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Background: Testing MRI gradient‐induced heating of implanted medical devices is required by regulatory organizations and others. A gradient heating test of the ISO 10974 Technical Specification (TS) for active implants was adopted for this study of passive hip implants. All but one previous study of hip implants used nonuniform gradient exposure fields in clinical scanners and reported heating of less than 5 °C. This present study adapted methods of the TS, addressing the unmet need for identifying worst‐case heating via exposures to uniform gradient fields. Purpose: To identify gradient‐field parameters affecting maximum heating in vitro for a hip implant and a cylindrical titanium disk. Study Type: Computational simulations and experimental validation of induced heating. Phantom: Tissue‐simulating gel. Field Strength: 42 T/s RMS, sinusoidal, continuous B fields with high spatial uniformity Assessment: Hip implant heating at 1–10 kHz, via computational modeling, validated by limited point measurements. Experimental measurements of exposures of an implant at 42 T/s for 4, 6, and 9 kHz, analyzed at 50, 100, and 150 seconds. Statistical Tests: One sample student's t‐test to assess difference between computational and experimental results. Experimental vs. computational results were not significantly different (p < 0.05). Results: Maximum simulated temperature rise (10‐minute exposure) was 10 °C at 1 kHz and 0.66 °C at 10 kHz. The ratio of the rise for 21 T/s vs. 42 T/s RMS was 4, after stabilizing at 50 seconds (dB/dt ratio squared). Data Conclusions: Heating of an implant is proportional to the frequency of the B field and the implant's cross‐sectional area and is greater for a thickness on the order of its skin depth. Testing with lower values of dB/dt RMS with lower cost amplifiers enables prediction of heating at higher values for dB/dt squared (per ISO TS) with identical frequency components and waveforms, once thermal equilibrium occurs. Evidence Level: 1 Technical Efficacy: Stage 1 [ABSTRACT FROM AUTHOR]

Purpose: There is increasing use of open‐bore vertical MR systems that consist of two planar RF coils. A recent study showed that the RF‐induced heating of a neuromodulation device was much lower in the open‐bore system at the brain and the chest imaging landmarks. This study focused on the hip and knee implants and compared the specific absorption rate (SAR) distribution in human models in a 1.2T open‐bore coil with that of a 1.5T conventional birdcage coil. Methods: Computational modeling results were compared against the measurement values using a saline phantom. The differences in RF exposure were examined between a 1.2T open‐bore coil and a 1.5T conventional birdcage coil using SAR in an anatomical human model. Results: Modeling setups were validated. The body placed closed to the coil elements led to high SAR values in the birdcage system compared with the open‐bore system. Conclusion: Our computational modeling showed that the 1.2T planar system demonstrated a lower intensity of SAR distribution adjacent to hip and knee implants compared with the 1.5T conventional birdcage system. [ABSTRACT FROM AUTHOR]

Background: Auditory and non‐auditory safety concerns associated with the appreciable sound levels inherent to magnetic resonance imaging (MRI) procedures exist for neonates. However, current gaps in knowledge preclude making an adequate risk assessment. Purpose: To measure acoustic exposure (duration, intensity, and frequency) during neonatal brain MRI and compare these values to existing hearing safety limits and data. Study Type: Phantom. Phantom: Cylindrical doped water phantom. Field Strength/Sequence: Neonatal brain protocols acquired at 1–3 T. Scans in the model protocol included a diffusion tensor imaging scan, a gradient echo, a three‐dimensional (3D) fast spin echo, 3D fast spin‐echo single‐shots, a spin echo, a turbo spin echo, a 3D arterial spin labeling scan, and a susceptibility‐weighted fast spin‐echo scan. Assessment: The sound pressure levels (SPLs), frequency profile, and durations of five neonatal brain protocols on five MR scanners (scanner A [3 T, whole‐body], scanner B [1.5 T, whole‐body], scanner C [1 T, dedicated neonatal], scanner D [1.5 T, whole‐body], and scanner E [3 T, whole‐body]) located at three different sites were recorded. The SPLs were then compared to the International Electrotechnical Commission (IEC) hearing safety limit and existing data of infant non‐auditory responses to loud sounds to assess risk. Statistical Tests: Mann‐Whitney U test to assess whether the dedicated neonatal scanner was quieter than the other machines. Results: The average level A‐weighted equivalent value (LAEQ) across all five MR scanners and scans was 92.88 dBA and the range of LAEQs across all five MR scanners and scans was 80.8–105.31 dBA. The duration of the recorded neonatal protocols maintained by neonatal scanning facilities (from scanners A, B, and C) ranged from 27:33 to 37:06 minutes. Data Conclusion: Neonatal protocol sound levels straddled existing notions of risk, exceeding sound levels known to cause non‐auditory responses in neonates but not exceeding the IEC MRI SPL safety limit. Level of Evidence: 5 Technical Efficacy: Stage 5 [ABSTRACT FROM AUTHOR]