A system for controllable adjustment of the temperature of a treatment element of a medical device, the system comprising: a fluid delivery conduit in fluid communication with the treatment element including an upstream portion and a downstream portion; a subcooler located between the upstream fluid flow path and the downstream fluid flow path; a bypass fluid flow path having a first end that is in direct communication with the upstream fluid flow path and a second end that is in direct communication with the downstream fluid flow path; a first valve (S1) located in the upstream fluid flow path between the subcooler and the first end of the bypass fluid flow path ; and a second valve (SX) located in the bypass fluid flow path ; a fluid recovery conduit in fluid communication with the treatment element ; a third valve in the fluid recovery conduit; and an operating console including a processor , the processor being programmed to: circulate a fluid within the treatment element at a first temperature, the first temperature being a temperature at which tissue ablation occurs; characterised in that the processor adjusts the first valve (S1) and the second valve (SX) during a thawing phase to increase the temperature of the fluid within the treatment element to a second temperature that is greater than the first temperature; and then extends the thawing phase of the treatment element by maintaining the fluid within the treatment element at a temperature of between -20 °C and -25 °C for a period of time between two seconds and 40 seconds by adjusting the first valve (S1) and the second valve (SX). a fluid delivery conduit in fluid communication with the treatment element including an upstream portion and a downstream portion; a subcooler located between the upstream fluid flow path and the downstream fluid flow path; a bypass fluid flow path having a first end that is in direct communication with the upstream fluid flow path and a second end that is in direct communication with the downstream fluid flow path; a first valve (S1) located in the upstream fluid flow path between the subcooler and the first end of the bypass fluid flow path ; and a second valve (SX) located in the bypass fluid flow path ; a fluid recovery conduit in fluid communication with the treatment element ; a third valve in the fluid recovery conduit; and an operating console including a processor , the processor being programmed to: circulate a fluid within the treatment element at a first temperature, the first temperature being a temperature at which tissue ablation occurs; characterised in that the processor adjusts the first valve (S1) and the second valve (SX) during a thawing phase to increase the temperature of the fluid within the treatment element to a second temperature that is greater than the first temperature; and then extends the thawing phase of the treatment element by maintaining the fluid within the treatment element at a temperature of between -20 °C and -25 °C for a period of time between two seconds and 40 seconds by adjusting the first valve (S1) and the second valve (SX). circulate a fluid within the treatment element at a first temperature, the first temperature being a temperature at which tissue ablation occurs; characterised in that the processor adjusts the first valve (S1) and the second valve (SX) during a thawing phase to increase the temperature of the fluid within the treatment element to a second temperature that is greater than the first temperature; and then extends the thawing phase of the treatment element by maintaining the fluid within the treatment element at a temperature of between -20 °C and -25 °C for a period of time between two seconds and 40 seconds by adjusting the first valve (S1) and the second valve (SX). <EOS>