Magnetic resonance imaging assisted cryosurgery

A method for utilizing information obtained from magnetic resonance imaging of a target region to control real-time cryosurgical parameters, said target region including a frozen region having a first temperature distribution, an unfrozen region having a second temperature distribution, and an interfacial surface bounding said frozen region, comprising the steps of:

• generating an image of said target region with a magnetic resonance imaging technique;
• identifying said frozen region as a section of the image so generated having no magnetic resonance signal;
• determining a temperature at said interfacial surface;
• solving the heat equation for the interior of said frozen region utilizing a temperature at said interfacial surface to determine said first temperature distribution in said frozen region;
• measuring nuclear relaxation times in said unfrozen region by a magnetic resonance technique;
• determining said second temperature distribution in said unfrozen region by calculations based on said nuclear relaxation times as measured by said magnetic resonance technique;
• and
• affecting said cryosurgical parameters according to said first and second temperature distributions to achieve a desired result.

A method for monitoring temperatures of a target region in a biological tissue with a magnetic resonance imaging technique and a cryoprobe, said target region including a frozen region having a first temperature distribution, an unfrozen region having a second temperature distribution, and an interfacial surface bounding said frozen region, comprising the steps of:

• generating an image of said target region with said magnetic resonance imaging technique;
• identifying said frozen region as corresponding to a section of the image so generated having a low magnetic resonance signal;
• determining a temperature at said interfacial surface;
• solving a heat equation for the interior of said frozen region utilizing the temperature at said interfacial surface to determine said first temperature distribution in said frozen region;
• measuring nuclear relaxation times in said unfrozen region by a magnetic resonance technique;
• determining said second temperature distribution using calculations based on said nuclear relaxation times measured in said unfrozen region;
• and
• using said first and second temperature distributions determined to monitor the temperature of said target region.

A method for monitoring temperatures of a target region in a biological tissue with a magnetic resonance imaging technique and a cryoprobe, said target region including a frozen region having a first temperature distribution, an unfrozen region having a second temperature distribution, and an interfacial surface bounding said frozen region, comprising the steps of:

• generating an image of said target region with said magnetic resonance imaging technique;
• determining the location of said frozen region using the image so generated;
• solving a heat equation for the interior of said frozen region using a temperature of approximately -0.56 degrees Celsius as the temperature at said interfacial surface to determine said first temperature distribution in said frozen region;
• determining said second temperature distribution for said unfrozen region;
• and
• using said first and second temperature distributions determined to monitor the temperature of said target region.