Jeffrey J. Horvath

Reproducibility of Dynamic Contrast-enhanced MR Imaging. Part I. Perfusion Characteristics in the Female Pelvis by Using Multiple Computer-aided Diagnosis Perfusion Analysis Solutions

PURPOSE To test the reproducibility of model-derived quantitative and semiquantitative pharmacokinetic parameters among various commercially available perfusion analysis solutions for dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging. MATERIALS AND METHODS The study was institutional review board approved and HIPAA compliant, with waiver of informed consent granted. The study group consisted of 15 patients (mean age, 44 years; range, 28-60 years), with 15 consecutive 1.5-T DCE MR imaging studies performed between October 1, 2010, and December 27, 2010, prior to uterine fibroid embolization. Studies were conducted by using variable-flip-angle T1 mapping and four-dimensional, time-resolved MR angiography with interleaved stochastic trajectories. Images from all DCE MR imaging studies were postprocessed with four commercially available perfusion analysis solutions by using a Tofts and Kermode model paradigm. Five observers measured pharmacokinetic parameters (volume transfer constant [K(trans)], v(e) [extracellular extravascular volume fraction], k(ep)[K(trans)/v(e)], and initial area under the gadolinium curve [iAUGC]) three times for each imaging study with each perfusion analysis solution (between March 13, 2011, and September 8, 2011) by using two different region-of-interest methods, resulting in 1800 data points. RESULTS After normalization of data output, significant differences in mean values were found for the majority of perfusion analysis solution combinations. The within-subject coefficient of variation among perfusion analysis solutions was 48.3%-68.8% for K(trans), 37.2%-60.3% for k(ep), 27.7%-74.1% for v(e), and 25.1%-61.2% for iAUGC. The intraclass correlation coefficient revealed only poor to moderate consistency among pairwise perfusion analysis solution comparisons (K(trans), 0.33-0.65; k(ep), 0.02-0.81; v(e), -0.03 to 0.72; and iAUGC, 0.47-0.78). CONCLUSION A considerable variability for DCE MR imaging pharmacokinetic parameters (K(trans), k(ep), v(e), iAUGC) was found among commercially available perfusion analysis solutions. Therefore, clinical comparability across perfusion analysis solutions is currently not warranted. Agreement on a postprocessing standard is paramount prior to establishing DCE MR imaging as a widely incorporated biomarker.

Reproducibility of Dynamic Contrast-enhanced MR Imaging. Part II. Comparison of Intra- and Interobserver Variability with Manual Region of Interest Placement versus Semiautomatic Lesion Segmentation and Histogram Analysis

PURPOSE To compare the inter- and intraobserver variability with manual region of interest (ROI) placement versus that with software-assisted semiautomatic lesion segmentation and histogram analysis with respect to quantitative dynamic contrast material-enhanced (DCE) MR imaging determinations of the volume transfer constant (K(trans)). MATERIALS AND METHODS The study was approved by the institutional review board and compliant with HIPAA. The requirement to obtain informed consent was waived. Fifteen DCE MR imaging studies of the female pelvis defined the study group. Uterine fibroids were used as a perfusion model. Three varying types of lesion measurements were performed by five readers on each study by using DCE MR imaging perfusion analysis software with manual ROI placement and a semiautomatic lesion segmentation and histogram analysis solution. Intra- and interreader variability of measurements of K(trans) with the different measurement types was calculated. RESULTS The overall interobserver variability of K(trans) with manual ROI placement (mean, 28.5% ± 9.3) was reduced by 42.5% when the semiautomatic, software-assisted lesion measurement method was used (16.4% ± 6.2). Whole-lesion measurement showed the lowest interobserver variability with both measurement methods (20.1% ± 4.3 with the manual method vs 10.8% ± 2.6 with the semiautomatic method). The overall intrareader variability with the manual ROI method (7.6% ± 10.6) was not significantly different from that with the semiautomatic method (7.3% ± 10.8), but the intraclass correlation coefficient for intrareader reproducibility improved from 0.86 overall with the manual method to 0.99 with the semiautomatic method. CONCLUSION A semiautomatic lesion segmentation and histogram analysis approach can provide a significant reduction in interobserver variability for DCE MR imaging measurements of K(trans) when compared with manual ROI methods, whereas intraobserver reproducibility is improved to some extent.

Correlation between quantitative whole-body muscle magnetic resonance imaging and clinical muscle weakness in pompe disease

Previous examination of whole‐body muscle involvement in Pompe disease has been limited to physical examination and/or qualitative magnetic resonance imaging (MRI). In this study we assess the feasibility of quantitative proton‐density fat‐fraction (PDFF) whole‐body MRI in late‐onset Pompe disease (LOPD) and compare the results with manual muscle testing.

Global Health Training in Radiology Residency Programs

RATIONALE AND OBJECTIVES To measure perceptions of radiology residents regarding the imaging needs of the developing world and the potential role of an organized global health imaging curriculum during residency training. MATERIALS AND METHODS An electronic survey was created and then distributed to residents in accredited US radiology residency. RESULTS Two hundred ninety-four residents responded to the survey. A majority (61%) planned to pursue future international medical aid work, even though a similar proportion (59%) believed that they would be ill-prepared with their current training to pursue this career goal. The vast majority (91%) of respondents stated that their residency program offers no opportunities to participate in global health imaging experiences. Most surveyed residents felt that an organized global health imaging curriculum would improve understanding of basic disease processes (87%) and cost-conscious care (82%), prepare residents for lifelong involvement in global health (80%), and increase interpretative skills in basic radiology modalities (73%). If such a curriculum were available, most (62%) of surveyed residents stated that they would be likely or very likely to participate. Many (58%) believed the availability of such a program would have influenced their choice of residency program; a similar proportion of residents (75%) believed that the availability of a global health imaging curriculum would increase recruitment to the field of radiology. CONCLUSION Many radiology residents are motivated to acquire global health imaging experience, with most survey respondents planning to participate in global health initiatives. These data demonstrate an imbalance between the level of resident interest and the availability of global health imaging opportunities, and support the need for discussion on how to implement global health imaging training within radiology residency programs.

Antigen delivery by α2-macroglobulin enhances the cytotoxic T lymphocyte response

α2M* targets antigens to APCs for rapid internalization, processing, and presentation. When used as an antigen‐delivery vehicle, α2M* amplifies MHC class II presentation, as demonstrated by increased antibody titers. Recent evidence, however, suggests that α2M* encapsulation may also enhance antigen‐specific CTL immunity. In this study, we demonstrate that α2M*‐delivered antigen (OVA) enhances the production of specific in vitro and in vivo CTL responses. Murine splenocytes expressing a transgenic TCR specific for CTL peptide OVA257–264 (SIINFEKL) demonstrated up to 25‐fold greater IFN‐γ and IL‐2 secretion when treated in vitro with α2M*‐OVA compared with soluble OVA. The frequency of IFN‐γ‐producing cells was increased ∼15‐fold, as measured by ELISPOT. Expansion of the OVA‐specific CD8+ T cell population, as assayed by tetramer binding and [3H]thymidine incorporation, and OVA‐specific cell‐mediated cytotoxicity, as determined by a flow cytometric assay, were also enhanced significantly by α2M*‐OVA. Furthermore, significant CTL responses were observed at antigen doses tenfold lower than those required with OVA alone. Finally, we also observed enhanced humoral and CTL responses by naïve mice following intradermal immunization with α2M*‐OVA. These α2M*‐OVA‐immunized mice demonstrated increased protection against a s.c.‐implanted, OVA‐expressing tumor, as demonstrated by delayed tumor growth and prolonged animal survival. The observation that α2M*‐mediated antigen delivery elicits specific CTL responses suggests the cross‐presentation of antigen onto MHC class I. These results support α2M* as an effective antigen‐delivery system that may be particularly useful for vaccines based on weakly immunogenic subunits or requiring dose sparing.

Tunneled Internal Jugular Hemodialysis Catheters: Impact of Laterality and Tip Position on Catheter Dysfunction and Infection Rates

PURPOSE To determine rates of dysfunction and infection for tunneled internal jugular vein hemodialysis catheters based on laterality of insertion and catheter tip position. MATERIALS AND METHODS Retrospective review of a procedural database for tunneled internal jugular vein hemodialysis catheter placements between January 2008 and December 2009 revealed 532 catheter insertions in 409 patients (234 male; mean age, 54.9 y). Of these, 398 catheters were placed on the right and 134 on the left. The catheter tip location was categorized as superior vena cava (SVC), pericavoatrial junction, or mid- to deep right atrium based on review of the final intraprocedural radiograph. The rates of catheter dysfunction and catheter-related infection (reported as events per 100 catheter-days) were analyzed. RESULTS Catheters terminating in the SVC or pericavoatrial junction inserted from the left showed significantly higher rates of infection (0.50 vs 0.27; P = .005) and dysfunction (0.25 vs 0.11; P = .036) compared with those inserted from the right. No difference was identified based on laterality for catheter tip position in the mid- to deep right atrium. Left-sided catheters terminating in the SVC or pericavoatrial junction had significantly more episodes of catheter dysfunction or infection than catheters terminating in the mid- to deep right atrium (0.84 vs 0.35; P = .006), whereas no significant difference was identified for right-sided catheters based on tip position. CONCLUSIONS When inserted from the left internal jugular vein, catheter tip position demonstrated a significant impact on catheter-related dysfunction and infection; this relationship was not demonstrated for right-sided catheters.

Comparison of Primary Jejunostomy Tubes versus Gastrojejunostomy Tubes for Percutaneous Enteral Nutrition

PURPOSE To evaluate technical success and long-term outcomes of percutaneous primary jejunostomy tubes for postpyloric enteral feeding compared with percutaneous gastrojejunostomy (GJ) tubes. MATERIALS AND METHODS Over a 25-month interval, 41 consecutive patients (26 male; mean age, 55.9 y) underwent attempted fluoroscopy-guided direct percutaneous jejunostomy tube insertion. Insertions at previous jejunostomy tube sites were excluded. The comparison group consisted of all primary GJ tube insertions performed over a 12-month interval concomitant with the jejunostomy tube interval (N = 169; 105 male; mean age, 59.4 y). Procedural, radiologic, and clinical data were retrospectively reviewed. Intervention rates were expressed as events per 100 catheter-days. RESULTS The technical success rate for percutaneous jejunostomy tube insertion was 96%, versus 93% for GJ tubes (P = .47). Mean fluoroscopy times were similar for jejunostomy and GJ tubes (9.8 vs 10.0 min, respectively; P value not significant). Jejunostomy tubes exhibited a lower rate of catheter dysfunction than GJ tubes, with catheter exchange rates of 0.24 versus 0.93, respectively, per 100 catheter-days (P = .045). GJ tube tip retraction into the stomach occurred in 9.5% of cases, at a rate of 0.21 per 100 catheter-days. Intervention rates related to leakage were 0.19 and 0.03 for jejunostomy and GJ tubes, respectively (P < .01). Jejunostomy and GJ tubes exhibited similar rates of catheter exchange for occlusion and replacement as a result of inadvertent removal. No major complications were encountered in either group. CONCLUSIONS Percutaneous insertion of primary jejunostomy tubes demonstrated technical success and complication rates similar to those of GJ tubes. Jejunostomy tubes exhibited a lower dysfunction rate but a higher leakage rate compared with GJ tubes.

Abdominopelvic and Lower Extremity Deep Venous Thrombosis: Evaluation With Contrast-Enhanced MR Venography With a Blood-Pool Agent

OBJECTIVE The purpose of this article is to evaluate contrast-enhanced (CE) MR venography (MRV) with a blood-pool agent for detection of abdominopelvic and lower extremity deep venous thrombosis (DVT) compared with a conventional unenhanced gradient-recalled echo (GRE) MRV technique. MATERIALS AND METHODS This retrospective study was performed on 30 patients (mean age, 52.7 years; 15 men and 15 women) referred for MRV between March 2010 and November 2010 for evaluation of lower extremity or abdominopelvic DVT. All patients underwent a GRE sequence followed by a CE T1-weighted sequence with gadofosveset, a blood-pool agent. The abdominopelvic and lower extremity venous system was divided into 13 segments. The presence of acute or chronic DVT was assessed by six radiologists, as well as qualitative and quantitative assessments of each venous segment. Image acquisition and interpretation times were also tabulated. RESULTS The sensitivity and specificity for acute DVT were 91.0% and 99.8%, respectively, on CE MRV compared with 80.8% and 95.8%, respectively, on GRE MRV (p = 0.077 and p < 0.001). The sensitivity and specificity for chronic DVT were 84.4% and 98.4%, respectively, on CE MRV and 64.5% and 95.6%, respectively, on GRE MRV (p < 0.001 for both). Subjective ratings of vein visualization, signal homogeneity, and confidence pertaining to DVT diagnosis were significantly higher with the CE images (p < 0.001). The contrast-to-noise ratio for CE images was similar or significantly higher for all venous segments. Image acquisition and radiologist interpretation times on the CE studies were decreased (p < 0.001). CONCLUSION Gadofosveset-enhanced MRV had equal or higher sensitivity and specificity for detection of DVT than did GRE MRV, with decreased time for image acquisition and interpretation.

Inter‐ and intra‐rater reproducibility of quantitative dynamic contrast enhanced MRI using TWIST perfusion data in a uterine fibroid model

To determine the reproducibility of TWIST‐derived (Time‐Resolved Angiography with Interleaved Stochastic Trajectories) quantitative dynamic contrast enhanced (DCE) MRI in a uterine fibroid model.

Covered Transjugular Intrahepatic Portosystemic Shunts: Accuracy of Ultrasound in Detecting Shunt Malfunction

OBJECTIVE The purpose of this study was to determine the accuracy of ultrasound for detecting transjugular intrahepatic portosystemic shunt (TIPS) malfunction in covered stents in comparison with bare metal stents. MATERIALS AND METHODS During a 6-year period, 126 TIPS angiography examinations were performed in 78 patients who had undergone a recent TIPS ultrasound examination. Radiology reports and images were retrospectively reviewed, and the sensitivity and specificity of sonographic parameters for detecting TIPS dysfunction were calculated using TIPS angiography and portosystemic gradient as the reference standards. RESULTS Of 126 paired studies, 43 were in bare metal TIPS and 83 were in covered TIPS. Peak shunt velocity of covered and bare metal TIPS measured by ultrasound showed comparable sensitivities for detection of shunt dysfunction, using both depressed (< 90 cm/s) and elevated (> 200 cm/s) peak shunt velocity criteria. However, a depressed velocity was more specific in covered TIPS (0.939 vs 0.550, p < 0.001) whereas elevated velocity was more specific in bare TIPS (0.485 vs 0.800, p = 0.041). An interval change in peak TIPS velocity greater than 25% was significantly more sensitive in detection of dysfunction in covered TIPS (0.815 vs 0.400, p = 0.015) whereas detection based on main portal vein velocities (≤ 30 cm/s) was not statistically different in the two groups. CONCLUSION Our data suggest that the accuracy of ultrasound for detection of TIPS shunt malfunction is at least as high in covered stents as in bare metal stents. Diagnostic performance for several sonographic parameters varied significantly between bare and covered stents, suggesting the need for optimization of sonographic criteria for covered stents.