Hoon Ji

Portal-venous gas unrelated to mesenteric ischemia

Abstract. The aim of this study was to report on 8 patients with all different non-ischemic etiologies for portal-venous gas and to discuss this rare entity and its potentially misleading CT findings in context with a review of the literature. The CT examinations of eight patients who presented with intrahepatic portal-venous gas, unrelated to bowel ischemia or infarction, were reviewed and compared with their medical records with special emphasis on the pathogenesis and clinical impact of portal-venous gas caused by non-ischemic conditions. The etiologies for portal-venous gas included: abdominal trauma (n=1); large gastric cancer (n=1); prior gastroscopic biopsy (n=1); prior hemicolectomy (n=1); graft-vs-host reaction (n=1); large paracolic abscess (n=1); mesenteric recurrence of ovarian cancer superinfected with clostridium septicum (n=1); and sepsis with Pseudomonas aeruginosa (n=1). The clinical outcome of all patients was determined by their underlying disease and not negatively influenced by the presence of portal-venous gas. Although the presence of portal-venous gas usually raises the suspicion of bowel ischemia and/or intestinal necrosis, this CT finding may be related to a variety of non-ischemic etiologies and pathogeneses as well. The knowledge about these conditions may help to avoid misinterpretation of CT findings, inappropriate clinical uncertainty and unnecessary surgery in certain cases.

Differentiation of chronic focal pancreatitis from pancreatic carcinoma by in vivo proton magnetic resonance spectroscopy

Objective: To determine the differences between the in vivo proton magnetic resonance spectroscopy (1H-MRS) features of chronic focal pancreatitis and pancreatic carcinoma and to evaluate the possibility of discriminating chronic focal pancreatitis from pancreatic carcinoma by analysis of in vivo 1H-MR spectra. Methods: The 1H-MR spectra from 36 human pancreases were evaluated in vivo. This series included 15 cases of chronic focal pancreatitis and 21 cases of pancreatic carcinoma. All cases were confirmed histopathologically after surgical resection. The ratios of the peak area (P) of all peaks at 1.6-4.1 ppm to lipid (0.9-1.6 ppm) (P [1.6-4.1 ppm]/P [0.9-1.6 ppm]) in the chronic focal pancreatitis and pancreatic carcinoma groups were evaluated, and the results were compared. The sensitivity and specificity of the analysis were also evaluated by in vivo 1H-MR spectra for discriminating between chronic focal pancreatitis and pancreatic carcinoma. Results: In vivo 1H-MR spectra showed significantly less lipid in chronic focal pancreatitis than in pancreatic carcinoma. The ratio of P (1.6-4.1 ppm)/P (0.9-1.6 ppm) in chronic focal pancreatitis was significantly higher than that in pancreatic carcinoma (P < 0.05) because of a decreased peak area of lipids. The means ± SDs of P (1.6-4.1 ppm)/P (0.9-1.6 ppm) in the chronic focal pancreatitis and pancreatic carcinoma groups were 2.78 ± 1.67 and 0.51 ± 0.49, respectively. Using a value of <2.5 as positive for pancreatic cancer, the sensitivity and the specificity for pancreatic cancer were 100% and 53.3%, respectively. Conclusion: Chronic focal pancreatitis and pancreatic carcinoma can be distinguished from each other by analysis of in vivo 1H-MR spectra, and in vivo 1H-MRS can be a useful method for making a differential diagnosis between chronic focal pancreatitis and pancreatic carcinoma.

Acute Small Bowel Ischemia: CT Imaging Findings

Small bowel ischemia is a disorder related to a variety of conditions resulting in interruption or reduction of the blood supply of the small intestine. It may present with various clinical and radiologic manifestations, and ranges pathologically from localized transient ischemia to catastrophic necrosis of the intestinal tract. The primary causes of insufficient blood flow to the small intestine are various and include thromboembolism (50% of cases), nonocclusive causes, bowel obstruction, neoplasms, vasculitis, abdominal inflammatory conditions, trauma, chemotherapy, radiation, and corrosive injury. Computed tomography (CT) can demonstrate changes because of ischemic bowel accurately, may be helpful in determining the primary cause of ischemia, and can demonstrate important coexistent findings or complications. However, common CT findings in acute small bowel ischemia are not specific and, therefore, it is often a combination of clinical, laboratory and radiologic signs that may lead to a correct diagnosis. Understanding the pathogenesis of various conditions leading to mesenteric ischemia and being familiar with the spectrum of diagnostic CT signs may help the radiologist recognize ischemic small bowel disease and avoid delayed diagnosis. The aim of this article is to provide a review of the pathogenesis and various causes of acute small bowel ischemia and to demonstrate the contribution of CT in the diagnosis of this complex disease.

Intra-patient Prone to Supine Colon Registration for Synchronized Virtual Colonoscopy

In this paper, we present an automated method for colon registration. The method uses dynamic programming to align data defined on colon center-line paths, as extracted from the prone and supine scans. This data may include information such as path length and curvature as well as descriptors of the shape and size of the colon near the path. We show how our colon registration technique can be used to produce synchronized fly-through or slice views.

Normal colonic wall thickness at CT and its relation to colonic distension

Purpose The purpose of this work was to analyze the relation between normal colonic wall thickness at CT and local colonic distension. Method One hundred consecutively acquired patients were included in our study. All patients were asymptomatic regarding their intestine, and their history was always negative for intestinal disease. All CT examinations were performed for other reasons than intestinal disease. Colonic wall thickness at CT was measured digitally in every patient at four locations and set in relation to the local colonic distension. Results The normal colonic wall thickness ranged from 0 to 2 mm in colonic segments with a diameter of ≥4–6 cm, from 0.2 to 2.5 mm in colonic segments with a diameter of 3–4 cm, from 0.3 to 4 mm in colonic segments with a diameter of 2–3 cm, and from 0.5 to 5 mm in colonic segments with a diameter of 1–2 cm. Maximal colonic wall thickness ranged up to 6 and 8 mm in the proximal and distal colon, respectively, if the measured colonic segment showed a luminal width of <1 cm according to contraction. Discussion The normal colonic wall thickness at CT should be regarded as a dynamic value that stays in clear relation to the local colonic distension. In contracted colonic segments, a colonic wall thickness of 6–8 mm may still be normal. On the other hand, a colonic wall measuring 5 and 3 mm should be regarded as thickened if found in colonic segments with a luminal width of >2 and 4 cm, respectively.

Multislice CT colonography: current status and limitations.

CT colonography (CTC) is a promising method for colorectal screening providing a full structural evaluation of the entire colon and gaining in popularity due to a superior safety profile, a low rate of complications, and high patient acceptance. Multislice CT (MSCT) has further improved the diagnostic potential of CTC by generating high-resolution CT images of the abdomen and pelvis in shorter acquisition times than was previously possible. Over the past year, multiple studies have been published on every aspect of CTC including techniques, image display, image reconstruction, and clinical trial results assessing the feasibility of CTC as a screening tool. Yet despite increasing clinical use, the appropriate role of CTC in colorectal cancer screening remains undefined and barriers to widespread adoption remain. In particular, though the test is generally regarded as easy to perform, accurate interpretation requires a steep learning curve. While several large studies have found high sensitivity and specificity, the accuracy of CTC in a screening population has yet to be verified and almost no health insurance plans reimburse for its use in colorectal screening. Ongoing research in computer-aided detection and new software tools, however, have the potential to increase accuracy and ease of interpretation significantly, accelerating its acceptance as a colorectal screening tool.

Computed tomography and magnetic resonance imaging of hepatic metastases.

The detection and characterization of liver metastases is well performed with either computed tomography or magnetic resonance imaging. The administration of intravenous contrast is essential for almost all indications, with multiphasic imaging aiding in lesion characterization and detection. The use of multidetected CT (MDCT) provides the ability for optimized vascular and multiplanar imaging, but has also resulted in increased examination complexity. Tissue-specific MR contrast agents can yield the highest rate of lesion detection and thus may be useful in presurgical planning.

Benign liver tumors

This article discusses the most important benign liver tumors, both in adult and pediatric patients. A pathologic discussion of each neoplasm is included to provide a basis for understanding the radiologic-pathologic correlation that is used throughout the monograph. The benign liver tumors are presented according to their frequency. Therefore, hemangioma, the most common primary benign liver neoplasm, is discussed first, followed by focal nodular hyperplasia, hepatocellular adenoma, and the benign primary pediatric tumors--infantile hemangioendothelioma and mesenchymal hamartoma. Finally, a brief discussion of nodular regenerative hyperplasia and other rare hepatic masses is included. Bile duct cyst (simple, non-parasitic cyst of the liver) is not included since it is not a neoplasm. Likewise, cystadenoma is not discussed since it originates from the biliary duct cell and is appropriately included in the biliary neoplasms category.

Magnetic resonance imaging: Liver-specific contrast agents

MR imaging with new liver-specific contrast agents will probably be the imaging modality used in the future to detect focal liver lesions. The detection of HCC will probably be improved by using specific hepatobiliary agents, but the exact technique remains to be determined. New liver-specific contrast can differentiate some benign lesions from malignant ones and can assist in making a final diagnosis. In certain circumstances, liver-specific contrast agents can be used to evaluate hepatic vessels, the biliary tract, and hepatic function. New applications are also expected.