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Research Papers

Evaluation of a Voxelized Model Based on DCE-MRI for Tracer Transport in Tumor

[+] Author and Article Information
K. N. Magdoom

 University of Florida, Department of Mechanical and Aerospace Engineering, RM 212 MAE-A, P.O. Box 116250, Gainesville, FL 32611mkulam@ufl.edu

Gregory L. Pishko

 University of Florida, Department of Mechanical and Aerospace Engineering, RM 212 MAE-A, P.O. Box 116250, Gainesville, FL 32611pishko@ohsu.edu

Jung Hwan Kim

 University of Florida, Department of Mechanical and Aerospace Engineering, RM 212 MAE-A, P.O. Box 116250, Gainesville, FL 32611junghwk@gmail.com

Malisa Sarntinoranont1

 University of Florida, Department of Mechanical and Aerospace Engineering, RM 212 MAE-A, P.O. Box 116250, Gainesville, FL 32611msarnt@ufl.edu

1

Corresponding author.

J Biomech Eng 134(9), 091004 (Aug 27, 2012) (9 pages) doi:10.1115/1.4007096 History: Received January 27, 2012; Revised June 02, 2012; Posted July 06, 2012; Published August 27, 2012; Online August 27, 2012

Recent advances in the treatment of cancer involving therapeutic agents have shown promising results. However, treatment efficacy can be limited due to inadequate and uneven uptake in solid tumors, thereby making the prediction of drug transport important for developing effective therapeutic strategies. In this study, a patient-specific computational porous media model (voxelized model) was developed for predicting the interstitial flow field and distribution of a systemically delivered magnetic resonance (MR) visible tracer in a tumor. The benefits of a voxel approach include less labor and less computational time (approximately an order of magnitude reduction compared to the traditional computational fluid dynamics (CFD) approach developed earlier by our group). The model results were compared with that obtained from a previous approach based on unstructured meshes along with MR-measured tracer concentration data within tumors, using statistical analysis and qualitative representations. The statistical analysis indicated the similarity between the structured and unstructured models’ results with a low root mean square error (RMS) and a high correlation coefficient. The voxelized model captured features of the flow field and tracer distribution such as high interstitial fluid pressure inside the tumor and the heterogeneous distribution of the tracer. Predictions of tracer distribution by the voxelized approach also resulted in low RMS error when compared with MR-measured data over a 1 h time course. The similarity in the voxelized model results with experiment and the nonvoxelized model predictions were maintained across three different tumors. Overall, the voxelized model serves as a reliable and swift alternative to approaches using unstructured meshes in predicting extracellular transport within tumors.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 3

Contours of IFP predicted by (a) voxelized model and (b) non-voxelized models. Tumor and skin boundaries are overlaid on the contours. Line plots compare the predicted IFP by the models along the (c) horizontal and (d) vertical bisectors in the mid-slice. The tumor and skin boundaries are represented by dashed and dash-dot lines, respectively.

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Figure 4

Contours of IFV predicted by (a) voxelized model and (b) non-voxelized models. Tumor and skin boundaries are overlaid on the contours. Line plots compare the predicted IFV by both the models along the (c) horizontal and (d) vertical bisectors in the mid-slice. The tumor and skin boundaries are represented by dashed and dash-dot lines, respectively.

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Figure 8

Error histograms for tracer concentration within the tumor for voxel (top row) and non-voxel (bottom row) model results with respect to MR experimental data at t = (a & d) 5, (b & e) 30 and (c & f) 60 min.

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Figure 7

Error histograms for extracellular flow (a, b & c) and tracer transport at t = (d) 5, (e) 30 and (f) 60 mins in baseline simulations for the voxelized model with respect to the non-voxelized model predictions.

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Figure 6

Line plots comparing the predicted tracer concentration in the tissue between the models and experiment along the horizontal (top row) and vertical (bottom row) bisectors of a mid-slice at t = 5 (a & c) and 60 (b & d) mins. The tumor and skin boundaries are represented by dashed and dash-dot lines, respectively.

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Figure 5

Comparison of tracer concentration contours. MR-derived tissue concentration (top row) compared with voxelized model (middle row) and non-voxelized (bottom row) predictions at t = 5 (a, d & g), 30 (b, e & h), and 60 (c, f & i) min. Tumor and skin boundaries are overlaid on the contours.

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Figure 2

CFD compatible meshes. (a) Schematic of voxelized (cartesian) mesh (b) Unstructured mesh of reconstructed hindlimb including tumor (light green), skin (green), cut ends (yellow), and a representation of the mid-slice (dark blue). Number of voxels in the figure were reduced by a factor of 16 for more clarity. Horizontal and vertical lines used for plotting the flow field and tracer transport in (c) voxelized and (d) non-voxelized models.

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Figure 1

Flow chart comparing the computational methods for voxelized and nonvoxelized modeling

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