In last decades 3D printing has had rapid developments in medicine, especially in orthopedy and dentistry, where it is used as surgical guide for implantation with an improvement of treatment outcomes. Thus, the purpose of this work is to propose a cardiac surgical guide as improved solution for ischemic scar treatment, reducing the medical procedure timing, and enhancing the treatment. The work is done at the cardiology department of UZ Brussel Hospital in Bruxelles, under the guidance of Prof. Marco Mandolini, Prof. Bernardo Innocenti and Prof. Carlo de Asmundis. The treatment of ischemic scar in patients with post myocardial infarction (MI) is clinically important because it leads to malignant arrhythmias, like ventricular tachycardia (VT), which represent a common cause of morbidity and mortality. Because of MI, the border zone between scarred and normal myocardium is the predominant substrate for the majority of VT post-MI. Nowadays, the treatment consists of a long iterative method, which alternes heart electrical activity mapping and ablation procedure until the sinus rhythm is restored. The concept of surgical guide for ischemic scar treatment derived from the need to have a precise visualization of pathological area to make sure to assess the necrotic extent of ablation lesions because an incomplete ablation of arrhythmogenic substrate allows subsequent recovery of tissue with restoration of arrhythmias. To build a surgical guide to indicate directly on the heart the target area to be treated by ablation procedure, it is necessary to consider surgeon’s and engineer’s requirements in terms of biocompatibility, efficiency, temperature resistance, manufacturing time and cost. For the model realization, computed tomography (CT) and cardiac magnetic resonance (CMR) images are processed in 3D Slicer Software to extract anatomical structure and pathological information, and then, the models are merged in Meshmixer Software to realize the 3D virtual model. The material selection is crucial: it depends on surgical guide action, and 3D printer, considering workspace and surgical procedures associated to, such as packaging and sterilization through Vaporized Hydrogen Peroxide Gas (VHP). The second part of this work is focused on demonstrating the product functionality and feasibility, thought conducting of the geometry and thermal tests. The geometry test has demonstrated that the VHP sterilization does not affect either geometric structure (about a millimeter) and mechanical properties. Though the overcomes of nondestructive tests have demonstrated that safe conditions (below 40-45°C during RF and LRF and, above -40°C during cryoablation) are guaranteed in all trials, except for T1 at 0 s during RF, which warms the guide material, leading to cell damaging. Thus, it is recommended to not be in contact with the surgical mask and maintain at least 1 mm of distance from the mask during ablation. Instead, through the comparison between samples before and after ablation procedures, it is possible to appreciate that all samples have not any visible changes. Finally, the simulation test on porcine heart has demonstrated the surgical mask functionality and the easy application: during LRF procedure, the ablator acts within the surgical mask target area, creating a visible grey lesion which precisely follows the guide perimeter with tolerances in the order of millimeter, considered acceptable. In conclusion, work findings indicate that the 3D surgical guide is a reliable technology that contributes to more precise and rapid treatment of ischemic scar post MI, but a medical support for identification of target area to treat from diagnostic images is still essential. Further studies are needed to make a trustworthy evaluation of position accuracy and to demonstrate the efficiency in terms of time and quality for the ischemic scar ablation treatment.
Negli ultimi decenni la stampa 3D ha subito rapidi sviluppi in diversi campi della medicina, in particolare in ortopedia e in ortodonzia, in cui sono state sviluppate guide chirurgiche per migliorare l’impianto di protesi. Per questo motivo, lo scopo di questo progetto è di proporre una guida chirurgica in ambito cardiologico, per il trattamento di cicatrici ischemiche, minimizzando i tempi della procedura operatoria e migliorandone i risultati. L’intero lavoro è stato svolto a Bruxelles, presso il reparto di cardiologia dell’ospedale UZ Brussel, sotto la supervisione dei professori Marco Mandolini, Bernardo Innocenti e Carlo de Asmundis. Il trattamento delle cicatrici ischemiche in pazienti affetti da infarto miocardico è di cruciale importanza perché porta ad aritmie cardiache, quali tachicardie ventricolari, che rappresentano una delle più comuni cause di mortalità. In seguito ad un infarto, la zona compresa tra il tessuto cardiaco totalmente danneggiato e quello sano è considerata la zona da trattare. Attualmente, il trattamento consiste in un processo iterativo che alterna il mappaggio dell’attività elettrica cardiaca e il trattamento di ablazione di piccole zone finché non viene restaurato il ritmo sinusale. Il concetto di guida chirurgica per il trattamento di questa patologia, deriva del bisogno di avere una precisa visualizzazione dell’area patologica che permetta un rapido accesso alla zona da trattare, affinché l’aritmia venga risolta senza rischio di ricadute. Per costruire una guida che indichi direttamente sulla superficie cardiaca la zona da trattare, è necessario tenere in considerazione diversi requisiti quali la biocompatibilità, la stabilità, la resistenza alla temperatura, i tempi e i costi di realizzazione. Per la realizzazione del modello, le immagini della TC e della RM sono state processate attraverso il Software 3D Slicer per l’estrazione della struttura anatomica e della patologia. Successivamente, i modelli ottenuti sono stati sovrapposti attraverso il software Meshmixer, ottenendo il modello 3D virtuale. Di cruciale importanza è stata la scelta del materiale, il quale deve essere funzionale al trattamento, compatibile con il tipo di stampante 3D, considerando lo spazio di lavoro, e le procedure associate, tra cui la sterilizzazione attraverso il Perossido di Idrogeno e l’impacchettamento, per il mantenimento delle condizioni sterili fino alla sala operatoria. La seconda parte del progetto è incentrata a dimostrare la fattibilità e la funzionalità del prodotto, attraverso test termici e sulla geometria. I risultati dei test hanno dimostrato che la guida chirurgica ha risposto positivamente alla maggior parte delle prove a cui è stata sottoposta: la sterilizzazione VHP non ha avuto effetti né sulla struttura né sulle proprietà meccaniche del materiale. Il materiale ha dimostrato di poter garantire le condizioni di sicurezza quando sottoposto all’ablazione, tranne nella prova di RF, in cui il materiale si surriscalda, portando ad una temperatura di +50°C il tessuto sottostante sano, danneggiandolo. Pertanto, si raccomanda di mantenere lo strumento di ablazione ad una distanza di 1 mm. Al termine dei test termici, i campioni di materiale sono stati paragonati e non è stato rilevato alcun cambiamento. Inoltre, il test di simulazione sul cuore di maiale ha confermato la rapida modalità di applicazione e la funzionalità della guida: l’effetto dell’ablatore sul tessuto cardiaco segue fedelmente il perimetro della zona target indicata dalla guida. In conclusione, i risultati ottenuti indicano che la guida chirurgica stampata 3D è un’affidabile tecnologia che potrebbe contribuire ad un trattamento più preciso delle cicatrici ischemiche riducendo i tempi della procedura. Ulteriori studi sono necessari per valutarne l’accuratezza e l’efficienza, specifica per ogni paziente.
Use of 3D printing technology as heart surgical guide in ischemic scar ablation treatment: a feasibility study
CANDELARI, MARA
2020/2021
Abstract
In last decades 3D printing has had rapid developments in medicine, especially in orthopedy and dentistry, where it is used as surgical guide for implantation with an improvement of treatment outcomes. Thus, the purpose of this work is to propose a cardiac surgical guide as improved solution for ischemic scar treatment, reducing the medical procedure timing, and enhancing the treatment. The work is done at the cardiology department of UZ Brussel Hospital in Bruxelles, under the guidance of Prof. Marco Mandolini, Prof. Bernardo Innocenti and Prof. Carlo de Asmundis. The treatment of ischemic scar in patients with post myocardial infarction (MI) is clinically important because it leads to malignant arrhythmias, like ventricular tachycardia (VT), which represent a common cause of morbidity and mortality. Because of MI, the border zone between scarred and normal myocardium is the predominant substrate for the majority of VT post-MI. Nowadays, the treatment consists of a long iterative method, which alternes heart electrical activity mapping and ablation procedure until the sinus rhythm is restored. The concept of surgical guide for ischemic scar treatment derived from the need to have a precise visualization of pathological area to make sure to assess the necrotic extent of ablation lesions because an incomplete ablation of arrhythmogenic substrate allows subsequent recovery of tissue with restoration of arrhythmias. To build a surgical guide to indicate directly on the heart the target area to be treated by ablation procedure, it is necessary to consider surgeon’s and engineer’s requirements in terms of biocompatibility, efficiency, temperature resistance, manufacturing time and cost. For the model realization, computed tomography (CT) and cardiac magnetic resonance (CMR) images are processed in 3D Slicer Software to extract anatomical structure and pathological information, and then, the models are merged in Meshmixer Software to realize the 3D virtual model. The material selection is crucial: it depends on surgical guide action, and 3D printer, considering workspace and surgical procedures associated to, such as packaging and sterilization through Vaporized Hydrogen Peroxide Gas (VHP). The second part of this work is focused on demonstrating the product functionality and feasibility, thought conducting of the geometry and thermal tests. The geometry test has demonstrated that the VHP sterilization does not affect either geometric structure (about a millimeter) and mechanical properties. Though the overcomes of nondestructive tests have demonstrated that safe conditions (below 40-45°C during RF and LRF and, above -40°C during cryoablation) are guaranteed in all trials, except for T1 at 0 s during RF, which warms the guide material, leading to cell damaging. Thus, it is recommended to not be in contact with the surgical mask and maintain at least 1 mm of distance from the mask during ablation. Instead, through the comparison between samples before and after ablation procedures, it is possible to appreciate that all samples have not any visible changes. Finally, the simulation test on porcine heart has demonstrated the surgical mask functionality and the easy application: during LRF procedure, the ablator acts within the surgical mask target area, creating a visible grey lesion which precisely follows the guide perimeter with tolerances in the order of millimeter, considered acceptable. In conclusion, work findings indicate that the 3D surgical guide is a reliable technology that contributes to more precise and rapid treatment of ischemic scar post MI, but a medical support for identification of target area to treat from diagnostic images is still essential. Further studies are needed to make a trustworthy evaluation of position accuracy and to demonstrate the efficiency in terms of time and quality for the ischemic scar ablation treatment.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12075/1270