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Diagram of the experimental setup for the atherectomy device situated in a tube with superimposed throughflow.
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A definitive, quantitative investigation has been per-formed to determine whether orbital atherectomy gives rise to cavitation. The investigation encom-passed a synergistic interaction between in vitro ex-perimentation and numerical simulation. The ex-perimentation was performed in two independent fluid environments: 1) a transparent tube having a...
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... tests, purports to have identified the presence of cavitation bubbles caused by orbital atherectomy. On the other hand, the second article, a totally clinical study, made little mention of cavitation. The last two articles dealt with bubbles created by ultrasound and were focused on damage due to bubble collapse within simulated blood vessels. Attention will now be turned to a discussion of what appears to be the only report of the creation of cavitation bubbles by rotational atherectomy [22]. There are several reasons why the observations reported in this reference may be viewed with some uncertainty. First, the time of bubble collapse reported there is on the order of minutes. Since the involved bubbles had radii on the order of 100 μm, the collapse time should have been in the range of 10 μs according to the aforementioned findings of [21]. Figure 1 of [22] shows that the radial distribution of the bubbles is the same both adjacent to the rotating crown and adjacent to the shaft to which the crown is affixed. However, the rotational velocities at the surface of the crown and at the surface of the bare shaft appear to differ by an order of magnitude, thereby giving rise to very different pressures adjacent to the bare shaft and the crown. In this light, it is difficult to justify comparable distributions of bubbles adjacent to the crown and the bare shaft. Photographs of the bubble field presented in Figures 6 and 7 of [22] show the presence of bubbles in regions distal to the crown that do not contain a rotating device. The mechanism for the creation of the latter-named bubbles is, therefore, unclear. The specific orbital atherectomy device that has motivated this investigation is displayed in Figure 1 . The special feature of this device is that the crown which functions as a sanding surface is positioned eccentrically on the shaft. This off-center positioning creates a secondary motion in addition to the main rotational motion of the shaft. The secondary motion is a precession. It has the virtue of following the contour of the surface of the plaque even as the plaque is removed and the lumen is enlarged. The primary application of the device is for the treatment of peripheral artery disease (PAD). This device has been operated in a large number of clinical settings but no reports have been received which suggest the presence of cavitation. On the other hand, the findings reported by [22] are disquieting and justify a careful evaluation of the cavitation issue. The experiments were performed in two in vitro environments. The first is a large open-topped glass container having a diameter of 80 mm (3.1 in.) and a height of approximately 80 mm (3.1 in.). A schematic diagram of this environment with the rotating atherectomy device in place is exhibited in Figure 2 . As pictured in the figure, in this model the crown is a symmetric widening of the shaft. The shaft diameter is 1.1 mm (0.043 in.). Both symmetric and asymmetric crowns of various dimensions were used in the experiments. Rotational speeds of the shaft were varied between 80,000 and 214,000 rpm. The second experimental environment is a horizontal circular glass tube having a diameter of 6 mm (0.24 in.) and a length of approximately 25 cm (10 in.). This setup is pictured schematically in Figure 3 . A throughflow was superimposed on the rotational motion of the atherectomy device. The use of a throughflow was motivated by the in vivo situation wherein blood and a lubri- cant co-flowed through the artery being ...
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... second experimental environment is a horizontal circular glass tube having a diameter of 6 mm (0.24 in.) and a length of approximately 25 cm (10 in.). This setup is pictured schematically in Figure 3. A throughflow was superimposed on the rotational motion of the ath- erectomy device. ...
Citations
... Abdel-Wahab et al. [15] examined the effect of DCP on drug stents. Ramazani-Rend et al. [16] assessed the effect of cavitation during the DCP process. Some researchers evaluated the effect of rotational speed during the drilling on restenosis after DCP [4,17]. ...
Objective: Drilling of calcifed plaque (DCP) inside the artery is a method for removing calcifed plaques. This study
investigated the efect of drill. To validate the maximum temperature calculated by computer simulation, this value
was also measured by an experimental on a phantom model.
Results: Increasing drill bit diameter during drilling would increase the temperature in vascular nerves. In a drill bit
with a diameter of 4 mm, the risk of thermal necrosis in vascular nerves of the artery wall decreased by 8.57% by
changing the drill from WC to NT. The same value for a drill bit with a diameter of 6 mm was 10.17%. However, the
trend of the generated temperature in the vascular nerves did not change signifcantly with change of the material
and diameter of the drill bit. The results showed that for DCP with the least risk of thermal necrosis in vascular nerves
and subsequently the lowest risk of restenosis, coagulation and thermal stroke of the patient, the best option is to use
a drill bit with a diameter of 4 mm and NT material for drilling.
... Four input parameters were investigated: the rotational speed ( ω), blood-mimicking water flow rate ( Q b ), saline flow rate ( Q s ), and insertion length of the sheath inside blood vessel ( l ). The average blood flow rate was 40 ml/min in the normal popliteal artery [13] . The Q b was set at 40, 20, and 0 ml/min, representing 0%, 50%, and 100% blockage of the artery, respectively. ...
This research studies the catheter friction thermal energy generation and saline temperature in rotational atherectomy (RA). RA is a catheter-based procedure utilizing a high-speed (typically 130,000 to 210,000 rpm) miniature grinding wheel to remove hardened calcified plaque inside the artery to restore the blood flow. During RA, elevated temperature due to the friction within the catheter may lead to complications such as slow-flow/no-reflow and myocardial infarction. RA experiments were conducted to measure the catheter temperature. An advection-diffusion model with inverse heat transfer solution was developed to estimate the spatial and temporal distributions of saline temperature and study effects of the rotational speed, catheter insertion length, and flow rates of blood-mimicking water and saline. The saline temperature rise is higher with higher wheel rotational speed, shorter insertion length, and lower flow rates of blood-mimicking water and saline. The wheel rotational speed and blood flow rate are the two most significant parameters affecting the saline and blood-mimicking water mixture temperature, which exhibits the highest (9 °C) rise under the 175,000 rpm wheel rotational speed and no blood-mimicking water flow (totally occluded artery) condition. This research provides insights and guidelines on RA device and clinical procedure from the thermal perspective.
... Treatment of this type of cardiovascular disease typically fi rst involves dietary and lifestyle changes to reduce the presence of clogging cholesterols within the blood, cholesterol medication, and surgical intervention. Among the most common surgical interventions are balloon angioplasty, stenting, medicated stenting [1][2][3][4][5][6][7], atherectomy [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], or a combination treatment. One positive outcome of these treatments is that they often increase the compliance of the artery wall which is a measure of cardiovascular health [26][27][28][29][30][31][32][33][34][35]. ...
p>A new device has been designed, developed and tested to improve the capacity of vascular drug and stem cell delivery. The device consists of a catheter with a multitude of small lumens (instead of a large central channel lumen). The use of multiple lumens provides a number of benefi ts to medical intervention. First, the multiple lumens are spread across the catheter cross section. As a consequence, the medication/stem cells are more effectively dispersed into the artery. Second, the construction of the new catheter has an increased mechanical strength compared to the standard single-lumen catheter – therefore, it is able to resist compressive forces caused by a pressurized balloon. This fact makes the new design able to preserve medication/stem cell flowrates without causing mechanical hemolysis to the cells. Finally, the newly designed device prohibits clumping of stem cells carried in solution.</p
... Engineering studies that have been conducted on orbital atherectomy include Lovik et al. 's assessment of tissue thermal damage by the finite element simulation model and accompany- ing experimental validation [17] , Ramazani-Rend et al. 's numerical and experimental proof of the absence of cavitation [18] , Helgeson et al. 's investigation of plaque debris trajectory and agglomeration within the blood [19] , Adams et al. 's [20] and Kohler et al. 's [21] ex- perimental examination of particle size and analysis of the crown dynamics without the arterial wall interaction. Missing from this literature review are descriptions, qualitative or quantitative, of the crown motion and contact forces with lesions in orbital atherec- tomy associated with the procedure safety, efficacy (vessel lumen enlargement and tissue softening), and complications such as dis- section and spasm. ...
Orbital atherectomy is a catheter-based minimally invasive procedure to modify the plaque within atherosclerotic arteries using a diamond abrasive crown. This study was designed to investigate the crown motion and its corresponding contact force with the vessel. To this end, a transparent arterial tissue-mimicking phantom made of polyvinyl chloride was developed, a high-speed camera and image processing technique were utilized to visualize and quantitatively analyze the crown motion in the vessel phantom, and a piezoelectric dynamometer measured the forces on the phantom during the procedure. Observed under typical orbital atherectomy rotational speeds of 60,000, 90,000, and 120,000 rpm in a 4.8 mm caliber vessel phantom, the crown motion was a combination of high-frequency rotation at 1000, 1500, and 1660.4-1866.1 Hz and low-frequency orbiting at 18, 38, and 40 Hz, respectively. The measured forces were also composed of these high and low frequencies, matching well with the rotation of the eccentric crown and the associated orbital motion. The average peak force ranged from 0.1 to 0.4 N at different rotational speeds.
... In the present study, a new question will be addressed related to the impact of plaque removal on the flow/pressure relationship. In particular, calcified plaque will be removed using a technique called orbital atherectomy434445. The device is designed to be used either as a stand-alone procedure or more commonly in conjunction with balloon angioplasty. ...
... In the present study, a new question will be addressed related to the impact of plaque removal on the flow/pressure relationship. In particular, calcified plaque will be removed using a technique called orbital atherectomy [43][44][45]. The device is designed to be used either as a stand-alone procedure or more commonly in conjunction with balloon angioplasty. ...
Numerical calculations have been performed to quantify the importance of plaque removal on blood flow. The artery under consideration is the popliteal artery which is susceptible to plaque lesions. An orbital artherectomy device was used to partially remove a calcified plaque layer. Measurements taken before and after the treatment were used in idealized calculations and pressure losses through the lesion were determined. It was found that the removal of plaque by orbital atherectomy increases the blood flowrate through the artery. At the same time, there is a major reduction of pressure loss through the lesion. After treatment, the systolic pressure drop was 2.5 times less than prior to treatment. The cycle-averaged pressure drop was improved by a factor of 3.5. The results are similar for a wide range of plaque lesion lengths (from 3 mm to 18 mm). A deeper investigation into the source of pressure loss reveals that the majority of the loss is confined to the entrance of the lesion and is caused by flow acceleration (and later deceleration) rather than by friction. The calculations were repeated with three increasingly complex numerical methods (steady laminar, unsteady laminar, and unsteady transitional). It was found that all methods were in good agreement so that more computationally expensive techniques are not required in order to obtain accurate results. The results of the simulation were compared with clinical pressure measurements before and after treatment. The two results were found to be in good agreement.
... The present study is aimed at determining how removal of plaque changes the artery compliance. There has been a recent advance in atherectomy procedures and techniques [15,[60][61][62][63][64][65][66]. The procedures have been shown to remove plaque, open clogged arteries, and increase flow rate. ...
p>Cardiovascular disease is a major cause of mortality throughout the world. The history of cardiovascular research is rich and although this study is not intended to be a review of the subject, a short summary related to the present work is necessary. Interested readers are invited to review articles such as [1-4]. These studies are representative of the literature which deal with the complexities of hemodynamics. Among the important subtopics are the relationship between the wall and the fluid. The fluid exerts a shear stress on the wall which is believed to be a causing of thickening of the wall and the initiation of cardiovascaular disease. The flow also has an impact on transport through the arterial wall [5-20].
In addition to these hemodynamic-focused studies, it has been found that arterial compliance (the distension of an artery wall during the cardiac cycle) is an important indicator of disease progression. In particular, for a diseased artery, the stiffened arterial wall or the rigid plaque layer reduces the otherwise healthy-artery response to pressure fluctuations [21-22]. In addition, the presence of a stenosis can affect the blood velocity profile [21-26] which can be measured Doppler or ultrasound techniques [27-37].</p
This chapter describes a photonic sensor system based on laser excitation and CMOS array image capture altogether advanced digital signal processing algorithms. The photonic sensor targets the detection and characterization of cavitation bubbles in multiphase water flows. This sensor finds application in areas where a multiphase water flow is produced, by example bubbling water column reactors, turbine impellers, marine screw and pump-jet propellers where cavitation can be produced, and water-air mixing volumes in dam intakes and spillways in hydroelectric energy generation plants. The photonic sensor comprises an image capture CMOS array with a polymeric tunable optical lens which digitises an area illuminated by a laser diode operating at wavelength 532 nm. This approach permits high-contrast acquisition independent of external lighting conditions. Ad hoc signal processing algorithms are applied on the digitised image in order to evaluate the statistical distribution of bubble size, shape, speed and concentration inside the multiphase flow. Experimental demonstration of the developed sensor indicates its proper operation, being capable of a complete statistical bubble characterization in a water column at 0.01 and 0.05 MPa pressure levels. The performance of different computational methods, including Optical Flow, SIFT and SURF, has been also evaluated in the experimental work for comparison of the underlying image processing algorithms.
Simulations were made of the pressure and velocity fields throughout an artery before and after removal of plaque using orbital atherectomy plus adjunctive balloon angioplasty or stenting. The calculations were carried out with an unsteady computational fluid dynamic solver that allows the fluid to naturally transition to turbulence. The results of the atherectomy procedure leads to an increased flow through the stenotic zone with a coincident decrease in pressure drop across the stenosis. The measured effect of atherectomy and adjunctive treatment showed decrease the systolic pressure drop by a factor of 2.3. Waveforms obtained from a measurements were input into a numerical simulation of blood flow through geometry obtained from medical imaging. From the numerical simulations, a detailed investigation of the sources of pressure loss was obtained. It is found that the major sources of pressure drop are related to the acceleration of blood through heavily occluded cross sections and the imperfect flow recovery downstream. This finding suggests that targeting only the most occluded parts of a stenosis would benefit the hemodynamics. The calculated change in systolic pressure drop through the lesion was a factor of 2.4, in excellent agreement with the measured improvement. The systolic and cardiac-cycle-average pressure results were compared with measurements made in a multi-patient study treated with orbital atherectomy and adjunctive treatment. The agreements between the measured and calculated systolic pressure drop before and after the treatment were within 3%. This excellent agreement adds further confidence to the results. This research demonstrates the use of orbital atherectomy to facilitate balloon expansion to restore blood flow and how pressure measurements can be utilized to optimize revascularization of occluded peripheral vessels.
This research studies the grinding wheel dynamics in orbital atherectomy – a catheter-based minimally invasive procedure to pulverize plaque in atherosclerotic arteries using a diamond grinding wheel. Experiments were conducted to investigate the grinding wheel motion and grinding forces in orbital atherectomy. A high-speed camera and subsequent image processing were utilized to visualize and quantitatively analyze the grinding wheel motion through a transparent arterial tissue-mimicking phantom made of polyvinyl chloride, while the grinding forces were measured by a piezoelectric dynamometer. Observed under typical orbital atherectomy grinding rotational speeds of 60,000, 90,000, and 120,000rpm in a 4.8mm diameter vessel, the grinding wheel motion was a combination of a low-frequency orbiting at 18, 38, 40Hz and a high-frequency rotation of 1000, 1500, and 1660.4-1866.1Hz, respectively. Grinding forces consisted of the high and low frequencies that matched well with the wheel motion.
