Measurement of Power Density in a Lossy Material by Means of Electro-Magnetically Induced Acoustic Signals for Non-Invasive Determination of Spatial Thermal Absorption in Connection with Pulsed Hyperthermia

Caspers, F.; Conway, J.

doi:10.1109/euma.1982.333121

Cited by 21 publications

(7 citation statements)

References 5 publications

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“…6 Microwave-induced thermoacoustics was used to quantify physical parameters in media such as the power density and the concentration of a given substance. [7][8][9] Several investigators employed microwave-induced thermoacoustics in the 1980s for imaging of biological tissues. [10][11][12][13][14][15] However, these early works did not produce any tomographic or depthresolved images.…”

Section: Introductionmentioning

confidence: 99%

Scanning microwave-induced thermoacoustic tomography: Signal, resolution, and contrast

Ku¹,

Wang

2001

Med. Phys.

155

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Scanning thermoacoustic tomography was explored in the microwave region of the electromagnetic spectrum. Short microwave pulses were used to induce acoustic waves by thermoelastic expansion in biological tissues. Cross sections of tissue samples were imaged by a linear scan of the samples while a focused ultrasonic transducer detected the time-resolved thermoacoustic signals. Based on the microwave-absorption properties of normal and cancerous breast tissues, the piezoelectric signals in response to the thermoacoustic contrast were investigated over a wide range of electromagnetic frequencies and depths of tumor locations. The axial resolution is related to the temporal profile of the microwave pulses and to the impulse response of the ultrasonic transducer. The lateral resolution is related to the numerical aperture of the ultrasonic transducer as well as to the frequency spectra of the piezoelectric signals in the time window corresponding to the axial resolution. Gain compensation, counteracting the microwave attenuation, was applied to enhance the image contrast.

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Section: Introductionmentioning

confidence: 99%

Scanning microwave-induced thermoacoustic tomography: Signal, resolution, and contrast

Ku¹,

Wang

2001

Med. Phys.

155

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“…AG Bell observed the thermoacoustic (TA) effect over a century ago, and application to diagnostic imaging was proposed in the 1980s (Bowen et al, 1981, Caspers and Conway, 1982, Nasoni et al, 1984). Thermoacoustic imaging is a hybrid technique that relies upon conversion of electromagnetic energy into mechanical energy via thermal expansion to create TA pressure pulses.…”

Section: Introductionmentioning

confidence: 99%

Thermoacoustic contrast of prostate cancer due to heating by very high frequency irradiation

Hull

Thomas

et al. 2015

Phys. Med. Biol.

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Applying the thermoacoustic (TA) effect to diagnostic imaging was first proposed in the 1980s. The object under test is irradiated by high-power pulses of electromagnetic energy, which heat tissue and cause thermal expansion. Outgoing TA pressure pulses are detected by ultrasound transducers and reconstructed to provide images of the object. The TA contrast mechanism is strongly dependent upon the frequency of the irradiating electromagnetic pulse. When very high frequency (VHF) electromagnetic irradiation is utilized, TA signal production is driven by ionic content. Prostatic fluids contain high levels of ionic metabolites, including citrate, zinc, calcium, and magnesium. Healthy prostate glands produce more ionic metabolites than diseased glands. VHF pulses are therefore expected to generate stronger TA signal in healthy prostate glands than in diseased glands. A benchtop system for performing ex vivo thermoacoustic computed tomography with VHF energy is described and images are presented. The system utilizes irradiation pulses of 700 ns duration exceeding 20 kW power. Reconstructions frequently visualize anatomic landmarks such as the urethra and verumontanum. TA reconstructions from three freshly excised human prostate glands with little, moderate, and severe cancerous involvement are compared with histology. TA signal strength is negatively correlated with percent cancerous involvement in this small sample size. For the 45 regions of interest analyzed, a reconstruction value of 0.4 mV provides 100% sensitivity but only 29% specificity. This sample size is far too small to draw sweeping conclusions, but the results warrant a larger volume study including comparison of TA images to the gold standard, histology.

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“…6 Microwave-induced thermoacoustics was used to quantify physical parameters in media such as the power density and the concentration of a given substance. [7][8][9] Microwave-induced thermoacoustics was also employed by several investigators in the 1980s for imaging of biological tissues. [10][11][12][13][14][15] However, these early works did not produce any tomographic or depth-resolved images.…”

Section: Introductionmentioning

confidence: 99%

Scanning thermoacoustic tomography in biological tissue

2000

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Microwave-induced thermoacoustic tomography was explored to image biological tissue. Short microwave pulses irradiated tissue to generate acoustic waves by thermoelastic expansion. The microwave-induced thermoacoustic waves were detected with a focused ultrasonic transducer. Each time-domain signal from the ultrasonic transducer represented a one-dimensional image along the acoustic axis of the ultrasonic transducer similar to an ultrasonic A-scan. Scanning the system perpendicularly to the acoustic axis of the ultrasonic transducer would generate multi-dimensional images. Two-dimensional tomographic images of biological tissue were obtained with 3-GHz microwaves. The axial and lateral resolutions were characterized. The time-domain piezo-electric signal from the ultrasonic transducer in response to the thermoacoustic signal was simulated theoretically, and the theoretical result agreed with the experimental result very well.

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Measurement of Power Density in a Lossy Material by Means of Electro-Magnetically Induced Acoustic Signals for Non-Invasive Determination of Spatial Thermal Absorption in Connection with Pulsed Hyperthermia

Cited by 21 publications

References 5 publications

Scanning microwave-induced thermoacoustic tomography: Signal, resolution, and contrast

Scanning microwave-induced thermoacoustic tomography: Signal, resolution, and contrast

Thermoacoustic contrast of prostate cancer due to heating by very high frequency irradiation

Scanning thermoacoustic tomography in biological tissue

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