ФОРМУВАННЯ ГІДРОДИНАМІЧНОГО РЕЖИМУ В ЗОНІ ВПЛИВУ ВІДВАЛІВ ГІРСЬКИХ ПОРІД ТА ХВОСТОСХОВИЩ

За результатами моделювання з використанням тривимірної чисельної моделі, що комплексно відбиває планово-профільну фільтрацію в межах прони-кних і розділяючих шарів, встановлені закономірності геофільтрації у верхній частині породного масиву на ділянках розташування відвалів гірських порід і хвостосховищ. Виявлений характер впливу гідродинамічного режиму, що формується в умовах гравітаційно-навантаженого породного масиву, на гео-механічний стан прилеглої до об'єктів гірничого виробництва території. По результатам моделирования с использованием трехмерной численной модели, комплексно отражающей планово-профильную фильтрацию в пределах проницаемых и разделяющих слоев, установлены закономерности геофильтрации в верхней части породного массива на участках расположе-ния отвалов горных пород и хвостохранилищ. Определен характер влияния гидродинамического режима, формирующегося в условиях гравитационно-нагруженного породного массива, на геомеханическое состояние прилегаю-щей к объектам горного производства территории. The features of ground water flow have been determined for the top layers of the rock mass in dump tailing areas by numerical simulation using a model reproduc-ing 3D ground water flow within aquifers and confining layers. The impact of the hydrodynamic regime formed in the gravitationally loaded rock mass on geomechanical conditions of the territory affected by mining industry sites has been revealed

Effect of Contrast Agent Dose Reduction on Vascular Enhancement and Image Quality in Thoracoabdominal Dynamic 3-Dimensional Magnetic Resonance Angiography: A Systematic Intraindividual Analysis in Pigs

OBJECTIVE: High spatial and temporal resolution contrast-enhanced magnetic resonance angiography (MRA) with gadolinium-based contrast agents (GBCAs) at standard dose offers both detailed anatomic information on both arterial and venous vessels and hemodynamic characteristics. Several preclinical and clinical dynamic 3-dimensional (3D) MRA studies that focused on arterial vessels only proposed that high image quality may also be achieved with significantly reduced GBCA doses, calling into question the need to use standard doses. A systematic analysis of GBCA doses and resulting image quality for both arteries and veins has not yet been performed. The purpose of this study was therefore to systematically analyze dose-dependent vascular enhancements in dynamic 3D-MRA of the thoracoabdominal vasculature at 1.5 T in an animal model to determine the optimal contrast agent protocol for optimized vascular assessment. MATERIALS AND METHODS: The vascular enhancement in thoracoabdominal dynamic 3D-MRA (time-resolved angiography with interleaved stochastic trajectories, TWIST at 1.5 T) was interindividually and intraindividually compared in 5 anesthetized Göttingen minipigs using gadobutrol at the standard dose (0.1 mmol/kg body weight, ie, 0.1 mL/kg) and at reduced doses (0.08, 0.06, 0.04, 0.02 mmol/kg) in a randomized order. All injections were performed at 2 mL/s followed by 20 mL saline. Images were quantitatively analyzed, measuring signal intensities in 5 regions that covered the passage of the GBCA through the body at different representative stages of circulation (pulmonary, arterial, and venous system). The evaluation of GBCA dose-dependent signal intensity changes in the different vascular regions was performed by linear regression analysis.The qualitative image analysis of dynamic 3D-MRA by 3 independent radiologists included the visibility of 25 arterial and venous vessel segments at different stages of GBCA passage. Possible quality losses were statistically tested by comparing image quality ratings at the reduced dose with that of the standard dose using Friedman test followed by Dunn post hoc test for multiple comparison. Significance was stated at P < 0.05. RESULTS: Quantitative analysis revealed shorter time-to-peak intervals and bolus durations in line with decreasing GBCA dose and volume in all vessels. Although the peak signal was almost independent of the administered GBCA dose at the level of the pulmonary trunk, a linear signal decrease in the abdominal aorta ( r2 = 0.96), the renal arteries ( r2 = 0.99), the inferior vena cava ( r2 = 0.99), and the portal vein ( r2 = 0.97) was observed. Cumulative analysis of arterial segments revealed significantly lower image quality at doses below 40% of the standard dose, whereas in venous segments, significantly lower image quality was observed at doses below 60% of the standard dose. CONCLUSIONS: In dynamic 3D-MRA at 1.5 T, dose reduction leads to a signal loss that is most pronounced in the venous system and results in significantly lower image quality according to the dose and vessels of interest. Careful dose reduction is thus required according to the specific diagnostic needs. For dynamic 3D-MRA of the arterial and venous system, GBCA doses of at least 60% of the standard dose up to the full dose are preferable, whereas 40% of the standard dose seems feasible if only the arterial system is to be imaged

Mapping of Autogenous Saphenous Veins as an Imaging Adjunct to Peripheral MR Angiography in Patients with Peripheral Arterial Occlusive Disease and Peripheral Bypass Grafting: Prospective Comparison with Ultrasound and Intraoperative Findings

<div><p>Background</p><p>Mapping of the great saphenous vein is very important for planning of peripheral and coronary bypass surgery. This study investigated mapping of the great saphenous vein as an adjunct to peripheral MR angiography using a blood pool contrast agent in patients who were referred for evaluation of peripheral arterial occlusive disease and bypass surgery.</p><p>Methods</p><p>38 patients with peripheral arterial occlusive disease (21 men; mean age: 71 years, range, 44–88 years) underwent peripheral MR angiography using the blood pool contrast agent Gadofosveset trisodium. Apart from primary arterial assessment images were evaluated in order to determine great saphenous vein diameters at three levels: below the saphenofemoral junction, mid thigh and 10 cm above the knee joint (usability: diameter range: >3 and <10 mm at one level and >3.5 and <10 mm at a neighboring level). Duplex ultrasound was performed by an independent examiner providing diameter measurements at the same levels. Additionally, vessel usability was determined intraoperatively by the vascular surgeon during subsequent bypass surgery.</p><p>Results</p><p>Mean venous diameters for MR angiography/duplex ultrasound were 5.4±2.6/5.5±2.8 mm (level 1), 4.7±2.7/4.6±2.9 mm (level 2) and 4.4±2.2/4.5±2.3 mm (level 3), respectively, without significant differences between the modalities (<i>P</i> = 0.207/0.806/0.518). Subsequent surgery was performed in 27/38 patients. A suitable saphenous vein was diagnosed in 25 and non-usability was diagnosed in 2 of the 27 patients based on MR angiography/duplex ultrasound, respectively. Usability was confirmed by intraoperative assessment in all of the 24 patients that received a venous bypass graft in subsequent bypass surgery. In 1 case, in which the great saphenous vein was assessed as useable by both MR angiography and duplex ultrasound, it was not used during subsequent bypass surgery due to the patients clinical condition and comorbidities.</p><p>Conclusion</p><p>Simultaneous mapping of the great saphenous vein as an imaging adjunct to peripheral MR angiography with a blood pool contrast agent is an alternative to additive duplex ultrasound in patients undergoing subsequent peripheral bypass grafting.</p></div

Flowchart portraying the study design.

<p>Flowchart portraying the study design.</p

MR-angiographic and duplex sonographic images of the great saphenous vein.

<p>Magnetic resonance imaging (BPCA-MRA) and color-coded duplex sonography in the proximal level of the left GSV of a 69 year old male patient who suffered from ulcerations of the lower leg. (a, b) Axial multiplanar reformat of contrast-enhanced T1-weighted gradient-echo images during the steady-state. (c) Axial color-coded duplex sonography.</p

MR-angiographic and duplex sonographic images of the great saphenous vein.

<p>Magnetic resonance imaging (BPCA-MRA) and color-coded duplex sonography in the proximal level of the left GSV of a 63 year old female patient who suffered from PAOD stage III and was referred to the radiological department for assessment of the arterial status prior to a proposed bypass surgery. (a, b) Axial multiplanar reformat of contrast-enhanced T1-weighted gradient-echo images during the steady-state. (c) Axial color-coded duplex sonography.</p

Clinical and demographic characteristics of the study population.

<p>All patients were of white ethnicity.</p><p>Clinical and demographic characteristics of the study population.</p

Intraoperative measurement of the dissected great saphenous vein.

<p>Intraoperative measurement of the dissected great saphenous vein.</p

MR-angiographic protocol.

<p>Sequence flow of the combined first-pass and steady-state MR angiographic protocol and technical parameters of T1-weighted gradient-echo sequences for first-pass and steady-state MR angiography.</p

Correlation between MR-angiographic (MRA) and duplex sonographic (DUS) values in the three levels.

<p>Pearson correlation coefficients R²: level 1: 0.989; level 2: 0.986, level 3: 0.973.</p