Patterned thin metal film for the lateral resolution measurement of photoacoustic tomography.
BACKGROUND
Image quality assessment method of photoacoustic tomography has not been completely standardized yet. Due to the combined nature of photonic signal generation and ultrasonic signal transmission in biological tissue, neither optical nor ultrasonic traditional methods can be used without modification. An optical resolution measurement technique was investigated for its feasibility for resolution measurement of photoacoustic tomography.


METHODS
A patterned thin metal film deposited on silica glass provides high contrast in optical imaging due to high reflectivity from the metal film and high transmission from the glass. It provides high contrast when it is used for photoacoustic tomography because thin metal film can absorb pulsed laser energy. An US Air Force 1951 resolution target was used to generate patterned photoacoustic signal to measure the lateral resolution. Transducer with 2.25 MHz bandwidth and a sample submerged in water and gelatinous block were tested for lateral resolution measurement.


RESULTS
Photoacoustic signal generated from a thin metal film deposited on a glass can propagate along the surface or through the surrounding medium. First, a series of experiments with tilted sample confirmed that the measured photoacoustic signal is what is propagating through the medium. Lateral resolution of the photoacoustic tomography system was successfully measured for water and gelatinous block as media: 0.33 mm and 0.35 mm in water and gelatinous material, respectively, when 2.25 MHz transducer was used. Chicken embryo was tested for biomedical applications.


CONCLUSIONS
A patterned thin metal film sample was tested for its feasibility of measuring lateral resolution of a photoacoustic tomography system. Lateral resolutions in water and gelatinous material were successfully measured using the proposed method. Measured resolutions agreed well with theoretical values.
Center for Devices and Radiological Health, US Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA. do-hyun.kim@fda.hhs.gov
Do-Hyun
DH
Kim
Dong-Ho
DH
Shin
Sang Hun
SH
Ryu
Chul-Gyu
CG
Song
D005898:Glass / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D061088:Photoacoustic Techniques / Q000295:instrumentation / Q000379:methods*; D011786:Quality Control; D012822:Silicon Dioxide / Q000737:chemistry; D013016:Sound; D014054:Tomography / Q000295:instrumentation / Q000379:methods*; D014159:Transducers; D014867:Water / Q000737:chemistry
D008670:Metals; D014867:Water; D012822:Silicon Dioxide