The beam pattern shows the relative amplitude of the acoustic pressure as a function of direction relative to the transducer. Beam patterns are three-dimensional. The transmit and receive beam patterns are basically the same.

The Bernoulli effect describes the reduction in pressure that occurs with an increase in velocity of fluid flow.

See also Bernoulli Equation, and Maximum Velocity.

Bicycle stress echocardiography can be used instead of treadmill. Bicycle exercise is particularly useful for patients with valvular heart disease or for evaluated pulmonary artery pressures. It is also used as a substitute for treadmill exercise testing when the heart performance at each stage of exercise needs to be assessed and the patient is capable of bicycle exercise. Bicycle stress echocardiography has no additional risk compared to routine exercise.

See also M-Mode Echocardiography.

A bolus is a rapid infusion of high dose contrast agent. Dynamic and accumulation phase imaging can be performed after bolus injection. Since the transit time of the bolus is only a short time, images with high frame rate show the wash in and wash out of the contrast material. The injection rate and the total injected volume modifies the bolus peak profile. Substantial changes in the concentrations during signal acquisition induce artifacts. Furthermore, the hemodynamic parameters (cardiac output, blood pressure) influence the bolus profile. However, the characteristics of ultrasound contrast agents are favorable with a continuous perfusion.

See also Negative Bolus.

Bubble destruction describes the microbubble shell rupture by ultrasound pulses. The bubble destruction increases with increasing peak negative pressure and decreasing frequency. The mechanical index is an indicator for the effectiveness of microbubble destruction. Contrast enhanced ultrasound relies on bubble rupture to detect bubbles in small vessels.

See also Negative Bolus.