RESUMEN
RATIONALE AND OBJECTIVES: The authors developed a model of tissue capillary beds applicable to perfusion/diffusion imaging with magnetic resonance imaging (MRI). The model consists of a formalin-fixed excised dog kidney attached to a variable speed pump. With this system, it is possible to perfuse the kidney at selected rates. METHODS: Using the intravoxel incoherent motion model (IVIM), the apparent diffusion coefficient (ADC), diffusion coefficient (D), and perfusion fraction (f) were computed for a region of interest (ROI) in the renal cortex and in the medulla of seven kidneys, one of which was injected with a vasodilator before fixation. ADC and D values were computed for both cortex and medulla. These values were normalized to zero flow and plotted against renal perfusion. The perfusion fraction f was expressed in percent and was not normalized to zero flow. RESULTS: Normalized ADC and f were correlated with tissue perfusion rates using the Spearman rank-sum test (n = 18, rs greater than 0.5, P less than or equal to .02 for the standard preparation in both cortex and medulla), whereas normalized D (rs much less than 0.5) was uncorrelated for both preparations in cortex and medulla. CONCLUSIONS: The isolated perfused dog kidney is a useful model of tissue capillary beds for perfusion imaging technique development. The perfusion/diffusion-related parameters ADC and f increase as flow increases in the tissues, whereas D does not.
Asunto(s)
Riñón/anatomía & histología , Imagen por Resonancia Magnética/métodos , Animales , Difusión , Perros , Técnicas In Vitro , PerfusiónRESUMEN
Aneurysmal bone cysts (ABCs) have been reported in essentially every bone of the human skeleton. This case report documents a very unusual clinical appearance for this entity: a superior mediastinal mass. Also, the patient underwent multiple imaging studies that demonstrated both common (absence of septations) and unusual (extensive involvement of vertebral body with little involvement of posterior elements) characteristics of ABCs.
Asunto(s)
Quistes Óseos/diagnóstico , Neoplasias del Mediastino/diagnóstico , Neoplasias de la Columna Vertebral/diagnóstico , Vértebras Torácicas , Adulto , Quistes Óseos/complicaciones , Quistes Óseos/patología , Quistes Óseos/cirugía , Trastornos de Deglución/etiología , Diagnóstico Diferencial , Disnea/etiología , Femenino , Humanos , Imagen por Resonancia Magnética , Neoplasias del Mediastino/complicaciones , Neoplasias del Mediastino/patología , Neoplasias del Mediastino/cirugía , Parestesia/etiología , Compresión de la Médula Espinal/etiología , Fusión Vertebral , Neoplasias de la Columna Vertebral/complicaciones , Neoplasias de la Columna Vertebral/patología , Neoplasias de la Columna Vertebral/cirugía , Vértebras Torácicas/diagnóstico por imagen , Vértebras Torácicas/patología , Vértebras Torácicas/cirugía , Tomografía Computarizada por Rayos XRESUMEN
A pacemaker that increases pacing rate in response to exercise enables the pacemaker patient to improve his state of well-being. Possible sensors include atrial rate, Q-T interval, pH, venous oxygen saturation, respiratory rate, cardiac output, body motion, and blood temperature. To determine the efficacy of right ventricular blood temperature as an indicator of exercise, an experimental temperature-controlled pacemaker was developed and was evaluated in dogs. A resulting algorithm was implemented in a microcomputer-based VVI pacemaker which reliably detected exercise and rest from blood temperature when totally implanted. The pacemaker generated two pacing rates to provide increased cardiac output. Data is being obtained to establish feasibility in humans.
