Novel Device for Targeting Tumors in Laparoscopic Radiofrequency Ablation: A Learning Curve Study

William J Brown, MS1, Maria A Cassera, BS2, Zeljka Jutric, MD2, Paul D Hansen, MD2, Chet W Hammill, MD, MS, MCR2. 1Meharry Medical College, 2Providence Cancer Center

Introduction:

Precise needle placement within the liver is essential during hepatic ablation procedures.Tumor targeting is typically performed under ultrasound guidance, however, this can be challenging. A novel 3-D guidance system, has been developed to aid in accurate needle placement during ablation.

Methods:

Five novices and five experienced hepatobiliary surgeons were recruited for participation. Using an agar block with a strategically placed analog tumor, participants targeted the tumor under four controlled conditions: in-line with the ultrasound plane (0 degrees off-axis) using ultrasound alone, in-line with the ultrasound plane using 3-D guidance, off-axis to the ultrasound plane (45 degrees off-axis) using ultrasound alone, and off-axis to the ultrasound plane using 3-D guidance. Time to target the tumor, the number of withdrawals required to accurately target the center of the tumor, and the National Aeronautics and Space Administration Task Load Index (NASA-TLX) were collected. The NASA-TLX is an established tool for measurement of mental workload.Initial and final parameters for each of the four conditions were compared using a within-subjects paired t-test.

Results:

Results for mean time to target tumor, mean number of withdrawals, and mean NASA-TLX score are reported in Table 1. A significant reduction was seen in the number of required withdrawals in all situations when using the 3-D guidance. Mental workload was similar initially, but was significantly lower using 3-D guidance after proficiency was achieved. The only difference in targeting time was in the initial trials when approaching the target from 45 degrees off-axis.

Conclusion:

Although 3-D guidance did not reduce targeting time substantially, it did reduce the number of required withdrawals, potentially decreasing complications and decreased mental workload after proficiency was achieved.

In Line (0 degrees off-axis) First Trial p-value Last Trial p-value

Mean Time(seconds):

Ultrasound Guidance

3-D Guidance

117.4

71.2

0.234

93.5

55.8

0.412

Mean Number of Withdrawals:

Ultrasound Guidance

3-D Guidance

4.6

1.1

0.003

4.1

0.1

0.009

Mean Mental Workload Score:

Ultrasound Guidance

3-D Guidance

48.7

42.7

0.213

47.3

24.3

0.017

Out of Line (45 degrees off-axis) First Trial p-value Last Trial p-value

Mean Time(seconds):

Ultrasound Guidance

3-D Guidance

82.5

31.2

0.031

129.2

17.8

0.158

Mean Number of Withdrawals:

Ultrasound Guidance

3-D Guidance

2.2

0.6

0.003

5.9

0.1

0.009

Mean Mental Workload Score:

Ultrasound Guidance

3-D Guidance

48.6

34.5

0.054

49.3

20.4

0.0002

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