Renal hemodynamics and oxygenation in transient renal artery occluded rats evaluated with iron-oxide particles and oxygenation-sensitive imaging.

INTRODUCTION: Mild or severe renal arterial occlusion is a phenomenon occasionally observed in daily clinical practice, potentially leading to renal ischemia and a general impairment of renal function. Secondly, closing the blood flow to the kidneys can also occur during kidney transplantation procedures. However, the exact physiological effects of these conditions on renal blood perfusion as well as the renal oxygen handling are poorly understood. The objectives of this study were therefore to measure the lateral changes of renal blood perfusion in rats subjected to transient unilateral arterial occlusion (RAS), and in addition, to measure the consequences on the intrarenal oxygenation. METHODS: Experimental studies were performed using sixteen adolescent rats. The left renal artery was exposed through a flank incision and acute RAS for 45 min was achieved by placing a ligature around the renal artery. MRI was performed 3 days after the surgical procedure, where a blood oxygenation sensitive sequence (BOLD MRI) was performed, followed by a perfusion-weighted imaging sequence using a single bolus of the iron-oxide nanoparticle Sinerem. The renal oxygenation of blood was indirectly measured by the BOLD-parameter R2*, and perfusion measures include relative renal blood flow, relative renal blood volume and mean transit time. Histopathologic changes through the outer stripe of the outer medulla showing typical histopathologic findings of ischemia. DISCUSSION: This study demonstrated that rats with transient renal arterial stenosis (for 45 min) showed a reduction in intrarenal oxygenation and intrarenal blood flow three days after the surgical procedure. A decreased R2* was measured within the ipsilateral medulla in parallel with a decreased medullary blood flow, is probably related to a lower reabsorption load within the ipsilateral kidney. MRI may therefore be a promising tool in long-term evaluation of RAS.

Combined radiofrequency ablation and antiangiogenic drug for the treatment of recurrent renal tumor.

The efficacy of radiofrequency ablation of large renal tumors can be increased by modulating their size and vascularity with antiangiogenic drugs, which may limit the sink effect related to high blood flow. We present an observation with 3 recurrent tumor locations, the largest being 3.7 cm in diameter. Pretreatment with antiangiogenics provided a significant reduction of tumor size and perfusion, allowing efficient ablation under favorable conditions.

Update of renal imaging.

Significant technical improvements have allowed the use of radiological techniques to play a growing role in the imaging of renal diseases. Noninvasive ultrasound methods (ie, sonography and Doppler) are now positioned as first-line methods for the evaluation of renovascular diseases. Multidetector computed tomography is able to provide high spatial resolution images of the kidneys and renal arterial vessels. Magnetic resonance imaging, which provides higher signal-to-noise ratio and higher spatial and/or temporal resolution, can display both morphological information about renal parenchyma and vessels and functional data, including perfusion, filtration, diffusion, or oxygenation. In renovascular diseases, these techniques have the potential to drive new strategies, including Doppler sonography as a first-line method, followed by computed tomography angiography or magnetic resonance angiography, depending mainly on renal function. Imaging of parenchymal renal diseases is developing toward more quantitative (volumetric and functional measurements) and more specific (through in vivo cell targeting) acquisitions for obtaining the adequate information on tissue characteristics relevant either for diagnosis or for prognosis or treatment follow-up.

Airway wall thickness in cigarette smokers: quantitative thin-section CT assessment.

PURPOSE: To design and validate a dedicated software tool to measure airway dimensions on thin-section computed tomographic (CT) images and to use the tool to prospectively compare airway wall thickness in nonsmokers with normal lung function with that in smokers with and without chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: All subjects gave written informed consent. The study was approved by local ethics committee. With Laplacian of Gaussian algorithm, software was tested in phantom and excised sheep lung fixed in inflation and validated with Bland-Altman analysis. Study prospectively included nine nonsmokers (six women, three men; mean age, 53 years +/- 5.6 [standard error of the mean]) with normal lung function (group 1), seven smokers (three women, four men; mean age, 56 years +/- 5.6) with normal lung function (group 2), and eight smokers (zero women, eight men; mean age, 65 years +/- 4.0) with COPD. Calculations were determined with spirometrically gated CT: For each selected bronchus, the wall area (WA), internal area (IA), airway caliber (sum of IA and WA), and WA/IA ratio were calculated. For each patient, summation of WA to summation of IA (SigmaWA/SigmaIA) ratio, which reflected normalized airway wall thickness, was calculated. Groups were compared by using analysis of variance with generalized linear model and unpaired t test. Pearson correlation coefficient was used to assess correlation between software measurements and pulmonary function test results. RESULTS: Comparison of measurements in phantom and excised sheep lung with algorithm measurements revealed that the latter were reliable and repeatable. In clinical study, SigmaWA/SigmaIA ratio was significantly different among three groups (P < .001). Normalized airway wall thickness and IA were significantly related to lung function test data, including forced expiratory volume in 1 second (r = -0.54, P = .006), specific airway conductance (r = -0.45, P = .03), and forced expiratory flow between 25% and 75% of vital capacity (r = -0.65, P < .001). CONCLUSION: This software provides accurate and reproducible measurements of IA and WA of bronchi on thin-section CT images and demonstrates that in vivo normalized airway wall thickness was larger in smokers with COPD than it was in smokers or nonsmokers without COPD.

Structure and function of small airways in smokers: relationship between air trapping at CT and airway inflammation.

PURPOSE: To use quantitative computed tomography (CT) to compare lung attenuation with both inflammatory infiltration and in vitro reactivity of peripheral airways in smokers scheduled to undergo lung resection for localized pulmonary lesions. MATERIALS AND METHODS: Attenuation was measured in nine ex-smokers, 13 current smokers, and eight nonsmoking control subjects by using CT with respiratory gating and a contour-tracing algorithm. After lung resection in smokers, peripheral bronchi were dissected and studied in terms of both inflammation (by using immunohistochemistry to examine glycolmethacrylate-embedded specimens) and mechanical activity (by using an isolated organ bath system). Comparisons between groups were made by using analysis of variance and subsequent unpaired t tests. Correlations were evaluated by using the Pearson coefficient and stepwise multiple regression analysis. RESULTS: The difference between inspiratory and expiratory attenuation was significantly higher in control subjects (-128 HU +/- 11 [SD]) than in ex-smokers (-77 HU +/- 10; P =.004) or current smokers (-67 HU +/- 11; P =.001). Cells infiltrating the smooth muscle increased with the decrease in expiratory attenuation (r = -0.46; P =.03) and the increase in inspiratory versus expiratory attenuation (r = 0.66; P =.001). Mast cell and neutrophil infiltration of smooth muscle was the most important factor in this relationship. Cellular infiltration of the smooth muscle increased with the decrease of in vitro relaxation response to salbutamol. CONCLUSION: In smokers, air trapping is correlated with inflammatory infiltration of the smooth muscle layer of small airways.