Advancements at the Lower End: Advances in HF, VHF, and UHF Systems and Technology

Caverly, Robert H.; Breed, Gary; Cantrell, W.H.; Eron, M.; Garcia, Jose; Kondrath, Nisha; Myer, Dan; Ruiz, M. Nieves; Walker, John L.

doi:10.1109/mmm.2014.2367855

Cited by 14 publications

(10 citation statements)

References 50 publications

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“…6 depicts a temperature sensor tip aligned with the exposed tip of an 800 µm Cu wire of length 0.41λ, coated with 350 µm of plastic insulation. 1 The temperature rise after 5 minutes of MRI scanning was recorded for various lengths of insulated wire. The insulation was 350 µm thick, but thinner and thicker variants were also tested.…”

Section: Temperature Was Measured Using An Optocon Fotempmentioning

confidence: 99%

“…The significant benefit of a factor of two would require >200 Ω/m. 1 Optocon say that the "final few millimeters" of the probe is the active sensing region. Our experience suggests that the temperature of the last 1 mm of the probe tip contributes to the reading.…”

Section: Impact Of Wire Resistancementioning

confidence: 99%

“…A 3-Tesla (3 T) MRI machine can deliver peak pulses in the order of 30 kW at 128 MHz. [1] This can lead to significant heating of the patient. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommends maximum localized temperatures of 38 • C in the head and 39 • C in the torso, representing 1-2 • C of heating.…”

Section: Introductionmentioning

confidence: 99%

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Electromagnetic techniques to minimize the risk of hazardous local heating around medical implant electrodes during MRI scanning

McCabe

Scott

Butler³

2015

2015 European Microwave Conference (EuMC)

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Magnetic Resonance Imaging (MRI) scans are contraindicated for many patients with medical implants. We establish the circumstances that cause, and the resistances required to ameliorate and to eliminate dangerous levels of MRI-induced heating that occur at the exposed, distal end of an electrical lead implanted in tissue. Simulated predictions are compared with measurements made at 128 MHz in a 3-Tesla MRI machine. A low resistance at kilohertz frequencies is sought by implant makers, in contrast with the high resistance demanded for safety. The practicality of presently-developed strategies to prevent tissue damage is brought into question. We examine the extent to which skin-depth and transmission-line properties can be manipulated to improve safety.Index Terms-Biomedical electrodes, medical diagnostic imaging, dipole antennas, electromagnetic modeling.

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Section: Temperature Was Measured Using An Optocon Fotempmentioning

confidence: 99%

Section: Impact Of Wire Resistancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electromagnetic techniques to minimize the risk of hazardous local heating around medical implant electrodes during MRI scanning

McCabe

Scott

Butler³

2015

2015 European Microwave Conference (EuMC)

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“…Because of the need to faithfully reproduce these sophisticated waveforms, the power amplifiers (PAs) need to be highly linear and so Class A amplifiers are the rule in MRI work, although there is work on high-power linearized PAs for MRI use. Traditionally, these high-power PAs have been rack mounted and located in a separate room (the so-called equipment room) from the scan room containing the B0 magnet ( Figure 17(a) [45]). This allowed the heat generated with low-efficiency Class A amplification (and with peak to average power ratio of 6 dB, efficiencies are even lower than the typical Class A PA) to be easily dissipated without heating up the scan room.…”

Section: Transmitters and Power Amplifiersmentioning

confidence: 99%

“…Figure 17. (a) Rack-mounted, 16-channel, 1 kW/channel PAs for a 7-T MRI system [45]. (b) An in-bore PA array with 16 channels, 1 kW/channel [46].…”

Section: Rf Cablingmentioning

confidence: 99%

MRI Fundamentals: RF Aspects of Magnetic Resonance Imaging (MRI)

Caverly

2015

IEEE Microwave

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Design and robustness improvement of high‐performance LNA using 0.15 μm GaN technology for X‐band applications

Zafar

Akoglu

Aras

et al. 2022

Circuit Theory & Apps

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In this paper, we present a highly robust GaN-based X-band low-noise amplifier (LNA) showing promising small-signal and noise performance as well as good linearity. The LNA is fabricated using in-house 0.15 μm AlGaN/GaN on a SiC HEMT process. Owing to the optimum choice of HEMT topologies and simultaneous matching technique, LNA achieves a noise figure better than 2 dB, output power at 1 dB gain compression higher than 19 dB, input and output reflection coefficients better than À9 and À11 dB, respectively. The small-signal gain of LNA is more than 19 dB for the whole band, and NF has a minimum of 1.74 dB at 10.2 GHz. LNA obtains an OIP3 up to 34.2 dBm and survives input power as high as 42 dBm. Survivability is investigated in terms of gain compression and forward gate current. Reverse recovery time (RRT), a crucial parameter for radar front-ends, is explored with respect to the RC time constant and trap phenomenon. The analysis shows that the significant contribution in RRT is due to traps while the RC time constant is in the nanoseconds range. Moreover, this study also addresses the requirement and choice of a DC gate feed resistor for the subsequent stages in a multi-stage design. The size of the designed LNA chip is 3 mm Â 1.2 mm only.

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Advancements at the Lower End: Advances in HF, VHF, and UHF Systems and Technology

Cited by 14 publications

References 50 publications

Electromagnetic techniques to minimize the risk of hazardous local heating around medical implant electrodes during MRI scanning

Electromagnetic techniques to minimize the risk of hazardous local heating around medical implant electrodes during MRI scanning

MRI Fundamentals: RF Aspects of Magnetic Resonance Imaging (MRI)

Design and robustness improvement of high‐performance LNA using 0.15 μm GaN technology for X‐band applications

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