13th Annual Global Embolization Symposium & Technologies
Purpose : To investigate ice balls formed with two cryoprobes crossing at two different positions in a tissue phantom.
Material and Methods : Experiments were performed using a tissue phantom comprising 0.9 % sodium chloride aqueous solution with 3 % gelatin and 0.3 % agarose-III. Two cryoprobes (IceSeed®) were crossed at an angle of 30 degrees at two different intersections: mid-crossing and proximally crossing, which indicated placements at 5.6 and 11.5 mm, respectively, in the tip-to-tip distance assuming the treatment of a target tumor of 2 cm in diameter. Parallel placement at a distance of 11 mm was also tested as a control. Changes in the shape and size of ice balls were examined during freezing for 210 seconds using CryoHit (Galil Medical Ltd., Israel) at the argon gas pressure of 25 MPa.
Results : In the parallel placement, cylindrical ice balls around individual probes connected with each other and formed a flat sphere. In the cross placement, ice balls initially had a different appearance, i.e. X shape (mid-crossing) and inverse V shape (proximally crossing), and then formed a bulk ice ball. However, the final shape and size of ice balls slightly differed from each another. The front views of ice balls had an oval shape (mid-crossing) and tear drop shape (proximally crossing). The final sizes of ice balls, i.e. the width, length, and distance between the probe tip and ice surface at the bottom, were 29/30/3.5 mm (parallel), 27.5/38.5/6 mm (mid-crossing), and 27.7/35/4 mm (proximally crossing), respectively. The final ice balls were larger than the 2 cm spherical target in all cases examined.
Conclusions : The shapes of ice balls produced with two crossing cryoprobes depended on the crossing points; however, the final ice balls were larger than the 2 cm spherical target in all cases examined.