Faculty Bibliography

Advances in surgical techniques, orthopaedic implant design, and higher demands for improved functionality of the aging population have resulted in a high prevalence of patients with metallic implants about the knee. Total knee arthroplasty, knee-replacing tumor prostheses, and osteosynthesis implants create various imaging artifacts and pose special challenges for the imaging evaluation with computed tomography (CT) and magnetic resonance imaging (MRI). CT artifacts can be effectively mitigated with metal artifact reduction reconstruction algorithms, dual-energy data acquisition with virtual monoenergetic extrapolation, and three-dimensional postprocessing techniques, such as volume and cinematic rendering. Artifacts related to metal implants on MRI can be reduced via optimization of the scan parameters and using advanced techniques such as multi-acquisition variable-resonance image combination, and slice encoding for metal artifact correction.

While the imaging modality of choice to diagnose neurosarcoidosis is gadolinium-enhanced MRI, F-FDG PET/CT maybe used to stage the disease or target the optimal biopsy site. Few cases have described intense F-FDG uptake at the sites of active neurosarcoidosis in the midbrain and pituitary gland, cerebellar hemispheres, and temporal lobes. Here, we present a case of neurosarcoidosis whose PET/CT examination demonstrated F-FDG avidity in a dural plaque.

We present two cases of umbilical hernia incarceration following large volume paracentesis (LVP) in patients with cirrhotic ascites. Both patients became symptomatic within 48 hours after the LVP. Although being rare, given the significantly higher mortality rate of cirrhotic patients undergoing emergent herniorrhaphy, this complication of LVP is potentially serious. Therefore, it is recommended that patients be examined closely for the presence of umbilical hernias before removal of ascitic fluid and an attempt should be made for external reduction of easily reducible hernias, if a hernia is present.

OBJECT/OBJECTIVE:This study aims to validate phase-contrast magnetic resonance imaging (PC-MRI) measurements of a steady flow through a severe stenotic phantom using particle image velocimetry (PIV) and computational fluid dynamics (CFD). MATERIALS AND METHODS/METHODS:The study was performed in an axisymmetric 87 % area stenosis model using an inlet Reynolds number (Re) of 160, corresponding to a jet Re of 444. Velocity patterns and estimated fluid shear stresses from three modalities were analyzed and compared qualitatively and quantitatively. RESULTS:Visual analysis via contour subtraction and Bland-Altman plots showed good agreement for flow velocities and less agreement for maximum shear stress (MSS). The Pearson's coefficients of correlation between PC-MRI and PIV were 0.97 for the velocity field and 0.82 for the MSS. The corresponding parameters between PC-MRI and CFD were 0.96 and 0.84, respectively. CONCLUSION/CONCLUSIONS:Findings indicate that PC-MRI can be implemented to estimate velocity flow fields and MSS; however, this method is not sufficiently accurate to quantify the MSS at regions of high shear rate.

PURPOSE/OBJECTIVE:To validate conventional phase-contrast MRI (PC-MRI) measurements of steady and pulsatile flows through stenotic phantoms with various degrees of narrowing at Reynolds numbers mimicking flows in the human iliac artery using stereoscopic particle image velocimetry (SPIV) as gold standard. MATERIALS AND METHODS/METHODS:A series of detailed experiments are reported for validation of MR measurements of steady and pulsatile flows with SPIV and CFD on three different stenotic models with 50%, 74%, and 87% area occlusions at three sites: two diameters proximal to the stenosis, at the throat, and two diameters distal to the stenosis. RESULTS:Agreement between conventional spin-warp PC-MRI with Cartesian read-out and SPIV was demonstrated for both steady and pulsatile flows with mean Reynolds numbers of 130, 160, and 190 at the inlet by evaluating the linear regression between the two methods. The analysis revealed a correlation coefficient of > 0.99 and > 0.96 for steady and pulsatile flows, respectively. Additionally, it was found that the most accurate measures of flow by the sequence were at the throat of the stenosis (error < 5% for both steady and pulsatile mean flows). The flow rate error distal to the stenosis was primarily found to be a function of narrowing severity including dependence on proper Venc selection. CONCLUSION/CONCLUSIONS:SPIV and CFD provide excellent approaches to in vitro validation of new or existing PC-MRI flow measurement techniques.

We present a case of an acquired, transient, rotated right kidney in a 43-year-old woman with an enterocutaneous fistula who presented with acute pulmonary embolism. This non-ptotic rotated kidney returned to its normal orientation within 10 days. We postulate that this transient kidney rotation is due to transient hepatomegaly and passive renal congestion secondary to pulmonary embolism. While in this patient there were no untoward sequelae, it has been reported that ureteral obstruction or vascular occlusion can occur in patients with ptotic and malrotated kidneys, and radiologists, therefore, should be aware of this unusual occurrence and the potential complications.

The viability and a number of morphological properties of in situ astrocytes of rat spinal cord cultures including changes in surface area and migration of both cell body and nucleus were investigated at magnetic field intensities comparable to those currently used for magnetic resonance imaging. Viability of rat spinal astrocytes was studied after up to 72 hours of 2.1T static magnetic field exposure. Surface areas and two-dimensional centroids of both soma and nucleus after 2 hours of magnetic field exposure were determined and compared with those of the same cells before magnetic field exposure. Cell membrane ruffling was quantified using fractal analysis. Viability of astrocytes remained unchanged at 4, 16, 24, 48 and 72 hours. The mean soma area before and after 2 hours of field exposure was 6450 microm(2) and 6299 microm(2), respectively, whereas the values for nuclear area were 185.6 microm(2) and 185.7 microm(2). The mean displacement of the centroid of soma parallel and perpendicular to the magnetic field direction was 1.07 microm and 0.78 microm, respectively. The corresponding quantities for nuclei were 0.29 microm and -2.00 microm. None of these changes were statistically significant. No membrane protrusion was observed by fractal analysis. In conclusion, strong static magnetic field at 2.1 T does not significantly affect the viability and morphological properties of rat astrocytes.