MR thermometry

All patients tolerated the procedure well under local anesthesia. The total procedure time was on average 90 min and all patients were treated on an outpatient basis. All complications observed were minor and no further treatment was necessary. Online MR thermometry allowed exact visualization of the extension of laser-induced changes and their relationship to the neighboring anatomy. Lesions up to 2 cm in diameter could be efficiently treated... 

MR thermometry is performed with a Turbo-FLASH sequence (TR/TE/TI = 7/3/400) as well as a Thermo-FLASH-2D sequence (TR/TE/Flip angle =102/8/15), which was found to he more sensitive to thermal induced. 

Vogl TJ, Mack MG, Muller P, Phillip C et al (1995) Recurrent nasopharyngeal tumors preliminary clinical results with interventional MR imaging-controlled laser-induced thermotherapy. Radiology 196 725 Vogl TJ, Mack MG, Hirsch HH, Muller P, Weinhold N, Wust P, Philipp C, Roggan R, Felix R (1997) In-vitro evaluation of MR-thermometry for laser-induced thermotherapy. Fortschr R5ntgenstr 167 638... 

Evaluation of the MR thermometry data during MR-guided laser-induced thermotherapy demonstrates that metastatic tissue is very sensitive to heat,... 

McDannold NJ, King RL, Jolesz FA, Hynynen KH (2000) Usefulness of MR imaging-derived thermometry and dosimetry in determining the threshold for tissue damage induced by thermal surgery in rabbits. Radiology 216 517-523... 

Proton Frequency Shift T1 Thermometry 320 Parenchymal Changes at MR Parenchymal Changes at CT Parenchymal Changes at US New Developments 324 Post-ablation Appearances and Follow-Up at Contrast Enhanced CT 325 Recognising Recurrence 326 Timing of Recurrence 327 CT vs MR for Detection of Recurrence 327 Conclusion 327 References 327... 

The wide range of the values of the energy which was applied to the metastases indicates that there is a high variance in heat distribution. Sometimes a couple of minutes are enough to treat a metastasis with a reliable safety margin and sometimes applications times of 30 min and more are necessary to get same necrosis in another metastasis of the same size. Therefore reliable nearly online monitoring of treatment is absolutely necessary in order to avoid over- or undertreatment of the metastases. Due to the fact that laser ablation is fully compatible with MR, vdiich is the most reliable method for thermometry, MR is very well suited for monitoring thermal ablation like LITT. 

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