MR temperature mapping of focused ultrasound surgery

Cline, H. E.; Hynynen, Kullervo; Hardy, Christopher J.; Watkins, Ronald D.; Schenck, John F.; Jólesz, Ferenc A.

doi:10.1002/mrm.1910310608

Cited by 253 publications

(142 citation statements)

References 23 publications

(35 reference statements)

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“…1a) to create a pulse that is short in duration compared to the time for thermal dissipation. The intensity distributions at the focus along the z-axis and in the orthogonal focal plane z ϭ 0 are given by (25):…”

Section: Theorymentioning

confidence: 99%

“…The various geomet-rical factors associated with the transducer are illustrated in Figure 1a and are given by the diameter 2a, radius R, depth h, and radial and axial distances r and z, respectively, from the focus to the point of interest. Following Cline et al (25), these focusing patterns can be approximated with elliptical Gaussian functions with radial and axial radii r o and z o , respectively, corresponding to about 60% of the maximum intensity, from which an exact analytic solution to Eq. [1] is obtained (25):…”

Section: Theorymentioning

confidence: 99%

“…Following Cline et al (25), these focusing patterns can be approximated with elliptical Gaussian functions with radial and axial radii r o and z o , respectively, corresponding to about 60% of the maximum intensity, from which an exact analytic solution to Eq. [1] is obtained (25):…”

Section: Theorymentioning

confidence: 99%

See 2 more Smart Citations

Tissue thermal conductivity by magnetic resonance thermometry and focused ultrasound heating

Cheng

Plewes

2002

Magnetic Resonance Imaging

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Purpose:To investigate the combined use of magnetic resonance (MR) temperature imaging and focused ultrasound (FUS) for the noninvasive determination of tissue thermal properties. Materials and Methods:Brief, spatial impulses of temperature elevation were created in tissue using a spherical, air-backed transducer operating at 1.68 MHz and measured using MR temperature imaging in a 1.5-Tesla clinical scanner. A novel technique based on thermal washout is applied in an analysis of the acquired MR temperature images to estimate tissue thermal conductivity and perfusion.Results: Numerical simulations and experiments in vitro and in vivo demonstrate that thermal conductivity can be measured to within 10% of the true value with MR thermometry at 1.5 Tesla. With the temperature precision available at 1.5 Tesla, however, robust perfusion estimation is feasible only in highly perfused organs or tumors. Conclusion:This study has developed a method for determining tissue thermal properties specific to the patient and organ at the site of interest, and allows repeated application. This capability is relevant in thermal therapy planning of tumor ablation using MR-guided FUS systems.

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Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

See 1 more Smart Citation

Tissue thermal conductivity by magnetic resonance thermometry and focused ultrasound heating

Cheng

Plewes

2002

Magnetic Resonance Imaging

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“…To avoid this problem, the amount of energy E deposited during one feedback cycle t F into the point r is defined by Eq. [8].…”

Section: Spatial Temperature Controlmentioning

confidence: 99%

Real‐time adaptive methods for treatment of mobile organs by MRI‐controlled high‐intensity focused ultrasound

Senneville

Mougenot

Moonen

2007

Magnetic Resonance in Med

176

165

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Focused ultrasound (US) is a unique and noninvasive technique for local deposition of thermal energy deep inside the body. MRI guidance offers the additional benefits of excellent target visualization and continuous temperature mapping. However, treating a moving target poses severe problems because 1) motionrelated thermometry artifacts must be corrected, 2) the US focal point must be relocated according to the target displacement. In this paper a complete MRI-compatible, high-intensity focused US (HIFU) system is described together with adaptive methods that allow continuous MR thermometry and therapeutic US with real-time tracking of a moving target, online motion correction of the thermometry maps, and regional temperature control based on the proportional, integral, and derivative method. The hardware is based on a 256-element phased-array transducer with rapid electronic displacement of the focal point. The exact location of the target during US firing is anticipated using automatic analysis of periodic motions.

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“…This holds true for the range of temperatures that would typically be encountered by a device left outside (-5 °C to 40 °C) although it should be noted that it is not possible to obtain a signal from water below freezing. This relationship is well understood and has led to the development of MR thermometry [19], [20], [21].…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of magnetic resonance probes for use as embedded sensors in constructed wetlands

Hughes‐Riley

Dye

Anderez

et al. 2016

Sensors and Actuators A: Physical

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Constructed wetlands are now accepted as an environmentally friendly means of wastewater treatment however, their effectiveness can be limited by excessive clogging of the pores within the gravel matrix, making this an important parameter to monitor. It has previously been shown that the clog state can be characterised using magnetic resonance (MR) relaxation parameters with permanent magnet based sensors. One challenge with taking MR measurements over a time scale on the order of years is that seasonal temperature fluctuations will alter both the way that the sensor operates as well as the relaxation times recorded. Without an understanding of how the sensor will behave under different temperature conditions, meaningful information about the clog state cannot be successfully extracted from a wetland. This work reports the effect of temperature on a permanent magnet based MR sensor to determine if the received signal intensity is significantly compromised as a result of large temperature changes, and whether meaningful relaxation data can be extracted over the temperature range of interest. To do this, the central magnetic field of the sensor was monitored as a function of temperature, showing an expected linear relationship. Signal intensity was measured over a range of temperatures (5 °C to 44 °C) for which deterioration at high and low temperatures compared to room temperature was observed. The sensor was still operable at the extremes of this range and the reason for the signal loss has been studied and explained. Spin-lattice relaxation time measurements using the sensor at different temperatures have also been taken on a water sample and seem to agree with literature values. Further to this, measurements have been taken in an operational wetland over the course of 203 days and have shown a linear dependence with temperature as would be expected. This work concluded that the sensor can perform the task of measuring the spin-lattice relaxation time over the required temperature range making it suitable for long-term application in constructed wetlands.

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MR temperature mapping of focused ultrasound surgery

Cited by 253 publications

References 23 publications

Tissue thermal conductivity by magnetic resonance thermometry and focused ultrasound heating

Tissue thermal conductivity by magnetic resonance thermometry and focused ultrasound heating

Real‐time adaptive methods for treatment of mobile organs by MRI‐controlled high‐intensity focused ultrasound

Temperature dependence of magnetic resonance probes for use as embedded sensors in constructed wetlands

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