Determining the Safety Threshold for the Passage of a Ureteral Access Sheath in Clinical Practice Using a Purpose-Built Force Sensor.

PURPOSE: Ureteral injury is a frequent complication of ureteral access sheath deployment. We sought to define the safe threshold of force for the passage of a ureteral access sheath using a novel ureteral access sheath force sensor. MATERIALS AND METHODS: Ureteral access sheath-force sensor measurements were recorded in 210 renal units. A 16Fr ureteral access sheath was deployed initially based on a prior porcine study. If 6 N was reached, the surgeon was advised to downsize the 16Fr ureteral access sheath. In each case, a post-ureteroscopic lesion scale was recorded. Regression models were used to estimate the impact of adjusted variables on post-ureteroscopic lesion scale grade, 16Fr ureteral access sheath deployment, and peak force. RESULTS: A 16Fr ureteral access sheath was deployed in 127 (61%) renal units with a mean peak force of 5.7 N. Two high-grade ureteral injuries occurred; in both cases >6 N of force was recorded. Post-ureteroscopic lesion scale grade correlated directly with peak insertion force (p <0.01). Bacteriuria within 60 days of the procedure (OR 2.009, p=0.034), combination of preoperative stent plus oral tamsulosin (OR 2.998, p=0.045), and prior ipsilateral stone surgery (OR 2.13, p=0.01) were independent predictors of successful 16Fr ureteral access sheath deployment. Among patients with neither prior ipsilateral stone surgery nor preoperative stent, preoperative tamsulosin facilitated passage of a 16Fr ureteral access sheath (OR 2.750, p=0.034). CONCLUSIONS: Ureteral access sheath associated ureteral injury can be averted by limiting the insertion force to ≤6 N. Prior stone surgery, preoperative indwelling ureteral stent plus oral tamsulosin, and recently treated bacteriuria favored passage of a 16Fr ureteral access sheath. In the naïve, unstented patient, preoperative tamsulosin favored deployment of a 16Fr ureteral access sheath.

Ureteral Access Sheath Deployment: How Much Force Is Too Much? Initial Studies with a Novel Ureteral Access Sheath Force Sensor in the Porcine Ureter.

Introduction and Objectives: Ureteral injuries can occur during ureteral access sheath (UAS) deployment. The force exerted during deployment and the amount of force that results in ureteral injury is yet to be accurately quantitated. In this feasibility study, we developed and then tested a novel force-sensing device in our animal laboratory to identify the threshold force that results in a porcine ureteral injury. Methods: With Institutional Animal Care and Use Committee approval, we measured ureteral dilator and UAS deployment force using our proprietary University of California, Irvine Ureteral Access Sheath Force Sensor (UAS-FS). The exerted force was measured during deployment from the moment that the tip of the UAS was passed into the urethral meatus until it reached the renal pelvis; progression of the UAS along the ureter was monitored with fluoroscopy. Ureteroscopic evaluation was performed after deployment of each catheter/sheath ≥8F to assess for ureteral injury using the Postureteroscopic Lesion Scale (PULS). Results: Six juvenile Yorkshire female pigs (12 ureters) were studied. No injuries were detected when the deployment force was <4 Newtons (N), which was the case when the catheter/access sheath was ≤13F. Increasing UAS size >13F resulted in greater peak forces. In five of the pigs, ureters selected for 14F UAS deployment without previous sequential dilation were injured (PULS ≥3) at a mean threshold force of 4.84 N. Serial dilation had a higher threshold for PULS ≥3 at 5.56 N. Overall, injury of PULS ≥3 was routinely noted when the force applied exceeded 8.1 N. Conclusions: The UAS-FS reliably measured forces while deploying a UAS. Significant ureteral injury can routinely be avoided if the applied force is <4.84 N; PULS ≥3 routinely occurred when forces exceeded 8.1 N. Serial dilation may allow safe passage at higher deployment forces, as much as 5.56 N.

Topical oxygen therapy & micro/nanobubbles: a new modality for tissue oxygen delivery.

Up to 15 billion dollars of US health care expenditure each year is consumed by treatment of poorly healing wounds whose etiologies are often associated with aberrancies in tissue oxygenation. To address this issue, several modes of tissue oxygen delivery systems exist, including Hyperbaric Oxygen Therapy (HBOT) and Topical Oxygen Therapy (TOT), but their efficacies have yet to be fully substantiated. Micro/nanobubbles (MNBs), which range anywhere from 100 µm to <1 µm in diameter and are relatively stable for hours, offer a new mode of oxygen delivery to wounds. The aim of this article is to systematically review literature examining the use of TOT for wound healing and use of MNBs for tissue oxygenation using the MEDLINE database. The search yielded 87 articles (12 MNB articles and 75 TOT articles), of which 52 met the inclusion criteria for this literature review (12 MNB articles and 40 TOT articles). Additionally, we present an analysis on the efficacy of our MNB generating technology and propose its use as a wound healing agent.

Breast tissue characterization with photon-counting spectral CT imaging: a postmortem breast study.

PURPOSE: To investigate the feasibility of breast tissue characterization in terms of water, lipid, and protein contents with a spectral computed tomographic (CT) system based on a cadmium zinc telluride (CZT) photon-counting detector by using postmortem breasts. MATERIALS AND METHODS: Nineteen pairs of postmortem breasts were imaged with a CZT-based photon-counting spectral CT system with beam energy of 100 kVp. The mean glandular dose was estimated to be in the range of 1.8-2.2 mGy. The images were corrected for pulse pile-up and other artifacts by using spectral distortion corrections. Dual-energy decomposition was then applied to characterize each breast into water, lipid, and protein contents. The precision of the three-compartment characterization was evaluated by comparing the composition of right and left breasts, where the standard error of the estimations was determined. The results of dual-energy decomposition were compared by using averaged root mean square to chemical analysis, which was used as the reference standard. RESULTS: The standard errors of the estimations of the right-left correlations obtained from spectral CT were 7.4%, 6.7%, and 3.2% for water, lipid, and protein contents, respectively. Compared with the reference standard, the average root mean square error in breast tissue composition was 2.8%. CONCLUSION: Spectral CT can be used to accurately quantify the water, lipid, and protein contents in breast tissue in a laboratory study by using postmortem specimens.

Volumetric lean percentage measurement using dual energy mammography.

PURPOSE: Currently, there is no accepted standard for measuring breast density. Dual energy mammography, which has demonstrated accurate measurement in phantoms, has been proposed as one possible method. To examine the use of chemical analysis as a possible means to validate breast density measurements from dual energy mammography, a bovine tissue model was investigated. Known quantities of lean and adipose tissue were compared with composition values measured from dual energy images and chemical analysis. METHODS: Theoretical simulations were performed to assess the impact variations in breast composition would have on measurement of breast density from a single calibration. Fourteen ex-vivo tissue samples composed of varying amounts of pure lean tissue and pure adipose tissue (lean percentage) from 0 to 100%, in increments of 10%, were imaged using dual energy mammography. This was followed by chemical analysis based on desiccation, trituration, and fat extraction with petroleum ether to determine water, lipid, and protein content. The volumetric lean percentage (VLP) as measured from images (VLP(I)) and as derived from chemical analysis data (VLP(CA)) were compared with the VLP calculated from measurements of sample mass with a scale (VLP(M)). Finally, data from the bovine tissue model in this study were compared to compositional data from a previous report of human tissue composition. RESULTS: The results from simulation suggest a substantial impact on measuring breast density is likely due to changes in anatomical breast composition. VLP(I) was related to the VLP(M) by VLP(I) = 1.53 VLP(M) + 10.0 (r2 > 0.99). VLP(CA) was related to VLP(M) by VLP(CA) = 0.76 VLP(M) + 22.8 (r2 > 0.99). VLP(I) was related to VLP(CA) by VLP(I) = 2.00 VLP(CA) - 35.6 (r2 > 0.99). Bovine adipose tissue was shown to be very similar to human adipose tissue in terms of water, lipid, and protein content with RMS differences of 1.2%. Bovine lean tissue was shown to be very similar to human skeletal muscle tissue and somewhat similar to human mammary gland tissue with RMS differences of 0.4 and 22.2%, respectively. CONCLUSIONS: The results of this study show strong linear relationships between volumetric lean percentage measurements using dual energy mammography, chemical analysis and the actual mass. Determining the existence of a relationship between VLP(I) and VLP(CA) was necessary before comparing density results from the dual energy technique to composition data from chemical analysis for samples of unknown composition.