Fig 1.
Raw ultrasound backscatter signals (i.e., radiofrequency signals) and the corresponding envelope signal used to estimate the Nakagami parameter m for modeling the statistical distribution of backscatter envelope R.
Different Nakagami parameters indicate varying envelope statistics caused by various properties of scatterers in the tissue.
Fig 2.
The algorithmic scheme for Nakagami imaging proposed in this study for real-time monitoring RFA.
Compared with the conventional Nakagami image, the new algorithm applies frequency and temporal compounding of Nakagami images for an enhanced visualization of RFA-induced ablation zones.
Fig 3.
Real-time Nakagami imaging system for monitoring RFA.
The proposed algorithm is integrated into a PC-based clinical ultrasound scanner (Terason ultrasound).
Fig 4.
After RFA, the tissue sample was cut along the ultrasound imaging plane for histological observations, and the size of the ablation zone was estimated using ImageJ.
Fig 5.
B-mode, temporal compounding Nakagami , PAX, and tissue section images of RFA-induced ablation zones in porcine liver when the ATL = 0.5 cm (a), 1.0 cm (b), and 1.5 cm (c).
The green crosshair in the B-mode images indicates the location of the RF electrode.
Fig 6.
The relationship between the sizes of the ablation zone in the tissue section measured using ImageJ and the (a) –1, (b) –2, (c) –3, (d) –4, (e) –5, and (f) –6 dB contours in the PAX images (n = 18).
The ablation size estimated using the—6 dB contour in the PAX images had the highest correlation with that measured using the tissue section images (r = 0.941).
Fig 7.
The ablation sizes estimated using the PAX and tissue section images as a function of RF needle length.
The ablation size estimated using the—6 dB contour in the PAX image is the nearest to that measured using ImageJ.
Fig 8.
B-mode, , PAX, and tissue section images of RFA-induced ablation zones in the pork tenderloin when the ATL = 0.5 cm (a), 1.0 cm (b), and 1.5 cm (c).
The results indicated that Nakagami imaging cannot monitor the RFA of muscle fiber tissues.
Fig 9.
H&E stains of the porcine liver and muscle tissue before and after RFA.