Embedded bleeding detector into a PMMA applicator for electron intraoperative radiotherapy

Abstract

The aim of this work is to present a ready to industrialize low-cost and easy-to-install bleeding detector for use in intraoperative electron radiation therapy (IOERT). The detector works in stand-alone mode and is embedded into a translucent polymethylmethacrylate (PMMA) applicator avoiding any contact with the patient, which represent a novelty compared to previous designs. The use of this detector will prevent dose misadministration during irradiation in the event of accumulation of fluids in the applicator. Methods: The detector is based on capacitive sensor and wireless power-supply electronics. Both sensor and electronics have been embedded in the applicator, so that any contact with the patient would be avoided. Since access to the tumor can be done through different trajectories, the detector has been calibrated for different tilting angles. Results: The result of the calibration provides us with a fit curve that allows the interpolation of the results at any angle. Comparison of estimated fluid height vs real height gives an error of 1 mm for tilting angles less than 10 • and 2 mm for tilting angles greater than 15 • . This accuracy is better than the one required by clinic. Conclusions: The performance of the bleeding detector was evaluated in situ. No interference was observed between the detector and the beam. In addition, a user-friendly mobile application has been developed to help the surgical team making decisions before and during irradiation. The measurement provided by the mobile application was stable during the irradiation process.

Calibration and validation of a bleeding detector for beveled PMMA applicators in electron intraoperative radiotherapy

“…The deviations in height estimation could be reduced by obtaining sensitivity as a function of inclination and orientation, as was done by García-Gil et al [20] for flat applicators, but this would be a more complex process in the case of bPMMA applicators and may not be viable. Moreover, such a complex process is not necessary for clinical purposes, as the main objective is to detect a fluid level greater than 5 mm.…”

“…The LIAC HWL Mobile linac [20,22] offers electron energies at 6, 8, 10, and 12 MeV. To enable direct visualization of the tumor bed, PMMA applicators are used.…”

“…The use of detectors to measure the presence of fluid in a recipient is common in fields such as in industrial, medical or environmental monitoring applications [10][11][12][13]. Although bleeding detectors for medical applications can be found in the literature [14][15][16][17], the problem of real-time bleeding detection in IOERT treatments has only been found in [18][19][20]. Bleeding detectors described in [14][15][16][17] basically perform the detection through image processing [14][15][16] or augmented reality and processing through artificial intelligence [17].…”

“…The detector incorporates a mobile application that allows the surgical team to verify the presence of accumulated fluid in the applicator both before and during the irradiation process. The solution proposed by García-Gil et al [20] for fPMMA applicators meets all clinical requirements: 5 mm detection capability, high visibility, no patient contact, linac independence, no interference with the irradiation beam and easy-touse. Nevertheless, the bleeding detection solution for bPMMA applicators has not yet been solved, despite these being the most widely used clinically.…”

Eines computacionals avançades per a planificació radioterapèutica mitjançat simulacions Monte Carlo

“…Aquestes van consistir en tres irradiacions de 300 unitats monitor, en un maniquí d'aigua sòlida en cada cas. Les mesures de taxa de dosi màxima, es van realitzar a 3 m de distància amb un INOVION 451 (Fluke Biomedical, EUA), una configuració que ja s'havia emprat en treball previs [144]. A partir de les mesures, es va obtenir el quocient de la mitjana de la mesura de taxa de dosi màxima entre ambdós aplicadors, amb una incertesa estadística inferior al 2%.…”