RESUMEN
OBJECTIVE: A photoacoustic signal is proportional to the product of the optical absorption coefficient and the local light fluence; quantitative photoacoustic measurements of the optical absorption coefficients, therefore, require an accurate compensation of optical fluence variation. Usually, an additional diffuse optical tomography is incorporated to estimate the light fluence variation, but it is often troubled with the bulky measurement system. On this note, we present a dual-modality photoacoustic fusion imaging method that is implemented with a normal photoacoustic imaging (PAI) device. METHODS: A single piezoelectric transducer is employed to receive the photoacoustic waves and passive ultrasound (PU) waves simultaneously. Since the PU wave is generated by the backscattering and diffuse reflection photons, it has the capacity to facilitate diffuse reflectance (DR) imaging. We merged photoacoustic and DR imaging based on their dual-modality with a compensation of the optical fluence variation. RESULTS: The absorption coefficient differences caused by the light fluence variation are reduced more than half with the proposed method, when comparing to the pure photoacoustic imaging. CONCLUSION: The dual-modality photoacoustic fusion imaging is able to correct the PAI errors caused by the optical fluence variation. SIGNIFICANCE: The proposed method can be widely accepted by different PAI applications to compensate the light fluence variations without any additional required element.
Asunto(s)
Procesamiento de Imagen Asistido por Computador/métodos , Técnicas Fotoacústicas/métodos , Animales , Diseño de Equipo , Luz , Músculos/diagnóstico por imagen , Fantasmas de Imagen , Porcinos , UltrasonografíaRESUMEN
As one of the fastest-growing imaging modalities in recent years, photoacoustic imaging has attracted tremendous research interest for various applications including anatomical, functional and molecular imaging. Majority of the photoacoustic imaging systems are based on time-domain pulsed photoacoustic method, which utilizes pulsed laser source to induce wideband photoacoustic signal revealing optical absorption contrast. An alternative way is frequency-domain photoacoustic method utilizing chirping modulation of laser intensity to achieve lower system cost. In this paper, we report another way of photoacoustic method, called phase-domain photoacoustic sensing, which explores the phase difference between two consequent intensity-modulated laser pulses induced photoacoustic measurements to reveal the optical property. The basic principle is introduced, modelled and experimentally validated in this paper, which opens another potential pathway to perform photoacoustic sensing and imaging eliminating acoustic detection variations beyond the conventional time-domain and frequency-domain photoacoustic methods.
Asunto(s)
Técnicas Fotoacústicas , Rayos Láser , Luz , Imagen Molecular , Análisis EspectralRESUMEN
GOAL: Hyperthermia therapy requires tight temperature control to achieve selective killing of cancerous tissue with minimal damage on surrounding healthy tissues. METHODS: To this end, accurate temperature monitoring and subsequent heating control are critical. However, an economic, portable, and real-time temperature control solution is currently lacking. To bridge this gap, we present a novel portable close-loop system for hyperthermia temperature control, in which photoacoustic technique is proposed for noninvasive real-time temperature measurement. Exploiting the high sensitivity of photoacoustics, the temperature is monitored with an accuracy of around 0.18 °C and then fed back to a controller implemented on field programmable gate array (FPGA) for temperature control. Dubbed as portable hyperthermia feedback controller (pHFC), it stabilizes the temperature at preset values by regulating the hyperthermia power with a proportional-integral-derivative (PID) algorithm; and to facilitate digital implementation, the pHFC further converts the PID output into switching values (0 and 1) with the pulse width modulation (PWM) algorithm. RESULTS: Proof-of-concept hyperthermia experiments demonstrate that the pHFC system is able to bring the temperature from baseline to predetermined value with an accuracy of 0.3° and a negligible temperature overshoot. CONCLUSION: The pHFC can potentially be translated to clinical applications with customized hyperthermia system design. SIGNIFICANCE: This paper can facilitate future efforts in seamless integration of close-loop temperature control solution and various clinical hyperthermia systems.
Asunto(s)
Hipertermia Inducida/métodos , Nanopartículas de Magnetita/química , Técnicas Fotoacústicas/métodos , Procesamiento de Señales Asistido por Computador , Retroalimentación , Humanos , Modelos Biológicos , Fantasmas de Imagen , Técnicas Fotoacústicas/instrumentaciónRESUMEN
A noninvasive method of stimulating the nerve by applying radiofrequency has been presented. The design is based on the concept of magnetic resonance based power transfer. A comparison between electric field on the nerve at the frequency of 450-550 KHz with vacuum placed under a human tissue and the case where it is replaced with a resonant and non-resonant structure was analysed. Calculations were performed by using Ansoft HFSS. Power savings of 7.15% was observed when resonant structures were used, compared to vacuum. Theoretical calculation and simulation of fields were presented.