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SU‐GG‐J‐105: Image‐Guided Thermal Ablation in Bone Using Dynamic Chemical Shift Imaging
Author(s) -
Taylor BA,
Shetty A,
Elliott AM,
Springer AC,
Hwang KP,
Hazle JD,
Stafford RJ
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2961655
Subject(s) - materials science , imaging phantom , ablation , dynamic imaging , biomedical engineering , image resolution , laser ablation , temperature measurement , laser , nuclear medicine , nuclear magnetic resonance , optics , image processing , medicine , physics , image (mathematics) , computer science , digital image processing , quantum mechanics , artificial intelligence
Purpose: To investigate the use of a novel dynamic chemical shift imaging technique for guiding image‐guided thermal therapy delivery in bone ex vivo . Method and Materials: Interstitial laser applicators (980‐nm) were placed into the yellow marrow of freshly excised canine femur under MR‐guidance. A fluoroptic probe was inserted 0.5 cm from the laser source in order to provide an absolute measurement of temperature. Image acquisition was performed using a multiple gradient‐echo at 1.5T and a super‐resolution spectral processing algorithm was used to calculate the PRF of water and lipid. A six‐pixel ROI near the fluoroptic probe was created and the PRF of water and lipid were measured as a function of temperature to calculate the temperature sensitivity coefficient (TSC). Another bone was used to perform an external laser ablation. This was performed at 3.0T to demonstrate the use at higher fields even in the presence of gradient power constraints. Temperature maps were created using lipid as an internal reference for susceptibility and field drift correction. Results: The TSC of water was measured to be − 0.0108 ± 0.0001 ppm / ° C ( R 2 = 0.981 ) . The lipid showed low correlation and sensitivity to temperature with a TSC of − 0.0020 ± 0.0001 ppm / ° C ( R 2 = 0.438 ) . Interestingly, the TSC of the difference between water and lipid was − 0.0087 ± 4 e − 6 ppm / ° C ( R 2 = 0.961 ) which is consistent to findings in lipid‐water based phantom calibrations. Conclusion: We've demonstrated the ability of monitoring temperature changes in bone marrow which would be a great benefit in using image‐guided thermal therapies for treatment of primary and metastatic bone neoplasms. The technique possesses the ability to monitor the water PRF separate from the lipid, which alleviates the problem of lipid contamination in PRF temperature mapping with no time or SNR penalty. In addition, use of the lipid signal can potentially be exploited as an internal reference to correct for field‐drift or susceptibility errors in temperature estimation.