Low-cost chest paediatric phantom for dose optimisation: construction and validation.

INTRODUCTION AND OBJECTIVES: In order to perform chest dose optimisation studies, the imaging phantom should be adequate for image quality evaluation. Since high-end phantoms are cost prohibitive, there is a need for a low-cost construction method with fairly available tissue substitutes. MATERIALS AND METHODS: Theoretical calculations of radiological characteristics were performed for each of lung, cortical bone and soft tissues in order to choose appropriate substitute, then, cork, P.V.C. (Polyvinyl chloride) and water were chosen, respectively. Validation included, firstly, measuring CT Hounsfield Units (HU) of a real patient's tissues then compared against their corresponding anatomies in the constructed phantom. Secondly, Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values were acquired in this study to evaluate the quality of images generated from the constructed phantom, then, compare their trends with a valid phantom under different exposure parameters (kVp and mAs). RESULTS: From theoretical calculations, the percentage differences showed high accuracy of tissue substitutes when simulating real patient tissues; P.V.C. was ≥5.78%, cork was ≥4.46% and water ≥5%. The percentage difference (CT HU) between lung and cortical bone and their equivalent tissue substitutes were 10.44% and 0.53%-3.17%, respectively. Strong positive correlations were found for SNR when changing both kVp (0.79) and mAs (0.65). While the correlation strength of CNR values were found to be moderate when changing both kVp (0.58) and mAs (0.53). CONCLUSIONS: Our low-cost phantom approved through CT HU that their materials replicate the radiological characteristics of real one-year-old child while SNR and SNR correlations confirmed its applicability in imaging and optimisation studies.

Construcción y validación de un fantoma torácico pediátrico asequible para optimizar la dosis / Low-cost chest paediatric phantom for dose optimisation: construction and validation

Introducción y objetivosPara llevar a cabo estudios de optimización de dosis, el fantoma de imagenología debe ser adecuado para evaluar la calidad de la imagen. El coste de los fantomas de gama alta suele ser prohibitivo, por lo que es necesario hallar un método de construcción asequible que emplee sustitutos tisulares que sean razonablemente fáciles de obtener.Materiales y métodosSe realizaron cálculos teóricos de las características radiológicas de cada uno de los pulmones, el hueso cortical y los tejidos blandos con el fin de elegir el sustituto adecuado; para ello, se eligieron el corcho, el cloruro de polivinilo (PVC) y el agua, respectivamente. La validación consistió, en primer lugar, en la medición de las unidades Hounsfield (UH) de tomografía computarizada (TC) de los tejidos de un paciente real y su posterior comparación con las anatomías correspondientes en el fantoma construido. En segundo lugar, se obtuvieron los valores de relación señal/ruido (S/R) y de relación contraste/ruido (C/R) para evaluar la calidad de las imágenes generadas a partir del fantoma construido y comparar sus tendencias con un fantoma válido utilizando diferentes parámetros de exposición (valores pico de kilovoltaje [kVp] y miliamperios por segundo [mAs]).ResultadosPartiendo de los cálculos teóricos, las diferencias porcentuales exhibieron una precisión elevada en los sustitutos tisulares al simular los tejidos de un paciente real; con PVC fue de ≥ 5,78%, con corcho ≥ 4,46% y con agua ≥ 5%. La diferencia porcentual (UH de TC) entre el pulmón y el hueso cortical y sus sustitutos tisulares equivalentes fue de 10,44% y de 0,53 a 3,17%, respectivamente. Se encontraron fuertes correlaciones positivas para la S/R al variar tanto los valores de kVp (0,79) como de mAs (0,65). Por el contrario, se halló que la fuerza de correlación de los valores de la C/R era moderada al cambiar los valores de kVp (0,58) y mAs (0,53).(AU)

Introduction and ObjectivesIn order to perform chest dose optimisation studies, the imaging phantom should be adequate for image quality evaluation. Since high-end phantoms are cost prohibitive, there is a need for a low-cost construction method with fairly available tissue substitutes.Materials and MethodsTheoretical calculations of radiological characteristics were performed for each of lung, cortical bone and soft tissues in order to choose appropriate substitute, then, cork, P.V.C. (Polyvinyl Chloride) and water were chosen, respectively. Validation included, firstly, measuring CT Hounsfield Units (HU) of a real patient's tissues then compared against their corresponding anatomies in the constructed phantom. Secondly, Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values were acquired in this study to evaluate the quality of images generated from the constructed phantom, then, compare their trends with a valid phantom under different exposure parameters (kVp and mAs).ResultsFrom theoretical calculations, the percentage differences showed high accuracy of tissue substitutes when simulating real patient tissues; P.V.C. was ≥ 5.78%, cork was ≥ 4.46% and water ≥ 5%. The percentage difference (CT HU) between lung and cortical bone and their equivalent tissue substitutes were 10.44% and 0.53%-3.17%, respectively. Strong positive correlations were found for SNR when changing both kVp (0.79) and mAs (0.65). While the correlation strength of CNR values were found to be moderate when changing both kVp (0.58) and mAs (0.53).ConclusionsOur low-cost phantom approved through CT HU that their materials replicate the radiological characteristics of real one-year-old child while SNR and SNR correlations confirmed its applicability in imaging and optimisation studies.(AU)