Gastric morphological changes of MRI and CT signs are similar can be expressed as gastric wall thickening, mass, ulcer and ring dikes, stomach stiff, narrow, and changes in mucosal Pei wrinkles, the difference is more diverse means of MRI examination can be to include the axial, coronal, sagittal and stomach and other multi-dimensional long-axis scan, which showed the lesion more objective form. At the same time, MRI can also be a virtual endoscopic gastric (MRVE) imaging, to achieve full stomach observe the internal morphology. According to scanning signal characteristics of gastric cancer vary sequence, plain is generally in the SE, such as signal T1WI, FSPGR T1WI sequences mostly low or equal signal, SSFSET2WI and FIESTA sequences usually presents, etc., or inhomogeneous high signal.
MRI signs of cancer of the introduction, gastric signal and the signal difference between the normal gastric wall, on the stomach wall and the mucous membrane that change alone is insufficient to make the diagnosis of patients has important significance, but also help determine tumor site, T stage correctly . Sohn (2000), etc. that enhance the detection and staging for gastric cancer is not meaningful, because the enhanced instead of "blurred the boundaries of the tumor." However, most scholars believe that the enhanced scan is very significant. After intravenous injection of contrast medium, the majority of gastric cancer was high relative to normal gastric wall enhancement, enhancement patterns may have a variety of performance, the more common, there are two, one for early enhancement of normal gastric wall more than 90s after the injection of contrast agent, gastric mucosa peak enhancement, and peak enhancement of gastric mucosa in advance, in increased early (30 – 90s); the other is to strengthen the performance of the degree of gastric cancer continued to increase, to the interstitial peak period, with the strengthening phase delay , gastric cancer and normal contrast between the more and more evident. We found that some enhanced scan LAVA relatively low enhancement of gastric cancer. Enhancement pattern of cancer may be affected by the diversity we consider the pathological types of cancer, strengthen the scanning phase sequence and take other factors. But no matter how the enhancement patterns of cancer, adjacent normal gastric wall with there will always be differences in the signal, so the multi-phase dynamic scanning of gastric cancer, the scan can not determine the lesion is necessary for those cases or the.
MRI signs of gastric introduction diagnostic accuracy of MRI in early gastric cancer reported each vary greatly, from 13% (Sohn, 2000) to 75% (Ka ton, 2000) range, consider the type of cancer, MRI of the I or E-type early cancer diagnosis accuracy, but to the lIb-type early cancer diagnosis is difficult, at present there is no experience to follow.
Advanced gastric cancer MRI can better show the size, shape, and the range of three-dimensional measurement of invasive disease. According to type was different, as local thickening of the stomach or mass protruding (Borrmann1 type), gastric wall thickening with the limitations of ulcerative (Borrmann 2 type), diffuse thickening with ulcer (Borrmann 3 type), and stomach broad diffuse gastric wall thickening with narrow stiff (Borrmann 4 type). Diagnosis requires shaft, crown, sagittal joint application to fully demonstrate ulcerative form, objective evaluation of pancreatic cancer and the relationship between and adjacent large blood vessels, easy stages. Diagnosis requires the examination and the patient should be based on the extent and condition of choice with a variety of sequences combined. For Borrmann 3 type gastric cancer to determine the border, MRI scan multi-phase enhanced CT more than superiority, and can be different according to the signal to distinguish between the normal gastric wall.
MRI evaluation of stomach cancer on infiltration along the stomach wall, Kang noted that when the cancer and other gastric mucosa adjacent to a long T2 signal enhancement with the MRI scan has strengthened, there is the possibility of tumor invasion, and put forward in order to determine the scope of violations of cancer; However, Cho and other studies suggest that this band through the CT as mucosal edema or lower reactivity due to fat deposition, our study found that some cancer enhanced scan is not adjacent to the submucosal layer thickening enhancement, and the scan showed a fat suppression low signal, it still can not change except for some of the potential for the reaction. Borrmann 4 type cancer, because of its desmoplastic (desmoplastic) features, are often in the T2WI was low relative to the normal gastric wall signal enhancement after intravenous injection of contrast medium and lower levels, attention should be identified.
MRI signs of gastric introduced, with the MRI imaging technology, accurate staging of gastric cancer rates in recent years has obviously improved. T staging accuracy of research reports has reached 70% – 90%. Gastric spiral CT and fast breath-hold MRI sequence comparison studies have shown, MRI for T staging accuracy (73%, wowen81%) has been higher than CT (66% -73%); and N staging MRI (55 % – 65%) and CT (58% – 73%) roughly equal. Dynamic contrast enhanced subtraction images can distinguish the stomach of 2-3 layers, T staging accuracy of up to 88%.