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- Radiotherapy-customized head immobilization masks: from modeling and analysis to 3D printingPublication . Loja, Amélia; Craveiro, D. S.; Vieira, Lina Oliveira; Sousa, Eva; Rodrigues, J. A.; Portal, R. J. F.Immobilization devices may be a valuable aid to ensure the improved effectiveness of radiotherapy treatments where constraining the movements of specific anatomical segments is crucial. This need is also present in other situations, specifically when the superposition of various medical images is required for fine identification and characterization of some pathologies. Because of their structural characteristics, existing head immobilization systems may be claustrophobic and very uncomfortable for patients, during both the modeling and usage stages. Because of this, it is important to minimize all the discomforts related to the mask to alleviate patients’ distress and to simultaneously guarantee and maximize the restraint effectiveness of the mask. In the present work, various head immobilization mask models are proposed based on geometrical information extracted from computerized tomography images and from 3D laser scanning point clouds. These models also consider the corresponding connection to a radiotherapy table, as this connection is easily altered to accommodate various manufacturers’ solutions. A set of materials used in the radiotherapy field is considered to allow the assessment of the stiffness and strength of the masks when submitted to typical loadings.
- Using 3D anthropometric data for the modelling of customised head immobilisation masksPublication . Loja, Amélia; Sousa, E.; Vieira, Lina Oliveira; Craveiro, D.S.; Parafita, Rui; C. Costa, Durval; Costa, DMSHead 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.
- Developments on finite element methods for medical image supported diagnosticsPublication . Almeida, Ana; Barbosa, Joaquim; Carvalho, André; Loja, Amélia; Portal, Ricardo; Rodrigues, José Alberto; Vieira, Lina OliveiraVariational image-processing models offer high-quality processing capabilities for imaging. They have been widely developed and used in the last two decades, enriching the fields of mathematics as well as information science. Mathematically, several tools are needed: energy optimization, regularization, partial differential equations, level set functions, and numerical algorithms. For this work we consider a second-order variational model for solving medical image problems. The aim is to obtain as far as possible fine features of the initial image and identify medical pathologies. The approach consists of constructing a regularized functional and to locally analyse the obtained solution. Some parameters selection is performed at the discrete level in the framework of the finite element method. We present several numerical simulations to test the efficiency of the proposed approach.
- An optimization strategy for customized radiotherapy head immobilization masksPublication . Craveiro, D.S.; Loja, Amélia; Vieira, Lina Oliveira; Vinyas, M.An effective head immobilization is an important requirement in radiotherapy treatment sessions, although it may also be thought in the future as a precious aid in brain medical imaging. Thus, the present work is focused on the stiffness optimization of a customized head immobilization mask, modelled upon the head reconstruction surface based on computerized tomography images. This paper proposes a strategy supported by a metaheuristic optimization technique and a metamodeling approach for the whole mask, illustrated at its most unfavorable region occurring in the gnathion region.