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3D printed ultrasound phantoms for clinical training

Authors:
3D printed ultrasound phantoms for clinical training
James Robertson,1* Emma Hill,1 Andrew A. Plumb,2 Simon Choong,3 Simeon J. West,3 Daniil I. Nikitichev1
1 Department of Medical Physics and Biomedical Engineering, University College London.
London, Gower Street, WC1E 6BT, London, United Kingdom.
2 Centre for Medical Imaging, University College London, London, United Kingdom
3 University College Hospital, 235 Euston Road, NW1 2BU, London, United Kingdom.
E-mail:
james.robertson.10@ucl.ac.uk and emma.hill.14@ucl.ac.uk
Internet: http://www.ucl.ac.uk/medphys
Ultrasound is a ubiquitous, portable structural imaging technique used to provide visual
feedback for a heterogeneous range of diagnostic and surgical techniques[1]. Preparatory training
for these techniques therefore demands a range of teaching models tailored for each application.
Existing anatomical models are often overly simple or prohibitively expensive, causing difficulties in
obtaining patient or procedure specific models. In this study we present ultrasound phantoms for
clinical teaching and training purposes, fabricated by extruding and photopolymerization three-
dimensional (3D) printing technologies.
3D printing is increasingly used in medicine, neuroscience and biotechnology due to its
affordability and the ability to create complex anatomical geometries[2]. 3D printed imaging
phantoms have been successfully demonstrated in the past but they were relatively simple[3][4]. In
order to create patient-specific models from medical image data, image-processing software is
required. In recent years, a number of image-processing methods have been developed that allow
the rapid generation of anatomically accurate 3D models from population or patient specific
data[5][6]. There is a growing interest in the application of these techniques in a clinical context for
the creation of anatomically accurate 3D printed models from medical images for therapeutic,
research and teaching applications [7-9].
For this study, clinical partners identified a requirement for practical rib and kidney imaging
phantoms for use in surgical teaching and planning of complex cases. We produced a series of
high quality 3D printed functional models of selected sets of ribs and a partial kidney model
suitable for use in clinical training for ultrasound guided therapy and diagnostics. Clinical partners
advised on specific design considerations for these models.
To produce these models, X-Ray CT data were segmented to extract volumes of interest. These
segmentations were transferred to MeshMixer software for refinement, before being exported as
stereolithography (STL) files for 3D printing software (Figure. 1.a). A rib models was printed in
enhanced PLA extruding material using an Ultimaker printer (Ultimaker, UK) while a kidney model
was fabricated in digital material (DM9860, Stratasys) using a polyjet Objet printer (Stratasys, UK)
(Figure 1.b,c). These models were combined in an ultrasound imaging phantom (Figure 1.c).
The ultrasonic profiles of the imagining phantom were obtained and compared with pre-existing
ultrasound images of the areas and organs of interest. These images were used to gauge
suitability of the phantom for teaching and surgical planning, and to determine the optimal 3D
printing material for use in realistic phantom production. Following review the final model design
will be of use to clinicians and educators for medical training purposes as the final STL files can be
easily shared between centres. Furthermore, the optimised production technique will be of interest
for anyone wishing to design a similar phantom for alternative medical applications.
Figure 1. a) Medial view of completed rib mesh in MeshMixer environment following segmentation
in Seg3D b) Completed 3D print of Rib model in Polylactic Acid (PLA) on Ultimaker 2 3D printer c)
Reduced scaled rib phantom with partial kidney phantom in fluid bath (insert: detail of kidney
phantom) d) Ultrasound scan of human rib
in-situ
, with reflection and shadowing from the rib
highlighted e) Ultrasound scan of imaging phantom showing shadowing and reflections from rib
and kidney phantoms.
Keywords
Ultrasound phantom, clinical training, image processing
Biography
James Robertson obtained an undergraduate degree in Biomedical Science with Medical Physics
from University College London in 2013 in part completion of an MBBS in Medicine (on hiatus). He
is currently reading for a PhD in Medical Physics at the Biomedical Ultrasound Group of the Dept.
of Medical Physics and Biomedical Engineering of UCL, under Dr Bradley Treeby. His research is
based on the use of numerical simulation of ultrasound for the transcranial focusing of ultrasonic
therapy, and includes the creation and validation of multiple ultrasonic bone phantoms.
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Shiroki, K. Hoshinaga,
Transplant. Proc.
2015, 47, 596.
... The ribs phantom was used as an ultrasound imaging phantom for clinical training. By embedding the ribs into a mineral-oil based material (Mindsets, Waltham Cross, United Kingdom) to simulate surrounding musculature and soft tissues, and combining these with a chicken breast and an 18 gauge puncture needle, it was possible to perform a low-cost mock kidney fine needle aspiration (FNA) procedure (Fig 3) [31]. In Fig 3B, the reflection of part of the ribs phantom can be seen in the top right corner. ...
... It was possible to create the segmented structures with high detail, allowing them to be used as teaching models. Furthermore, the printed model of the ribs was found to be functionally close to a real rib cage when imaged by an ultrasound scanner [31]. ...
Article
Full-text available
Anatomical models are important training and teaching tools in the clinical environment and are routinely used in medical imaging research. Advances in segmentation algorithms and increased availability of three-dimensional (3D) printers have made it possible to create cost-efficient patient-specific models without expert knowledge. We introduce a general workflow that can be used to convert volumetric medical imaging data (as generated by Computer Tomography (CT)) to 3D printed physical models. This process is broken up into three steps: image segmentation, mesh refinement and 3D printing. To lower the barrier to entry and provide the best options when aiming to 3D print an anatomical model from medical images, we provide an overview of relevant free and open-source image segmentation tools as well as 3D printing technologies. We demonstrate the utility of this streamlined workflow by creating models of ribs, liver, and lung using a Fused Deposition Modelling 3D printer.
... The use of products derived from 3D mesh models and computer aided design (CAD) techniques in healthcare is rapidly growing. Applications include: planning surgical procedures for hepatic & renal cancer resection; innovative cardiac and vascular device testing for paediatric and adult populations; visualisation of complex head and neck anatomy for neurosurgeons; practicing procedures ex vivo; training models and educating clinicians and patients [9][10][11][12][13]. Models of heart [2], renal collecting system [14], kidney [15] and brain [16,17] have been previously developed. ...
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Background: Ultrasonic assessment of optic nerve sheath diameter (ONSD) as a non-invasive measure of intracranial pressure (ICP) has been evaluated in the literature as a potential valid technique for rapid ICP estimation in the absence of invasive intracranial monitoring. The technique can be challenging to perform and little literature exists surrounding intra-operator variability. Objectives: In this study we describe the creation of a novel model of ONSD to be utilized in ultrasound training of this technique. We demonstrate the realistic ultrasonographic images created utilizing this novel model. Methods: We designed ocular models composed of gelatin spheres and variable three dimensional printed cylinders, which simulate the globe of the eye and variable ONSD's respectively. These models were suspended in a gelatin background and ultrasound of the ONSD was conducted using standard techniques described in the literature. Results: This model produces clear and accurate representation of ONSD that closely mimics in vivo images. It is affordable and easy to produce in large quantities, portending its use in an educational environment. Conclusions: Utilizing the standard linear array ultrasound probe for ONSD measurements in our model provided realistic images comparable to in vivo. This provides an affordable and exciting means to test intra- and inter- operator variability in a standardized environment. Knowing this, we can further apply this novel model of ONSD to ultrasound teaching and training courses with confidence in its ability and the technique's ability to produce consistent results.
  • D I Nikitichev
  • A Barburas
  • K Mcpherson
  • S J West
  • J M Mari
  • A E Desjardins
  • A Fedorov
  • R Beichel
  • J Kalpathy-Cramer
  • J Finet
D. I. Nikitichev, A. Barburas, K. McPherson, S. J. West, J. M. Mari, and A. E. Desjardins, Ultrasound Med. Biol., 2015, in press. [5] CIBC, "http://seg3d.org" 2015. [6] A. Fedorov, R. Beichel, J. Kalpathy-Cramer, J. Finet, J-C. Fillion-Robin, S. Pujol, C. Bauer, D. Jennings, F. Fennessy, M. Sonka, J. Buatti, S. R. Aylward, J. V. Miller, S. Pieper, R. Kikinis, Magn. Reson. Imaging 2012, 30, 9.
  • D I Nikitichev
  • A Barburas
  • K Mcpherson
  • S J West
  • J M Mari
  • A E Desjardins
D. I. Nikitichev, A. Barburas, K. McPherson, S. J. West, J. M. Mari, and A. E. Desjardins, Ultrasound Med. Biol., 2015, in press.
  • A Fedorov
  • R Beichel
  • J Kalpathy-Cramer
  • J Finet
  • J -C. Fillion-Robin
  • S Pujol
  • C Bauer
  • D Jennings
  • F Fennessy
  • M Sonka
  • J Buatti
  • S R Aylward
  • J V Miller
  • S Pieper
  • R Kikinis
A. Fedorov, R. Beichel, J. Kalpathy-Cramer, J. Finet, J-C. Fillion-Robin, S. Pujol, C. Bauer, D. Jennings, F. Fennessy, M. Sonka, J. Buatti, S. R. Aylward, J. V. Miller, S. Pieper, R. Kikinis, Magn. Reson. Imaging 2012, 30, 9.
  • R Partridge
  • N Conlisk
  • J A Davies
R. Partridge, N. Conlisk, J. A. Davies, Organogenesis 2014, 8, 22.
  • B W Turney
B. W. Turney, J. Endourol. 2014, 28, 360.
  • M Kusaka
  • M Sugimoto
  • N Fukami
  • H Sasaki
  • M Takenaka
  • T Anraku
  • T Ito
  • T Kenmochi
  • R Shiroki
  • K Hoshinaga
M. Kusaka, M. Sugimoto, N. Fukami, H. Sasaki, M. Takenaka, T. Anraku, T. Ito, T. Kenmochi, R. Shiroki, K. Hoshinaga, Transplant. Proc. 2015, 47, 596.