[MR imaging of gastric wall layers in vitro: correlation to thehistologic wall structure]

MRI of gastric carcinoma: Results of T and N-staging in an in vitro study

AIM: To determine the accuracy of 1.5-T magnetic resonance imaging (MRI) in the evaluation of gastric wall invasion and perigastric lymph node metastasis in gastric adenocarcinoma.

METHODS: Twenty resected gastric specimens containing 20 tumors were studied with a 1.5-T MR system using a commercial head surface coil. MR scanning was performed with a T1 weighted image (TR/TE = 500/20), and a T2 weighted image (TR/TE = 2500/90). MR findings were compared with pathologic findings.

RESULTS: A T1-weighted image demonstrated three layers in the normal gastric wall. All of the gastric tumors were well demonstrated by lesions and location. In a MRI findings of gastric wall invasion, there was 1 case of T1, 7 of T2, 11 of T3. Pathologic results of resected specimens included 3 cases of pT1, 4 of pT2, and 12 of pT3. The accuracy of T staging with MRI was 74% (14 of 19). MRI findings of lymph node metastasis included 6 cases of N0, 13 cases of N1. The accuracy of the N staging with MRI was 47% (9 of 19).

CONCLUSION: MRI has a high diagnostic accuracy in the evaluation of the T staging of gastric cancer in vitro and thus potentially enables preoperative histopathologic staging.

Magnetic resonance imaging for local staging of gastric carcinoma: results of an in vitro study

OBJECTIVE

Preoperative staging of gastric carcinoma is limited by the fact that available imaging modalities do not enable accurate evaluation of the depth of infiltration of the gastric wall. The aim of this study was to evaluate the efficiency of conventional magnetic resonance imaging (MRI) in local staging of gastric carcinoma.

METHODS

Sixty-five specimens of patients with proven gastric carcinoma were examined immediately after gastrectomy. Examination was performed with a 1-T MRI and included T1-weighted, T2-weighted, and opposed phase images. Images were analyzed for the number of visible wall layers and their signal intensity characteristics, for tumor localization and depth of infiltration. T-stage was classified according to the TNM system. Finally, the staging by MRI was compared with the histopathological staging of the specimens.

RESULTS

The mucosal, submucosal, and proper muscle layers could be differentiated by the typical signal intensities. Depiction of the subserosa or serosa was not possible. In 65 specimens, 67 carcinomas were found by the pathologist. Sixty-four of 67 (96%) histologically proven carcinomas were correctly localized by MRI; T-staging accuracy was 50% only, mainly because of overstaging pT2 tumors as T3.

CONCLUSIONS

MRI enables differentiation of gastric wall layers and, therefore, technically allows the evaluation of the local tumor stage of gastric carcinomas. However, infiltration of the subserosal and serosal layer cannot be proved accurately. Overstaging pT2 tumors is one of the most predominant problems. Yet further technical developments in high-resolution imaging of the gastric wall may improve T-staging in the near future and overcome today's staging limitations.

Radiologische Bildgebung des oberen Gastrointestinaltraktes

CT, and multi-detector row computed tomography in particular, play a very important role in staging malignant tumors of the stomach. The optimized technique of so called "Hydro-CT", including distension to the gastric wall with 1-1.5 l oral contrast media, mainly water, has fostered the diagnostic value of CT in the diagnosis of diseases of the stomach. By using the "Hydro-CT" technique, the detection rate for gastric carcinoma is now between 89% and 94%, and for liver metastasis between 85% and 92%. For overall T staging, the sensitivity is rather low at between 43% and 65%, and for the lymph nodes between 64 and 88%. Depending on tumor type, multislice computed tomography (MSCT) supplies morphological details for defining the type of lesion (polyps, gastritis, lymphoma, gastrointestinal stromal tumours, carcinoma). Nevertheless, a definite differential diagnosis remains difficult. In addition, multiplanar reconstruction (MPR), derived from multi-detector row computed tomography data sets, is very helpful in localizing these pathologies and demonstrating their anatomic relationship to adjacent organs and vascular structures. MRI plays no major part in the diagnostic evaluation of the upper GI-tract.

New coil concept for endoluminal MR imaging: initial results in staging of gastric carcinoma in correlation with histopathology

Our aim was to conduct a prospective study to evaluate staging accuracy of a new coil concept for endoluminal magnetic resonance imaging (MRI) on ex vivo gastric carcinomas. Twenty-eight consecutive patients referred to surgery with a clinically proven primary gastric malignancy were included. Surgical specimens were examined with a foldable and self-expanding loop coil (8-cm diameter) at 1.5 Tesla immediately after total gastrectomy. T1- and T2-weighted and opposed-phase sequences (axial, frontal sections; 3- to 4-mm slice thickness) were acquired. Investigators blinded to any patient information analyzed signal intensity of normal gastric wall, gastric tumor, and lymph nodes. Findings were compared with histopathological staging. On surgical specimens, 2-5 gastric wall layers could be visualized. All gastric tumors (26 carcinomas, two lymphomas) were identified on endoluminal MR data (100%). Overall accuracy for T staging was 75% (18/24); sensitivity to detect serosal involvement was 80% and specificity 89%. N staging correlated in 58% (14/24) with histopathology (N+ versus N-). The endoluminal coil concept is feasible and applicable for an ex vivo setting. Endoluminal MR data provided sufficient detail for gastric wall layer differentiation, and therefore, identification of T stages in gastric carcinoma is possible. Further investigations in in vivo settings should explore the potential of our coil concept for endoluminal MR imaging.

Magnetic Resonance Imaging Gastrography

OBJECTIVES

We sought to demonstrate the feasibility of depicting gastric tumors using magnetic resonance imaging (MRI) while applying the dark lumen technique. The findings were correlated with conventional gastroscopy. In addition, we evaluated the screening for lymph nodes and liver metastases during the same session to identify potential tumor spread.

MATERIALS AND METHODS

The study included 15 patients with known malignant gastric disease. Conventional gastrointestinal endoscopy was performed in all patients as gold standard. All patients were examined with computed tomography for tumor staging. MRI was performed using 1 L of tap water as oral contrast agent for all protocols. The MRI program included an axial T1-weighted (T1w; 2D-FLASH) sequence, an axial STIR and T2w (TSE) sequence, and 2 postcontrast T1w (3D coronal /2D axial FLASH) sequences using 0.2 mmol/kg gadolinium diethylenetriaminepenta-acetic acid as intravenously injected contrast agent. Qualitative analysis and comparison with conventional gastroscopy were performed.

RESULTS

The images obtained with the postcontrast 3D coronal T1w-FLASH sequence were the most suitable in identifying gastric tumors. Complete correlation with conventional gastroscopy was achieved in 80% of the cases and partial correlation in 13% of the cases. The same imaging sequence was also appropriate for the evaluation of lymph nodes. For the identification of liver metastases, the images obtained with the axial postcontrast T1w 2D-FLASH sequence provided a higher diagnostic confidence as compared with other imaging protocols.

CONCLUSIONS

Applying the dark lumen technique through MRI is suitable for imaging gastric tumors and has the potential to become a "one-stop shopping" method because of the possibility for lymph node evaluation and screening for metastases during the same session based on the same images.

MR Imaging of the Stomach: Potential Use for Mangafodipir Trisodium— A Study in Swine

PURPOSE

To evaluate mangafodipir trisodium as a potential contrast agent at magnetic resonance (MR) imaging of the stomach.

MATERIALS AND METHODS

Mangafodipir trisodium was injected intravenously into three swine at a dose of 5 micromol per kilogram of body weight. For comparison, gadopentetate dimeglumine was injected into three other swine at a dose of 0.1 mmol per kilogram of body weight. T1-weighted three-dimensional MR images were acquired in all six swine at 1.5 T before and approximately 10, 15, 20, 25, 30, and 40 minutes after contrast material administration. Extracted stomach specimens were imaged at 3.0 T. In vivo and ex vivo images were evaluated visually and quantitatively for contrast enhancement of the stomach, and in vivo images were evaluated for the presence of reflux from the duodenum.

RESULTS

Mangafodipir trisodium produced prolonged and selective enhancement of the inner surface of the stomach, in contrast to the more general enhancement seen with gadopentetate dimeglumine, and reflux from the duodenum could not account for this selective enhancement. Ex vivo images confirmed that T1 enhancement in the stomach wall with mangafodipir trisodium was limited to the inner surface. Gadopentetate dimeglumine did not produce selective enhancement of the inner surface of the stomach.

CONCLUSION

Mangafodipir trisodium preferentially enhances the inner surface of the stomach on MR images acquired in swine and, therefore, may have potential for use as a contrast agent at MR imaging of the human stomach.