Real‐time MR thermometry for monitoring HIFU ablations of the liver

Holbrook, Andrew B.; Santos, Juan M.; Kaye, Elena; Rieke, Viola; Pauly, Kim Butts

doi:10.1002/mrm.22206

Cited by 85 publications

(63 citation statements)

References 27 publications

(26 reference statements)

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“…Referenceless thermometry has been validated in a retrospective study in 33 patients undergoing uterine fibroid ablation 17 and has been used for real-time monitoring of focused ultrasound ablation of the liver during free breathing. 18 Recently, we introduced a new approach to the referenceless method that uses reweighted ᐉ 1 regression, 19 a form of robust regression, to obtain background phase coefficients. That method does not require prior knowledge of the heating region in order to obtain an accurate temperature map and does not require tracking the heated area during motion.…”

Section: Introductionmentioning

confidence: 99%

Hybrid referenceless and multibaseline subtraction MR thermometry for monitoring thermal therapies in moving organs

et al. 2010

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Purpose: Magnetic resonance thermometry using the proton resonance frequency ͑PRF͒ shift is a promising technique for guiding thermal ablation. For temperature monitoring in moving organs, such as the liver and the heart, problems with motion must be addressed. Multi-baseline subtraction techniques have been proposed, which use a library of baseline images covering the respiratory and cardiac cycle. However, main field shifts due to lung and diaphragm motion can cause large inaccuracies in multi-baseline subtraction. Referenceless thermometry methods based on polynomial phase regression are immune to motion and susceptibility shifts. While referenceless methods can accurately estimate temperature within the organ, in general, the background phase at organ/ tissue interfaces requires large polynomial orders to fit, leading to increased danger that the heated region itself will be fitted by the polynomial and thermal dose will be underestimated. In this paper, a hybrid method for PRF thermometry in moving organs is presented that combines the strengths of referenceless and multi-baseline thermometry. Methods: The hybrid image model assumes that three sources contribute to image phase during thermal treatment: Background anatomical phase, spatially smooth phase deviations, and focal, heat-induced phase shifts. The new model and temperature estimation algorithm were tested in the heart and liver of normal volunteers, in a moving phantom HIFU heating experiment, and in numerical simulations of thermal ablation. The results were compared to multi-baseline and referenceless methods alone. Results: The hybrid method allows for in vivo temperature estimation in the liver and the heart with lower temperature uncertainty compared to multi-baseline and referenceless methods. The moving phantom HIFU experiment showed that the method accurately estimates temperature during motion in the presence of smooth main field shifts. Numerical simulations illustrated the method's sensitivity to algorithm parameters and hot spot features. Conclusions: This new hybrid method for MR thermometry in moving organs combines the strengths of both multi-baseline subtraction and referenceless thermometry and overcomes their fundamental weaknesses.

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Section: Introductionmentioning

confidence: 99%

Hybrid referenceless and multibaseline subtraction MR thermometry for monitoring thermal therapies in moving organs

et al. 2010

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“…During ablation procedures, imaging is used to locate targeted lesions (11-13), monitor tissue ablation (14)(15)(16), and evaluate treatment effectiveness (17)(18)(19). Because of its ease of use and broad availability, ultrasonography (US) is most routinely used during ablation procedures in clinical settings (20)(21)(22).…”

Section: Experimental Overviewmentioning

confidence: 99%

Multimodality Imaging to Assess Immediate Response to Irreversible Electroporation in a Rat Liver Tumor Model

Zhang¹,

White²,

Nicolai³

et al. 2014

Radiology

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Purpose:To compare changes on ultrasonographic (US), computed tomographic (CT), and magnetic resonance (MR) images after irreversible electroporation (IRE) ablation of liver and tumor tissues in a rodent hepatoma model. Materials and Methods:Studies received approval from the institutional animal care and use committee. Forty-eight rats were used, and N1-S1 tumors were implanted in 24. Rats were divided into groups and allocated for studies with each modality. Imaging was performed in normal liver tissues and tumors before and after IRE. MR imaging was performed in one group before and after IRE after hepatic vessel ligation. US images were graded to determine echogenicity changes, CT attenuation was measured (in Hounsfield units), and MR imaging signal-to-noise ratio (SNR) was measured before and after IRE. Student t test was used to compare attenuation and SNR measurements before and after IRE (P , .05 indicated a significant difference). Results:IRE ablation produced greater alterations to echogenicity in normal tissues than in tumors. Attenuation in ablated liver tissues was reduced compared with that in control tissues (P , .001), while small attenuation differences between ablated (42.11 HU 6 2.11) and control (45.14 HU 6 2.64) tumors trended toward significance (P = .052). SNR in ablated normal tissues was significantly altered after IRE (T1-weighted images: pre-IRE, 145.95 6 24.32; post-IRE, 97.80 6 18.03; P = .004; T2-weighted images, pre-IRE, 47.37 6 18.31; post-IRE, 90.88 6 37.15; P = .023). In tumors, SNR differences before and after IRE were not significant. No post-IRE signal changes were observed after hepatic vessel ligation. Conclusion:IRE induces rapid changes on gray-scale US, unenhanced CT, and MR images. These changes are readily visible and may assist a performing physician to delineate ablation zones from the unablated surrounding parenchyma.q RSNA, 2014

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“…RECENT IMPROVEMENTS IN high-intensity focused ultrasound (HIFU) technology have revealed its potential as a noninvasive surgical tool in many clinical settings (1)(2)(3)(4)(5)(6)(7). Of the many tools available for monitoring HIFU treatment, magnetic resonance imaging (MRI) has proven to be a practical tool for this purpose.…”

mentioning

confidence: 99%

Proton resonance frequency shift‐weighted imaging for monitoring MR‐guided high‐intensity focused ultrasound transmissions

Chen

Huang

Peng

et al. 2011

Magnetic Resonance Imaging

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Purpose: To combine temperature-related information of phase images and magnitude images acquired from an MR spoiled gradient echo sequence using a postprocessing method referred to as PRF-shift-weighted imaging (PRFSWI). Materials and Methods:Phase images are capable of detecting shifts in proton resonance frequency (PRF) caused by local changes in temperature. Magnitude images provide anatomical information for treatment planning and positioning as well as temperature-related contrast. We used PRFSWI to produce a phase-mask and performed multiplication on the magnitude image to increase temperature-related contrast.Results: Through MRI-guided focused ultrasound (MRIg-FUS) experiments (both ex vivo and in vivo), we determined that PRFSWI is capable of enhancing the contrast of a heated area even in the initial stages of transmitting high-intensity focused ultrasound energy. Conclusion:The PRFSWI images are sensitive to changes in temperature and display the heated spot directly in the magnitude images. Although the images do not provide quantitative data related to temperature, this method could be used as a complement to the phase temperature mapping method in the real-time monitoring of MRIgFUS experiments.

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Real‐time MR thermometry for monitoring HIFU ablations of the liver

Cited by 85 publications

References 27 publications

Hybrid referenceless and multibaseline subtraction MR thermometry for monitoring thermal therapies in moving organs

Hybrid referenceless and multibaseline subtraction MR thermometry for monitoring thermal therapies in moving organs

Multimodality Imaging to Assess Immediate Response to Irreversible Electroporation in a Rat Liver Tumor Model

Proton resonance frequency shift‐weighted imaging for monitoring MR‐guided high‐intensity focused ultrasound transmissions

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