Research Article: Patient-specific neurosurgical phantom: assessment of visual quality, accuracy, and scaling effects

Date Published: March 13, 2018

Publisher: Springer International Publishing

Author(s): Felipe Wilker Grillo, Victor Hugo Souza, Renan Hiroshi Matsuda, Carlo Rondinoni, Theo Zeferino Pavan, Oswaldo Baffa, Helio Rubens Machado, Antonio Adilton Oliveira Carneiro.

http://doi.org/10.1186/s41205-018-0025-8

Abstract

Training in medical education depends on the availability of standardized materials that can reliably mimic the human anatomy and physiology. One alternative to using cadavers or animal bodies is to employ phantoms or mimicking devices. Styrene-ethylene/butylene-styrene (SEBS) gels are biologically inert and present tunable properties, including mechanical properties that resemble the soft tissue. Therefore, SEBS is an alternative to develop a patient-specific phantom, that provides real visual and morphological experience during simulation-based neurosurgical training.

A 3D model was reconstructed and printed based on patient-specific magnetic resonance images. The fused deposition of polyactic acid (PLA) filament and selective laser sintering of polyamid were used for 3D printing. Silicone and SEBS materials were employed to mimic soft tissues. A neuronavigation protocol was performed on the 3D-printed models scaled to three different sizes, 100%, 50%, and 25% of the original dimensions. A neurosurgery team (17 individuals) evaluated the phantom realism as “very good” and “perfect” in 49% and 31% of the cases, respectively, and rated phantom utility as “very good” and “perfect” in 61% and 32% of the cases, respectively. Models in original size (100%) and scaled to 50% provided a quantitative and realistic visual analysis of the patient’s cortical anatomy without distortion. However, reduction to one quarter of the original size (25%) hindered visualization of surface details and identification of anatomical landmarks.

A patient-specific phantom was developed with anatomically and spatially accurate shapes, that can be used as an alternative for surgical planning. Printed models scaled to sizes that avoided quality loss might save time and reduce medical training costs.

Partial Text

Medical error can be defined as acts of commission or omission that have the potential to harm or that effectively harm patients [1]. A study has revealed that technical errors, such as problems in equipment use or in the performance of a procedure, cause 27.8% of these events [2, 3]. The image-guided navigation (IGN) systems have been employed to assist surgeons during complex surgical procedures [4] that require extreme manual and visual abilities. IGN allows real-time surgical tool localization through co-registration of the patient’s body and tomographic images, such as computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound imaging (US) [5]. Neuronavigation systems are IGN systems dedicated to help surgeons during neurosurgeries to locate a tool in a three dimensional (3D) space while moving it around or inside the patient’s head [6]. Mastering the use of navigation systems requires extensive training in a controlled environment to allow accurate and precise measurements.

In an attempt to minimize medical errors, the simulation of medical procedures has become a common approach in medical training. In this scenario, simulating the specific characteristics of a patient constitutes a challenge [9]. The use of negative molds is a well-known method to reproduce morphology [32, 33]. However, it is impossible to copy internal structures or organs for in-vivo studies of human cases. The use of 3D printers enables the development of realistic phantoms with anatomically and spatially accurate shapes [34]. Previous studies have reported the use of 3D printing to reproduce the patient’s anatomy for surgical and treatment planning and to facilitate understanding of the normal and pathologic anatomy of individual patients in different situations, such as aneurysm [35, 36]. Weinstock et al. used 3D printing and silicone molding and relied on the aid of Hollywood special effects technicians, who finished the model with makeup, to improve realism [37]. Therefore, the combination of 3D printing and molding technique helps to accelerate object manufacture [37]. Compared to 3D printing, in this study the silicone molds enabled faster production of multiple copies with the same details and even allowed the preparation of materials that are not yet available for 3D printing. We also verified that the soft tissue-mimicking material SEBS bore a striking resemblance to the patient’s brain cortex anatomy and enabled haptic feedback for surgical procedures. Further development should allow mimicking of internal brain structures and dynamic functions, such as blood circulation.

A patient-specific (Sturge Weber case) phantom was successfully created by using 3D printing techniques and molds that included a soft tissue mimicking material for the brain structure, meninx and skull. Our study revealed that 3D printing and SEBS are promising tools to develop a patient-specific phantom as a teaching tool, providing tissue mimicking material and reliable anatomical morphology. Moreover, the molding technique enabled the performance of fast copies for a single case, which confirmed the didactic potential of the presented models. The use of multiscale models is a successful alternative to improve time and to simulate the general steps of surgical procedures.

 

Source:

http://doi.org/10.1186/s41205-018-0025-8

 

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