ABSTRACT
Objective: To explore the optimal acquisition protocols for 177Lu-Dotatate SPECT/CT imaging based on different energy windows and collimators. Methods 177Lu SPECT images of a NEMA IEC body phantom with known activity concentration ration (12:1) between filled hollow spheres and uniform background were acquired with 3 different collimators: Low energy high resolution (LEHR), medium energy general purpose (MEGP) and high energy general purpose (HEGP). Main energy window was defined around the energy peak 113 keV, 208 keV and 113 keV+208 keV with 20% width. Scatter correction was performed with applying attenuation correction and triple energy window method. Thus 9 different acquisition protocols could be produced, including LEHR_113, LEHR_208, LEHR_113+208, MEGP_113, MEGP_208, MEGP_113+208, HEGP_113, HEGP_208 and HEGP_113+208 in short. The intensity ratio between spheres and background, relative error and conversion factor were measured and corrected for partial volume effect and used to compare the performance of different methods. Results: The contrast of MEGP_208 SPECT image was the worst, whereas better visual resolution images were achieved by MEGP_208 and MEGP_113+208. The measured average intensity ratios of 9 methods were all lower than the real ratio (F=2.659, P=0.040). The relative error of intensity ratio in MEGP_113+208 was the minimum ([-1.33±6.40]%), and in LEHR_208 was the maximum ([-58.34±14.42]%). All acquisition protocols showed significant difference in conversion factor (F=4.846, P=0.003). Conclusion: Different acquisition protocols have significant effect on the results of 177Lu-Dotatate SPECT/CT quantitative imaging. Image quality of MEGP collimator combined with 113 keV+208 keV is the best, and the intensity ratio is the closest to the real ratio.
ABSTRACT
Introducción: en aplicaciones biomédicas, la termografía infrarroja ha permitido visualizar el patrón de distribución de temperatura de la piel y el tejido subyacente, permitiendo diagnosticar problemas vasculares o nerviosos y, particularmente, trastornos en la termorregulación como el fenómeno de Raynaud y la intolerancia al frío. Sin embargo, las publicaciones no detallan el protocolo de adquisiciónde imágenes ni validan el mismo; factores determinantes para la calidad y relevancia de la informacióndiagnóstica obtenida. Objetivo: diseñar y validar un protocolo de adquisición de imágenes por termografía infrarroja para analizar la termorregulación en la mano. Materiales y métodos: Se diseñó un nuevo protocolo de adquisición de imágenes por termografía infrarroja utilizando un estímulofrío en la mano. Se analizaron estadísticamente regiones de interés de imágenes termográficas de 18 mediciones intrasujeto en un único sujeto y mediciones intersujeto en 17 individuos sanos. Resultados: En las mediciones intrasujeto e intersujeto se encontró que 10 minutos después del estímulo frío el porcentaje de recuperación de la temperatura fue cercano al 100%, excepto en un individuo en el cual, a pesar de no reportar enfermedades o lesiones previas, la punta de los dedos después del estímulo alcanzó apenas los 28 ºC. La prueba de fatiga en uno de los sujetos sanos mostró alteraciones en el proceso de termorregulación de la mano cuando el protocolo se repite en corto tiempo.
Introduction: in biomedical applications, infrared thermography has allowed to visualize the temperaturedistribution patterns of skin and underlying tissue, allowing the diagnosis of vascular or nervous disorders, particularly disturbances in the thermoregulation process as Raynauds phenomenon and cold intolerance. However, most papers not detailed the images acquisition protocol or its validation, being these two determining factors to the quality and relevance of the obtained diagnostic information.Objective: To design and validate an acquisition protocol of diagnostic imaging by infrared thermographyto analyze the thermoregulation process in hand. Material and methods: It was designed a new acquisition protocol of diagnostic imaging by infrared thermography using a cold stimulus in hand. It was statistically analyzed the regions of interest of thermographic images of 18 intrasubject measurements (in one individual) and intersubject measurements in 17 healthy individuals. Results: In the intrasubject and intersubject measurements, it found that 10 minutes after the cold stimulus the temperature measured was close to 100% of initial temperature, except for one of healthy subjects who, despite not report diseases or previous injuries, the temperature of the fingertips after stimulus barely reached 28 °C. The fatigue test in one healthy subject presents alterations in the thermoregulation process in hand when the protocol was repeated in a short time.