![]() ![]() Very recently, the first acoustic biomolecules for ultrasound, analogous to GFP for optics, were developed based on a unique class of air-filled protein nanostructures called gas vesicles, or GVs, making it possible to use ultrasound to visualize the function of cells deep inside tissues. ![]() In contrast, the physics of ultrasonic waves allow them to propagate centimeters deep into biological tissues without losing their coherence, and enable tissue scanning at the organ scale. However, the microstructure of biological tissues restricts a photon’s transport mean free path to about 1 mm, limiting in vivo optical imaging applications. Green fluorescent protein (GFP) and its analogs serve as irreplaceable tools allowing biologists to visualize gene expression and other cellular processes using optical microscopes. These results advance the physical facet of the emerging field of biomolecular ultrasound, and are also relevant to synthetic ultrasound contrast agents. Finally, we demonstrate that xAM enables highly specific in vivo imaging of GVs located in the gastrointestinal tract, a target of prime interest for future cellular imaging. We demonstrate in tissue-mimicking phantoms that imaging artifacts distal to GV inclusions decrease as the plane-wave cross-propagation angle opens, nearing complete extinction at angles above 16.5 degrees. We show in both simulations and experiments that residual xAM nonlinearity due to wave propagation decreases as the plane-wave cross-propagation angle increases. By transmitting cross-propagating plane-waves, we minimize cumulative nonlinear interaction effects due to collinear wave propagation, while generating a transient wave-amplitude modulation at the two plane-waves’ intersection. The xAM method derives from counter-propagating wave interaction theory which predicts that, in media exhibiting quadratic elastic nonlinearity like biological tissue, the nonlinear interaction of counter-propagating acoustic waves is inefficient. To address this issue, we present an imaging paradigm, cross-amplitude modulation (xAM), which relies on cross-propagating plane-wave transmissions of finite aperture X-waves to achieve quasi artifact-free in vivo imaging of GVs. Unfortunately, the in vivo specificity of AM ultrasound imaging is systematically compromised by the nonlinearity added by the GVs to propagating waves, resulting in strong image artifacts from linear scatterers downstream of GV inclusions. ![]() We previously engineered GVs exhibiting a nonlinear scattering behavior in response to acoustic pressures above 300 kPa, and showed that amplitude-modulated (AM) ultrasound pulse sequences that both excite the linear and nonlinear GV scattering regimes were highly effective at distinguishing GVs from linear scatterers like soft biological tissues. Acoustical methods for the in vivo detection of GVs are now required to maximize the impact of this technology in biology and medicine. The expression of these unique air-filled proteins, known as gas vesicles (GVs), in cells allows ultrasound to image cellular functions such as gene expression in vivo, providing ultrasound with its analog of optical fluorescent proteins. Recently, this capability was enhanced with the development of acoustic biomolecules – proteins with physical properties enabling them to scatter sound. 1) Warranty does Not Cover Damage Caused to the Product Due to Improper Installation by Customer Normal Wear and Tear Caused Due to Use of Product.Ģ) Warranty does Not Cover Any External Accessories to the Product (Such as Battery, Cable, Carrying Bag etc.)ģ) All Plastic, Rubber, Glass, or Aesthetic Parts and Consumable Replacements will be on a Chargeable Basis.Ĥ) All Transportation & Handling Expenses Incurred while Replacing or Repairing will be Payable by the Customer.Ī) The Product is Not Operated as per the Instructions Given in the User Guide, if Any.The basic physics of sound waves enables ultrasound to visualize biological tissues with high spatial and temporal resolution.1) Warranty is Non-transferrable, Valid Only in the Territory of India and Extended Only to the First End User Customer (Customer).Ģ) Warranty will be Valid Only when the Original Purchase Invoice is Presented at the Time of Service.ģ) Warranty will Cover Only Functional Parts and Software Issues having Manufacturing Defects and does Not Cover Damages Resulting from Unauthorised Adaptations/Adjustments/Tampering of the Product, Improper Installation of the Product, Normal Wear and Tear Caused Due to Use of Product.Carry-in, For warranty claims or any product related issues please email at or call: +91-6366043210. ![]()
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