Actuator-driven Pulsed Water Jet Research Articles

Piezo Actuator-Driven Pulsed Water Jet for Neurosurgery: Laboratory Evaluation with the Swine Model and Implications of Mechanical Properties.

Object Pulsed water jet is an emerging surgical instrumentation intended to achieve both maximal lesion resection and functional maintenance through preservation of fine vessels and minimal damage to the surrounding tissue. The piezo actuator-driven pulsed water jet (ADPJ) is a new technology that can deliver a precisely controlled uniform and efficient pulsed water jet with minimum water flow. The present study evaluated the ADPJ system in preclinical animal studies in the swine brain, and investigated breaking strength, one of the parameters for mechanical properties, to elucidate the mechanism of tissue selectivity for tissue dissection by the water jet. Methods This system consisted of a pump chamber driven by a piezo actuator, a stainless steel tube, and a nozzle (internal diameter: 0.15 mm). The water was supplied at 6 ml/min. The relationship between input voltage (3-25 V at 400 Hz) and peak pressure was measured using a pressure sensor through a sensing hole. Temporal profile of dissection depth during moving application was evaluated using gelatin brain phantom and swine brain. The dissected specimens were evaluated histologically. The mechanical property (breaking strength) of swine brain was measured by a compact table-top universal tester. Results Peak pressure increased linearly with increase in the input voltage, which reflected dissection depth in both the gelatin brain phantom and swine brain. Small arteries were preserved, and minimum damage to surrounding tissues occurred. The breaking strength of arachnoid membrane (0.12 ± 0.014 MPa) was significantly higher compared to gray matter (0.030 ± 0.010 MPa) and white matter (0.056 ± 0.009 MPa) (p < 0.05). The breaking strength of gray matter corresponded to that of 3 wt% gelatin, and that of white matter corresponded to a value between those of 3.5 and 4 wt% gelatin, and the dissection depth seemed to be estimated by 3-4 wt% gelatin. Conclusion The present study suggests that the ADPJ system has the potential to achieve accurate tissue dissection with preservation of blood vessels in neurosurgery. The difference in breaking strength may explain the tissue selectivity between brain parenchyma and tissue protected by the arachnoid membrane.

Effectiveness of an actuator-driven pulsed water jet for removal of softened carious dentin.

The aim of this study was to assess the utility of an actuator-driven pulsed water jet (ADPJ) as a hardness-dependent carious dentin removal device by using different outputs. Thirty-six plane surface dental caries samples were treated with the ADPJ at 150, 200, and 250 voltage (12 teeth each). The Knoop hardness number (KHN) and Ca/P mass ratio were measured at 70 μm from the deepest point of the removing groove. Furthermore, three other teeth samples were manually treated with the ADPJ at the three above mentioned voltages (one tooth each) for 1 min. The KHN and Ca/P mass ratio were measured at 70 μm from the surface of the residual dentin part. In both the KHN and Ca/P mass ratio, higher residual dentin depended on the applied voltage of ADPJ. The ADPJ enabled the removal of softened carious dentin in an applied voltage-dependent manner.

The effectiveness of an actuator-driven pulsed water jet for the removal of artificial dental calculus: a preliminary study

BackgroundWhile hand and ultrasonic scalers are the primary tools used for the removal of dental calculus in periodontal treatment, many studies have shown that they also damage the enamel surface. We have developed a novel actuator-driven pulsed water jet (ADPJ) system, which has the ability to selectively remove materials depending on their stiffness. Considering the different material properties between teeth and dental calculus, it might be possible to develop the ADPJ to remove dental calculus without damage to the tooth’s enamel surface using a suitable jet pressure. Therefore, the aim of this study was to assess the effectiveness of the ADPJ in removing dental calculus, and the surface features of the teeth after its use.MethodsA total of 93 artificial teeth coated with artificial dental calculus were examined in this study. The weights of 90 teeth were measured before and after the use of ADPJ, which had an applied voltage setting of 150, 200, or 240 V. The three remaining teeth were instrumented with a conventional hand scaler, ultrasonic scaler, or ADPJ (set at 240 V). Damage to the artificial tooth surfaces was evaluated using 5% Evans blue dye under an optical microscope. Furthermore, apatite pellets, which are utilized as experimental substitutes for natural teeth, were assessed after the use of ADPJ and both conventional scalers.ResultsThe ADPJ significantly reduced the amount of artificial calculus, and the removal rate was dependent on the applied voltage. No damage was observed on the surface of the artificial tooth and apatite pellet following the use of ADPJ, in contrast to the conventional scalers.ConclusionsThe results of this study demonstrate the in vitro effectiveness of ADPJ in the removal of dental calculus, without causing damage to tooth surfaces.

Anatomic Indications for Using Actuator-driven Pulsed Water Jet for Hepatectomy.

The clamp crushing method and the use of the Cavitron ultrasonic surgical aspirator (CUSA) are widely accepted techniques for hepatic parenchymal transection. The actuator-driven pulsed water jet (ADPJ) with high tissue selectivity is a new technology that was shown as a safe transection tool in preclinical models, although not much is known about its safety criteria in patients. Therefore, its strongest advantage, the best indications for its use, and its performance in comparison with other transection methods remain to be clarified. In this report, we present several representative cases to help answer these questions. We started using the ADPJ in December 2017, only in cases where the tumor was very close to major vessels or attached to them, along a considerable length, to preserve vessels and prevent postoperative liver failure. All the cases underwent highly demanding procedures. We avoided using this device in cases such as liver cirrhosis, where the hepatic parenchyma was very hard. Six cases fulfilled our limited indications for using ADPJ. The median age and number of tumors were 55 years (10 to 69 y) and 2.5 years (1 to 4 y), respectively. The mean tumor size was 7.8 cm (2.8 to 21 cm), the minimum distance between the tumor and major vessels to be preserved was 0 mm (0 to 4 mm), and the contact length of the tumor and major vessels was 26 mm (19 to 40 mm). Regarding the surgical outcome, the median operation time and blood loss were 559 minutes (508 to 919 min) and 620 mL (230 to 860 mL), respectively. We achieved a negative surgical margin (R0 resection) in all cases. Using ADPJ, we could perform R0 hepatectomy in all cases, which preoperatively were considered to have a high chance of being margin positive. We consider the best indication for using ADPJ is when the tumor and vessels to be preserved are attached or very close over a long distance.

Effects of a Novel Piezo Actuator-driven Pulsed Water Jet System on Residual Kidney After Partial Nephrectomy in a Rat Model

To evaluate renal damage after off-clamp partial nephrectomy (PN) using a novel surgical device, piezo actuator-driven pulsed water jet (ADPJ) system. Sprague-Dawley rats were divided into 4 groups and subjected to sham operation, off-clamp PN by the piezo ADPJ system, radio knife, and soft coagulation, which have been used as thermal coagulation devices. Urine and blood samples were collected, and residual kidneys were harvested at 1, 7, 14, 30, and 90 days after PN. Serum blood urea nitrogen, creatinine, and urinary and serum kidney injury molecule-1 KIM-1 levels were measured. Morphological features and the extent of renal ischemia of resection surfaces were evaluated by hematoxylin-eosin staining and immunostaining using antibodies to 1-methyladenosine, respectively. In addition, the expression levels of KIM-1 mRNA extracted from each resection surface were analyzed by quantitative real-time reverse transcription polymerase chain reaction. Serum blood urea nitrogen and creatinine were significantly lower with the piezo ADPJ system than with soft coagulation. Urinary and serum KIM-1 levels were also significantly decreased with the ADPJ. The extent of 1-methyladenosine immunostaining was significantly less with the ADPJ than with thermal coagulation devices. The expression levels of KIM-1 mRNA were also lower in the ADPJ system group. The piezo ADPJ system might attenuate renal damage after off-clamp PN.

Water Veil Effect to Control Splashing from the Pulsed Water Jet Device: Minimizing the Potential Risk of Dissemination Using Surgical Aspirators.

Maximum resection with minimum damage to normal structures is required for a better clinical outcome. Several efficient surgical devices such as the Cavitron ultrasonic surgical aspirator are available. Our group developed the actuator-driven pulsed water jet (ADPJ) to dissect soft tissue with vessel preservation. Although these devices are very effective for resection, tumor seeding is a potential risk. The present study investigated the control of splashing during ADPJ use. We demonstrate the effect of additional water flow around the instrument tip to veil the splashing. Pulsed water jet was ejected from the tip of the ADPJ nozzle. Effects of ADPJ parameters such as input voltage, suction pressure, and distance between the nozzle and the target (standoff distance) on the amount of splashing were analyzed. Methylene blue solution was ejected on photo paper, gelatin brain phantom, and porcine brain harvested and subsequently immersed into physiologic saline to quantify the amount of splashing. High-input voltage and a long standoff distance had significant correlations with large amounts of splashing (r > 0.5; p < 0.01). However, suction pressure had no correlation (r = 0.23). Additional water flow combined with the ADPJ decreased the amount of splashing. A high-speed camera recording revealed that the additional water flow formed a water veil that prevented droplet dispersion, as confirmed with experiments using the brain phantom and porcine brain, in which the irregularity and elasticity are specific. The veil effect of additional water flow is important to reduce splashing during ADPJ use and can minimize the potential risk of dissemination and enhance the safety of the ADPJ.

Actuator-driven pulsed water jet surgery system: Clinical experience.

Actuator-driven pulsed water jet surgery system: Clinical experience.

The Piezo Actuator-Driven Pulsed Water Jet System for Minimizing Renal Damage after Off-Clamp Laparoscopic Partial Nephrectomy.

In the setting of partial nephrectomy (PN) for renal cell carcinoma, postoperative renal dysfunction might be caused by surgical procedure. The aim of this study was to clarify the technical safety and renal damage after off-clamp laparoscopic PN (LPN) with a piezo actuator-driven pulsed water jet (ADPJ) system. Eight swine underwent off-clamp LPN with this surgical device, while off-clamp open PN was also performed with radio knife or soft coagulation. The length of the removed kidney was 40 mm, and the renal parenchyma was dissected until the renal calyx became clearly visible. The degree of renal degeneration from the resection surface was compared by Hematoxylin-Eosin staining and immunostaining for 1-methyladenosine, a sensitive marker for the ischemic tissue damage. The mRNA levels of neutrophil gelatinase-associated lipocalin (Ngal), a biomarker for acute kidney injury, were measured by quantitative real-time PCR. Off-clamp LPN with ADPJ system was successfully performed while preserving fine blood vessels and the renal calix with little bleeding. In contrast to other devices, the resection surface obtained with the ADPJ system showed only marginal degree of ischemic changes. Indeed, the expression level of Ngal mRNA was lower in the resection surface obtained with the ADPJ system than that with soft coagulation (p = 0.02). Furthermore, using the excised specimens of renal cell carcinoma, we measured the breaking strength at each site of the human kidney, suggesting the applicability of this ADPJ to clinical trials. In conclusion, off-clamp LPN with the ADPJ system could be safely performed with attenuated renal damage.

Application of actuator-driven pulsed water jet in aneurysmal subarachnoid hemorrhage surgery: its effectiveness for dissection around ruptured aneurysmal walls and subarachnoid clot removal.

In clipping surgery for aneurysmal subarachnoid hemorrhage (aSAH), critical steps include clot removal and dissection of aneurysms without premature rupture or brain injuries. To pursue this goal, a piezo actuator-driven pulsed water jet (ADPJ) system was introduced in this study. This study included 42 patients, who suffered aSAH and underwent clipping surgery. Eleven patients underwent surgery with the assistance of the ADPJ system (ADPJ group). In the other 31 patients, surgery was performed without the ADPJ system (Control group). The ADPJ system was used for clot removal and aneurysmal dissection. The clinical impact of the ADPJ system was judged by comparing the rate of premature rupture, degree of clot removal, and clinical outcomes. Intraoperatively, a premature rupture was encountered in 18.2 and 25.8% of cases in the ADPJ and control groups, respectively. Although the differences were not statistically significant, intraoperative observation suggested that the ADPJ system was effective in clot removal and dissection of aneurysms in a safe manner. Computed tomography scans indicated the achievement of higher degrees of clot removal, especially when the ADPJ system was used for cases with preoperative clot volumes of more than 25ml (p=0.047, Mann-Whitney U test). Clinical outcomes, including incidence of postoperative brain injury or symptomatic vasospasm, were similar in both groups. We described our preliminary surgical results using the ADPJ system for aSAH. Although further study is needed, the ADPJ system was considered a safe and effective tool for clot removal and dissection of aneurysms.

Predicting Tissue Breaking Strengths in the Epileptic Brain with T2 Relaxometry: Application of Pulsed Water Jet Dissection System for Epilepsy Surgery.

Background The piezo actuator-driven pulsed water jet (ADPJ) system is a novel surgical instrument that enables dissection of tissue without thermal damage. Using the ADPJ system in epilepsy surgery requires prediction of the tissue breaking strength of the epileptic brain. The aim of this study was to elucidate whether magnetic resonance imaging T2 relaxometry could predict the breaking strength. Methods A total of 12 patients with drug-resistant temporal lobe epilepsy who received surgical treatment were included in the study. All the patients qualified for surgery after a comprehensive preoperative evaluation for the treatment of epilepsy. T2 relaxation time, breaking strength of the hippocampus, and an anterior temporal lobe specimen obtained from surgery with dissection depth determined by the ADPJ system were examined. Results Preoperative T2 relaxation times of the anterior temporal lobe and hippocampus showed mild positive correlation with breaking strength (R2 = 0.60). The hippocampus showed higher T2 relaxation time than the temporal lobe. Hippocampal sclerosis seemed to have higher breaking strength than other pathologies, suggesting the correlation depends on the anatomical location and histopathology. The dissection depth of the extirpated lesion was negatively correlated with the breaking strength at input voltages of 10 V (R2 = - 0.34) and 20 V (R2 = - 0.20). Conclusions T2 relaxometry may be useful to predict tissue breaking strength in the epileptic brain that allows safe application of the ADPJ system in epilepsy surgery.

Evaluation of a newly developed piezo actuator-driven pulsed water jet system for liver resection in a surviving swine animal model.

Background Preservation of the hepatic vessels while dividing the parenchyma is key to achieving safe liver resection in a timely manner. In this study, we assessed the feasibility of a newly developed, piezo actuator-driven pulsed water jet (ADPJ) for liver resection in a surviving swine model.MethodsTen domestic pigs underwent liver resection. Parenchymal transection and vessel skeletonization were performed using the ADPJ (group A, n = 5) or an ultrasonic aspirator (group U, n = 5). The water jet was applied at a frequency of 400 Hz and a driving voltage of 80 V. Physiological saline was supplied at a flow rate of 7 ml/min. After 7 days, the animals were killed and their short-term complications were examined and compared between the two groups.ResultsNo significant complications, such as massive bleeding, occurred in either group during the surgical procedures. The transection time per transection area was significantly shorter in group A than in group U (1.5 ± 0.3 vs. 2.3 ± 0.5 min/cm2, respectively, P = 0.03). Blood loss per transection area was not significantly different between groups A and U (9.3 ± 4.2 vs. 11.7 ± 2.3 ml/cm2, P = 0.6). All pigs in group A survived for 7 days. No postoperative bleeding or bile leakage was observed in any animal at necropsy.ConclusionThe present results suggested that the ADPJ reduces transection time without increasing blood loss. ADPJ is a safe and feasible device for liver parenchymal transection.

Actuator-driven pulsed water jet surgery system: Initial clinical experience

Actuator-driven pulsed water jet surgery system: Initial clinical experience

Ventricle wall dissection and vascular preservation with the pulsed water jet device: novel tissue dissector for flexible neuroendoscopic surgery.

Neuroendoscopic surgery allows minimally invasive surgery, but lacks effective methods to control bleeding. Water jet dissection with continuous flow has been used in liver and kidney surgery since the 1980s, and is effective for tissue manipulation with vascular preservation, but involves some potential risks, such as elevation of intracranial pressure during application in the ventricles. The authors previously reported the efficacy of the actuator-driven pulsed water jet device (ADPJ) to dissect soft tissue with vascular preservation in microscopic neurosurgery. This feasibility study investigated the use of the ADPJ to reduce the amount of water usage, leading to more safety with sustained efficacy. A small-diameter pulsed water jet device was developed for use with the flexible neuroendoscope. To identify the optimal conditions for the water jet, the flow rate, water pressure, and distance between the nozzle and target were analyzed in an in vitro study by using a gelatin brain phantom. A ventricle model was used to monitor the internal pressure and temperature. For ex vivo experiments the porcine brain was harvested and ventricle walls were exposed, and subsequently immersed into physiological saline. For in vivo experiments the cortex was microsurgically resected to make the small cortico-ventricle window, and then the endoscope was introduced to dissect ventricle walls. In the in vitro experiments, water pressure was approximately 6.5 bar at 0.5 mm from the ADPJ nozzle and was maintained at 1 mm, but dropped rapidly toward 50% at 2 mm, and became 10% at 3.5 mm. The ADPJ required less water to achieve the same dissection depth compared with the continuous-flow water jet. With the ventricle model, the internal pressure and temperature were well controlled at the baseline, with open water drainage. These results indicated that the ADPJ can be safely applied within the ventricles. The ADPJ was introduced into a flexible endoscope and the ventricle walls were dissected in both the ex vivo and in vivo conditions. The ventricle wall was dissected without obscuring the view, and the vascular structures were anatomically preserved under direct application. Histological examination revealed that both the vessels on the ventricle wall and the fine vessels in the parenchyma were preserved. The ADPJ can safely and effectively dissect the ventricle wall, with vascular preservation in immersed conditions. To achieve the optimal result of tissue dissection with minimal surgical risk, the ADPJ is a potential device for neuroendoscopic surgery of the ventricles.

Use of Actuator-Driven Pulsed Water Jet in Brain and Spinal Cord Cavernous Malformations Resection.

A piezo actuator-driven pulsed water jet (ADPJ) system is a novel surgical instrument that enables dissection of tissue without thermal damage. It can potentially resect intra-axial lesions while preserving neurological function. To report our first experience of applying an ADPJ system to brain and spinal cord cavernous malformations. Four patients (2 women and 2 men, mean age 44.5 years) with brain (n = 3) and spinal cord (n = 1) cavernous malformations were enrolled in the study. All surgeries were performed with the aid of the ADPJ system. Postoperative neurological function and radiological findings were evaluated. The ADPJ system was useful in dissecting boundaries between the lesion and surrounding brain/spinal cord tissues. The pulsed water jet provided a clear surgical view and helped surgeons follow the margins. Water jet dissection peeled off the brain and spinal cord tissues from the lesion wall. Surrounding gliotic tissue was preserved. As a consequence, the cavernous malformations were successfully removed. Postoperative magnetic resonance imaging confirmed total removal of lesions in all cases. Preoperative neurological symptoms completely resolved in 2 patients. The others experienced partial recovery. No patients developed new postoperative neurological deficits; facial palsy temporarily worsened in 1 patient who underwent a suprafacial colliculus approach for the brainstem lesion. The ADPJ provided a clear surgical field and enabled surgeons to dissect boundaries between lesions and surrounding brain and spinal cord gliotic tissue. The ADPJ system is a feasible option for cavernous malformation surgery, enabling successful tumor removal and preservation of neurological function.

Experimental Application of Piezoelectric Actuator-Driven Pulsed Water Jets in Retinal Vascular Surgery.

To report on the effectiveness and safety of an ophthalmic piezoelectric actuator-driven pulsed water jet (ADPJ) system adapted for intraocular use. First, we determined the highest ADPJ flow rate that did not cause an unsafe rise in intraoperative intraocular pressure (IOP) in rabbits (n = 4). Next, we determined the most effective ADPJ frequency (in hertz) at that flow rate. Finally, we visualized the ADPJ stream, measured its pressure, and determined the minimum voltage and distance between the ADPJ needle and retinal veins to induce intravenous displacement of the blood column (DBC) through massage of the outer retinal vessels (n = 3) while not causing retinal tearing or hemorrhage. We found that a 0.05 mL/min ADPJ flow rate caused IOP to rise above 40 mm Hg after 1 minute, but that at 0.025 mL/min, IOP stayed below 40 mm Hg even after 3 minutes. Moreover, we found that a 0.025 mL/min ADPJ stream was stable at a pulse frequency of 10 Hz and that at this flow rate/frequency the ADPJ pressure was closely correlated with the applied voltage (P < 0.001, r2 = 0.9991). The minimum voltage and distance to achieve intravenous DBC without causing retinal tearing or hemorrhage were 40 V and 0.5 mm, respectively. With an appropriate flow rate and surgical time, ADPJ successfully induced massage of the retinal vessels and intravenous DBC while maintaining safe IOP and not causing retinal complications. The ADPJ system has promise as a safe and minimally invasive instrument for the intraocular surgical treatment of human retinal vascular diseases.

The Dissection Profile and Mechanism of Tissue-Selective Dissection of the Piezo Actuator-Driven Pulsed Water Jet as a Surgical Instrument: Laboratory Investigation Using Swine Liver

Background/Purpose: The water jet technique dissects tissue while sparing cord-like structures such as blood vessels. The mechanism of such tissue-selective dissection has been unknown. The novel piezo actuator-driven pulsed water jet (ADPJ) system can achieve dissection with remarkably reduced water consumption compared to the conventional water jet; however, the system's characteristics and dissection capabilities on any organ have not been clarified. The purposes of this study were to characterize the physical properties of the novel ADPJ system, evaluate the dissection ability in swine organs, and reveal the mechanism of tissue-selective dissection. Methods: The pulsed water jet system comprised a pump chamber driven by a piezo actuator, a stainless steel tube, and a nozzle. The peak pressure of the pulsed water jet was measured through a sensing hole using a pressure sensor. The pulsed water jet technique was applied on swine liver in order to dissect tissue on a moving table using one-way linear ejection at a constant speed. The dissection depth was measured with light microscopy and evaluated histologically. The physical properties of swine liver were evaluated by breaking strength tests using tabletop universal testing instruments. The liver parenchyma was also cut with three currently available surgical devices to compare the histological findings. Results: The peak pressure of the pulsed water jet positively correlated with the input voltage (R² = 0.9982, p < 0.0001), and this was reflected in the dissection depth. The dissection depth negatively correlated with the breaking strength of the liver parenchyma (R² = 0.6694, p < 0.0001). The average breaking strengths of the liver parenchyma, hepatic veins, and Glisson's sheaths were 1.41 ± 0.45, 8.66 ± 1.70, and 29.6 ± 11.0 MPa, respectively. The breaking strength of the liver parenchyma was significantly lower than that of the hepatic veins and Glisson's sheaths. Histological staining confirmed that the liver parenchyma was selectively dissected, preserving the hepatic veins and Glisson's sheaths in contrast to what is commonly observed with electrocautery or ultrasonic instruments. Conclusions: The dissection depth of liver tissue is well controlled by input voltage and is influenced by the moving velocity and the physical properties of the organ. We showed that the device can be used to assure liver resection with tissue selectivity due to tissue-specific physical properties. Although this study uses an excised organ, further in vivo studies are necessary. The present work demonstrates that this device may function as an alternative tool for surgery due to its good controllability of the dissection depth and ability of tissue selectivity.

Characteristics of an actuator-driven pulsed water jet generator to dissecting soft tissue

This paper reports characteristics of an actuator-driven pulsed water jet generator applied, in particular, to dissect soft tissues. Results of experiments, by making use of high speed recording of optical visualization and varying nozzle diameter, actuator time interval, and their effects on dissection performance are presented. Jet penetration characteristics are compared with continuous water jet and hence potential assessment of pulsed water jets to clinical applications is performed.