The perfect image quality is dependent on some assumptions of the propagation of ultrasound waves in tissues after generating in an imaging system. These assumptions are important for the developing of optimal ultrasound imaging systems.
A lot of steps can be taken to prevent artifacts and to improve image quality, for example beamforming is used to focus the ultrasound beam, and contrast agents decrease the reflectivity of the undesired interfaces or increase the backscattered echoes from the desired regions.

See also Coded Excitation, Validation and Refraction Artifact, Q-Value, Ultrasound Phantom, Dead Zone, Narrow Bandwidth.

Interventional ultrasound, also known as ultrasonography, encompasses a range of invasive or surgical procedures guided by ultrasound imaging. While its widest application lies in intravascular ultrasound imaging for measuring atherosclerotic plaque, it has proven valuable in various medical fields.
In urology, ultrasound-guided interventions are employed for treatments like high intensity focused ultrasound (HIFU) in prostate conditions. The precise imaging provided by ultrasound aids in targeting the affected area and delivering therapeutic energy effectively.
In intraabdominal conditions, endoscopic ultrasound is frequently utilized. This technique combines ultrasound imaging with an endoscope to visualize and evaluate structures within the gastrointestinal tract, allowing for precise diagnoses and targeted interventions.
Ultrasound-guided procedures play a significant role in several medical specialties, including liver sonography, obstetric and gynecologic ultrasound, and thyroid ultrasound. These procedures involve interventions such as RF thermal ablation or biopsies, which are guided by real-time ultrasound imaging.
For instance, in liver sonography, ultrasound guidance is crucial for performing biopsies or RF thermal ablation, a technique used to treat liver tumors by delivering localized heat to destroy the abnormal tissue. The real-time imaging allows for precise needle placement and monitoring during the procedure.
In obstetric and gynecologic ultrasound, ultrasound-guided procedures, such as biopsies, can be performed to obtain tissue samples for diagnostic purposes. Additionally, ultrasound guidance is valuable during interventions like amniocentesis or fetal blood sampling, enabling accurate and safe procedures.
Thyroid ultrasound procedures often involve ultrasound-guided fine-needle aspiration biopsy (FNAB), which allows for the sampling of thyroid nodules for cytological examination. The ultrasound image helps guide the needle into the targeted area, ensuring accurate sampling and minimizing potential complications.
Overall, ultrasound-guided interventions provide minimally invasive and precise approaches to diagnosis and treatment. The real-time imaging capabilities of ultrasound contribute to enhanced accuracy, safety, and patient outcomes in procedures like biopsies, injections, and drainage.

See also Transurethral Sonography, Endocavitary Echography, and B-Mode Acquisition and Targeting.

A liver sonography is a diagnostic tool to image the liver and adjoining upper abdominal organs such as the gallbladder, spleen, and pancreas. Deeper structures such as liver and pancreas are imaged at a lower frequency 1-6 MHz with lower axial and lateral resolution but greater penetration. The diagnostic capabilities in this area can be limited by gas in the bowel scattering the sound waves.
The application of microbubbles may be useful for detection of liver lesions and for lesion characterization. Some microbubbles have a liver-specific post vascular phase where they appear to be taken up by the reticuloendothelial system (RES). Dynamic contrast enhanced scans in a similar way as with CT or MRI can be used to studying the arterial, venous and tissue phase.
After a bolus injection, early vascular enhancement is seen at around 30sec in arterialized lesions (e.g., hepatocellular carcinomas (HCC), focal nodular hyperplasia (FNH)). Later enhancement is typical of hemangiomas with gradually filling towards the center. In the late phase at around 90sec, HCCs appear as defects against the liver background. Most metastases are relatively hypovascular and so do not show much enhancement and are seen as signal voids in the different phases.
Either with an intermittent imaging technique or by continuous scanning in a nondestructive, low power mode, characteristic time patterns can be used to differentiate lesions.

See also Medical Imaging, B-Mode, High Intensity Focused Ultrasound, Ultrasound Safety and Contrast Medium.

The propagation of high amplitude ultrasound waves is inadequate described by a linear wave equation. Non-linear propagation is to expect if the power levels are high enough to make non-linear effects significant. A non-linear propagation results in the distortion of the transmitted waveforms, resulting in the generation of harmonics of the initial frequency components transmitted by the transducer.
In the near field of ultrasound probes, the occurring diffraction and focusing effects make this process complex. The distortion of a wavefront propagating in a medium in which the compressional phase moves slightly faster than the rarefactional phase, results is the conversion of some wave energy into higher harmonics of the fundamental frequency. The effect increases strongly with increasing wave amplitude.

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'POINT Biomedical was a privately held pharmaceutical company, founded in 1996 to pursue technologies related to imaging and drug delivery. POINT's core technology was based upon an ultrasonically responsive two-layer, biodegradable microsphere or BiSphere™. One of the most important features of this technology is the ability to noninvasively trigger the BiSpheres™ to release their contents at sites within the body using externally generated pulses of ultrasound. From this basic platform, POINT was developing a pipeline of products that leverage the unique properties of the BiSphere™ technology in the areas of imaging and therapeutics. POINT has initially focused development of this platform on the assessment of tissue specific blood flow. The lead product, CARDIOsphere®, is a pharmaceutical agent that will enable cardiologists to perform myocardial perfusion imaging studies in the office setting using ultrasound rather than more expensive and cumbersome nuclear medicine (or radioisotope) techniques.'
'According to BioSpace, Tom Feldman, ex-CEO of Point BioMedical, the company's lead investor, Vendanta Capital has chosen not to follow through with the second half of its $50 million private equity financing. Point BioMedical has withdrawn the new drug application for its molecular imaging agent CARDIOsphere and is liquidating its assets to avoid a formal bankruptcy proceeding in 2008.'