A Method to Estimate the Hydraulic Conductivity of the Ground by TRT Analysis.

The knowledge of hydraulic properties of aquifers is important in many engineering applications. Careful design of ground-coupled heat exchangers requires that the hydraulic characteristics and thermal properties of the aquifer must be well understood. Knowledge of groundwater flow rate and aquifer thermal properties is the basis for proper design of such plants. Different methods have been developed in order to estimate hydraulic conductivity by evaluating the transport of various tracers (chemical, heat etc.); thermal response testing (TRT) is a specific type of heat tracer that allows including the hydraulic properties in an effective thermal conductivity value. Starting from these considerations, an expeditious, graphical method was proposed to estimate the hydraulic conductivity of the aquifer, using TRT data and plausible assumption. Suggested method, which is not yet verified or proven to be reliable, should be encouraging further studies and development in this direction.

The acoustic hood: a patient-independent device improving acoustic noise protection during neonatal magnetic resonance imaging.

BACKGROUND: Magnetic resonance imaging (MRI) is today the imaging modality of choice to investigate the neonatal brain. However, the acoustic noise during scanning is very loud, often exceeding 100 dBA. AIM: To reduce the acoustic noise during MRI for neonatal patients. If effective, this would create a safer environment and also result in fewer aborted examinations due to poor image quality from patient motion. METHODS: A passive acoustic noise protector, the acoustic hood, was built out of dampening material. Sound pressure measurements with and without the acoustic hood were performed using our clinical neonatal scan protocol, consisting of eight imaging sequences. The acoustic hood is placed over the newborn inside the MR scanner tunnel during the examination to absorb acoustic noise. RESULTS: The acoustic noise level was substantially reduced using the acoustic hood. Peak sound pressure was reduced 16.18-22.21 dBA depending on the pulse sequence. For the entire frequency spectra, reduction were between 4-13.59 dBA again varying with the pulse sequence. CONCLUSION: Acoustic noise can be reduced further than before by using the patient-independent acoustic hood in addition to other noise protection. We recommend the use of three passive hearing protections during neonatal MRI: (1) dental putty, (2) paediatric ear muffs, and (3) the acoustic hood.

MRI of the brain and thorax during extracorporeal membrane oxygenation: preliminary report from a pig model.

Early diagnosis of cerebral hypoxic ischemic complications during extracorporeal membrane oxygenation (ECMO) is important to guide further treatment. However, diagnostic methods available during ECMO are limited, especially in adults and older children. Magnetic resonance imaging (MRI) is a sensitive and noninvasive method for assessment of vessel patency and brain parenchymal changes, and for measurement of brain perfusion. The use of MRI during ECMO has, to our knowledge, never been reported. We report the first animal experiment with MRI examination during ECMO. After a preliminary test with the mobile ECMO system in the MRI environment, a healthy pig was put on venoarterial ECMO, transported to the MRI department, and examined with sequences for anatomy and function of the brain and thorax. The results showed that the ECMO system was not adversely affected by the magnetic field at a distance from the camera where positioning and examination of the animal was possible. High-quality anatomical and functional images of the brain, heart, and thoracic vessels were acquired. The results suggest that MRI may be used for early diagnosis of cranial complications in patients on ECMO. MRI may also provide a useful tool for further research on flow dynamics and brain perfusion during ECMO.

Proton magnetic resonance spectroscopy in neuroblastoma: current status, prospects and limitations.

Non-invasive biological information about residual neuroblastoma tumour tissue could allow treatment monitoring without the need for repeated biopsies. Magnetic resonance spectroscopy (MRS) can be performed with standard MR-scanners, providing specific biochemical information from selected tumour regions. By proton 1H-MRS, lipids, certain amino acids and lactate can be detected and their relative concentrations estimated in vivo. Using experimental models of neuroblastoma, we have described the potential of 1H-MRS for the prediction of tumour tissue viability and treatment response. Whereas viable neuroblastoma tissue is dominated by the choline 1H-MRS resonance, cell death as a consequence of spontaneous necrosis or successful treatment with chemotherapy, angiogenesis inhibitors, or NSAIDs is associated with decreased choline content. Therapy-induced neuroblastoma cell death is also associated with enhanced 1H-MRS resonances from mobile lipids and polyunsaturated fatty acids. The mobile lipid/choline ratio correlates significantly with cell death and based on the dynamics of this ratio tumour regression or continued growth (drug resistance) after chemotherapy can be predicted in vivo. The implications of these findings are discussed with focus on the potentials and limitations of introducing 1H-MRS for clinical assessment of treatment response in children with neuroblastoma. Biochemical monitoring of neuroblastoma with 1H-MRS could enable tailoring of individual therapy as well as provide early pharmacodynamic evaluation of novel therapeutic modalities.