Analysis of magnetization transfer effects on T1-weighted spin-echo scans using a simple tissue phantom simulating gadolinium-enhanced brain lesions.
The purpose of this study was to analyze the effect of several magnetization transfer (MT) pulse and T1-weighted spin-echo (SE) sequence parameters on lesion-to-background contrast, using a simple tissue phantom emulating the T1 relaxation and MT properties of gadolinium-enhanced brain lesions. Eggbeaters (Nabisco Inc., East Hanover, NJ) liquid egg product was doped with gadolinium in six concentrations from .0 to 1.0 mmol and cooked. The gadolinium-doped egg phantom and normal volunteer brains were studied using an SE sequence with TE = 20 msec and high power, pulsed, off-resonance MT saturation. The effects of MT pulse frequency offset (1,000-6,000 Hz), sequence repetition time (TR = 500-1,000 msec, with MT power held constant), and slice-select flip angle (60-120 degrees) on the magnetization transfer ratio (MTR) and the simulated lesion-to-background contrast were determined at the different "intralesion" gadolinium concentrations. The MTR and lesion-to-background contrast of all materials were greatest at narrow MT pulse frequency offsets. There was in inverse relationship between gadolinium concentration and MTR and a positive correlation between the gadolinium concentration and lesion-to-background (L/B) contrast, a weak negative correlation between slice-select flip angle and L/B, and a negative correlation between TR and L/B. The relaxation properties and MT behavior of the egg phantom are close to that expected for enhancing brain lesions, allowing a rigorous analysis of several variables affecting lesion-to-background contrast for high MT power, T1-weighted SE sequences.
Finelli
D A
DA
Department of Radiology, MetroHealth Medical Center/Case Western Reserve University School of Medicine, Cleveland, OH 44109-1998, USA. DFINELLI@METROHEALTH.ORG
Hurst
G C
GC
Frank
H A
HA
Gullapali
R P
RP
Apicella
A
A
D000328:Adult; D001921:Brain / Q000033:anatomy & histology* / Q000473:pathology; D001927:Brain Diseases / Q000175:diagnosis*; D003287:Contrast Media; D005260:Female; D005682:Gadolinium; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D009942:Organometallic Compounds; D004369:Pentetic Acid / Q000031:analogs & derivatives; D019047:Phantoms, Imaging; D013997:Time Factors
D003287:Contrast Media; D009942:Organometallic Compounds; D004369:Pentetic Acid; C064925:gadodiamide; D005682:Gadolinium; D019786:Gadolinium DTPA