What is grating lobe artifact?
Side lobes and grating lobes are both unwanted parts of the ultrasound beam emitted off axis that. produce image artifacts due to error in positioning the returning echo.
What causes ultrasound grating lobes?
Grating lobes are an artifact generated as a result of undersampling of the spatial frequencies in the transmitted and received ultrasound beams, and depend on the transmitted wavelength and the element size and spacing24.
What is the difference between side lobe artifact and grating lobe artifact?
Side Lobes are created by each individual piezoelectric crystal. Grating Lobes are formed from multiple crystals. Strong reflectors in the line of sight of these off-axis lobes will be reflected echoes back to transducer and displayed on the monitor.
What is the difference between side lobes and grating lobes?
Side lobes are always present in an ultrasonic sound field. They are only troublesome when they are strong enough to produce indications of significant amplitude to look like a defect indication. 2. Grating lobes are caused by the periodic spacing of individual array elements in an ultrasonic sensor.
How do you fix grating lobes?
Thus the simplest way to minimize grating lobes in a given application is to use a transducer with a small pitch. Specialized transducer design incorporating subdicing (cutting elements into smaller elements) and varying element spacing will also reduce unwanted lobes.
What causes side lobe artifact?
Side lobe artifacts occur where side lobes reflect sound from a strong reflector that is outside of the central beam, and where the echoes are displayed as if they originated from within the central beam.
What do you mean by grating lobes how can they be suppressed?
In antenna arrays inter-element spacing with lambda or more creates grating lobes. Pseudo suppression of these lobes is possible by decreasing the inter-element spacing along with optimization of feed excitations; however, this increases the main-lobe beam-width.
Why do artifacts occur in ultrasound?
Artifacts are any alterations in the image which do not represent an actual image of the examined area. They may be produced by technical imaging errors or result from the complex interaction of the ultrasound with biological tissues. Reverberation artifacts appear as a series of equally spaced lines.
What is beam squint?
Beam squint is an unfocusing of the antenna across frequency when we use phase shift, instead of a true time delay, to steer the beam. We’ll also discuss the trade-off between these two steering methods and understand the impact of beam squint on typical systems.
What are 3 artifacts produced during ultrasound?
Reverberation, Comet Tail, and Ring-Down Reverberation artifacts arise from multiple echoes generated between highly reflective and parallel structures that interact at a perpendicular angle to the ultrasound beam.
What does artifact mean on ultrasound?
Artifacts are any alterations in the image which do not represent an actual image of the examined area. They may be produced by technical imaging errors or result from the complex interaction of the ultrasound with biological tissues. REVERBERATION. Reverberation artifacts appear as a series of equally spaced lines.
What is grating lobe in antenna?
Definition. In antenna or transducer arrays, a grating lobe is defined as “a lobe other than the main lobe, produced by an array antenna when the inter-element spacing is sufficiently large to permit the in-phase addition of radiated fields in more than one direction.”
What is angle of squint?
The “angle” of deviation, or the “angle” of squint is usually defined as the angle between the visual axis of the fixating eye and the visual axis of the deviating eye. This definition is approximately correct numerically only for horizontal deviations measured at 6 meters.
What is a side lobe in ultrasound?
Abstract. Transducer side lobes consist of multiple low-intensity sound beams located outside of the main ultrasound beam. Although the echoes generated by side lobes originate outside of the main beam, they appear as specular or diffuse artifactual echoes within the beam.
What causes artifact on ultrasound?
US artifacts arise secondary to errors inherent to the ultrasound beam characteristics, the presence of multiple echo paths, velocity errors, and attenuation errors.
What is the significance of grating lobes?
Grating lobes are the maxima of the main beam, as predicted by the pattern multiplication theorem. When the array spacing is less than or equal to λ / 2 , only the main lobe exists in the visible space, with no other grating lobes. Grating lobes appear when the array spacing is greater than λ / 2 .