Biomedical subjects

M Komu

Publications and source records attributed to M Komu.

57 records · Page 4Linked to original sources

PubMedDate not supplied

Tissue characterization of intracranial tumors by magnetization transfer and spin-lattice relaxation parameters in vivo.

T1s and magnetization transfer (MT) parameters of 36 intracranial tumors were determined in vivo at 0.1 T to assess their use in tissue characterization. The mobile water relaxation times (T1w) did not differ between tumor groups, whereas the T1s, the apparent MT relaxation times (T1a), and the parameters MT contrast (MTC) differed significantly between several tumor types. The MT rates (Rwm) demonstrated the most significant differences; Rwm values could reliably separate high grade and low grade gliomas. T1ws of the tumors were commonly in the same range as that of normal gray matter, whereas other parameters differed from those of normal brain. The results indicate that MT rates are superior to other parameters in the characterization of intracranial tumors and may be also useful clinically in the grading of gliomas.

Adenoma↗

PubMedDate not supplied

Negative gastrointestinal contrast enhancement and image distortion induced by superparamagnetic particles at 0.02 Tesla.

Gastrointestinal contrast enhancement and image distortion induced by superparamagnetic particles were evaluated in vitro and in rabbits at 0.02 Tesla. Test tubes containing 0.01-1.0 mg particles/ml were imaged in an oil or water bath in order to demonstrate the concentration-dependent signal void and image distortion in vitro at several pulse sequences. The lowest concentration of particles tested clearly decreased the signal intensity. Image distortion was observed when the concentration exceeded 0.07 mg/ml and was more pronounced on the T2-weighted images. The in vitro T2 relaxation time decreased from 122 ms to 56 ms with an increase in the particle concentration from 0.01 to 0.06 mg/ml. A loss of the GI-tract signal was observed in rabbits after the administration of 1 mg particles/kg, given as a 0.03 mg/ml suspension. At a dose of 20 mg/kg (0.6 mg/ml suspension) significant image distortion was observed.

Contrast Media↗

PubMedDate not supplied

Method dependence of proton spin-lattice relaxation analysis in biologic tissues.

Spin-lattice proton relaxation times (T1) in several biologic and phantom samples have been measured and analysed by using standard inversion recovery (IR) and spin echo (SE) sequences at 0.02 T. The average T1 of the sample was measured with the two-data point method. In the case of bi-exponential relaxation the value of a single T1 is strongly dependent on the TI and TR selected. With short TI the T1 value obtained by using the two point method is approximately equal to the weighted average of the two relaxation time components (T1s and T1l), while at long inversion times TI the single T1 is more dependent on the long component T1l. The more the true short and long relaxation time components T1s and T1l of the bi-exponential relaxation differ from each other, the greater is the potential error, provided that the weights ws and wl do not differ very much. When two-data point analyzing method is used, the possible multi-exponential behaviour of the relaxation in tissues will be missed. For more reliable T1 values a series of images with as many values of TI as possible should be taken. Knowledge of true multi-exponential relaxation parameters helps in optimizing the sequence parameters and the image contrast between the various tissues.

Animals↗