A Large-Scale Proteomics Resource of Circulating Extracellular Vesicles for Biomarker Discovery in Pancreatic Cancer.

Pancreatic cancer has the worst prognosis of all common tumors. Earlier cancer diagnosis could increase survival rates and better assessment of metastatic disease could improve patient care. As such, there is an urgent need to develop biomarkers to diagnose this deadly malignancy earlier. Analyzing circulating extracellular vesicles (cEVs) using 'liquid biopsies' offers an attractive approach to diagnose and monitor disease status. However, it is important to differentiate EV-associated proteins enriched in patients with pancreatic ductal adenocarcinoma (PDAC) from those with benign pancreatic diseases such as chronic pancreatitis and intraductal papillary mucinous neoplasm (IPMN). To meet this need, we combined the novel EVtrap method for highly efficient isolation of EVs from plasma and conducted proteomics analysis of samples from 124 individuals, including patients with PDAC, benign pancreatic diseases and controls. On average, 912 EV proteins were identified per 100µL of plasma. EVs containing high levels of PDCD6IP, SERPINA12 and RUVBL2 were associated with PDAC compared to the benign diseases in both discovery and validation cohorts. EVs with PSMB4, RUVBL2 and ANKAR were associated with metastasis, and those with CRP, RALB and CD55 correlated with poor clinical prognosis. Finally, we validated a 7-EV protein PDAC signature against a background of benign pancreatic diseases that yielded an 89% prediction accuracy for the diagnosis of PDAC. To our knowledge, our study represents the largest proteomics profiling of circulating EVs ever conducted in pancreatic cancer and provides a valuable open-source atlas to the scientific community with a comprehensive catalogue of novel cEVs that may assist in the development of biomarkers and improve the outcomes of patients with PDAC.

Factors Affecting Adherence to Outpatient Radiology Report Recommendations.

PURPOSE: To identify factors associated with adherence to radiology follow-up recommendations by the referring physicians. MATERIALS AND METHODS: In this retrospective study, CT, ultrasound, and MRI reports with the keyword "recommend" and synonyms between March 11, 2019, and March 29, 2019, were included. Emergency department and inpatient examinations and routine surveillance recommendations, such as lung nodules, were excluded. Performance of follow-up examinations was correlated with the strength of recommendation, conditionality of recommendation, direct communication of results to ordering provider, and history of cancer. Outcomes included adherence to recommendations and time to follow-up. Statistical comparison between groups was performed using χ2, Kruskal-Wallis, and Spearman correlation. RESULTS: Qualifying recommendations were provided in 255 reports (age 60.1 ± 16.5 years, female: 151 of 255, 59.22%). Imaging follow-up was performed in 166 of 255 (65%) reports: 148 of 166 (89.15%) nonconditional versus 18 of 166 (10.48%) conditional recommendations (P = .008), and more frequently in the patients with a strong follow-up recommendation (138 of 166 [83.13%], versus 28 of 166 [16.86%]) (P = .009). The median time to follow-up was 28 days versus 82 days in patients without versus with a history of cancer (P = .00057), 28 days versus 70 days with direct communication with the provider versus without (P = .0069), 82.5 versus 21 days for reports in which a specific follow-up interval was provided (86 of 255, 33.72%) versus those without (169 of 255, 66.27%) (P < .001). CONCLUSION: The adherence rate for radiological nonroutine recommendations was 65%. Reports with strongly worded and nonconditional follow-up recommendations were followed more frequently. Direct communication with providers, patients without a known cancer history, and recommendations with no specified time interval identified were followed up earlier. CLINICAL RELEVANCE: Strongly worded and nonconditional follow-up recommendations increase the likelihood of follow-up being performed. Direct communication of imaging follow-up recommendations to the provider and lack of specific time intervals decreases the median time to follow-up, which in turn may decrease the delay in medical care.

Comparative Effectiveness of Magnetic Resonance Imaging-Ultrasound Fusion Versus In-bore Magnetic Resonance Imaging-targeted Prostate Biopsy.

OBJECTIVE: To examine the comparative effectiveness of magnetic resonance imaging-ultrasound (MRI-U/S) fusion biopsy and in-bore MRI-targeted biopsy. METHODS: We identified men aged 18-89 with a diagnosis of elevated prostate specific antigen (PSA) or Gleason 6 prostate cancer on active surveillance who underwent MRI-U/S fusion prostate biopsy (12-core + targeted) in the office or in-bore MRI-targeted biopsy (MRI-IB; targeted only). The cancer detection rate (CDR; Gleason 6-10) and clinically significant CDR (csCDR; Gleason 7-10) were compared across biopsy techniques, adjusted for patient and radiographic features. RESULTS: A total of 280 patients (346 lesions) were included, of whom 23.9% were on active surveillance for Gleason 6 prostate cancer. In the per-patient analyses, there was no statistically significant difference in adjusted overall CDR (64.1% vs 54.2%; P = .24) or csCDR (36.5% vs 37.9%; P = .85) between MRI-U/S and MRI-IB biopsy. In the per-lesion analyses, there was no statistically significant difference in adjusted overall CDR (45.7% vs 50.1%; P = .49) between MRI-U/S and MRI-IB biopsy, but MRI-IB biopsy was associated with a higher csCDR than MRI-U/S biopsy (32.8% vs 21.4%; P = .02). CONCLUSION: We observed no statistically significant differences in cancer detection rates between MRI-U/S fusion biopsy and MRI-IB biopsy in per-patient analyses. However, MRI-IB biopsy was associated with higher csCDR when considering targeted biopsy cores only. These results suggest that systematic cores should be obtained when performing MRI-U/S fusion biopsy.

Management of Patients With Common Bile Duct Dilatation Without a Sonographic Evident Cause: Evaluating the Yield of Subsequent Magnetic Resonance Imaging and Findings Correlated With Causative Pancreaticobiliary Pathology.

OBJECTIVES: The aims of the study were to evaluate the yield of magnetic resonance imaging (MRI) in patients with common bile duct (CBD) dilatation without a sonographic evident cause and to investigate sonographic and laboratory findings at presentation that might predict identification of underlying pancreaticobiliary pathology. METHODS: Included were consecutive patients in whom MRI was performed for further evaluation of CBD dilatation detected on ultrasound (US), without a sonographic evident cause, from January 1, 2014, to December 31, 2014. Magnetic resonance imaging and clinical data were retrospectively reviewed. Patients were divided into two groups: patients with and without identified underlying causative pancreaticobiliary pathology. Ultrasound findings and laboratory results at presentation were compared between groups to identify findings suggestive of underlying pancreaticobiliary pathology. RESULTS: Fifty-seven patients, with a mean age of 54 ± 16 years including 37 females (65%), underwent MRI. Specific pancreaticobiliary causes for CBD dilatation were identified in 38 patients (66%, 31 benign and 7 malignant). In the remaining patients, no cause was identified in 17 (30%) and MRIs were nondiagnostic in 2 patients. Magnetic resonance imaging accuracy for correctly identifying the underlying cause of CBD dilatation was 91%. Patients with associated intrahepatic bile duct dilatation on US and elevated alanine aminotransferase and alkaline phosphatase were more likely to have underlying pancreaticobiliary pathology (P < 0 .05). No patient with initial negative MRI had pancreaticobiliary malignancy. CONCLUSIONS: Magnetic resonance imaging seems to be an accurate noninvasive method for identifying the underlying cause in most patients with CBD dilatation on US and in excluding pancreaticobiliary malignancy. Patients with associated intrahepatic bile duct dilatation and/or elevated liver enzymes are at higher risk of harboring underlying pancreaticobiliary pathology.

Artificial intelligence to assess body composition on routine abdominal CT scans and predict mortality in pancreatic cancer- A recipe for your local application.

BACKGROUND: Body composition is associated with mortality; however its routine assessment is too time-consuming. PURPOSE: To demonstrate the value of artificial intelligence (AI) to extract body composition measures from routine studies, we aimed to develop a fully automated AI approach to measure fat and muscles masses, to validate its clinical discriminatory value, and to provide the code, training data and workflow solutions to facilitate its integration into local practice. METHODS: We developed a neural network that quantified the tissue components at the L3 vertebral body level using data from the Liver Tumor Challenge (LiTS) and a pancreatic cancer cohort. We classified sarcopenia using accepted skeletal muscle index cut-offs and visceral fat based its median value. We used Kaplan Meier curves and Cox regression analysis to assess the association between these measures and mortality. RESULTS: Applying the algorithm trained on LiTS data to the local cohort yielded good agreement [>0.8 intraclass correlation (ICC)]; when trained on both datasets, it had excellent agreement (>0.9 ICC). The pancreatic cancer cohort had 136 patients (mean age: 67 ± 11 years; 54% women); 15% had sarcopenia; mean visceral fat was 142 cm2. Concurrent with prior research, we found a significant association between sarcopenia and mortality [mean survival of 15 ± 12 vs. 22 ± 12 (p < 0.05), adjusted HR of 1.58 (95% CI: 1.03-3.33)] but no association between visceral fat and mortality. The detector analysis took 1 ± 0.5 s. CONCLUSIONS: AI body composition analysis can provide meaningful imaging biomarkers from routine exams demonstrating AI's ability to further enhance the clinical value of radiology reports.

The utility of magnetic resonance imaging for noninvasive evaluation of diabetic nephropathy.

BACKGROUND: Noninvasive quantitative measurement of fibrosis in chronic kidney disease (CKD) would be desirable diagnostically and therapeutically but standard radiologic imaging is too variable for clinical usage. By applying a vibratory force, tissue shear wave stiffness can be measured by magnetic resonance elastography (MRE) that may correlate with progression of kidney fibrosis. Since decreased kidney perfusion decreases tissue turgor and stiffness, we combined newly available three-dimensional MRE shear stiffness measurements with MR arterial spin labeling (ASL) kidney blood flow rates to evaluate fibrosis in diabetic nephropathy. METHODS: Thirty individuals with diabetes and Stage 0-5 CKD and 13 control individuals without CKD underwent noncontrast MRE with concurrent ASL blood flow measurements. RESULTS: MRE cortical shear stiffness at 90 Hz was decreased significantly below controls in all CKD stages of diabetic nephropathy. Likewise, ASL blood flow decreased progressively from 480 ± 136 mL/min/100 g of cortical tissue in controls to 302 ± 95, 229 ± 7 and 152 ± 32 mL/min/100 g in Stages 3, 4 and 5 CKD, respectively. A magnetic resonance imaging (MRI) surrogate for the measured glomerular filtration fraction [surrogate filtration fraction = estimated glomerular filtration rate (eGFR)/ASL] decreased progressively from 0.21 ± 0.07 in controls to 0.16 ± 0.04 in Stage 3 and 0.10 ± 0.02 in Stage 4-5 CKD. CONCLUSIONS: In this pilot study, MRI with ASL blood flow rates can noninvasively measure decreasing kidney cortical tissue perfusion and, with eGFR, a decreasing surrogate filtration fraction in worsening diabetic nephropathy that appears to correlate with increasing fibrosis. Differing from the liver, MRE shear stiffness surprisingly decreases with worsening CKD, likely related to decreased tissue turgor from lower blood flow rates.

Migrating to the Modern PACS: Challenges and Opportunities.

With progressive advancements in picture archiving and communication system (PACS) technology, radiology practices frequently look toward system upgrades and replacements to further improve efficiency and capabilities. The transition between PACS has the potential to derail the operations of a radiology department. Careful planning and attention to detail from radiology informatics leaders are imperative to ensure a smooth transition. This article is a review of the architecture of a modern PACS, highlighting areas of recent innovation. Key considerations for planning a PACS migration and important issues to consider in data migration, change management, and business continuity are discussed. Beyond the technical aspects of a PACS migration, the human factors to consider when managing the cultural change that accompanies a new informatics tool and the keys to success when managing technical failures are explored. Online supplemental material is available for this article. ©RSNA, 2018.

Magnetic resonance imaging performance for diagnosis of ovarian torsion in pregnant women with stimulated ovaries.

BACKGROUND: To determine if asymmetric ovarian edema on non-contrast MRI can be used to distinguish torsed from non-torsed stimulated ovaries in pregnant women. METHODS: In this retrospective study, our radiology database was searched for women who were pregnant and who had undergone ovarian stimulation and underwent MRI abdomen/pelvis from 1/2000-12/2012. At our institution, ultrasound is typically performed as a first line study for pregnant women with pelvic pain, with MR for those patients with indeterminate findings. 64 pregnant women (gestational age range 3-37 weeks) were included. MRI indication, prospective interpretation, operative diagnosis, and follow-up were recorded. Two blinded radiologists (with a third radiologist tie-breaker) independently measured and described the ovaries, including the likelihood of torsion. If one or both ovaries/adnexa had an underlying lesion such as a dermoid, cystadenoma, or abscess, the patient was excluded from size and signal intensity comparison (N = 14). For the remaining 50 women, comparison was made of the ovaries in women with normal ovaries (N = 27), stimulated ovaries without torsion (N = 11), non-stimulated ovaries with torsion (N = 3), and stimulated ovaries with torsion (N = 3). Patients with asymmetric ovarian edema without stimulation or torsion (N = 3) and with polycystic ovary syndrome (N = 3) were analyzed separately. RESULTS: Average normal ovarian length was 3.2 cm, compared to 4.5 cm for asymmetric edema and 5.6-8.8 cm for the other four groups. Average difference in greatest right and left ovarian diameter was 19% for normal ovaries compared to 24-37% for the other 5 groups. Asymmetric signal on T2-weighted imaging (T2WI) was seen in 12% (3/27) of normal ovaries compared to 9% (1/11) of stimulated patients without torsion, 33% (1/3) of patients with PCOS and 67% (2/3) of patients with torsion both without and with stimulation. The correct diagnosis of torsion was made prospectively in 5/6 cases but retrospectively in only 3/6 cases. In patients with stimulation, correct diagnosis of torsion was made in 2/3 cases prospectively (both with asymmetric T2 signal) and retrospectively in only 1/3 cases. In 13/64 patients, other acute gynecologic and non-gynecologic findings were diagnosed on MRI. CONCLUSIONS: Enlarged edematous ovary can be seen with ovarian stimulation, ovarian torsion, or both. Although asymmetric ovarian edema occurred more frequently in patients with torsion than without, in pregnant patients with stimulated ovaries referred for MRI (typically after non-diagnostic ultrasound), ovarian torsion could not be confidently diagnosed or excluded retrospectively with non-contrast MRI.

MRI guided needle localization in a patient with recurrence pleomorphic sarcoma and post-operative scarring.

MRI-guided wire localization is commonly used for surgical localization of breast lesions. Here we introduce an alternative use of this technique to help with surgical resection of a recurrent pleomorphic sarcoma embedded in extensive post-treatment scar tissue. We describe a case of recurrent pleomorphic soft tissue sarcoma in the thigh after treatment with neoadjuvant therapy, surgery, and radiation. Due to the distortion of the normal tissue architecture and formation of extensive scar tissue from prior treatment, wire localization under MRI was successfully used to assist the surgeon in identifying the recurrent tumor for removal.

High throughput tools to access images from clinical archives for research.

Historically, medical images collected in the course of clinical care have been difficult to access for secondary research studies. While there is a tremendous potential value in the large volume of studies contained in clinical image archives, Picture Archiving and Communication Systems (PACS) are designed to optimize clinical operations and workflow. Search capabilities in PACS are basic, limiting their use for population studies, and duplication of archives for research is costly. To address this need, we augment the Informatics for Integrating Biology and the Bedside (i2b2) open source software, providing investigators with the tools necessary to query and integrate medical record and clinical research data. Over 100 healthcare institutions have installed this suite of software tools that allows investigators to search medical record metadata including images for specific types of patients. In this report, we describe a new Medical Imaging Informatics Bench to Bedside (mi2b2) module ( www.mi2b2.org ), available now as an open source addition to the i2b2 software platform that allows medical imaging examinations collected during routine clinical care to be made available to translational investigators directly from their institution's clinical PACS for research and educational use in compliance with the Health Insurance Portability and Accountability Act (HIPAA) Omnibus Rule. Access governance within the mi2b2 module is customizable per institution and PACS minimizing impact on clinical systems. Currently in active use at our institutions, this new technology has already been used to facilitate access to thousands of clinical MRI brain studies representing specific patient phenotypes for use in research.

Tumor necrosis on magnetic resonance imaging correlates with aggressive histology and disease progression in clear cell renal cell carcinoma.

OBJECTIVE: The study objective was to correlate the magnetic resonance imaging (MRI) features of clear cell renal cell carcinoma (ccRCC) with the histopathologic features and disease progression. METHODS: Institutional review board approval for this retrospective study was obtained; patient consent was not required. The initial staging MRI scans of 75 patients with histologically confirmed ccRCC were retrospectively reviewed. The imaging was assessed by 2 radiologists for the presence of tumor necrosis, cystic degeneration, intracellular fat, hemorrhage, retroperitoneal collaterals, and renal vein thrombosis. Quantitative analysis for the MRI presence of intracellular lipid within tumors was performed. MRI findings were correlated with histopathologic findings of clear cell percentage, alveolar and tubular growth pattern, and disease progression. Statistical associations were evaluated with nonparametric univariable analyses and multivariable logistic regression models. RESULTS: Correlation between MRI and histopathologic features was performed in 75 patients, whereas follow-up data were available for progression analysis in 68 patients. The presence of tumor necrosis, retroperitoneal collaterals, and renal vein thrombosis on MRI was significantly associated with a low percentage of tumor cells with clear cytoplasm (P < .01) and metastatic disease at presentation or disease progression (P < .01). At multivariable analysis, necrosis remained the only feature statistically associated with disease progression (P = .03; adjusted odds ratio, 27.7; 95% confidence interval, 1.4-554.7 for reader 1 and P = .02; adjusted odds ratio, 29.3; 95% confidence interval, 1.7-520.8 for reader 2). CONCLUSIONS: Necrosis in ccRCC on MRI correlates with the histopathologic finding of lower percentage of tumor cells with clear cytoplasm and is a poor prognostic indicator irrespective of tumor size.

Angiomyolipoma with minimal fat: can it be differentiated from clear cell renal cell carcinoma by using standard MR techniques?

PURPOSE: To retrospectively assess whether magnetic resonance (MR) imaging with opposed-phase and in-phase gradient-echo (GRE) sequences and MR feature analysis can differentiate angiomyolipomas (AMLs) that contain minimal fat from clear cell renal cell carcinomas (RCCs), with particular emphasis on small (<3-cm) masses. MATERIALS AND METHODS: Institutional review board approval and a waiver of informed consent were obtained for this HIPAA-compliant study. MR images from 108 pathologically proved renal masses (88 clear cell RCCs and 20 minimal fat AMLs from 64 men and 44 women) at two academic institutions were evaluated. The signal intensity (SI) of each renal mass and spleen on opposed-phase and in-phase GRE images was used to calculate an SI index and tumor-to-spleen SI ratio. Two radiologists who were blinded to the pathologic results independently assessed the subjective presence of intravoxel fat (ie, decreased SI on opposed-phase images compared with that on in-phase images), SI on T1-weighted and T2-weighted images, cystic degeneration, necrosis, hemorrhage, retroperitoneal collaterals, and renal vein thrombosis. Results were analyzed by using the Wilcoxon rank sum test, two-tailed Fisher exact test, and multivariate logistic regression analysis for all renal masses and for small masses. A P value of less than .05 was considered to indicate a statistically significant difference. RESULTS: There were no differences between minimal fat AMLs and clear cell RCCs for the SI index (8.05%±14.46 vs 14.99%±19.9; P=.146) or tumor-to-spleen ratio (-8.96%±16.6 and -15.8%±22.4; P=.227) when all masses or small masses were analyzed. Diagnostic accuracy (area under receiver operating characteristic curve) for the SI index and tumor-to-spleen ratio was 0.59. Intratumoral necrosis and larger size were predictive of clear cell RCC (P<.001) for all lesions, whereas low SI (relative to renal parenchyma SI) on T2-weighted images, smaller size, and female sex correlated with minimal fat AML (P<.001) for all lesions. CONCLUSION: The diagnostic accuracy of opposed-phase and in-phase GRE MR imaging for the differentiation of minimal fat AML and clear cell RCC is poor. In this cohort, low SI on T2-weighted images relative to renal parenchyma and small size suggested minimal fat AML, whereas intratumoral necrosis and large size argued against this diagnosis.

High-resolution proton density weighted three-dimensional fast spin echo (3D-FSE) of the knee with IDEAL at 1.5 Tesla: comparison with 3D-FSE and 2D-FSE--initial experience.

PURPOSE: To assess the feasibility of combining three-dimensional fast spin echo (3D-FSE) and Iterative-decomposition-of water-and-fat-with-echo asymmetry-and-least-squares-estimation (IDEAL) at 1.5 Tesla (T), generating a high-resolution 3D isotropic proton density-weighted image set with and without "fat-suppression" (FS) in a single acquisition, and to compare with 2D-FSE and 3D-FSE (without IDEAL). MATERIALS AND METHODS: Ten asymptomatic volunteers prospectively underwent sagittal 3D-FSE-IDEAL, 3D-FSE, and 2D-FSE sequences at 1.5T (slice thickness [ST]: 0.8 mm, 0.8 mm, and 3.5 mm, respectively). 3D-FSE and 2D-FSE were repeated with frequency-selective FS. Fluid, cartilage, and muscle signal-to-noise ratio (SNR) and fluid-cartilage contrast-to-noise ratio (CNR) were compared among sequences. Three blinded reviewers independently scored quality of menisci/cartilage depiction for all sequences. "Fat-suppression" was qualitatively scored and compared among sequences. RESULTS: 3D-FSE-IDEAL fluid-cartilage CNR was higher than in 2D-FSE (P < 0.05), not different from 3D-FSE (P = 0.31). There was no significant difference in fluid SNR among sequences. 2D-FSE cartilage SNR was higher than in 3D FSE-IDEAL (P < 0.05), not different to 3D-FSE (P = 0.059). 2D-FSE muscle SNR was higher than in 3D-FSE-IDEAL (P < 0.05) and 3D-FSE (P < 0.05). Good or excellent depiction of menisci/cartilage was achieved using 3D-FSE-IDEAL in the acquired sagittal and reformatted planes. Excellent, homogeneous "fat-suppression" was achieved using 3D-FSE-IDEAL, superior to FS-3D-FSE and FS-2D-FSE (P < 0.05). CONCLUSION: 3D FSE-IDEAL is a feasible approach to acquire multiplanar images of diagnostic quality, both with and without homogeneous "fat-suppression" from a single acquisition.

Dynamic half-Fourier single-shot turbo spin echo for assessment of deep venous thrombosis: initial observations.

OBJECTIVE: The objective of this study was to retrospectively analyze the value of dynamic half-Fourier single-shot turbo spin echo (HASTE) imaging in patients with suspected deep venous thrombosis (DVT). MATERIALS AND METHODS: Fifty-five veins in 24 patients were interrogated using a HASTE sequence with the patients relaxed and in various degrees of Valsalva. Veins were analyzed for changes in caliber (+CAL) and signal intensity (+SI) or in their absence (-CAL and -SI, respectively) and compared with the presence of thrombus on gadolinium-enhanced magnetic resonance imaging. RESULTS: There was no thrombus in veins with the +CAL, +SI pattern (n=40) (P<.01). Five of seven veins (71.4%) with the -CAL, -SI pattern had thrombus (P<.01). A qualitative change in CAL had a sensitivity of 100% and a specificity of 91% for the presence of thrombus. An increase of 1.5 mm in CAL had a sensitivity of 100% and a specificity of 93% for this diagnosis. CONCLUSION: Dynamic HASTE imaging offers a physiological method to evaluate veins for deep venous thrombosis.

Use of personal digital assistants in diagnostic radiology resident education.

RATIONALE AND OBJECTIVES: Personal digital assistants (PDAs) are gaining widespread use in the medical community. We introduced a PDA-based mobile system that provides departmental and educational information with a seamless connection to the intranet. The objective of this study is to determine the impact a PDA has on educational resources (learning or data reference) brought to work and used at home by a radiology resident based on user surveys. MATERIALS AND METHODS: Survey was performed on 32 radiology residents in our department before and 6 months after the release of the PDA-based system. We assessed the changes in (1) sources of learning at home and at work, and in (2) data reference. The second survey also evaluated the usefulness of each component of the system. RESULTS: After the release of the PDA-based mobile system, the use of "digital books and references" as data references and educational resources that were brought to work every day significantly increased (P = .016, P < .0001, respectively). "Traditional books and references" remained the "most useful source in learning radiology"; however, "digital books and references" increased as the residents' first choice from 0% to 16% within 6 months of introducing the package (P = .125). CONCLUSION: The introduction of a PDA-based system consisting of educational and departmental information had a statistically significant impact in increasing the use of digitized information in radiology resident education.

A mobile solution: PDA-based platform for radiology information management.

OBJECTIVE: We describe how our radiology department set up, integrated, and deployed a personal digital assistant-based mobile platform to deliver updated critical departmental and educational material to our residents. CONCLUSION: We have implemented and described a robust mobile solution that maintains a seamless connection with the departmental intranet. Resident feedback regarding the use of the mobile solution program has confirmed our belief that using this mobile technology is a feasible and clinically practical alternative for accessing time-sensitive and educational materials. Furthermore, our description can help others deploy such digital products and facilitate the transition to soft copy that is already occurring in radiology education.

Static material properties of the tectorial membrane: a summary.

The tectorial membrane (TM) is a polyelectrolyte gel. Hence, its chemical, electrical, mechanical, and osmotic properties are inextricably linked. We review, integrate, and interpret recent findings on these properties in isolated TM preparations. The dimensions of the TM in alligator lizard, chick, and mouse are sensitive to bath ion concentrations of constituents normally present in the cochlear fluids - an increase in calcium concentration shrinks the TM, and an increase in sodium concentration swells the TM in a manner that depends competitively on the calcium concentration. The sodium-induced swelling is specific; it does not occur with other alkali metal cations. We interpret these findings as due to competitive binding of sodium and calcium to TM macromolecules which causes a change in their conformation that leads to a change in mechanical properties. In mouse TM, decreasing the bath pH below 6 or increasing it above 7 results in swelling of the TM. Electric potential measurements are consistent with the notion that the swelling is caused by a pH-driven increase in positive fixed charge at low pH and an increase in the magnitude of the negative fixed charge at high pH which is consistent with the known protonation pattern of TM macromolecules. Increasing the osmotic pressure of the bathing solution with polyethylene glycol shrinks the TM and decreasing the ionic strength of the bathing solution swells the TM. Both results are qualitatively consistent with predictions of a polyelectrolyte gel model of the TM.