Automatic irrigation system with a fiber-optic pressure sensor regulating intrapelvic pressure for flexible ureteroscopy.

Increased intrapelvic pressure (IPP) due to irrigation during flexible ureteroscopy (f-URS) can pose a risk of postoperative severe urinary tract infection associated with pyelovenous backflow. An automatic regulation system for maintaining safe IPP levels could enable surgeons to perform f-URS safely without postoperative complications. This study aimed to assess the measurement accuracy of an ultra-miniature fiber-optic pressure sensor incorporated into a small-caliper ureteroscope for assessing IPP and to develop an automatic irrigation system linked to this sensor. A porcine kidney was used for the ex vivo experiment. The nephrostomy catheter, connected to the conventional pressure transducer, was placed on the renal pelvis to evaluate the actual IPP (a-IPP). For measuring IPP using the fiber-optic pressure sensor (fo-IPP) built into the f-URS, a diaphragm pressure sensor of Φ250 µm was used. To establish an irrigation system, the optimal proportional-integral-derivative (PID) controller was explored to accurately adjust the irrigation pump flow rate. A high correlation between a-IPP and fo-IPP was confirmed across irrigation pressure values of 60-180 mbar (all, r ≥ 0.7, p < 0.001). When performing bolus irrigation, although fo-IPP showed relatively a higher peak value than a-IPP, the response time of fo-IPP was equivalent to that of a-IPP. After PID parameter optimization, our automatic irrigation system based on fo-IPP smoothly and accurately regulated the intended IPP set in the 5-20 mmHg range without overshooting. We successfully developed and demonstrated an automatic irrigation system regulating IPP based on the PID controller for f-URS, utilizing a fiber-optic pressure sensor. Further research, including in vivo studies, will be needed to assess clinical feasibility.

Development of modified laser Doppler flowmetry device for real-time monitoring of esophageal mucosal blood flow: a preclinical assessment with an animal model.

This study aimed to modify a laser Doppler flowmeter designed and assembled at our institute. After measuring sensitivity evaluation in ex vivo experiments, we confirmed the efficacy of this new device for monitoring real-time esophageal mucosal blood flow changes after thoracic stent graft implantation by simulating various clinical situations in an animal model. Thoracic stent graft implantation was performed in a swine model (n = 8). Esophageal mucosal blood flow decreased significantly from baseline (34.1 ± 18.8 ml/min/100 g vs. 16.7 ± 6.6 ml/min/100 g, P < 0.05) in the lower esophagus (Th6-Th8) where the stent graft covered the aorta. In the hemorrhagic shock model (shock index ≥ 1.0), esophageal mucosal blood flow showed a remarkable change from baseline in the upper esophagus (Th1-Th3), where the stent graft did not cover the aorta (20.8 ± 9.8 ml/min/100 g vs. 12.9 ± 8.6 ml/min/100 g, P < 0.01); however, it returned to the baseline value within a 30-min period. Mucosal blood flow remained stable in the esophagus, where the stent graft did not cover the aorta. After elevating the mean blood pressure to > 70 mmHg with continuous intravenous noradrenaline infusion, esophageal mucosal blood flow increased significantly in both regions; however, the reaction was different between the two regions. Our newly developed laser Doppler flowmeter could measure real-time esophageal mucosal blood flow changes in various clinical situations during thoracic stent graft implantation in a swine model. Hence, this device can be applied in many medical fields by downsizing it.

Design and kinematics of a tube-shaped multidirectional bending robotic device using slackened SMA wires for transurethral ureterolithotripsy.

PURPOSE: The complex and elaborate structure of the urinary system presents surgeons with difficulty in using a ureteroscope with a fixed optical fiber to reach the targeted calculus. To address this challenge, a robotic device is required to control the direction of laser irradiation position independently in ureteroscopes. METHOD: A continuum robotic device was designed and fabricated. The device is constructed with three slackened shape memory alloy (SMA) wires to control the laser irradiation position of the optical fiber combined with the view of the camera on the tip of the ureteroscope. Kinematics analysis and experimental evaluation reveal the capability of the device. RESULTS: The structure of the device is the same as a single-joint continuum robot. This device is unique because of the tiny diameter of 1.1 mm which can be used inside the ureteroscope through a Ø1.2 mm inner channel into the kidney for transurethral ureterolithotripsy. Kinematic analysis revealed the relationship among space coordinates, angles of bending, and direction and SMA wires length. The maximum bending angle was around 25° when the current value was 350 mA on a single SMA wire. The device could achieve multi-directional bending by allocating the values of current on SMA wires, separately. CONCLUSION: This device offers a major advancement in small size and dexterity in medical robotics. Combined with a proper control system, this device could simplify the operation and improve the efficiency of the transurethral ureterolithotripsy.

Treatment strategy for pediatric giant mucinous cystadenoma: A case report.

Because of their rarity, the treatment strategy for pediatric ovarian epithelial tumors is controversial, especially for a giant cystadenoma. We report the largest mucinous cystadenoma (MCA) case in the pediatric literature thus far. A 12-year-old girl had abdominal distention and visited our hospital. She had a multilocular cyst with some protuberance on the inside and high values of CA 19-9 and CA-125. We diagnosed her with a left MCA and performed a left oophorectomy. The tumor was the stage IA borderline malignant MCA and weighed 11.8 kg. Five years have passed, the patient has not experienced recurrence or metastasis. The resection of giant tumors can affect respiration and circulation. However, pre- or intra-operative drainage may lead to dissemination and adhesion. When we treat pediatric giant ovarian epithelial tumors, we must understand the findings that suggest the possibility of malignancy to decide appropriately as to whether drainage should be performed.

A new manometry device for evaluating the sphincter of Oddi using a fiber-optic pressure sensor.

INTRODUCTION: Although measuring the pressure of the sphincter of Oddi and the bile duct is considered to be an important examination, called Sphincter of Oddi manometry (SOM), some complications related to the SOM device remain unsolved. MATERIAL AND METHODS: To decrease adverse complications, we developed a 0.46 mm manometry and we performed some in vitro studies. RESULTS: We successfully developed a 0.46 mm SOM. The diameter is the thinnest size used in endoscopic examinations. The results of in vitro studies show the suitability as SOM. CONCLUSION: This device will decrease the risks related to SOM examination. To confirm the safety and feasibility, further studies including in vivo studies will be needed.

Oesophageal mucosal blood flow changes after thoracic endovascular stent graft implantation using a novel sensor probe.

OBJECTIVES: Secondary aorto-oesophageal fistula is a rare, lethal complication occurring after thoracic endovascular aneurysmal repair. The cause of secondary aorto-oesophageal fistula is unknown, but a reduction in local oesophageal mucosal blood flow (OMBF) may be a basis for such a devastating sequela. Our study aims to develop a novel blood flow sensor probe to detect changes in OMBF after thoracic stent graft implantation in an experimental swine model. METHODS: A novel laser Doppler flowmetry sensor probe incorporating an optical fibre sensor within a nasogastric tube was developed using microelectromechanical system technology. OMBF was measured at various levels using this sensor probe, to test its feasibility before and after thoracic endovascular stent graft implantation covering Th4-Th8 vertebral levels in 6 swine. RESULTS: In the middle oesophagus (Th5-Th7), where the aorta was covered with a stent graft, the measured OMBFs were significantly decreased after thoracic endovascular stent graft implantation than those of baseline (8.6 ± 2.7 vs 18.4 ± 7.9 ml/min/100 g, P < 0.0001), followed by a plateau period for at least 2 h after stent grafting (8.7 ± 3.3 ml/min/100 g, P < 0.0001 vs baseline). OMBFs in the upper (Th1-Th3) and lower (Th9-Th11) oesophagus, where the aorta was not covered with a stent graft, were unaffected by thoracic endovascular stent grafting. CONCLUSIONS: The novel laser Doppler flowmetry sensor probe was useful to monitor precise changes of OMBF in a swine model, demonstrating a significant reduction in OMBF after thoracic endovascular stent graft implantation.

Intraparenchymal ultrasound application and improved distribution of infusate with convection-enhanced delivery in rodent and nonhuman primate brain.

OBJECT Convection-enhanced delivery (CED) is an effective drug delivery method that delivers high concentrations of drugs directly into the targeted lesion beyond the blood-brain barrier. However, the drug distribution attained using CED has not satisfactorily covered the entire targeted lesion in tumors such as glioma. Recently, the efficacy of ultrasound assistance was reported for various drug delivery applications. The authors developed a new ultrasound-facilitated drug delivery (UFD) system that enables the application of ultrasound at the infusion site. The purpose of this study was to demonstrate the efficacy of the UFD system and to examine effective ultrasound profiles. METHODS The authors fabricated a steel bar-based device that generates ultrasound and enables infusion of the aqueous drug from one end of the bar. The volume of distribution (Vd) after infusion of 10 ml of 2% Evans blue dye (EBD) into rodent brain was tested with different frequencies and applied voltages: 252 kHz/30 V; 252 kHz/60 V; 524 kHz/13 V; 524 kHz/30 V; and 524 kHz/60 V. In addition, infusion of 5 mM gadopentetate dimeglumine (Gd-DTPA) was tested with 260 kHz/60 V, the distribution of which was evaluated using a 7-T MRI unit. In a nonhuman primate (Macaca fascicularis) study, 300 µl of 1 mM Gd-DTPA/EBD was infused. The final distribution was evaluated using MRI. Two-sample comparisons were made by Student t-test, and 1-way ANOVA was used for multiple comparisons. Significance was set at p < 0.05. RESULTS After infusion of 10 µl of EBD into the rat brain using the UFD system, the Vds of EBD in the UFD groups were significantly larger than those of the control group. When a frequency of 252 kHz was applied, the Vd of the group in which 60 V was applied was significantly larger than that of the group in which 30 V was used. When a frequency of 524 kHz was applied, the Vd tended to increase with application of a higher voltage; however, the differences were not significant (1-way ANOVA). The Vd of Gd-DTPA was also significantly larger in the UFD group than in the control group (p < 0.05, Student t-test). The volume of Gd-DTPA in the nonhuman primate used in this study was 1209.8 ± 193.6 mm(3). This volume was much larger than that achieved by conventional CED (568.6 ± 141.0 mm(3)). CONCLUSIONS The UFD system facilitated the distribution of EBD and Gd-DTPA more effectively than conventional CED. Lower frequency and higher applied voltage using resonance frequencies might be more effective to enlarge the Vd. The UFD system may provide a new treatment approach for CNS disorders.

Real-time monitoring of spinal cord blood flow with a novel sensor mounted on a cerebrospinal fluid drainage catheter in an animal model.

OBJECTIVE: The aim of our study was to develop a novel monitoring system for spinal cord blood flow (SCBF) to test the efficacy of the SCBF sensor in an animal model. METHODS: The sensor system consisted of 2 optical fibers, a pedestal for fiber fixation, and a mirror for the laser reflection and was incorporated into a cerebrospinal fluid drainage catheter. In vivo studies were performed in a swine model (n=10) to measure SCBF during spinal cord ischemia induced by clamping the descending thoracic aorta and supra-aortic neck vessels, when necessary. A temporary low cardiac output model was also created by inflow clamping of the inferior vena cava to analyze the quantitative changes in SCBF during this maneuver. RESULTS: The developed SCBF monitoring catheter placed intrathecally could detect SCBF in all the swine. The SCBF after aortic crossclamping at the fourth intercostal level exhibited diverse changes reproducibly among the swine, with a >25% reduction in SCBF in 5 pigs, an increase in 3, and no significant changes in 2. Consistent reductions were recorded during inferior vena cava occlusion. The mean SCBF decreased by 32% after inferior vena cava occlusion when the cardiac output had decreased by 27%. CONCLUSIONS: We have developed a novel SCBF sensor that could detect real-time changes in spinal cord perfusion in a swine model. The device holds promise to detect imminent ischemia or ensure acceptable blood perfusion in the spinal cord and could further enhance our understanding of spinal cord circulation.