Utility of contrast-enhanced ultrasonography for qualitative imaging of atherosclerosis in Watanabe heritable hyperlipidemic rabbits: initial experimental study.

PURPOSE: Using Watanabe heritable hyperlipidemic (WHHL) rabbits, we investigated the ability of ultrasonography (US) to detect contrast enhancement of atherosclerotic lesions after intravenous injection of a microbubble contrast agent (MB) and confirmed the localization of MB in the lesion by transmission electron microscopy (TEM). MATERIALS AND METHODS: The abdominal aortic wall of six WHHL rabbits was observed for 20 min after MB delivery. To evaluate contrast enhancement, a region of interest (ROI) was set in the intima-media complex (IMC) and the aortic lumen. The average image brightness of the ROI was recorded as the echogenicity at each time point. Differences at each time point were analyzed by analysis of variance and the t-test. Histological analysis was performed after US observation. RESULTS: The echogenicity of the IMC was 8.48 ± 3.01 before and 10.96 ± 7.88, 32.42 ± 12.79, 79, 17.73 ± 9.118, and 31.18 ± 13.35, respectively, at 0.5, 2, 5, 10, and 20 min after MB injection. The echogenicity of the vessel lumen was 1.16 ± 1.57, 64.21 ± 11.52, 53.55 9.81, 13.32 ± 9.78, 2.63 ± 1.45, and 3.66 ± 3.01 at the corresponding time points. At 20 min after injection, the echogenicity of the IMC was significantly higher than before or 0.5 min after injection. The distribution of MB inside macrophages in atherosclerotic plaques could not be confirmed by TEM. CONCLUSION: Ultrasonography was able to detect contrast enhancement of the IMC at 10 and 20 min after injection of MB.

Degradable Gelatin Microspheres as an Embolic Agent: an Experimental Study in a Rabbit Renal Model

OBJECTIVE: To investigate the basic characteristics of degradable gelatin microspheres (GMSs), including their embolic behavior and degradation periods when they are used as embolic materials in the renal arteries of rabbit models. MATERIALS AND METHODS: Based on the GMS particle size, 24 kidneys were divided into 3 groups of eight kidneys, and each group was embolized with a different GMS particle size (group 1: 35-100 micrometer, group 2: 100-200 micrometer, and group 3: 200-300 micrometer). From each group, two rabbits were sacrificed immediately after embolization (day 0), and a pair of rabbits from each group underwent an angiogram and were sacrificed on days 3, 7, and 14, respectively, after embolization. The level of arterial occlusion, the pathological changes in the renal parenchyma, and the degradation of the GMSs were evaluated angiographically and histologically. RESULTS: A follow-up angiogram on days 0, 3, 7, and 14 revealed the presence of wedge-shaped poorly-enhanced areas in the parenchymal phase as seen in all groups. The size of these areas tended to increase with the particle diameter, and persisted up to day 14. On days 3, 7, and 14, parenchymal infarctions were observed histologically in all cases, and this observation corresponded with the parenchyma being supplied by the embolized arteries. GMSs of group 1 mainly reached the interlobular arteries, while those of group 3 mainly reached the interlobar arteries. In all but two cases, the GMSs were identified histologically even on day 14, and sequential degradation was histologically identified in all GMS groups. CONCLUSION: GMSs can be used as degradable embolic materials which can control the level of embolization.

Detectability of Various Sizes of Honeycombing Cysts in an Inflated and Fixed Lung Specimen: the Effect of CT Section Thickness

OBJECTIVE: We wanted to clarify the relationship between the visibility of air cysts on CT images, the CT slice thickness and the size of the air cysts, with contact radiographs as the gold standard, for the accurate evaluation of honeycomb cysts. MATERIALS AND METHODS: An inflated and fixed autopsied lung having idiopathic interstitial pneumonia was evaluated. The corresponding air cysts were identified on the contact radiographs of a 0.5 mm-thick-section specimen and also on the CT images of three different kinds of section thickness: 0.5, 1.0 and 2.5 mm. The maximal diameters of the air cysts were measured under a stereomicroscope. RESULTS: A total of 341 air cysts were identified on the contact radiograph, and they were then evaluated. Sixty-six percent of air cysts 1 to 2 mm in diameter were detected by 0.5 mm slice thickness CT, while only 34% and 8% were detected by 1.0 and 2.5 mm slice thickness CT, respectively. Only 28% and 22% of air cysts less than 1 mm in diameter were detected by 0.5 and 1.0 mm slice thickness CT, respectively. CT with a 2.5 mm slice thickness could not demonstrate air cysts less than 1 mm in diameter. CONCLUSION: The CT detection rate of honeycombing is significantly influenced both by the slice thickness and the size of the air cysts.