RESUMEN
About two million peripheral angiographies are performed annually in the United States, hence a reduction in exposure would yield significant healthcare benefits. The synchronization of bolus traveling, the table motion, and the fluoroscopic imaging chain can be highly effective for dose reduction in Digital Subtraction Angiography (DSA) by minimizing the field-of-view according to the vascular anatomy of the region traveled by the bolus. The goal of this paper is to demonstrate the feasibility of adjusting the field-of-view while tracking the contrast bolus, thus reducing the dosage of both the bolus and the radiation. The speed of the bolus is respectively estimated in the systole and diastole stages. An EKG-gated Hammerstein model is used to predict the bolus chasing speed. A real-time algorithm is designed to extract the bolus dynamics, and define the field of view transversely and longitudinally. A limb stabilization technique is also presented to suppress any significant image misalignment. Our simulation results show that the proposed techniques are promising for clinical applications.
Asunto(s)
Neoplasias Encefálicas/diagnóstico , Encéfalo/patología , Medios de Contraste/administración & dosificación , Imagen por Resonancia Magnética/métodos , Adenoma/diagnóstico , Combinación de Medicamentos , Gadolinio/administración & dosificación , Gadolinio DTPA , Glioma/diagnóstico , Humanos , Aumento de la Imagen , Meglumina/administración & dosificación , Neuroma Acústico/diagnóstico , Compuestos Organometálicos/administración & dosificación , Ácido Pentético/administración & dosificación , Ácido Pentético/análogos & derivados , Neoplasias Hipofisarias/diagnósticoRESUMEN
Many factors affect the ability to detect a CNS lesion. There is no single contrast dose that is optimal for all diseases. By understanding these factors that may affect lesion detection, the appropriate dose for specific pathologic processes may be determined.
Asunto(s)
Neoplasias del Sistema Nervioso Central/diagnóstico , Medios de Contraste , Gadolinio , Imagen por Resonancia Magnética , HumanosRESUMEN
PURPOSE: To study the efficacy of contrast MR imaging in the evaluation of central nervous system complications in the cardiopulmonary bypass patient and attempt to explain their pathophysiology based on the MR appearance and the cardiopulmonary bypass protocol. METHOD: Nineteen patients were prospectively studied with contrast MR examinations the day before and 3 to 7 days after cardiopulmonary bypass, to determine the nature, extent, and number of new postoperative MR abnormalities. Cardiopulmonary bypass parameters used in our institution included: membrane oxygenation, arterial filtration with a pore size of 25 microns, and a relatively high perfusion rate to produce a cardiac index of 2.0 to 2.5 L/min per m2. RESULTS: The preoperative noncontrast MR examination showed age-related changes and/or signs of ischemia in 60% of patients on the day before surgery. However, there was no abnormal enhancement or new T2 abnormalities on any postoperative MR examination to suggest hypoperfusion or emboli. None of the 19 patients developed overt neurologic deficits postoperatively. Review of the cardiopulmonary bypass protocol used indicated significant variations in technique at different institutions. CONCLUSION: Contrast MR imaging demonstrated no new abnormalities in patients after cardiopulmonary bypass performed with strict in-line arterial filtration and relatively high perfusion. MR imaging is feasible in the early postoperative period after cardiopulmonary bypass and may offer a convenient method for evaluation of the neurologic impact of technical factors associated with cardiopulmonary bypass.