Using 3D anthropometric data for the modelling of customised head immobilisation masks

ABSTRACT

Head immobilization thermoplastic masks for radiotherapy purposes involve a distressful modelling procedure for the patient. To assess the possibility of using different acquisition and reconstruction methods to obtain a 3Dskin surface model of PIXY-phantom-head and to present a proposal of an alternative head immobilisation mask prototype. Phantom head geometry acquisitions using: computed tomography (reconstructed with ImageJ and Osirix); and 3DLaserScanner (reconstructed with SolidWorks). From these reconstructed surface models a set of landmarks was measured and subsequently compared with physical measurements obtained with a Rosscraft-Calliper. For statistical evaluation, relative deviations graphics and Friedman-test for non-parametrical paired samples were used, with a significance level of 5%. For a first assessment of the proposed mask performance, a radiotransparent material was considered, the strength and stiffness evaluation being performed using the finite element method. There are small differences between all the acquisitions and reconstructions methods and the physical measurements, statistically significant differences (X2F(6)) = 6.863, p=0.334) were not found. The proposed mask performed well from the strength and stiffness perspectives, leading to the desired immobilisation aim. The immobilisation mask design proposal may be an effective alternative to the present completely hand-made situation, which presents a high-degree of discomfort and stress to the patients.

KEYWORDS:

• 3D surfaces scanning
• computed tomography
• computational modelling of head surface
• immobilisation mask prototype
• mask’ mechanical behaviour

Acknowledgements

The authors wish to acknowledge the financial support of Project IPL/2016/SoftImob/ISEL, IPL/2016/CardiaCor_ESTeSL and Project LAETA—UID/EMS/50022/2019. The authors also wish to acknowledge Fundação Champalimaud for the possibility of obtaining the CT images which were essential to this study.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors wish to acknowledge the financial support of Project IPL/2016/SoftImob/ISEL, IPL/2016/CardiaCor_ESTeSL and Project LAETA—UID/EMS/50022/2019.

Notes on contributors

MAR Loja

MAR Loja is with GIMOSM, ISEL/IPL, Grupo de Investigação em Modelação e Optimização de Sistemas Multifuncionais, and with LAETA, IDMEC, Instituto Superior Técnico. Her academic background integrates PhD in Mechanical Engineering. Her research interests are related to the areas of Computational Mechanics of Solids, Optimization and Reverse Engineering.

E Sousa

E Sousa is with GI-MOSM, ISEL/IPL, Grupo de Investigação em Modelação e Optimização de Sistemas Multifuncionais and, H&TRC – Health &Technology Research Center, ESTeSL/IPL - Escola Superior de Tecnologia da Saúde de Lisboa/Instituto Politécnico de Lisboa. Her academic background integrates MSc in Biomedical and Biophysical Engineering. Her research interests are related to the areas of Medical Image and Radioteraphy.

L Vieira

L Vieira is with GI-MOSM, ISEL/IPL, Grupo de Investigação em Modelação e Optimização de Sistemas Multifuncionais, H&TRC – Health &Technology Research Center, ESTeSL/IPL - Escola Superior de Tecnologia da Saúde de Lisboa/Instituto Politécnico de Lisboa and, Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal. Her academic background integrates PhD in Biomedical and Biophysical Engineering. Her research interests are related to the areas of Medical Image and Radioteraphy.

DMS Costa

DMS Costa is with GIMOSM, ISEL/IPL, Grupo de Investigação em Modelação e Optimização de Sistemas Multifuncionais. His academic background integrates a MSc in Mechanical Engineering. His research interests are related to the areas of Smart Structures, FEA, Multifunctional Materials and Optimization.

R Parafita

R Parafita, Medical Physicist of Nuclear Medicine-Radiopharmacology, Champalimaud Centre for the Unknown, Champalimaud Foundation, MSc in Physics Engineering, Interests in Medical Image and Radiation Protection

DC Costa

DC Costa, Director of Nuclear Medicine-Radiopharmacology, Champalimaud Centre for the Unknown, Champalimaud Foundation; Nuclear Medicine Physician; MSc and PhD by the University of London, UK; Fellow of the Royal College of Radiologists, London, UK; Emeritus Reader, University College London, London, UK; past-President of UEMS-EBNM (from 2012 to 2015).