Cryoablation of an adrenal metastasis under CT guidance

An 85-year-old male patient, suffering from bronchial carcinoma, was diagnosed with a left adrenal mass. It was progressive in size, despite prior radiotherapy, therefore being highly suggestive of a metastasis. The patient was admitted for cryoablation.

The patient was placed in left lateral decubitus to prone position. The intervention was performed under general anesthesia.

The metastasis in the left adrenal gland, measuring approx. 5 cm in diameter, was seen in a biphasic (arterial and venous) contrast CT scan for planning, showing peripheral enhancement in the venous phase. The lesion was closely located between the upper pole of the left kidney and the abdominal aorta.

The access routes were planned using myNeedle Guide 3D. A total of six cryoprobes (Boston Scientific IceRod 1.5 CX 90°) were placed in the lesion using dorsal paravertebral or intercostal paths. Due to the lack of alternative access routes, three probes had to be placed using a transpulmonary approach. A 10-minute freeze cycle was carried out, followed by passive thawing for 9 minutes. Then another 10-minute freeze cycle was followed by an active thawing of 1 minute. The growth of the ice ball and the ablation zone were monitored at 8-minute intervals by CT scanning using i-spiral. Tract ablation was performed at the removal of the probes to prevent track seeding.

A biphasic (arterial and venous) control contrast CT scan was performed, showing a hypodense area in the ablation zone without contrast enhancement of the adrenal gland. No signs of post-interventional complications, especially neither bleeding nor pneumothorax, were seen.

The patient was dismissed from the hospital the day after the procedure. A follow-up CT, three months after the cryoablation, showed complete devascularization of the lesion with no signs of recurrence.

Fig. 2: An axial image from a follow-up contrast CT scan, 3 months after the cryoablation procedure, showed complete devascularization of the lesion (arrow) with no signs of recurrence.

Cryoablation applies alternating cycles of freezing and thawing to cause mechanical stress on the cellular membranes from intracellular ice crystal formation and hypotonic cell disruption. Adrenal ablations are usually performed under CT guidance. The success of the procedure, as well as the prevention of nontarget thermal injury, highly rely on precise probe positioning, meticulous preprocedural planning and intraprocedural monitoring.

Studies have shown that cryoablation has a lower risk of a hypertensive crisis than microwave ablation. [1,2] During the cryoablation procedure, the ice ball growing, and thus the ablation area, can be clearly monitored on CT imaging. Potential damages to risk structures, such as vessels (a renal artery in this case) in the target area can be carefully avoided. The trajectories of six cryoprobes are planned on multiplanar reformats (MPRs) using myNeedle Guide 3D. This method is particularly helpful in planning a double angulated access path. The planned path is individually transferred by “one-click” to the laser guidance system, myNeedle Laser, integrated in both software and hardware of the CT scanner, SOMATOM X.ceed. Two of the four laser projectors installed on the gantry are utilized for visualizing the probe. Specifically, these two projectors are combined to visualize both the entry point and trajectory angle of the probe accurately. The selection criteria for these two adjacent laser projectors prioritize precision in entry point and trajectory angle visualization. During the probe placement, short sequential (i-sequence) or spiral (i-spiral) scans are performed to monitor the progress. With the help of the laser guidance system, the workflow of the probe positioning becomes more efficient, facilitating a successful placement of six cryoprobes in the tumor.