Acoustic and Photoacoustic Molecular Imaging of Cancer
JOURNAL OF NUCLEAR MEDICINE
2013; 54 (11): 1851-1854
Characterizing dynamics of shear waves induced with acoustic radiation force impulse in histotripsy lesions for treatment feedback.
journal of the Acoustical Society of America
2013; 134 (5): 4010-?
Ultrasound and combined optical and ultrasonic (photoacoustic) molecular imaging have shown great promise in the visualization and monitoring of cancer through imaging of vascular and extravascular molecular targets. Contrast-enhanced ultrasound with molecularly targeted microbubbles can detect early-stage cancer through the visualization of targets expressed on the angiogenic vasculature of tumors. Ultrasonic molecular imaging can be extended to the imaging of extravascular targets through use of nanoscale, phase-change droplets and photoacoustic imaging, which provides further molecular information on cancer given by the chemical composition of tissues and by targeted nanoparticles that can interact with extravascular tissues at the receptor level. A new generation of targeted contrast agents goes beyond merely increasing imaging signal at the site of target expression but shows activatable and differential contrast depending on their interactions with the tumor microenvironment. These innovations may further improve our ability to detect and characterize tumors. In this review, recent developments in acoustic and photoacoustic molecular imaging of cancer are discussed.
View details for DOI 10.2967/jnumed.112.115568
View details for Web of Science ID 000326876800005
View details for PubMedID 24187042
Histotripsy mechanically fractionates soft tissues into fluid-like homogenates that cannot support shear waves. We hypothesize that dynamics of shear waves excited from a histotripsy lesion using acoustic radiation force impulse (ARFI) change progressively during the fractionation process, and such change is related to the degree of tissue fractionation. To test this hypothesis, lesions with different degrees of fractionation were created in agar-graphite tissue mimicking phantoms and ex vivo kidneys with increasing numbers of histotripsy pulses (3-cycle 750- kHz ultrasound pulses at a peak negative/positive pressure of 17/108 MPa). The shear waves were excited by ARFI focused at the lesion center. The shear-induced temporal displacement profile was measured at a lateral location 10 mm offset to the lesion with M-mode imaging. Results showed significant changes in two characteristics: the peak-to-peak displacement decayed exponentially, and the relative time-to-peak displacement increased and saturated with increasing numbers of histotripsy pulses (N = 6). Correspondingly, the degree of tissues fractionation, as indicated by the percentage of structurally intact cell nuclei, decreased exponentially. Strong linear correlations existed between the two characteristics and the degree of tissue fractionation (R2 > 0.97). These results suggest that characteristics of shear waves induced in a histotripsy lesion may provide useful feedback for treatment outcomes.
View details for DOI 10.1121/1.4830627
View details for PubMedID 24181033