Dynamic spin-echo imaging: theoretical assessment and implementation.
A spin-echo method for obtaining dynamic magnetic resonance (MR) images is described. The method combines the RARE (rapid acquisition with relaxation enhancement) pulse sequence with a data acquisition scheme in which only a centric fraction of the raw data is sampled to increase the time resolution of the dynamic images. The missing high-resolution data are supplied from reference images. By these means, an effective time resolution of about 10 seconds per image is achieved, which is suitable for diagnostic assessment of contrast enhancement procedures. A promising clinical application is contrast-enhanced MR imaging of the pituitary. Although the resolution of small objects in this size range is potentially degraded, this shortcoming is compensated for with use of variable refocusing flip angles. In the context of pituitary imaging, the centric 30%-40% of the raw data is shown to be the optimal fraction to acquire for the low-resolution dynamic images. Ten patients with previous history of pituitary disease have been imaged with dynamic and conventional spin-echo techniques. In six of these patients, an equivalent diagnosis was reached with dynamic and conventional images, while in two, only the dynamic images showed the lesion; in the final two patients, only the conventional images showed the lesion.
Bishop
J
J
Department of Medical Biophysics, University of Toronto, Ontario, Canada.
Henkelman
R M
RM
Plewes
D B
DB
D000236:Adenoma / Q000175:diagnosis / Q000473:pathology; D000465:Algorithms; D002712:Chlorides / Q000737:chemistry; D003287:Contrast Media; D004338:Drug Combinations; D005682:Gadolinium; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D017895:Manganese Compounds / Q000737:chemistry; D008536:Meglumine; D008962:Models, Theoretical; D009942:Organometallic Compounds; D004369:Pentetic Acid / Q000031:analogs & derivatives; D010900:Pituitary Diseases / Q000175:diagnosis / Q000473:pathology; D010902:Pituitary Gland / Q000033:anatomy & histology; D010911:Pituitary Neoplasms / Q000175:diagnosis / Q000473:pathology; D012815:Signal Processing, Computer-Assisted
D002712:Chlorides; D003287:Contrast Media; D004338:Drug Combinations; D017895:Manganese Compounds; D009942:Organometallic Compounds; D008536:Meglumine; D004369:Pentetic Acid; D005682:Gadolinium; D019786:Gadolinium DTPA; C025340:manganese chloride