Pruebas técnicas de aceptación de la PET/CT del modelo Biograph Vision 450 de Siemens
Fecha
2023-11-09
Tipo
tesis de maestría
Autores
Ramírez Morera, Óscar Paul
Título de la revista
ISSN de la revista
Título del volumen
Editor
Resumen
Esta tesis académica, para optar por el título de maestría académica en física médica, versa
sobre las pruebas técnicas de aceptación del sistema tomográfico PET/CT BV 450, el cual pertenece
al proyecto ciclotrón-PET/CT de la UCR. Dichas pruebas técnicas buscan comprobar el correcto
desempeño de la PET/CT BV 450 (objeto de estudio), el cual se verifica mediante la inspección de
un conjunto de parámetros técnicos de calidad de imagen y su confrontación con valores de
referencia de estándares protocolarios internacionales o técnicos del fabricante Siemens
Healthineers.
Así, pues, el objetivo general de esta tesis académica fue verificar el desempeño correcto de
la PET/CT BV 450 para la producción de imágenes médicas funcionales y anatómicas de alta
calidad para la investigación científica o clínica. Ahora bien, para llevarse a cabo dicho objetivo
general en esta tesis académica, se desarrollaron tres capítulos, los cuales corresponden con tres
objetivos específicos: en el primer capítulo, se muestra la teoría científica pertinente para la
explicación del funcionamiento de la PET/CT BV 450; en el segundo capítulo, se redacta el
protocolo de pruebas técnicas de aceptación de la PET/CT BV 450 (i.e., la metodología); y,
finalmente, en el tercer capítulo, se realizan los correspondientes análisis y discusión de los
resultados de las mediciones de las pruebas técnicas de aceptación, confrontando dichos resultados
con los criterios técnicos de aprobación protocolaria. Una vez terminados el análisis y la discusión
de resultados, una síntesis de los resultados se presentará.
En síntesis, los resultados de CT fueron: (1) exactitud del alineamiento del láser en el rango
0.00–1.96 mm; dichos valores son menores a 2 mm. (2) exactitud del desplazamiento de la camilla
(i) horizontal en el rango -1.50–0.50 mm, (ii) vertical en el rango 0.00–1.00 mm; dichos valores son
menores a 2 mm. (3) desempeño de bajo contraste (valores de CNR) de 3.821 > 1.000 (protocolo
de cabeza adulta), 1.006 > 1.000 (protocolo de abdomen adulto), 0.758 > 0.700 (protocolo de
cabeza pediátrica), 4.768 > 0.400 (protocolo abdomen pediátrico). (3) resolución espacial para el
patrón visible de 10 barras de aluminio, el cual es mayor a 6 barras de aluminio. (4) uniformidad de
los números CT (diferencias de medidas entre valores periféricos y el valor central) dada por el
rango 0.000–3.676 UH; ningún valor superó las 5 UH. (5) exactitud del número CT evaluada en
acrílico (120.270–132.264 UH), en agua (3.230–6.099 UH), en aire (-996.727–-991.132 UH), en
polietileno (-97.373–-84.267 UH) y en teflón (864.332–966.124 UH); todos estos valores en UH se
encuentran dentro de los rangos protocolarios para cada tipo de material. (6) evaluación visual de
artefactos; no hubo ningún artefacto indicador de un problema sistémico. (7) dosimetría de CT
(comparación de valores de CTDIVOL medidos con cámara de ionización con los valores reportados
por el propio sistema tomográfico); para cuatro protocolos distintos de escaneo (cabeza y abdomen,
adulto y niño), los valores de error de medición (en el rango de 0.13–6.93%) no excedieron el 20%.
(8) ancho del haz de radiación (comparación entre el valor de la medición de dicho ancho y el ancho
nominal según el propio sistema tomográfico); para tres colimaciones distintas del haz de rayos X, obtuvimos (i) 1×5: 1.00, 20.00%, (ii) 6×1.2: 2.80, 38.89%, (iii) 12×1.2: 3.60, 25.00%, donde se
cumple que la diferencia absoluta no se excede de 3 mm o el error porcentual no supera el 30%.
En síntesis, los resultados de PET y PET+CT fueron: (1) la resolución espacial resultó en el
rango de valores medidos de FWHMespacial de 3.37–3.44 mm, el cual corresponde con un rango de
errores porcentuales de 0.405%–8.147%; algunos de estos valores porcentuales no superan el 5% de
error porcentual y algunos valores de FWHMespacial no superan los valores del fabricante (3.40, 3.70
mm). (2) la sensibilidad, cuyos valores medidos, relativos al isocentro, fueron 10.26 cps/kBq (en 0
cm) y 10.44 cps/kBq (en 10 cm); el valor medio 10.35 cps/kBq es superior al valor del fabricante
(8.9 cps/kBq). (3) la fracción medida de dispersión fue 37.86% tal que 37.86% < 1.05·39% (valor
del fabricante) y la estimación de las pérdidas de cuentas por tiempo muerto y por eventos
aleatorios fue 156.23 kcps, el cual sólo se desvía del valor dado por el fabricante (160 kcps) por un
2.35%. (4) la evaluación de la exactitud de las correcciones, por pérdidas de cuentas (tiempo
muerto) y por eventos aleatorios, resultó en un error de conteo de coincidencias verdaderas de –
3.4% (NECRmax), el cual corresponde con una tasa medida de cuentas verdaderas casi idéntica a la
tasa de cuentas verdaderas de baja radioactividad (96.6% de similitud). (5) la resolución de
sincronización de coincidencias de tiempo de vuelo resultó en un valor de FWHMtemporal de 213.1 ps
tal que 213.1 ps < 1.05·214 ps (valor del fabricante). (6) la evaluación de la calidad de imagen
resultó en el rango de valores medidos de recuperación de contraste porcentual de 29.29–83.72% y
en el rango de valores medidos de variabilidad porcentual del fondo de 2.66%–3.72%; dichos
rangos corresponden con valores de contraste suficientemente altos y valores de variabilidad del
fondo suficientemente bajos. (7) la prueba de la exactitud del corregistro de las imágenes PET+CT
resultó en diferencias de distancias entre fuentes radioactivas, medidas en la imagen CT y en la
imagen PET, de 0.913 mm (línea 1-2) y 0.738 mm (línea 1-3); ninguno de estos valores medidos
superó 1 mm.
Las dos síntesis anteriores de los resultados de las pruebas técnicas de aceptación de la
PET/CT BV 450 mencionan, para cada uno de los puntos de cada prueba técnica en particular, el
correspondiente criterio técnico de aprobación al final de la redacción de cada punto. Por lo tanto,
todas las pruebas técnicas de aceptación de la PET/CT BV 450, efectuadas para el desarrollo de esta
tesis académica, fueron aprobadas por dicho sistema tomográfico. Por consiguiente, el sistema
tomográfico PET/CT BV 450 cumplió las normas técnicas de los estándares protocolarios
internacionales y de las especificaciones técnicas del fabricante Siemens Healthineers, y dicho
sistema posee un excelente desempeño técnico, el cual es apropiado para su servicio clínico e
investigativo. A su vez, los resultados de estas pruebas técnicas de aceptación de la PET/CT BV 450
se podrán usar como las líneas base del control de calidad rutinario en el proyecto ciclotrón-PET/CT
de la UCR.
This academic thesis, as an academic requirement to obtain a master degree on medical physics from UCR’s postgraduate program, is about acceptance technical testing of PET/CT BV 450 system which belongs to UCR’s cyclotron-PET/CT project. The purpose of these technical testing is to verify the correct performance of PET/CT BV 450 (study’s object) which is verified by evaluating a set of image quality technical parameters and comparing their corresponding measurement results to international protocol’s performance criteria or manufacturer’s performance criteria (Siemens Healthineers). Thus, the general objective of this academic thesis is to verify the correct performance of PET/CT BV 450 system, that is, its capacity to produce high quality, anatomical, functional images for clinical and researching purposes. Then, realizing this thesis’ general objective means to develop three chapters which correspond to thesis’ three specific objectives, namely: (1) to explain synthetically the scientific theory of PET/CT BV 450’s functioning; (2) to describe in detail acceptance technical testing procedures of PET/CT BV 450 system (i.e., methodology) based on NEMA NU-2 2018 and ACR 2017 protocols; (3) to analyze and discuss measurement results obtained from acceptance technical testing comparing them to protocol acceptance criteria. Once analysis and discussing of measurement results are done, a synthesis of results is shown. In summary, results from technical acceptance testing of CT are: (1) range of distance measurement for scout prescription and alignment light accuracy testing is 0.00–1.96 mm; distance values are less than 2 mm. (2) ranges of table travel accuracy testing: (i) -1.50–0.50 mm (horizontal displacement), (ii) 0.00–1.00 mm (vertical displacement); these displacement values are less than 2 mm. (3) CNR values for low-contrast performance testing: 3.821 > 1.000 (adult head scan protocol), 1.006 > 1.000 (adult abdomen scan protocol), 0.758 > 0.700 (pediatric head scan protocol), 4.768 > 0.400 (pediatric abdomen protocol). (3) amount of metalic lines per centimeter for spatial resolution testing: 10 visible metalic lines per centimeter of high-contrast target; this measured number of metalic lines per centimeter is greater than 6 lines per centimeter. (4) Hounsfield unit values for CT number uniformity testing are given by the following range: 0.000– 3.676 UH; none of these UH values exceed 5 UH. (5) Hounsfield unit value ranges for CT number accuracy testing are given by the following regions of interest made from specific material: acrylic (120.270–132.264 UH), water (3.230–6.099 UH), air (-996.727–-991.132 UH), polyethylene (- 97.373–-84.267 UH), teflon (864.332–966.124 UH); all of these UH values fall inside of protocol ranges. (6) in case of artifact evaluation, there are no artifacts indicating a CT systematic problem. (7) CT dosimetry testing (comparison between CTDIVOL values measured by pencil ionizing chamber and CT system’s own CTDIVOL measurement values); CTDIVOL measured values for four different scan protocols (adult head, adult abdomen, pediatric head, pediatric abdomen) [range of 0.13–6.93%] are within 20% of the values reported by the CT system. (8) radiation beam width testing (comparison between measured radiation beam width and nominal radiation beam width, i.e., CT system’s own measured radiation beam width); measurement values for three different X- ray beam collimations are given by: (i) 1×5: 1.00, 20.00%, (ii) 6×1.2: 2.80, 38.89%, (iii) 12×1.2: 3.60, 25.00%, where measured radiation beam widths are accurate to within 3 mm or 30% of the total nominal collimated beam widths. In summary, results from technical acceptance testing of PET and PET+CT are: (1) the range of measured FWHMspatial for spatial resolution testing is given by 3.37–3.44 mm; this range corresponds to an measurement percentage error range of 0.405%–8.147%; some of these percentage values do not exceed 5% of tolerated percentage error and some values of FWHMspatial do not exceed manufacturer’s reference values (3.40 mm, 3.70 mm). (2) sensitivity testing’s measured values relative to system’s isocenter are 10.26 cps/kBq (at 0 cm) and 10.44 cps/kBq (at 10 cm); the mean value of these two sensitivity measurements is 10.35 cps/kBq which is greater than manufacturer’s sensitivity value (8.9 cps/kBq). (3) in case of scatter fraction, count losses, and random measurement testing, the measured scatter fraction is 37.86% so that 37.86% < 1.05·39% (manufacturer’s value) and the estimation of count losses and randoms is 156.23 kcps which deviates from manufacturer’s value (160 kcps) by a percentage of 2.35%. (4) evaluation of the accuracy of count losses and randoms corrections has resulted in a true coincidence count rate error of –3.4% (NECRmax) which corresponds to a measured true concidence count rate almost identical to low-radioactivity true coincidence count rate (percentage similarity value of 96.6%). (5) a measured value of FWHMtemporal of 213.1 ps is obtained from time of flight resolution testing so that 213.1 ps < 1.05·214 ps (manufacturer’s value). (6) in case of image quality evaluation, the range of measured percentage contrast recovery values is 29.29–83.72% and the range of measured percentage background variability values is 2.66%–3.72%; these ranges correspond to sufficiently-high percentage contrast recovery values and sufficiently-low percentage background variability values. (7) PET+CT image coregistration accuracy testing results in two-sources-distance difference, one two-sources-distance measured in CT image and another two-sources-distance measured in PET image, of 0.913 mm (1-2 line) and 0.738 mm (1-3 line); none of these values exceeds 1 mm. At the end of each previously written sentence about a particular PET/CT acceptance technical test, its corresponding protocol technical criterion is indicated. Then, all PET/CT acceptance technical tests of this academic thesis are approved and, therefore, PET/CT BV 450 system fulfills international protocol standard technical norms and Siemens Healthineers’ technical specifications. Thus, this tomographic system has an excellent technical performance which is appropriate for clinical service and research. In turn, these PET/CT acceptance technical testing results are available to be used as baselines for routine quality control at UCR’s cyclotron-PET/CT project.
This academic thesis, as an academic requirement to obtain a master degree on medical physics from UCR’s postgraduate program, is about acceptance technical testing of PET/CT BV 450 system which belongs to UCR’s cyclotron-PET/CT project. The purpose of these technical testing is to verify the correct performance of PET/CT BV 450 (study’s object) which is verified by evaluating a set of image quality technical parameters and comparing their corresponding measurement results to international protocol’s performance criteria or manufacturer’s performance criteria (Siemens Healthineers). Thus, the general objective of this academic thesis is to verify the correct performance of PET/CT BV 450 system, that is, its capacity to produce high quality, anatomical, functional images for clinical and researching purposes. Then, realizing this thesis’ general objective means to develop three chapters which correspond to thesis’ three specific objectives, namely: (1) to explain synthetically the scientific theory of PET/CT BV 450’s functioning; (2) to describe in detail acceptance technical testing procedures of PET/CT BV 450 system (i.e., methodology) based on NEMA NU-2 2018 and ACR 2017 protocols; (3) to analyze and discuss measurement results obtained from acceptance technical testing comparing them to protocol acceptance criteria. Once analysis and discussing of measurement results are done, a synthesis of results is shown. In summary, results from technical acceptance testing of CT are: (1) range of distance measurement for scout prescription and alignment light accuracy testing is 0.00–1.96 mm; distance values are less than 2 mm. (2) ranges of table travel accuracy testing: (i) -1.50–0.50 mm (horizontal displacement), (ii) 0.00–1.00 mm (vertical displacement); these displacement values are less than 2 mm. (3) CNR values for low-contrast performance testing: 3.821 > 1.000 (adult head scan protocol), 1.006 > 1.000 (adult abdomen scan protocol), 0.758 > 0.700 (pediatric head scan protocol), 4.768 > 0.400 (pediatric abdomen protocol). (3) amount of metalic lines per centimeter for spatial resolution testing: 10 visible metalic lines per centimeter of high-contrast target; this measured number of metalic lines per centimeter is greater than 6 lines per centimeter. (4) Hounsfield unit values for CT number uniformity testing are given by the following range: 0.000– 3.676 UH; none of these UH values exceed 5 UH. (5) Hounsfield unit value ranges for CT number accuracy testing are given by the following regions of interest made from specific material: acrylic (120.270–132.264 UH), water (3.230–6.099 UH), air (-996.727–-991.132 UH), polyethylene (- 97.373–-84.267 UH), teflon (864.332–966.124 UH); all of these UH values fall inside of protocol ranges. (6) in case of artifact evaluation, there are no artifacts indicating a CT systematic problem. (7) CT dosimetry testing (comparison between CTDIVOL values measured by pencil ionizing chamber and CT system’s own CTDIVOL measurement values); CTDIVOL measured values for four different scan protocols (adult head, adult abdomen, pediatric head, pediatric abdomen) [range of 0.13–6.93%] are within 20% of the values reported by the CT system. (8) radiation beam width testing (comparison between measured radiation beam width and nominal radiation beam width, i.e., CT system’s own measured radiation beam width); measurement values for three different X- ray beam collimations are given by: (i) 1×5: 1.00, 20.00%, (ii) 6×1.2: 2.80, 38.89%, (iii) 12×1.2: 3.60, 25.00%, where measured radiation beam widths are accurate to within 3 mm or 30% of the total nominal collimated beam widths. In summary, results from technical acceptance testing of PET and PET+CT are: (1) the range of measured FWHMspatial for spatial resolution testing is given by 3.37–3.44 mm; this range corresponds to an measurement percentage error range of 0.405%–8.147%; some of these percentage values do not exceed 5% of tolerated percentage error and some values of FWHMspatial do not exceed manufacturer’s reference values (3.40 mm, 3.70 mm). (2) sensitivity testing’s measured values relative to system’s isocenter are 10.26 cps/kBq (at 0 cm) and 10.44 cps/kBq (at 10 cm); the mean value of these two sensitivity measurements is 10.35 cps/kBq which is greater than manufacturer’s sensitivity value (8.9 cps/kBq). (3) in case of scatter fraction, count losses, and random measurement testing, the measured scatter fraction is 37.86% so that 37.86% < 1.05·39% (manufacturer’s value) and the estimation of count losses and randoms is 156.23 kcps which deviates from manufacturer’s value (160 kcps) by a percentage of 2.35%. (4) evaluation of the accuracy of count losses and randoms corrections has resulted in a true coincidence count rate error of –3.4% (NECRmax) which corresponds to a measured true concidence count rate almost identical to low-radioactivity true coincidence count rate (percentage similarity value of 96.6%). (5) a measured value of FWHMtemporal of 213.1 ps is obtained from time of flight resolution testing so that 213.1 ps < 1.05·214 ps (manufacturer’s value). (6) in case of image quality evaluation, the range of measured percentage contrast recovery values is 29.29–83.72% and the range of measured percentage background variability values is 2.66%–3.72%; these ranges correspond to sufficiently-high percentage contrast recovery values and sufficiently-low percentage background variability values. (7) PET+CT image coregistration accuracy testing results in two-sources-distance difference, one two-sources-distance measured in CT image and another two-sources-distance measured in PET image, of 0.913 mm (1-2 line) and 0.738 mm (1-3 line); none of these values exceeds 1 mm. At the end of each previously written sentence about a particular PET/CT acceptance technical test, its corresponding protocol technical criterion is indicated. Then, all PET/CT acceptance technical tests of this academic thesis are approved and, therefore, PET/CT BV 450 system fulfills international protocol standard technical norms and Siemens Healthineers’ technical specifications. Thus, this tomographic system has an excellent technical performance which is appropriate for clinical service and research. In turn, these PET/CT acceptance technical testing results are available to be used as baselines for routine quality control at UCR’s cyclotron-PET/CT project.
Descripción
Palabras clave
Pruebas técnicas de aceptación, Tomografía computarizada (CT), Tomografía por emisión de positrones (PET), Imagenología médica, Evaluación de desempeño