Variation correction algorithm: Analysis of phase suppression and thermal profile fidelity for proton resonance frequency magnetic resonance thermometry at 0.2 T

Barkauskas, Kestutis J.; Lewin, Jonathan S.; Duerk, Jeffrey L.

doi:10.1002/jmri.10239

Cited by 11 publications

(8 citation statements)

References 42 publications

(45 reference statements)

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“…Instances of such endeavors are preacquisition K-space correction and post-acquisition linear regression. 44 These methods suppress the misalignment of the echo in the K-space, which according to Grimault et al 43 contributes significantly to time-dependent background phase variations.…”

Section: Discussion 41 Calibrations and Observations Of Phase Driftmentioning

confidence: 99%

Assessment of thermal effects of interstitial laser phototherapy on mammary tumors using proton resonance frequency method

Figueroa

et al. 2011

J. Biomed. Opt.

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Abstract. Laser immunotherapy (LIT) uses a synergistic approach to treat cancer systemically through local laser irradiation and immunological stimulation. Currently, LIT utilizes dye-assisted noninvasive laser irradiation to achieve selective photothermal interaction. However, LIT faces difficulties treating deeper tumors or tumors with heavily pigmented overlying skin. To circumvent these barriers, we use interstitial laser irradiation to induce the desired photothermal effects. The purpose of this study is to analyze the thermal effects of interstitial irradiation using proton resonance frequency (PRF). An 805-nm near-infrared laser with an interstitial cylindrical diffuser was used to treat rat mammary tumors. Different power settings (1.0, 1.25, and 1.5 W) were applied with an irradiation duration of 10 min. The temperature distributions of the treated tumors were measured by a 7 T magnetic resonance imager using PRF. We found that temperature distributions in tissue depended on both laser power and time settings, and that variance in tissue composition has a major influence in temperature elevation. The temperature elevations measured during interstitial laser irradiation by PRF and thermocouple were consistent, with some variations due to tissue composition and the positioning of the thermocouple's needle probes. Our results indicated that, for a tissue irradiation of 10 min, the elevation of rat tumor temperature ranged from 8 to 11• C for 1 W and 8 to 15• C for 1.5 W. This is the first time a 7 T magnetic resonance imager has been used to monitor interstitial laser irradiation via PRF. Our work provides a basic understanding of the photothermal interaction needed to control the thermal damage inside a tumor using interstitial laser treatment. Our work may lead to an optimal protocol for future cancer treatment using interstitial phototherapy in conjunction with immunotherapy. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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Section: Discussion 41 Calibrations and Observations Of Phase Driftmentioning

confidence: 99%

Assessment of thermal effects of interstitial laser phototherapy on mammary tumors using proton resonance frequency method

Figueroa

et al. 2011

J. Biomed. Opt.

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“…If the temperature of the imaged subject is not varying, the subject is stationary, a single transmit/receive (T/R) coil is used for acquisition, and if T 2 effects are ignored, then the effect of static field inhomogeneity (ΔB 0 ) on the reconstructed image intensity, I, is given by I (r, TE) = ∥ M ⊥ (r)∥ ⋅ e −iγΔB 0 (r,t)TE +φ 0 (1) where |M ⊥ | is the magnitude of the transverse magnetic field; r is a spatial position vector; γ is the gyromagnetic ratio; TE is the echo time; ΔB 0 is the difference between the local field and the z-component of the main magnetic field B 0 that satisfies the Larmor equation; and φ 0 is the initial (constant) phase. Note that in these experiments any field inhomogeneity primarily affects the phase of the image, whereas in echo-planar sequences [6] it additionally results in image distortion and deformation.…”

Section: Theory Measuring the Magnetic Fieldmentioning

confidence: 99%

“…Phase-based proton-resonance frequency (PRF) MR thermometry measurements are particularly susceptible to underlying field variations [1]. Field homogeneity and stability affect the signal-to-noise ratio (SNR) and resolution in MR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Monitoring and correcting spatio-temporal variations of the MR scanner’s static magnetic field

El-Sharkawy

Schär

Bottomley

et al. 2006

Magn Reson Mater Phy

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The homogeneity and stability of the static magnetic field are of paramount importance to the accuracy of MR procedures that are sensitive to phase errors and magnetic field inhomogeneity. It is shown that intense gradient utilization in clinical horizontal-bore superconducting MR scanners of three different vendors results in main magnetic fields that vary on a long time scale both spatially and temporally by amounts of order 0.8-2.5 ppm. The observed spatial changes have linear and quadratic variations that are strongest along the z direction. It is shown that the effect of such variations is of sufficient magnitude to completely obfuscate thermal phase shifts measured by proton-resonance frequency-shift MR thermometry and certainly affect accuracy. In addition, field variations cause signal loss and line-broadening in MR spectroscopy, as exemplified by a fourfold line-broadening of metabolites over the course of a 45 min human brain study. The field variations are consistent with resistive heating of the magnet structures. It is concluded that correction strategies are required to compensate for these spatial and temporal field drifts for phase-sensitive MR protocols. It is demonstrated that serial field mapping and phased difference imaging correction protocols can substantially compensate for the drift effects observed in the MR thermometry and spectroscopy experiments.

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“…During three and eight minutes (for testing the validity of the conclusions for different durations) of heating in the right and left muscles, respectively, single-slice (S/S) GRE images (parameters in Table 1) were acquired for 3.3 seconds after every 26.7 seconds of the RF power input. The first image of the series had no heating applied and served as the reference for PRF thermometry (18,19). In the subsequent cooling period without RF input, GRE images were obtained every five seconds for the first 24 frames, every 20 seconds for the next 18 frames, and then every 30 seconds for the last 16 or six frames (for three-and eight-minute ablation, respectively).…”

Section: Image Acquisitionmentioning

confidence: 99%

“…Obtaining a temperature distribution map from MR phase difference images requires accurate and consistent k-space alignment and phase correction (18,19). Also, the MR temperature map had to be corrected because of the thermocouple susceptibility artifact at the RF probe tip.…”

Section: Image Processingmentioning

confidence: 99%

Magnetic resonance imaging and model prediction for thermal ablation of tissue

Chen

Barkauskas

Nour

et al. 2007

Magnetic Resonance Imaging

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Purpose: To monitor and predict tissue temperature distributions and lesion boundaries during thermal ablation by combining MRI and thermal modeling methods. Materials and Methods:Radiofrequency (RF) ablation was conducted in the paraspinal muscles of rabbits with MRI monitoring. A gradient-recalled echo (GRE) sequence via a 1.5T MRI system provided tissue temperature distribution from the phase images and lesion progression from changes in magnitude images. Post-ablation GRE estimates of lesion size were compared with post-ablation T2-weighted turbo-spin-echo (TSE) images and hematoxylin and eosin (H&E)-stained histological slices. A three-dimensional (3D) thermal model was used to simulate and predict tissue temperature and lesion size dynamics. Results:The lesion area estimated from repeated GRE images remained constant during the post-heating period when the temperature of the lesion boundary was less than a critical temperature. The final lesion areas estimated from multi-slice (M/S) GRE, TSE, and histological slices were not statistically different. The model-simulated tissue temperature distribution and lesion area closely corresponded to the GRE-based MR measurements throughout the imaging experiment. Conclusion:For normal tissue in vivo, the dynamics of tissue temperature distribution and lesion size during RF thermal ablation can be 1) monitored with GRE phase and magnitude images, and 2) simulated for prediction with a thermal model.

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Variation correction algorithm: Analysis of phase suppression and thermal profile fidelity for proton resonance frequency magnetic resonance thermometry at 0.2 T

Cited by 11 publications

References 42 publications

Assessment of thermal effects of interstitial laser phototherapy on mammary tumors using proton resonance frequency method

Assessment of thermal effects of interstitial laser phototherapy on mammary tumors using proton resonance frequency method

Monitoring and correcting spatio-temporal variations of the MR scanner’s static magnetic field

Magnetic resonance imaging and model prediction for thermal ablation of tissue

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