Healthy Pulmonary

Clinical Significance

Pulmonary arteries connect blood flow from the heart to the lungs in order to oxygenate blood before being pumped through the body. The main pulmonary artery (MPA) starts at the right ventricle of the heart and divides into the left (LPA) and right pulmonary arteries (RPA), which branch out into the lungs. The main pulmonary artery in healthy subjects has an average diameter of 2.72 cm. Anatomical differences in MPA diameter have also been documented between genders, with a mean MPA diameter of 2.77 cm for males and 2.64 cm for females.

Examples of complications seen in the pulmonary arteries include pulmonary hypertension and pulmonary embolisms. Pulmonary arterial hypertension (PAH) is a chronic disease that occurs when the blood vessels between the heart and lungs narrow and harden, increasing the pressure in the pulmonary arteries. The increased resistance makes it difficult for the heart to pump blood to the lungs, adding strain to and weakening the right ventricle. PAH is a serious condition, with a median survival of less than 3 years if left untreated,causing over 15,000 deaths and 260,000 hospital visits in the United States in 2002.

Significant vascular remodeling is observed in PAH patients, with larger proximal pulmonary arteries and more convoluted branches when compared to healthy patients. In a study examining three-dimensional hemodynamics of the pulmonary arteries, PAH patients were found to have an average main pulmonary diameter of 3.5 ± 0.5 cm, where healthy patients had an average of 2.7 ± 0.1 cm.

A pulmonary embolism is another condition seen the pulmonary arteries, involving one or more arteries being blocked by a blood clot. The blood clots typically originate elsewhere in the body and travel to the pulmonary arteries. The effects of a pulmonary embolism can be quiet severe, with the first sign being sudden death in 25% of pulmonary embolism cases. However, prompt application of anti-clogging medication can help avoid mortality and further complications.

Clinical Data

Patient-specific volumetric image data was obtained to create physiological models and blood flow simulations. The RAS coordinate system was assumed for the image data orientation. Voxel Spacing, voxel dimensions, and physical dimensions are provided in the Right-Left (R ), Anterior-Posterior (A), and Superior-Inferior (S) direction. The patient was 67 years old and female. Details of the image data are listed as below:

Volumetric image data details (CT)

R A S
Voxel Spacing (mm) 0.5859 0.5859 1.25
Voxel Dimensions 512 512 198
Physical Dimensions (mm) 300 300 247.5

Coronal MIP image:

Model Description

The models extend from the main pulmonary artery to various levels of branching in the left and right pulmonary arteries. Using Simvascular and the image data above, the geometrical models are generated by selecting centerline paths along the vessels, creating 2D segmentations along each of these paths, and then lofting the segmentations together to create a solid model. A separate solid model was created for each vessel and Boolean addition was used to generate a single model representing the complete aortofemoral model. The vessel junctions were then blended to create a smoothed model.

Geometric model details

Number of inlets Number of outlets Volume(cm3) Surface Area(cm2) Number of Vessel Paths Number of 2-D Segmentations
1 100 89.08 345.13 101 591

Physiological Assumption

Blood Viscosity Blood Density
0.04 g/cm•s2 1.06 g/cm3

Vessel Paths:

Vessel Segmentations:

Vessel Geometric Model:

Boundary Conditions

Inlet Boundary Conditions

The inflow waveform was adapted to be an average resting pulmonary artery flow waveform for healthy subjects.

Flow Waveform:

Period and Cardiac Output:

Period (s) Cardiac Output (L/min) Profile Type
1.00 4.9799 Plug

Outlet Boundary Conditions

Resistance values for exercise conditions were assigned at each outlet, calculated using the outlet area, LPA/RPA flow split, and pulmonary pressures.

Resistance Values and Presure Offset in cgs and mmHg:

Face Name Rp Po  Face Name Rp Po
LPA_01 64977.0 RPA_01 22937.0
LPA_02 79287.0 RPA_02 20837.0
LPA_03 44647.0 RPA_03 16347.0
LPA_04 30777.0 RPA_04 29027.0
LPA_05 32127.0 RPA_05 23237.0
LPA_06 48817.0 RPA_06 22517.0
LPA_07 42697.0 RPA_07 43537.0
LPA_08 73087.0 RPA_08 21407.0
LPA_09 196177.0 RPA_09 14017.0
LPA_10 196597.0 RPA_10 50247.0
LPA_11 107667.0 RPA_11 44487.0
LPA_12 66137.0 RPA_12 56947.0
LPA_13 46447.0 RPA_13 44127.0
LPA_14 105477.0 RPA_14 29617.0
LPA_15 44577.0 RPA_15 34087.0
LPA_16 56197.0 RPA_16 20317.0
LPA_17 46107.0 RPA_17 38807.0
LPA_18 31857.0 RPA_18 39687.0
LPA_19 60017.0 RPA_19 54317.0
LPA_20 110257.0 RPA_20 68907.0
LPA_21 58227.0 RPA_21 9037.0
LPA_22 235207.0 RPA_22 36747.0
LPA_23 167027.0 RPA_23 36527.0
LPA_24 62907.0 RPA_24 37727.0
LPA_25 65557.0 RPA_25 50577.0
LPA_26 65147.0 RPA_26 61527.0
LPA_27 167727.0 RPA_27 19457.0
LPA_28 53197.0 RPA_28 24987.0
LPA_29 81657.0 RPA_29 32787.0
LPA_30 47327.0 RPA_30 20997.0
LPA_31 125137.0 RPA_31 38477.0
LPA_32 259287.0 RPA_32 23097.0
LPA_33 199747.0 RPA_33 26757.0
LPA_34 40687.0 RPA_34 52057.0
LPA_35 141367.0 RPA_35 35637.0
LPA_36 167847.0 RPA_36 33177.0
LPA_37 228047.0 RPA_37 86327.0
LPA_38 322217.0 RPA_38 56877.0
LPA_39 89857.0 RPA_39 28817.0
LPA_40 83317.0 RPA_40 16507.0
LPA_41 151587.0 RPA_41 54837.0
LPA_42 110987.0 RPA_42 42747.0
LPA_43 102237.0 RPA_43 35047.0
LPA_44 202567.0 RPA_45 108297.0
LPA_45 128107.0 RPA_46 99367.0
LPA_46 38487.0 RPA_47 45587.0
LPA_47 148757.0 RPA_48 20597.0
LPA_48 236347.0 RPA_49 37177.0
LPA_49 116137.0 RPA_50 146297.0
LPA_50 75087.0 RPA_51 16627.0

Simulation & Results

Conservation of mass and Navier-Stokes equations were solved using 3D finite element methods assuming rigid and non-slip walls. The number of time steps per cycle is 1000 with fixed time step size. The simulation was run in cgs units for several cardiac cycles to allow the flow rate and pressure fields to stabilize. Simulation results were quantified for the last cardiac cycle. Paraview, an open-source scientific visualization application, was used to visualize the results. A volume rendering of velocity magnitude for three time points during the cardiac cycle can be seen.

(a)Peak Systole; (b)End Systole; (\(c\))End Diastole

Surface distribution of time-averaged blood pressure (TABP), time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) were also visualized and can be seen.

(a)TABP; (b)TAWSS; (\(c\))OSI