Biomedical subjects

Dominik Paul

Publications and source records attributed to Dominik Paul.

4 recordsLinked to original sources

PubMed2006

T2-weighted balanced SSFP imaging (T2-TIDE) using variable flip angles.

A new technique for acquiring T2-weighted, balanced steady-state free precession (b-SSFP) images is presented. Based on the recently proposed transition into driven equilibrium (TIDE) method, T2-TIDE uses a special flip angle scheme to achieve T2-weighted signal decay during the transient phase. In combination with half-Fourier image acquisition, T2-weighted images can be obtained using T2-TIDE. Numerical simulations were performed to analyze the signal behavior of T2-TIDE in comparison with TSE and b-SSFP. The results indicate identical signal evolution of T2-TIDE and TSE during the transient phase. T2-TIDE was used in phantom experiments, and quantitative ROI analysis shows a linear relationship between TSE and T2-TIDE SNR values. T2-TIDE was also applied to abdominal and head imaging on healthy volunteers. The resulting images were analyzed quantitatively and compared with standard T2-weighted and standard b-SSFP methods. T2-TIDE images clearly revealed T2 contrast and less blurring compared to T2-HASTE images. In combination with a magnetization preparation technique, STIR-weighted images were obtained. T2-TIDE is a robust technique for acquiring T2-weighted images while exploiting the advantages of b-SSFP imaging, such as high signal-to-noise ratio (SNR) and short TRs.

Brain↗

PubMed2006

Intrinsic fat suppression in TIDE balanced steady-state free precession imaging.

A novel fat-suppressed balanced steady-state free precession (b-SSFP) imaging method based on the transition into driven equilibrium (TIDE) sequence with variable flip angles is presented. The new method, called fat-saturated (FS)-TIDE, exploits the special behavior of TIDE signals from off-resonance spins during the flip angle ramp. As shown by simulations and experimental data, the TIDE signal evolution for off-resonant isochromats during the transition from turbo spin-echo (TSE)-like behavior to the true fast imaging with steady precession (TrueFISP) mode undergoes a zero crossing. The resulting signal notch for off-resonant spins is then used for fat suppression. The efficiency of FS-TIDE is demonstrated in phantoms and healthy volunteers on a 1.5T system. The resulting images are compared with standard TrueFISP data with and without fat suppression. It is demonstrated that FS-TIDE provides a fast and stable means for homogenous fat suppression in abdominal imaging while maintaining balanced SSFP-like image contrast and signal-to-noise ratio (SNR). The scan time of FS-TIDE is not increased compared to normal TrueFISP imaging without fat suppression and identical k-space trajectories. Because of the intrinsic fat suppression, no additional preparation is needed. Possible repetition times (TRs) are not firmly limited to special values and are nearly arbitrary.

Adipose Tissue↗

PubMed2004

Can body volume be determined by PET?

PURPOSE: To avoid dependence on body weight, the standardised uptake value (SUV) in positron emission tomography (PET) can instead be normalised to the lean body mass (LBM), which can be determined from body volume and mass. This study was designed to answer the following questions: Firstly, can the total body volume in principle be determined using PET? Secondly, is the precision of this measurement comparable to that achieved using an established standard method. METHODS: Ten patients were examined during oncological whole-body PET examinations. The whole-body volume of the patients was determined from the transmission scan in PET. Air displacement plethysmography with BOD POD was used for comparison as the standard method of volume determination. RESULTS: In all patients, the whole-body volumes could be determined using PET and the standard method. Bland and Altman [23] analysis for agreement between the volumes determined by the two methods (presentation of differences vs means) revealed a very small difference of -0.14 l. With a mean patient volume of 71.81+/-15.93 l, the relative systematic error is only <0.1%. On this basis, equality of the volume values determined by the two methods can be assumed. CONCLUSION: PET can be used as a supplementary method for experimental determination of whole-body volume and total body fat in tumour patients. The fat content can be used to calculate the LBM and to determine body weight-independent SUVs (SUV(LBM)).

Anthropometry↗

PubMed2004

TRIM: TR independent multislice imaging.

This article introduces a novel concept to overcome the dependence of image contrast on spatial positioning parameters such as the number of slices and slice separation in multislice measurements: TR-independent multislice (TRIM) acquisition allows the number of slices in a single measurement to remain independent of the repetition time TR. Ramped TRIM (rTRIM) allows the distance between the sections excited in each repetition to remain independent of the distance between the reconstructed slices. Even images from overlapping slices can be acquired without crosstalk between the images of adjacent slices due to spatially overlapping excitation profiles. This concept is based on a special reordering scheme: Within a single TR acquisition, steps are only taken from a fraction of all slices. This necessitates attribution of different phase-encoding steps to different slices within each repetition cycle. The reordering scheme can be derived by the use of a design matrix. The imaging properties of the technique are discussed theoretically and illustrated by a point spread function analysis based on simulations and phantom measurements. Potential sources of artifacts are identified and methods for their prevention are developed. Optimized implementations with different T(1)-weighted sequences such as spin echo (SE), turbo spin echo (TSE), and spoiled gradient echo acquisitions are shown on normal volunteers with imaging parameters used in routine diagnosis.

Humans↗