What is the difference between a B-ultrasound and a Doppler ultrasound?

Ultrasound is a vibrational wave that travels through mediums such as water or air. The human ear can only perceive sound waves with frequencies between 20 and 20,000 Hertz (vibrations per second).When the frequency exceeds 20,000 Hertz, it becomes inaudible to humans. These imperceptible sound waves are called ultrasound. The following image shows a comparison of the hearing frequency ranges of humans and bats.thecomparison.

An ultrasound examination uses an ultrasound device to emit inaudible ultrasound waves. These waves, acting as a medium, bounce off different organs in the body, producing different echoes. The ultrasound device analyzes these echoes, determining the spatial location of an organ based on the time it takes for the echo to return. The strength of the echo also helps determine whether the characteristics of an organ are normal or abnormal. Through ultrasound, we can observe the internal structures, size, and location of parts of the body that are normally invisible.

Radiation refers to any energy emitted or transmitted through space or a medium in the form of waves or particles. This includes things we use every day: (non-ionizing radiation) visible light, infrared light, microwaves, radio waves, extremely low frequency waves, and heat radiation.

The "radiation" people often worry about actually refers to ionizing radiation: α particles, β particles, neutrons, X-rays, and γ rays. These are high-energy radiations that can remove electrons from atoms, creating ions—a process called ionization. Ions can significantly damage various molecules in the body, including DNA and proteins. This type of radiation is more powerful than non-ionizing radiation.

Ultrasound is a sound wave, not ionizing radiation, and does not cause the same harm as ionizing radiation. The following image shows a comparison of common ionizing and non-ionizing radiation.

Ultrasound has been used clinically for decades, and to date, there is no medical evidence to show that obstetric ultrasound causes any significant, short-term or long-term effects on the fetus.

Therefore, there is no need to worry about ultrasound examinations.

The idea that "color Doppler ultrasound is just a colored B-ultrasound" is incorrect.

In fact, B-ultrasound and color Doppler ultrasound are both different ultrasound examination devices and different ultrasound examination methods. According to the working principle of the ultrasound instrument, ultrasound examinations can be divided into the following four categories:

A-mode:

This method displays tissue characteristics using waveforms, mainly used to measure the diameter of organs to determine their size.

B-mode:

This is what we most commonly refer to as "B-ultrasound." It uses a planar image to display the specific situation of the tissue being examined. During the examination, the reflected signals from the body's interface are first converted into light spots of varying intensity. These light spots can be displayed on a fluorescent screen. This method is intuitive, highly repeatable, and allows for comparison over time. It is therefore widely used in the diagnosis of diseases in the gynecology, obstetrics, urology, digestive, and cardiovascular systems.

D-mode:

This is an ultrasound diagnostic method specifically used to detect blood flow and organ activity. It is also known as Doppler ultrasound, or what we commonly refer to as "color Doppler ultrasound." It can determine whether blood vessels are patent, whether the lumen is narrowed or occluded, and the location of lesions. Newer D-mode ultrasound can also quantitatively measure blood flow in the lumen. In recent years, scientists have developed color-coded Doppler systems that can display the direction of blood flow in different colors under the guidance of anatomical landmarks on echocardiograms, with the depth of color representing the flow rate.