th  - 1988 - 51st ENC Conference

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WED 9:25 ]
A STATIC NMR IMAGE OF A ROTATING OBJECT
S. Matsui,* K. Sekihara, H. Shiono, and H. Kohno
Central Research Laboratory, Hitachi, Ltd.
P.O. Box 2, Kokubunji, Tokyo 185, Japan.
An approach to imaging of a rotating object is described and demonstrated experimentally.
The principle is to apply field gradients such that the N~ signal from the
rotating object observed under the applied gradients results in appropriate scanning
in the spatial frequency domain, or the k space. The scanning pattern must cover the
k space as uniformly as possible. A static image of the rotating object can be obtained
from such a scanning pattern by suitable data processing.
When the whole object is moving, one must consider the field gradients in the
moving object frame, G (t), (not in the laboratory frame, ~R(t)). Then, the signal
scanning pattern in the object-frame k
r
space is
(t) = W gr (t')dt' = Y 0
r
I
Here, D_ is a transformation depending on the object motion. In the case of rotation
about t~e Y axis at an angular frequency~o s, D G is given by
(o t 0
DG= 0 s 1 0 s
t 0 cos ~ t .
-sin ~s s
In our preliminary two-dimensional (x,z) experiment, a gradient sequence in the
laboratory frame, B~(t) = (Go~O t, 0, Go), was applied to obtain a spiral scanning
K
pattern in the object frame, k ~t) = (~G~tsin~ t, 0, Y G^tcos~ t). A phantom,
r u V S
consisting of two water-filled capillaries (~l.5Sand 2 nnn 1.d.), was rotated at 180
Hz. The obtained proton image was consistent with the dimensions of the phantom.
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