Kim Butts Pauly's Lab

Overview of MR-Guided Cryoablation of the Prostate

We have been developing methods for MRI monitoring cryoablation of the prostate. While for some procedures, it is sufficient to know the iceball boundary, prostate cancer cryoablation requires knowledge of which tissue reached a sufficiently cold temperature of -20°C - -40°C. Therefore, we have investigated the relationship of MRI parameters to temperature of frozen tissue. As tissue freezes, the signal intensity decreases as free water is taken up into ice crystals. In addition, the R2* (=1/T2*) increases as the signal is now dominated by the hydration water (water loosely bound to macromolecules). Either of these can be related to temperature, though the SI is relative and sensitive to tissue motion, while the R2* is not.

Since T2* values of frozen tissue are very short, we have used ultrashort echo time pulse sequences consisting of half pulse excitation and spiral or PR readouts. The half pulse excitation has been very sensitive to eddy currents, so we have been looking at ways to decrease this sensitivity, including gradient measurement methods, new half pulse methods, and saturation of all out of slice signal.

We have also looked at how the consistency of the MR parameters of several frozen tissues, including prostate, kidney, muscle, and liver. R2* values are very similar, suggesting the MR-visible macromolecular content of the tissues is similar. This is the same effect that results in a similarity in the magnetization transfer (MT) absorbtion between different tissue types.

Relevant Lab Publications

Daniel B, Butts K, Block W, Magnetic Resonance Imaging of Frozen Tissues - Temperature Dependent MR Signal Characteristics and Relevance for MR Monitoring of Cryosurgery, Magn Reson Med, 1999;41:627-630.

Butts K, Sinclair J, Wansapura J, Daniel B, Pauly J, Temperature Quantitation and Mapping of Frozen Tissue, Invited Orginal Research Paper, JMRI 2001; 13:99-104.

Wansapura J, Daniel B, Pauly J, and Butts K, Temperature Mapping of Frozen Tissue Using Eddy Current Compensated Half Excitation RF Pulses, MRM, 2001, 46(5):985-92.

Butts K, Daniel B, Chen L, Bouley D, Wansapura J, Maier S, Dumoulin C, Watkins R, Diffusion-Weighted MRI after Cryosurgery of the Canine Prostate, JMRI 2003, 17(1):131-5.

Wansapura J, Daniel B, Vigen K, Butts, K, In Vivo MR Thermometry of Frozen Tissue Using R2* and Signal Intensity, Academic Radiology. 2005 Sep;12(9):1080-4.

Lu A, Pauly J, Butts Pauly K, Improved Slice Selection for R2* Mapping during Cryoablation with Eddy Current Compensation, JMRI, 2008 Jul;28(1):190-8

Chen J, Daniel BL, Diederich CJ, Bouley DM, van den Bosch MA, Kinsey AM, Sommer G, Butts Pauly KB, Monitoring prostate thermal therapy with diffusion-weighted MRI, Magn Reson Med, 2008 Jun; 59(6):1365-72.

Van den Bosch M, Josan S, Bouley D, Chen J, Rieke V, Butts Pauly K, Daniel BL, MRI-guided Percutaneous Cryoablation of the Prostate: In Vivo Imaging of Cryonecrosis with histologic correlation in an animal model, JVIR, 2009 Feb;20(2):252-8, PMID: 19091600.

Josan S, Pauly J, Daniel B, Butts Pauly K, Improved Half RF Slice Selectivity in the Presence of Eddy Currents with Out-of-Slice Saturation, MRM, 2009 Mar 24;61(5):1090-1095. PMID: 19319972.

Josan S, Pauly J, Daniel B, Butts Pauly K, Double Half RF Pulses for Reduced Sensitivity to Eddy Currents in UTE Imaging, MRM, 2009 Feb;61(5):1083-1089. PMID: 19235919.

Josan S, Bouley D, van den Bosch M, Daniel B, Butts Pauly K, MRI-guided cryoablation - in vivo assessment of focal canine prostate cryolesions, JMRI, 2009 Jul;30(1):169-76. PMID: 19557805.

Kaye E, Josan S, Lu A, Lynch S, Rosenberg J, Caires C, Butts Pauly K, Consistency of Signal Intensity and T2* in Frozen Porcine Heart Muscle, Kidney, and Liver, JMRI, 2010 Mar;31(3):719-24. PubMed PMID: 20187218; PubMed Central PMCID: PMC2832094.

Lu A, Daniel B, Kaye E, Butts Pauly K, MRI of Frozen Tissue Demonstrates a Phase Shift, MRM, 2011 May 31. [Epub ahead of print]. PMID: 21630347

Ghanouni P, Gill H, Kaye E, Butts Pauly K, Daniel B, MR Imaging-guided Cryoablation for the Treatment of Benign Prostatic Hyperplasia, J Vasc Interv Radiol, 2011 Oct;22(10):1427-30. PMID: 21961982  PMCID: PMC3185301.

Abstracts Not Published Elsewhere

Kaye E, Lu A, Alley M, Butts Pauly, K, PRF Shift in Frozen Tissue at 3T, ISMRM 2009

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