Abstract
Currently the accepted method for setting the correct rf power levels to achieve 90° and 180 ° rf pulses for Mr imaging is to peak the echo amplitude of a rf spin-echo sequence. The echo amplitude of this α-2α pulse sequence is proportional to sin3 (α) and has a relatively broad maximum. Recently another method for setting the rf flip angle by maximizing the ratio of the stimulated echo to the primary echo amplitudes (in a 3α sequence) demonstrated accuracy similar to that of the spin-echo method using a shorter repetition time. We present a new, more sensitive, and more accurate method for setting the correct rf power levels for 90° and 180° rf pulses. In this method, based upon the stimulated echo pulse sequence, we are able to accurately set the rf power to within ±0.1 dB by minimizing the signal amplitude of the third spin echo. This null method works for both selective and nonselective rf pulses of flip angle 90° or 180°, allowing the use to accurately adjust the relative amplitudes of the four rf pulse types within a single pulse sequence.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 16-24 |
| Number of pages | 9 |
| Journal | Magnetic Resonance in Medicine |
| Volume | 9 |
| Issue number | 1 |
| State | Published - 1989 |
| Externally published | Yes |
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging
- Radiological and Ultrasound Technology
Cite this
A method for correctly setting the rf flip angle. / Perman, W. H.; Bernstein, Matthew A; Sandstrom, J. C.
In: Magnetic Resonance in Medicine, Vol. 9, No. 1, 1989, p. 16-24.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - A method for correctly setting the rf flip angle
AU - Perman, W. H.
AU - Bernstein, Matthew A
AU - Sandstrom, J. C.
PY - 1989
Y1 - 1989
N2 - Currently the accepted method for setting the correct rf power levels to achieve 90° and 180 ° rf pulses for Mr imaging is to peak the echo amplitude of a rf spin-echo sequence. The echo amplitude of this α-2α pulse sequence is proportional to sin3 (α) and has a relatively broad maximum. Recently another method for setting the rf flip angle by maximizing the ratio of the stimulated echo to the primary echo amplitudes (in a 3α sequence) demonstrated accuracy similar to that of the spin-echo method using a shorter repetition time. We present a new, more sensitive, and more accurate method for setting the correct rf power levels for 90° and 180° rf pulses. In this method, based upon the stimulated echo pulse sequence, we are able to accurately set the rf power to within ±0.1 dB by minimizing the signal amplitude of the third spin echo. This null method works for both selective and nonselective rf pulses of flip angle 90° or 180°, allowing the use to accurately adjust the relative amplitudes of the four rf pulse types within a single pulse sequence.
AB - Currently the accepted method for setting the correct rf power levels to achieve 90° and 180 ° rf pulses for Mr imaging is to peak the echo amplitude of a rf spin-echo sequence. The echo amplitude of this α-2α pulse sequence is proportional to sin3 (α) and has a relatively broad maximum. Recently another method for setting the rf flip angle by maximizing the ratio of the stimulated echo to the primary echo amplitudes (in a 3α sequence) demonstrated accuracy similar to that of the spin-echo method using a shorter repetition time. We present a new, more sensitive, and more accurate method for setting the correct rf power levels for 90° and 180° rf pulses. In this method, based upon the stimulated echo pulse sequence, we are able to accurately set the rf power to within ±0.1 dB by minimizing the signal amplitude of the third spin echo. This null method works for both selective and nonselective rf pulses of flip angle 90° or 180°, allowing the use to accurately adjust the relative amplitudes of the four rf pulse types within a single pulse sequence.
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M3 - Article
VL - 9
SP - 16
EP - 24
JO - Magnetic Resonance in Medicine
JF - Magnetic Resonance in Medicine
SN - 0740-3194
IS - 1
ER -