Fast‐response VHF pulsed 2 KW power amplifiers

Quine, Richard W.; Eaton, Gareth R.; Dillon, Shane

doi:10.1002/cmr.b.20074

Cited by 5 publications

(5 citation statements)

References 8 publications

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“…18 To utilize the full power of our 2 kW RF amplifier 31 ͑Tomco Technologies, Norwood SA, Australia͒, the transmit-receive switch of the imager was redesigned utilizing a new protection scheme and high power components. 32 A pulse amplitude modulation switch was added to produce / 2-and -pulses of equal duration.…”

Section: Iie Electron Spin Echo Imagingmentioning

confidence: 99%

Comparison of 250 MHz electron spin echo and continuous wave oxygen EPR imaging methods for in vivo applications

Epel¹,

Sundramoorthy²,

Barth³

et al. 2011

Medical Physics

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Purpose:The authors compare two electron paramagnetic resonance imaging modalities at 250 MHz to determine advantages and disadvantages of those modalities for in vivo oxygen imaging. Methods: Electron spin echo ͑ESE͒ and continuous wave ͑CW͒ methodologies were used to obtain three-dimensional images of a narrow linewidth, water soluble, nontoxic oxygen-sensitive trityl molecule OX063 in vitro and in vivo. The authors also examined sequential images obtained from the same animal injected intravenously with trityl spin probe to determine temporal stability of methodologies. Results: A study of phantoms with different oxygen concentrations revealed a threefold advantage of the ESE methodology in terms of reduced imaging time and more precise oxygen resolution for samples with less than 70 torr oxygen partial pressure. Above ϳ100 torr, CW performed better. The images produced by both methodologies showed pO 2 distributions with similar mean values. However, ESE images demonstrated superior performance in low pO 2 regions while missing voxels in high pO 2 regions. Conclusions: ESE and CW have different areas of applicability. ESE is superior for hypoxia studies in tumors.

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Section: Iie Electron Spin Echo Imagingmentioning

confidence: 99%

Comparison of 250 MHz electron spin echo and continuous wave oxygen EPR imaging methods for in vivo applications

Epel¹,

Sundramoorthy²,

Barth³

et al. 2011

Medical Physics

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“…Relative to standard pulsed EPR, which requires high-power pulsed RF/microwave amplifiers (see, e.g., [17; 18]), much lower power can be used with the Frank sequence. Relative to normal CW operation, the present method shares with normal high-power pulse FID detection the advantage that the magnetic field is not scanned and magnetic field modulation is not required.…”

Section: Resultsmentioning

confidence: 99%

Use of the Frank sequence in pulsed EPR

Tseitlin

Quine

Halpern

et al. 2011

Journal of Magnetic Resonance

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The Frank polyphase sequence has been applied to pulsed EPR of triarylmethyl radicals at 256 MHz (9.1 mT magnetic field), using 256 phase pulses. In EPR, as in NMR, use of a Frank sequence of phase steps permits pulsed FID signal acquisition with very low power microwave/RF pulses (ca. 1.5 mW in the application reported here) relative to standard pulsed EPR. A 0.2 mM aqueous solution of a triarylmethyl radical was studied using a 16 mm diameter cross loop resonator to isolate the EPR signal detection system from the incident pulses.

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“…The manual rotary step-attenuator that controlled the pulse power {7} was placed before the power amplifier. The two-stage high power linear RF amplifier {8} (240–260 MHz, maximum power in the linear regime - 2 kW, 2% maximum duty cycle) manufactured by Tomco Technologies, Norwood SA, Australia (36) was used to amplify pulses to ~1 kW peak power. The 10 dB fixed attenuator {9} on the output of the amplifier reduced the power to 100 W (maximum power was restricted by the power rating of components following the amplifier output).…”

Section: Methodsmentioning

confidence: 99%

A versatile high speed 250‐MHz pulse imager for biomedical applications

Epel

Sundramoorthy

Mailer

et al. 2008

Concepts Magn Reson

109

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A versatile 250 MHz pulse electron paramagnetic resonance (EPR) instrument for imaging of small animals is presented. Flexible design of the imager hardware and software makes it possible to use virtually any pulse EPR imaging modality. A fast pulse generation and data acquisition system based on general purpose PCI boards performs measurements with minimal additional delays. Careful design of receiver protection circuitry allowed us to achieve very high sensitivity of the instrument. In this article we demonstrate the ability of the instrument to obtain three dimensional images using the electron spin echo (ESE) and single point imaging (SPI) methods. In a phantom that contains a 1 mM solution of narrow line (16 μT, peak-to-peak) paramagnetic spin probe we achieved an acquisition time of 32 seconds per image with a fast 3D ESE imaging protocol. Using an 18 minute 3D phase relaxation (T2e) ESE imaging protocol in a homogeneous sample a spatial resolution of 1.4 mm and a standard deviation of T2e of 8.5% were achieved. When applied to in vivo imaging this precision of T2e determination would be equivalent to 2 torr resolution of oxygen partial pressure in animal tissues.

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Fast‐response VHF pulsed 2 KW power amplifiers

Cited by 5 publications

References 8 publications

Comparison of 250 MHz electron spin echo and continuous wave oxygen EPR imaging methods for in vivo applications

Comparison of 250 MHz electron spin echo and continuous wave oxygen EPR imaging methods for in vivo applications

Use of the Frank sequence in pulsed EPR

A versatile high speed 250‐MHz pulse imager for biomedical applications

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