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Double Angle method(s)

Double Angle technique

NeuroPoly Lab, Polytechnique Montreal, Quebec, Canada

The Double Angle method (DA or DAM) is a class of B1 mapping technique swherein two RF pulses at flip angles α and 2α are applied to a pulse sequence, and the ratio of the images are compared to expected output to produce a B1 map. Several main pulse sequences (Figure 4.1]) have been called the double angle method in the literature, and both have their own equations describing the relationship between the expected images and B1. In this chapter, we’ll mostly explore there the α-180 method (Figure 4.1]), and then briefly explain the other method and its similarities/differences.

Pulse sequences for double angle methods. A) Double angle method using a gradiend echo. B) Double angle method using a 180 degree refocusing pulse. C) Double angle method using a 2\alpha refocusing pulse, acquired with two values \alpha_{1} and \alpha_{2} such that \alpha_{2}=2\alpha_{1}.

Figure 4.1:Pulse sequences for double angle methods. A) Double angle method using a gradiend echo. B) Double angle method using a 180 degree refocusing pulse. C) Double angle method using a 2α2\alpha refocusing pulse, acquired with two values α1\alpha_{1} and α2\alpha_{2} such that α2=2α1\alpha_{2}=2\alpha_{1}.

Double Angle Methods
Transmit and Receive RF field amplitudes
Double Angle Methods
Gradient echo and 180 degree spin echo method