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Carvalho V, Maia I, Souza A, Ribeiro J, Costa P, Puga H, Teixeira S, Lima RA. In vitro
Biomodels in Stenotic Arteries to Perform Blood Analogues Flow Visualizations and Measurements: A Review. Open Biomed Eng J 2020. [DOI: 10.2174/1874120702014010087] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Cardiovascular diseases are one of the leading causes of death globally and the most common pathological process is atherosclerosis. Over the years, these cardiovascular complications have been extensively studied by applying in vivo, in vitro and numerical methods (in silico). In vivo studies represent more accurately the physiological conditions and provide the most realistic data. Nevertheless, these approaches are expensive, and it is complex to control several physiological variables. Hence, the continuous effort to find reliable alternative methods has been growing. In the last decades, numerical simulations have been widely used to assess the blood flow behavior in stenotic arteries and, consequently, providing insights into the cardiovascular disease condition, its progression and therapeutic optimization. However, it is necessary to ensure its accuracy and reliability by comparing the numerical simulations with clinical and experimental data. For this reason, with the progress of the in vitro flow measurement techniques and rapid prototyping, experimental investigation of hemodynamics has gained widespread attention. The present work reviews state-of-the-art in vitro macro-scale arterial stenotic biomodels for flow measurements, summarizing the different fabrication methods, blood analogues and highlighting advantages and limitations of the most used techniques.
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Patient-specific simulation of coronary artery pressure measurements: an in vivo three-dimensional validation study in humans. BIOMED RESEARCH INTERNATIONAL 2015; 2015:628416. [PMID: 25815328 PMCID: PMC4359837 DOI: 10.1155/2015/628416] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 09/10/2014] [Indexed: 02/04/2023]
Abstract
Pressure measurements using finite element computations without the need of a wire could be valuable in clinical practice. Our aim was to compare the computed distal coronary pressure values with the measured values using a pressure wire, while testing the effect of different boundary conditions for the simulation. Eight coronary arteries (lumen and outer vessel wall) from six patients were reconstructed in three-dimensional (3D) space using intravascular ultrasound and biplane angiographic images. Pressure values at the distal and proximal end of the vessel and flow velocity values at the distal end were acquired with the use of a combo pressure-flow wire. The 3D lumen and wall models were discretized into finite elements; fluid structure interaction (FSI) and rigid wall simulations were performed for one cardiac cycle both with pulsatile and steady flow in separate simulations. The results showed a high correlation between the measured and the computed coronary pressure values (coefficient of determination [r2] ranging between 0.8902 and 0.9961), while the less demanding simulations using steady flow and rigid walls resulted in very small relative error. Our study demonstrates that computational assessment of coronary pressure is feasible and seems to be accurate compared to the wire-based measurements.
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Ponzini R, Vergara C, Rizzo G, Veneziani A, Roghi A, Vanzulli A, Parodi O, Redaelli A. Womersley number-based estimates of blood flow rate in Doppler analysis: in vivo validation by means of phase-contrast MRI. IEEE Trans Biomed Eng 2010; 57:1807-15. [PMID: 20659826 DOI: 10.1109/tbme.2010.2046484] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A common clinical practice during single-point Doppler analysis is to measure the centerline maximum velocity and to recover the time-averaged flow rate by exploiting an assumption on the shape of velocity profile (a priori formula), either a parabolic or a flat one. In a previous study, we proposed a new formula valid for the peak instant linking the maximum velocity and the flow rate by including a well-established dimensionless fluid-dynamics parameter (the Womersley number), in order to account for the hemodynamics conditions (Womersley number-based formula). Several in silico tests confirmed the reliability of the new formula. Nevertheless, an in vivo confirmation is missing limiting the clinical applicability of the formula. An experimental in vivo protocol using cine phase-contrast MRI (2-D PCMRI) technique has been designed and applied to ten healthy young volunteers in three different arterial districts: the abdominal aorta, the common carotid artery, and the brachial artery. Each PCMRI dataset has been used twice: 1) to compute the value of the blood flow rate used as a gold standard and 2) to estimate the flow rate by measuring directly the maximum velocity and the diameter (i.e., emulating the intravascular Doppler data acquisition) and by applying to these data the a priori and the Womersley number-based formulae. All the in vivo results have confirmed that the Womersley number-based formula provides better estimates of the flow rate at the peak instant with respect to the a priori formula. More precisely, mean performances of the Womersley number-based formula are about three times better than the a priori results in the abdominal aorta, five times better in the common carotid artery, and two times better in the brachial artery.
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Affiliation(s)
- Raffaele Ponzini
- High Performance Computing Division, Consorzio Interuniversitario Lombardo per l'Elaborazione Automatica, Segrate (MI) 20090, Italy.
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Vergara C, Ponzini R, Veneziani A, Redaelli A, Neglia D, Parodi O. Womersley number-based estimation of flow rate with Doppler ultrasound: sensitivity analysis and first clinical application. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2010; 98:151-160. [PMID: 19879011 DOI: 10.1016/j.cmpb.2009.09.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 09/07/2009] [Accepted: 09/21/2009] [Indexed: 05/28/2023]
Abstract
In this paper we continue in investigating the approach we have proposed in a paper recently published, for a reliable estimate of (peak systolic) blood flow rate from velocity Doppler measurements. Basic features of this approach together with some in silico test cases were discussed in that work. Here, we provide more insights of this approach by performing a sensitivity analysis of the formulas relating blood flow rate to velocity. In particular we analyze how our estimates are affected by perturbation or errors in measurements in comparison with a standard method for catheter based estimates based on the assumption of a parabolic velocity profile. A first glance to in vivo clinical applications is given as well.
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Affiliation(s)
- Christian Vergara
- Department of Information Technology and Mathematical Methods, Università degli Studi di Bergamo, viale Marconi 5, Dalmine (BG), Italy.
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Rittger H, Kuper A, Breithardt OA, Kuon E, Schmidt M, Sinha AM, Blüm B, Jakob A, Brachmann J. A new angiographic method to assess coronary flow reserve-validation in humans. Catheter Cardiovasc Interv 2010; 75:167-73. [PMID: 19924776 DOI: 10.1002/ccd.22251] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Coronary flow reserve (CFR) is defined as the ratio between coronary artery flow during maximal hyperemia and rest. It is considered as a marker for the integrity of the epicardial coronary circulation and the microcirculation. CFR measurement typically requires the introduction of a guide wire into a diseased coronary artery. We tested a new algorithm, which allows to estimate CFR by analysis of coronary angiograms without the need for direct intracoronary measurements. METHODS Twenty seven patients (10 female, mean age 64 +/- 11 years) underwent diagnostic cardiac catheterization for the evaluation of chest pain. A Doppler wire was introduced into the diseased coronary artery and CFR(doppler) was calculated by the flow velocity ratio between rest and maximal hyperemia, induced by intravenous administration of 140 microg of adenosine per kg bodyweight. This was compared to the angiographically determined CFR (CFR(angio)) under the same conditions (rest and induced maximal hyperemia) by densitometry. CFR(angio) was based on the creation of two time density curves representing the disappearance of contrast over time. CFR(angio) was the resulting ratio between the density values during hyperemia and rest. RESULTS An excellent correlation was found between CFR(doppler) and CFR(angio): CFR(angio) = 1 x CFR(doppler) (r = 0.87; P < 0.0001). The average absolute difference between both indeces was 0.36 +/- 0.31. CONCLUSION Measurement of CFR(angio) by densitometry is feasible and provides results, which are comparable to Doppler-derived intracoronary flow velocity measurements.
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Affiliation(s)
- Harald Rittger
- Medizinische Klinik II, Klinikum Coburg gGmbH, Coburg, Germany.
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Garwood S. Measuring Renal Blood Flow with the Intraoperative Transesophageal Echocardiography Probe. Anesth Analg 2009; 108:1371-6. [DOI: 10.1213/ane.0b013e31819ed3f6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Ponzini R, Lemma M, Morbiducci U, Montevecchi FM, Redaelli A. Doppler derived quantitative flow estimate in coronary artery bypass graft: a computational multiscale model for the evaluation of the current clinical procedure. Med Eng Phys 2007; 30:809-16. [PMID: 17980641 DOI: 10.1016/j.medengphy.2007.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 09/12/2007] [Accepted: 09/16/2007] [Indexed: 10/22/2022]
Abstract
In order to investigate the reliability of the so called mean velocity/vessel area formula adopted in clinical practice for the estimation of the flow rate using an intravascular Doppler guide wire instrumentation, a multiscale computational model was used to give detailed predictions on flow profiles within Y-shaped coronary artery bypass graft (CABG) models. At this purpose three CABG models were built from clinical patient's data and used to evaluate and compare, in each model, the computed flow rate and the flow rate estimated according to the assumption of parabolic velocity profile. A consistent difference between the exact and the estimated value of the flow rate was found in every branch of all the graft models. In this study we showed that this discrepancy in the flow rate estimation is coherent to the theory of Womersley regarding spatial velocity profiles in unsteady flow conditions. In particular this work put in evidence that the error in flow rate estimation can be reduced by using the estimation formula recently proposed by Ponzini et al. [Ponzini R, Vergara C, Redaelli A, Veneziani A. Reliable CFD-based estimation of flow rate in haemodynamics measures. Ultrasound Med Biol 2006;32(10):1545-55], accounting for the unsteady nature of blood, applicable in the clinical practice without resorting to further measurements.
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Affiliation(s)
- Raffaele Ponzini
- Department of Bioengineering, Politecnico di Milano, Milan, Italy; Consorzio Interuniversitario Lombardo per l'Elaborazione e l'Automazione (CILEA), Milan, Italy.
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Ponzini R, Vergara C, Redaelli A, Veneziani A. Reliable CFD-based estimation of flow rate in haemodynamics measures. ULTRASOUND IN MEDICINE & BIOLOGY 2006; 32:1545-55. [PMID: 17045876 DOI: 10.1016/j.ultrasmedbio.2006.05.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Revised: 05/15/2006] [Accepted: 05/22/2006] [Indexed: 05/12/2023]
Abstract
Physically useful measures in current clinical practice refer often to the blood flow rate, that is related to the mean velocity. However, the direct measurement of the latter is currently not possible using a Doppler velocimetry technique. Therefore, the usual approach to calculate the flow rate with this technique consists in measuring the maximum velocity and in estimating the mean velocity, making the hypothesis of parabolic profile that in realistic situations results in strongly inaccurate estimates. In this paper, we propose a different way for estimating the flow rate regarded as a function of maximum velocity and Womersley number. This relation is obtained by fixing a parametrised representation and by evaluating the parameters by means of a least-square approach working on the numerical results of CFD simulations (about 200). Numerical simulations are carried out by prescribing the flow rate, not the velocity profile. In this way, no bias is implicitly induced in prescribing boundary conditions. Validation tests based on numerical simulations show that the proposed relation improves the flow rate estimation.
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Affiliation(s)
- Raffaele Ponzini
- Department of Bioengineering, Politecnico di Milano, Segrate (MI), Italy.
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Hillewaert W, Courtens K, McLaughlin M, Wauters J, Wilmer A, Bijnens B, Claus P, Verdonck P, Devos P, Segers P. Numerical assessment of the impact of a flow wire on its velocity measurements. ULTRASOUND IN MEDICINE & BIOLOGY 2006; 32:1025-36. [PMID: 16829316 DOI: 10.1016/j.ultrasmedbio.2006.03.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Revised: 03/02/2006] [Accepted: 03/16/2006] [Indexed: 05/10/2023]
Abstract
Blood flow velocities can be measured using a Doppler flow wire. This numerical study evaluates the impact of a 0.014" flow wire on the measured frequencies in a straight artery with diameters of 3 mm and 4 mm, under steady and pulsatile flow conditions. Simulations were performed with the wires positioned differently in the artery (perfectly centred and at an offset of 0.5 mm from the wall) and with different types of wire (tilted and straight). Measurements were taken at range gates from 4 mm to 10 mm. During simulations using a 3-mm vessel under pulsatile flow conditions, the relative error between the measured and reference maximum frequency (occurring in absence of the wire) decreased from 17.7% to 11.6% (with a mean value of 14.9%). During simulations using an off-centre 1.5 degree tilted wire, the mean error was approximately 5%. Therefore, our study suggests that that a centrally positioned flow wire is unfavourable for measuring flow velocities.
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Affiliation(s)
- Wim Hillewaert
- Cardiovascular Mechanics and Biofluid Dynamics, Institute of Biomedical Technology, Ghent University, Ghent, Belgium
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Sinha Roy A, Back LH, Banerjee RK. Guidewire flow obstruction effect on pressure drop-flow relationship in moderate coronary artery stenosis. J Biomech 2006; 39:853-64. [PMID: 16488224 DOI: 10.1016/j.jbiomech.2005.01.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2004] [Accepted: 01/27/2005] [Indexed: 01/24/2023]
Abstract
To evaluate the local hemodynamic effects of coronary artery balloon angioplasty, computational fluid dynamics was applied to representative stenoses geometry post-angioplasty (minimal lesion diameter d(m) = 1.8mm which produced 64% mean area stenoses) based on a group of patients and measured values of coronary flow reserve (CFR) returning to a normal range (3.6+/-0.3). The computations were at mean flow rates (Q) of 50, 100, 150 and 170 ml/min. The study indicates changes in the hemodynamic conditions due to insertion of a guidewire, which can be used to determine the mean pressure drop (Deltap ) and fall in distal mean coronary pressure (p(r)), and thus give quantitative estimate of uncertainty expected in diagnosis of moderate lesions. The guidewire to minimal lesion diameter ratio is 0.26, causing tighter "artifactual" mean area stenoses of 65.5%. During hyperemia, p(m) dropped to 72 mmHg as compared to 75 mmHg under patho-physiological condition without guidewire. Q(h) (subscript h: hyperemia) decreased from 180 without guidewire to 170 ml/min with the guidewire present. Thus, there was a significant approximately 43% increase in Deltap(h) and a approximately 51% increase in the hyperemic flow resistance (R(h) = Deltap(h)/Q(h)) over the patho-physiological condition. This could cause an overestimation of the severity of the moderate stenoses. Transient and steady flow guidewire surface shear stress was 35-50% higher than corresponding values for arterial wall shear stress. The non-dimensional data given in tabular form may be useful in interpretation of clinical guidewire measurements for moderate lesions of similar geometry and size.
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Affiliation(s)
- Abhijit Sinha Roy
- Department of Mechanical Engineering, University of Cincinnati, 688 Rhodes Hall, PO Box 210072, Cincinnati, OH 45221-0072, USA
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Manoharan G, Pijls NHJ, Lameire N, Verhamme K, Heyndrickx GR, Barbato E, Wijns W, Madaric J, Tielbeele X, Bartunek J, De Bruyne B. Assessment of Renal Flow and Flow Reserve in Humans. J Am Coll Cardiol 2006; 47:620-5. [PMID: 16458147 DOI: 10.1016/j.jacc.2005.08.071] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Revised: 07/25/2005] [Accepted: 08/08/2005] [Indexed: 11/29/2022]
Abstract
OBJECTIVES The purpose of this work was to establish the normal range of maximal renal hyperemic response in humans and to identify the ideal renal vasodilatory stimuli. BACKGROUND Stenotic renovascular atherosclerosis is increasingly treated by percutaneous transluminal renal intervention but with an unpredictable outcome. This may be due to hemodynamically non-significant stenosis or the presence of irreversible damage to the glomerular circulation. We propose that the renovascular hyperemic response may help identify appropriate patients. METHODS In 28 normotensive patients, quantitative angiographic measurements of the renal artery were obtained, and renal artery pressure and flow velocity were continuously recorded after various hyperemic agents. RESULTS In a first group of 11 patients, a significant increase in renal artery average peak velocity (APV) was observed after intrarenal (IR) bolus injection of 600 microg isosorbide dinitrate (41 +/- 19%), 30 mg papaverine (50 +/- 34%), 50 microg dopamine (94 +/- 54%), 0.8 microg x kg(-1) fenoldopam (80 +/- 25%), and during IR infusion of 1 microg x kg(-1) x min(-1) fenoldopam (86 +/- 28%). A second group of 17 patients received intravenous infusion of dopamine (3, 5, 10, 20, 30, and 40 microg x kg(-1) x min(-1)). The 3 and 5 microg x kg(-1) x min(-1) of dopamine modestly reduced renal resistance index (RI) (-13 +/- 15% and -25 +/- 20%, respectively). At higher dosages, no further decline in RI was observed. No significant change in vessel diameter was observed before and after the administration of the pharmacological stimuli suggesting that changes in APV corresponded with changes in absolute renal blood flow. CONCLUSIONS The normal renal flow reserve averages approximately 2 in humans with normal renal function. An IR bolus injection of 50 microg x kg(-1) of dopamine is the most convenient means to elicit maximal renal hyperemia.
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Van Herck PL, Vrints CJ, Carlier SG. Coronary Circulation and Interventional Cardiology. Ann Biomed Eng 2005; 33:1735-42. [PMID: 16389522 DOI: 10.1007/s10439-005-8778-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2005] [Accepted: 06/03/2005] [Indexed: 10/25/2022]
Abstract
Cardiovascular disease has long been the leading cause of death in developed countries and it is rapidly becoming the number one killer in developing countries. Sudden heart attacks remain the primary cause of death in the United States: over 1.4 million attacks are suffered every year, more than half of which prove fatal. Interventional Cardiology is aimed to alleviate symptoms of cardiac pains and poor coronary circulation, and reduce the risk of death and nonfatal myocardial infarction. Our understanding of the coronary circulation has improved several folds due to the introduction of advance technologies. Yet, the microcirculatory flow needs future investigation.
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Affiliation(s)
- P L Van Herck
- Department of Cardiology, Antwerp University, Belgium
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Sinha Roy A, Banerjee RK, Back LH, Back MR, Khoury S, Millard RW. Delineating the guide-wire flow obstruction effect in assessment of fractional flow reserve and coronary flow reserve measurements. Am J Physiol Heart Circ Physiol 2005; 289:H392-7. [PMID: 15734887 DOI: 10.1152/ajpheart.00798.2004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hemodynamic analysis was conducted to determine uncertainty in clinical measurements of coronary flow reserve (CFR) and fractional flow reserve (FFR) over pathophysiological conditions in a patient group with coronary artery disease during angioplasty. The vasodilation-distal perfusion pressure (CFR-p(rh)) curve was obtained for 0.35- and 0.46-mm guide wires. Our hypothesis is that a guide wire spanning the lesions elevates the pressure gradient and reduces the flow during hyperemic measurements. Maximal CFR-p(rh) was uniquely determined by the intersection of measured CFR and calculated p(rh) of native and residual epicardial lesions in patients without microvascular disease, during angioplasty. Extrapolation of the linear curve gave a zero-coronary flow mean pressure (p(zf)) of approximately 20 mmHg and a corresponding p(rh) of 55 mmHg in the native lesions, which coincided with the level that causes ischemia in human hearts. On this linear curve, values of CFR and FFRmyo (pathophysiological condition) and CFRg and FFRmyog (in the presence of the guide wire) were obtained in native and residual lesions. A strong linear correlation was found between CFR and CFRg [CFR = CFRg x 0.689 + 1.271 (R2= 0.99) for 0.46 mm and CFR = CFRg x 0.757 + 1.004 (R2= 0.99) for 0.35 mm] and between FFRmyo and FFRmyog [FFRmyo = FFRmyog x 0.737 + 0.263 (R2= 0.99) for 0.46 mm and FFRmyo = FFRmyog x 0.790 + 0.210 (R2= 0.99) for 0.35 mm]. This study establishes a strong correlation between CFR and CFRg and between FFRmyo and FFRmyog, which could be used to obtain the true state of occlusion in the coronary artery during angioplasty.
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Affiliation(s)
- Abhijit Sinha Roy
- Dept. of Mechanical Engineering, 688 Rhodes Hall, PO Box 210072, Cincinnati, OH 45221-0072, USA
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Andrews RT, Binkert CA. Relative rates of blood flow reduction during transcatheter arterial embolization with tris-acryl gelatin microspheres or polyvinyl alcohol: quantitative comparison in a swine model. J Vasc Interv Radiol 2004; 14:1311-6. [PMID: 14551279 DOI: 10.1097/01.rvi.0000092903.31640.70] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE To determine whether two commonly used embolic agents have differing rates of blood flow reduction during transcatheter embolization of the renal arteries in an animal model. MATERIALS AND METHODS The renal arteries of 10 pigs were embolized with either polyvinyl alcohol (300-500 or 500-700- micro m) or tris-acryl gelatin microspheres (300-500 or 700-900- micro m). Equivalent unit doses of each agent were suspended in 40 mL of fluid and injected in 1-mL aliquots for 20 mL and then in 5-mL aliquots for 20 mL. Blood flow was measured after each aliquot with an intraarterial Doppler flow wire placed through the embolization catheter. RESULTS Renal arterial blood flow was most rapidly and reliably decreased by 300-500- and 700-900- micro m microspheres, both of which had achieved >90% reduction from baseline flow after the injection of 6 mL of suspension. An equivalent reduction in flow required 25 mL of 300-500- micro m PVA suspension and 30 mL of 500-700- micro m PVA suspension. The reduction in blood flow with microspheres was significantly greater (P <.05) than that with PVA between 5 and 19 mL of suspension delivered. Differences between larger and smaller particle sizes of the same agent were not statistically significant. CONCLUSIONS Tris-acryl gelatin microspheres reduced renal blood flow more quickly and reliably than did PVA. The type of agent used in embolization had a greater impact on the rate of flow reduction than did particle size in the range of sizes tested.
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Affiliation(s)
- Robert T Andrews
- Dotter Interventional Institute, University of Washington Medical Center, 1959 NE Pacific St., RR 215, Box 357115, Seattle, Washington 98195-7115, USA.
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Yu N, Polycarpou AA, Wagoner Johnson AJ. Measuring mechanical properties of fine-wire cross-sections used in medical devices. ACTA ACUST UNITED AC 2004; 70:106-13. [PMID: 15199590 DOI: 10.1002/jbm.b.30027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this study, it was demonstrated that the nanoindentation technique can be used to measure the elastic modulus and hardness of fine-wire cross-sections with diameters ranging from 100-200 microm. Using miniature optics and a specially developed micrometer positioning system, measurements were successfully performed on the wire cross-sections with an accuracy of 1 microm. Homogeneous wire cross-sections, such as MP35N (high-strength nickel-cobalt alloy), composite wires such as MP35N with a silver core (MP35N/Ag-core), and platinum-clad tantalum (Pt-clad Ta) were studied. From the nanoindentation measurements, the elastic modulus and hardness at different positions and depths were calculated. It was found that both elastic modulus and hardness reached a constant value below the hardened surface, which resulted from mechanical polishing. Material properties obtained from the measurements were compared with the literature values of bulk materials as well as available results on fine wires. The data from the wire cross-sections, especially the uniform material samples, showed that both the elastic modulus and hardness were significantly lower near the outer 10-15 microm of the wire as compared to the rest of the wire, which is due to surface weakening during manufacturing. In addition, both modulus and hardness showed a small but consistent "sawtooth" variation across the diameter of the wires, excluding the outer 10-15 microm, that is postulated to be induced by the distribution of residual stress.
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Affiliation(s)
- Ning Yu
- Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Jenni R, Kaufmann PA, Jiang Z, Attenhofer C, Linka A, Mandinov L. In vitro validation of volumetric blood flow measurement using Doppler flow wire. ULTRASOUND IN MEDICINE & BIOLOGY 2000; 26:1301-1310. [PMID: 11120368 DOI: 10.1016/s0301-5629(00)00265-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Determination of any volumetric blood flow requires assessment of mean blood flow velocity and vessel cross-sectional area. For evaluation of coronary blood flow and flow reserve, however, assessment of average peak velocity alone is widely used, but changes in velocity profile and vessel area are not taken into account. We studied the feasibility of a new method for calculation of volumetric blood flow by Doppler power using a Doppler flow wire. An in vitro model with serially connected silicone tubes of known lumen diameters (1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mm) and pulsatile blood flow ranging from 10 to 200 mL/min was used. A Doppler flow wire was connected to a commercially available Doppler system (FloMap(R), Cardiometrics) for online calculation of the zeroth (M(0)) and the first (M(1)) Doppler moment, as well as mean flow velocity (V(m)). Two different groups of sample volumes (at different gate depths) were used: 1. two proximal sample volumes lying completely within the vessel were required to evaluate the effect of scattering and attenuation on Doppler power, and 2. distal sample volumes intersecting completely the vessel lumen to assess the vessel cross-sectional area. Area (using M(0)) and V(m) (using M(1)/M(0)) obtained from the distal gates were corrected for scattering and attenuation by the data obtained from the proximal gates, allowing calculation of absolute volumetric flow. These results were compared to the respective time collected flow. Correlation between time collected and Doppler-derived flow measurements was 0.98 (p < 0.0001), with a regression line close to the line of equality indicating an excellent agreement of the two measurements in each individual tube. The mean paired flow difference between the two techniques was 1.5 +/- 9.0 mL/min (ns). Direct volumetric blood flow measurement from received Doppler power using a Doppler flow wire system is feasible. This technique may potentially be of great clinical value because it allows an accurate assessment of coronary flow and flow reserve with a commercially available flow wire system.
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Affiliation(s)
- R Jenni
- University Hospital Zurich, Division of Cardiology, Echocardiography, Zurich, Switzerland
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CARLIER STÉPHANEG, LANGENHOVE GLEN, LUPOTTI FERMIN, ALBERTAL MARIANO, MASTIK FRITS, BOM KLAAS, SERRUYS PATRICKW. Coronary Flow Reserve Versus Geometric Measurements of Coronary Dimensions: Advantages and Limitations of the Functional Stenosis Assessment. J Interv Cardiol 1999. [DOI: 10.1111/j.1540-8183.1999.tb00669.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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