1. Quantification of tumor localization needle displacement prior to tumor excision in navigated lumpectomy
Christina Yan1, Tamas Ungi1, Gabrielle Gauvin2, Doris Jabs3, Andras Lasso1, Jay Engel2, John Rudan2, Gabor Fichtinger1
1 Laboratory for Percutaneous Surgery, School of Computing, Queen’s University, Kingston, ON
2 Department of Surgery, Queen’s University, Kingston ON
3 Department of Radiology, Queen’s University, Kingston ON
Intro
The idea for this project rooted forward to us by surgical oncologists asking for some kind of navigation system to guide lumpectomy procedures.
A needle was used to track the tumor’s position, but we noticed in a few patients that the needle was slipping and losing track of the tumor’s location
Decided to investigate this needle slippage because this can cause inaccurate tumor tracking
Methods
A radiologist looked at 10 pre – operative US and measured the needle slippage relative to tumor margins in the images
Slippage was measured by the change in distance from the needle and tumor boundary (fig 2)
Also looked at the angle at which the needle is inserted into the skin, calculated from the direction vectors of the needle and coronal plane
Used the cosine of this angle to see if gravity affected needle slippage
Results
Avg disp under 2 mm
Max disp was 4.5 mm
Data showed a sig rel btw slippage and insertion angle
Conclusion
Looked at needle slippage in navigated lumpectomy
Results showed that horizontally needles had lower slippage
Going forward, we can refine the clinical workflow or improve the mechanical design of the tumor tracking needle to reduce needle slippage
Introduction
Results
Average needle displacement was 1.7±1.2 mm. It was determined that NCA was significantly correlated (p=0.04) with increased needle displacement. Localization needles inserted pointing towards the operating room ceiling tended to experience greater displacement (Fig 5).
Average time between the first and last in plane image was ±89.3 seconds.
Maximum needle displacement was 4.5 mm.
In breast conserving surgery, a.k.a. lumpectomy, electromagnetic (EM) navigation has been found to be helpful in achieving complete tumor resection without increasing the excised tissue volume (Ungi 2016).
Prior to resection, a tissue locking needle equipped with EM sensor is inserted in the tumor under ultrasound guidance, and the tumor is localized in ultrasound. During resection, through tracking the needle, the tumor is tracked relative to the surgical tool.
Unfortunately, the localization needle may displace, compromising tumor tracking accuracy. We investigated the displacement of the localization needle during ultrasound scanning.
Methods
Data collection
Intra-operative ultrasound scans were collected from 10 patients with non-palpable tumors. Ultrasound scans were evaluated by a physician to quantify needle displacement relative to visible tumor margins.
Quantifying needle displacement
Needle coronal angle (NCA) measurement
The NCA was measured from the direction vectors of the localization needle and the coronal plane (Fig 3), using the first in-plane ultrasound image observed, where the image was parallel with the localization needle (Fig 4).
The cosine of NCA represented the vertical component (anterior- posterior direction relative to the patient in supine position on the operating table), and was used to estimate needle displacement resulting from the mechanical forces associated with the attached electromagnetic sensor.
An experienced radiologist pre-operatively inserted the hooked localization needle (Fig 1), before performing an ultrasound scan to contour a 3D tumor volume to be used in EM navigation.
Figure 1. Localization needle with hooks deployed in green breast tumor.
Figure 5. Scatter plot showing the relationship of needle displacement and needle orientation. Displacement is shown along the needle axis relative to the distal tumor margin, between the beginning and the end of ultrasound scan. Positive direction is towards the needle shaft; negative direction is towards the needle tip.
Conclusion
Tracking needle displacements from EM navigated lumpectomy procedures were measured. A significant relationship was found between vertically inserted localization needles and increased needle displacement.
Results suggest that inserting the localization needle horizontally may reduce needle displacement. Improved clinical workflow and mechanical design of the hooked needle are other areas for improvement that may reduce overall needle displacement.
Needle displacement was measured by the change in distance between the needle tip and tumor margins in the direction of the needle axis (Fig 2).
Figure 2. Distance between needle and tumor boundary .
Reference
Ungi, T., Gauvin, G., Lasso, A., Yeo, C.T., Pezeshki, P., Vaughan, T., Carter, K., Rudan, J., Engel, C.J., Fichtinger, G., “Navigated breast tumor excision using electromagnetically tracked ultrasound and surgical instruments”, IEEE Trans Biomed Eng. 63(3):600-6 (2016).
Open-source platforms used
Figure 3. NCA Measurement.
Figure 4. In-plane measurement.