Imaging Predictors of Elevated Lung Shunt Fraction in Patients Being Considered for Yttrium-90 Radioembolization.

PURPOSE: To identify imaging findings associated with elevated lung shunt fraction (LSF) in patients being considered for yttrium-90 ((90)Y) radioembolization. MATERIALS AND METHODS: During the period 2009-2014, 152 consecutive patients underwent planning hepatic arteriography with technetium-99m ((99m)Tc) macroaggregated albumin (MAA) injection. Computed tomography (CT) or magnetic resonance imaging performed before the procedure for each patient was assessed for hepatic vein (HV) tumor thrombus or occlusion from external compression by tumor. When imaging was a multiphase CT scan (117 patients), the arterial phase was evaluated for evidence of early HV opacification (relative to unaffected HVs), indicating hepatic venous shunting. These factors were correlated with LSF determined by (99m)Tc-MAA imaging. RESULTS: Median LSF was 6.7% (range, < 0.1%-71%), significantly higher for HCC (8.0% vs 6.3% for other tumors, P = .048). Larger tumor size was associated with higher LSF in univariate analysis (P = .001). There was high interobserver agreement for determining hepatic venous shunting (97%, κ = 0.847), which was associated with higher LSF (P < .001; 78% sensitivity, 93% specificity). Of 5 cases of HV tumor thrombus, all had high (> 20%) LSF (P < .001). HV occlusion was also associated with higher LSF (P = .039). Multivariate analysis confirmed that early HV opacification and either HV tumor thrombus or occlusion were associated with higher LSF. CONCLUSIONS: Early HV opacification and HV tumor thrombus or occlusion on cross-sectional imaging performed before radioembolization are associated with elevated LSF, which may contraindicate or limit the dose delivered in (90)Y radioembolization. This information could be helpful during patient counseling for anticipating the most appropriate mode of liver-directed therapy.

Caval penetration by retrievable inferior vena cava filters: a retrospective comparison of Option and Günther Tulip filters.

PURPOSE: To compare the frequency of vena caval penetration by the struts of the Option and Günther Tulip cone filters on postplacement computed tomography (CT) imaging. MATERIALS AND METHODS: All patients who had an Option or Günther Tulip inferior vena cava (IVC) filter placed between January 2010 and May 2012 were identified retrospectively from medical records. Of the 208 IVC filters placed, the positions of 58 devices (21 Option filters, 37 Günther Tulip filters [GTFs]) were documented on follow-up CT examinations obtained for reasons unrelated to filter placement. In cases when multiple CT studies were obtained after placement, each study was reviewed, for a total of 80 examinations. Images were assessed for evidence of caval wall penetration by filter components, noting the number of penetrating struts and any effect on pericaval tissues. RESULTS: Penetration of at least one strut was observed in 17% of all filters imaged by CT between 1 and 447 days following placement. Although there was no significant difference in the overall prevalence of penetration when comparing the Option filter and GTF (Option, 10%; GTF, 22%), only GTFs showed time-dependent penetration, with penetration becoming more likely after prolonged indwelling times. No patient had damage to pericaval tissues or documented symptoms attributed to penetration. CONCLUSIONS: Although the Günther Tulip and Option filters exhibit caval penetration at CT imaging, only the GTF exhibits progressive penetration over time.

Imaging assessment of a portable hemodialysis device: detection of possible failure modes and monitoring of functional performance.

BACKGROUND: The purpose of this study was to investigate the utility and limitations of various imaging modalities in the noninvasive assessment of a novel compact hemodialyzer under development for renal replacement therapy, with specific aim towards monitoring its functional performance. METHODS: The prototype is a 4×3×6 cm aluminum cartridge housing "blood" and "dialysate" flow paths arranged in parallel. A sheet of semipermeable silicon nanopore membranes forms the blood-dialysate interface, allowing passage of small molecules. Blood flow was simulated using a peristaltic pump to instill iodinated contrast through the blood compartment, while de-ionized water was instilled through the dialysate compartment at a matched rate in the countercurrent direction. Images were acquired under these flow conditions using multi-detector computed tomography (MDCT), fluoroscopy, high-resolution quantitative computed tomography (HR-QCT), and magnetic resonance imaging (MRI). MDCT was used to monitor contrast diffusion efficiency by plotting contrast density as a function of position along the path of flow through the cartridge during steady state infusion at 1 and 20 mL/min. Both linear and exponential regressions were used to model contrast decay along the flow path. RESULTS: Both linear and exponential models of contrast decay appeared to be reasonable approximations, yielding similar results for contrast diffusion during a single pass through the cartridge. There was no measurable difference in contrast diffusion when comparing 1 mL/min and 20 mL/min flow rates. Fluoroscopy allowed a gross qualitative assessment of flow within the device, and revealed flow inhomogeneity within the corner of the cartridge opposite the blood inlet port. MRI and HR-QCT were both severely limited due to the paramagnetic properties and high atomic number of the target material, respectively. During testing, we encountered several causes of device malfunction, including leak formation, trapped gas, and contrast-mediated nanopore clogging. We illustrate the imaging manifestations of each. CONCLUSIONS: Despite the inherent challenges in imaging a predominantly metallic device, some modalities show potential in the non-invasive assessment of a novel compact hemodialyzer. The approaches described here could potentially be translated to device evaluation in the implanted setting.