Kidney volume quantification using contrast‐enhanced in vivo X‐ray micro‐CT in mice

The present study sought to establish a standard in vivo imaging procedure for mouse kidney anatomy evaluation using contrast‐enhanced high‐resolution X‐ray microtomography (micro‐CT). Micro‐CT estimation of kidney volume was compared with ex vivo measurement by micro‐CT and water displacement. Control values were obtained in four strains (BALB/c, C3H/HeN, 129/Sv and C57BL/6J) of healthy male and female mice aged 22 ± 2 weeks. An excellent correlation was found between in vivo and ex vivo kidney volumes (n = 26 mice; 52 kidneys; r = 0.96). In vivo measurement systematically overestimated ex vivo kidney volume by 28 ± 4%, while there was no significant difference between the ex vivo micro‐CT value and the true kidney volume on water displacement (2.3 ± 2.1%). In vivo kidney volume also correlated strongly with kidney weight and in vivo kidney length (n = 52 mice; 104 kidneys; r = 0.84, r = 0.92 respectively). Differences between strains were observed for kidney volume when comparing either kidney volume or kidney weight to body weight. In conclusion, this study demonstrated that contrast‐enhanced micro‐CT enables accurate in vivo measurement of kidney volume, length and thickness in mice. Reference parameters are reported for four strains. The technique provides a useful follow‐up research tool for mouse phenotyping and renal disease studies. Copyright © 2008 John Wiley & Sons, Ltd.     

Selective X‐ray contrast enhancement of the spleen of living mice mediated by gold nanorods

Gold nanomaterials (AuNPs) represent a promising new class of contrast agents for X‐ray computed tomographic (CT) imaging in both research and clinical settings. These materials exhibit superior X‐ray absorption properties compared with other iodinated agents, and thus require lower injection doses. Gold is nonimmunogenic and therefore contributes to safety profile in living specimens. Unfortunately, most reports on the use of AuNPs as X‐ray CT enhancers only demonstrate marginal enhancement of the intended anatomical structure. In this study, we demonstrate the dramatic properties of gold nanorods (GNR) to serve as robust X‐ray CT contrast‐enhancing agent for selective imaging of the spleen. These organ‐specific uptake properties were delineated by performing longitudinal CT imaging of living mice that were dosed with GNR at 2 day intervals. Rapid uptake in spleen was noted within 12 h of first systemic administration with a change in contrast enhancement of 90 Hounsfield units (ΔHU = 90) and with two subsequent injections a total contrast enhancement of over 200 HU was observed. The resulting images provide excellent contrast that will enable the detailed anatomical visualization and study of a range of pre‐clinical models of spleen disease including infection and cancer. Copyright © 2014 John Wiley & Sons, Ltd.     

Serine‐ and mannose‐modified liposomal contrast agent for computed tomography: evaluation of the enhancement in rabbit liver VX‐2 tumor model

Kupffer cell imaging is a powerful tool for the detection of liver cancer. This diagnostic procedure depends on the faculty of the reticuloendothelial system (RES) which takes up foreign bodies, including small particles. The current study aimed to develop a novel RES targeting liposomal contrast agent that functionalized with serine or mannose, the moiety specifically binding to a corresponding receptor on phagocytic cells. Liposomes loaded with non‐ionic X‐ray contrast media, Iohexol, were prepared by supercritical carbon dioxide reverse‐phase evaporation method and were intravenously injected to healthy rabbits in order to evaluate the liver parenchymal enhancement in X‐ray computed tomography (CT). From 10 to 40 min after injection, the mean enhancement value of the liver parenchyma approached 45 and 34 Hounsfield units (HU) when serine‐modified iodinated liposomal contrast agent (ILCA) and mannose‐modified ILCA were applied, respectively. The tumor‐to‐liver contrast values were also evaluated after the administration of the prepared ILCA to rabbits with VX‐2 carcinoma. For serine‐modified ILCA, tumor‐to‐liver contrast was 82 HU at 1 min and >24 HU at 10–40 min; for mannose‐modified ILCA, the values were 58 HU at 0.5 min and >21 HU at 10–40 min. These vales estimated from the region of intrest and the imaging figures of liver indicate the potential of ILCA for clinical use. Copyright © 2010 John Wiley & Sons, Ltd.     

Anatomical and functional imaging of myocardial infarction in mice using micro‐CT and eXIA 160 contrast agent

Noninvasive small animal imaging techniques are essential for evaluation of cardiac disease and potential therapeutics. A novel preclinical iodinated contrast agent called eXIA 160 has recently been developed, which has been evaluated for micro‐CT cardiac imaging. eXIA 160 creates strong contrast between blood and tissue immediately after its injection and is subsequently taken up by the myocardium and other metabolically active tissues over time. We focus on these properties of eXIA and show its use in imaging myocardial infarction in mice. Five C57BL/6 mice were imaged ~2 weeks after left anterior descending coronary artery ligation. Six C57BL/6 mice were used as controls. Immediately after injection of eXIA 160, an enhancement difference between blood and myocardium of ~340 HU enabled cardiac function estimation via 4D micro‐CT scanning with retrospective gating. Four hours post‐injection, the healthy perfused myocardium had a contrast difference of ~140 HU relative to blood while the infarcted myocardium showed no enhancement. These differences allowed quantification of infarct size via dual‐energy micro‐CT. In vivo micro‐SPECT imaging and ex vivo triphenyl tetrazolium chloride (TTC) staining provided validation for the micro‐CT findings. Root mean squared error of infarct measurements was 2.7% between micro‐CT and SPECT, and 4.7% between micro‐CT and TTC. Thus, micro‐CT with eXIA 160 can be used to provide both morphological and functional data for preclinical studies evaluating myocardial infarction and potential therapies. Further studies are warranted to study the potential use of eXIA 160 as a CT molecular imaging tool for other metabolically active tissues in the mouse. Copyright © 2014 John Wiley & Sons, Ltd.     

Dynamic contrast‐enhanced computed tomography for the quantification of tumor response to vasoactive agents in a rat tumor model: preliminary results

Rationale and Objectives

The purpose of this pilot study was to establish the ability of dynamic contrast enhanced computed tomography (DCE‐CT) to detect changes in tumor blood flow (BF) and oxygenation induced by vasoactive substances in rats.

Materials and Methods

Under ultrasound guidance, a fiber‐optic probe was guided into thigh tumors in eight rats and attached to an oxygenation/blood flow‐sensing device. A DCE‐CT sequence was acquired at the oxygen‐sensing probe tip during injection of iodinated contrast media. Group 1 rats (n = 6) were administered a vasodilator (hydralazine, 5 mg/kg i.v.) and group 2 rats (n = 2) were given physiologic saline in a similar volume. DCE‐CT was repeated at the probe tip after 30 min. BF in the whole tumor and at the probe tip were estimated pre‐ and post‐drug administration and the percentage change was calculated.

Results

DCE‐CT defined significant differences between pre‐ and post‐drug BF in the whole tumor (p = 0.007) and at the probe tip (p = 0.03). Estimates of percentage change in BF in the whole tumor agreed with fiber‐optic measure of percentage change perfusion (r² = 0.60; p = 0.02) and pO₂ (r² = 0.65; p = 0.02). Estimates of percentage change in BF at the probe tip agreed with fiber‐optic measures of percentage change in perfusion (r² = 0.83; p = 0.001) and pO₂ (r² = 0.62; p = 0.02).

Conclusions

Preliminary results indicate that DCE‐CT is capable of identifying alterations in tumor BF in rats. The percentage change in BF agrees with a validated estimate of tumor perfusion and oxygenation. This research technique may prove useful for assessment of tumor BF during combined chemotherapeutic and radiation therapy to improve outcome. Copyright © 2010 John Wiley & Sons, Ltd.     

MRI tumor characterization using Gd‐GlyMe‐DOTA‐perfluorooctyl‐mannose‐conjugate (Gadofluorine M™), a protein‐avid contrast agent

The rationale and objectives were to define the MRI tumor‐characterizing potential of a new protein‐avid contrast agent, Gd‐GlyMe‐DOTA‐perfluorooctyl‐mannose‐conjugate (Gadofluorine M?; Schering AG, Berlin, Germany) in a chemically induced tumor model of varying malignancy. Because of the tendency for this agent to form large micelles in water and to bind strongly to hydrophobic sites on proteins, it was hypothesized that patterns of dynamic tumor enhancement could be used to differentiate benign from malignant lesions, to grade the severity of malignancies and to define areas of tumor necrosis. Gadofluorine M, 0.05 mmol Gd kg^?1, was administered intravenously to 28 anesthetized rats that had developed over 10 months mammary tumors of varying degrees of malignancy as a consequence of intraperitoneal administration of N‐ethyl‐N‐nitrosourea (ENU), 45–250 mg kg^?1. These tumors ranged histologically from benign fibroadenomas to highly undifferentiated adenocarcinomas. Dynamic enhancement data were analyzed kinetically using a two‐compartment tumor model to generate estimates of fractional plasma volume (fPV), apparent fractional extracellular volume (fEV*) and an endothelial transfer coefficient (K^PS) for this contrast agent. Tumors were examined microscopically for tumor type, degree of malignancy (Scarff–Bloom–Richardson score) and location of necrosis. Eighteen tumor‐bearing rats were successfully imaged. MRI data showed an immediate strong and gradually increasing tumor enhancement. K^PS and fEV*, but not fPV obtained from tumors correlated significantly (p < 0.05) with the SBR tumor grade, r = 0.65 and 0.56, respectively. Estimates for K^PS and fEV* but not fPV were significantly lower in a group consisting of benign and low‐grade malignant tumors compared with the group of less‐differentiated high‐grade tumors (1.61 ± 0.64 vs 3.37 ± 1.49, p < 0.01; 0.45 ± 0.17 vs 0.78 ± 0.24, p < 0.01; and 0.076 ± 0.048 vs 0.121 ± 0.088, p = 0.24, respectively). It is concluded that the protein‐avid MRI contrast agent Gadofluorine M enhances tumors of varying malignancy depending on the tumor grade, higher contrast agent accumulation for more malignant lesions. The results show potential utility for differentiating benign and low‐grade malignant lesions from high‐grade cancers. Copyright © 2006 John Wiley & Sons, Ltd.     

Utilization of nanoparticles as X‐ray contrast agents for diagnostic imaging applications

Among all the diagnostic imaging modalities, X‐ray imaging techniques are the most commonly used owing to their high resolution and low cost. The improvement of these techniques relies heavily on the development of novel X‐ray contrast agents, which are molecules that enhance the visibility of internal structures within the body in X‐ray imaging. To date, clinically used X‐ray contrast agents consist mainly of small iodinated molecules that might cause severe adverse effects (e.g. allergies, cardiovascular diseases and nephrotoxicity) in some patients owing to the large and repeated doses that are required to achieve good contrast. For this reason, there is an increasing interest in the development of alternative X‐ray contrast agents utilizing elements with high atomic numbers (e.g. gold, bismuth, ytterbium and tantalum), which are well known for exhibiting high absorption of X‐rays. Nanoparticles (NPs) made from these elements have been reported to have better imaging properties, longer blood circulation times and lower toxicity than conventional iodinated X‐ray contrast agents. Additionally, the combination of two or more of these elements into a single carrier allows for the development of multimodal and hybrid contrast agents. Herein, the limitations of iodinated X‐ray contrast agents are discussed and the parameters that influence the efficacy of X‐ray contrast agents are summarized. Several examples of the design and production of both iodinated and iodine‐free NP‐based X‐ray contrast agents are then provided, emphasizing the studies performed to evaluate their X‐ray attenuation capabilities and their toxicity in vitro and in vivo. Copyright © 2014 John Wiley & Sons, Ltd.     

In vivo comparison of tantalum,tungsten, and bismuth enteric contrast agents to complement intravenous iodine for double‐contrast dual‐energy CT of the bowel

To assess the ability of dual‐energy CT (DECT) to separate intravenous contrast of bowel wall from intraluminal contrast, we scanned 16 rabbits on a clinical DECT scanner: n = 3 using only iodinated intravenous contrast, and n = 13 double‐contrast enhanced scans using iodinated intravenous contrast and experimental enteric non‐iodinated contrast agents in the bowel lumen (five bismuth, four tungsten, and four tantalum based). Representative image pairs from conventional CT images and DECT iodine density maps of small bowel (116 pairs from 232 images) were viewed by four abdominal imaging attending radiologists to independently score each comparison pair on a visual analog scale (?100 to +100%) for (1) preference in small bowel wall visualization and (2) preference in completeness of intraluminal enteric contrast subtraction. Median small bowel wall visualization was scored 39 and 42 percentage points (95% CI 30–44% and 36–45%, both p < 0.001) higher for double‐contrast DECT than for conventional CT with enteric tungsten and tantalum contrast, respectively. Median small bowel wall visualization for double‐contrast DECT was scored 29 and 35 percentage points (95% CI 20–35% and 33–39%, both p < 0.001) higher with enteric tungsten and tantalum, respectively, than with bismuth contrast. Median completeness of intraluminal enteric contrast subtraction in double‐contrast DECT iodine density maps was scored 28 and 29 percentage points (95% CI 15–31% and 28–33%, both p < 0.001) higher with enteric tungsten and tantalum, respectively, than with bismuth contrast. Results suggest that in vivo double‐contrast DECT with iodinated intravenous and either tantalum‐ or tungsten‐based enteric contrast provides better visualization of small bowel than conventional CT. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluation of eXIA 160XL cardiac‐related enhancement in C57BL/6 and BALB/c mice using micro‐CT

Evaluation of cardiovascular function in mice using micro‐CT requires that a contrast agent be administered to differentiate the blood from the myocardium. eXIA 160XL, an aqueous colloidal poly‐disperse contrast agent with a high iodine concentration (160 mg I ml^?1), creates strong contrast between blood and tissue with a low injection volume. In this study, the blood‐pool enhancement time‐course of eXIA 160XL is monitored over a 48 h period to determine its optimal use during cardiac function studies in C57BL/6 and BALB/c mice. Eight‐second scans were performed (80 kV_p, 110 mA) using the GE Locus Ultra micro‐CT scanner. Six C57BL/6 and six BALB/c male mice (22–24 g) were injected via tail vein with 5 µl g^?1 body weight eXIA 160XL. A precontrast scan was performed; following injection, mice were scanned at 5, 15, 30, 45 and 60 min, and 2, 4, 8, 12, 24 and 48 h. Images were reconstructed, and enhancement–time curves were generated for each of the following tissues: left ventricle (LV), myocardium, liver, spleen, renal cortex, bladder and brown adipose tissue. The highest contrast in the LV occurred at 5 min in both strains (~670 HU above precontrast value). Uptake of the contrast agent by the myocardium was also observed: myocardial tissue showed increasing enhancement over a 4 h period in both strains, remaining even once the contrast was eliminated from the vasculature. In both C57BL/6 and BALB/c strains, eXIA 160XL provided high contrast between blood and myocardial tissue for a period of 30 min following injection. Notably, this contrast agent was also taken up by the myocardium and provided continued enhancement when it was eliminated from the blood, making LV wall motion studies possible. In conclusion, eXIA 160XL, with its high iodine concentration and targeted tissue uptake characteristics, is an ideal agent to use when evaluating cardiovascular function in mice. Copyright © 2012 John Wiley & Sons, Ltd.     

Extracellular matrix deposition and scaffold biodegradation in an in vitro three‐dimensional model of bone by X‐ray computed microtomography

The development of an in vitro model of bone and the optimization of tools for determining the biological processes occurring during bone repair remains a major goal in the field of bone tissue engineering. Recently, a model based on a three‐dimensional co‐culture of osteoblasts and osteoclast precursors in Skelite^TM scaffolds was developed. Although induction of osteoblast and osteoclast differentiation was observed, a complete evaluation of bone deposition and biodegradation processes was missing due to technical limitations. In the current study, both X‐ray computed microtomography and histological analysis were used to monitor these two key biological processes in the same in vitro model. Either osteoblasts or a combination of osteoblasts and osteoclasts were seeded on Skelite^TM scaffolds. Scaffold biodegradation and increased bone deposition together with a more organized extracellular matrix were observed in the co‐cultures, highlighting the role of osteoclasts in the determination and regulation of bone deposition. Results confirmed the potential and relevance of co‐culturing osteoblasts and osteoclasts to resemble native tissue. The combination of X‐ray computed microtomography and histology presented in this study could be useful in future studies for the validation and development of new in vitro culture systems for bone tissue engineering. Copyright © 2012 John Wiley & Sons, Ltd.     

How transfer rates generate Gd‐BOPTA concentrations in rat liver compartments: implications for clinical liver imaging with hepatobiliary contrast agents

Following the injection of hepatobiliary contrast agents, MRI detects all molecules included in a region of interest but cannot estimate true concentrations in sinusoids, interstitium, hepatocytes or bile canaliculi. The aim of the study was to measure true concentrations in hepatocytes and to show how transfer rates across sinusoidal and canalicular membranes generate these concentrations. We perfused livers isolated from normal rats with 200 μM Gd‐DTPA and Gd‐BOPTA and measured clearances from sinusoids to liver and from hepatocytes to bile canaliculi or back to interstitium. We detected Gd‐BOPTA with a gamma probe and determined true concentrations in each liver compartment knowing their liver volumes. No pharmacokinetic modelling was applied. Gd‐BOPTA clearance from sinusoids to liver (2.5 ± 0.4 mL/min) was 50 times higher than that of Gd‐DTPA (0.05 ± 0.02 mL/min) when portal flow rate was 30 mL/min (p < 0.0001). Gd‐BOPTA clearance from sinusoids to liver was always superior to hepatocyte clearance, and hepatocyte Gd‐BOPTA concentrations measured by the probe increased over time. Gd‐BOPTA concentrations reached 439 ± 83 μM in hepatocytes and 15 × 700 ± 3100 μM in bile canaliculi, while concentrations in sinusoids were 200 μM. Gd‐BOPTA true concentrations in hepatocytes depend on the simultaneous clearances from sinusoids to hepatocytes and from hepatocytes to bile canaliculi and back to sinusoids. The study better defines how signal intensities are generated when hepatobiliary contrast agents are injected in clinical imaging. Copyright © 2016 John Wiley & Sons, Ltd.     

Sonographic assessment of the normal limits and percentile curves of liver, spleen, and kidney dimensions in healthy school-aged children.

OBJECTIVE: The purpose of this study was to determine the normal standards of liver, spleen, and kidney dimensions and the relationship of each with sex, age, body weight, height, body mass index, and body surface area in healthy school-aged children. METHODS: Seven hundred twelve healthy school-aged children (7-15 years) in 2 neighboring cities, including rural areas and city centers, were evaluated prospectively. Sex, age, weight, height, body mass index, and body surface area were determined for each case. Organ dimensions were measured 3 times, and the mean values were recorded. All measured organs had a normal position, shape, and echo texture. The children were separated into 5 groups according to body weight. RESULTS: There were no significant differences in organ dimensions with respect to sex (P > .05). The mean right kidney length was shorter than the left kidney length, and the difference was significant (P = .009). Body weight showed the best correlation with liver, spleen, and kidney dimensions. The results were also supported by the variance and covariance of the correlation coefficients. CONCLUSIONS: The normal limits of the liver, spleen, and kidneys are important parameters during a sonographic examination. This study revealed that organ dimensions showed the best correlation with body weight. To our knowledge, in clinical practice there are no pediatric organ dimension percentile graphs for interpretation of sonographic examinations. We hope this study contributes to daily practice in radiology clinics.     

In vivo high‐resolution 3D Overhauser‐enhanced MRI in mice at 0.2 T

Overhauser‐enhanced MRI (OMRI) offers the potentiality of detecting low‐concentrated species generated by specific biological processes. However molecular imaging applications of OMRI need significant improvement in spatial localization. Here it is shown that 3D‐OMRI of a free radical injected in tumor‐bearing mice can be performed at high anatomical resolution at a constant field. A 30 mm cavity operating at 5.43 GHz was inserted in a C‐shaped magnet for proton MRI at 0.194 T. Nude mice with or without brain‐implanted C6 rat glioma were positioned in the cavity and injected with TOPCA (1‐oxyl‐2,2,5,5‐tetramethyl‐2,5‐dihydro‐1H‐pyrrole‐3‐carboxylic acid). OMRI was performed in 3D within several minutes in the brain region without high overheating of the animals. Voxel size was 0.5 × 0.5 × 1 mm³, providing good delineation of brain regions. Signal amplifications ranged from 2 in tumors to 10 in vessels several minutes after TOPCA injection. Time‐course of signal enhancement could be measured by 2D OMRI at 15 s time intervals in a localized thin slice. The method opens the way for molecular imaging of biological activities able to generate OMRI‐visible free radicals. Copyright © 2012 John Wiley & Sons, Ltd.     

Contrast‐enhanced sonography for screening of vascular complication in recipients following living donor liver transplantation

The purpose of this article is to discuss the role of CEUS for screening of vascular complication in recipients admitted to ICU following LDLT, effect of microbubble contrast agent on Doppler phenomenon, CEUS technique, and illustrate CEUS findings in recipients with complication following LDLT. CEUS can enhance the role of US in the diagnosis of postoperative vascular complication in recipients following living donor liver transplantation at the bedside. © 2013 Wiley Periodicals, Inc. J Clin Ultrasound, 41:305–312, 2013     

细胞因子信号转导抑制因子-1在脓毒症小鼠肝脏和脾脏中表达的研究

目的 观察细胞因子信号转导抑制因子-1(SOCS1)在脓毒症小鼠肝脏和脾脏中的变化情况,探讨SOCS在体内的可能作用机制.方法 采用盲肠结扎穿孔术(CLP)制备脓毒症小鼠模型.提取肝脏和脾脏组织的总RNA及蛋白,采用逆转录-聚合酶链反应(RT-PCR)技术测定组织中SOCS1 mRNA的相对含量;用免疫印迹法测定组织中SOCS1相对蛋白含量;用SPSS统计软件分析上述指标之间的变化关系.结果 脓毒症小鼠术后6 h肝组织SOCS1的基因和蛋白表达均迅速升高,基因表达至24 h达到高峰(P＜0.05),蛋白表达一直保持高位;在脾脏中仅检测到SOCS1基因表达,随时间延长逐渐上升,并一直保持高位;肝脏中SOCS1的基因和蛋白表达量间呈明显正相关(y=0.110±5.765×10-3x,r=0.837,F=93.309,P＜0.01).结论 CLP导致的脓毒症可诱导SOCS1在肝脏和脾脏中进一步表达,提示SOCS1在脓毒症出现后的免疫变化中有重要作用,可利用它们对脓毒症进行干预,以改善脓毒症的预后.