Dataset Information

Gradient-induced voltages on 12-lead ECGs during high duty-cycle MRI sequences and a method for their removal considering linear and concomitant gradient terms.

ABSTRACT: To restore 12-lead electrocardiographic (ECG) signal fidelity inside MRI by removing magnetic field gradient-induced voltages during high gradient duty cycle sequences.A theoretical equation was derived to provide first- and second-order electrical fields induced at individual ECG electrodes as a function of gradient fields. Experiments were performed at 3T on healthy volunteers using a customized acquisition system that captured the full amplitude and frequency response of ECGs, or a commercial recording system. The 19 equation coefficients were derived via linear regression of data from accelerated sequences and were used to compute induced voltages in real-time during full resolution sequences to remove ECG artifacts. Restored traces were evaluated relative to ones acquired without imaging.Measured induced voltages were 0.7 V peak-to-peak during balanced steady state free precession (bSSFP) with the heart at the isocenter. Applying the equation during gradient echo sequencing, three-dimensional fast spin echo, and multislice bSSFP imaging restored nonsaturated traces and second-order concomitant terms showed larger contributions in electrodes further from the magnet isocenter. Equation coefficients are evaluated with high repeatability (??=?0.996) and are dependent on subject, sequence, and slice orientation.Close agreement between theoretical and measured gradient-induced voltages allowed for real-time removal. Prospective estimation of sequence periods in which large induced voltages occur may allow hardware removal of these signals.

SUBMITTER: Zhang SH

PROVIDER: S-EPMC4689682 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Gradient-induced voltages on 12-lead ECGs during high duty-cycle MRI sequences and a method for their removal considering linear and concomitant gradient terms.

Zhang Shelley HuaLei SH Tse Zion Tsz Ho ZT Dumoulin Charles L CL Kwong Raymond Y RY Stevenson William G WG Watkins Ronald R Ward Jay J Wang Wei W Schmidt Ehud J EJ

Magnetic resonance in medicine 20150623 5

<h4>Purpose</h4>To restore 12-lead electrocardiographic (ECG) signal fidelity inside MRI by removing magnetic field gradient-induced voltages during high gradient duty cycle sequences.<h4>Theory and methods</h4>A theoretical equation was derived to provide first- and second-order electrical fields induced at individual ECG electrodes as a function of gradient fields. Experiments were performed at 3T on healthy volunteers using a customized acquisition system that captured the full amplitude and ...[more]

PMID: 26101951

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Project description:INTRODUCTION: We describe initial validation of a new system for digital to analog conversion (DAC) and reconstruction of 12-lead ECGs. The system utilizes an open and optimized software format with a commensurately optimized DAC hardware configuration to accurately reproduce, from digital files, the original analog electrocardiographic signals of previously instrumented patients. By doing so, the system also ultimately allows for transmission of data collected on one manufacturer's 12-lead ECG hardware/software into that of any other. MATERIALS AND METHODS: To initially validate the system, we compared original and post-DAC re-digitized 12-lead ECG data files (?5-minutes long) in two types of validation studies in 10 patients. The first type quantitatively compared the total waveform voltage differences between the original and re-digitized data while the second type qualitatively compared the automated electrocardiographic diagnostic statements generated by the original versus re-digitized data. RESULTS: The grand-averaged difference in root mean squared voltage between the original and re-digitized data was 20.8 µV per channel when re-digitization involved the same manufacturer's analog to digital converter (ADC) as the original digitization, and 28.4 µV per channel when it involved a different manufacturer's ADC. Automated diagnostic statements generated by the original versus reconstructed data did not differ when using the diagnostic algorithm from the same manufacturer on whose device the original data were collected, and differed only slightly for just 1 of 10 patients when using a third-party diagnostic algorithm throughout. CONCLUSION: Original analog 12-lead ECG signals can be reconstructed from digital data files with accuracy sufficient for clinical use. Such reconstructions can readily enable automated second opinions for difficult-to-interpret 12-lead ECGs, either locally or remotely through the use of dedicated or cloud-based servers.

Project description:Earlier work demonstrated that ACGME duty hour reform did not adversely affect mortality, with slight improvement noted among specific subgroups.To determine whether resident duty hour reform differentially affected the mortality risk of high severity patients or patients who experienced post-operative complications (failure-to-rescue).Observational study using interrupted time series analysis with data from July 1, 2000 - June 30, 2005. Fixed effects logistic regression was used to examine the change in the odds of mortality or failure-to-rescue (FTR) in more versus less teaching-intensive hospitals before and after duty hour reform.All unique Medicare patients (n = 8,529,595) admitted to short-term acute care non-federal hospitals and all unique VA patients (n = 318,636 patients) with principal diagnoses of acute myocardial infarction, congestive heart failure, gastrointestinal bleeding, stroke or a DRG classification of general, orthopedic or vascular surgery.We measured mortality within 30 days of hospital admission and FTR, measured by death among patients who experienced a surgical complication. The odds of mortality and FTR generally changed at similar rates for higher and lower risk patients in more vs. less teaching intensive hospitals. For example, comparing the mortality risk for the 10% of Medicare patients with highest risk to the other 90% of patients in post-reform year 1 for combined medical an OR of 1.01 [95% CI 0.90, 1.13], for combined surgical an OR of 0.91 [95% CI 0.80, 1.04], and for FTR an OR of 0.94 [95% CI 0.80, 1.09]. Findings were similar in year 2 for both Medicare and VA. The two exceptions were a relative increase in mortality for the highest risk medical (OR 1.63 [95% CI 1.08, 2.46]) and a relative decrease in the high risk surgical patients within VA in post-reform year 1 (OR 0.52 [95% CI 0.29, 0.96]).ACGME duty hour reform was not associated with any consistent improvements or worsening in mortality or failure-to-rescue rates for high risk medical or surgical patients.

Dataset Information

Gradient-induced voltages on 12-lead ECGs during high duty-cycle MRI sequences and a method for their removal considering linear and concomitant gradient terms.

Publications

Gradient-induced voltages on 12-lead ECGs during high duty-cycle MRI sequences and a method for their removal considering linear and concomitant gradient terms.

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