Tracking of liver metastases during surgery

Image-guided navigation surgery allows for full utilization of
pre-operative imaging during surgery, and has the potential of reducing both
irradical resections and morbidity. This is in liver surgery the first pilot
study towards clinical implementation.

Primary Objective:
To measure distances between the pointer tip held on surgical clips placed on
the liver surface and the closest tumor border using navigation, and compare it
to the actual distance measured in intraoperative XperCT.

Secondary Objectives:
* To assess the feasibility of intraoperative XperCT acquisition and
registration to preoperative imaging. Feasibility is judged in visual
inspection of similarity of the vessels and lesions on the images.
* To determine the accuracy of the navigation system relative to anatomy before
the start of liver surgery (liver border measurement).
* To evaluate the usability this the newly introduced technique for users (i.e.
surgeons and surgical assistants).

An observational pilot study.
Participation in the study will not involve additional visits to the hospital
for the included patients. Informed consent will be obtained during the pre*
operative outpatient clinic appointment or upon admission to the hospital at
least one day before operation.
The standard preoperative contrast-enhanced diagnostic CT or MR-scan is used
for preoperative image segmentation to create a three dimensional model of the
liver. Important structures like the portal vein, hepatic vein, gall bladder,
cysts, ribs and tumor will be delineated. When the patient enters the OR, three
external patient trackers containing electromagnetic sensors are placed on the
back of the patient. Next, surgery starts according to the standard surgical
procedure. When the liver is mobilized, a single 6 degrees of freedom
electromagnetic marker is glued to the liver with medical glue in close
proximity to the expected location of the tumor. This reference*sensor will be
used during the surgery to track the current anatomical position of liver.
Additionally, up to four surgical clips are placed within the intended
resection area, they will be used for accuracy verification of the system.
After this, an intra*operative contrast-enhanced breath hold XperCT scan will
be acquired to enable registration based on hepatic vessels of the preoperative
MR scan and the current anatomical position of the patient. During this
CT-scan, EM tracking will measure the current orientation of the EM sensor.
During surgery, anatomical structures will be identified using the guidance of
a blunt tip probe of the electromagnetic navigation system. Total time of the
proposed measurements, including the intraoperative scan, will take no longer
than 30 minutes. This is a pilot study to evaluate the overall performance of
the surgical navigation system during surgery, without impact on the surgical
procedure itself.

Safety issues: No expected risks for the included patients are expected. A
similar approach for abdominal surgery was evaluated in 25 patients (N13NAV)
and no potential risks for patients were identified during the course of the
study.