Table 3.
Summary of techniques for liver fat quantification and their mechanisms
|
Technique
|
Mechanism for liver fat quantification
|
Principle of the techniques
|
| CAP | Spectral based technique (AC) | CAP measures the attenuation of or reduction in the amplitude of the ultrasound waves on their way through the liver |
| ATI | Spectral based technique (AC) | ATI quantifies the degree of the ultrasound beam attenuation. The attenuation of the ultrasound beam is calculated by analyzing echo signals received by the transducer |
| ATT | Spectral based technique (AC) | Two ultrasonic waves of different frequencies (F0, F1; F0 < F1) are transmitted to the same beamline and the received signal is obtained. ATT estimates the attenuation coefficient it by calculating the slope of the received signal ratio (F0/F1) |
| UGAP | Spectral based technique (AC) | UGAP compares the measured liver signal and the referential signal (measured on the reference phantom with known attenuation and backscatter coefficients) |
| Att. PLUS | Spectral based technique (AC) | Att. PLUS measures the decrease in amplitude of ultrasound waves as they propagate throughout the tissue |
| TAI | Spectral based technique (AC) | TAI is determined based on the attenuation properties of different frequency components in the tissue, and the spectrum of radiofrequency signals provides a downshift of the center frequency according to depth. The TAI parameter indicates the slope of the ultrasound center frequency downshift |
| BSC | Spectral based technique (BSC) | BSC measures the ultrasound energy returned from the tissue |
| UDFF | Spectral based technique (BSC) | UDFF is obtained by combining both AC and BSC and the result is presented as the percentage of hepatic steatosis. Reference phantom data is integrated into the ultrasound system and fixed-acquisition region of interest is applied |
| TSI | Envelope Statistic based technique | The TSI is based on the shape parameter of the Nakagami distribution which reflects the local concentration and arrangement of ultrasound scatterers |
| ASQ | Envelope Statistic based technique | ASQ measures the FD ratio, which is based on the difference between theoretical and real echo amplitude distributions |
| NLV | Envelope Statistic based technique | NLV parameter was derived from ASQ, which analyzed ultrasound amplitudes sampled from gray-scale ultrasound images |
| SS | Envelope Statistic based technique | SS calculates the speed of sound through the liver |
| SSp.PLUS | Envelope Statistic based technique | SSp.PLUS is a novel technique that allows quantification of the intrahepatic speed of sound which is correlated with the liver fat content |
AC: Attenuation coefficient; BSC: Backscatter coefficient; CAP: Controlled attenuation parameter; ATI: Attenuation imaging; ATT: Attenuation measurement function; UGAP: Ultrasound-guided attenuation parameter; Att.PLUS: Attenuation plane-wave ultrasound; TAI: Tissue attenuation imaging; UDFF: Ultrasound-derived fat fraction; TSI: Tissue scatter distribution imaging; ASQ: Acoustic structure quantification; NLV: Normalized local variance; SS: Speed of sound; SSp.PLUS: Sound speed plane-wave ultrasound; FD: Focal disturbance.