The Histopathologic Reaction of Rabbit Lungs after Intrabronchial Application of Contrast Agents

PURPOSE: The aim of this study was to determine a safe gastrointestinal contrast agent that could be used in various clinical situations where there is a risk of aspiration using a rabbit model. MATERIALS AND METHODS: 30 healthy white rabbits were used. The rabbits were divided into 5 groups containing six animals each, one control group (anesthesia only) and 4 groups receiving various contrast agents [Solotop (Barium sulphate suspension), Gastrografin (Sodium and meglumine amidotrizoate), and Telebrix (Meglumine ioxitalamate), Visipaque (Iodixanol)]. The contrast agents were injected selectively into a main bronchus via a catheter inserted under fluoroscopy guidance. The rabbits were sacrificed either 1 day or 7 days after injecting the contrast agents, and the tissue reaction of the bronchi and lungs were examined both macro- and microscopically. The level of alveolar septal thickening, peribronchiolar lymphocytic infiltration, pulmonary congestion and edema, inflammatory exudate in the alveoli or bronchiolar lumina, microabscess formation, necrosis, pigmentation of materials injected, and fibropurulent pleurisy were evaluated and graded according to the severity as follows: no change, mild, moderate, marked in degree. RESULTS: The common microscopic findings were alveolar septal thickening and peribronchiolar lymphocytic infiltration. Pulmonary congestion and edema, inflammatory exudate in the alveoli or bronchiolar lumina were observed in 21 out of 24 rabbits receiving the contrast agents. Pigmentation of the materials injected was observed only in the group receiving Solotop. An inflammatory exudate in the alveoli and bronchiolar/bronchial lumina, microabscess formation, and necrosis were noted in most groups, but was more frequent and severe in the group receiving Gastrografin. CONCLUSION: The histopathological reactions of the rabbit lungs after the intrabronchial application of a contrast agent showed variable degrees of inflammatory reactions. Gastrografin produced most severe and extensive reaction, Solotop and Telebrix a moderate reaction, and Visipaque a minimal reaction. Therefore, a non-ionic dimeric contrast agent such as Visipaque may be the safest contrast agent in the lung when a GI tract examination is performed in clinical situations where there is a risk of aspiration.

Equilibrium Phase MR Angiography Using New Blood Pool Contrasts: Experimental Study in Rabbits

PURPOSE: The purpose of this study was to evaluate the usefulness of three experimental blood pool contrast agents for equilibrium phase magnetic resonance angiography. MATERIALS AND METHODS: MR angiography was performed in 21 rabbits before and 1, 5, 10, 20 and 30 minutes and 24 hours after the injection of gadolinium-based blood pool contrast agents (Gadomer-17, Gadofluorine M,) and superparamagnetic iron oxide blood pool agent (Ferucarbotran). 3D TOF SPGR images of the thoracic and abdominal aorta (and involving the renal arteries) were obtained. The signal difference-to noise ratios (SDNRs) were measured over time in the aorta. These images were then compared to that of images with Gd-DTPA. RESULTS:MR angiography with the three blood pool agents yielded excellent visualization results of the rabbit abdominal aorta. At the same dose, the three agents provided a significant increase of the aorta-to-tissue SDNR in comparison with that achieved with the Gd-DTPA (a 250% increase for Gadomer-17, a 124% increase for Gadofluorine and a 88% increase for Ferucarbotran). The SDNRs using Ferucarbotran especially showed continuously increasing values to 30 minutes after the injection of contrast agent. CONCLUSION: The three blood pool agents were found to be very useful contrast agents for equilibrium phase MR angiography.

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.

Efficacy of Pamiray(R) as a Nonionic Intravenous Contrast Material: Experimental Study Using Normal Rabbits

PURPOSE: To evaluate the efficacy of Pamiray(R) as an intravenous nonionic contrast material by comparing it with an established nonionic contrast material (Iopamiro(R)). MATERIALS AND METHODS: Forty adult New Zealand white rabbits weighing about 3.0 kg were used in this study. Aortography and urography (scout, 5, 15 and 30 minutes delay after injection) were performed in ten rabbits with Pamiray(R) (370 mgI/mL) and in other ten rabbits with Iopamiro(R) (370 mgI/mL). All twenty rabbits under-went abdominal triple-phase spiral CT before and 5 and 30 seconds after injection of the contrast material. The degree of contrast enhancement seen on aortograms and intravenous urograms was determined using a three-point scale by two radiologists, who reached a consensus. CT attenuation expressed in Hounsfield units (HU) was measured using the regions of interest (ROIs) facility in the liver, bilateral kidneys, aorta, portal vein, and inferior vena cava. The Mann-Whitney U test was used in image evaluation for intergroup comparisons. RESULTS: There was no significant difference between the two groups in the degree of contrast enhancement seen on aortograns. In urography, however, Iopamiro(R) was superior to Pamiray(R) in demonstrating calyces of the right kidney on 15-minute delay images and Pamiray(R) was superior to Iopamiro(R) in demonstrating the right ureter and the renal pelvis on five minute-delay images and the left ureter on 30 minutes delay (p<.05). Peak enhancement of the aorta during the first phase of bdominal CT was higher in the group in which Pamiray(R) was used. CONCLUSION: When normal rabbits were used for aortography, abdominal CT, and urography, Pamiray(R), provided more effective contrast enhancement than a previously used nonionic contrast material, namely Iopamiro(R). There were, however, slight differences in the enhancement features of renal calyces and ureters seen on 5-and 15-minute urograms.

Radiologic Findings of Cholangiolocellular Carcinoma: A Case Report

Cholangiolocellular carcinoma is a rare lesion, intermediate in type between hepatocellular and cholangio-cellular carcinoma. The radiologic findings of cholangiolocellular carcinomas have not been reported. We describe the ultrasound, CT, MR, and angiographic findings of a case of cholangiolocellular carcinoma not associated with liver cirrhosis.

Radiologic and Histopathologic Evaluation of Various Contrast Media for Bronchography

PURPOSE: To determine which contrast media are both efficient and safe for the imaging of airways. MATERIALS AND METHODS: We evaluated five contrast media (barium, gastrografin, iotrolan, ioxaglate, iopentol) in terms of image quality and their effects on the lungs of 25 white rabbits. For bronchography 0.5ml of contrast media was used. In each contrast group, HRCT scans were obtained immediately (n=5), 12 hours (n=4), 1 day (n=3), 2 days (n=2), and 1 week (n=1) after bronchography. Histopathologic specimens were obtained immediately, 12 hours, 1 day, 2 days, and 1 week later. Bronchograms were evaluated for image quality by three radiologists working independently, and were scored as 1(poor), 2(moderate), or 3(good) in terms of contrast quality and bronchial coating. HRCT was evaluated by two radiologists who reached a concensus; they determined the presence of contrast media, and then the pattern and extent of pulmonary opacity, and any related changes. Histopatholgic specimens were evaluated by two pathologists who sought consensus as to the extent of inflammation, pulmonary edema, and hemorrhage, and any changes in these aspects. RESULTS: Bronchography indicated that the sum of scores for contrast quality was 45 for barium, 33 for gastrografin, 28 for iotrolan, 30 for ioxaglate, and 28 for iopentol, while for each of these media, the sum of scores for bronchial coating was 39, 19, 25, 23, and 21, respectively. Barium showed the best image quality. In all rabbits, HRCT demonstrated the variable extent of groundglass attenuation and/or consolidation. Lesions were most extensive at 1-2 days and then regressed at 1 week; these HRCT findings correlated well with histologic findings. In histologic studies of all five contrast media groups, variable severe inflammatory reactions were observed, with or without necrosis, congestion, edema, and hemorrhage. It was noted that ioxaglate appeared to cause least tissue reaction. CONCLUSIONS: The imaging results of this experimental study indicate that for bronchography, barium is the best available contrast media, On the basis of the histologic and HRCT results, however, ioxaglate is the best.

Optimal Scan Time of Dual-phase Spiral CT in Normal Rabbit Liver: Effect of Contrast Injection Rate

PURPOSE: To determine the effect of contrast injection rate on rabbit liver enhancement and the optimaltem-poral window for dual-phase spiral CT of rabbit liver at each injection rate. MATERIALS AND METHODS: Usingspiral CT, seven New Zealand White rabbits underwent dynamic scanning at one level of liver. Three protocols ofcontrast injection rates were employed, namely 0.3 ml/sec(group 1), 1ml/sec(group 2) and 2 ml/sec(group 3). During120 seconds of total scan time, the scan interval was 3 seconds. Densities of the aorta, liver and portal veinwere averaged in equivalent time. The different injection rate protocols were compared for peak enhancement/timeon a time density curve. RESULTS: Mean peak enhancement (HU) in equivalent time(secs) was 310/18(group 1),383/9(group 2) and 357/6(group 3) in the aorta ; 34/36, 40/36 and 41/30 in the liver ; and 135/36, 153/24 and170/21 in the portal vein. The temporal window during the arterial phase was 12-21 sec(group 1), 6-12 sec(group2), and 6-12 sec(group 3). The temporal window during the portal phase was from 30 sec(0.3ml/sec), 21sec(1ml/sec)and 21 sec(2 ml/sec). CONCLUSION: During dual-phase spiral CT, the temporal window for liver scanningshould be determined according to each contrast injection rate. A slow contrast injection rate prolongs thetemporal window during the arterial phase.