Thermoacoustic contrast of prostate cancer due to heating by very high frequency irradiation. Phys Med Biol 2015 Jan 21;60(2):689-708
Date
01/03/2015Pubmed ID
25554968Pubmed Central ID
PMC4292912DOI
10.1088/0031-9155/60/2/689Scopus ID
2-s2.0-84920836388 (requires institutional sign-in at Scopus site) 16 CitationsAbstract
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 TA 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.
Author List
Patch SK, Hull D, Thomas M, Griep SK, Jacobsohn K, See WAAuthors
Kenneth Jacobsohn MD Professor in the Urologic Surgery department at Medical College of WisconsinSarah K. Patch PhD Associate Professor in the Physics department at University of Wisconsin - Milwaukee
MESH terms used to index this publication - Major topics in bold
AcousticsBody Temperature
Computer Simulation
Contrast Media
Electromagnetic Radiation
Hot Temperature
Humans
Image Enhancement
Image Processing, Computer-Assisted
Male
Prostatic Neoplasms
Signal-To-Noise Ratio
