Article Figures & Data
Figures
- Fig 1.
Phantom and experimental setup. Photograph shows the plexiglass phantom before filling with the gel saline solution shows the plastic grid frame and adjustable posts, which allow precise positioning and support of the dual implantable pulse generators, extensions, and DBS leads. The cables for the four fluoroptic thermometry probes are seen coursing off the bottom of the photograph.
- Fig 2.
DBS lead mean temperature elevation as a function of local SAR. Plot shows greatest observed mean temperature elevation for 1 min of data collection, obtained at the time of peak heating during the 10- to 15-minute imaging time interval, versus local SAR value for single and multisection fast spin-echo images. Linear regression (all data points): r = 0.994, P < .001, x variable = 0.88, and y intercept = −0.13.
Tables
Sequence SAR (W/kg) Temperature (°C) ΔTmean (°C) ΔTmax (°C) P < .01 Local Whole Body Baseline Imaging Standardized sequence FSE SS 7.13 0.24 24.8 ± 0.1 30.5 ± 0.1 5.7 5.8 * FSE SS 3.87 0.13 24.6 ± 0.2 28.2 ± 0.1 3.6 3.7 * FSE SS 2.10 0.07 24.4 ± 0.1 26.1 ± 0.1 1.7 2.3 * FSE SS 1.12 0.04 24.9 ± 0.1 25.8 ± 0.2 0.9 1.3 * FSE MS 7.26 0.24 24.8 ± 0.1 31.3 ± 0.1 6.5 6.7 * FSE MS 2.17 0.07 24.8 ± 0.1 26.6 ± 0.1 1.8 2.0 * FSE MS 0.50 0.02 24.1 ± 0.1 24.2 ± 0.1 0.1 0.3 Clinical sequences EPI 0.14 0.00 23.7 ± 0.1 23.9 ± 0.1 0.2 0.3 MPRAGE 0.36 0.01 23.3 ± 0.1 23.4 ± 0.1 0.1 0.2 QMT 3.44 0.11 23.8 ± 0.1 24.8 ± 0.1 1.0 1.5 * MT MRA 4.28 0.14 24.2 ± 0.1 25.8 ± 0.1 1.6 1.8 * Note.—SAR indicates specific absorption rate; ΔTmean, mean temperature increase; ΔTmax, maximum observed temperature increase; FSE, fast spin-echo; SS, single section; MS, multisection; EPI, echo-planar imaging; MPRAGE, magnetization prepared rapid acquisition gradient-echo; QMT, quantitative magnetization transfer; MT MRA, magnetization transfer-suppressed MR angiography. Baseline temperature is the mean ± 1 SD of 12 consecutive measurements (1 min of data) at ambient conditions before the start of the MR imaging sequence. Imaging temperature is the mean ± 1 SD of 12 consecutive measurements (1 min of data) obtained during 10 to 15 min of continuous imaging, encompassing the time of the maximum observed temperature increase. For all measurements, the background reference temperature increase was <0.5°C.
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