Improved Image Guidance for Minimally Invasive Liver Therapy: Image Co-registration Techniques
Abstract
Open surgeries are fast being replaced by minimally invasive procedures and noninvasive
procedures. Image guidance is an indispensible tool during these procedures.
When using navigation systems in minimally invasive procedures, pre-operative
images are frequently used for guidance. However, these images do not display
changes occurring during the surgery. Therefore, intra-operative imaging is also used.
By combining intra-operative and pre-operative information, the procedure may be
improved. The registrations of the pre-operative images with the updated intraoperative
images will allow better overview and availability of needed information,
which will give more accurate tool guidance and targeting during surgery.
This PhD thesis gives an overview of technologies used in laparoscopic surgery.
Registration methods and validation studies were explored and investigated to be able
to improve the outcome of the minimally invasive procedures.
Cone beam CT was explored as an intra-operative imaging modality in a laparoscopic
setting. This was done to evaluate the deformations introduced in the liver due to
pneumoperitoneum and respiration. Shifts as large as 44.5mm were found in this
study.
4D ultrasound can be used as an intra-operative imaging technique as well as for the
registration of pre-operative images to patient anatomy using 4D ultrasound images as
an aid. A validation study of a motion estimation method was carried out on the liver
of healthy volunteers. We found that the method was capable of tracking structures
with an accuracy of 1mm.
We studied the effect of non-periodic motion of drift in the liver owing to peristalsis
movement and gravity. Initial results confirm a drift of 5.95mm comparing
inhalations and 8.09 mm comparing exhalations when acquiring data over a period of
30 minutes.
The surgeons can benefit more from the information available in the pre-operative
CT/MR images in combination with intra-operative imaging such as ultrasound with
more accurate image fusion techniques together with tool navigation and
visualization. The work performed in this thesis with further development has
potential for improving surgical outcome of minimally invasive liver therapy and also
other abdominal soft tissue therapeutic procedures.