Estimating the transmissibility of H5N1 and the effect of vaccination in Indonesia.

The spread of H5N1 avian influenza continues to pose an economic burden and a public health risk worldwide. Despite this, estimates of the transmissibility of infection exist in only a handful of settings and vary considerably. Using final size methods and flock-level infection data from a field trial of mass vaccination, we obtained the first estimates of the transmissibility of infection between and within flocks in Indonesia. We also found that outbreaks in areas designated as vaccination zones were less transmissible than in non-vaccination zones. However, this reduction is only comparable with a limited degree of protective vaccination coverage. Quantifying the overall effect of vaccination in these zones remains challenging. However, this result would appear to imply that, although the interventions applied in vaccination zones were not sufficient to completely prevent transmission in all areas, when outbreaks occur, they are less transmissible than those in areas where vaccination was not applied. This could be either a direct or an indirect effect of vaccination. Given the dynamism of small-scale poultry production in Indonesia, more regular vaccination may be required to ensure that infection is fully controlled in vaccination zones.

A prospective study of human papillomavirus (HPV) testing to resolve uncertainty in colposcopy.

OBJECTIVE: UK colposcopy services are seeing increased workloads, a large proportion of which are follow-up appointments. The English Cervical Screening Programme HPV Special Interest Group identified five subcategories of colposcopy clinic patients who often require prolonged follow-up regimes for low-grade abnormalities. Human papillomavirus (HPV) testing has a high negative predictive value, meaning that HPV-negative women are at very low risk of underlying disease. Our objectives were to quantify the number of HPV-negative women in each study subcategory and to evaluate the number who could potentially be discharged from colposcopy on the basis of their results. METHODS: Four colposcopy clinics prospectively identified women according to five categories over 12 months. All women underwent cytological testing and high-risk HPV (hrHPV) testing using the Hybrid Capture 2 test. Management outcomes and decisions based on a knowledge of the HPV status were recorded. RESULTS: Data available on 755 women showed that 422/755 (55.9%) and 260/755 (34.4%) had persistent cervical intraepithelial neoplasia grade 1 (CIN1) (Category 1) or a minor abnormality following treatment (Category 2), respectively. In Categories 1 and 2, 51.7% and 60.2%, respectively, were hrHPV negative. The rates with biopsies of CIN2 or worse (CIN2+) across the two categories were 3/355 (0.8%) and 21/291 (7.0%) for hrHPV-negative and hrHPV-positive women, respectively. CONCLUSION: The incorporation of hrHPV testing within organized cervical screening programmes has been widely accepted. hrHPV testing for the clinical scenarios outlined in this study detects women who are hrHPV negative and therefore at low risk of underlying disease, potentially reducing anxiety and inconvenience for women and costs to colposcopy services.

The volume perspective: a comparison of two excisional treatments for cervical intraepithelial neoplasia (laser versus LLETZ).

OBJECTIVE: To compare two excisional treatments, laser cone biopsy and large loop excision of the transformation zone (LLETZ), in terms of the volume of tissue removed, and to determine the relation between the height and the total volume of the cone specimen. DESIGN: Retrospective cross-sectional study. SETTING: Large teaching hospital in London. POPULATION: A total of 1136 eligible excisional treatments (laser cone or large loop excision of the transformation zone, LLETZ). METHODS: Eligible excisional treatments (laser cone or LLETZ) performed between 1 January 2002 and 31 December 2007 in our colposcopy unit were identified using the Infoflex(R) database. The total volume of the cone biopsy was calculated mathematically using the data provided in the histopathology reports. MAIN OUTCOME MEASURES: The volume of the cone biopsy was compared with the technique of excision and the histology grades. RESULTS: Three hundred and thirty-nine laser cone biopsies were performed, whereas 797 LLETZ biopsies were recorded, during the study period. There was no difference in the mean age in the two groups. However, there is a proportional increase in the volume of the cone as the height of the cone increases, and a significant number of the values are skewed, suggesting that the diameter of the base of the cone contributes significantly to the total volume. Laser cone biopsies (median volume 1.84 cm(3), 95% CI 1.98-2.54 cm(3)) account for a larger volume of tissue excised compared with LLETZ (median volume 0.78 cm(3), 95% CI 0.91-1.02 cm(3)) (P < 0.0001). This relationship is not altered when the two procedures are stratified for grade of lesion, i.e. excision for low-grade cervical intraepithelial neoplasia (CIN) (laser median volume 1.55 cm(3), 95% CI 1.46-2.06; LLETZ median volume 0.62 cm(3), 95% CI 0.73-0.88 cm(3)) (P < 0.0001) or high-grade CIN (laser median volume 1.84 cm(3), 95% CI 2.11-2.53 cm(3); LLETZ median volume 0.82 cm(3), 95% CI 0.94-1.07 cm(3)) (P < 0.0001). CONCLUSIONS: The volume of cervical tissue removed during laser conisation is significantly more than that removed with LLETZ. The indication of the cone biopsy does influence the volume of tissue removed.

HPV testing as an adjunct to cytology in the follow up of women treated for cervical intraepithelial neoplasia.

OBJECTIVE: To evaluate human papillomavirus (HPV) testing in combination with cytology in the follow up of treated women. DESIGN: A prospective study. SETTING: Three UK centres: Manchester, Aberdeen and London. POPULATION OR SAMPLE: Women treated for cervical intraepithelial neoplasia (CIN). METHODS: Women were recruited at 6 months of follow up, and cytology and HPV testing was carried out at 6 and 12 months. If either or both results were positive, colposcopy and if appropriate, a biopsy and retreatment was performed. At 24 months, cytology alone was performed. MAIN OUTCOME MEASURES: Cytology and histology at 6, 12 and 24 months. RESULTS: Nine hundred and seventeen women were recruited at 6 months of follow up, with 778 (85%) and 707 (77.1%) being recruited at 12 and 24 months, respectively. At recruitment, 700 women had had high-grade CIN (grades 2 or 3) and 217 had CIN1. At 6 months, 14.6% were HPV positive and 10.7% had non-negative cytology. Of those with negative cytology, 9% were HPV positive. Of the 744 women who were cytology negative/HPV negative at baseline, 3 women with CIN2, 1 with CIN3, 1 with cancer and 1 with vaginal intraepithelial neoplasia (VAIN)1 were identified at 24 months. Nine of 10 cases of CIN3/cervical glandular intraepithelial neoplasia (CGIN) occurred in HPV-positive women. At 23 months, cancer was identified in a woman treated for CGIN with clear resection margins, who had been cytology negative/HPV negative at both 6 and 12 months. CONCLUSIONS: Women who are cytology negative and HPV negative at 6 months after treatment for CIN can safely be returned to 3-year recall.

Hardware-in-the-loop-simulation of the cardiovascular system, with assist device testing application.

This paper presents a technique for evaluating the performance of biomedical devices by combining physical (mechanical) testing with a numerical, computerised model of a biological system. This technique is developed for evaluation of a cardiac assist device prior to in vivo trials. This device will wrap around a failing heart and provide physical beating assistance (dynamic cardiac compression). In vitro, the device to be tested is placed around a simulator comprising a mechanical simulation of the beating ventricles. This hardware model interfaces with a computerised (software) model of the cardiovascular system. In real time the software model calculates the effect of the assistance on the cardiovascular system and controls the beating motion of the hardware heart simulator appropriately. The software model of the cardiovascular system can represent ventricles in various stages of heart failure, and/or hardened or congested blood vessels as required. The software displays physiological traces showing the cardiac output, depending on the natural function of the modelled heart together with the physical assist power provided. This system was used to evaluate the effectiveness of control techniques applied to the assist device. Experimental results are presented showing the efficacy of prototype assist on healthy and weakened hearts, and the effect of asynchronous assist.

Quality control assurance in national screening programmes for cervical cancer.

The United Kingdom established a centrally controlled formal screening programme for cervical cancer in 1988. The programme has been an unprecedented success, with the incidence of cervical cancer falling by an accelerated rate of 7% a year. Underlying the success of the programme is a rigorous system of quality assurance at all levels of activity. Quality assurance assessment in performed for coverage of the target population, cytology reporting laboratories and colposcopy services. Each component in the system is examined annually by mandatory returns, and by regular on-site review of the clinical services by independent authorities. Processes also exist to establish and maintain the competency of all clinical and non-clinical staff involved in the programme. Using nationally published figures from the financial year 2001/2002, the different quality assurance strategies are described. The future development of quality assurance in the programme is then discussed.

Determination of the trabecular bone direction from digitised radiographs.

There is increasing evidence for monitoring the bone trabecular structure to explain, in part, the mechanical properties of bone. Despite the emergence of Computed Tomography, a radiograph is the standard format as it is cheap and used for assessing implant performance. Furthermore, various image-processing techniques developed to assess the trabecular structure from radiographs have regained interest owing to improvements in imaging equipment. This study assessed the precision and accuracy of the Co-occurrence and Run-length matrix, Spatial-frequency and Minkowski-fractal techniques to infer the trabecular direction from radiographs. Ten clinical images of femoral neck regions were obtained from digitised pelvic radiographs and subsequently analysed. These data were also used to generate synthetic images where the trabecular thickness, separation and directions were controlled in order to calculate the accuracy of the techniques. Additionally, a Laplacian noise was added in order to infer the precision of the techniques. All methods assessed the trabecular direction with a high degree of accuracy in these synthetic images including a single direction and no noise. However, only the Spatial-frequency and Co-occurrence matrix methods performed well on the clinical and heavily corrupted synthetic images. This demonstrated the possibility of inferring a linear trabecular direction in clinical conditions.

Activation and extinction models for platelet adhesion.

Adherent platelets are an important part of both thrombus formation and in certain stages of atherogenesis. Platelets can be activated by potent chemicals released from adherent platelets and adhere far more readily than unactivated ones. An analytical and numerical model is presented utilising high Peclet number for the activation and adhesion of platelets in shear flows. The model uses a similarity transformation, which characterises the relationship between convective, diffusive transport and the bulk platelet activating reaction mechanism. A first order surface reaction mechanism is used to model platelet adhesion at the wall (cell) surface. The reduced Damköhler number, M, characterises the importance of the bulk reaction and includes both convective and diffusive terms. For a high rate of blood flow (M-->0) the activation of platelets can effectively be terminated. In contrast, for (M-->infinity) an inner layer of activated platelets exists with an infinitesimally thin reaction sheet separating activated and non-activated platelets. This characterisation by the Damköhler number highlights results found clinically, in that thrombus forms in areas of low shear (high M) and in some cases an increased blood flow (low M) can inhibit the activation of platelets completely. The model shows the critical balance that exists between convection, diffusion and reaction.

Adhesion of leukocytes under oscillating stagnation point conditions: a numerical study.

Leukocyte recruitment from blood to the endothelium plays an important role in atherosclerotic plaque formation. Cells show a primary and secondary adhesive process with primary bonds responsible for capture and rolling and secondary bonds for arrest. Our objective was to investigate the role played by this process on the adhesion of leukocytes in complex flow. Cells were modelled as rigid spheres with spring like adhesion molecules which formed bonds with endothelial receptors. Models of bond kinetics and Newton's laws of motion were solved numerically to determine cell motion. Fluid force was obtained from the local shear rate obtained from a CFD simulation of the flow over a backward facing step.In stagnation point flow the shear rate near the stagnation point has a large gradient such that adherent cells in this region roll to a high shear region preventing permanent adhesion. This is enhanced if a small time dependent perturbation is imposed upon the stagnation point. For lower shear rates the cell rolling velocity may be such that secondary bonds have time to form. These bonds resist the lower fluid forces and consequently there is a relatively large permanent adhesion region.

Evaluation of the precision of magnetic resonance phase velocity mapping for blood flow measurements.

Evaluating the in vivo accuracy of magnetic resonance phase velocity mapping (PVM) is not straightforward because of the absence of a validated clinical flow quantification technique. The aim of this study was to evaluate PVM by investigating its precision, both in vitro and in vivo, in a 1.5 Tesla scanner. In the former case, steady and pulsatile flow experiments were conducted using an aortic model under a variety of flow conditions (steady: 0.1-5.5 L/min; pulsatile: 10-75 mL/cycle). In the latter case, PVM measurements were taken in the ascending aorta of ten subjects, seven of which had aortic regurgitation. Each velocity measurement was taken twice, with the slice perpendicular to the long axis of the aorta. Comparison between the measured and true flow rates and volumes confirmed the high accuracy of PVM in measuring flow in vitro (p > 0.85). The in vitro precision of PVM was found to be very high(steady: y = 1.00x + 0.02, r = 0.999; pulsatile: y = 0.98x + 0.72, r = 0.997; x: measurement #1, y: measurement #2) and this was confirmed by Bland-Altman analysis. Of great clinical significance was the high level of the in vivo precision (y = 1.01x - 0.04, r = 0.993), confirmed statistically (p = 1.00). In conclusion, PVM provides repeatable blood flow measurements. The high in vitro accuracy and precision, combined with the high in vivo precision, are key factors for the establishment of PVM as the "gold-standard" to quantify blood flow.

Population of the vessel wall by leukocytes binding to P-selectin in a model of disturbed arterial flow.

We examined the hypothesis that disturbance of laminar flow promotes the attachment of leukocytes to the vessel wall in regions where the wall shear stress is otherwise too high. Isolated neutrophils, lymphocytes, or monocytes were perfused through chambers with backward-facing steps so that vortices occurred with well-defined reattachment of flow. Wall shear stresses downstream in reestablished flow equaled 0.07 Pa (low shear) or 0.3 Pa (high shear). In chambers coated with P-selectin, adherent leukocytes rolled. By use of a P-selectin-Fc fragment chimera, adhesion was predominantly stationary, enabling definition of initial attachment sites. Neutrophils adhered in all regions of the low-shear chamber, with a local maximum around the reattachment point. However, in the high-shear chamber, adhesion was restricted to the recirculation zone and immediately downstream from the reattachment point. Rolling at high shear stress allowed a population of regions where initial attachment could not occur. At high shear, lymphocytes and monocytes also formed attachments restricted to the region of the reattachment point. The results imply that all types of leukocytes might bind to a capture receptor in high-shear vessels with discontinuities in the wall and might then spread to other regions.

Platelet deposition in stagnation point flow: an analytical and computational simulation.

A mathematical and numerical model is developed for the adhesion of platelets in stagnation point flow. The model provides for a correct representation of the axi-symmetric flow and explicitly uses shear rate to characterise not only the convective transport but also the simple surface reaction mechanism used to model platelet adhesion at the wall surface. Excellent agreement exists between the analytical solution and that obtained by the numerical integration of the full Navier--Stokes equations and decoupled conservation of species equations. It has been shown that for a constant wall reaction rate modelling platelet adhesion the maximum platelet flux occurs at the stagnation point streamline. This is in direct contrast to that found in experiment where the maximum platelet deposition occurs at some distance downstream of the stagnation point. However, if the wall reaction rate is chosen to be dependent on the wall shear stress then the analysis shows that the maximum platelet flux occurs downstream of the stagnation point, providing a more realistic model of experimental evidence. The analytical formulation is applicable to a large number of two-dimensional and axi-symmetrical surface reaction flows where the wall shear stress is known a priori.

Comparison of single-round polymerase chain reaction (PCR) and pepsin-trypsin digest (PTD) methods for detection of Myxobolus cerebralis.

Single-round polymerase chain reaction (PCR) and pepsin-trypsin digest (PTD) methods were compared for the detection of Myxobolus cerebralis. Parallel tests were conducted on a total of 1743 free-ranging and 400 hatchery-reared salmonids. Concurrent results were found in 84.6% of the free-ranging fish samples, and 83.5% of the hatchery samples. PCR identified M. cerebralis more frequently than did PTD, and did so in many geographic locations previously considered free of the parasite. Average myxospore count by PTD among both free-ranging and hatchery fish increased significantly (p < 0.001) with a subjective evaluation of amplicon staining intensity.

Dependence of adhesive behavior of neutrophils on local fluid dynamics in a region with recirculating flow.

We have recently described patterns of adhesion of different types of leukocytes downstream of a backward facing step. Here the predicted fluid dynamics in channels incorporating backward facing steps are described, and related to the measured velocities of flowing cells, patterns of attachment and characteristics of rolling adhesion for neutrophils perfused over P-selectin. Deeper (upstream depth 300 microm, downstream depth 600 microm, maximum wall shear stress approximately 0.1 Pa) and shallower (upstream depth 260 microm, downstream depth 450 microm, maximum wall shear stress approximately 0.3 Pa) channels were compared. Computational fluid dynamics (CFD) predicted the presence of vortices downstream of the steps, distances to reattachment of flow, local wall shear stresses and components of velocity parallel and perpendicular to the wall. Measurements of velocities of perfused neutrophils agreed well with predictions, and suggested that adhesion to P-selectin should be possible in the regions of recirculating flow, but not downstream in re-established flow in the high shear channel. When channels were coated with a P-selectin-Fc chimaera, neutrophils were captured from flow and immobilised. Capture showed local maxima around the reattachment points, but was absent elsewhere in the high shear chamber. In the low shear chamber there was depression of adhesion just beyond the reattachment point because of expansion of flow and depletion of neutrophils near the wall. Inside the recirculation zones, adhesion decreased approaching the step because of an increasing, vertically upward velocity component. When channels were coated with P-selectin, neutrophils rolled in all regions, but lifted off the surface as they rolled backwards into low shear regions near the step. Rolling velocity in the recirculation zone was independent of shear stress, possibly because of the effects of vertical lift. We conclude that while local wall shear stress influences adhesive behavior, delivery of cells to the wall and their behavior after capture also depend on components of flow perpendicular to the wall.

The influence of ventricular input impedance on the hydrodynamic performance of bioprosthetic aortic roots in vitro.

BACKGROUND AND AIM OF THE STUDY: Hydrodynamic function testing using pulsatile flow simulators provides a valuable means of comparative assessment of heart valves in vitro. The majority of pulsatile flow simulators consist of modular rigid chambers and a positive displacement pump with an infinite input impedance, in which the inertia of the test fluid results in pressure oscillations when the valves under test are opening and closing. For mechanical and stented bioprosthetic valves these pressure oscillations decay quickly. However, due to the highly compliant nature of tissue roots, the resulting pressure and flow oscillations are extreme and extend throughout systole. With increasing interest in the use of free-sewn roots and valves it is most desirable to improve this hydrodynamic model. The aim of this study was to investigate the influence in changes in ventricular input impedance on the hydrodynamic characteristics of free-sewn aortic roots and stented valves. METHODS: The Leeds pulsatile flow simulator was modified to incorporate additional compliance chambers in the form of a viscoelastic impedance adaptor (VIA) at the pump/ventricular interface. Six 23 mm bioprosthetic aortic roots fixed with 0.5% buffered glutaraldehyde at zero pressure, and a size 23 mm stented porcine aortic bioprosthesis were tested in this modified simulator, at the conditions of maximum and minimum input compliance. RESULTS: The pressure and flow waveforms for the fixed aortic roots showed considerable differences at the conditions of maximum and minimum input compliance. Indeed, the extreme pressure oscillations observed at minimum compliance (infinite input impedance) were not present at maximum compliance, and the forward flow waveform was much smoother. In contrast, for the stented valve, the differences in the pressure and flow waveforms between maximum and minimum input compliance were minimal, but this was expected due to the lack of compliance in the stented valve itself. In addition, the flow and pressure waveforms at maximum compliance in the VIA were comparable for the fixed aortic roots and the stented bioprosthesis, thus allowing direct comparison of the characteristics of these two different devices. Using test conditions of maximum input compliance, effective orifice area for the roots was 1.69 cm2 compared with 1.47 cm2 for the stented valve. CONCLUSION: An appropriate physiological model for the hydrodynamic testing of compliant tissue roots has been established.

Distribution of hepatic venous blood in the total cavo pulmonary connection: an in vitro study into the effects of connection geometry.

The total cavo pulmonary connection, or TCPC, is a surgical correction to congenital heart defects. The geometry of this connection has been shown to determine the fluid power loss as well as the distribution of hepatic fluid that enters through the inferior vena cava. In vitro studies were performed to measure the power loss and hepatic fluid distribution in models of the TCPC with four different geometries. It was found that a zero offset straight geometry provided good hepatic fluid distribution but large power loss. A zero offset flared geometry provided low power loss but poor hepatic fluid distribution. The optimal geometry from those tested was found to be the zero offset cowl geometry whereby an enlargement was made on one side of the inferior and superior vena cava. So long as the cowl was directed toward the pulmonary artery of lowest flow rate, low power loss and relatively good distribution of hepatic flow could be obtained.

The in vitro hydrodynamic characteristics of the porcine pulmonary valve and root with regard to the ross procedure.

OBJECTIVE: The hydrodynamic parameters and leaflet motion of the porcine pulmonary root and valve and the performance of the pulmonary autograft implanted in subcoronary position or as a free-standing root were investigated at systemic and pulmonary pressures in vitro. METHODS: Ten fresh pulmonary and aortic roots (anulus diameter, 20-25 mm) were tested in a pulsatile flow simulator. Five free-sewn pulmonary valves were implanted in aortic roots in the subcoronary position, and 5 pulmonary roots were implanted as free-standing roots. The external diameter of the roots was measured at the sinotubular junction in a pressure range of 0 to 120 mm Hg. The transvalvular gradient and regurgitation were measured, and the effective orifice area was calculated. The leaflet motion was recorded on video tape. RESULTS: The fresh pulmonary roots were more compliant than their aortic counterparts (33% +/- 3. 0% vs 7% +/- 1.5% with dilatation at 0-30 mm Hg and 46% +/- 8.4% vs 35% +/- 7.8% with dilatation at 0-120 mm Hg). The pulmonary roots had a lower pressure drop at systemic than at pulmonary pressures. The pressure drops of the pulmonary roots were also lower than those of the aortic roots in the systemic pressure range. The leaflet opening of the pulmonary valve was triangular, with low bending deformation at all pressures. Implanting the free-sewn pulmonary valve in the subcoronary position or the pulmonary root as a free-standing root did not affect the hydrodynamic parameters and leaflet motion adversely. CONCLUSION: The pulmonary valve and root could easily withstand aortic pressures in vitro. A biphasic dilatation curve ensures that higher pressures did not overdilate the pulmonary root. Moreover, valve performance was better at systemic pressures.

The effect of sizing on the hydrodynamic parameters of the Medtronic freestyle valve in vitro.

BACKGROUND: An in vitro model has been established to investigate the effect of sizing on the hydrodynamic characteristics and leaflet motion of the Medtronic Freestyle valve. METHODS: The valves were tested in fresh porcine aortic roots. Two or three different sizes of valves were implanted in the same aortic root one after the other. The compliance of the fresh aortic and the composite roots was measured in the pressure range of 0 to 120 mm Hg, and the composite roots were then tested in a pulsatile flow simulator. The transvalvular gradient and degree of regurgitation were measured and the effective orifice area and performance index were calculated. Leaflet motion was recorded on video. RESULTS: The fresh aortic roots dilated by average 39.4% as the hydrostatic pressure rose from 0 to 120 mm Hg. Implantation of the Medtronic Freestyle valve did not change the distensibility of the aortic root significantly. The sizing protocol did not affect significantly the hydrodynamic performance. However, a significantly lower open leaflet bending deformation was found in the undersized valves. Regurgitation was found only at 2-mm undersized valves. CONCLUSIONS: Leaflet motion of the Medtronic Freestyle valve in vitro was best if 1 mm undersized, and this may be beneficial to long-term durability.

Distribution of hepatic venous blood in the total cavo-pulmonary connection: an in vitro study.

OBJECTIVES: The objective of this project was to quantify the effects of geometry on the distribution of hepatic blood to the lungs in patients with a total cavo-pulmonary connection. The basis for this work is the supposition that hepatic blood is necessary for proper lung function. METHODS: Plastic models of these connections were made with varying degrees of offset between the inferior and superior vena cava and attached to an in vitro flow loop. Dye was injected into the inferior vena cava and its concentration quantified in each pulmonary artery. These data were converted to percentage concentration and distribution of hepatic blood to each lung. RESULTS: With no offset between the vena cava, hepatic blood distribution and concentration to each lung was similar to normal. For an offset of one or more diameters, hepatic blood tended to flow preferentially towards the nearest pulmonary artery with the opposite pulmonary artery exhibiting a deficit (<10% of normal). CONCLUSIONS: Distribution of hepatic blood to each lung was found to be a function of vena cava offset and pulmonary artery flow split. Under normal conditions, 60% of blood towards the right pulmonary artery, the hepatic blood distribution to both lungs could be maintained above 50% of normal if the inferior vena cava was offset towards the left pulmonary artery. Offsetting the inferior vena cava towards the right pulmonary artery jeopardized the delivery of hepatic blood to one lung.

Motion correction for the quantification of mitral regurgitation using the control volume method.

Quantifying mitral regurgitation is difficult because of the complexity of the flow, geometry and motion of the mitral valve. In this paper a MRI compatible phantom was built incorporating a left ventricle and mitral valve motion. Valve motion was obtained using a pneumatic piston. The mitral valve was made regurgitant and the regurgitant volume quantified using a modified control volume method. The modification to the method was the addition of mitral motion correction. This was attained by moving the control volume in unison with the mitral valve and by correcting for this motion in the integration of velocity. This correction was found to be simple, in that it represented the volume swept out by the moving control surface. The measured regurgitant volume was compared to a second MR measurement using a single slice technique, made possible by the tubular construction of the phantom's left atrium. Regression analysis between these two methods produced a regression line of y = 0 + 1.02 x; R = 0.97; standard error of the estimate = 3.47 ml.