Hereditary effects were very low in contrast to the fatal cancer risk estimation. According to the results we can discard deterministic effects, unless complications appear in the procedure. Radiation exposure must be optimized. It is necessary that medical staff know the radiological risks associated with the intervention, and inform the patients about them.
Purpose This paper investigates the feasibility of implementing a predictive maintenance program for a multileaf collimator (MLC) based on data collected in trajectory logs (TLs) obtained by conducting a simple daily test, with the aim of minimizing unscheduled downtime. Methods A dynamic field test was designed, and the TLs generated in the course of daily administration in a linear accelerator were collected to evaluate trajectory deviations of the MLC leaves as well as interlocks (COL 420219/20, COL 420207/08) reported by the machine. During this evaluation, we observed that the trajectory deviations of some leaves increased up to a threshold value beyond which certain interlocks began to appear in treatment fields in those leaves. An exponential degradation model was therefore developed to predict this drift and determine each leaf's remaining useful life (RUL). Once the applicability of the model was confirmed, we added a second accelerator equipped with an MLC with the same configuration to validate the model. Results The model was able to predict certain COL 420219/20 interlocks resulting from primary readout/expected position discrepancies and to estimate each leaf's RUL. In total, 11 cases (8 interlocks + 3 potential interlocks avoided due to service interventions [27.3% of the total]) were detected over 7 days in advance, with no false positive results. Scheduling of service interventions several days prior to MLC failure would therefore be possible. When these types of interlocks were not predicted by the model, they were always generated by leaf motor failure. Consequently, intervention time could also be optimized by directly replacing the motor. During the study period, for these types of interlocks, our approach would have reduced downtime from 35.25 to 4.00 h (88.7%) and from 34.75 to 22.83 h (34.3%) for each accelerator, respectively. For COL 420207/08 interlocks, which are generated by primary/secondary readout discrepancies, no correlation with leaf trajectory deviation increases recorded in the TLs was found. Throughout the study period, these types of interlocks requiring service intervention, also mainly for motor replacement, represented a downtime of 9.50 h for the first accelerator (21.2% of total downtime) and by 4.33 h (11.1% of total downtime) for the second accelerator. Conclusion This study demonstrates that by applying a predictive MLC maintenance program based on information collected in TLs, it is possible to predict certain interlocks and therefore schedule preemptive interventions to avoid their occurrence. This could optimize health‐care delivery performance and minimize the loss of treatment sessions.
This paper proposes a method for improving the resolution of the fluence derived from detector array measurement using the information collected in dynalog files. From dynalog information, a file is generated with the actual multileaf collimator (MLC) positions and used as input to the treatment planning system (TPS) to obtain the dynalog-derived fluence and the theoretical response over the detector array. In contrast with the measured response, this theoretical response allows for correction of the dynalog-derived fluence and translation into the reconstructed fluence. This fluence is again introduced into the planning system to verify the treatment using clinical tools. Initially, more than 98% of the points passed the two-dimensional (2D) phantom gamma test (3% local dose - 3 mm) for all of the treatment verifications, but in some dose–volume histogram (DVH) comparisons, we note sensitive differences for the planning target volume (PTV) coverage and for the maximum doses in at-risk organs (up to 3.5%). In dose–distribution evaluations, we found differences of up to 5% in the PTV edges in certain cases due to detector array measurement errors. This work improves the resolution of the fluence derived from detector array measurements based on the treatment information, in contrast with the current commercial proposals based on planned data.
objetivos: El varicocele es una anomalía benigna que se detecta generalmente en pacientes jóvenes, y para cuyo tratamiento existen técnicas quirúrgicas. La embolización endovascular es un procedimiento terapéutico alternativo mínimamente invasivo, pero con un riesgo radiológico asociado que resulta esencial conocer para valorar el método de tratamiento más adecuado. El objetivo del trabajo es determinar niveles locales de dosis recibidas en embolizaciones de varicocele en pacientes pediátricos y minimizarlas, estimando el riesgo radiológico. Material y métodos: El estudio se ha realizado en dos fases; una retrospectiva para 15 embolizaciones en pacientes con edades comprendidas entre 10 y 18 años, sin intervención previa en el método de trabajo, y otra prospectiva para 10 pacientes de 10 a 16 años de edad, utilizando algunas técnicas de reducción de dosis implementadas en el equipo. Se conocía el tiempo de escopia y el valor del producto dosis-área de cada intervención. Además, en la fase prospectiva, se han utilizado dosímetros termoluminescentes para la evaluación de la dosis máxima de entrada en piel, y películas radiográficas para verificar la zona irradiada. Resultados: La dosis efectiva media estimada en el estudio retrospectivo fue de 8.8 mSv. El riesgo total medio de inducción de cáncer fatal en cualquier localización fue un 0.16%, siendo un 0.0007% para los efectos hereditarios. La dosis máxima de entrada en piel fue de 250 mGy, siendo 2 Gy el umbral de dosis para la aparición de efectos deterministas en piel. Para los pacientes del estudio prospectivo, las dosis y el riesgo radiológico se redujeron en más de un 70%. Conclusiones: La estimación de riesgo radiológico estocástico es relativamente elevada comparada con el riesgo de complicaciones severas en las intervenciones quirúrgicas de varicocele, excepto para el caso de efectos hereditarios. Son descartables los efectos de tipo determinista, salvo en complicaciones del procedimiento. La exposición a la radiación debe ser optimizada. Es necesario que los clínicos prescriptores e intervencionistas conozcan los riesgos radiológicos asociados a la intervención e informen a sus pacientes.
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