Final answer:
Lateral gain is the system control primarily used in cardiac imaging to correct for dropout on the sides of the image.
Step-by-step explanation:
Lateral gain is the system control primarily used in cardiac imaging to correct for dropout on the sides of the image. Lateral gain is a technique that increases the brightness of pixels on the edges of the image, compensating for the loss of signal. This helps to improve the visibility and accuracy of structures, such as the heart, in cardiac imaging. For example, in echocardiography, which is a common method of cardiac imaging, lateral gain can be adjusted to enhance the quality of the images and provide a more comprehensive view of the heart.