Assessment of left ventricle magnetic resonance temperature stability in patients in the presence of arrhythmias

Abstract

Background Magnetic resonance (MR) thermometry allows visualization of lesion formation in real‐time during cardiac radiofrequency (RF) ablation. The present study was performed to evaluate the precision of MR thermometry without RF heating in patients exhibiting cardiac arrhythmia in a clinical setting. The evaluation relied on quantification of changes in temperature measurements caused by noise and physiological motion. Methods Fourteen patients referred for cardiovascular magnetic resonance imaging underwent an extra sequence to test the temperature mapping stability during free‐breathing acquisition. Phase images were acquired using a multi‐slice, cardiac‐triggered, single‐shot echo planar imaging sequence. Temperature maps were calculated and displayed in real‐time while the electrocardiogram (ECG) was recorded. The precision of temperature measurement was assessed by measuring the temporal standard deviation and temporal mean of consecutive temperature maps over a period of three minutes. The cardiac cycle was analyzed from ECG recordings to quantify the impact of arrhythmia events on the precision of temperature measurement. Finally, two retrospective strategies were tested to remove acquisition dynamics related either to arrhythmia events or sudden breathing motion. Results ECG synchronization allowed categorization of inter‐beat intervals (RR) into distinct beat morphologies. Five patients were in stable sinus rhythm, while nine patients showed irregular RR intervals due to ectopic beats. An average temporal standard deviation of temperature of 1.6°C was observed in patients under sinus rhythm with a frame rate corresponding to the heart rate of the patient. The temporal standard deviation rose to 2.5°C in patients with arrhythmia. The retrospective rejection strategies increased the temperature precision measurement while maintaining a sufficient frame rate. Conclusions Our results indicated that real‐time cardiac MR thermometry shows good precision in patients under clinical conditions, even in the presence of arrhythmia. By providing real‐time visualization of temperature distribution within the myocardium during RF delivery, MR thermometry could prevent insufficient or excessive heating and thus improve safety and efficacy.

Real-time automatic temperature regulation during in vivo MRI-guided laser-induced thermotherapy (MR-LITT)

“…However, in the case of subject motion during the acquisition, artifacts on thermometry may occur and thus alter the quality of the regulation algorithm which results in an important energy delivery by the generator. A similar real-time thermometry pipeline was previously evaluated on the heart during catheterbased radiofrequency ablation and showed a temperature standard deviation below 2 °C on most of the pixels covering the myocardium 40 . Additional control steps can also be included in the real-time pipeline to limit the maximal allowed delivered power to reduce the risks of creating susceptibility artifacts.…”

Continuous cardiac thermometry via simultaneous catheter tracking and undersampled radial golden angle acquisition for radiofrequency ablation monitoring

“…Robustness of the phase subtraction to the variations in RR intervals between beats is a second potential issue needing to be evaluated before clinical application. In such cases, classification of beats based on RR interval 34 , 52 or QRS morphology 53 could also be envisioned to sort the projection during the library creation. The fast k-space algorithm 46 could alleviate this limitation by providing a more robust physiological phase compensation toward outliers.…”

Proton Resonance Frequency Shift Thermometry: A Review of Modern Clinical Practices

“…While cryoablation and microwave ablation are MR‐compatible, they are not compatible with PRF thermometry, as their operating temperatures (below –40 °C and over 100 °C, respectively) are outside the region of linearity of the chemical shift coefficient α (which is –15 °C to 100 °C). Radiofrequency ablation requires a wide‐bore scanner for imaging and the electrodes used for treatment can produce imaging artifacts, which make it unsuitable for PRF thermometry, although work is ongoing to improve this 39 . Consequently, this review details the latest clinical advances in MR‐guided ultrasound and laser ablation.…”

“…Radiofrequency ablation requires a wide-bore scanner for imaging and the electrodes used for treatment can produce imaging artifacts, which make it unsuitable for PRF thermometry, although work is ongoing to improve this. 39 Consequently, this review details the latest clinical advances in MR-guided ultrasound and laser ablation.…”