Jan Patrick Opherk

Characterization and staging of central bile duct stenosis—Evaluation of the hepatocyte specific contrast agent gadoxetate disodium

OBJECTIVE To assess the value of gadoxetate disodium for characterization and staging of central bile duct stenosis (CBDS). MATERIALS AND METHODS This prospective HIPAA-compliant study was IRB approved. 14 patients (8 male, 6 female; 36-80 years) with clinical suspicion of CBDS underwent preoperative MRI. To estimate the value of hepatocyte phase images (10, 20, 120 min p.i.), only T2w images (T2), only post-contrast images (CM), or both image datasets were assessed in three reading sessions by 3 readers. Agreement of each reading session with the intraoperative findings in terms of CBDS etiology and tumor extension (weighted kappa statistic) was calculated. RESULTS CBDS was caused by hilar cholangiocarcinoma (n=9), gallbladder carcinoma (n=4) and pancreatic carcinoma (n=1). Characterization of CBDS etiology was correct by use of: T2w images in 57%, 64%, 50%; CM images in 64%, 57%, 50%; both in 71%, 64%, 64%. Agreement comparing reading sessions and intraoperative findings regarding tumor extension was fair up to moderate (κ-range=0.21-0.54) as a result of common underestimation. Interobserver agreement for tumor extension was fair (κ-range=0.31-0.33). CONCLUSIONS By means of combined evaluation of T2 and CM images a more reliable characterization of CBDS was possible. Even though CBDS tended to be underestimated assessment of exact tumor extension was improved by contrast administration.

Physical stress testing of bovine jugular veins using magnetic resonance imaging, echocardiography and electrical velocimetry.

Bovine jugular veins (BJVs) (Contegra) are valve-bearing pulmonary artery substitutes. Their valves have higher profiles than human pulmonary valves; this might result in less optimal performance. Therefore, we investigated the impact of stress and undersizing on conduit performance with ergometry, echocardiography and magnetic resonance imaging (MRI). Between April 2007 and June 2008, 20 BJV recipients (age 7.9-19.6 years) underwent spiroergometry and subsequent echocardiography; after due rest, ergometry was repeated and followed by MRI during recovery. A year later, exams were repeated. Data was evaluated as follows: comparison of stress related maximal individual valve performance changes (magnetic resonance: exercise induced average stroke volume changes by 61+/-49%; mean insufficiency increased by 2% in patients with <1% rest insufficiency and by 8% after rest insufficiency of >10%; the average rest gradient of 24+/-11 mmHg rose to 40+/-20 mmHg), and stratification of pooled observations by regurgitation fraction, insufficiency grades and z-values (insufficiency rose with increasing heart rate and decreasing stroke volume; undersizing increased gradients during recovery by 7+/-0.7 mmHg/z-value). Contegras high-profile valves tolerate stress without performance drop. Stress induced changes of insufficiency and gradient were clinically not significant, but sufficient to distort examination results; therefore, constant examination conditions are indispensable for a correct follow-up.