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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