4. IMAGING WORK UP AT STAGING 4.1 CROSS SECTIONAL IMAGING MODALITIES The accurate staging of gastric cancer is the most important prognostic factor for patient management. Presently, endoscopic ultrasonography (EUS) is the most reliable method for assessing the primary tumor and evaluating T and N stage with high diagnostic rates. The accuracy of EUS for gastric cancer staging varies among different authors with ranges between 64.8% and 92% for T staging and 50% and 90% for N staging, with a few incidences of overstaging and understaging [Tsendsuren et al., 2006]. Multidetector CT provides relatively valuable results of T and N staging, including differentiation between T1a, T1b, and T2 gastric cancers [Lee et al., 2010]. The use of the combination of virtual gastroscopy and dynamic contrast-enhanced MPR images obtained at multi–detector row CT after air and water distention of the stomach can improve tumor detection rates as well as accuracy rates in T and N staging of gastric cancers [Chen et al., 2007]. Virtual gastroscopy from images obtained in air-distended stomach provides an excellent overview of abnormal mucosal lesions within the stomach lumen [Lee, 2000]. The technique is most helpful in the detection of type IIa, IIc, and III early gastric cancer mucosal lesions. These lesions are usually missed at CT due to absence of thickening of the gastric wall. At CT, positive trial nodes are identified on the basis of size, shape, and enhancement pattern. CT in general is relatively insensitive and also nonspecific for detecting nodal metastases due to its inability to detect microscopic nodal invasion, which is common in gastric cancer, and the presence of reactive nodes that may be greater than [Monig et al., 1999]. The role of FDG PET in the preoperative staging of gastric cancer is considered to be still uncertain but it is most useful in detecting advanced disease [Podoloff et al., 2007]. PET is not yet accepted because it cannot provide the exact T stage and N stage of
4. IMAGING WORK UP AT STAGING 4.1 CROSS SECTIONAL IMAGING MODALITIES The accurate staging of gastric cancer is the most important prognostic factor for patient management. Presently, endoscopic ultrasonography (EUS) is the most reliable method for assessing the primary tumor and evaluating T and N stage with high diagnostic rates. The accuracy of EUS for gastric cancer staging varies among different authors with ranges between 64.8% and 92% for T staging and 50% and 90% for N staging, with a few incidences of overstaging and understaging [Tsendsuren et al., 2006]. Multidetector CT provides relatively valuable results of T and N staging, including differentiation between T1a, T1b, and T2 gastric cancers [Lee et al., 2010]. The use of the combination of virtual gastroscopy and dynamic contrast-enhanced MPR images obtained at multi–detector row CT after air and water distention of the stomach can improve tumor detection rates as well as accuracy rates in T and N staging of gastric cancers [Chen et al., 2007]. Virtual gastroscopy from images obtained in air-distended stomach provides an excellent overview of abnormal mucosal lesions within the stomach lumen [Lee, 2000]. The technique is most helpful in the detection of type IIa, IIc, and III early gastric cancer mucosal lesions. These lesions are usually missed at CT due to absence of thickening of the gastric wall. At CT, positive nodes are identified on the basis of size, shape, and enhancement pattern. CT in general is relatively insensitive and also nonspecific for detecting nodal metastases due to its inability to detect microscopic nodal invasion, which is common in gastric cancer, and the presence of reactive nodes that may be greater than [Monig et al., 1999]. The role of FDG PET in the preoperative staging of gastric cancer is considered to be still uncertain but it is most useful in detecting advanced disease [Podoloff et al., 2007]. PET is not yet accepted because it cannot provide the exact T stage and N stage of trial