RESUMEN
BACKGROUND: Detecting and interpreting changes in the images of follow-up CT scans by the clinicians is often time-consuming and error-prone due to changes in patient position and non-rigid anatomy deformations. Thus, reconstructed repeat scan images are required, precluding reduced dose sparse-view repeat scanning. OBJECTIVE: A method to automatically detect changes in a region of interest of sparse-view repeat CT scans in the presence of non-rigid deformations of the patient's anatomy without reconstructing the original images. METHODS: The proposed method uses the sparse sinogram data of two CT scans to distinguish between genuine changes in the repeat scan and differences due to non-rigid anatomic deformations. First, size and contrast level of the changed regions are estimated from the difference between the scans' sinogram data. The estimated types of changes in the repeat scan help optimize the method's parameter values. Two scans are then aligned using Radon space non-rigid registration. Rays which crossed changes in the ROI are detected and back-projected onto image space in a two-phase procedure. These rays form a likelihood map from which the binary changed region map is computed. RESULTS: Experimental studies on four pairs of clinical lung and liver CT scans with simulated changed regions yield a mean changed region recall rate >â86%and a mean precision rate >â83%when detecting large changes with low contrast, and high contrast changes, even when small. The new method outperforms image space methods using prior image constrained compressed sensing (PICCS) reconstruction, particularly for small, low contrast changes (recallâ=â15.8%, precisionâ=â94.7%). CONCLUSION: Our method for automatic change detection in sparse-view repeat CT scans with non-rigid deformations may assist radiologists by highlighting the changed regions and may obviate the need for a high-quality repeat scan image when no changes are detected.
Asunto(s)
Procesamiento de Imagen Asistido por Computador , Tomografía Computarizada por Rayos X , Abdomen , Algoritmos , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Hígado , Fantasmas de Imagen , Tomografía Computarizada por Rayos X/métodosRESUMEN
BACKGROUND: Many pediatric trauma patients are initially evaluated at non-pediatric, non-trauma centers where they undergo CT prior to transfer to a pediatric trauma center. The purpose of this study is to quantify the number of repeat CT and assess the risk of delayed or missed injuries. METHODS: The institutional pediatric trauma registry was queried for patients evaluated from January 2001 to March 2012. All patients who underwent repeat CT within 24 h after transfer were included. General admission, demographic, and outcome data were analyzed. RESULTS: A total of 6041 patients were transferred from a referring hospital after undergoing CT scans. Five percent of patients underwent repeat CT with a mean age of 6.3 ± 5.7 years. Patients who underwent repeat CT scans had significantly higher Injury Severity Scores and lower Glasgow Coma Scale. CT head was the most commonly repeated. Comparing results of referring CT scans to repeated scans, there was good agreement between results for head CT (κ = 0.69) and moderate agreement for abdominopelvic CT (κ = 0.59). The overall incidence of delayed diagnosis of injuries was 0.7%. CONCLUSION: The low incidence of missed or delayed injuries justifies limiting additional radiation exposure to pediatric trauma patients based on clinical status.