Microwave radiometry for non-invasive detection of vesicoureteral reflux (VUR) following bladder warming

Paul R. Stauffer; Paolo F. Maccarini; Kavitha Arunachalam; Valeria De Luca; Sara Salahi; Alina Boico; Oystein Klemetsen; Yngve Birkelund; Svein K. Jacobsen; Fernando Bardati; Piero Tognolotti; Brent Snow

doi:10.1117/12.875636

22 February 2011 Microwave radiometry for non-invasive detection of vesicoureteral reflux (VUR) following bladder warming

Paul R. Stauffer, Paolo F. Maccarini, Kavitha Arunachalam, Valeria De Luca, Sara Salahi, Alina Boico, Oystein Klemetsen, Yngve Birkelund, Svein K. Jacobsen, Fernando Bardati, Piero Tognolotti, Brent Snow

Author Affiliations +

Proceedings Volume 7901, Energy-based Treatment of Tissue and Assessment VI; 79010V (2011) https://doi.org/10.1117/12.875636
Event: SPIE BiOS, 2011, San Francisco, California, United States

Abstract

Background: Vesicoureteral reflux (VUR) is a serious health problem leading to renal scarring in children. Current VUR detection involves traumatic x-ray imaging of kidneys following injection of contrast agent into bladder via invasive Foley catheter. We present an alternative non-invasive approach for detecting VUR by radiometric monitoring of kidney temperature while gently warming the bladder. Methods: We report the design and testing of: i) 915MHz square slot antenna array for heating bladder, ii) EMI-shielded log spiral microstrip receive antenna, iii) high-sensitivity 1.375GHz total power radiometer, iv) power modulation approach to increase urine temperature relative to overlying perfused tissues, and v) invivo porcine experiments characterizing bladder heating and radiometric temperature of aaline filled 30mL balloon "kidney" implanted 3-4cm deep in thorax and varied 2-6°C from core temperature. Results: SAR distributions are presented for two novel antennas designed to heat bladder and monitor deep kidney temperatures radiometrically. We demonstrate the ability to heat 180mL saline in in vivo porcine bladder to 40-44°C while maintaining overlying tissues <38°C using time-modulated square slot antennas coupled to the abdomen with room temperature water pad. Pathologic evaluations confirmed lack of acute thermal damage in pelvic tissues for up to three 20min bladder heat exposures. The radiometer clearly recorded 2-6°C changes of 30mL "kidney" targets at depth in 34°C invivo pig thorax. Conclusion: A 915MHz antenna array can gently warm in vivo pig bladder without toxicity while a 1.375GHz radiometer with log spiral receive antenna detects ≥2°C rise in 30mL "urine" located 3-4cm deep in thorax, demonstrating more than sufficient sensitivity to detect Grade 4-5 reflux of warmed urine for non-invasive detection of VUR.

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Paul R. Stauffer, Paolo F. Maccarini, Kavitha Arunachalam, Valeria De Luca, Sara Salahi, Alina Boico, Oystein Klemetsen, Yngve Birkelund, Svein K. Jacobsen, Fernando Bardati, Piero Tognolotti, and Brent Snow "Microwave radiometry for non-invasive detection of vesicoureteral reflux (VUR) following bladder warming", Proc. SPIE 7901, Energy-based Treatment of Tissue and Assessment VI, 79010V (22 February 2011); https://doi.org/10.1117/12.875636

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