calcified; 3, severely calcified). RESULTS: Of the 380 reviewed vessel sections, 28 represented 70%-99% stenoses and 14 represented occlusions. For detecting >/==" BORDER="0">70% lesions, STVR as well as CPR and MIP/axial studies revealed significantly higher specificity (91%-94%), positive predictive value (PPV; 0.62-0.72), and accuracy (90%-94%) than MIP (specificity, 59%; PPV, 0.27; accuracy, 64%; P <.001) in moderately or severely calcified vessel sections. In noncalcified or mildly calcified sections, the specificity of MIP was comparable with the other rendering techniques (96%-98%; P values ranging from.34 to.77). No significant sensitivity differences were noticed among the CT angiography modalities: STVR, 79%; MIP, 88%; CPR, 83%; and MIP/axial, 93% (P values ranging from.12 to.78). Negative predictive values ranged from 0.97 to 0.99 (P values ranging from.14 to 1). Median calcification scores in sections with overestimated lumen narrowings were significantly higher (3, severely calcified) than in sections with correctly graded lumen width (1, mildly calcified) with all CT angiography modalities (P <.05). CONCLUSION: With use of STVR, visualization of vascular lumen can be improved by rendering highly transparent mural calcifications. Hence, for three-dimensional presentation of aortoiliac arteriosclerotic disease, STVR studies should be preferred to MIPs as supplements to review of axial-source images.