Magnetic susceptibility effects on the accuracy of MR temperature monitoring by the proton resonance frequency method

Boss, Andreas; Graf, Hansjörg; Müller‐Bierl, Bernd; Clasen, Stephan; Schmidt, Diethard; Pereira, Philippe L.; Schick, Fritz

doi:10.1002/jmri.20438

Cited by 31 publications

(25 citation statements)

References 18 publications

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“…A decreased SNR due to incomplete filtering and to possible residual organ displacements may occur and thereby increase the standard deviation of temperature estimation [21]. Therefore, additional image processing was performed off-line as follows [22]: first, in each pixel of a ROI located outside the heated region, the standard deviation of the MR temperature measurements was calculated before, during and after RF ablation; second, residual motion was corrected using an atlas of reference data (magnitude and corresponding phase images) for the different liver positions recorded before the heating phase; third, if the temperature standard deviation (outside the RF ablation zone) following the above-mentioned correction exceeded 10% of a predefined maximal value, the temperature image was removed from the TD calculation process.…”

Section: Post Processingmentioning

confidence: 99%

Real time monitoring of radiofrequency ablation based on MR thermometry and thermal dose in the pig liver in vivo

et al. 2007

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Real time monitoring of radiofrequency ablation based on MR thermometry and thermal dose in the pig liver in vivo Abstract To evaluate the feasibility and accuracy of MR thermometry based on the thermal dose (TD) concept for monitoring radiofrequency (RF) ablations, 13 RF ablations in pig livers were performed under continuous MR thermometry at 1.5 T with a filtered clinical RF device. Respiratory gated fast gradient echo images were acquired simultaneously to RF deposition for providing MR temperature maps with the proton resonant frequency technique. Residual motion, signal to noise ratio (SNR) and standard deviation (SD) of MR temperature images were quantitatively analyzed to detect and reject artifacted images in the time series. SD of temperature measurement remained under 2°C. Macroscopic analysis of liver ablations showed a white zone (Wz) surrounded by a red zone (Rz). A detailed histological analysis confirmed the ongoing nature of the coagulation necrosis in both Wz and Rz. Average differences (±SD) between macroscopic size measurements of Wz and Rz and TD predictions of ablation zones were 4.1 (±1.93) mm and −0.71 (±2.47) mm, respectively. Correlation values between TD and Wz and TD and Rz were 0.97 and 0.99, respectively. MR thermometry monitoring based on TD is an accurate method to delineate the size of the ablation zone during the RF procedure and provides a clinical endpoint.

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Section: Post Processingmentioning

confidence: 99%

Real time monitoring of radiofrequency ablation based on MR thermometry and thermal dose in the pig liver in vivo

et al. 2007

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“…Evaluation of temperature mapping has been mainly focused on the analysis of accuracy and precision (18,20,30). A high precision of temperature values was published for both EPI and GRE sequences (18).…”

Section: Discussionmentioning

confidence: 99%

“…Prior studies reported that any temperature above 52°C caused irreversible tissue damage (24,25). Sixty degrees C was chosen in order to compensate for eventual breathing-induced temperature misregistrations reported especially for the liver dome (26) and for errors induced by the use of metallic applicators (20). We used a binary classification test to evaluate the validity of the temperature maps (see Fig.…”

Section: Segmentation Of the Coagulation Zonementioning

confidence: 99%

“…In addition to active artifacts caused by the RF generator, which do not occur in this approach, other factors interfere with the temperature measurement: these are passive artifacts of the RF probes (20), intrascan motion, and interscan patient motion (7). With gradient echo imaging (GRE) and segmented echo planar imaging (EPI) sequences, two sequence types have been suggested to perform PRF-based temperature measurement (18).…”

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Prediction of cell necrosis with sequential temperature mapping after radiofrequency ablation

Rempp

Clasen

Boss

et al. 2009

Magnetic Resonance Imaging

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Purpose:To assess the feasibility of magnetic resonance (MR) thermometry after thermoablative therapy and to quantitatively evaluate the ability of two sequence types to predict cell necrosis. Methods:Twenty patients with hepatic tumors were treated by MR-guided radiofrequency ablation. For each 10 patients, postinterventionally performed gradient echo and segmented echo planar imaging sequences were used to calculate temperature maps based on the proton resonance frequency shift method. Contrast-enhanced images acquired 1 month after therapy were registered on the temperature maps and the necrotic, nonenhanced area was segmented and compared to the area with a displayed temperature above 60°C. Sensitivity and positive predictive value of the temperature map was calculated, using the follow-up imaging as the gold standard. Results:Temperature mapping reached acceptable image quality in 45/47 cases. Sensitivity, ie, the rate of correctly detected coagulated tissue was 0.82 Ϯ 0.08 for the gradient echo imaging (GRE) sequence and 0.81 Ϯ 0.14 for the echo planar imaging (EPI) sequence. Positive predictive value, ie, the rate of voxel in the temperature map over 60°C that actually developed necrosis, was 0.90 Ϯ 0.07 for the GRE sequence and 0.84 Ϯ 0.11 for the EPI sequence. Conclusion:Sequential MR temperature mapping allows for the prediction of the coagulation zone with an acceptable sensitivity and positive predictive value using EPI and GRE sequences. REAL-TIME TEMPERATURE MAPPING of magnetic resonance (MR)-guided minimally invasive radiofrequency (RF) ablation has been shown to be feasible both ex vivo (1) and in vivo (2-5), and has the potential of becoming the gold standard for therapy monitoring of thermoablative therapies. Different MR techniques have been proposed for temperature measurement (6 -10); the most frequently used is the proton resonance frequency shift (PRF) method (11-14), which is based on a temperature-dependent phase shift allowing for the measurement of temperature changes relative to a baseline image. With frequent repetitive measurements during thermoablative therapy, this approach allows a precise estimation of the lethal thermal dose (15) based on the Arrhenius model (16,17) and could be used to predict the size and position of the coagulation zone in animal studies (3,5). Furthermore, real-time temperature monitoring could allow for visualizing a vessel-related cooling effect and thus prevent a survival of cancer cells due to an undetected heat-sink effect.Due to technical and medical challenges linked to this approach, the majority of the literature up to now concerns preclinical questions. In case of RF ablation, the simultaneous use of an RF generator with frequencies between 300 and 500 kHz during imaging decreases image quality (6,18). To date, only noncommercial filters were used to overcome this problem (4,18) or generators with an adapted frequency were employed in animal studies (3,19). Therefore, we performed temperature measurement with a sequential approach: The sedated pat...

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“…The accuracy of the temperature measurements using MR thermometry is comparable to that of the invasive methods (20). However, conventional MR thermometry methods, such as PRFS, are sensitive to local magnetic susceptibility associated with tissue anatomy and interventional medical devices (21)(22)(23), large fat contents within the region of interest (ROI) (14), motion artifacts (5), and magnetic field drift (20). Alternative MR thermometry techniques have been developed over the last twenty years to exploit MR properties that afford high temperature sensitivity and measurement accuracy.…”

Section: Introductionmentioning

confidence: 99%

Image-guided thermal ablation with MR-based thermometry

Zhu

Sun

2017

Quant. Imaging Med. Surg.

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Thermal ablation techniques such as radiofrequency, microwave, high intensity focused ultrasound (HIFU) and laser have been used as minimally invasive strategies for the treatment of variety of cancers. MR thermometry methods are readily available for monitoring thermal distribution and deposition in real time, leading to decrease of incidents of normal tissue damage around targeted lesion. HIFU and laser-induced thermal therapy (LITT) are the two widely accepted tumor ablation techniques because of their compatibility with MR systems. MRI provides multiple temperature dependent parameters for thermal imaging, such as signal intensity, T1, T2, diffusion coefficient, magnetization transfer, proton resonance frequency shift (PRFS, including phase imaging and spectroscopy) as well as frequency shift of temperature sensitive contrast agents. Absolute temperature mapping techniques, including both spectroscopic imaging using metabolites as a reference and phase imaging using fat as a reference, are immune to susceptibility effects and are not dependent on phase differences. These techniques are intrinsically more reliable than relative temperature measurement by phase mapping methods. If the limitation of low temporal and spatial resolution could be overcome, these methods may be preferred for MR-guided thermal ablation systems.As of today, the most popular MR thermal imaging method applied in tumor thermal ablation surgery is, however, still PRFS based phase mapping technique, which only provides relative temperature change and is prone to motion artifacts.

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Magnetic susceptibility effects on the accuracy of MR temperature monitoring by the proton resonance frequency method

Cited by 31 publications

References 18 publications

Real time monitoring of radiofrequency ablation based on MR thermometry and thermal dose in the pig liver in vivo

Real time monitoring of radiofrequency ablation based on MR thermometry and thermal dose in the pig liver in vivo

Prediction of cell necrosis with sequential temperature mapping after radiofrequency ablation

Image-guided thermal ablation with MR-based thermometry

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