The main advantage of ultrasound is that certain structures can be observed without using radiation. However, ultrasound is energy and there are ultrasound safety regulations, because two bioeffects of ultrasound are heat and cavitation. Ultrasound is a mechanical energy in which a pressure wave travels through tissue. Reflection and scattering back to the transducer are used to form the image. As sound energy is transmitted through the tissue, some energy is reflected and some power is absorbed.
Possible physical effects with ultrasound:
The ultrasound safety is based on two indices, the mechanical index (MI) and the thermal index (TI). The WFUMB guidelines state that ultrasound that produces temperature rises of less than 1.5°C may be used without reservation. They also state that ultrasonic exposure causing temperature rises of greater than 4°C for over 5 min should be considered potentially hazardous. This leaves a wide range of temperature increases which are within the capability of diagnostic ultrasound equipment to produce and for which no time limits are recommended. However, it has not been determined that medical ultrasound causes any adverse reaction or deleterious effect.
The American Institute of Ultrasound in Medicine states that as of 1982, no independently confirmed significant biologic effects had been observed in mammalian tissue below (medical usage) 100mW/cm2.

See also Ultrasound Regulations and Ultrasound Radiation Force.

Ultrasound machines, with their various components and types, have revolutionized the field of medical imaging. These devices enable healthcare professionals to visualize internal structures, assess conditions, and guide interventions with real-time imaging capabilities. Today, medical ultrasound systems are complex signal processing machines. Assessing the performance of an ultrasound system requires understanding the relationships between the characteristics of the system, such as the point spread function, temporal resolution, and the quality of images. Image quality aspects include the detail resolution, contrast resolution and penetration. Systems with microbubble scanner modification are particularly suitable for contrast enhanced ultrasound.


In summary, ultrasound machines have diverse performance levels and corresponding price ranges, catering to various medical imaging needs. From low-performance systems with basic imaging capabilities to high-performance and premium systems with advanced features, ultrasound technology continues to advance healthcare imaging capabilities.
See also Ultrasound Physics, Handheld Ultrasound, Environmental Protection, Equipment Preparation.

Ultrasound technology with its advancements is vital for delivering high-quality patient care. Innovations including high-frequency ultrasound, 3D//4D imaging, contrast enhanced ultrasound, elastography, and point-of-care ultrasound, have expanded the capabilities of ultrasound imaging and improved diagnostic accuracy.
B-Mode imaging, also known as brightness mode, is the fundamental technique in ultrasound imaging. It produces two-dimensional images based on the echoes received from tissues and organs. Understanding the principles of B-Mode imaging, such as gain adjustment, depth control, and image optimization, is crucial for obtaining diagnostically valuable images. M-Mode imaging, on the other hand, allows for the visualization of motion over time, enabling assessment of cardiac structures and function, as well as fetal heart rate.
High-frequency ultrasound refers to the use of ultrasound waves with frequencies greater than 10 MHz. This technology enables improved resolution, allowing for detailed imaging of superficial structures like skin, tendons, and small organs. High-frequency ultrasound has found applications in dermatology, ophthalmology, and musculoskeletal imaging.
Traditional 2D ultrasound has been augmented by the advent of 3D ultrasound technology. By acquiring multiple 2D images from different angles, this technique construct a volumetric representation of the imaged area. The addition of 4D ultrasound in real-time motion adds further value by capturing dynamic processes.
Doppler imaging employs the Doppler effect to evaluate blood flow within vessels and assess hemodynamics. Color Doppler assigns color to different blood flow velocities, providing a visual representation of blood flow direction and speed. Spectral Doppler displays blood flow velocities as a waveform, allowing for detailed analysis of flow patterns, resistance, and stenosis.
Contrast enhanced ultrasound employs microbubble contrast agents to enhance the visualization of blood flow and tissue perfusion. By injecting these agents intravenously, sonographers can differentiate between vascular structures and lesions. Elastography is a technique that measures tissue elasticity or stiffness. It assists in differentiating between normal and abnormal tissues, aiding in the diagnosis of various conditions such as liver fibrosis, breast lesions, and thyroid nodules.
Fusion imaging combines ultrasound with other imaging modalities, such as computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET). By overlaying or merging ultrasound images with those obtained from other modalities, the user can precisely locate and characterize abnormalities, guide interventions, and improve diagnostic accuracy. Fusion imaging has proven particularly useful in areas such as interventional radiology, oncology, and urology.
See also Equipment Preparation, Environmental Protection, Handheld Ultrasound, Portable Ultrasound and Ultrasound Accessories and Supplies.