Fiberoptic gastroscopy (FG) is generally regarded as a standard test for detection of gastric cancer. Upper gastrointestinal series (UGI), however, still represents a routine or survey examination for imaging gastric abnormalities although it has certain limitations in clinical use. Even though the application of conventional computed tomography (CT) in staging gastric carcinoma has been introduced, the results are unsatisfactory.
Recently, spiral CT, including various three-dimensional (3D) reconstructions such as virtual endoscopy and axial source images (2D) has been used in imaging the alimentary tract.
While most reports in literature laid emphasis on colon polyps there have been a few studies investigating gastric carcinoma with spiral CT In clinical practice, advanced gastric carcinoma is defined using Borrmann’s classification, which is the pathological basis for UGI diagnosis, and the resectability of the tumor and prognosis of the patients are evaluated presurgically using TNM staging which is one of the suggested applications of spiral CT.
In this study, 2D and 3D display techniques after spiral CT scan were cross-referenced. The role of this combined spiral CT technique was compared with that of UGI and FG in the detection and Borrmann’s classification of gastric carcinoma, which, to our knowledge, has not been reported in literature.The staging of gastric carcinoma with spiral CT was also correlated with histopathology.
CT Abdomen with contrast in patient history
During a 12-month period, 60 consecutive patients (36 males, 24 females) ranging from 27 to 79 years old (mean=62 a.), who were diagnosed of gastric carcinoma with FG and subsequent biopsy were recruited. Among the 60 gastric carcinoma patients, 43 were undertaken gastrectomy or subtotal gastrectomy, 17 were undertaken surgical exploration only because of severe adhesion between tumor and surrounding tissues. This study was approved by the administrative authority of the university hospital and fully informed consent was obtained from each patient. Within one week after FG procedure, UGI was performed prior to spiral CT scanning on each patient.
CT Abdomen with contrast was performed with a Hispeed CT/i scanner (General Electric Medical Systems, Milwaukee, WI). All patients were fasted for 12 hours. Before the CT scanning, 20 mg raceanisodamine hydrochloride was intramuscularly administered and two packs (6 g) of effervescent granules were taken orally. Usually patients were immediately placed on the scanning table in an oblique supine position. A scout projection was made to confirm the stomach to be distended by gas. If insufficient distention of stomach was found, half to one pack of effervescent granules was added and a scout projection was scanned again. Then, spiral CT was performed with a 3-mm collimation and a pitch of 1.2-1.5 mm during a single breathhold of 22-33 seconds, which produced a 3D-volume
acquisition that included the entire stomach. Tube current was 200-280 mA, voltage was 120 kVp and scan time was 1 second per rotation.
Barium double contrast technique with standard projection was used for UGI studies by an experienced radiologist. Standard FG examination was performed by an experienced gastrologist and the biopsy samples were processed as a clinical routine of pathology department.
Abdomen with contrast reconstruction
3D-postprocessing modes including CT virtual gastroscopy (CTVG), surface shaded display (SSD) and “Raysum” Display (virtual double contrast barium study) were performed by a built-in workstation (Advantage Window 2.0, General Electric Medical Systems, Milwaukee, WI) after raw data reconstruction with 1 mm interval. For intraluminal views of the stomach, a default level of -525 (Hounsfield unit, HU) provided by the Navigator (GE Company) was chosen. SSD and “Raysum” display were obtained with a threshold of -311HU.
CT Abdomen with contrast analysis
Sixty sets of hard copy of grayscale spiral CT images (including axial source images, CTVG, SSD, and “Raysum” display) and UGI radiograms from 60 patients were obtained by one radiologist and were randomly reviewed and scored with consensus by two other experienced radiologists who were blinded to clinical data, pathology, and the information of other imaging techniques. Video recording of FG examinations was reviewed and scored with consensus by two experienced gastrologists. The diagnostic confidence, appearance, location, and size of suspected lesions on images of spiral CT, UGI and FG wererecorded. For spiral CT, the observers made the final judgments after referring to all 4 techniques including CTVG, SSD, “Raysum” and axial source images. The lesions were then classified as early and advanced gastric carcinoma according to Borrmann’s classification. Based on spiral CT, TNM staging of gastric carcinoma of each case was also noted.
Diagnostic confidence for detecting a lesion was rated as 1, definitely no lesion; 2, probably not a lesion; 3, possible lesion; 4, probable lesion; 5, definite lesion. Any image artifacts that degraded diagnostic confidence were also noted. All findings of lesions with spiral CT, UGI and FG were further verified with the results of surgical exploration, dissected specimen and histology, which were used as the gold standard for detection, Borrmann’s classification and spiral CT staging of gastric carcinoma
CT Abdomen with contrast Statistical analysis
Data entry procedures and statistical analysis were performed with a statistical software package (SAS for windows, version 6.12, SAS Institute, Cary, NC). By using only those lesions allocated with confidence rate of 3 or higher, the sensitivity of detection and classification of gastric carcinomas of each technique was assessed (Chi-square test). Significant differences were considered when the P value was less than or equal to 0.05.
CT Abdomen with contrast Result
The classification, size and location of the gastric cancer in this study are summarized in below w complete set of image data of a patient is exemplified in Figure below.
CT Abdomen with contrast images A complete set of image data of a patient. Spiral CT images (A-D), fiberoptic gastroscopy (E), surgical specimen (F) and corresponding barium study (G) from a patient (female, 48 a.) of Borrmann’s type 2 and TNM stage 1 of advanced gastric carcinoma.
(A), axial image (supine position with right side elevated) showed a focal irregular protruding (arrow) from the posterior wall of antrum. (B), “Raysum” display (virtual double contrast barium study) stressed double-margin changes at the greater curvature of antrum: tumor (large arrow) and ulcer (small arrow) margins. (C), SSD image showed depression at the antrum with a central
ulcer (arrow). (D), CTVG image depicted an intraluminal irregular mass with a flat ulcer (arrow). The view angle was illustrated by the 2D image at lower right corner. (E), fiberoptic gastroscopic view showed a lobulated mass. (F), surgical specimen demon stratad a mass with a small central ulcer (arrow). (G), barium study revealed an intraluminal filling defect (arrows) with a flat ulcer (asterisk) at the greater curvature of antrum.