ABSTRACT
Understanding particle deposition in the human lung is crucial for the assessment of environmental pollutants and the design of new drug delivery systems. Traditionally, research has been carried out by experimental analysis, but this generally requires expensive equipment and exposure of volunteers to radiation, resulting in limited data. To overcome these drawbacks, there is an emphasis on the development of numerical models capable of accurate predictive analysis. The most advanced of these computer simulations are based on three-dimensional computational fluid dynamics. Solving the flow equations in a complete, fully resolved lung airway model is currently not feasible due to the computational resources required. In the present work, a simplified lung model is presented and validated for accurate prediction of particle deposition. Simulations are performed for an 8-path approximation to a full lung airway model. A novel boundary condition method is used to ensure accurate results in truncated flow branches. Simulations are performed at a steady inhalation flow rate of 18 l min-1, corresponding to a low activity breathing rate, while the effects of particle size and density are investigated. Comparison of the simulation results with available experimental data shows that reasonably accurate results can be obtained at a small fraction of the cost of a full airway model. The simulations clearly evaluate the effect of both particle size and particle density. Most importantly, the results show an improvement over a previously documented single-path model, both in terms of accuracy and the ability to obtain regional deposition rates. The present model represents an improvement over previously used simplified models, including single-path models. The multi-path reduced airway approach described can be used by researchers for general and patient-specific analyses of particle deposition and for the design of effective drug delivery systems.
Subject(s)
Breath Tests , Models, Biological , Humans , Lung , Administration, Inhalation , Computer Simulation , Particle Size , AerosolsABSTRACT
OBJECTIVE: Infection of large vessel prostheses is a rare but critical complication. The aim of this work is to assess the impact of PET/CT with 18F-Fluordesoxyglucose (PET-FDG) on the diagnosis of infection in our environment. MATERIAL AND METHODS: Thirty-five patients (38 scans) were evaluated for suspected prosthetic infection. A qualitative analysis was performed taking into account the distribution of the radiopharmaceutical, categorizing the studies as positive or negative for infection. Those with focal or multifocal deposits along the vascular prosthesis were considered positive, and negative if a homogeneous and diffuse distribution over the whole prosthesis was observed, or a total absence of uptake. A semi-quantitative analysis was performed using SUVmax and average SUV values, and a metabolic index was calculated (SUVmax of the graft / average SUV of the normal vascular pool). RESULTS: The PET-FDG study was positive in 20 patients, with a diagnostic accuracy of 84%. The 38 PET-FDG scans performed showed positive capture patterns (focal in 6, multifocal in 15, diffuse in 4) and negative pattern in the remaining 13. The sensitivity, specificity, positive and negative predictive values obtained for the PET-FDG were 95%, 89%, 90% and 94%, and for the AngioTC study 50%, 73%, 73% and 50%, respectively. The area values under the ROC curve were as follows: for the AngioTC 0.642 (not significant), and for the SUVmax values of 0.925 (p<0.005), average SUV of 0.922 (p<0.005) and for the metabolic index of 0.917 (p<0.005). CONCLUSIONS: The PET-FDG proves to be a tool with high diagnostic accuracy in the infection of vascular prosthesis, both visual analysis according to patterns and semi-quantitative.
ABSTRACT
Introducción: En los últimos años han surgido nuevos estudios de imagen en diagnóstico y seguimiento de tumores urológicos metastásicos. Material y métodos: Se revisa a 41 pacientes con sospecha de recidiva de tumor urotelial o renal, analizando el rendimiento diagnóstico de las PET-TC realizadas entre 2013 y 2016. Resultados: Recopilamos 17 tumores uroteliales y 24 renales, con una mediana de seguimiento de 30 meses. Un 29,3% de los uroteliales corresponden a alto grado y un 29,3% de los renales a carcinoma de célula clara Furhman II. En conjunto, los estudios de imagen detectaron recidivas en 34 pacientes. La TC fue positiva en el 83% de los pacientes, mientas la PET lo fue en el 75,6%. La coincidencia TC/PET fue del 50%. La PET detectó más enfermedad en un 41% de los casos frente a un 5% con TC. Esto supuso un cambio en la estrategia terapéutica en el 40% de los pacientes. La sensibilidad, especificidad, valor predictivo positivo y negativo para la TC y la PET fueron de 92 y 92%; 57 y 100%; 92 y 100% y 57 y 70%, respectivamente. Conclusión: En tumores urológicos, la PET presenta una sensibilidad similar a las técnicas de imagen estándar, pero con una mayor especificidad, valor predictivo positivo y valor predictivo negativo. Esto supuso un cambio en la estrategia de tratamiento en el 40% de los pacientes de nuestra serie. La PET probablemente se convierta en la prueba de referencia en los estudios de extensión y seguimiento de la mayor parte de los tumores urológicos
Introduction: New imaging studies have appeared in recent years for the diagnosis and follow-up of metastatic urological tumours. Material and methods: A total of 41 patients were reviewed with suspected recurrence of a urothelial or kidney tumour, analysing the diagnostic performance of PET-CT scans undertaken between 2013 and 2016. Results: We collected 17 urothelial tumours and 24 renal tumours, with a median follow-up of 30 months. A total of 39.3% of the urothelial tumours were high grade and 29.3% of the kidney tumours were clear cell Fuhrman II. As a whole, the imaging studies detected recurrences in 34 patients. CT was positive in 83% of the patients, while the PET scan was positive in 75.6%, CT/PET coincidence was 50%. The PET scan detected further disease in 41% of the cases compared to 5% by CT. This resulted in a change of therapeutic strategy in 40% of the patients. Sensitivity, specificity, positive predictive value and negative predictive value for the CT and the PET scans were 92% and 92%, 57% and 100%, 92% and 100%, and 57% and 70% respectively. Conclusion: The PET scan showed similar sensitivity for urological tumours to the standard imaging techniques but with higher specificity, positive predictive value and negative predictive value. This led to a change in treatment strategy for 40% of the patients in our series. The PET scan will probably become the standard test in the extension and follow-up studies of most urological tumours
Subject(s)
Humans , Male , Female , Adult , Middle Aged , Aged , Kidney Neoplasms/diagnostic imaging , Urologic Neoplasms/diagnostic imaging , Neoplasm Recurrence, Local/diagnostic imaging , Fluorodeoxyglucose F18/administration & dosage , Radiopharmaceuticals/administration & dosage , Positron Emission Tomography Computed Tomography , Follow-Up Studies , Retrospective Studies , Sensitivity and SpecificityABSTRACT
INTRODUCTION: New imaging studies have appeared in recent years for the diagnosis and follow-up of metastatic urological tumours. MATERIAL AND METHODS: A total of 41 patients were reviewed with suspected recurrence of a urothelial or kidney tumour, analysing the diagnostic performance of PET-CT scans undertaken between 2013 and 2016. RESULTS: We collected 17 urothelial tumours and 24 renal tumours, with a median follow-up of 30 months. A total of 39.3% of the urothelial tumours were high grade and 29.3% of the kidney tumours were clear cell Fuhrman II. As a whole, the imaging studies detected recurrences in 34 patients. CT was positive in 83% of the patients, while the PET scan was positive in 75.6%, CT/PET coincidence was 50%. The PET scan detected further disease in 41% of the cases compared to 5% by CT. This resulted in a change of therapeutic strategy in 40% of the patients. Sensitivity, specificity, positive predictive value and negative predictive value for the CT and the PET scans were 92% and 92%, 57% and 100%, 92% and 100%, and 57% and 70% respectively. CONCLUSION: The PET scan showed similar sensitivity for urological tumours to the standard imaging techniques but with higher specificity, positive predictive value and negative predictive value. This led to a change in treatment strategy for 40% of the patients in our series. The PET scan will probably become the standard test in the extension and follow-up studies of most urological tumours.
