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Table. Detection Rates for Identification of Hepatic Metastases Size of lesons Helical CT MRI Helical CT+ MRI < cm 8/28 (64) 8/28 (64) 023/28 (82)* 2 cm 26/33 (79) 28/33 (85) 28/33 (85) > 2 cm 30/3 (97) 29/3 (94) 03/3 (00) Total 74/92 (80) 75/92 (82) 82/92 (89) Note. -Numbers in parentheses are the percentages. * Corresponds to statistically significant difference (p = 0.036) by McNemar test. a b c Fig.. A 50-year-old woman with sigmoid colon cancer a. Helical CT scan during portal venous phase shows no definite focal lesion in the liver. b. T2- weighted MR image shows a tiny lesion with subtle high signal intensity in segment- of the liver (arrow). c. On Mn-DPDP enhanced T-weighted images, the lesion shows low signal intensity (arrow). The lesion was confirmed as metastasis at histopathologic examination. a b c Fig. 2. A 59-year-old man with sigmoid colon cancer. a. CT scan shows a hypoattenuating nodule (arrow) in segment of the liver. b. On Mn-DPDP enhanced MRI, the nodule is not defined. This nodule was missed on interpretation of MRI alone. c. On T2-weighted image, the nodule shows subtle high signal intensity. The lesion was confirmed as metastasis at histopathologic examination. - -
Table 3. Interobserver Variability in Confidence Ratings ( -values) Table 2. Mean Az Values for Each Imaging Technique for Differentiating Malignant lesions from Benign Lesions Size of lesions Helical CT MRI Helical CT+ MRI < cm 0.603 0.08 0.807 0.06 0.848 0.05 2 cm 0.807 0.06 0.883 0.05 0.92 0.04 > 2 cm 0.932 0.06 0.927 0.05 0.955 0.04 Note. Date are mean SD Statiscally significant difference (p<0.05) compared with CT Size of Lesions Helical CT MRI Helical CT+ MRI < cm 0.62 0.72 0.83 2 cm 0.82 0.9 0.93 > 2 cm 0.92 0.96 Note. -values 0 >, positive correlation; 0 0.4, positive but poor agreement; 0.4 0.75, good agreement; > 0.75,excellent agreement : consensus of opinions in all nodules a b Fig. 3. A 67-year-old man with sigmoid colon cancer a. Helical CT scan during portal phase shows two small hypoattenuating nodules that are too small to characterize in liver segment- and - (arrows). b. On T2-weighted image, segment lesions (arrows) in segment- show very high signal intensity suggesting hepatic cysts. However segment- lesion is not defined. c. On Mn-DPDP enhanced T-weighted images, segment- lesion (arrowhead) shows low signal intensity. The lesion in segment- VI was confirmed as metastasis at histopathologic examination. c - 2 -
Table 4. False Positive Rates Size of lesions Helical CT MRI Helical CT+ MRI < cm 5/53 (28) 5/53 (9) 3/53 (6) 2 cm 08/53 (5) 3/53 (6) 3/53 (6) 2 cm > 0/53 (0) 2/53 (4) 0/53 (0) Note. Numbers in parentheses are the percentage of patients with at least one false positive lesions. Statiscally significant difference (p<0.05) compared with MRI, CT-MRI a b c Fig. 4. A 58-year-old woman with rectal cancer (A) Mn-DPDP enhanced MRI shows a nodule with low signal intensity in segment of the liver (arrow), which is not defined on T2-weighted image (B). The lesion was interpreted as metastasis on interpretation of MRI alone. (C). On CT images, no focal lesion is seen in corresponding area. On combined CT-MRI reading, the lesion was correctly interpreted as artifact probably caused by partial volume averaging of an adjacent colon loop. - 3 -
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Preoperative Detection of Hepatic Metastases from the colorectal Cancers: Comparison of Dual-phase CT scan, Mn-DPDP enhanced MRI, and combination of CT and MRI Kyung Min Shin, M.D., Hun Kyu Ryeom, M.D., Jong Yeol Kim, M.D., Gyu Seok Choi, M.D. 2, Hye Jeong Kim, M.D., Jong Min Lee, M.D., Yongmin Chang, Ph.D., Yong Seon Kim, M.D., Duk Sik Kang, M.D. Department of Radiology, School of Medicine, Kyungpook National University 2 Department of Surgery, School of Medicine, Kyungpook National University Purpose : To determine the usefulness of additional Mn-DPDP MRI for preoperative evaluation of the patients with colorectal cancers by comparison of dual-phase CT scan, Mn-DPDP enhanced MRI and combination of CT and MRI. Materials and Methods : Fifty-three colorectal cancer patients with 92 metastatic nodules underwent dualphase (arterial and portal) helical CT scan and Mn-DPDP MRI prior to surgery. The indication of MRI was presence or suspected of having metastatic lesions at CT scan and/or increased serum carcinoembryonic antigen (CEA) levels (0 ng/ml or more). The diagnosis was established by the combination of findings at surgery, intraoperative ultrasonography, and histopathologic examination. Two radiologists interpreted CT, MRI, and combination of CT-MRI at discrete sessions and evaluated each lesion for location, size, and intrinsic characteristics. The lesions were divided into three groups according to their diameter; cm <, 2 cm, and > 2 cm. Diagnostic accuracy was evaluated using the alternative-free response receiver operating characteristic method. Detection and false positive rate were also evaluated. Results : In the lesions smaller than cm, detection rate of combined CT-MRI was superior to CT or MRI alone (82%, p = 0.036). The mean accuracy (Az values) of combined CT and MRI was significantly higher than that of CT in the lesions smaller than 2 cm ( cm <, p=0.034; 2 cm, p=0.045). However, there was no significant difference between MRI and combined CT-MRI. The false positive rate of CT was higher than those of combined CT-MR in the lesions smaller than cm (28 %, p=0.023). Conclusion : Additional MRI using Mn-DPDP besides routine CT scan was helpful in differentiating the hepatic lesions (< 2 cm) and could improve detection of the small hepatic metastases (< cm) from colorectal carcinoma. Index words : Liver neoplasms, CT Liver neoplasmamms, MR Magnetic resonance (MR), contrast media Address reprint requests to : Hun Kyu Ryeom, Department of Radiology, School of Medicine, Kyungpook National University 50, 2Ga, Samduk-dong, Jung-gu, Taegu 700-72, Korea. Tel. 82-53-420-5390 Fax. 82-53-422-2677 E-mail: hkryeom@knu.ac.kr - 6 -