Strategies in MR-guided focused ultrasound

PurposeTo determine under-sampled k-space gradient echo trajectories for MR thermometry with PRF shift to increase acquisition speed while maintaining temperature accuracy.MethodsA computer simulation was built and used to study the behaviour of temperature measurement errors as different lines of k-space were acquired. A fully acquired k-space was constructed from the information in the Bioheat Transfer Equation (BHTE), various k-space under-sampling schemes were employed and temperature maps were reconstructed using the PRF shift method as a basis. Temperature errors were calculated as the difference in the maximum temperature predicted by the BHTE and the maximum temperature measured by the under-sampled scheme. ResultsUnder-sampled gradient echo keyhole trajectories showed promising results for making temperature measurements. Using 5 interleaves with a 63 keyhole size estimates temperature with only a 0.4% error while providing a 1.68x faster frame rate.ConclusionGradient echo keyhole trajectories can be used to make temperature measurements for MR thermometry with PRF shift. This method can also be applied for shorter sonications and making temperature estimates for multiple slices