الفهرس 
Anatomy of stomachOnly 14 pages are availabe for public view
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Abstract
Actually, recent advances in CT technology and 3D imaging software have sparked renewed interest in the imaging of the gastrointestinal tract and multidetector CT has offered several potential advantages over single–section techniques; these advantages include faster data acquisition, greater anatomic coverage and comparable coverage times with much thinner section collimation together with better resolution.
Overall, incidence and mortality from gastric carcinoma have been steadily declining over the last few decades, but it remains one of the leading causes of cancer death worldwide, with a relative increase in incidence of proximal and cardial lesions.
Endoscopy and double contrast barium examination of the upper gastrointestinal tract are still the basic investigational tool for diagnosing the gastric cancer patient. However, they are exclusively based on depiction of the gastric mucosa and are limited by their inherent inability to evaluate transmural and extraserosal extension of disease. This means that they are unsuitable for T-staging according to the TNM system.
Endoscopic Ultrasonography (EUS) and computed tomography (CT) are often used for preoperative image modalities in staging gastric carcinoma. EUS was superior to CT in T staging (as it can detect the gastric wall with five layers of its internal structures) and perigastric lymph node evaluation in previous studies. However, it cannot be used for nodal staging beyond the first dimension of nodes, peritoneal dissemination and liver metastasis due to diminution of the field of view and it is operator dependant. Recently, fast scanning with rapid infusion of IV contrast medium administration (Dynamic CT) and filling the stomach with a large amount of low-density fluid have been used to overcome the limitations of conventional CT in the evaluation of the transmural and extraserosal spread of disease with rates of accuracy of 65-78% in T staging and 48-78% in N staging. It also does not interfere with 3D imaging and CT angiography.
Some authors have supported the use of laparoscopy, however, it can not be routinely done owing to its invasive nature.
The spiral CT technique is limited due to the partial-volume averaging effects in areas scanned obliquely. A comparative study between fast MR imaging compared with helical CT in gastric cancer staging found similar accuracies for T and N staging. Another study showed low detectability of early gastric cancers (EGCs) using MR imaging due to problems with spatial resolution. However MR imaging is more expensive than CT and not as widely available.
Multidetector row CT (MDCT) is a potentially powerful tool for noninvasive gastric evaluation. When thin collimation is used, near-isotropic imaging of the stomach is possible, allowing high quality multiplanar reformation (MPR) and three- dimensional (3D) ’’navigator’’ virtual gastroscopy (VG) scanning of the gastric images.
The combination of air and hydro-distension of the stomach along with dynamic contrast-enhanced MDCT with near-isotropic imaging offers improved diagnosis of a large variety of gastric disease.
Multidetector CT accurately define the group of patients for whom primary surgical therapy will not be suitable. If CT shows definitive transmural extension with peritoneal tumor spread, presurgical chemotherapy is used to down stage the tumor.
After completion of chemotherapy, restaging of the tumor will be performed. If there is a positive response to chemotherapy, curative surgical therapy will be attempted.
Therefore, preoperative staging of gastric cancer appears to be by far the main clinical indication.
In addition, multidetector CT plays an important role in evaluation of post operative complications and detection of tumor recurrence following partial gastrectomy.
Despite substantial advances introduced by MDCT technology, there are still several limitation including its inability to detect flat type of early gastric cancer (IIB) even in combination with VG and MPR images, also its overstaging in T2 cancers or understaging in T3 cancers. In addition to poor soft tissue contrast resolution of MDCT. Lastly it lacks reliable CT criteria for metastatic lymph nodes.
So, in conclusion MDCT with 3D imaging is an important diagnostic tool for suspected malignant lesions, post-operative tumor recurrence or residual lesions of gastric origin which should be considered, It is also important in the detection of the affected lymph nodes and extension into nearby organs and distant metastases.