Flashes sequence

Fig. 1.20 Gradient-echo based pulse sequences based on low flip angles. When low flip angles and short image repetition times are employed at the expense of transverse magnetization during the course of the complete image acquisition, this represents a FLASH sequence (without ). The combination of flip angle and repetition time can be adjusted in...

Table 18.2 summarizes the sequences and MR techniques which in our experience can be proposed (as mandatory or optional) in the diagnostic management of veno-occlusive disorders of the brain. Venous MRA can either be performed with the time-of-flight (TOF) or with the phase-contrast (PC) technique. In addition to the tomographic images, a flow sensitive gradient-echo sequence should be obtained if CVST is in question. As a fast screening examination we prefer a TOF 2D FLASH sequence (Table 18.2 Fig. 18.4, see 18.6c), oriented 90 degree to the flow direc-...

Oscillation was not essentially observed in the oxygen yields when a flash sequence was preceeded by weak continuous illumination [188,190]. This result has been taken as evidence that the steady-state concentrations of the S states are very similar, and consequently the quantum yields of the photosteps must be equal. If this conclusion is correct, one quantum is involved in each transition, since in nonsaturating flashing light the Oj yield, monitoring the final transition 84 80, depends linearly upon the flash intensity [189]. 

Rg. 6.2.10 [Haal] Timing diagram of the 2D FLASH sequence for fast imaging. The method employs slice-selective excitation pulses of the order of 15°. 

Images can be acquired using standard, relaxation-weighted spin-echo and FLASH sequences. The contrast is based on the transverse proton relaxation time T2 of water. 

The process is visualized by injection of Gd + chelate complexes like Gd(DTPA) as contrast agents on top of the column and using a FLASH sequence for rapid imaging. The unique insight into the separation process gained by NMR ima ng is illustrated in Figure 10.1.4 by a series of FLASH images [Bayl] a parabolic profile arises from faster elution in the core of the column. It is caused by a combination of wall absorption and thermal effects from a temperature distribution across the column diameter. The band... 

Oxygen sequences The damping of the oscillations of the amount of oxygen produced by each flash during a flash sequence is dependant on the concentration of "closed centers" (due to Q ) remaining after the dark period between flashes. The calculated miss parameter was increased for DCMU-II, DClIU-IIg and AzV mutants the increase was very small for AzI and loxi as compared to the wild type. It was also increased for Chenopodium album resistant thylakoids as compared to susceptible thylakoids. 

Papanikolaou N, Grammatikakis J, Maris T, Lauenstein T, Prassopoulos P,Gourtsoyiannis N (2003) MR colonog-raphy with fecal tagging comparison between 2D turbo FLASH and 3D FLASH sequences. Eur Radiol 13 448-452... 

The examination can be completed with a Tl-weighted 2D FLASH sequence in the axial plane, which permits assessment of the adjacent abdominal organs with high image quality. 

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. 

Before and after LITT treatment Tj-weighted (SE, GE), and T2-weighted (SE) images are obtained. Of special importance is a dynamic Turbo-FLASH sequence protocol, which acquires images prior to as well as in short delays (6 s) following the intravenous administration of contrast over a length of 180 s. Follow-up studies including non-enhanced and contrast-enhanced sequences are performed 1,... 

Rofsky NM, Weinreb JC, Ambrosino MM, et al (1996) Comparison between in-phase and opposed-phase Tl-weighted breath hold flash sequences for hepatic imaging. J Comput Assist Tomogr 20 230-235... 

Fig. 3. Deeaspidin extends, and pveillumination shortens, the lag in onset of ATP formation. Chloro--plasts were suspended in SO irM sorbitol, SO wM trioine-KOH pH 8.S, 3 mM MgCl2 and 0.1 wM methyl viologen with IS g chi nil ". Stringently dark conditions were main tained in the room and throughout the storage, transfer and incubation periods. After the appro--priate dark or pre-illumination treatments, luciferin-luciferase, diddenosine pen-taphosphate, ADP, Pi and lO M valinomycin were added. The start of the 1 Hz flash sequences is indicated by the upward pointed arrow, the end by the downward arrow. A fresh sample was prepared for each treatment, except for curve 4, which is...

Fig. 4. Effects of deeaspidin and BSA at pH 7.0. The eocperiment was simitar to that of Fig. 3 except the pH was adjusted to 7.0. Curve 1, similar in plan to curve 1, Fig 3, hut djesaspidin was given at 0.2 then 2.5 mg BSA was added followed by 6 minutes of dark prior to the 1 Hz flash sequence to drive ATP formation. Curve Similar to curve 1, hut 2 min after 2.5 mg BSA addition, 36 single-turnover flashes were given at 1 Hz, followed hy 6 min darkness. The remaining components of the ATP assay were added during the last min of darkness, prior to the ATP formation assay. Curye A control, with BSA added before desaspidin.

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