Biomedical Engineering Reference
In-Depth Information
TABLE 12.1
Studies Describing the Use of Image-Guided Navigation with Radiofrequency Ablation
Organ
Image Modality
Navigation
Study
Reference
Liver
CT
Planning only
Clinical data
Villard et al. (2005)
Liver
CT
Planning only
Clinical data
Bale et al. (2010)
Liver
CT
Robot assisted
Human trial
Solomon et al. (2006)
Liver
CT
Optical
Human trial
Mundeleer et al. (2008)
Liver, Kidney
CT
Electromagnetic
Human trial
Stone et al. (2007); Giesel et al. (2009)
Liver
MRI
Optical
Human trial
Maeda et al. (2009)
Bale et al. (2010). These authors provide an excellent overview
of the difficulties in precisely placing the radiofrequency abla-
tion probe in clinical cases where the lesions are close to major
vessels or the size of the lesion requires overlapping probes. They
discuss the potential of navigation and image guidance for plan-
ning and executing RF ablations and give an example case of six
different trajectories for a large liver metastasis.
The development of a treatment planning system for overlap-
ping ablations along with robotic assistance for accurate needle
placement was described by Solomon et al. (2006). Customized
software was developed to allow the user to overlay predicted
zones of ablation onto the CT images from two commercially
available RFA systems. The planning software was coupled to
a surgical robot called Acubot that included a remote center
of motion capability for needle positioning at any orientation.
A human clinical study was completed on two patients with
hepatic lesions larger than 3.0 cm that required two overlap-
ping ablations. In both cases the overlapping ablations were per-
formed through the same skin entry site, and no complications
were observed.
A navigation system for radiofrequency ablation was devel-
oped by a group in Belgium (Mundeleer et al. 2008). The naviga-
tion system was based on optical tracking (Polaris, NDI), and
passive retroreflective markers were attached to the handle of
the RFA probe. Image registration was accomplished by a com-
bination of landmark transforms (paired point matching) and
an iterative closest point implementation.
Ex vivo
experiments
were completed using a graduated box phantom and a veal liver,
followed by two
in vivo
tests, one laparoscopic and one percuta-
neous. The results showed the feasibility of the approach and the
potential of such a system in the clinical environment.
One pioneering group in the use of navigation for RFA has
been the Center for Interventional Oncology at the NIH Clinical
Center. This group has demonstrated the feasibility of fusing CT,
MRI, and PET for treatment planning, navigation, and follow-up
in RFA for kidney and liver tumors (Giesel et al. 2009). For RFA
of kidney tumors, electromagnetic tracking (Aurora, Northern
Digital) was used with multiplanar reconstructed CT images
(Percunav, Traxtal Inc., Toronto, and Philips Medical Systems,
Andover, MA) to guide probe placement (Figure 12.7).
While most of the work in navigation for RFA has been based
on CT imaging, several researchers have investigated other
imaging modalities, including MRI. A Japanese group per-
formed ablation on 34 liver cancer patients using a navigation
system based on open MRI (Maeda et al. 2009). An ultrasound
probe was tracked with a Polaris optical tracking system, and
during ablation, the ultrasound probe, needle, tumor, and MR
image were displayed on the monitor (Figure 12.8). Registration
between the real-time ultrasound images and the preoperative
MR images was done using the open source 3D Slicer navigation
and display software (Brigham and Women's Hospital, Boston,
Massachusetts) (Gering et al. 2001).
12.3.3 Cryoablation
12.3.3.1 Introduction
While cyroablation has been part of medical practice for sev-
eral decades, it is only in the last several years that technological
advances have resulted in cyroprobes thin enough (down to 17
gauge) for percutaneous applications. The objective of cyroabla-
tion is to reduce the temperature of the tumor and a surround-
ing margin to below the lethal level of minus 20°C without
damaging surrounding healthy tissue (Georgiades et al. 2011).
The major applications of cyroablation are in the kidney and
prostate, although the technology has also been employed in
other organs.
There are two FDA-approved cyroablation systems available
in the United States from the companies Endocare and Galil
Medical. Endocare was recently acquired by HealthTronics and
offers four cyroprobes, with the largest probe generating a -20°C
teardrop-shaped isotherm of 44 mm in length and 24 mm in
diameter. The Galil Medical system also offers four cyroprobes
that also differ in the size and shape of ice ball created. These
devices, along with a sampling of cryoprobes, are shown in
Figure 12.9.
12.3.3.2 Navigation Systems and Cyroablation
While there have not been as many studies published on the
use of navigation systems in cyroablation as in radiofrequency
ablation, there have been several investigations worth noting
as shown in Table 12 . 2. Most of the cryoablation studies have
focused on the kidney, but there have been also been several
studies investigating the liver and other organs. Each study
listed in the table will now be described.The use of navigation in
percutaneous renal tumor ablation was investigated in a clinical
trial of 10 patients (Haber et al. 2010b). Patients with enhancing
renal masses underwent a preoperative CT scan with a preplaced
tracking sensor. The CT images were sent to the navigation plat-
form for three-dimensional volume rendering. A handle that
