Water-saving strategies in the mining industry - The potential of mineral processing simulators as a tool for their implementation.

As the mining industry is facing an increasing number of issues related to its fresh water consumption, water-saving strategies are progressively being implemented in the mineral processing plants, often leading to variations in the process water chemistry. However, the impact of water chemistry variations on the process performance is rarely known beforehand, thus creating an obstacle to the implementation of those water-saving strategies. To tackle this problem, the effect the different dissolved species present in the process water have on the processing plant performance must be quantified, and this information must be digitalized in a practical and suitable form to be used in mineral processing simulators. To achieve this goal, a methodology to digitalize the influence of the process water composition on the flotation performance is presented in this paper. Using the flotation of a fluorite ore as case study, the relationship between process water composition and the flotation kinetics of that fluorite ore was determined. This relationship was digitalized in HSC Sim, a mineral processing simulator, turning it into a tool capable of simulating the flotation performance under a variety of process water compositions. Finally, the potential of this new tool to help implementing water-saving strategies on the mine site is discussed, and the challenges that need to be overcome in order to apply this tool at industrial scale are being addressed.

3D evaluation of myocardial edema: experimental study on 22 pigs using magnetic resonance and tissue analysis.

BACKGROUND: Myocardial edema (ME) adversely affects ventricular function. Thus, we performed an animal study to demonstrate (1) 3D-ME using magnetic resonance imaging (MRI), which can show ME depending on myocardial location, (2) type of cardioplegic solution, and (3) quantification tools. METHODS: Pig hearts (n = 22) were perfused using Bretschneider's solution (BRET, n = 8), butanedionemonoxime (BDM, n=8), or no cardioplegia as controls (CTRL, n = 6). Hearts underwent MRI (T(1)-inversion recovery). Myocardial water content (MWC, reference method) was determined from left ventricle anterior, posterior (PW), lateral wall, interventricular septum, papillary muscle, right ventricle wall. Images underwent 3D reconstruction using ray-tracing. Gray-value analysis was performed on "virtual" samples. For statistical analysis, ANOVA, Student's t-test, and the Student-Newman-Keuls test were used. RESULTS: (1) ME was induced (p < 0.0001 vs. control). Localization differed in MWC, p = 0.003 (BRET), p = 0.023 (BDM), highest at PW (p < 0.01). (2) Differences between the cardioplegia groups were not significant. (3) "Virtual" samples showed equal distribution (BRET: p = 0.007, BDM: p = 0.003), highest at PW (p < 0.01). CONCLUSIONS: We validated 3D assessment of induced ME in pig hearts using MRI. The method may therefore become an exact tool in monitoring cardioplegia.

Evaluation of breath-hold contrast-enhanced 3D magnetic resonance angiography technique for imaging visceral abdominal arteries and veins.

RATIONALE AND OBJECTIVES: To evaluate the diagnostic value of breath-hold contrast-enhanced 3D magnetic resonance angiography (MRA) for assessment of the visceral abdominal arteries and veins in patients with suspected abdominal neoplasms. METHODS: Twenty-one patients underwent MR imaging on a 1.5 T unit using a body phased-array coil. MRA was performed with a 3D-FLASH sequence (TR 3.8 ms, TE 1.3 ms, flip angle 25 degrees, acquisition time 20 seconds), 8 to 12 seconds after an intravenous bolus injection of Gd-DTPA. The acquisition delay between the arterial and the portal venous phase was 12 seconds. The image quality and the degree of vascular involvement were evaluated using coronal source images and maximum intensity projection reconstructions. Diagnosis was confirmed by surgery/histology. RESULTS: Image quality was optimal in more than 85% of the patients (19/21 arterial phase and 17/21 portal venous phase). MRA correctly predicted vascular status in 20 of 21 patients (95%), with complete concordance between MRA results and surgical findings. In one patient with chronic pancreatitis, MRA demonstrated a false-positive finding that could not be confirmed surgically. CONCLUSIONS. Breath-hold contrast-enhanced 3D-MRA is a valuable technique for assessing visceral abdominal arteries and veins.

[Combined use of MRI and MR cholangiopancreatography and contrast enhanced dual phase 3-D MR angiography in diagnosis of pancreatic tumors: initial clinical results]. / Kombinierter Einsatz von MRT, MRCP und kontrastverstärkter 2-Phasen 3D-MRA in der Diagnostik von Pankreastumoren: Erste klinische Ergebnisse.

PURPOSE: To evaluate the accuracy of a non-invasive "all-in-one" staging MR method in patients with pancreatic tumors. MATERIAL AND METHODS: 46 patients were prospectively evaluated by a combined MR imaging protocol including breath-hold T1- and T2-weighted pulse sequence, MRCP using a breath-hold 2D-RARE sequence, and breath-hold gadolinium-enhanced dual-phase 3D-MR angiography. RESULTS: All pancreatic tumors were detected by the combination of cross-sectional imaging and MRCP. In spite of the use of MRCP, definitive differentiation between pancreatic carcinoma and chronic pancreatitis was not possible in 3 (6.5%) out of 46 cases. High quality 3D-MR angiograms were obtained in 43 (93.5%) cases. In 6 (13%) patients 3D-MRA showed an aberrant right hepatic artery. The overall accuracy of MRI in assessing extrapancreatic tumor spread, lymph node metastases, liver metastases, and vascular involvement was 95.7%, 80.4%, 93.5%, and 89.1%, respectively. CONCLUSION: Due to its high accuracy, the "all-in-one" MR protocol may become the most important modality after clinical examination and ultrasound in the diagnostic work-up for most patients with suspicion of pancreatic tumors.

[1H-MR spectroscopy in anorexia nervosa: reversible cerebral metabolic changes]. / 1H-MR-Spektroskopie bei Anorexia nervosa: reversible zerebrale Metabolitenänderungen.

PURPOSE: By using localized 1H-MR spectroscopy in the brain of patients with anorexia nervosa we wanted to verify our preliminary results and to look for a reversibility of the metabolic changes under therapy. METHODS: In 22 patients and 17 healthy volunteers (11 follow-up examinations) single voxel 1H-MR spectroscopy (TE = 50 ms, TM = 30 ms, TR = 1500 ms, voxel (2 cm)3, acq.: 256) was used in two different localizations (thalamus and parieto-occipital region). The first examination of the patients was performed before therapy, the follow-up examination at the end of therapy. RESULTS: In both regions of the brain we found a statistically significant elevation of the Cho/Cr-ratio in comparison to normal controls. The follow-up examinations revealed reversibility of the metabolic changes under successful therapy. CONCLUSIONS: 1H-MR spectroscopy reveals metabolic changes in the brain of patients with anorexia nervosa, which are reversible under successful therapy. These metabolic changes can be conclusively explained using a biochemical model.

[1H-MR spectroscopy in anorexia nervosa: the characteristic differences between patients and healthy subjects]. / 1H-MR-Spektroskopie bei Anorexia nervosa: charakteristische Unterschiede zwischen Patienten und gesunden Probanden.

PURPOSE: The neurophysiological and neuromorphological changes in patients with anorexia nervosa (AN) are well-known but the reason of both is still unknown. We have evaluated the usefulness of hydrogen (H1) magnetic resonance spectroscopy in anorexia nervosa. METHOD: We investigated 15 patients with clinically diagnosed AN (ICD F50.0) and 17 controls without eating disorders. The body mass index (BMI) was 15.8 and 21, respectively. The spectroscopy was recorded on two voxels in the parieto-occipital white matter or in the thalamus with a water-suppressed STEAM-sequence. The metabolites were recorded with respect to phosphocreatine (PCr). RESULTS: The ratio of NAA/PCr in both voxels were not significantly different when comparing patients vs. controls. Patients showed significantly higher ratios of choline-containing components (Cho) or, respectively Cho/PCr and NAA/PCr in the white matter. Distinct, but not significant differences were detected both for m-Ino and m-Ino/PCr in the parieto-occipital region and for the Cho- and m-Ino contained ratios in the thalamus. CONCLUSION: AN is not associated with neuronal damage. The ratio of Cho/PCr and NAA/Cho may reflect the disturbance of membrane-turnover. It is possible that the increase of membrane catabolism leads to a hyperosmolar state. The change of m-Ino/PCr ratio may reflect the regulation of osmolarity.

Proton magnetic resonance spectroscopy in acute, juvenile anorexia nervosa.

Anorexia nervosa is usually associated with a shrinkage of the brain that is at least partially reversible with weight gain. The pathogenesis of this brain abnormality is unclear. The purpose of this study was to investigate potential alterations in localized proton magnetic resonance (1H MR) spectra of anorectic patients immediately after an interval of excessive weight loss. Twelve patients and seventeen control subjects were examined. Water suppressed 1H MR spectra were recorded from two voxels placed in the thalamus and in the parieto-occipital white matter. The spectra of ten patients could be evaluated. Comparing patients and control subjects, significantly higher signal intensity ratios of choline containing compounds (Cho) relative to total creatine (Cr) as well as significantly lower ratios of N-acetyl-aspartate (NAA) relative to Cho were found in the white matter region. We hypothesize that these results indicate an abnormal starvation, associated membrane turnover, which predominantly takes place in the white matter. No evidence for neuronal degeneration was found in the thalamus or in the white matter region.