Giuseppe Carluccio

Measurement of SAR-induced temperature increase in a phantom and in vivo with comparison to numerical simulation.

To compare numerically simulated and experimentally measured temperature increase due to specific energy absorption rate from radiofrequency fields.

Radiofrequency field enhancement with high dielectric constant (HDC) pads in a receive array coil at 3.0T

To investigate the use of a new high‐dielectric constant (HDC) material for improving SNR and transmission efficiency for clinical MRI applications at 3 Tesla (T) with cervical spine imaging.

An Approach to Rapid Calculation of Temperature Change in Tissue Using Spatial Filters to Approximate Effects of Thermal Conduction

We present an approach to performing rapid calculations of temperature within tissue by interleaving, at regular time intervals, 1) an analytical solution to the Pennes (or other desired) bioheat equation excluding the term for thermal conduction and 2) application of a spatial filter to approximate the effects of thermal conduction. Here, the basic approach is presented with attention to filter design. The method is applied to a few different cases relevant to magnetic resonance imaging, and results are compared to those from a full finite-difference (FD) implementation of the Pennes bioheat equation. It is seen that results of the proposed method are in reasonable agreement with those of the FD approach, with about 15% difference in the calculated maximum temperature increase, but are calculated in a fraction of the time, requiring less than 2% of the calculation time for the FD approach in the cases evaluated.

Algorithm 934: Fortran 90 subroutines to compute Mathieu functions for complex values of the parameter

Software to compute angular and radial Mathieu functions is provided in the case that the parameter q is a complex variable and the independent variable x is real. After an introduction on the notation and the definitions of Mathieu functions and their related properties, Fortran 90 subroutines to compute them are described and validated with some comparisons. A sample application is also provided.

Predicting long‐term temperature increase for time‐dependent SAR levels with a single short‐term temperature response

Present a novel method for rapid prediction of temperature in vivo for a series of pulse sequences with differing levels and distributions of specific energy absorption rate (SAR).

Parallel transmission RF pulse design with strict temperature constraints

RF safety in parallel transmission (pTx) is generally ensured by imposing specific absorption rate (SAR) limits during pTx RF pulse design. There is increasing interest in using temperature to ensure safety in MRI. In this work, we present a local temperature correlation matrix formalism and apply it to impose strict constraints on maximum absolute temperature in pTx RF pulse design for head and hip regions. Electromagnetic field simulations were performed on the head and hip of virtual body models. Temperature correlation matrices were calculated for four different exposure durations ranging between 6 and 24 min using simulated fields and body‐specific constants. Parallel transmission RF pulses were designed using either SAR or temperature constraints, and compared with each other and unconstrained RF pulse design in terms of excitation fidelity and safety. The use of temperature correlation matrices resulted in better excitation fidelity compared with the use of SAR in parallel transmission RF pulse design (for the 6 min exposure period, 8.8% versus 21.0% for the head and 28.0% versus 32.2% for the hip region). As RF exposure duration increases (from 6 min to 24 min), the benefit of using temperature correlation matrices on RF pulse design diminishes. However, the safety of the subject is always guaranteed (the maximum temperature was equal to 39°C). This trend was observed in both head and hip regions, where the perfusion rates are very different.

A fast, analytically-based method to optimize local transmit efficiency for a transmit array

To develop an analytically based algorithm for rapid optimization of the local radiofrequency magnetic (B1+) field intensity for a given radiofrequency power through a transmit array. The analytical nature of the method will yield insight to optimization requirements and provides a valuable reference for numerically based searches.

Comparison of 2D and 3D models of the human head surrounded by a dielectric sheet in MRI scans

A sheet of high dielectric constant surrounding the head has been used in MRI scans to improve signal-to-noise ratio and lower the power transmitted by the array of coils. In a study presented at the URSI General Assembly and Scientific Symposium, Beijing, China, August 2014, we have presented a two-dimensional model in which the human head is simulated by a cylinder with appropriate uniform dielectric constant and conductivity, surrounded by a dielectric sheet of high permittivity and illuminated by an array of line sources. We proved that under appropriate excitation of the array elements, the electric field is zero and the magnetic field is locally maximum and circularly polarized on the axis of the structure.

Analytical approach to compute the electromagnetic field inside a model of the human head surrounded by a dielectric pad

We present an analytical approach to justify the behavior of the magnetic field observed when dielectric material is used to enhance magnetic resonance imaging (MRI) of the human head.

Optimization of the order and spacing of sequences in an MRI exam to reduce the maximum temperature and thermal dose: Order and Spacing of MRI Sequences

Evaluate the possibility to reduce specific energy absorption rate (SAR)‐induced maximum temperature and thermal dose by rearranging the order and spacing of sequences without increasing duration of the MRI examination.