Observer accuracy in the detection of pulmonary nodules on CT: effect of cine frame rate.

AIM: To assess the effect of cine frame rate on the accuracy of the detection of pulmonary nodules at computed tomography (CT). MATERIALS AND METHODS: CT images of 15 consecutive patients with (n = 13) or without (n = 2) pulmonary metastases were identified. Initial assessment by two thoracic radiologists provided the "actual" or reference reading. Subsequently, 10 radiologists [board certified radiologists (n = 4) or radiology residents (n = 6)] used different fixed cine frame rates for nodule detection. Within-subjects analysis of variance (ANOVA) was used to evaluate the data. RESULTS: Eighty-nine nodules were identified by the thoracic radiologists (median 8, range 0-29 per patient; median diameter 9 mm, range 4-40 mm). There was a non-statistically significant trend to reduced accuracy at higher frame rates (p=0.113) with no statistically significant difference between experienced observers and residents (p = 0.79). CONCLUSION: The accuracy of pulmonary nodule detection at higher cine frame rates is reduced, unrelated to observer experience.

Characterization of focal hepatic lesions with ferumoxides-enhanced T2-weighted MR imaging.

OBJECTIVE: The purpose of this study was to evaluate whether ferumoxides-enhanced MR imaging of focal hepatic lesions provides distinctive signal intensity and lesion-to-liver contrast changes for benign and malignant lesions, helping to further characterize and differentiate these lesions. MATERIALS AND METHODS: Data analysis was performed on 70 patients, with previously identified focal hepatic lesions, who underwent MR imaging of the liver before and after IV administration of ferumoxides (10 micromol Fe/kg). Lesions analyzed with pathologically proven diagnoses included metastases (n = 40), hepatocellular carcinoma (n = 11), cholangiocarcinoma (n = 6), hemangioma (n = 4), focal nodular hyperplasia (n = 6), and hepatocellular adenoma (n = 3). Response variables measured and statistically compared included the percentage of signal-intensity change and lesion-to-liver contrast. RESULTS: Focal nodular hyperplasia showed significant signal intensity loss on ferumoxides-enhanced T2-weighted images (mean, -43%+/-6.7%, p < 0.01). All other lesion groups showed no statistically significant change in signal intensity on ferumoxides-enhanced T2-weighted images, although signal intensity loss was seen in some individual hepatocellular adenomas (mean, -6.6%+/-24.0%) and hepatocellular carcinomas (mean, -3.3%+/-10.3%). All lesions, with the exception of hepatocellular carcinoma, had a marked increase in lesion-to-liver contrast on ferumoxides-enhanced T2-weighted images, which was statistically significant for metastases and hemangioma (p < 0.02). CONCLUSION: Focal nodular hyperplasia shows significant decrease in signal intensity on ferumoxides-enhanced T2-weighted images, which may aid in the differentiation of focal nodular hyperplasia from other focal hepatic lesions. Other lesions, namely, hepatocellular adenoma and carcinoma, can have reticuloendothelial uptake, but usually to a lesser degree than that of focal nodular hyperplasia.

The Rocky liver: radiologic-pathologic correlation of calcified hepatic masses.

Although relatively uncommon in daily clinical practice, calcification may be found in inflammatory hepatic lesions and in benign and malignant liver neoplasms. The most common source of calcified hepatic lesions is inflammatory conditions such as granulomatous diseases (e.g., tuberculosis). The calcification typically involves the entire lesion and appears as a dense mass that can produce artifacts on computed tomographic (CT) scans. Echinococcus cysts have curvilinear or ring calcification. Hemangiomas, especially large ones, may contain large, coarse calcifications that are centrally located in areas of fibrosis; these may be seen at CT (20% of cases) or radiography (10%). In hepatocellular adenoma, calcifications may be solitary or multiple and are usually located eccentrically within a complex heterogeneous mass. Calcifications in fibrolamellar carcinoma have been reported in 15%-25% of cases at CT and occur in a wide variety of patterns. Calcifications in intrahepatic cholangiocarcinoma are typically accompanied by a desmoplastic reaction and are visible at CT in about 18% of cases. Calcified hepatic metastases are most frequently associated with mucin-producing neoplasms such as colon carcinoma. Knowledge of the pathologic features of each entity helps radiologists to better recognize the shape, size, density, number, location, and distribution of hepatic calcifications seen on images and to narrow the differential diagnosis.

Hepatic metastases.

Developments in ultrasound, CT scan, and MR imaging have increased our ability to detect and characterize focal liver lesions. Advances in the medical and surgical treatment of secondary liver tumors have continued to challenge these advances in radiology. A successful outcome depends on knowledge of the size and location of the tumor burden, and accurate radiologic assessment is crucial to identify those subgroups who may benefit from surgery and to prevent unnecessary radical surgery in those likely to gain only a short-term benefit.

Hepatic calcification.

Although a specific diagnosis of the calcified liver mass may not always be possible, there are some morphologic imaging features that help to indicate the diagnosis (Table 1). The radiologist needs to be aware of the wide spectrum of diseases of the liver that can calcify, and the most common causes. Pathologic correlation with axial imaging has greatly enhanced our understanding and interpretation of the underlying liver lesion, which may help to differentiate benign from malignant etiology.

MRI of the rectum: non-neoplastic disease.

The rectum has become the most successful area of the gastrointestinal tract to be studied with MRI. Its anatomical location, fixed in the pelvic fat, and its lack of peristalsis, make it an ideal organ to be scanned with MRI. In addition, MRI allows a direct sagittal and coronal display, of key importance to colorectal surgeons whose terminology and approach are based on the coronal plane. The sagittal plane allows the depiction of the relation of the rectum to the sacrum, uterus and prostate, with detail not available by other imaging techniques, and the use of endorectal coils allows excellent demonstration of the rectal wall. Although MRI has been used primarily to study rectal carcinoma, other diseases, congenital, inflammatory and vascular in origin, can be studied using the correct technique.

Hepatic metastases: computed tomography versus magnetic resonance imaging in 1997.

The developments in computed tomography (CT) and magnetic resonance (MR) imaging that have taken place over the last two decades have dramatically increased our ability to detect and characterize focal liver lesions, and have led to the liver becoming the primary focus of interest in abdominal imaging. At the same time, advances in the medical and surgical treatment of secondary liver tumors have continued to be a challenge to these advances in radiology. It is clear that a successful outcome depends on knowledge of the size and location of the tumor burden, and accurate radiological assessment is crucial in identifying the subgroups of patients who may benefit from surgery and, at the same time, in preventing unnecessary radical surgery, with its high morbidity, in those likely to gain only a short-term benefit. The current period of limited resources, along with increased awareness of the effects of ionizing radiation, has led to competition between the two modalities, with considerable debate as to which offers the better noninvasive examination of the liver, particularly with regard to the detection and characterization of focal liver lesions. Arguments over each method's relative merits have tended to be overstated, but the parallel use of different diagnostic techniques is costly and inefficient. Each needs to be placed in an appropriate position on diagnostic pathways.

MR imaging of the liver--a practical approach.

Clinical information must be combined with radiologic features to evaluate focal or diffuse liver disease effectively, and MR examinations need to be tailored appropriately. If there are characteristic radiologic findings, in many cases a correct diagnosis is possible; however, radiologic methods may provide an exact description of disease extent, vascular supply, infiltration, metastases, and tumor changes like necrosis or hemorrhage, without providing a definitive diagnosis. In these situations interventional radiologic techniques (such as percutaneous biopsy) have a potential role in diagnosis.

Low density barium and bentonite mixture versus high density barium: a comparative study to optimize negative gastrointestinal contrast agents for MRI.

The purpose of this study was to compare the patient tolerance and efficacy, as magnetic resonance imaging negative oral contrast agents, of a mixture of clay compound bentonite and low density barium sulfate suspension with that of higher density barium sulfate. Twenty patients were randomized into two groups: 10 patients receiving a mixture of low concentration 60% w/v barium sulfate plus 2.5% w/v bentonite, and 10 patients receiving 220% w/v barium sulfate Liuqid-HD (E-Z-EM, Westbury, NY). Post-contrast Spin-echo (SE) T1- and T2-weighted images (WI) were obtained on a 1.0T magnet. Two independent readers scored the overall intraluminal signal intensity and delineation of the gastrointestinal tract and adjacent organs. Patient acceptance was evaluated via a short questionnaire, by recording spontaneous comments and documenting the quantity of contrast agent ingested. There was greater intraluminal bowel signal reduction and organ delineation with 220% w/v barium than with the barium-bentonite mixture on both SE T1WI (p = 0.03) and SE T2WI (p = 0.42). With both agents there was greater signal reduction on SE T2WI than SE T1WI. Higher scores for organ delineation for both contrast agents were seen with SE T1WI. With 220% w/v barium, there was significantly better delineation of the pancreatic body (p = 0.02) and pancreatic tail (p = 0.02) on T1WI compared with SE T2WI. With the barium-bentonite mixture, SE T1WI showed improved delineation of jejunum compared with SE T2WI (p = 0.03). There were no statistically significant differences between the volume of contrast ingested in the two groups. Abdominal cramps were recorded for one patient in each group. These results suggest that barium-bentonite mixture, although useful as a negative gastro-intestinal contrast agent, is not as effective as 220% w/v barium. Further studies with a larger patient population and concentration optimization studies are needed.

Developmental intrahepatic shunts of childhood: radiological features and management.

The purpose of this study was to evaluate the role of radiological techniques in the diagnosis and management of developmental intrahepatic shunts. Hepatic vascular fistulae are recognised sequelae of liver trauma and intrahepatic tumours. However, there are rare developmental malformations which may present in childhood or later life and which may carry life-threatening complications. Retrospective analysis of clinical and radiological data was carried out in 24 patients. Anomalies evaluated were: (a) direct communication between hepatic artery and hepatic veins; (b) congenital hepatoportal arteriovenous malformations; and (c) congenital portocaval anastomosis with persistent flow through the ductus venosus. Although rare, the prompt recognition of these vascular anomalies allows early surgical or radiological intervention and reversal of the haemodynamic complications.

MRI of the gastrointestinal tract.

This article reviews the application of magnetic resonance imaging (MRI) to study the gastrointestinal (GI) tract. A summary of the current MRI techniques is included, emphasizing the choice of pulsing sequences, imaging plane, surface coils and intravenous and oral contrast agents for each of the different segments of the GI tract. The multiple available oral contrast agents are reviewed, including the role of both positive and negative. Finally, the major clinical applications of MRI in the GI tract are discussed by major disease categories (congenital abnormalities, inflammatory disease and benign and malignant neoplasms). The latter is further subdivided by GI tract segments such as esophagus, stomach, small bowel and colon.