IMAGE-GUIDED
CRYOABLATION
LIVER METASTASIS —
Cryosurgery Procedures
Image
Guided Percutaneous Cryoablation of Secondary
Liver Cancer
Galil Medical’s third
generation ultra-thin
cryoablation needles have made it possible
to treat liver metastases percutaneously (through
the skin), without surgical incisions. By combining
these 1.47 mm diameter needles with the interventional
radiologist’s specialized knowledge of minimally
invasive cancer treatment procedures, patients
can benefit from a shorter hospital stay and a
quicker return to everyday life. Also, the ability
to perform the procedure percutaneously may expand
the patient population that can receive curative
as well as palliative treatment for secondary
hepatic malignancies.
MRI compatible cryoablation
needles and thermal
sensors are also available, allowing cryoablative
treatment for liver cancer to be performed safely
as a minimally-invasive procedure under image
guidance. Image guidance refers to the use of
imaging techniques (e.g., fluoroscopy, ultrasound,
CT and MRI) during a procedure. Percutaneous
cryoablation is often performed in an interventional
treatment room in the radiology department rather
than in the operating room. It can be performed
under general anesthesia, or under conscious sedation
with local anesthesia.
Intraprocedurally, imaging is used
to target and place the cryoablation
needles into the tumor, to monitor the double
freeze-thaw process, and to control the treatment,
as necessary. Imaging is also used before the
procedure to plan the treatment and after the
procedure to assess the treatment response.
The interventional radiologist will
usually perform a scan about a week before the
scheduled intervention in order to create a plan
for the procedure. The plan will include the entrance
site of the cryoablation
needles, and how many cryoablation
needles will be needed to ablate the targeted
tissue along with a 1 cm margin. Because the size
and shape of the iceball formed by each cryoablation
needle is predictable, the physician is able to
accurately plan the treatment in advance. This
information is also a factor in determining the
type of anesthesia that will used, and allow the
interventional team to make sure that adequate
amounts of gas and other accessories are available
at the time of the procedure.
At the time of the procedure, the
patient is positioned on the gantry so that the
I.R. physician as well as anesthesia personnel
have the access to the patient that they need.
A pre-procedure scan will be performed to confirm
the planned needle entry site. The patient is
then prepped and draped, and local anesthetic
is injected. If a biopsy is to be taken before
the cryoablation, it is taken at this time. The
first cryoablation
needle is placed and another scan is performed
to confirm that the placement is correct. This
procedure is repeated for each needle and thermal
sensor used.
The first freeze cycle is then initiated, and a CT or MRI scan is taken about 3-5 minutes into the cycle to monitor the formation of the iceball. For more information about the technology behind the cryoablation process, see the section Cryoablation Technology. By imaging at this point in the procedure, the physician can confirm that the iceball is completely engulfing the tumor.
After the initial freeze, the iceball is allowed to thaw for a few minutes. This thawing process is also an important part of tumor destruction. To learn more about how the cryoablation cycle destroys tumors, please see the section on Cryobiology. A second freeze cycle is performed, after which a short active thaw allows the physician to loosen the needles from the iceball and remove them from the body. The needle insertion sites are then closed and dressed.
A scan is usually performed immediately
following the procedure to assess the initial
response of the targeted tissue. The physician
can determine by the size and shape of the cryolesion
if the tumor has been covered according to the
pre-treatment plan. During the follow-up period,
the physician will perform MRI or CT scans at
regular intervals to screen for residual tumor
and recurrent disease. One of the many benefits
of image-guided percutaneous cryoablation to treat
liver metastases is that it can be repeated, if
necessary, without the trauma of open surgery.
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