Absolute Temperature

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Navin Bansal - One of the best experts on this subject based on the ideXlab platform.

  • Absolute Temperature mr imaging with thulium 1 4 7 10 tetraazacyclododecane 1 4 7 10 tetramethyl 1 4 7 10 tetraacetic acid tmdotma
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Judy R James, Yong Gao, Michael A Miller, Andriy M Babsky, Navin Bansal
    Abstract:

    MR thermometry based on the water (1)H signal provides high temporal and spatial resolution, but it has low Temperature sensitivity (approximately 0.01 ppm/degrees C) and requires monitoring of another weaker signal for Absolute Temperature measurements. The use of the paramagnetic lanthanide complex, thulium 1,4,7,10- tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraacetate (TmDOTMA(-)), which is approximately 60 times more sensitive to Temperature than the water (1)H signal, is advanced to image Absolute Temperatures in vivo using water signal as a reference. The Temperature imaging technique was developed using gradient echo and asymmetric spin echo imaging sequences on 9.4 Tesla (T) horizontal and vertical MR scanners. A comparison of regional Temperatures measured with TmDOTMA(-) and fiber-optic probes showed that the accuracy of imaging Temperature is <0.3 degrees C. The Temperature imaging technique was found to be insensitive to inhomogeneities in the main magnetic field. The feasibility of imaging Temperature of intact rats at approximately 1.4 mmol/kg dose with approximately 1-mm spatial resolution in only 3 min is demonstrated. TmDOTMA(-) should prove useful for imaging Absolute Temperatures in deep-seated organs in numerous biomedical applications.

Lambertus W Bartels - One of the best experts on this subject based on the ideXlab platform.

  • multi gradient echo mr thermometry for monitoring of the near field area during mr guided high intensity focused ultrasound heating
    Physics in Medicine and Biology, 2015
    Co-Authors: Mie K Lam, Martijn De Greef, Job G Bouwman, Chrit T W Moonen, Max A Viergever, Lambertus W Bartels
    Abstract:

    The multi-gradient echo MR thermometry (MGE MRT) method is proposed to use at the interface of the muscle and fat layers found in the abdominal wall, to monitor MR-HIFU heating. As MGE MRT uses fat as a reference, it is field-drift corrected. Relative Temperature maps were reconstructed by subtracting Absolute Temperature maps. Because the Absolute Temperature maps are reconstructed of individual scans, MGE MRT provides the flexibility of interleaved mapping of Temperature changes between two arbitrary time points. The method's performance was assessed in an ex vivo water bath experiment. An ex vivo HIFU experiment was performed to show the method's ability to monitor heating of consecutive HIFU sonications and to estimate cooling time constants, in the presence of field drift. The interleaved use between scans of a clinical protocol was demonstrated in vivo in a patient during a clinical uterine fibroid treatment. The relative Temperature measurements were accurate (mean Absolute error 0.3 °C) and provided excellent visualization of the heating of consecutive HIFU sonications. Maps were reconstructed of estimated cooling time constants and mean ROI values could be well explained by the applied heating pattern. Heating upon HIFU sonication and subsequent cooling could be observed in the in vivo demonstration.

  • Absolute mr thermometry using time domain analysis of multi gradient echo magnitude images
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Sara M Sprinkhuizen, Chris J G Bakker, Lambertus W Bartels
    Abstract:

    MRI allows for Absolute Temperature measurements in substances containing two spectral resonances of which the frequency difference Delta f(T) is related to Absolute Temperature. This frequency difference can be extracted from spectroscopic data. An image-based MR technique that allows for the acquisition of spectroscopic data at high temporal and spatial resolution is the multi-gradient-echo sequence. In this work, the application of the multi-gradient-echo sequence for MR thermometry purposes was further developed. We investigated the possibility of postprocessing the multi-gradient-echo data into Absolute Temperature maps, using time-domain analysis of the magnitude of the multi-gradient-echo signals. In this approach, instead of an indirect computation of Delta f(T) from separately found frequencies, Delta f(T) is a direct output parameter. In vitro experiments were performed to provide proof of concept for retrieving Absolute Temperature maps from the time-domain analysis of multi-gradient-echo magnitude images. It is shown that this technique is insensitive to both field drift and local field disturbances. Furthermore, ex vivo bone marrow experiments were performed, using the fat resonance as a reference for Absolute Temperature mapping. It is shown that the postprocessing based on the magnitude signal in the time domain allows for the determination of Delta f(T) in bone marrow.

Judy R James - One of the best experts on this subject based on the ideXlab platform.

  • Absolute Temperature mr imaging with thulium 1 4 7 10 tetraazacyclododecane 1 4 7 10 tetramethyl 1 4 7 10 tetraacetic acid tmdotma
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Judy R James, Yong Gao, Michael A Miller, Andriy M Babsky, Navin Bansal
    Abstract:

    MR thermometry based on the water (1)H signal provides high temporal and spatial resolution, but it has low Temperature sensitivity (approximately 0.01 ppm/degrees C) and requires monitoring of another weaker signal for Absolute Temperature measurements. The use of the paramagnetic lanthanide complex, thulium 1,4,7,10- tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraacetate (TmDOTMA(-)), which is approximately 60 times more sensitive to Temperature than the water (1)H signal, is advanced to image Absolute Temperatures in vivo using water signal as a reference. The Temperature imaging technique was developed using gradient echo and asymmetric spin echo imaging sequences on 9.4 Tesla (T) horizontal and vertical MR scanners. A comparison of regional Temperatures measured with TmDOTMA(-) and fiber-optic probes showed that the accuracy of imaging Temperature is <0.3 degrees C. The Temperature imaging technique was found to be insensitive to inhomogeneities in the main magnetic field. The feasibility of imaging Temperature of intact rats at approximately 1.4 mmol/kg dose with approximately 1-mm spatial resolution in only 3 min is demonstrated. TmDOTMA(-) should prove useful for imaging Absolute Temperatures in deep-seated organs in numerous biomedical applications.

Bilal Ahmed Qureshi - One of the best experts on this subject based on the ideXlab platform.

  • heat exchanger inventory cost optimization for power cycles with one feedwater heater
    Energy Conversion and Management, 2014
    Co-Authors: Bilal Ahmed Qureshi, Mohamed A Antar
    Abstract:

    Cost optimization of heat exchanger inventory in power cycles with one open feedwater heater is undertaken. In this regard, thermoeconomic analysis for an endoreversible power cycle with an open feedwater heater is shown. The scenarios of constant heat rejection and addition rates, power as well as rate of heat transfer in the open feedwater heater are studied. All cost functions displayed minima with respect to the high-side Absolute Temperature ratio (θ1). In this case, the effect of the Carnot Temperature ratio (Φ1), Absolute Temperature ratio (ξ) and the phase-change Absolute Temperature ratio for the feedwater heater (Φ2) are qualitatively the same. Furthermore, the constant heat addition scenario resulted in the lowest value of the cost function. For variation of all cost functions, the smaller the value of the phase-change Absolute Temperature ratio for the feedwater heater (Φ2), lower the cost at the minima. As feedwater heater to hot end unit cost ratio decreases, the minimum total conductance required increases.

  • cost optimization of heat exchanger inventory for mechanical subcooling refrigeration cycles
    International Journal of Refrigeration-revue Internationale Du Froid, 2013
    Co-Authors: Bilal Ahmed Qureshi, Syed M Zubair
    Abstract:

    Abstract In this paper, thermoeconomic considerations are given to heat exchanger inventory allocation in vapor compression cycles with mechanical subcooling. Investigation is made with respect to constant work rate, heat rejection and cooling rates as well as heat transfer in the subcooler. It was found that no minima exist for any of the cost functions with respect to the Absolute Temperature ratio ( ξ ) and the average subcooling Absolute Temperature ratio ( θ 3 ). The derivatives for the integrated subcooling cycle can be generated from the derivatives of the dedicated subcooling cycle. It was concluded that the cost optimization of the integrated mechanical subcooling system is qualitatively the same as the dedicated subcooling system.

Sander J Tans - One of the best experts on this subject based on the ideXlab platform.

  • Temperature dependent resistivity of single wall carbon nanotubes
    EPL, 1998
    Co-Authors: C L Kane, E J Mele, R S Lee, John E Fischer, P Petit, Hongjie Dai, Andreas Thess, R E Smalley, Alwin Rogier Martijn Verschueren, Sander J Tans
    Abstract:

    Samples of single-wall carbon nanotubes containing tubes with an armchair wrapping have been produced and exhibit metallic behavior with an intrinsic resistivity which increases approximately linearly with Temperature over a wide Temperature range. Here we study the coupling of the conduction electrons to long-wavelength torsional shape fluctuations, or twistons. A one-dimensional theory of the scattering of electrons by twistons is presented which predicts an intrinsic resistivity proportional to the Absolute Temperature. Experimental measurements of the Temperature dependence of the resistivity are reported and compared with the predictions of the twiston theory.

  • Temperature dependent resistivity of single wall carbon nanotubes
    arXiv: Condensed Matter, 1997
    Co-Authors: C L Kane, E J Mele, R S Lee, John E Fischer, P Petit, Hongjie Dai, Andreas Thess, R E Smalley, Alwin Rogier Martijn Verschueren, Sander J Tans
    Abstract:

    Nonchiral single wall carbon nanotubes with an "armchair" wrapping are theoretically predicted to be conducting, and high purity samples consisting predominantly of these tubes exhibit metallic behavior with an intrinsic resistivity which increases approximately linearly with Temperature over a wide Temperature range. Here we study the coupling of the conduction electrons to long wavelength torsional shape fluctuations, or twistons. A one dimensional theory of the scattering of electrons by twistons is presented which predicts an intrinsic resistivity proportional to the Absolute Temperature. Experimental measurements of the Temperature dependence of the resistivity are reported and compared with the predictions of the twiston theory.