Implementation of helical computed tomography in magnetic resonance imaging.
OBJECTIVE
To provide a rapid sequence for volumetric imaging of large fields of view.


METHODS
The volumetric imaging principles of x-ray helical computed tomograpy (CT) were implemented here on an MRI scanner. However, using the advantages offered by MRI, spiral trajectories in K-space were incorporated to make the helical scan more efficient. Thus, data acquisition and interpolations were conducted in K-space and images reconstructed by gridding and applying the inverse Fourier transform. The rapid spiral helical (RASH) imaging method was evaluated by computer simulations, by scanning phantoms and an in vitro heart, and by comparison to conventional multislice interleaved spirals (MSIS) imaging.


RESULTS
A significant time saving (61.4% to 85.9%) relative to MSIS was achieved without significant degradation in image quality. Volume assessment and in-plane resolution by RASH were almost identical to the MSIS pulse sequence. The corresponding increase in effective slice width was estimated to range (for the values studied here) from 1.31 to 2.5 according to the selection of the helical pitch and the slice thickness used for imaging.


CONCLUSIONS
The suggested method offers the advantages provided by x-ray helical CT and can be useful in MRI volumetric scanning of large objects.
D000818:Animals; D003198:Computer Simulation; D005583:Fourier Analysis; D006321:Heart / Q000033:anatomy & histology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D012756:Sheep; D036542:Tomography, Spiral Computed / Q000379:methods*