The residual STL volume as a metric to evaluate accuracy and reproducibility of anatomic models for 3D printing: application in the validation of 3D-printable models of maxillofacial bone from reduced radiation dose CT images

Tianrun Cai; Frank J Rybicki; Andreas A Giannopoulos; Kurt Schultz; Kanako K Kumamaru; Peter Liacouras; Shadpour Demehri; Kirstin M Shu Small; Dimitris Mitsouras

doi:10.1186/s41205-015-0003-3

The residual STL volume as a metric to evaluate accuracy and reproducibility of anatomic models for 3D printing: application in the validation of 3D-printable models of maxillofacial bone from reduced radiation dose CT images

3D Print Med. 2015;1(1):2. doi: 10.1186/s41205-015-0003-3. Epub 2015 Nov 27.

Authors

Affiliations

¹ Applied Imaging Science Lab, Department of Radiology, Brigham and Women's Hospital, Boston, MA USA.
² The Ottawa Hospital Research Institute and Medical Imaging, Ottawa, ON Canada.
³ Department of Radiology, University of Ottawa, Ottawa, ON Canada.
⁴ Toshiba Medical Research Institute USA, Vernon Hills, IL USA.
⁵ Department of Radiology, Juntendo University, Tokyo, Japan.
⁶ Department of Radiology, Walter Reed National Military Medical Center, Bethesda, MD USA.
⁷ Division of Musculoskeletal Radiology, Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD USA.
⁸ Department of Radiology, Brigham and Women's Hospital, Boston, MA USA.

Abstract

Background: The effects of reduced radiation dose CT for the generation of maxillofacial bone STL models for 3D printing is currently unknown. Images of two full-face transplantation patients scanned with non-contrast 320-detector row CT were reconstructed at fractions of the acquisition radiation dose using noise simulation software and both filtered back-projection (FBP) and Adaptive Iterative Dose Reduction 3D (AIDR3D). The maxillofacial bone STL model segmented with thresholding from AIDR3D images at 100 % dose was considered the reference. For all other dose/reconstruction method combinations, a "residual STL volume" was calculated as the topologic subtraction of the STL model derived from that dataset from the reference and correlated to radiation dose.

Results: The residual volume decreased with increasing radiation dose and was lower for AIDR3D compared to FBP reconstructions at all doses. As a fraction of the reference STL volume, the residual volume decreased from 2.9 % (20 % dose) to 1.4 % (50 % dose) in patient 1, and from 4.1 % to 1.9 %, respectively in patient 2 for AIDR3D reconstructions. For FBP reconstructions it decreased from 3.3 % (20 % dose) to 1.0 % (100 % dose) in patient 1, and from 5.5 % to 1.6 %, respectively in patient 2. Its morphology resembled a thin shell on the osseous surface with average thickness <0.1 mm.

Conclusion: The residual volume, a topological difference metric of STL models of tissue depicted in DICOM images supports that reduction of CT dose by up to 80 % of the clinical acquisition in conjunction with iterative reconstruction yields maxillofacial bone models accurate for 3D printing.