Diagnostic Performance of CT Colonography for the Detection of Colorectal Polyps

OBJECTIVE: To investigate the diagnostic value of CT colonography for the detection of colorectal polyps. MATERIALS AND METHODS: From December 2004 to December 2005, 399 patients underwent CT colonography and follow-up conventional colonoscopy. We excluded cases of advanced colorectal cancer. We retrospectively analyzed the CT colonography findings and follow-up conventional colonoscopy findings of 113 patients who had polyps more than 6 mm in diameter. Radiologists using 3D and 2D computer generated displays interpreted the CT colonography images. The colonoscopists were aware of the CT colonography findings before the procedure. RESULTS: CT colonography detected 132 polyps in 107 of the 113 patients and conventional colonoscopy detected 114 colorectal polyps more than 6 mm in diameter in 87 of the 113 patients. The sensitivity of CT colonography analyzed per polyp was 91% (41/45) for polyps more than 10 mm in diameter and 89% (101/114) for polyps more than 6 mm in diameter. Thirteen polyps were missed by CT colonography and were detected on follow-up conventional colonoscopy. CONCLUSION: CT colonography is a sensitive diagnostic tool for the detection of colorectal polyps and adequate bowel preparation, optimal bowel distention and clinical experience are needed to reduce the rate of missing appropriate lesions.

Pulmonary Complications in Renal Transplantation

PURPOSE: To evaluate the radiographic and CT findings of pulmonary complications other than pulmonary edema arising from renal transplantation. MATERIALS AND METHODS: Among 393 patients who had undergone renal transplantation at our hospital during a previous ten-year period, 23 with pulmonary complications other than pulmonary edema were included in this study. The complications involved were infection caused by CMV (n=6), bacteria (n=4), fungus (n=4), tuberculosis (n=2), varicella (n=1) or chlamydia (n=1), and malignancy involving lung cancer (n=4) or Kaposi's sarcoma (n=1). Two chest radiologists reviewed all images. RESULTS: The complications manifesting mainly as pulmonary nodules were lung cancer(4/4), tuberculosis (1/2), and Kaposi's sarcoma(1/1). Pulmonary consolidation was a main feature in bacterial infection(4/4), fungal infection(3/4), tuberculosis(1/2), chlamydial infection(1/1), and varicellar pneumonia(1/1). Ground-glass attenuation was a main CT feature in CMV pneumonia(4/6), and increased interstitial marking was a predominant radiographic feature in CMV pneumonia(2/6). CONCLUSION: The main radiologic features described above can be helpful for differential diagnosis of the pulmonary complications of renal transplantation.

Radiofrequency Thermal Ablation of Benign Cystic Lesion:An Experimental Pilot Study in a Porcine Gallbladder Model

PURPOSE: To determine whether radiofrequency thermal ablation can be used to treat benign cystic lesions in a porcine gallbladder model. MATERIALS AND METHODS: This experimental study of radiofrequency thermal ablation involved the use of 15 exvivo porcine gallbladders and 15-G expandable needle electrodes. To investigate optimal temperature parame-ters,three groups of five were designated according to target temperature: Group A: 70 degrees C; Group B: 80 degrees C; Group C: 90 degrees C. After the target temperature was reached, ablation lasted for one minute. Gallbladder width, height and length were measured before and after ablation, and the estimated volume reduction ratios of the three groups were compared. Whether adjacent liver parenchyma around the gallbladder fossa was ablated by heat conducted from hot bile was also determined, and the thickness of the ablated area of the liver was measured. RESULTS: The volume reduction ratio in Group A, B and C was 42.7%, 41.7% and 42.9%, respectively (p>.05). In all 15 cases, gallbladder walls lost their transparency and elasticity at about 70 degrees C. In nine of ten cases in Groups B and C, the hepatic capsule around the gallbladder fossa was retracted at about 80 degrees C. The mean thickness of liver parenchymal damage adjacent to the gallbladder was 5.4 mm in Group B and 9.8 mm in Group C. In Group A livers, only one case showed minimal gradual parenchymal change. Microscopically, all three groups showed complete coagulation necrosis of the wall. CONCLUSION: On the basis of this feasibility study, radiofrequency thermal ablation is potentially suitable for the ultrasound-guided treatment of symptomatic cystic lesions including benign hepatic or renal cyst.

Radiofrequency Thermal Ablation of Malignant Hepatic Tumors: Post-Ablation Syndrome

PURPOSE: To evaluate post-ablation syndrome after radiofrequency thermal ablation of malignant hepatic tumors. MATERIALS AND METHODS: Forty-two patients with primary (n=29) or secondary (n=13) hepatic tumors under-went radiofrequency thermal ablation. A total of 65 nodules ranging in size from 1.1 to 5.0 (mean, 3.1) cm were treated percutaneously using a 50W RF generator with 15G expandable needle electrodes. We retrospec-tively evaluated the spectrum of post-ablation syndrome including pain, fever(> or =38 C degrees), nausea, vomiting, right shoulder pain, and chest discomfort according to frequency, intensity and duration, and the findings were cor-related with tumor location and number of ablations. We also evaluated changes in pre-/post-ablation serum aminotransferase(ALT/AST) and prothrombin time, and correlated these findings with the number of abla-tions. RESULTS: Post-ablation syndrome was noted in 29 of 42 patients (69.0%), and most symptoms improved with conservative treatment. The most important of these were abdominal pain (n=20, 47.6%), fever (n=8, 19.0%), and nausea (n=7, 16.7%), and four of 42 (9.5%) patients complained of severe pain. The abdominal pain lasted from 3 hours to 5.5 days (mean; 20.4 hours), the fever from 6 hours to 5 days (mean; 63.0 hours). and the nau-sea from 1 hour to 4 days (mean; 21.0 hours). Other symptoms were right shoulder pain (n=6, 14.3%), chest discomfort (n=3, 7.1%), and headache (n=3, 7.1%). Seventeen of 20 patients (85%) with abdominal pain had a subcapsular tumor of the liver. There was significant correlation between pain, location of the tumor, and number of ablations. After ablation, ALT/AST was elevated more than two-fold in 52.6%/73.7% of patients, respectively but there was no significant correlation with the number of ablation. CONCLUSION: Post-ablation syndrome is a frequent and tolerable post-procedural process after radiofrequency thermal ablation. The spectrum of this syndrome provides a useful guideline for the post-ablation management.

MR Findings of Bland and Proliferative Joint Effusion in Knee Joint

PURPOSE: To determine the MR imaging criteria by which bland and proliferative effusion of the knee may be differentiated. MATERIALS AND METHODS: We retrospectively reviewed the MR images of 64 patients (65cases), in whom T2-weighted sagittal scans revealed anteroposterior distension of the suprapatellar bursa of at least 0.5cm. The patients were divided into two groups: bland effusion (n=36) , and proliferative effusion [(n=29); pigmented villonodular synovitis (n=5), rheumatoid arthritis (n=6), septic arthritis (n=6), chronic synovitis (n=5), gouty arthritis (n=3), tuberculous arthritis (n=2), and lipoma arborescens (n=2)]. All conditions were diagnosed on the basis of operative data or clinical criteria. The knee joint space was divided into four compartments: the suprapatellar pouch, central zone, posterior femoral recess, and subpopliteal recess, and the amount and distribution of effusion was then compared between the two groups. The ratios of the width and the length of the lateral recess of the suprapatellar bursa to those of its medial recess were deter mined, and the findings for the two groups were compared. Abnormality of the intracapular fat pads (prefemoral fat, Hoffa 's fat, and quadriceps fat sign) as seen on sagittal scans, is a predictor proliferative effusion, and any such abnormality was evaluated. The synovium was classified as either thin or thick, and as having either a smooth or an irregular margin, as seen on Gadolinium-enhanced T1W1 images. RESULTS: As compared with bland effusion, proliferative effusion involved more prominent joint effusion in the suprapatellar pouch and posterior femoral recess, and in the suprapatellar bursa, the ratio of the width of the lateral recess to that of the medial recess was greater. When comparing the ratio of the length of the lateral recess to that of the medial recess, however, no significant statistical difference was noted. Sensitivity: specificity for proliferative effusion was 58%: 86% on coronal scan and 64%: 93% on axial scan at a threshold value of 0.7 (the ratio of the width). The prefemoral fat pad sign was 41% sensitive and 100% specific, while Hoffa 's fat pad sign had a sensitivity of 32% and a specificity of 95%. The corresponding figures for the quadriceps fat pad sign were 14% and 100%. The pattern of the synovium in bland effusion was thin and smooth in two, thick and smooth in one, and thin and irregular in one. In proliferative effusion, the pattern was thick and smooth in 11 cases, thin and irregular in four, and thick and irregular in 14. CONCLUSION: In proliferative effusion, the synovium tended to be thick and irregular. Proliferative effusion demonstrated greater predilection for the suprapatellar pouch, especially the lateral recess, and posterior femoral recess, than did bland effusion. Difference in the distribution of joint effusion effectively predict both proliferative effusion as well as intracapsular fat pad signs.