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Monitoring radiofrequency ablation using real-time ultrasound Nakagami imaging combined with frequency and temporal compounding techniques.

Zhou Z, Wu S, Wang CY, Ma HY, Lin CC, Tsui PH - PLoS ONE (2015)

Bottom Line: The experimental results showed that the proposed algorithm can operate on a standard clinical ultrasound scanner to monitor RFA in real time.The Nakagami imaging system effectively monitors RFA-induced ablation zones in liver tissues.In the future, real-time Nakagami imaging should be focused on the RFA of the liver and is suggested as an alternative monitoring tool when advanced elastography is unavailable or substantial bubbles exist in the ablation zone.

View Article: PubMed Central - PubMed

Affiliation: College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China.

ABSTRACT
Gas bubbles induced during the radiofrequency ablation (RFA) of tissues can affect the detection of ablation zones (necrosis zone or thermal lesion) during ultrasound elastography. To resolve this problem, our previous study proposed ultrasound Nakagami imaging for detecting thermal-induced bubble formation to evaluate ablation zones. To prepare for future applications, this study (i) created a novel algorithmic scheme based on the frequency and temporal compounding of Nakagami imaging for enhanced ablation zone visualization, (ii) integrated the proposed algorithm into a clinical scanner to develop a real-time Nakagami imaging system for monitoring RFA, and (iii) investigated the applicability of Nakagami imaging to various types of tissues. The performance of the real-time Nakagami imaging system in visualizing RFA-induced ablation zones was validated by measuring porcine liver (n = 18) and muscle tissues (n = 6). The experimental results showed that the proposed algorithm can operate on a standard clinical ultrasound scanner to monitor RFA in real time. The Nakagami imaging system effectively monitors RFA-induced ablation zones in liver tissues. However, because tissue properties differ, the system cannot visualize ablation zones in muscle fibers. In the future, real-time Nakagami imaging should be focused on the RFA of the liver and is suggested as an alternative monitoring tool when advanced elastography is unavailable or substantial bubbles exist in the ablation zone.

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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).
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pone.0118030.g006: 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).

Mentions: Fig. 5 depicts the B-mode, temporal compounding Nakagami , PAX, and tissue section images of in vitro RFA-induced ablation zones in porcine liver when the ATL was 0.5, 1.0, and 1.5 cm. The green crosshair in the B-mode image indicates the location of the RF electrode. The yellow contour in the tissue section image was generated using the ImageJ software and indicates the ablative margin. A strong shadowing effect occurred on the RFA-induced lesion, and thus, using the B-mode image to describe the ablation zone was difficult. By contrast, the image was markedly less affected by the shadow effect when the ablation zone was characterized. In particular, using the PAX image based on the enabled effectively visualizing the change in the backscattered statistics and estimating the ablation zone. Fig. 6 shows the relationship between the sizes of the ablation zone estimated using the tissue section measured in ImageJ and those estimated using the -1, -2, -3, -4, -5, and -6 dB contours of the PAX images (n = 18). The ablation size estimated according to the -6 dB contour in the PAX images had the highest correlation with that measured from tissue section images (r = 0.941). To confirm this observation, we further examined the ablation sizes estimated using the PAX and tissue section images as a function of RF needle length, as shown in Fig. 7. The ablation size estimated using the—6 dB contour in the PAX image was the nearest to that measured in ImageJ. Fig. 8 shows the B-mode, , PAX, and tissue section images of RFA-induced ablation zones in the pork tenderloin in vitro when the ATL was 0.5, 1.0, and 1.5 cm. The results indicated that Nakagami imaging was unable to monitor the RFA of muscle fiber tissues. Fig. 9 depicts the H&E stained images before and after RFA of the liver and muscle tissues. Apparently, the cell structures and sizes in the liver and muscle tissues differed. The Discussion section uses Fig. 9 to discuss the reason that the ultrasound Nakagami imaging operated differently when monitoring the liver and muscle tissues.


Monitoring radiofrequency ablation using real-time ultrasound Nakagami imaging combined with frequency and temporal compounding techniques.

Zhou Z, Wu S, Wang CY, Ma HY, Lin CC, Tsui PH - PLoS ONE (2015)

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).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4320093&req=5

pone.0118030.g006: 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).
Mentions: Fig. 5 depicts the B-mode, temporal compounding Nakagami , PAX, and tissue section images of in vitro RFA-induced ablation zones in porcine liver when the ATL was 0.5, 1.0, and 1.5 cm. The green crosshair in the B-mode image indicates the location of the RF electrode. The yellow contour in the tissue section image was generated using the ImageJ software and indicates the ablative margin. A strong shadowing effect occurred on the RFA-induced lesion, and thus, using the B-mode image to describe the ablation zone was difficult. By contrast, the image was markedly less affected by the shadow effect when the ablation zone was characterized. In particular, using the PAX image based on the enabled effectively visualizing the change in the backscattered statistics and estimating the ablation zone. Fig. 6 shows the relationship between the sizes of the ablation zone estimated using the tissue section measured in ImageJ and those estimated using the -1, -2, -3, -4, -5, and -6 dB contours of the PAX images (n = 18). The ablation size estimated according to the -6 dB contour in the PAX images had the highest correlation with that measured from tissue section images (r = 0.941). To confirm this observation, we further examined the ablation sizes estimated using the PAX and tissue section images as a function of RF needle length, as shown in Fig. 7. The ablation size estimated using the—6 dB contour in the PAX image was the nearest to that measured in ImageJ. Fig. 8 shows the B-mode, , PAX, and tissue section images of RFA-induced ablation zones in the pork tenderloin in vitro when the ATL was 0.5, 1.0, and 1.5 cm. The results indicated that Nakagami imaging was unable to monitor the RFA of muscle fiber tissues. Fig. 9 depicts the H&E stained images before and after RFA of the liver and muscle tissues. Apparently, the cell structures and sizes in the liver and muscle tissues differed. The Discussion section uses Fig. 9 to discuss the reason that the ultrasound Nakagami imaging operated differently when monitoring the liver and muscle tissues.

Bottom Line: The experimental results showed that the proposed algorithm can operate on a standard clinical ultrasound scanner to monitor RFA in real time.The Nakagami imaging system effectively monitors RFA-induced ablation zones in liver tissues.In the future, real-time Nakagami imaging should be focused on the RFA of the liver and is suggested as an alternative monitoring tool when advanced elastography is unavailable or substantial bubbles exist in the ablation zone.

View Article: PubMed Central - PubMed

Affiliation: College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China.

ABSTRACT
Gas bubbles induced during the radiofrequency ablation (RFA) of tissues can affect the detection of ablation zones (necrosis zone or thermal lesion) during ultrasound elastography. To resolve this problem, our previous study proposed ultrasound Nakagami imaging for detecting thermal-induced bubble formation to evaluate ablation zones. To prepare for future applications, this study (i) created a novel algorithmic scheme based on the frequency and temporal compounding of Nakagami imaging for enhanced ablation zone visualization, (ii) integrated the proposed algorithm into a clinical scanner to develop a real-time Nakagami imaging system for monitoring RFA, and (iii) investigated the applicability of Nakagami imaging to various types of tissues. The performance of the real-time Nakagami imaging system in visualizing RFA-induced ablation zones was validated by measuring porcine liver (n = 18) and muscle tissues (n = 6). The experimental results showed that the proposed algorithm can operate on a standard clinical ultrasound scanner to monitor RFA in real time. The Nakagami imaging system effectively monitors RFA-induced ablation zones in liver tissues. However, because tissue properties differ, the system cannot visualize ablation zones in muscle fibers. In the future, real-time Nakagami imaging should be focused on the RFA of the liver and is suggested as an alternative monitoring tool when advanced elastography is unavailable or substantial bubbles exist in the ablation zone.

Show MeSH
Related in: MedlinePlus