Contrast Material-enhanced Computed Tomography Research Articles

Recurrent Ovarian Cancer: Use of Contrast-enhanced CT and PET/CT to Accurately Localize Tumor Recurrence and to Predict Patients’ Survival

To compare accuracy and interobserver variability in the detection and localization of recurrent ovarian cancer with contrast material-enhanced (CE) computed tomography (CT) and positron emission tomography (PET)/CT and determine whether imaging findings can be used to predict survival. Waiving informed consent, the institutional review board approved this HIPAA-compliant, retrospective study of 35 women (median age, 54.4 years) with histopathologically proven recurrent ovarian carcinoma who underwent CE CT and PET/CT before exploratory surgery. All CE CT and PET/CT scans were independently analyzed. Tumor presence, number of lesions, and the size and maximum standardized uptake value (SUV(max)) of the largest lesion were recorded for patient and region. Surgical histopathologic findings constituted the reference standard. Areas under the receiver operating characteristic curves (AUCs), κ statistics, and hazard ratios were calculated. Readers' AUCs in detection of recurrence for region were 0.85 (95% confidence interval [CI]: 0.81, 0.90) and 0.78 (95% CI: 0.72, 0.83) for CE CT and 0.84 (95% CI: 0.79, 0.89) and 0.74 (95% CI: 0.67, 0.81) for PET/CT (P = .76); 12 patients died. At PET/CT, size, number, and SUV(max) of peritoneal deposits were significantly associated with poor survival for readers 1 and 2 (P ≤ .01and ≤ .05, respectively), as were long- and short-axis diameters, number, and SUV(max) of distant lymph nodes for reader 1 (P ≤ .001). With CE CT, size (reader 1) and number (readers 1 and 3) of peritoneal deposits were significantly associated with poor survival (P ≤ .01), as were long- and short-axis diameters and number of distant lymph nodes for reader 1 (P ≤ .01). Interobserver agreement ranged from fair (patient, κ = 0.30) to moderate (region, κ = 0.55) for CE CT and fair (patient, κ = 0.24) to substantial (region, κ = 0.63) for PET/CT. Preliminary data suggest that CE CT and PET/CT may have similar accuracy in detection of recurrent ovarian cancer. Tumor size, number, and SUV(max) may have potential as prognostic biomarkers for patients with recurrent ovarian cancer.

Visually Isoattenuating Pancreatic Adenocarcinoma at Dynamic-Enhanced CT: Frequency, Clinical and Pathologic Characteristics, and Diagnosis at Imaging Examinations

To retrospectively determine the frequency, clinical and pathologic characteristics, and computed tomographic (CT) findings of visually isoattenuating pancreatic adenocarcinomas and to investigate the utility of magnetic resonance (MR) imaging and positron emission tomography (PET)/CT for detecting them. Institutional review board approval was obtained. Patient informed consent was waived. Of 743 consecutive patients with pathologically proved pancreatic cancer, 644 patients (392 men, 252 women; mean age, 60 years ± 9.5 [standard deviation]) who had undergone both arterial and portal phase contrast material-enhanced CT were included. Visually isoattenuating pancreatic adenocarcinoma was defined as lesion isoattenuation in both scan phases. Serum levels of carbohydrate antigen 19-9, immunoglobulin G (IgG), and IgG fraction 4 (IgG4), survival after curative-intent surgery; and pathologic findings of visually isoattenuating pancreatic adenocarcinomas were analyzed. CT findings of visually isoattenuating pancreatic adenocarcinomas and the sensitivity of MR imaging and PET/CT for detecting them were determined. The frequency of visually isoattenuating pancreatic adenocarcinomas among pancreatic cancers was 5.4% (35 of 644). Serum levels of carbohydrate antigen 19-9, IgG, and IgG4 were elevated in 51.5% (17 of 33), 8.3% (one of 12), and 8.3% (one of 12) of patients, respectively. Visually isoattenuating pancreatic adenocarcinoma, compared with usual pancreatic adenocarcinoma, was independently associated with a better survival after curative-intent surgery: Adjusted hazard ratio was 0.430 (P = .006). Thirty surgically resected visually isoattenuating pancreatic adenocarcinomas were 1.5-4 cm (median, 3 cm). Their pathologic findings differed from those of usual pancreatic adenocarcinomas: lower tumor cellularity, more frequent intratumoral acinar tissue and islet cells, and less prominent tumor necrosis. Visually isoattenuating pancreatic adenocarcinomas showed various abnormalities at CT, which may suggest an isoattenuating mass or nodule. Sensitivities of MR imaging and PET/CT were 79.2% (19 of 24) and 73.7% (14 of 19), respectively. Visually isoattenuating pancreatic adenocarcinoma represents a small but meaningful subset of pancreatic cancer and has characteristic clinical and pathologic features. MR imaging and PET/CT may be useful as subsequent examinations when the patient is suspected of having the lesion at CT.

Distinguishing Hypervascular Pseudolesions of the Liver from Hypervascular Hepatocellular Carcinomas with Gadoxetic Acid–enhanced MR Imaging

To retrospectively determine findings at gadoxetic acid-enhanced magnetic resonance (MR) imaging in hypervascular pseudolesions that were observed at computed tomography (CT) during hepatic arteriography, with special focus on distinguishing these pseudolesions from hypervascular hepatocellular carcinomas (HCCs). The institute ethics committee deemed study approval unnecessary. The study population comprised 80 patients (55 men, 25 women) with chronic liver disease who underwent CT during hepatic arteriography and arterial portography, gadoxetic acid-enhanced MR imaging, and follow-up dynamic contrast material-enhanced CT. The diagnosis of 104 pseudolesions and 123 HCCs was confirmed by means of histopathologic or multimodality evaluation. Two radiologists assessed the MR imaging findings of HCCs and pseudolesions in consensus, including the signal intensities (SIs) of the lesions on T2-weighted, diffusion-weighted (DW), and contrast-enhanced hepatocyte-phase images. The findings of nodular pseudolesions and HCCs were compared with the Fisher exact test. Additionally, the hepatocyte-phase SI ratio (ratio of lesion SI to liver SI) for HCCs and pseudolesions was compared by means of the Mann-Whitney U test. There were 62 wedge-shaped, 32 nodular, and 10 linear pseudolesions. On gadoxetic acid-enhanced hepatocyte-phase MR images, 15% of pseudolesions (16 of 104) were hypointense compared with surrounding liver tissue. The mean hepatocyte-phase SI ratio of HCCs (0.65 +/- 0.14 [standard deviation]) was significantly lower (P < .01) than that of the nodular pseudolesions (0.95 +/- 0.11). The optimal cutoff value of hepatocyte-phase SI ratio for distinguishing between HCC and nodular pseudolesion was 0.84. No nodular pseudolesions were visible on DW images. Gadoxetic acid-enhanced hepatocyte-phase MR imaging and DW imaging could be used to distinguish hypervascular pseudolesions from hypervascular HCCs; a hepatocyte-phase SI ratio below 0.84 and visibility on DW images were findings specific for HCCs rather than pseudolesions.

A Method for Reconstructing the Arterial Input Function during Helical CT: Implications for Myocardial Perfusion Distribution Imaging

To determine if a multidetector computed tomographic (CT) image acquisition and analysis method can enable accurate measurement of the arterial input function (AIF) during first-pass adenosine stress helical multidetector CT angiography and to test the effect of using this method on the semiquantitative assessment of myocardial perfusion distribution. The animal care and use committee of Johns Hopkins University approved the use of all procedures. The AIF was reconstructed by using a combination of bolus-tracking and time-registered helical multidetector CT data. After the AIF reconstruction method was validated in healthy animals, coronary stenosis was induced in seven dogs and contrast material-enhanced multidetector CT was performed during adenosine infusion (0.14-0.21 mg per kilogram of body weight per minute). Myocardial attenuation density (AD) parameters normalized to portions of the AIF were compared with microsphere myocardial blood flow (MBF) measurements at linear regression analysis. There was no significant difference between the area under the curve (AUC) for dynamic multidetector CT-derived AIF (3108 + or - 1250 [standard deviation]) and that for combined bolus-tracking and time-registered multidetector helical CT-derived AIF (3086 + or - 941) (P = .90). When AIF analysis was applied to helical multidetector CT myocardial perfusion measurements, the correlation between MBF and mean myocardial AD normalized to the AUC for the entire AIF was significant (R(2) = 0.82, P <.001). Myocardial AD normalized to the AUC for the AIF measured during helical multidetector CT correlated best with MBF (R(2) = 0.86, P <.001). The combination of bolus tracking and time-registered helical imaging enables reconstruction of the AIF during multidetector CT perfusion imaging. The helical CT AIF can be used to improve the semiquantitative assessment of myocardial perfusion distribution.

Endovascular Abdominal Aortic Aneurysm Repair: Nonenhanced Volumetric CT for Follow-up

To evaluate the clinical usefulness of volumetric analysis at nonenhanced computed tomography (CT) as the sole method with which to follow up endovascular abdominal aortic aneurysm repair (EVAR) and to identify endoleaks causing more than 2% volumetric increase from the previous volume determination. The study had institutional review board approval. Images were reviewed retrospectively in a HIPAA-compliant manner for 230 CT studies in 70 patients (11 women, 59 men; mean age, 74 years) who underwent EVAR. The scannning protocol consisted of three steps: (a) contrast material-enhanced CT angiography before endovascular stent placement, (b) contrast-enhanced CT angiography 0-3 months after repair to depict immediate complications, and (c) nonenhanced CT at 3, 6, and 12 months after repair. At each follow-up visit, immediate aortic volume analysis was performed. If the interval volumetric change was 2% or less, no further imaging was performed. If the volume increased by more than 2% on the nonenhanced CT image, contrast-enhanced CT angiography was performed immediately to identify the suspected endoleak. Confidence intervals (CIs) were obtained by using bootstrapping to account for repeated measurements in the same patients. Mean volume decrease was -3.2% (95% CI: -4.7%, -1.9%) in intervals without occurrence of a clinically relevant endoleak (n = 183). Types I and III high-pressure endoleaks (n = 10) showed a 10.0% (95% CI: 5.0%, 18.2%) interval volumetric increase. Type II low-pressure endoleaks (n = 37) showed a 5.4% (95% CI: 4.6%, 6.2%) interval volumetric increase. Endoleaks associated with minimal aortic volume increase of less than 2% did not require any intervention. This protocol reduced radiation exposure by approximately 57%-82% in an average-sized patient. Serial volumetric analysis of aortic aneurysm with nonenhanced CT serves as an adequate screening test for endoleak, causing volumetric increase of more than 2% from the volume seen at the previous examination.

Pulmonary Embolism Detection with Dual-Energy CT: Experimental Study of Dual-Source CT in Rabbits

To evaluate feasibility and added value of dual-energy computed tomography (CT) in diagnosis of pulmonary embolism (PE). This institutional animal experimental committee-approved study was performed in accordance with animal care guidelines. Eight New Zealand rabbits underwent standard unenhanced and contrast material-enhanced dual-source CT. Gelatin sponge particles were injected into the pulmonary artery, and rabbits underwent contrast-enhanced dual-source CT pulmonary angiography, from which blood-flow (BF) and fusion images were created. Immediately after dual-source CT, rabbits were sacrificed, their lungs were removed and fixed in 10% formalin, and detailed pathologic determination of location and number of lung lobes with PE was performed. Two rabbits were excluded: One died during the procedure. In the other, the catheter tip was retained in the left inferior pulmonary artery. This caused marked postembolization CT image artifacts in adjacent regions. Six rabbits were included in final analysis. Two radiologists without knowledge of pathologic results evaluated five pulmonary lobes in each rabbit and recorded whether PE was present. Pathologic results served as the reference standard. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the techniques were calculated. Weighted kappa values were calculated to evaluate agreement between modalities. Pathologic analysis revealed PE in 18 of 30 pulmonary lobes. Conventional CT angiography was used to correctly identify PE in 12 lobes and absence of emboli in 18 lobes, which corresponded to sensitivity, specificity, PPV, and NPV of 67%, 100%, 100%, and 67%, respectively. A kappa value of 0.65 indicated good correlation with pathologic findings. On BF images, segments with an embolic region showed low perfusion compared with segments with a normal pulmonary region. BF images and fused images correctly showed PE in 16 of 18 pulmonary lobes and absence of emboli in 11 of 12 lobes, which corresponded to sensitivity, specificity, PPV, and NPV of 89%, 92%, 94%, and 85%, respectively, in detection of PE. A kappa value of 0.80 indicated good correlation with pathologic findings. Dual-source CT can depict normal and abnormal blood perfusion distribution in a rabbit's lung. Abnormal pulmonary blood distribution, as shown at dual-source CT, improves detection of acute PE in rabbits.

Natural History and CT Appearances of Aortic Intramural Hematoma

Rupture of the vasa vasorum into the media of the aortic wall results in an aortic intramural hematoma. Characteristic findings of an aortic intramural hematoma include a crescentic hyperattenuating fluid collection at unenhanced computed tomography (CT) and a smooth, nonenhancing, thickened aortic wall at contrast material-enhanced CT. The CT appearance of untreated intramural hematomas evolves over time, and decreased attenuation is a clue to the chronicity of a hematoma. CT is particularly useful for evaluating aortic intramural hematomas because it allows their differentiation from aortic dissections, which have similar clinical manifestations, and permits an exact determination of their location-crucial information for surgical planning. On the basis of CT findings, some hematomas may be expected to resolve spontaneously, whereas others may be identified as posing a high risk for serious complications such as aortic dissection, aneurysm, and rupture. Appropriate clinical management is aided by accurate recognition of diagnostically specific CT features and awareness of their significance.

Hepatocellular carcinomas: Correlation between time to peak hepatocellular carcinomas enhancement and time to peak aortic enhancement

Purpose To prospectively assess the relationship between the time to peak enhancement of hepatocellular carcinomas (HCC) and that of the aorta at 64-detector computed tomography (CT). Materials and methods The study prospectively included 43 patients with known HCC. All underwent abdominal CT imaging by using BodyPerfusion CT model. The CT data acquisition was initiated with a delay of 8–15 s from the beginning of the contrast material administered. The time–density curves (TDC) of the HCC and the aorta were drawn. The times to peak enhancement of the HCC and the aorta were recorded and the correlation between the time to peak enhancement of the HCC and that of the aorta was analyzed. Results There were three tendencies of TDC of the HCC enhancement, only 23.3% of them were similar to that of the aorta. The mean time to peak enhancement of the aorta and the HCC (86.1%) was 23.38 s and 30.04 s, respectively. The time to peak enhancement of most HCC was positively and linearly correlated with the time to peak aortic enhancement ( r = 0.662, P < 0.05). Conclusion The result may potentially allow scan delay optimization at contrast material-enhanced CT image in the detection of HCC according to interindividual variability.

Tumors in the Tracheobronchial Tree: CT and FDG PET Features

A variety of tumors, including primary malignant tumors, secondary malignant tumors, and benign tumors, can occur in the tracheobronchial tree. Primary malignant tumors commonly originate from the surface epithelium or the salivary glands, whereas most benign tumors arise from the mesenchymal tissue. At computed tomography (CT), primary malignant tumors manifest as a polypoid lesion, a focal sessile lesion, eccentric narrowing of the airway lumen, or circumferential wall thickening. At fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET), most squamous cell carcinomas show high uptake, whereas adenoid cystic carcinoma and mucoepidermoid carcinoma show variable uptake depending on the grade of differentiation. High-grade malignancies tend to show high and homogeneous uptake. Carcinoid tumors commonly show intense enhancement at contrast material-enhanced CT, which can be helpful in making the diagnosis, and usually have lower uptake at FDG PET than would be expected for a malignant tumor. Secondary malignant tumors occur as a result of either hematogenous metastasis or direct invasion by a malignancy from an adjacent structure. Their CT manifestations are similar to those of primary malignant tumors, with uptake at FDG PET depending primarily on the metabolic activity and degree of differentiation of the primary tumor. Among the benign tumors, hamartoma and lipoma can show characteristic CT findings such as "popcorn" calcification or internal fat. However, CT findings in most benign tumors are nonspecific. At FDG PET, benign tumors usually show little or no uptake and can be differentiated from malignant tumors. Knowledge of the characteristic CT and FDG PET findings of tracheobronchial tumors can aid in diagnosis and treatment planning.

Distribution of Renal Tumor Growth Rates Determined by Using Serial Volumetric CT Measurements

To retrospectively determine the distribution of growth rates across different sizes and subtypes of renal cortical tumors by assessing tumor volume and maximum tumor diameter at serial volumetric computed tomographic (CT) examinations. The institutional review board approved this retrospective, HIPAA-compliant study. Fifty-three of 2304 patients (34 men, 19 women; mean age, 67 years +/- 10 [standard deviation; range, 39-88 years) who underwent nephrectomy from 1989 to 2006 did not receive preoperative chemotherapy or radiation therapy and underwent at least two preoperative contrast material-enhanced CT examinations (at least 3 months apart) with identical section thickness that was no more than one-fifth of longitudinal tumor diameter. Tumor volume and maximum diameter were measured on CT scans. Reciprocal of doubling time (DT) (RDT) was calculated. Analysis of variance and Student t tests were performed. Thirty-two clear cell carcinomas, 10 papillary carcinomas, six chromophobe carcinomas, four oncocytomas, and one angiomyolipoma were analyzed. Median tumor size was 2.9 cm (range, 1-12 cm). Seven tumors did not increase in volume. DT ranged from -78476.54 to 18057.43 days (mean, -1230.73 days; median, 590.51 days). [corrected] Growth rate determined by using maximum diameter ranged from -10.8 to 33.2 mm/y (mean, 5.1 mm/y; median, 3.5 mm/y). Faster-growing tumors were more likely to be clear cell carcinomas, those of higher grade had higher growth rates. No significant correlation was found between RDT and tumor initial volume, subtype, or grade. Small renal tumors (<or=3.5 cm) were similar to larger tumors in subtype and growth rate. Age at diagnosis correlated negatively with renal tumor growth rate (P = .03). Growth rates in renal tumors of different sizes, subtypes, and grades represent a wide range and overlap substantially. Small renal tumors appear to be similar to larger ones in nature.

Abdomen: Angiography with 16-Detector CT—Comparison of Image Quality and Radiation Dose between Studies with 0.625-mm and those with 1.25-mm Collimation1

To prospectively compare image quality and volume computed tomographic (CT) dose index (CTDI(vol)) of 16-detector CT angiograms of the abdomen acquired with 0.625-mm collimation with those of images acquired with 1.25-mm collimation. This study had institutional review board approval, and informed consent was obtained from all patients. Dual-phase contrast material-enhanced CT was performed in 78 patients (48 men and 30 women; age, 34-91 years; mean age, 64.8 years) by using a 16-detector CT scanner. Patients were prospectively randomized into two equal-sized groups: those who underwent CT with 0.625-mm collimation and nonoverlapped reconstruction and those who underwent CT with 1.25-mm collimation and 50% overlapped reconstruction. Scan acquisition time was 7.5 seconds in both groups. CTDI(vol) was recorded. Arterial phase volume-rendered, arterial phase multiplanar reformatted, and portal venous phase multiplanar reformatted CT angiograms were generated. Qualitative assessment was performed for image quality and for depiction of splanchnic, intercostal, and lumbar arteries and veins. The unpaired t test was used for statistical comparison. On the arterial phase CT angiograms, there was no difference between the two collimation groups for the depiction of proximal splanchnic arteries, while the dorsal pancreatic, intercostal, and lumbar arteries and some peripheral splanchnic arterial branches were better delineated on CT scans obtained with 0.625-mm collimation than on scans obtained with 1.25-mm collimation (P < .05). Regarding the portal venous phase CT angiograms, no difference between the two groups was found in most veins, except the right adrenal vein (P = .003). Image quality was superior for 1.25-mm collimation (P < .001). CTDI(vol) values were positively correlated with patient body weight (r = 0.34, P < .001) but had no correlation with collimation size (P = .24). Scanning with 1.25-mm collimation seems adequate for a routine CT angiography examination of most arteries and veins at 16-detector CT, while scanning with 0.625-mm collimation facilitates improved delineation of fine vessels. CTDI(vol) values correlate positively with body weight but have no correlation with collimation size.

Intraductal Papillary Mucinous Neoplasm of the Pancreas: Assessment of the Likelihood of Invasiveness with Multisection CT

To evaluate the capabilities of multisection computed tomography (CT) in determining the likelihood of invasiveness of intraductal papillary mucinous neoplasm (IPMN). The institutional review board approved this research and waived informed consent from the patients. Two radiologists blinded to the pathologic assessment of malignancy or parenchymal invasion of IPMN retrospectively evaluated CT images of 61 consecutive surgically resected tumors (26 adenomas, 15 noninvasive carcinomas, and 20 invasive carcinomas) in patients who underwent multiphase contrast material-enhanced CT with 0.5- or 1-mm collimation. The findings were statistically analyzed by using univariate and multivariate analyses, with the optimal cutoff levels of each continuous parameter determined by generating receiver operating characteristic curves. The following findings showed significant differences among the three groups: maximum diameter of the main pancreatic duct (MPD), size (length of major axis) of the largest mural nodule in the MPD or in any associated cystic lesion, abnormal attenuating area in the surrounding parenchyma, calcification in the lesion, protrusion of the MPD into the ampulla of Vater, and bile duct dilatation. An MPD diameter of 6 mm or larger, a mural nodule of 3 mm or larger, and an abnormal attenuating area were independently predictive of malignancy. A mural nodule of 6.3 mm or larger in the MPD and an abnormal attenuating area were independently predictive of parenchymal invasion. According to these criteria, the sensitivity, specificity, and accuracy for identifying malignancy were 83%, 81%, and 82% and for identifying parenchymal invasion were 90%, 88%, and 89%, respectively. Multisection CT is useful for distinguishing among adenoma, noninvasive carcinoma, and invasive carcinoma in patients with IPMN.

Microwave Ablation of Lung Malignancies: Effectiveness, CT Findings, and Safety in 50 Patients

To retrospectively evaluate effectiveness, follow-up imaging features, and safety of microwave ablation in 50 patients with intraparenchymal pulmonary malignancies. This HIPAA-compliant study was approved by the institutional review board; informed consent was waived. From November 10, 2003, to August 28, 2006, 82 masses (mean, 1.42 per patient) in 50 patients (28 men, 22 women; mean age, 70 years) were percutaneously treated in 66 microwave ablation sessions. Each tumor was ablated with computed tomographic (CT) guidance. Follow-up contrast material-enhanced CT and positron emission tomographic (PET) scans were reviewed. Mixed linear modeling and logistic regression were performed. Time-event data were analyzed (Kaplan-Meier survival estimates and log-rank statistic). All event times were the time to a patient's first event (alpha level = .05, all analyses). At follow-up (mean, 10 months), 26% (13 of 50) of patients had residual disease at the ablation site, predicted by using index size of larger than 3 cm (P = .01). Another 22% (11 of 50) of patients had recurrent disease resulting in a 1-year local control rate of 67%, with mean time to first recurrence of 16.2 months. Kaplan-Meier analysis yielded an actuarial survival of 65% at 1 year, 55% at 2 years, and 45% at 3 years from ablation. Cancer-specific mortality yielded a 1-year survival of 83%, a 2-year survival of 73%, and a 3-year survival of 61%; these values were not significantly affected by index size of larger than 3 cm or 3 cm or smaller or presence of residual disease. Cavitation (43% [35 of 82] of treated tumors) was associated with reduced cancer-specific mortality (P = .02). Immediate complications included pneumothorax (Common Terminology Criteria for Adverse Events [CTCAE] grades 1 [18 of 66 patients] and 2 [eight of 66 patients]), hemoptysis (four of 66 patients), and skin burns (CTCAE grades 2 [one of 66 patients] and 3 [one of 66 patients]). Microwave ablation is effective and may be safely applied to lung tumors. (c) RSNA, 2008.

Lymphoplasmacytic Sclerosing Pancreatitis (Autoimmune Pancreatitis): Evaluation with Multidetector CT

Lymphoplasmacytic sclerosing pancreatitis is a form of chronic pancreatitis characterized by a mixed inflammatory infiltrate that centers on the pancreatic ducts. It is a cause of benign pancreatic disease that can clinically mimic pancreatic cancer. Preoperative detection of lymphoplasmacytic sclerosing pancreatitis is important because patients usually respond to steroid therapy. Patients with lymphoplasmacytic sclerosing pancreatitis are often referred for computed tomography (CT) when they are suspected of having a pancreatic or biliary neoplasm; therefore, it is important to search for potential findings suggestive of lymphoplasmacytic sclerosing pancreatitis when typical findings of a pancreatic or biliary neoplasm are not found. Typical CT findings include diffuse or focal enlargement of the pancreas without dilatation of the main pancreatic duct. Focal enlargement is most commonly seen in the head of the pancreas, and the involved pancreas on contrast material-enhanced CT images may be iso-attenuating relative to the rest of the pancreas, or hypo-attenuating, especially during the early postcontrast phase. Thickening and contrast enhancement of the wall of the common bile duct and gallbladder may reflect inflammatory infiltrate and fibrosis associated with lymphoplasmacytic sclerosing pancreatitis. There are several features seen at CT that may help to differentiate lymphoplasmacytic sclerosing pancreatitis from pancreatic cancer, such as diffuse enlargement of the pancreas with minimal peripancreatic stranding in patients with obstructive jaundice, an absence of significant pancreatic atrophy, and an absence of significant main pancreatic duct dilatation. When these findings are encountered, clinical, other imaging, and serologic data should be evaluated.

Contrast-enhanced 64-Section Coronary Multidetector CT Angiography versus Conventional Coronary Angiography for Stent Assessment

To prospectively evaluate the accuracy of 64-section computed tomography (CT) for diagnosis of stent restenosis, by using conventional coronary angiography as the reference standard. The ethics committee granted permission for the study; patients gave written consent. Contrast material-enhanced coronary CT angiography was performed in 53 patients (45 men, eight women; mean age, 54 years +/- 9 [standard deviation]) suspected of having stent restenosis. Coronary CT angiographic findings were compared with conventional coronary angiographic findings. Two physicians analyzed coronary CT angiographic data sets with multiplanar reformatted images and three-dimensional reformations by using a volume-rendering technique and looked for stent detectability, low-attenuation in-stent filling defects, and grades of restenosis. Conventional coronary angiographic results were interpreted by one of several observers in consensus for stent restenosis; they were blinded to coronary CT angiographic data. Statistical software and general estimating equations were used for data analysis. One hundred ten stents were identified in 53 patients. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of coronary CT angiography in detection of in-stent restenosis were 96.9%, 88.0%, 77.5%, 98.5%, and 91%, respectively. Coronary CT angiography depicted in-stent low-attenuation filling defects with an accuracy of 91% and negative predictive value of 98.5% (95% confidence interval: 90.9, 99.9). Coronary CT angiography depicted the status of 97 of 107 stents. There was no significant difference between in-stent lumen visibility and stent diameter (P = .104). Coronary CT angiography helped diagnose 15 of 18 stent restenoses with less than 50% narrowing, five of five stent restenoses with 50%-74% narrowing, and nine of nine (100%) stent restenoses with 75% or greater narrowing or total occlusion of the stent lumen. Coronary CT angiography can depict in-stent low-attenuation filling defects, which appear to be a reliable sign of stent restenosis, and 64-section CT depicts such defects with a high degree of accuracy.

Case 121: Familial Adrenocorticotropin-independent Macronodular Adrenal Hyperplasia Causing Cushing Syndrome

A 41-year-old African-American woman with a medical history of poorly controlled hypertension was found unresponsive. She was intubated by paramedics in the field. When she arrived at the emergency department, neurologic examination revealed obtunded mental status with right-sided hemiparesis and diminished peripheral reflexes. Vital signs were remarkable for a blood pressure of 220/170 mm Hg. An unenhanced computed tomographic (CT) scan of the head was obtained, and the patient was admitted to the neurosurgical intensive care unit for further observation. Routine chest radiography performed at admission revealed symmetric but abnormal widening of the superior mediastinum. This finding led us to obtain contrast material-enhanced CT scans of the chest and upper abdomen after intravenous administration of 140 mL of iopromide (Ultravist; Berlex Laboratories, Wayne, NJ). Several years later, this patient's older sister presented with worsening uncontrolled blood pressure. Diagnostic work-up, including intravenous contrast-enhanced CT of the abdomen, was performed in the patient's sister.

CT Evaluation of the Bulging Papilla with Endoscopic Correlation

A variety of pathologic conditions can cause abnormalities of the ampulla of Vater. A bulging papilla is frequently encountered at computed tomography (CT) and can be seen in healthy individuals as well as in patients with various pathologic conditions such as papillitis, ampullary cancer, and intraductal papillary mucinous tumor. Mural thickening and certain attenuation patterns seen at contrast material-enhanced CT can help differentiate pathologic papilla from normal papilla. Increased targetlike enhancement of the papilla is likely to represent a benign condition such as papillitis, whereas an enhancing polypoid mass or focal asymmetric or irregular thickening with prolonged enhancement in the ampulla of Vater indicates a malignant condition such as ampullary or periampullary carcinoma. Although CT often does not clarify the exact cause of bulging, adequate duodenal distention may allow detection of an abnormal papilla, thereby providing additional information about other abnormalities in the pancreaticobiliary system. Thus, CT findings may prove useful for subsequent imaging studies such as magnetic resonance (MR) cholangiography or endoscopy. MR cholangiography may be equivalent to CT for identifying a bulging papilla and superior for distinguishing the underlying cause. However, endoscopy with or without biopsy is the best method for making a definitive diagnosis in patients with a bulging papilla. Familiarity with the normal imaging anatomy of the periampullary region and with the imaging features of the various pathologic causes of a bulging papilla may be useful in making the diagnosis.

Effectiveness and Renal Tolerance of Multidetector Helical CT with Gadobutrol: Results of a Comparative Porcine Study

To prospectively evaluate the safety and effectiveness of high doses of 1 mol/L gadobutrol as a contrast agent for computed tomography (CT). Experiments were performed according to guidelines for care of laboratory animals. The local animal care committee approved the study protocol. Unenhanced and contrast material-enhanced CT images of the chest and abdomen were obtained randomly in nine domestic pigs. Gadobutrol was injected (1, 2, or 3 mL per kilogram of body weight; three pigs for each dose). Attenuation was measured in different vascular and parenchymal structures. Changes in blood chemistry and hematologic parameters were monitored before and 1, 2, 3, and 7 days after gadobutrol administration. Urine samples were evaluated before and 7 days after gadobutrol administration. Technetium 99m mertiatide renal scintigraphy was performed before and 7 days after contrast medium injection. Animals were sacrificed 7 days after contrast medium administration, and one kidney was removed from each animal for examination with light microscopy. No serious adverse events occurred. A mixed-model nested analysis of variance was used for statistical evaluation. Mean attenuations for the 1, 2, and 3 mL/kg gadobutrol doses, respectively, were 148 HU +/- 20 (standard deviation), 282 HU +/- 18, and 289 HU +/- 20 in the thoracic aorta; 99 HU +/- 11, 166 HU +/- 9, and 153 HU +/- 18 in the kidneys; and 106 HU +/- 7, 186 HU +/- 18, and 224 HU +/- 24 in the inferior vena cava. No clinically relevant changes in hematologic, blood chemistry, or urine analysis results were detected. Markers for glomerular filtration and tubular function were unaffected in all groups. Scintigraphy revealed no differences between unenhanced and contrast-enhanced results. No morphologic changes of the renal parenchyma were found at histologic analysis. Contrast-enhanced CT with a 2 or 3 mmol/kg dose of 1 mol/L gadobutrol resulted in excellent vascular and parenchymal enhancement. A gadobutrol dose of up to 3 mL/kg did not affect renal function.

CT and MR Imaging after Imaging-guided Thermal Ablation of Renal Neoplasms

In recent years, thermal tumor ablation techniques such as percutaneous radiofrequency (RF) ablation and cryoablation have assumed an important role in the management of renal tumors, particularly in patients who may be suboptimal candidates for more invasive surgical techniques. Postablation computed tomography (CT) and magnetic resonance (MR) imaging play an important part in evaluation of the ablation zone, surveillance for residual or recurrent tumor, and identification of procedure-related complications. The appearance of the ablation zone may vary depending on the ablation technique used, initial tumor size, and tumor location and composition. Most ablated tumors demonstrate a gradual decrease in size over time once the acute changes have resolved, although tumor involution is more evident after cryoablation than after RF ablation. Exophytic tumor ablation zones typically have a "bull's-eye" appearance on CT scans and MR images obtained after RF ablation, with a visible mass often persisting in the absence of viable tumor. Residual or recurrent tumor often manifests as a focus of nodular or crescentic enhancement on postablation contrast material-enhanced CT scans and MR images, although a thin peripheral rim of enhancement often persists for several months following cryoablation. Complications following renal tumor ablation are usually minor but may include hemorrhage, ureteral stricture, urine leak, colonic perforation and colonephric fistula, and pneumothorax. As more patients undergo renal ablation procedures, it will become increasingly important that radiologists be able to recognize typical postablation CT and MR imaging findings to prevent confusing them with other pathologic processes.

Imaging of Cerebral Venous Thrombosis: Current Techniques, Spectrum of Findings, and Diagnostic Pitfalls

Cerebral venous thrombosis is a relatively uncommon but serious neurologic disorder that is potentially reversible with prompt diagnosis and appropriate medical care. Because the possible causal factors and clinical manifestations of this disorder are many and varied, imaging plays a primary role in the diagnosis. Magnetic resonance (MR) imaging, un-enhanced computed tomography (CT), unenhanced time-of-flight MR venography, and contrast material-enhanced MR venography and CT venography are particularly useful techniques for detecting cerebral venous and brain parenchymal changes that may be related to thrombosis. To achieve an accurate diagnosis, it is important to have a detailed knowledge of the normal venous anatomy and variants, the spectrum of findings (venous sinus thrombi and recanalization, parenchymal diffusion or perfusion changes or hemorrhage), other potentially relevant conditions (deep venous occlusion, isolated cortical venous thrombosis, idiopathic intracranial hypertension), and potential pitfalls in image interpretation.