Faculty Bibliography

Purpose: TIPS creation fails to control ascites in 40% or more of patients, but the variables predicting outcome are unclear, with prior studies highlighting pre-TIPS portosystemic gradient (PSG) (Nair et al 2004; JVIR 15:1431). We studied which variables predict outcome of TIPS for refractory ascites. Materials and Methods: We retrospectively identified patients who underwent TIPS for refractory ascites between 1/12 and 5/14, yielding 40 patients. We excluded 17 patients due to insufficient peri-procedural documentation or technical failures, leaving 23 patients (16 men, 7 women, mean age 60 +/-2 yrs) for assessment of variables influencing osmotic (albumin and sodium levels) and hydrostatic (pre- and post- TIPS PSG and large varices) pressure. Responders were defined as those requiring fewer or no paracenteses; nonresponders had persistent ascites, with similar pre-TIPS frequency of therapeutic paracentesis. Complications within 1 month requiring hospitalization were noted. Multiple logistic regression, Mann-Whitney U tests, and one-tailed chi² tests assessed group differences. Results: Ten patients (43%: responders) had documented improvement in ascites. Multiple logistic regression including pre- and post-TIPS PSG significantly impacted outcome (p=0.04). Post- but not pre-TIPS PSG predicted outcome (p=0.04 vs. p=0.84). Responders had significantly lower post- TIPS gradient (5.8) compared with non-responders (7.6) (p=0.02). In contrast, responders and non-responders did not differ in albumin (2.7 vs. 2.7) or sodium (136 vs. 134) levels, or pre-TIPS gradient (13.9 vs. 14.7 mmHg) (p>0.05). Similar numbers of responders (50%) had large varices compared to non-responders (61%) (p=0.3). Responders (50%) had significantly more complications compared to non-responders (15%) (p=0.04), mostly encephalopathy (85%) requiring hospitalization. Conclusion: Only post-TIPS PSG predicted which patients had significantly reduced ascites, in contrast to prior studies suggesting importance of pre-TIPS gradient. Findings suggest aggressively lowering the gradient below 6 mmHg may be the most reliable technique to improve outcomes, although with expected higher risk of complications

Purpose: To evaluate if there is a significant difference in retrieval difficulty as determined by fluoroscopy time and equipment use when comparing three different filters: Denali, ALN, and Option/Option Elite. Materials and Methods: Retrospective analysis was performed of 33 filter retrievals performed over a 24 month period (12 men, 21 women; mean age 60). There were 8 Denali (Bard Peripheral Vascular), 9 ALN (ALN Implants), and 16 Option/ Option Elite (Argon Medical Devices) filter retrievals. Demographics, filter dwell time, fluoroscopy time during retrieval, and equipment used for retrieval were collected for each case. One Option case was excluded due to unsuccessful retrieval. Kruskal-Wallis H, two sample t-test and Chi-square analysis were used to determine significant differences in fluoroscopy time and equipment use between the three filter groups. Results: There were no significant differences between groups based on demographics or filter dwell time. Mean retrieval times were 4.9 min (SD: 3.6, range 1.2-10.3) for Denali, 9.9 min (SD: 5.5, range 2.9-18.6) for ALN, and 23.9 min (SD: 20.0, range 2.5 - 58) for Option/Option Elite. A Kruskal-Wallis H test showed a significant difference in these times (chi²=7.17, p=0.028), subsequent post-hoc analysis showed a significant difference only between Denali and Option but not between Denali and ALN or ALN and Option. Given normal distribution of fluoroscopy times for Denali and ALN, a separate t-test comparing these two filters did demonstrate a significant difference in fluoroscopy time (p=0.023). None of the Denali retrievals required additional equipment beyond a snare and sheath, 1/9 (11%) of ALN and 10/15 (67%) of Option retrievals required at least a tip deflecting wire or angled catheter (chi²=11.07, p=0.004). Sub-analysis separating Option and Option Elite filters did not change any results significantly. Conclusion: Denali filter retrieval involves significantly less fluoroscopy time than ALN or Option/Option Elite filter retrieval. In this series, Option/Option Elite retrieval also required significantly more equipment to achieve technical success compared to Denali and ALN retrieval. A larger sample size is required to corroborate these early results. (Table Presented)

Purpose: To review radiation dose exposure for patients undergoing IVC filter placement in order to infer quantitative guidelines for expected doses. To identify strategies for targeted dose reduction. Materials and Methods: Records of 230 consecutive cases of IVC filter placement in Interventional Radiology at a single university hospital between 1/4/12 and 6/7/13 were reviewed. Patients under age 18 and patients with variant anatomy (e.g. duplicated IVC) or caval thrombosis were excluded. Radiation dose (mGy) was recorded from the fluoroscopic detector system; access site and patient information were noted. Subset analyses were performed, including analysis before and after exclusion of outliers (more than two SD from the mean) and before and after exclusion of cases without contrast (no DSA). Patients were stratified by access site, BMI, age, and gender; correlation with dose was analyzed using Spearman rank correlation and Mann-Whitney tests. Four access site categories were used: Right internal jugular (RIJ), left internal jugular (LIJ), right common femoral (RCF), and Other. Results: Mean radiation dose in all subjects was 67.55 mGy, and after outliers and non-contrast cases were excluded, 51.35 mGy.Radiation dose was highest in cases when IVC filters were placed via the RIJ compared with LIJ, RCF, and other access sites. Radiation dose was significantly lower in cases with filters placed via RCF than in those with filters placed via RIJ (p=0.018). Conclusion: Analysis of radiation dose in a standardized procedure-IVC filter placement-provides valuable information on expected dose range and potential dose reduction strategies. Access via RIJ (vs. RCF) resulted in significantly higher dose, raising the question: should a standard access site for IVC filter placement be considered? Additionally, this model will be implemented to identify dose reduction strategies for other standard interventional procedures. (Table Presented)

The goals of this study were to derive a frequency-position function for the human cochlear spiral ganglion (SG) to correlate represented frequency along the organ of Corti (OC) to location along the SG, to determine the range of individual variability, and to calculate an "average" frequency map (based on the trajectories of the dendrites of the SG cells). For both OC and SG frequency maps, a potentially important limitation is that accurate estimates of cochlear place frequency based upon the Greenwood function require knowledge of the total OC or SG length, which cannot be determined in most temporal bone and imaging studies. Therefore, an additional goal of this study was to evaluate a simple metric, basal coil diameter that might be utilized to estimate OC and SG length. Cadaver cochleae (n = 9) were fixed <24 h postmortem, stained with osmium tetroxide, microdissected, decalcified briefly, embedded in epoxy resin, and examined in surface preparations. In digital images, the OC and SG were measured, and the radial nerve fiber trajectories were traced to define a series of frequency-matched coordinates along the two structures. Images of the cochlear turns were reconstructed and measurements of basal turn diameter were made and correlated with OC and SG measurements. The data obtained provide a mathematical function for relating represented frequency along the OC to that of the SG. Results showed that whereas the distance along the OC that corresponds to a critical bandwidth is assumed to be constant throughout the cochlea, estimated critical band distance in the SG varies significantly along the spiral. Additional findings suggest that measurements of basal coil diameter in preoperative images may allow prediction of OC/SG length and estimation of the insertion depth required to reach specific angles of rotation and frequencies. Results also indicate that OC and SG percentage length expressed as a function of rotation angle from the round window is fairly constant across subjects. The implications of these findings for the design and surgical insertion of cochlear implants are discussed.

Greenwood's frequency-position function for the organ of Corti (OC) is commonly used to estimate represented frequencies for cochlear implant (CI) electrodes, both in temporal bone studies and in imaging studies of living CI recipients. However, many contemporary CIs position stimulating electrodes near the modiolus, directly targeting the spiral ganglion (SG) cells within Rosenthal's canal. At the extreme base and apex, the SG does not extend as far as the OC, and the radial nerve fibers take a tangential course into the modiolus resulting in a potential offset between the frequency maps of the OC and SG. In this investigation, human cadaveric cochleae (n = 7) were studied in surface preparations after osmium staining. The OC and SG lengths were measured and radial fiber trajectories traced to identify frequency-matched points on each structure. These data allowed derivation of a mathematical function correlating represented frequency along the OC to position along the SG. A cubic function fit the data with a very high intersubject correlation. Better knowledge of the human SG 'neural frequency map' may help to refine electrode design, and to more accurately map CI channel filter bands to the appropriate cochlear place along the SG, which may be advantageous for more sophisticated CI outcomes, such as music appreciation. These data also could be valuable for electroacoustic stimulation, by defining the insertion distance of a CI electrode required to reach specific frequencies (based upon preoperative imaging) in an individual subject, thus helping to avoid trauma to cochlear regions with residual hearing.