Contrast-Enhanced MR Imaging of Lymph Nodes in Cancer Patients

The accurate identification and characterization of lymph nodes by modern imaging modalities has important therapeutic and prognostic significance for patients with newly diagnosed cancers. The presence of nodal metastases limits the therapeutic options, and it generally indicates a worse prognosis for the patients with nodal metastases. Yet anatomic imaging (CT and MR imaging) is of limited value for depicting small metastatic deposits in normal-sized nodes, and nodal size is a poor criterion when there is no extracapsular extension or focal nodal necrosis to rely on for diagnosing nodal metastases. Thus, there is a need for functional methods that can be reliably used to identify small metastases. Contrast-enhanced MR imaging of lymph nodes is a non-invasive method for the analysis of the lymphatic system after the interstitial or intravenous administration of contrast media. Moreover, some lymphotrophic contrast media have been developed and used for detecting lymph node metastases, and this detection is independent of the nodal size. This article will review the basic principles, the imaging protocols, the interpretation and the accuracies of contrast-enhanced MR imaging of lymph nodes in patients with malignancies, and we also focus on the recent issues cited in the literature. In addition, we discuss the results of several pre-clinical studies and animal studies that were conducted in our institution

Elevated urinary PCO2 in the rat: An intrarenal event

Elevated urinary PCO2 in the rat: An intrarenal event. During a bicarbonate diuresis, final urine PCO2 considerably exceeds systemic PCO2, an effect thought to reflect the postpapiliary delayed dehydration of carbonic acid. To test this explanation, PCO2 tensions along the inner medullary collecting duct (IMCD) of bicarbonate-loaded rats were measured directly using PCO2 microelectrodes. With systemic PCO2 held at 40mm Hg, IMCD PCO2 exceeded systemic PCO2 in every measurement by an average of 20 to 30mm Hg. A significant increment in PCO2 was seen between 50% IMCD length and the papilla tip. During the infusion of carbonic anhydrase, IMCD PCO2 was reduced but not to systemic levels. Finding elevated PCO2 along the terminal IMCD deemphasizes the importance of postpapillary delayed dehydration and suggests the possibility that bicarbonaturia is associated with papillary accumulation of carbon dioxide.PCO2 urinaire élevée chez le rat: Un phénomène intra-rénal. Au cours d'une diurèse induite par la perfusion de bicarbonate, la PCO2 de l'urine définitive est considérablement supérieure à la PCO2 systémique, fait que l'on attribue à la déshydratation postpapillaire retardée d'acide carbonique. Pour vérifier cette explication, la PCO2 le long du tube collecteur de la médullaire interne (TCMI) chez des rats recevant du bicarbonate étaient mesuré directement en utilisant des microélectrodes a PCO2. Lorsque la PCO2 systémique était maintenue à 40mm Hg, la PCO2 dans le TCMI dépassait à chaque mesure la PCO2 de 20 à 30mm Hg en moyenne. Une augmentation significative de la PCO2 était notée entre la moitié de la longueur du TCMI et la pointe de la papille. Pendant la perfusion d'anhydrase carbonique la PCO2 du TCMI diminuait mais n'atteignait pas les valeurs systémiques. Le fait que la PCO2 soit élevée le long du TCMI terminal fait perdre son importance à l'hydrolyse postpapillaire retardée et suggére la possibilité que la bicarbonaturie soit associée a une accumulation papillaire de carbon dioxide