Massive Intraventricular Air Embolism after Contrast-enhanced CT: Report of Two Cases

Venous air embolism, although considered as a rare condition, it occurs more frequently than it is recognized. Air embolism has been reported to occur after contrast-enhanced CT examination in up to 23% of patients. Because these emboli are usually small to moderate size and they are venous, the patients are usually asymptomatic. However, a large amount of intravenous air can cause disastrous consequences and it can be fatal. The author reports here on 2 cases of symptomatic massive intraventricular air embolism after contrast enhanced CT with a brief review of the pathophysiology and the recommended treatment of air embolization.

Hepatic CT Enhancement: Comparison between Dimeric and Monomeric Nonionic Contrast Agents in Rabbits

PURPOSE: To determine the hepatic and vascular enhancement profiles with nonionic dimeric, iodixanol, contrast agent in the rabbit and to compare them with nonionic monomeric, ioversol, contrast agent. MATERIALS AND METHODS: Seven rabbits initially underwent hepatic dynamic CT scan with either iodixanol or ioversol, followed by repeated CT scan with other unused contrast agent with one week interval between scans. Pre and post contrast attenuation values of hepatic parenchyma, aorta and portal vein were measured sequentially. The mean enhancement of the hepatic parenchyma, aorta and portal vein were compared between two agents. The mean peak enhancement and peak enhancement time of the liver, aorta, and portal vein were also compared. RESULTS: The attenuation values of ioversol showed a greater mean hepatic enhancement than iodixanol from 18 seconds to 39 seconds after injection (from late arterial phase to early portal venous phase) with a statistical significance (p<0.05). The mean peak enhancement of hepatic parenchyma, aorta and portal vein was also greater using ioversol than iodixanol, but the mean peak enhancement times of ioversol and iodixanol were nearly identical. CONCLUSION: Ioversol may have the greater effects than iodixanol on hepatic tumor conspicuity, especially from late arterial phase to early portal veneous phase.

Enhancement Pattern of Hepatocellular Carcinoma on Triphasic Helical CT: Quantitative Study

PURPOSE: To assess the enhancement pattern of hepatocellular carcinoma (HCC), as seen on triphasic helical dynamic computed tomography (CT) by measuring the attenuation value. MATERIALS AND METHODS: Triphasic helical dynamic CT scans of the liver in 94 patients (M:F=73:21; aged 33-81 years) with HCC were evaluated. The condition was confirmed on the basis of histologic (n=28) or clinical (n=66) findings. Scans were obtained at 30, 70, and 180 seconds after the start of contrast material injection, the attenuation values of the solid portion of the HCC and adjacent normal liver parenchyma being measured during the three phases. Enhancement patterns of the HCC nodule and adjacent liver parenchyma were analyzed, and the size of HCCs, the presence or absence of portal vein thrombosis, and the Child classification were also determined. RESULTS: The mean attenuation values of HCC were 69 HU during the arterial phase, 80 HU during the portal phase, and 65 HU during the delayed phase, while those of liver parenchyma were 48 HU, 81 HU and 72 HU, respectively. In 71.3% of cases (67/94), maximum enhancement occurred during the portal phase. Decreased tumor attenuation after peak enhancement was seen in 71.3% of lesions (67/94, Group I). while in 28.7% (27/94, Group II) attenuation showed no significant decrease. There were no statistically significant differences in the size of HCCs, portal vein thrombosis or Child classification between the two groups (p>0.05). CONCLUSION: On triphasic helical dynamic CT, the mean attenuation value of HCCs was highest during the portal phase. Over time, the majority of HCCs showed a decreased attenuation value.

Contrast Media in Abdominal Computed Tomography: Optimization of Delivery Methods

OBJECTIVE: To provide a systematic overview of the effects of various parameters on contrast enhancement within the same population, an animal experiment as well as a computer-aided simulation study was performed. MATERIALS AND METHODS: In an animal experiment, single-level dynamic CT through the liver was performed at 5-second intervals just after the injection of contrast medium for 3 minutes. Combinations of three different amounts (1, 2, 3 mL/kg), concentrations (150, 200, 300 mgI/mL), and injection rates (0.5, 1, 2 mL/sec) were used. The CT number of the aorta (A), portal vein (P) and liver (L) was measured in each image, and time-attenuation curves for A, P and L were thus obtained. The degree of maximum enhancement (Imax) and time to reach peak enhancement (Tmax) of A, P and L were determined, and times to equilibrium (Teq) were analyzed. In the computed-aided simulation model, a program based on the amount, flow, and diffusion coefficient of body fluid in various compartments of the human body was designed. The input variables were the concen-trations, volumes and injection rates of the contrast media used. The program generated the time-attenuation curves of A, P and L, as well as liver-to-hepatocel-lular carcinoma (HCC) contrast curves. On each curve, we calculated and plotted the optimal temporal window (time period above the lower threshold, which in this experiment was 10 Hounsfield units), the total area under the curve above the lower threshold, and the area within the optimal range. RESULTS: A. Animal Experiment: At a given concentration and injection rate, an increased volume of contrast medium led to increases in Imax A, P and L. In addition, Tmax A, P, L and Teq were prolonged in parallel with increases in injection time The time-attenuation curve shifted upward and to the right. For a given volume and injection rate, an increased concentration of contrast medium increased the degree of aortic, portal and hepatic enhancement, though Tmax A, P and L remained the same. The time-attenuation curve shifted upward. For a given volume and concentration of contrast medium, changes in the injection rate had a prominent effect on aortic enhancement, and that of the portal vein and hepatic parenchyma also showed some increase, though the effect was less prominent. A increased in the rate of contrast injection led to shifting of the time enhancement curve to the left and upward. B. Computer Simulation: At a faster injection rate, there was minimal change in the degree of hepatic attenuation, though the duration of the optimal temporal window decreased. The area between 10 and 30 HU was greatest when contrast media was delivered at a rate of 2 -3 mL/sec. Although the total area under the curve increased in proportion to the injection rate, most of this increase was above the upper threshould and thus the temporal window was narrow and the optimal area decreased. CONCLUSION: Increases in volume, concentration and injection rate all resulted in improved arterial enhancement. If cost was disregarded, increasing the injection volume was the most reliable way of obtaining good quality enhancement. The optimal way of delivering a given amount of contrast medium can be calculated using a computer-based mathematical model.

Intralobar Pulmonary Sequestration, Supplied from Left Gastric Artery: A Case Report

Pulmonary sequestration is a relatively rare anomaly. Arterial supply is usually derived from the aorta or its major branches, or very rarely from the left gastric artery. We present a case of intralobar sequestration in which blood was supplied by the left gastric artery.

Spiral CT in Kidney: Assumption of Renal Function by Objective Evaluation of Renal Cortical Enhancement

PURPOSE: To correlate the degree of renal cortical enhancement, objectively evaluated by means of spiral CT, with the serum level of creatinine, and to determine the extent to which this degree of enhancement may be used to detect renal parenchymal disease. MATERIALS AND METHODS: Eighty patients [M:F=50:30; age=25 -90 (mean, 53) years] with available serum level of creatinine who underwent spiral CT between September and October 1999 were included in this study. In fifty patients the findings suggested hepatic or biliary diseases such as hepatoma, biliary cancer, or stone, while in thirty, renal diseases such as cyst, hematoma, or stone appeared to be present. Spiral CT imaging of the cortical phase was obtained at 30 -40 seconds after the injection of 120 ml of non-ionic media at a rate of 3ml/sec. The degree of renal cortical enhancement was calculated by dividing the CT attenuation number of renal cortex at the level of the renal hilum by the CT attenuation number of aorta at the same level. The degree of renal cortical enhancement was compared with the serum level of creatinine, and the degree of renal cortical enhancement in renal parenchymal disease with that of the normal group. Among eighty patients there were five with renal parenchymal disease and 75 with normal renal function. RESULTS: The ratio of the CT attenuation number of renal cortex to that of aorta at the level of the renal hilum ranged between 0.49 and 0.99 (mean, 0.79; standard deviation, 0.15), while the serum level of creatinine ranged between 0.6 and 3.2 mg/dl. There was significant correlation (coefficient of -0.346) and a statistically significant probability of 0.002 between the ratio of the CT attenuation numbers and the serum level of creati-nine. There was a significant difference (statistically significant probability of less than 0.01) between those with renal parenchymal disease and the normal group. CONCLUSION: The use of spiral CT to measure the degree of renal cortical enhancement provides not only an effective index for estimating renal functional status but also a means of differentiating between patients with renal parenchymal disease and those who are normal.

Comparison of Contrast-enhanced Spiral CT Scan and Pulmonary Angiogra p hy in Diagnosing Pulmonary Embolism: An Experimental Study in Pig Models

PURPOSE: The purpose of our study was to compare the diagnostic value of contrast-enhanced spiral CT scanning and pulmonary angiography in detecting central and peripheral pulmonary embolism (PE) in pigs. MATERIALS AND METHODS: Experiments were performed in a porcine model of acute pulmonary embolism. Five pigs underwent contrast-enhanced spiral CT and pulmonary angiography after central venous administration of embolic material (Konyak). Three thoracic radiologists read the films and the results were compared with the findings of pathologic specimens. RESULTS: Of 85 cases of PE detected pathologically, 78 (91.8 %) were visible with spiral CT and 65 (76.5 %) with pulmonary angiography. Sensitivity and specificity for the detection of central emboli were 95 % and 100 %, respectively, with spiral CT, and 89 % and 100 %, respectively, with pulmonary angiography. Sensitivity and specificity for the detection of peripheral emboli were 88 % and 99 %, respectively, with spiral CT, and 64% and 100 %, respectively, with pulmonary angiography. CONCLUSION: Contrast-enhanced spiral CT is a very useful method for the diagnosis of both peripheral and central pulmonary embolism. Compared to pulmonary angiography its sensitivity and specificity are high.

Comparison of Contrast-enhanced Spiral CT Scan and Pulmonary Angiogra p hy in Diagnosing Pulmonary Embolism: An Experimental Study in Pig Models

PURPOSE: The purpose of our study was to compare the diagnostic value of contrast-enhanced spiral CT scanning and pulmonary angiography in detecting central and peripheral pulmonary embolism (PE) in pigs. MATERIALS AND METHODS: Experiments were performed in a porcine model of acute pulmonary embolism. Five pigs underwent contrast-enhanced spiral CT and pulmonary angiography after central venous administration of embolic material (Konyak). Three thoracic radiologists read the films and the results were compared with the findings of pathologic specimens. RESULTS: Of 85 cases of PE detected pathologically, 78 (91.8 %) were visible with spiral CT and 65 (76.5 %) with pulmonary angiography. Sensitivity and specificity for the detection of central emboli were 95 % and 100 %, respectively, with spiral CT, and 89 % and 100 %, respectively, with pulmonary angiography. Sensitivity and specificity for the detection of peripheral emboli were 88 % and 99 %, respectively, with spiral CT, and 64% and 100 %, respectively, with pulmonary angiography. CONCLUSION: Contrast-enhanced spiral CT is a very useful method for the diagnosis of both peripheral and central pulmonary embolism. Compared to pulmonary angiography its sensitivity and specificity are high.

Usefulness of Measurement of Circulation Time Using MgSO4: Correlation with Time-Density Curve Using Electron Beam Computed Tomography

PURPOSE: To determine the usefulness of MgSO 4 for measuring the systemic circulation time. Material and Methods: Systemic circulation time, defined as elapsed time from the injection of MgSO 4 solution to the point of pharyngeal burning sensation, was measured in 63 volunteers. MgSO 4 was injected into a superficial vein of an upper extremity. Using dynamic electron beam computed tomography at the level of the abdominal aorta and celiac axis, a timeintensity curve was plotted, and for these two locations, maximal enhancement time was compared. RESULTS: For 60 of the 63 subjects, both systemic circulation time and maximal enhancement time were determined. Average systemic circulation time was 17.4 (SD: 3.6) secs. and average maximal enhancement times at the level of the abdominal aorta and celiac axis were 17.5 (SD: 3.0) secs. and 18.5 (SD: 3.2)secs., respectively. Correlation coefficients between systemic circulation time and maximal enhancement time for the abdominal aorta and celiac axis were 0.73 (p<0.01) and 0.73 (p<0.05) respectively. CONCLUSION: The systemic circulation time demonstrated by MgSO 4 injection and maximal enhancement time for the abdominal aorta showed significant correlation. Thus, to determine the appropriate scanning time in contrast-enhanced radiological studies, MgSO 4 can be used instead of a test bolus study.

Delayed Enhancement of Pleural Effusion Following Angiography: A Case Report

It has been suggested that hyperdensity of pleural effusion, as seen on CT, is indicative of hemothorax. We report a case in which CT revealed delayed contrast enhancement of pleural effusion on, with no evidence of hemothorax. This phenomenon is clinically important because delayed enhancement can mimic hyperdensity of hemothorax.

Dual-Phase Helical CT Using Bolus Triggering Technique: Optimization of Transition Time

PURPOSE: To optimize the transition time between the triggering point in monitoring scanning and theinitia-tion of diagnostic hepatic arterial phase (HAP) scanning in hepatic spiral CT, using a bolus triggeringtechnique. MATERIALS AND METHODS: One hundred consecutive patients with focal hepatic lesion were included inthis study. Patients were randomized into two groups. Transition times of 7 and 11 seconds were used in group 1and 2, respectively. In all patients, bolus triggered HAP spiral CT was obtained using a semi-automatic bolustracking program after the injection of 120 mL of non-ionic contrast media at a rate of 3 mL/sec. When aorticenhancement reached 90 HU, diagnostic HAP scanning began after a given transition time. From images of group 1 andgroup 2, the degree of parenchymal enhancement of the liver and tumor-to-liver attenuation dif-ference weremeasured. Also, for qualitative analysis, conspicuity of the hepatic artery and hypervascular tumor was scored andanalyzed. RESULTS: Hepatic parenchymal enhancement on HAP was 12.07+/-6.44 HU in group 1 and 16.03+/-5.80 HU ingroup 2 (p .05). In the evaluationof conspicuity of hepatic artery, there was no statistically significant difference between the two groups(p>.05). The conspicuity of hypervascular tumors in group 2 was higher than in group 1 (p<.05). CONCLUSION: HAPspiral CT using a bolus triggering technique with a transition time of 11 seconds provides better HAP images thanwhen the transition time is 7 seconds.

Differentiation of Hepatocellular Carcinoma from Intrahepatic Cholangiocarcinoma as the Cause of Biliary Obstruction: Value of Dynamic CT During the Hepatic Arterial Phase

PURPOSE: To evaluate the usefulness of dynamic CT during the hepatic arterial phase with rapid IV injection ofcontrast material in distinguishing hepatocellular carcinoma (HCC) from intrahepatic cholangiocarcinoma (ICAC) asthe cause of biliary obstruction. MATERIALS AND METHODS: We retrospectively reviewed two-phase dynamic incrementalCT or helical CT findings in 22 patients with intrahepatic duct obstruction secondary to pathologically provenHCCs (n=12) or ICACs (n=10). Two-phase CT scans were obtained 20-45 seconds (hepatic arterial phase) or 2 minutes(equilibrium phase) after the initiation of a bolus injection of contrast material (5 mL/sec, 150 mL). Theenhancement patterns of tumors, as seen on two-phase images, were classified as hypo-, iso-, or hyperattenuated,relative to surrounding liver parenchyma. Two-phase images were compared and correlated with pathologic findings. RESULTS: During the hepatic arterial phase, diffuse high-enhancement was seen in nine HCCs (75%) and partialenhancement in three (25%); five (50%) of the ten ICACs were hypodense and five (50%) were hypodense withperipheral enhancement. During the equilibrium phase, however, all HCCs were hypodense and capsular enhancementwas seen in four cases (33.3%). All ICACs were hypodense with mild peripheral or central heterogeneousenhancement. Contrast enhancement patterns of HCCs during the hepatic arterial phase were significantly different(P<.0001) from those of ICACs. CONCLUSION: Our results suggest that dynamic CT during the hepatic arterial phase,with rapid IV injection of contrast material, is useful for the differentiation of HCC from ICAC as the cause ofbiliary obstruction.

Comparison of Enhancement Pattern of Nodular and Massive Hepatocellular Carcinoma with and without Portal VeinThrombosis in Three-Phase Spiral CT

PURPOSE: To evaluate the enhancement patterns of nodular and massive hepatocellular carcinoma (HCC), with or without portal vein thrombosis, on three-phase spiral CT. MATERIALS AND METHODS: Contrast enhancement patterns in 61 patients with HCC were retrospectively analysed. Three-phase spiral CT images of the hepatic arterial dominant phase, portal dominant phase, and delayed phase were obtained 30, 60-70, and 360 seconds after the injection of contrast material was initiated. Tumors were divided into grossly nodular and massive type and enhancement patterns of HCC, with and without portal vein thrombosis, were compared. These patterns were divided into three groups, as follows: High/High/Low; High/Low/Low; Low/Low/Low. HCC with portal vein thrombosis was found in 21 of 61 cases ; this carcinoma without portal vein thrombosis was found in 40 cases. The nodular type accounted for 39 cases, and the massive type for 22. RESULTS: In 21 cases of HCC with portal vein thrombosis, the most common enhancement pattern was L/L/L, and was seen in 13 cases (62%); H/L/L was seen in eight (38%), but H/H/L was not seen. In 40 cases of HCC without portal vein thrombosis, the most common enhancement pattern was H/L/L, seen in 25 cases (63%) ; this was followed by L/L/L (11 cases ; 27%), and H/H/L (4 cases ; 10%). In the arterial dominant phase, among cases of HCC with portal vein thrombosis, low attenuation was more common (13/21) than high (8/21);among cases of HCC without portal vein thrombosis, high attenuation was more common (29/40) than low (11/40). Among 39 nodular-type cases, HCC with portal vein thrombosis was found in six (H/H/L and L/L/L: three each), and HCCwithout portal vein thrombosis was seen in 33 (H/L/L: 22; L/L/L: 7; H/H/L; 4). Among 22 cases of the massive type, HCC with portal vein thrombosis accounted for 15 (L/L/L: 10, H/L/L: 5), and seven cases without portal vein thrombosis were seen (L/L/L: 4 ; H/L/L : 3). CONCLUSION: On Three-phase spiral CT, HCC showed different enhancing patterns according tumor type and the presence of portal vein thrombosis.

Quantitative Evaluation in Enhancement of Pancreas and Adjacent Vessels during Spiral CT

PURPOSE: To determine by quantitative evaluation of pancreatic and adjacent vascular enhancement during spiral CT, the ideal scan delay for examination of the pancreas. MATERIALS AND METHODS: Dual (n=90) and triple (n=90) phase spiral CT scans of patients whose pancreas showed no pathologic condition were retrospectively evaluated. Dual-phase scans were performed at 43 seconds (early), and 5-6 minutes (delayed) after the injection of 120ml of contrast material at an injection rate of 3ml/sec ; triple-phase scans were performed at 25 seconds (arterial), 60-65 seconds (portal) and 5-6 minutes (delayed) after the injection of 120-140ml of contrast material at an injection rate of 2-4ml/sec, and ten patients also underwent precontrast scanning. CT attenuation values (HU) were measured in the head, body and tail of the pancreas, aorta, and main portal vein during each phase of all scans. Triple-phase protocol was used to measure the effect of different total volumes and injection rates on enhancement of the pancreas and adjacent vessels. RESULTS: There was no significant difference in the degree of enhancement of the pancreas head, body and tail during each phase (p>0.05). The pancreas was maximally enhanced on 43 second delayed scan (132+/-20 HU)(p0.05). The main portal vein showed maximum enhancement on 43-second delayed scan (207+/-44 HU)(p<0.05). Different total volume of contrast material did not change the enhancement of the pancreas and adjacent vessels. At an injection rate of 2ml/sec, peak enhancement of the pancreas, aorta and portal vein was obtained on 60-65 second delayed scan, and at 4ml/sec, peak enhancement was obtained on 25 second delayed scan(p<0.05). CONCLUSION: Observing the usual protocols for abdominal spiral CT scanning, the pancreas was most effectively evaluated using a 43-second delayed scan. An increased injection rate resulted in earlier enhancement of the pancreas, aorta and portal vein.

Correlation Between Contrast Enhancement of Portal Vein and Spleen Size in Dual-phase Spiral CT

URPOSE: To evaluate using spiral CT the effect of spleen size on blood flow in the portal venous system andto know the usefulness of this evaluation. MATERIALS AND METHODS: Fifty-one patients without evidence on spiralCT scan of abnormality thought to affect portal venous flow presented between December 1994 and June 1995. We measured spleen size and Hounsfield units of portal vein in dual-phase, and calculated the ratio of the unit inthe portal phase to that in the arterial phase. Spleen size was measured, using the length of X-axis by that of Z-axis on spiral CT scan. We then measured the correlation between the two values. CT was performed with a Somatom Plus-S scanner(Siemens, Erlangen, Germany). A total dose of 120ml of non-ionic contrast material(Ultravist) was administered at a rate of 3ml/sec. Arterial and portal phase were obtained after 30 seconds and 60 seconds fromthe beginning of the contrast agent injection. RESULTS: The correlation between spleen size and contrast enhancement of the portal vein was relatively significant(Pearson's correlation coefficient(r)=0.41801). CONCLUSIONS: Spleen size significantly affects portal venous flow on spiral CT scan. The evaluation of spleensize and contrast enhancement of the portal vein could be useful in the differential diagnosis of diseases which affect portal venous flow.