A Simple Scanner Control Technique for Device Localization during MRI-Guided Percutaneous Procedures
Matthew Alexander MacDonald1,2, Adam C. Waspe3,4, Joao Amaral3,4, and Samuel Pichardo1,2

1Electrical Engineering, Lakehead University, Thunder Bay, ON, Canada, 2Thunder Bay Regional Research Institute, Thunder Bay, ON, Canada, 3Medical Imaging, University of Toronto, Toronto, ON, Canada, 4Hospital for Sick Children, Toronto, ON, Canada


An experiment demonstrates a simple technique for a clinician operator to interactively align scan planes to an interventional device within the scan room during an MRI guided procedure. Input is collected using foot pedal switches to select axial/device intersection points to specify a virtual line of best fit about which auxiliary views are aligned automatically. Volunteer operators position a biopsy needle within an ex vivo porcine specimen while interactively tracking the needle position and measurements are taken to assess the technique's efficiency.


MR Interventionalists and researchers interested in interactive MRI-guidance of percutaneous procedures.


MRI guided percutaneous interventions performed inside closed-bore MRI scanners can be performed with freehand device placement methods, which are conducted in real time during rapid image acquisition[1]. Here, we demonstrate how a clinician operator can simultaneously align multiple dynamic scan planes to an interventional device. This is done using foot pedal inputs to highlight device/axial plane intersection points that define a virtual line of best fit about which auxiliary dynamic scan planes are automatically oriented.


Trials were conducted with the experimental setup illustrated in Figure 1 using a 3T Philips Achieva MRI, an 11 gauge titanium biopsy needle, an ex-vivo porcine hind limb specimen, and an MR safe projector unit (MRA Inc., Washington, PA). Operator input was collected using foot-pedal optical switches constructed with plastic and brass to interrupt a 5mW 650nm multi-mode fiber-optic circuit interfaced with an external control PC. A GUI application was written in the Python computer language to control the scanner according to operator input using the MatMRI software toolbox[2]. This application was also used to display a visualization of the procedure inside the scan room using the connected projector. MR parameters for the dynamic images were: FOV = 300×300mm² resolution = 3×3×7mm³, TE/TR = 2.1ms/78ms, flip angle = 70°, acquisition matrix = 100×99, ETL = 11, reconstruction matrix = 112, NEX = 1, image frame time = 701ms. Volunteer operators (N=3) manually guided the biopsy needle tip from an externally marked entry site at the anterior leg to a target planted within the anterior thigh marked with a 1ml vile of gadoteridol (0.32mmol/L). Final needle tip distance from the target and scan plane alignment was verified using a T1-weighted 3D acquisition, FOV = 300×300×338mm³, resolution = 2.5×2.5×5mm³, TE/TR = 2.3ms/3.3ms, flip angle = 7°, acquisition matrix = 120×120, reconstruction matrix = 480, ETL = 1,NEX = 4.


Figure 2 shows verification of the needle tip in contact with the target as occurred in two out of three trials for an average tip to target distance of 4.73mm. Average plane misalignment was 5.36° between horizontal and vertical axes. The average completion time was 11 minutes and 58 seconds. Figure 3 shows an example screen-shot of real time dynamic image display. A device/axial plane intersection point is highlighted within the GUI in the primary (left) view and also shown are the automatically aligned views (center and right) showing the needle tip contacting the contrast enhanced target.

Discussion and Conclusions

Figure 4 shows a volunteer operator successfully aligning scan planes to an instrument using the proposed hands-free technique without having to deviate sight from inside the scanner bore. This set-up offers efficient interactive image plane control capabilities accessible with an array of only four input foot switches. Future study will focus on expanding this method to incorporate device motion information and further simplify operator input.


Authors acknowledge support from the Discovery and Undergraduate Student Research Awards programs of the Natural Sciences and Engineering Research Council of Canada, and the Ontario Graduate Scholarship program.


[1]Kaye, Elena A., et al. "Closed-Bore Interventional MRI: Percutaneous Biopsies and Ablations." American Journal of Roentgenology 205.4 (2015): W400-W410.

[2] Zaporzan, Benjamin, et al. "MatMRI and MatHIFU: software toolboxes for real-time monitoring and control of MR-guided HIFU." Journal of therapeutic ultrasound 1.1 (2013): 1-12.


Figure 1: Diagram of the experimental set-up

Figure 2: Verification of the biopsy needle tip in contact with contrast enhanced target

Figure 3: Screen-shot of real time dynamic image display showing double-oblique auxiliary views (centre, right) aligned to the biopsy needle according to points highlighted in the interactively controlled primary view (left)

Figure 4: A volunteer operator performing the experimental procedure with a projector screen mounted inside the scanner bore

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)