Catalog of Regulatory Science Tools to Help Assess New Medical Devices
This regulatory science tool presents a set of phantoms that provide digital models of human retina vasculature, based on images acquired with a fundus camera.
Technical Description
The vascular map deviates from the original geometry in that it is essentially planar and has been modified to provide circular channels with equal diameter throughout the volume. Three versions are included which incorporate: (a) a single vascular network (b) two vascular networks at different depths and rotated 90o and (c) a single vascular network that is tilted with respect to the surface so that the vessels vary in depth. The full dimensions are also nominally 45 x 45 x 13 mm but can be modified. These models can be implemented for 3D printing of tissue-simulating phantoms for a range of biophotonic imaging modalities, as noted above. The size of any printed model is dependent on the printer used as well as any preprocessing of the file.
This tool is described in an initial peer-reviewed journal article on hyperspectral imagingExternal Link Disclaimer [1]. Additional implementations can be found in articles on fluorescence imagingExternal Link Disclaimer [2] and confocal microscopyExternal Link Disclaimer [3]. The digital (STL) files are available on the NIH 3D Print Exchange.
Intended Purpose
This tool was developed to facilitate fabrication of phantom-based performance test methods for biophotonic imaging applications, such as hyperspectral and fluorescence imaging. The system could be used to evaluate accuracy in estimating blood oxygen saturation, or performance in imaging fluorophore-containing vasculature (e.g., indocyanine green). Specific product areas or product codes: MUD, OWN.
There are several ways in which this tool can facilitate product development and regulatory evaluation. When filled with a liquid (e.g., fluorophore solution, blood, or hemoglobin solution), the phantom can be used to evaluate and/or compare the performance of imaging systems, either subjectively or using objective metrics such as the signal intensity (or signal to noise ratio) and diameter (e.g., full-width-halfmaximum) of specific channels in the structure. Printed phantoms could be useful as a target for researchers developing/optimizing new imaging systems to evaluate the impact of changes in system design. Alternately, such models could be used to compare the performance of a single imaging system using fluorophores with different spectral characteristics. The models could also be used for constancy testing over time during clinical use (or clinical study) of an imaging system, or as basic training tools for clinicians.
The intended tool user population is primarily biophotonics researchers, device developers, medical technologists, although the models may be useful for clinicians as well.
Training in viewing/editing and 3D printing digital files is recommended to generate high quality phantoms from these files.
Testing
Validation of the optical properties and morphology of 3D printed phantoms based on the digital files described here is presented in a prior journal articleExternal Link Disclaimer [1]. Demonstration of the use of these files in fabricating tissue-simulating phantoms capable of being imaged by hyperspectral and fluorescence imaging systems is also provided in the aforementioned journal articles.
This tool has been leveraged for phantom fabrication in a research study by Lv et al.External Link Disclaimer [4].
Limitations
The files provided only represent useful geometric maps; the quality of actual tissue phantoms generated with these files is directly related to the optical properties of the materials used in 3D printing and material used to fill the channels. The designs provided do not enable generation of the range of standard image quality performance characteristics commonly recommended for evaluating imaging system performance (e.g., spatial resolution, depth of field, distortion, sensitivity/detectability).
Supporting Documentation
The links provided below include supporting documentation that provides information regarding how to generate useful phantoms and demonstrates their implementation on specific imaging systems.
Ghassemi, P., Wang, J., Melchiorri, A. J., Ramella-Roman, J. C., Mathews, S. A., Coburn, J. C., Sorg, B. S., Chen, Y., & Pfefer, T. J. (2015). Rapid prototyping of biomimetic vascular phantoms for hyperspectral reflectance imaging. Journal of biomedical optics, 20(12), 121312. https://doi.org/10.1117/1.JBO.20.12.121312External Link Disclaimer Ghassemi, P., Wang, B., Wang, J., Wang, Q., Chen, Y., & Joshua Pfefer, T. (2017). Evaluation of Mobile Phone Performance for Near-Infrared Fluorescence Imaging. IEEE transactions on bio-medical engineering, 64(7), 1650–1653. https://doi.org/10.1109/TBME.2016.2601014External Link Disclaimer Horng, H., O'Brien, K., Lamont, A., Sochol, R. D., Pfefer, T. J., & Chen, Y. (2021). 3D printed vascular phantoms for high-resolution biophotonic image quality assessment via direct laser writing. Optics letters, 46(8), 1987–1990. https://doi.org/10.1364/OL.412849External Link Disclaimer Lv, X., Chen, H., Liu, G., Shen, S., Wu, Q., Hu, C., Li, J., Dong, E., & Xu, R. X. (2018). Design of a portable phantom device to simulate tissue oxygenation and blood perfusion. Applied optics, 57(14), 3938–3946. https://doi.org/10.1364/AO.57.003938External Link Disclaimer