Reflux sonography, as an alternative to micturating cystography (MCU), evaluates vesico-ureteral reflux (VUR), a common problem in children. Contrast enhanced pulse-inversion imaging shows best results. During the instillation of an ultrasound contrast agent into the bladder, (as for a conventional MCU) the lower ureters and renal pelves are scanned transabdominally as the bladder is filled to stimulate micturition.
Advantages for reflux sonography are a high sensitivity and the avoidance of X-rays. A disadvantage is the poorer depiction of the posterior urethra. However, for girls and for all follow-up studies, the ultrasound MCU has become standard in many pediatric ultrasound departments.

See also Urologic Ultrasound, Kidney Ultrasound, Ultrasound Safety, Ultrasound Imaging Modes.

The thermal effect of ultrasound is caused by absorption of the ultrasound beam energy. As the ultrasound waves are absorbed, their energy is converted into heat. The higher the frequency, the greater the absorbed dose, converted to heat according the equation: f = 1/T where T is the period as in simple harmonic motion. Ultrasound is a mechanical energy in which a pressure wave travels through tissue. Heat is produced at the transducer surface and also tissue in the depth can be heated as ultrasound is absorbed.
The thermal effect is highest in tissue with a high absorption coefficient, particularly in bone, and is low where there is little absorption. The temperature rise is also dependent on the thermal characteristics of the tissue (conduction of heat and perfusion), the ultrasound intensity and the length of examination time. The intensity is also dependent on the power output and the position of the tissue in the beam profile. The intensity at a particular point can be changed by many of the operator controls, for example power output, mode (B-mode, color flow, spectral Doppler), scan depth, focus, zoom and area of color flow imaging. The transducer face and tissue in contact with the transducer can be heated.

See also Thermal Units Per Hour and Ultrasound Radiation Force.

See also Imagent®.
June 19, 2003
Alliance Pharmaceutical Corporation and Photogen Technologies, Inc. announced that they have closed the previously announced transaction whereby Photogen has acquired all of the assets of Alliance related to medical imaging, including all manufacturing and marketing rights to Imagent (formerly Imavist). Terms of the transaction were not disclosed.

June 03, 2002
Alliance Pharmaceutical Corp. announced that its ultrasound imaging agent, Imagent (perflexane lipid microspheres), has been approved for marketing by the U.S. Food and Drug Administration. The product will be marketed by Alliance in partnership with Cardinal Health, Inc., a provider of products and services to the healthcare industry, and inChord Communications, Inc., an independent healthcare communications company.

March 01, 2002
'Alliance Pharmaceutical Corp. announced that it has entered into a partnership with Bayer Schering Pharma AG, Germany and Cardinal Health Inc. for the marketing of Imavist (perflexane lipid microspheres), an ultrasound contrast agent. Schering licensed worldwide marketing rights for Imavist from Alliance in September 1997. The companies have agreed to modify this agreement to allow Alliance to increase its participation in the marketing of the product. Under the terms of the modified agreement, Alliance will have exclusive marketing rights to Imavist for cardiology indications in the U.S. for five years, and Schering will receive a royalty on product sales. Schering retains marketing rights for other indications in the U.S. and all indications in the rest of the world, subject to Alliance's option to obtain additional indications and territories. Under certain circumstances, Schering would co-market the product at the end of five years. Concurrently, Alliance has entered into a five-year exclusive agreement with Cardinal Health Inc., a provider of products and services to the health-care industry, to assist in the marketing of Imavist.'

October 08, 2001
'Alliance Pharmaceutical Corp. announced a clinical study to take place at Thomas Jefferson University Hospital, Philadelphia, using Alliance's Imavist (AF0150) contrast agent with ultrasound imaging to improve detection of prostate cancer. The study, which will involve 300 adult men with suspected prostate cancer, is being funded by the U.S. Department of Defense under a competitive grant awarded to Thomas Jefferson University for investigators at Jefferson's Prostate Center. Imavist is being developed jointly by Alliance and Bayer Schering Pharma AG Germany, and is awaiting final approval from the U.S. Food and Drug Administration.'

August 21, 2000
Alliance Pharmaceutical Corp. announced that it has received a letter from the U.S. Food and Drug Administration (FDA) stating that the FDA has completed its review of the New Drug Application (NDA) for Imagent (AF0150), and found it to be approvable. Imagent, an ultrasound contrast agent, is being developed jointly by Alliance and Bayer Schering Pharma AG, Germany

Notes:
The manufacturer is pursuing additional radiology indications such as ultrasound imaging of the prostate and liver, and clinical trials are currently being conducted to evaluate Imagent in conjunction with ultrasound imaging for use in the detection of prostate cancer. During the course of its development, the brand name for this product has changed from Imagent to Imavist back to Imagent. Initially reported on by the manufacturer as Imagent and then, between August 2000 and March 2002, as 'Imavist (formerly Imagent).' The manufacturer's 06/03/02 press release announcing FDA approval refers to the product as 'Imagent (formerly Imavist),' and the approval notice and monograph posted at the FDA site refers to the product as Imagent. Jointly developed by Alliance Pharmaceutical Corp and Bayer Schering Pharma AG, (Germany). Source: PR Newswire - 10/10/96, 03/31/98, 10/13/99, 03/13/01, 10/08/01; FDA approvals - 05/31/02; Alliance Pharmaceutical press release - 06/03/02.

(ESWL) Extracorporeal shock wave lithotripsy is a special use of kidney ultrasound, where high intensity focused ultrasound pulses are used to break up calcified stones in the kidney, bladder, or urethra. Pulses of sonic waves pulverize dense renal stones, which are then more easily passed through the ureter and out of the body in the urine. The ultrasound energy at high acoustic power levels is focused to a point exactly on the stone requiring an ultrasound scanning gel for maximum acoustic transmission.
Air bubbles in the ultrasound couplant, regardless of their size, degrade the performance of Lithotripsy and have the following effect:
Air bubbles smaller that 1/4 wavelength cause scattering of the sound waves as omni directional scatterers and less acoustic energy reaches the focal point. The result is less acoustic power at the focal point to disintegrate the kidney stone.
Air bubbles larger than 1/4 wavelength act as reflectors and deflects the acoustic energy off in a different direction. These results in less acoustic energy at the focal point.
Microbubbles dispersed throughout the ultrasound couplant layer change the average acoustic impedance of the gel layer (which reduces the total transmitted energy) and, due to refraction, change the focal point.

Targeted ultrasound contrast agents provide advantages compared with usual microbubble blood pool agents. The goal of targeted ultrasound contrast agents is to significantly and selectively enhance the detection of a targeted vascular site. Tissue-specific ultrasound contrast agents improve the image contrast resolution through differential uptake. Targeted drug delivery via contrast microbubbles is another contrast media concept and provides the potential for earlier detection and characterization of disease.
Targeted contrast imaging provides a higher sensitivity and specificity than obtained with a nontargeted contrast agent.
The detection of disease-indicative molecular signatures may allow early assessment of pathology on a molecular level.
Molecular imaging should be an efficient and less invasive technique to obtain three-dimensional localization of pathology.
Ultrasound agents typically remain within the vascular space, and therefore possible targets include molecular markers on thrombus, endothelial cells, and leukocytes. Targeted contrast agents permit noninvasive detection of thrombus, cancer, inflammation, or other sites where specific integrins or other adhesion molecules are expressed. Adhesion molecules such as monoclonal antibodies, peptides, asialoglycoproteins, or polysaccharides are incorporated into the shell of the microbubble or liposome. After injection into the bloodstream, the targeted agent accumulates via adhesion receptors at the affected site, enhancing detection with an ultrasound system.

See also Acoustically Active Lipospheres, and Tissue-Specific Ultrasound Contrast Agent.