Truncation artifact simulating motion in magnetic resonance imaging

140

MAGNETIC

RESONANCE

IHAGING:

VOLUME 4,

NUMGER 2,

1986

SltlULATOR ll’lAGlNG MAGNETIC RESONANCE INSTRUCTION IN PULSE SEQUENCE SELECTION

FOR

Rhodes M .Lufkin R. Keen R. Quinn J, Blenn W, Hanafee W Multiplanar

Diegnostic Imaging( MR JQ,WG)

and UCLA School of Medicine( RL ,RK, WH)

An ordinary desk top microcomputer wes programmed to simulate MR images for any specified spin echo pulse sequence. Model pixel maps of proton density, Tl , and T2 relaxation times were created from published values for different regions of human anatomy. images were then generated and displayed from the model maps and user specified pulse sequence parameters(TR, TE) in less than 30 seconds per image Models for various pathological conditions including calcification. subacute hemorrhage, porencephaly, fat, end multiple sclerosis were superimposed on the imfqes of normal anatomy to create unknown cases. The effect of pulse sequence selection on the contrast of normal structures as Well as the pethologlcal conditions is easily demonstrated with these devices. The use of simulated images is an excellent technique to provide experience in pulse sequence selection. Low cost micraxxnouters can orovide adequate image detail end reasonable imaoe calculation and disola/ time iing purposes Fig. 1. Simulated SE/I 50120 image of a patient with a subacute hemorrhage in the left cerebral hemisphere. Fig. 2. Simulated SE/ 1500/56 image of a patient with basal ganglia calcification.

TRUNCATION ARTIFACT RESONANCE IMAGING E Pusey, R Lufkin,

D Stark,

SIMULATING

R Brown, B Leikind,

MOTION

IN

MAGNETfC

W Hanafee

UCLA School of Medicrne( RL,EP ,RB ,EL .WH), and Massachusetts General Hosoital( DS) A ringing artifact similar in appearance to ar!lfact produ,w w!:h patient motion but unrelated to movement is present on megne!ic resonance images The phenomenon was lnvestlgated usmg doped water phantoms and normal volunteers Ail images were obtained on 0 3 Tesla permanent and 0 6 Tesla superconducting MR imagers with varying phase and frequency sampling rates. The artifaci ;dpyeared in both the phase and frequency axes as paraliel lines or rmomg adjacent to borders or tissue discontinuities. Increasing the sampling rates from 125 to i 12 re%ltd In higher frequency ringing and more rapId dropoff In ampil!lJ& Law pass digita; filterlng alsodiminished the rmgmg at the expenseof ime detail The truncation of the mfmite c terms used ior most WR imagmg Four rer series necessary to encode edges to the 12B to 5 1L produces the artifact It IS important to recognize this cornman artifact of the 2D-FT techntatie and not mistake I! for patlent motion or patho!qy