Obtaining local SAR and blood perfusion data from temperature measurements: steady state and transient techniques compared

Roemer, R. B.; Fletcher, Alison; Cetas, Thomas C.

doi:10.1016/0360-3016(85)90343-8

Cited by 98 publications

(37 citation statements)

References 14 publications

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“…For the latter, the local SAR can be derived from temperature gradients in temperature probes [11], which, however, requires a very cumbersome insertion of catheters into the tissue of interest. On the other hand, for MRI applications the averaged wholebody SAR (SAR-wb) can be estimated non-invasively using special resonant circuit techniques [12].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation and histopathological identification of acute thermal damage in skeletal porcine muscle in relation to whole-body SAR, maximum temperature, and CEM43 °C due to RF irradiation in an MR body coil of birdcage type at 123 MHz

Nadobny

Klopfleisch

Brinker

et al. 2015

International Journal of Hyperthermia

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Section: Introductionmentioning

confidence: 99%

Experimental investigation and histopathological identification of acute thermal damage in skeletal porcine muscle in relation to whole-body SAR, maximum temperature, and CEM43 °C due to RF irradiation in an MR body coil of birdcage type at 123 MHz

Nadobny

Klopfleisch

Brinker

et al. 2015

International Journal of Hyperthermia

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“…Previous studies 20 have shown that the specific absorption rate (SAR) can be estimated by measuring the rate of temperature increase immediately after the ultrasound power is turned on, when the conduction and perfusion losses are small compared to the absorbed power losses. The rate of temperature increase at the first sonication of each subject was used to calculate the experimental skull efficiency.…”

Section: A Experimental Skull Efficiencymentioning

confidence: 99%

Predicting variation in subject thermal response during transcranial magnetic resonance guided focused ultrasound surgery: Comparison in seventeen subject datasets

et al. 2016

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Purpose: In transcranial magnetic resonance-guided focused ultrasound (tcMRgFUS) treatments, the acoustic and spatial heterogeneity of the skull cause reflection, absorption, and scattering of the acoustic beams. These effects depend on skull-specific parameters and can lead to patient-specific thermal responses to the same transducer power. In this work, the authors develop a simulation tool to help predict these different experimental responses using 3D heterogeneous tissue models based on the subject CT images. The authors then validate and compare the predicted skull efficiencies to an experimental metric based on the subject thermal responses during tcMRgFUS treatments in a dataset of seventeen human subjects. Methods: Seventeen human head CT scans were used to create tissue acoustic models, simulating the effects of reflection, absorption, and scattering of the acoustic beam as it propagates through a heterogeneous skull. The hybrid angular spectrum technique was used to model the acoustic beam propagation of the InSightec ExAblate 4000 head transducer for each subject, yielding maps of the specific absorption rate (SAR). The simulation assumed the transducer was geometrically focused to the thalamus of each subject, and the focal SAR at the target was used as a measure of the simulated skull efficiency. Experimental skull efficiency for each subject was calculated using the thermal temperature maps from the tcMRgFUS treatments. Axial temperature images (with no artifacts) were reconstructed with a single baseline, corrected using a referenceless algorithm. The experimental skull efficiency was calculated by dividing the reconstructed temperature rise 8.8 s after sonication by the applied acoustic power. Results: The simulated skull efficiency using individual-specific heterogeneous models predicts well (R 2 = 0.84) the experimental energy efficiency. Conclusions: This paper presents a simulation model to predict the variation in thermal responses measured in clinical ctMRGFYS treatments while being computationally feasible. C 2016 American Association of Physicists in Medicine. [http://dx

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“…fat , k tumour , k muscle and k fat . In the first optimisation an applicator efficiency of 40% was used, which was obtained for the HYPERcollar applicator by Adibzadeh et al [17] using the power-off method [18,19]. Since the patients included in our study were all treated with the HYPERcollar applicator we used the result of this optimisation to determine the feasibility of 3D dosimetry.…”

Section: Optimisation Procedures Of Thermal Parameter Valuesmentioning

confidence: 99%

“…Other approaches that investigated accuracy of 3D temperature dosimetry were based on the power-off method [18,19] or MRTI. The power-off technique allows SAR or the effective perfusion to be determined, i.e.…”

Section: D Temperature Simulation Accuracymentioning

confidence: 99%

Accurate 3D temperature dosimetry during hyperthermia therapy by combining invasive measurements and patient-specific simulations

Verhaart

Verduijn

Fortunati

et al. 2015

International Journal of Hyperthermia

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Obtaining local SAR and blood perfusion data from temperature measurements: steady state and transient techniques compared

Cited by 98 publications

References 14 publications

Experimental investigation and histopathological identification of acute thermal damage in skeletal porcine muscle in relation to whole-body SAR, maximum temperature, and CEM43 °C due to RF irradiation in an MR body coil of birdcage type at 123 MHz

Experimental investigation and histopathological identification of acute thermal damage in skeletal porcine muscle in relation to whole-body SAR, maximum temperature, and CEM43 °C due to RF irradiation in an MR body coil of birdcage type at 123 MHz

Predicting variation in subject thermal response during transcranial magnetic resonance guided focused ultrasound surgery: Comparison in seventeen subject datasets

Accurate 3D temperature dosimetry during hyperthermia therapy by combining invasive measurements and patient-specific simulations

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