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Safety margin assessment after microwave ablation of liver tumors: inter- and intrareader variability

Jan Schaible
Jan Schaible
, 
Benedikt Pregler
Benedikt Pregler
, 
Wolf Bäumler
Wolf Bäumler
, 
Ingo Einspieler
Ingo Einspieler
, 
Ernst-Michael Jung
Ernst-Michael Jung
, 
Christian Stroszczynski
Christian Stroszczynski
 e 
Lukas Philipp Beyer
Lukas Philipp Beyer
   | 12 feb 2020
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Article Category: Research Article
Pubblicato online: 12 feb 2020
Pagine: 57 - 61
Ricevuto: 16 set 2019
Accettato: 10 gen 2020
DOI: https://doi.org/10.2478/raon-2020-0004
© 2020 Jan Schaible, Benedikt Pregler, Wolf Bäumler, Ingo Einspieler, Ernst-Michael Jung, Christian Stroszczynski, Lukas Philipp Beyer, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

(A) Pre-interventional arterial phase in which the tumor is almost invisible. This not only complicates ablation but also post-interventional detection of residual tumor tissue. (B) The result immediately postinterventionally with a corresponding ablation defect. (C) Axial and (D) coronal show the situation one day postinterventionally. Due to the different breathing position, the tumor was more peripheral the day before, whereas on the following day healthy liver tissue around the ablation defect is visible. Measuring the safety distance is particularly difficult in these cases.
(A) Pre-interventional arterial phase in which the tumor is almost invisible. This not only complicates ablation but also post-interventional detection of residual tumor tissue. (B) The result immediately postinterventionally with a corresponding ablation defect. (C) Axial and (D) coronal show the situation one day postinterventionally. Due to the different breathing position, the tumor was more peripheral the day before, whereas on the following day healthy liver tissue around the ablation defect is visible. Measuring the safety distance is particularly difficult in these cases.

Figure 2

Bland-Altman plots: intra- (A) and inter-reader (B) = reader 1 vs. reader 2, (C) = reader 2 vs. reader 3, (D) = reader 1 vs. 3) agreement for minimum safety margin measurements. The middle line shows the mean percentage difference in measurements and the dashed lines above and below show the 95% reference range. Measurements within the 95% reference range can be considered as intrinsic measurement errors (or variations) that are associated with the given measurement tools and imaging techniques. Therefore, a narrower reference range indicates a lower measurement error/variation.
Bland-Altman plots: intra- (A) and inter-reader (B) = reader 1 vs. reader 2, (C) = reader 2 vs. reader 3, (D) = reader 1 vs. 3) agreement for minimum safety margin measurements. The middle line shows the mean percentage difference in measurements and the dashed lines above and below show the 95% reference range. Measurements within the 95% reference range can be considered as intrinsic measurement errors (or variations) that are associated with the given measurement tools and imaging techniques. Therefore, a narrower reference range indicates a lower measurement error/variation.

Figure 3

The HCC in segment VIII (A) was pre-interventionally localized using landmarks such as metal clips (arrow) and anatomical landmarks like the kidney (arrow) (B). Post-interventionally, the same landmarks are used and the target area is localized by distance measurements (dashed lines) from different angles (C). The MRI follow-up after 6 weeks confirmed complete ablation (D).
The HCC in segment VIII (A) was pre-interventionally localized using landmarks such as metal clips (arrow) and anatomical landmarks like the kidney (arrow) (B). Post-interventionally, the same landmarks are used and the target area is localized by distance measurements (dashed lines) from different angles (C). The MRI follow-up after 6 weeks confirmed complete ablation (D).

Figure 4

Metastasis was best seen in the portal venous phase (B). In this case, clips after hemihepatectomy serve as orientation. A line is drawn (solid line) and the distance (dashed line) is measured by means of a clip at an angle of 90 degrees. The same fixed points are used postinterventionally. This already shows only a small safety distance in the peripheral area. In the 6 weeks follow-up MRI residual tumor tissue (circle) was detected.
Metastasis was best seen in the portal venous phase (B). In this case, clips after hemihepatectomy serve as orientation. A line is drawn (solid line) and the distance (dashed line) is measured by means of a clip at an angle of 90 degrees. The same fixed points are used postinterventionally. This already shows only a small safety distance in the peripheral area. In the 6 weeks follow-up MRI residual tumor tissue (circle) was detected.

Contingency table of all the three independent readings compared with the six weeks follow-up MRI as gold standard

Incomplete (6 weeks MRI)Complete (6 weeks MRI)
Reader 1
Incomplete23
Complete441
Reader 2
Incomplete18
Complete536
Reader 3
Incomplete58
Complete136

Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the three independent readings (R 1, 2, 3)) compared with the six weeks follow-up MRI as gold standard

R 1R 2R 3
Sensitivity93%82 %82 %
Specificity33%17 %83 %
PPV91 %88 %97 %
NPV40 %10 %39%

Baseline characteristics

Number of patientsN = 58
Age
   mean (years)62.84 (10.85)
   range (years)36–83
Gender
   male (%)53 (91)
Ablation method (%)
   microwave ablation58 (100)
Liver segments
   I3 (5)
   II4 (7)
   III6 (10)
   IVa7 (12)
   IVb3 (5)
   V7 (12)
   VI4 (7)
   VII12 (21)
   VIII9 (16)
Tumor entity
   Hepatocellular carcinoma46 (79)
   Metastasis colorectal cancer9 (16)
   Metastasis pancreatic cancer3 (5)
eISSN:
1581-3207
Lingua:
Inglese
Frequenza di pubblicazione:
4 volte all'anno
Argomenti della rivista:
Medicine, Clinical Medicine, Radiology, Internal Medicine, Haematology, Oncology
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