Oneshot for Varian (G.A. Morris/M. Nilsson)

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Basic facts about Doneshot

Synopsis: DOSY pulse sequence using bipolar gradient pairs

Family: Diffusion experiments

Code authors:  Gareth A. Morris,  Mathias Nilsson

Copyright: Manchester University

Introduction

The Oneshot sequence is suitable for "one-shot" acquisition (only one transient per gradient level), and is also a good general DOSY sequence. The pulse sequence is a more elaborated version of BPPSTE sequence, using bipolar pulse pairs. The refinements include a purge pulse in the diffusion delay, unbalanced gradient pulses in the bipolar pulse pairs as well as heating compensation gradients that are incremented as the diffusion gradients are incremented.

The sequence

Macros

setup_dosy

Enters a dialog to set-up the gradient array with equal steps in gradient squared. It is normally advisable to make even the first gradient level significant (e.g. 3G/cm)

makedosparams

Sets the parameter dosytimecubed when the pulse sequence is run. Dosytimecubed is a convenient parameter when fitting the data e.g. to produce a DOSY plot.

NB! These macros are compatible with VnmrJ2.3 or older.

Software that can process DOSY data

• The DOSY package of Vnmr and VnmrJ

• DOSYToolbox

Note: expand this list, by creating pages for programs and adding category links "Software" and "DOSY" to those pages.

RF parameters

• pw,tpwr,tof - 90^o pulse, its power level and transmitter offset
• satdly,satpwr,satfrq - length, power and offset of saturation pulse (used if satmode='y')

Gradient parameters

• gzlvl1 - amplitude of diffusion encoding gradient
• kappa - unbalance factor for the bpp pulses. The default of 0.2 is almost always suitable
• gt1 - total length of gradient encoding pulses gradient (split into two equal length bipolar pulses)
• gzlvl3, gt3 - amplitude and duration of the spoiler/purge gradient
• gzlvl_max - safety parameter, will trigger error message if gzlvl1*(1+kappa) > gzlvl_max

Delays

• del - diffusion delay
• gstab - gradient recovery delay

Flags

• delflag - value 'y' turns on the "diffusion" part of the pulse sequence, 'n' - turns it into a one pulse 1D experiment
• wet - value 'y' turns on Wet water suppression
• satmode - value 'y' turns presaturation on

References

1. Pelta, Michelle D and Morris, Gareth A and Stchedroff, Marc J and Hammond, Stephen J. A one-shot sequence for high-resolution diffusion-ordered spectroscopy. Magnetic Resonance in Chemistry 40(13):S147--S152, 2002. BibTeX [hammond02]

2. Pelta, Michelle D and Barjat, Hervé and Morris, Gareth A and Davis, Adrian L and Hammond, Stephen J. Pulse sequences for high-resolution diffusion-ordered spectroscopy (HR-DOSY). Magnetic Resonance in Chemistry 36(10):706--714, 1998. BibTeX [hammond98]

3. Wu, DH and Chen, AD and Johnson, CS. An improved diffusion-ordered spectroscopy experiment incorporating bipolar-gradient pulses. Journal of Magnetic Resonance, Series A 115(2):260--264, 1995. BibTeX [bppste]