Atherosclerosis is one of the main reasons for cardivascular disease which cause many deaths every year especially in the Western world. The development of atherosclerosis is strongly believed to be influenced by hemodynamic forces in the arteries e.g. wall shear stress (WSS). Estimations of WSS are therefore very important. By combining magnetic resonance imaging (MRI), image processing and computational fluid dynamic (CFD) simulations, it is possible to estimate subject specific WSS in the human arteries. The framework for performing such work includes i.e. using inlet boundary conditions which, however, will influence the final result i.e. the WSS distribution. This paper aims to investigate the influence of the inflow boundary condition in the human aorta with comparing two settings for the inflow: 1) subject specific inlet profile measured with MRI and 2) uniform profile with the subject specific mass flow rate. The analysis of WSS will be performed both on spatial location along the artery as well as on the temporal location in the cardiac cycle. Subject specific data have been used for geometry, inflow velocity profile and blood viscosity. The recommendation due to our findings from nine healthy subjects, is that a measured subject specific inlet boundary condition must be used in order to get a subject specific WSS distribution; the difference in WSS is 8-34% compared to using a mass-flow correct uniform profile. Temporal variations were clearly seen in the WSS differences due to the different inflow velocity profiles used. The lowest influence of the inlet boundary condition was found at peak velocity in the cardiac cycle. The aortic geometry does not form the flow in such extent (compared to the influence by inlet boundary condition) to obtain a more correct WSS distribution further away from the inlet at the systolic parts of the cardiac cycle. The shape of the vessel has only a significant influence at low velocities i.e. the diastolic phase of the cardiac cycle.

A detailed and a simplified model of a lesioning electrode was made using the finite element method. 15 simulations of the lesioning procedure were performed for each model and the resulting lesion volumes were compared in order to investigate if the simplified model is adequate. The simplified model resulted in a very slight overestimation of the volume compared to the detailed model. It was thus concluded that the simplified model is adequate for simulations.

Bio-heat transfer, - heat transfer affecting living organism under the influence of blood perfusion -, is given great and increasing attention in medicine today. One reason is the increasing use of thermal treatment methods in for example heart- and neuro-surgery. Analysis and modelling of the thermal aspects is frequently carried out at every stage of device and method development, as it exhibits unique possibilities to understand the complex interactions present. This work investigates the use of a hybrid bio-heat model/equation, which is subsequently used to analyse temperature measurement during thermal treatment of the prostate.

Errors in body temperature measurement might seriously influence the evaluation of an individual's health condition. We studied individual variation, measurement technique and the equipment used when assessing body temperature. In the first part of the study, three volunteers performed repeated measurements for five mornings. In the second part, the morning rectal, oral, ear and axillary temperatures were measured once in 84 men and women (19-59 years). The repeated measurements showed a daily temperature difference of 0.1-0.4 degrees C in rectal and oral temperatures, 0.2 degrees C-1.7 degrees C in the ear and 0.1-0.9 degrees C in the axillary temperatures. In the sample of 84 subjects, men and postmenopausal women had a lower mean body temperature compared to premenopausal women. The mean deviation between rectal temperature, and oral, ear and axillary temperatures, respectively, was > 0.5 degrees C, with a large individual variation. In conclusion, in order to improve the evaluation of body temperature, the assessment should be based on the individual variation, the same site of measurement and no adjustment of oral, ear or axillary temperatures to the rectal site.

BACKGROUND:In aortic prosthetic valves, both the Doppler-estimated gradients and orifice areas are misleading in the assessment of hemodynamic performance. The parameter of major interest is the net pressure gradient after pressure recovery (PR). We, therefore, investigated, in vitro, our ability to predict the net pressure gradient and applied the formulas in a representative patient population with 2 different valve designs.METHODS:We studied the St Jude Medical (SJM) standard valve (size 19-27) and SJM Biocor (size 21-27) in an in vitro steady-flow model with simultaneous Doppler-estimated pressure and catheter pressure measurements. Using echocardiography, we also studied patients who received the SJM (n = 66) and SJM Biocor (n = 45).RESULTS:In the SJM, we observed PR both within the prosthesis and aorta, whereas in the SJM Biocor, PR was only present in the aorta. We estimated the PR within the valve and within the aorta separately from echocardiographic in vitro data, combining a regression equation (valve) with an equation on the basis of fluid mechanics theory (aorta). The difference between estimated and catheter-obtained net gradients (mean +/- SD) was 0.6 +/- 1.6 mm Hg in the SJM and -0.2 +/- 1.9 mm Hg in the SJM Biocor. When these equations were applied in vivo, we found that PR had an overall value of 57 +/- 7% of the peak Doppler gradient in the SJM and 33 +/- 9% in the SJM Biocor.CONCLUSIONS:The in vitro results indicate that it is possible to predict the net pressure gradient by Doppler in bileaflet and stented biologic valves. Our data indicate that important PR is also present in stented biologic valves.

Bio-heat equations (BHEs) are necessary for predicting tissue temperature during thermal treatment. For some applications, however, existing BHEs describe the convective heat transfer by the blood perfusion in an unsatisfactory way. The two most frequently used equations, the BHE of Pennes and the k eff equation, use for instance either a heat sink or an increased thermal conductivity in order to account for the blood perfusion. Both these methods introduce modelling inaccuracies when applied to an ordinary tissue continuum with a variety of vessel sizes. In this study, a hybrid equation that includes both an increased thermal conductivity and a heat sink is proposed. The equation relies on the different thermal characteristics associated with small, intermediate and large sized vessels together with the possibilities of modelling these vessels using an effective thermal conductivity in combination with a heat sink. The relative importance of these two terms is accounted for by a coefficient g . For g = 0 and g = 1, the hybrid equation coincides with the BHE of Pennes and the k eff equation, respectively. The hybrid equation is used here in order to simulate temperature fields for two tissue models. The temperature field is greatly affected by g , and the effect is dependent on, e.g. the boundary conditions and the power supply. Since the BHE of Pennes and the k eff equation are included in the hybrid equation, this equation can also be useful for evaluation of the included equations. Both these heat transfer modes are included in the proposed equation, which enables implementation in standard thermal simulation programmes.

To clinically measure blood pressure at extra corporeal bloodlines involves a hazard due to the infection risk and a risk for thrombosis formation. The aim was to design a non-invasive pressure sensor, measuring directly on a tube section. A modified tube cross-section was used to improve sensitivity. Using the developed sensing principle, a consistent relation (r=0.999) was obtained between pressure and output signal. The output was stable and an acceptable drift within the temperature-range. The method shows great promise for applications in monitoring of the dialysis process.

During ablative neurosurgery of movement disorders, for instance therapy of Parkinson's disease, temperature monitoring is crucial. This study aims at a quantitative comparison of measurement deviations between the maximum temperature located outside the lesioning electrode and two possible thermocouple locations inside the electrode. In order to obtain the detailed temperature field necessary for the analysis, four finite element models associated with different surroundings and with different power supplies are studied. The results from the simulations show that both the power level and the power density as well as the surrounding medium affect the temperature measurement and the temperature field in general. Since the maximum temperature is located outside the electrode there will always be a deviation in time and level between the measured and the maximum temperature. The deviation is usually 2–7 s and 3–12°C, depending on, for example, the thermocouple location and surrounding medium. Therefore, not only the measured temperature but also the relation between measured and maximum temperature must be accounted for during therapy and device design.

A common demand today at universities world wide is education of more students with higher quality at a reduced cost. One possibility to solve the problem is a distributed training programme. CORTECH tutor is such a graduate training programme in biomedical engineering. The programme is organized by three different universities in Sweden-Karolinska Institute in Stockholm, Linkoping University in Linkoping and Lund University in Lund. The CORTECH tutor has received financial support from the Swedish Foundation for Strategic Research, SSF

The aim of this study was to develop a finite element model for simulation of the thermal characteristics of brain electrodes and to compare its performances with an in vitro experimental albumin model. Ten lesions were created in albumin using a monopolar electrode connected to a Leksell Neuro Generator and a computer-assisted video system was used to determine the size of the generated lesions. A finite element model was set up of the in vitro experiments using the same thermal properties. With a very simple heat source applied to the finite element model in the proximity of the upper part of the tip, a good agreement (no deviations in width and distance from tip but a deviation in length of −1.6 mm) with the in vitro experiments (width 4.6±0.1 mm and length 7.4±0.1 mm) was achieved when comparing the outline of the lesion. In addition, a gelatinous albumin-model was set up and compared to computer simulations resulting in deviations in width of −0.4 mm, length of −2.2 mm and distance from the tip of −0.1 mm. Hence, the utilisation of finite element model simulations may be a useful complement to in-vitro experiments.

Catheterization and Cardiovascular DiagnosisVolume 43, Issue 1 p. 108-110 Preliminary Report Bubble at tip of the stent delivery system of the Palmaz-Schatz stent improves trackability to the target site Kenichi Fujise MD, Corresponding Author Kenichi Fujise MD Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasDivision of Cardiology, University of Texas Health Science Center, 6431 Fannin Street, Suite 4200, Houston, TX 77030Search for more papers by this authorMazen Ganim MD, Mazen Ganim MD Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasSearch for more papers by this authorDan Loyd BS, RT, Dan Loyd BS, RT Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasSearch for more papers by this authorGeorge Schroth MD, George Schroth MD Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasSearch for more papers by this authorRichard W. Smalling MD, PhD, Richard W. Smalling MD, PhD Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasSearch for more papers by this author Kenichi Fujise MD, Corresponding Author Kenichi Fujise MD Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasDivision of Cardiology, University of Texas Health Science Center, 6431 Fannin Street, Suite 4200, Houston, TX 77030Search for more papers by this authorMazen Ganim MD, Mazen Ganim MD Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasSearch for more papers by this authorDan Loyd BS, RT, Dan Loyd BS, RT Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasSearch for more papers by this authorGeorge Schroth MD, George Schroth MD Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasSearch for more papers by this authorRichard W. Smalling MD, PhD, Richard W. Smalling MD, PhD Division of Cardiology, University of Texas Health Science Center and Hermann Hospital, Houston TexasSearch for more papers by this author First published: 06 December 1998 https://doi.org/10.1002/(SICI)1097-0304(199801)43:1<108::AID-CCD31>3.0.CO;2-JCitations: 6AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume43, Issue1January 1998Pages 108-110 SCAI Member Sign in RelatedInformation

Catheterization and Cardiovascular DiagnosisVolume 44, Issue 3 p. 367-367 Letter to the Editor Reply to the letter to the editor by Corcos et al. Kenichi Fujise MD, Corresponding Author Kenichi Fujise MD Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasHermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this authorMazen Ganim MD, Mazen Ganim MD Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this authorDan Loyd BS, RT, Dan Loyd BS, RT Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this authorGeorge Schroth MD, George Schroth MD Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this authorRichard W. Smalling MD, PhD, Richard W. Smalling MD, PhD Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this author Kenichi Fujise MD, Corresponding Author Kenichi Fujise MD Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasHermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this authorMazen Ganim MD, Mazen Ganim MD Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this authorDan Loyd BS, RT, Dan Loyd BS, RT Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this authorGeorge Schroth MD, George Schroth MD Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this authorRichard W. Smalling MD, PhD, Richard W. Smalling MD, PhD Hermann Hospital and Division of Cardiology, University of Texas-Houston Health Science Center, Houston, TexasSearch for more papers by this author First published: 06 December 1998 https://doi.org/10.1002/(SICI)1097-0304(199807)44:3<367::AID-CCD33>3.0.CO;2-FAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume44, Issue3July 1998Pages 367-367 SCAI Member Sign in RelatedInformation

Parison formation in a narrow neck press and blow process for glass container forming is studied. Heat transfer in the plunger; glass and blank mould during parison formation is analysed by a numerical model A finite difference formulation is used for the heat transfer calculations. The transient heat transfer during the parison forming is a combination of radiation and conduction. The heat transfer from the glass to the plunger and blank mould is influenced by the contact resistance between glass and manufacturing equipment. The contact resistance is calculated as a function of plunger pressure and glass temperature. The temperature distribution in the parison after the forming process is determined mainly by the surface temperature of the blank mould and the plunger: The influence of the radiation heat flux in the glass is found to be negligible compared to the conduction heat flux. The surface temperature is affected mainly by the plunger pressure and the cooling of the manufacturing equipment. If the cooling or the pressure is changed the temperature of the manufacturing equipment will change relatively slowly accompanied by a change in the parison temperature distribution.

A numerical method for analysis of temperature and heat transfer in patients undergoing hyperthermia treatment of the prostate is presented. The domain to be analysed is irregular in shape and consists of several materials and tissues with different thermal properties and complex boundary conditions. The blood vessels have temperature-dependent flow and the physical properties also depend on the temperature. The finite element formulation of the problem makes it possible to analyse different types of hyperthermia treatments, e.g. treatment of an enlarged prostate. The application shown here is a simulation performed in order to evaluate a thermal injury in a patient undergoing hyperthermia treatment because of symptomatic prostatic enlargement.

A mathematical model for the steady-state transport of analyte to a catalytic-metal-gate gas sensor directly exposed to a laminar gas flow in a duct is derived. The model is utilized in order to examine under what conditions problems with mass-transfer-limited response will occur for a measurement situation commonly encountered when catalytic-metal-gate semiconductor devices are used as gas sensors. Quantitative predictions for the lowering of the measured analyte concentration as compared to the nominal one are made for different total flows, sensor areas and reactive sticking coefficients. It is found that for square catalytic surfaces larger than 0.25 mm2 and reactive sticking coefficients higher than 10−4, the measured analyte concentration is significantly lower than the nominal concentration.

Continuous-wave Doppler signal intensity is commonly expected to reflect the severity of mitral regurgitation. Physical principles predict that alignment of the imaging beam, flow velocity, and turbulence can also be important or even dominant determinants of continuous-wave Doppler signal intensity. The reliability of tracking regurgitant severity with continuous-wave Doppler signal intensity was assessed in vitro with varying volume, velocity, turbulence, and beam alignment. The conditions wherein continuous-wave Doppler signal intensity increased with regurgitant volume were specific but poorly predictable combinations of orifice size, flow volume, and perfect beam alignment. Under other conditions flow velocity and turbulence effects dominated, and continuous-wave Doppler signal intensity did not reflect changing regurgitant volume. Continuous-wave Doppler signal intensity-based impressions of regurgitant severity may be unreliable and even misleading under some circumstances.

Since valvular regurgitation is one of the most common malfunctions of the heart the quantification of valvular regurgitation by means of non-invasive methods is desired. However existing methods for quantitative assessment is far from perfect. The aim of this paper is to study the proximal velocity field for non-stationary flow and non-planar geometries by computer simulation, which were performed using the FIDAP package to numerically solve the governing equations. A plexiglass in-vitro model similar to the computer model was used for comparison and the same results were obtained. The authors have found that it is possible to refine the PISA method and standardize flow calculations. Further improvements will hopefully create a tool for the echocardiographer that will facilitate evaluation and clinical applicability of the PISA approach

A 71-year-old man was treated with transurethral microwave thermotherapy because of symptoms of benign prostatic hyperplasia. The treatment session was performed without any abnormal complaints from the patient. Two hours post-treatment the patient felt pain in his penile shaft and noticed a wound. A thorough investigation revealed that the only possible explanation for the injury was a dislocation of the catheter.