Radiology, Vol 180, 123-125, Copyright © 1991 by Radiological Society of North America
Impact of section doubling on lesion contrast
PE Sheldon, PA Rothschild, DM Kramer, JD Hale and L Kaufman
Radiologic Imaging Laboratory, University of California, San Francisco 94080.
Misregistration between section position and a feature of interest, such as
a lesion, can result in loss of contrast on magnetic resonance images.
Because the section direction typically has the poorest resolution,
reduction of section misregistration can improve lesion contrast. Lesions
occur at random sites; hence, to reduce misregistration, it is necessary to
repeat imaging with a small amount of offset. This is impractical.
Therefore, a reconstruction algorithm that yields offset sections was
implemented, in which sections were produced with a zero- and a
half-section shift. This algorithm was tested in 14 patients with multiple
sclerosis. As expected, because of randomness associated with section
placement relative to lesions, the half-shifted sections provided greater
contrast as often as the zero- shifted sections. The combined set improved
contrast significantly in 39% of lesions; improvement was greatest in
lesions with lesser contrast. Signal-to-noise ratios were not affected by
this process, which appears to be useful in magnetic resonance image
reconstruction.
