124 - MRI Sequence Design for 3D Voxel Printing for Partial Nephrectomies

Poster Board Number: 124
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Abstract Body : Purpose of Study
3D printed patient-specific kidney models are proven to help with comprehension of anatomy, decisions on surgical approach, and increasing surgeon confidence in correctly planning the procedure. The standard STL (stereolithography) method fails to capture tissue gradients and blood vessels in a model yet is still considered the standard file format for additive manufacturing. Voxel printing is a novel 3D printing method used for preoperative planning that translates medical images into a 3D model with superior spatial and contrast resolution by addressing the nature of tissues that transition gradually across the interior of their volume. The purpose of this study is to address the representation of smaller scale tissue and vessel organization in voxel printing and apply it to patient-specific kidney models displaying renal carcinoma. Capturing accurate tissue gradients is critical to planning surgical procedures and further refinement of this printing technique would require investigating the blueprint of these models—the medical imaging—and querying which is best for tissue differentiation.

Methods
Digital modeling and voxel printing of 15 retrospective cases of renal carcinoma is completed based on our novel patented bitmap printing protocol. The MRI sequence configurations investigated and compared are several types of T1 and T2-weighted scans. This process includes identifying imaging sequences that contain high resolution images with thin slice acquisition and assessing each sequence's ability to identify 3 major anatomical components of the kidney significant to renal cell carcinoma. Success of methodology will be evaluated visually by a kidney surgeon through a series of photographs and will be based on consistency in MR scan to segmentation to model. A comparison of STL to voxel printing is also done similarly to our protocol, but specific to this project's anatomical components. Finally, a cladistic analysis is created as an opportunity to identify the benefit of investigating MR imaging and to see if advancement in radiology can be predicted.

Results
This effort has resulted in a physical library of exemplar specimens that are voxel-printed in a visually coherent design. The exemplar specimens are models of the renal cortex, renal calyx, as well as the arterial and venous vessels printed with defined MRI protocols. MRI settings to voxel print these models are stated depending on the structure. The result is a patient-specific voxel printed kidney model that overlaps each structure found while querying which scan is best for tissue differentiation, in order to provide a tool for surgeons to use in preoperative planning.

Conclusion
Optimizing medical imaging results in 3D printed models with higher resolution volumetric features of multi-structured tissue organization. The result of our method promised to provide surgeons with a direct translation of volumetric information from imaging for surgical guidance of multiphase imaging sequences in one holistic model.

Significance
The importance of examining the limitation of vessel branching in 3D models is that being able to locate secondary branching would allow clamping of secondary branching rather than primary, which would help in preserving kidney function. The importance of better differentiating tissues in 3D models where renal tumors typically originate is that it allows surgeons to have clearer distinction of the tumor, hence will improve rates of negative surgical margins.