Non-invasive vesicoureteral reflux imaging

Snow, Brent W.; Taylor, Michael

doi:10.1016/j.jpurol.2010.02.211

Cited by 34 publications

(32 citation statements)

References 39 publications

(27 reference statements)

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“…A MW diagnostic system with 915 MHz antenna array for external bladder warming to fever range temperatures (40–45°C) and a radiometer for passive temperature monitoring was recently reported for noninvasive detection of warm reflux in kidneys [11]. Due to high blood perfusion inside the kidneys, transient temperature change during warm reflux is expected to last less than a minute at depth.…”

Section: Discussionmentioning

confidence: 99%

“…In the proposed system, urine inside the bladder is raised to fever range temperature of 40–45°C using an external 915 MHz MW hyperthermia device requiring no catheterization or radiation exposure. In this work we present the theory and modeling efforts for the radiometric antenna design, frequency selection and detector sensitivity estimation for the system used in the animal study [11]. …”

Section: Introductionmentioning

confidence: 99%

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Modeling the detectability of vesicoureteral reflux using microwave radiometry

et al. 2010

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We present the modeling efforts on antenna design, frequency selection and receiver sensitivity estimation to detect vesicoureteral reflux (VUR) using microwave (MW) radiometry as the warm urine from the bladder maintained at fever range temperature using a MW hyperthermia device reflows into the kidneys. Radiometer center frequency (f c ), frequency band (Δf), and aperture radius (r a ) of the physical antenna for kidney temperature monitoring are determined using a simplified universal antenna model with circular aperture. Anatomical information extracted from computed tomography (CT) images of children age 4-6 years is used to construct a layered 3D tissue model. Radiometric antenna efficiency is evaluated in terms of the ratio between the power collected from the target at depth and the total power received by the antenna (η). Power ratio of the theoretical antenna is used to design a microstrip log spiral antenna with directional radiation pattern over f c ± Δf/2. Power received by the log spiral from the deep target is enhanced using a thin low-loss dielectric matching layer. A cylindrical metal cup is proposed to shield the antenna from electromagnetic interference (EMI). Transient thermal simulations are carried out to determine the minimum detectable change in antenna brightness temperature (δT B ) for 15-25 mL urine refluxes at 40-42°C located 35 mm from the skin surface. Theoretical antenna simulations indicate maximum η over 1.1-1.6 GHz for r a = 30-40 mm. Simulations of the 35 mm radius tapered log spiral yielded higher power ratio over f c ± Δf/2 for the 35-40 mm deep targets in the presence of an optimal matching layer. Radiometric temperature calculations indicate δT B ≥ 0.1 K for the 15 mL urine at 40°C and 35 mm depth. Higher η and δT B were observed for the antenna and matching layer inside the metal cup. Reflection measurements of the log spiral in saline phantom are in agreement with the simulation data. Numerical study suggests a radiometer with f c =1.35 GHz, Δf = 500 MHz and detector sensitivity better than 0.1 K would be the appropriate tool to noninvasively detect VUR using the log spiral antenna.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling the detectability of vesicoureteral reflux using microwave radiometry

et al. 2010

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“…Imaging studies currently recommended to detect reflux in children diagnosed with UTI involve bladder catheterization, sedation and ionizing radiation [2, 3]. The unpleasant procedure and long term effect of ionizing radiation in infants and children [4, 5] have motivated the development of alternative noninvasive imaging modalities for VUR detection [6]. The MW device proposed in [6] combines a 915 MHz hyperthermia applicator for external bladder warming to moderate temperatures (40–45°C) and MW radiometry to passively monitor the kidneys to detect the warm reflux.…”

Section: Introductionmentioning

confidence: 99%

Detection of Vesicoureteral Reflux Using Microwave Radiometry—System Characterization With Tissue Phantoms

Arunachalam

Maccarini

Luca

et al. 2011

IEEE Trans. Biomed. Eng.

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Microwave (MW) radiometry is proposed for passive monitoring of kidney temperature to detect vesicoureteral reflux (VUR) of urine that is externally heated by a MW hyperthermia device and thereafter reflows from the bladder to kidneys during reflux. Here we characterize in tissuemimicking phantoms the performance of a 1.375 GHz radiometry system connected to an electromagnetically (EM) shielded microstrip log spiral antenna optimized for VUR detection. Phantom EM properties are characterized using a coaxial dielectric probe and network analyzer (NA). Power reflection and receive patterns of the antenna are measured in layered tissue phantom. Receiver spectral measurements are used to assess EM shielding provided by a metal cup surrounding the antenna. Radiometer and fiberoptic temperature data are recorded for varying volumes (10-30 mL) and temperatures (40-46°C) of the urine phantom at 35 mm depth surrounded by 36.5°C muscle phantom. Directional receive pattern with about 5% power spectral density at 35 mm target depth and better than −10dB return loss from tissue load are measured for the antenna. Antenna measurements demonstrate no deterioration in power reception and effective EM shielding in the presence of the metal cup. Radiometry power measurements are in excellent agreement with the temperature of the kidney phantom. Laboratory testing of the radiometry system in temperature controlled phantoms supports the feasibility of passive kidney thermometry for VUR detection.

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“…The experiments were carried out using a heating cycle where the microwave power is turned on for a given time and then turned off for the remaining part of the cycle; a similar procedure as the one used by the current authors in animal testing of bladder heating [19], [30]. The off-time in the cycle allows time for cooling of perfused skin relative to non-perfused urine in the bladder, but most important, it provides measurement periods for the microwave radiometry without interference from microwave heating.…”

Section: Methodsmentioning

confidence: 99%

“…The concept is based on heating of the pediatric bladder and radiometric measurement of temperature rise in the kidney. Preliminary results using animal experiments are promising [19], [20]. In this paper, we investigate the task of heating a pediatric bladder safely using microwaves for both heating and radiometry.…”

Section: Introductionmentioning

confidence: 99%

Vesicoureteral Reflux in Children: A Phantom Study of Microwave Heating and Radiometric Thermometry of Pediatric Bladder

Birkelund

Klemetsen

Jacobsen

et al. 2011

IEEE Trans. Biomed. Eng.

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We have investigated the use of microwave heating and radiometry to safely heat urine inside a pediatric bladder. The medical application for this research is to create a safe and reliable method to detect vesicoureteral reflux, a pediatric disorder, where urine flow is reversed and flows from the bladder back up into the kidney. Using fat and muscle tissue models, we have performed both experimental and numerical simulations of a pediatric bladder model using planar dual concentric conductor microstrip antennas at 915 MHz for microwave heating. A planar elliptical antenna connected to a 500 MHz bandwidth microwave radiometer centered at 3.5 GHz was used for non-invasive temperature measurement inside tissue. Temperatures were measured in the phantom models at points during the experiment with implanted fiberoptic sensors, and 2D distributions in cut planes at depth in the phantom with an infrared camera at the end of the experiment. Cycling between 20 second with 20 Watts power for heating, and 10 seconds without power to allow for undisturbed microwave radiometry measurements, the experimental results show that the target tissue temperature inside the phantom increases fast and that the radiometer provides useful measurements of spatially averaged temperature of the illuminated volume. The presented numerical and experimental results show excellent concordance, which confirms that the proposed system for microwave heating and radiometry is applicable for safe and reliable heating of pediatric bladder.

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Non-invasive vesicoureteral reflux imaging

Cited by 34 publications

References 39 publications

Modeling the detectability of vesicoureteral reflux using microwave radiometry

Modeling the detectability of vesicoureteral reflux using microwave radiometry

Detection of Vesicoureteral Reflux Using Microwave Radiometry—System Characterization With Tissue Phantoms

Vesicoureteral Reflux in Children: A Phantom Study of Microwave Heating and Radiometric Thermometry of Pediatric Bladder

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