[Signal contamination problem in three-dimensional localization technique of MR spectroscopy--experiment and an analysis of patient data].
Signal contamination from the surrounding volume was studied using the ISIS sequence, a three-dimensional localization technique. In phantom experiments, contamination decreased with the increase of Tr, regardless of where the contamination originated from. In 52 localized liver spectra with a Tr of 2 sec, PCr contamination was estimated at 3 to 4%, and contamination of ATP signals from the surrounding liver tissue at less than 1%, because of the relatively short T1 of ATP in the liver. In the spectra of brain neoplasms obtained using the simultaneous double-volume selection technique, the PCr ratio in the tumor relative to the control area was high in low grade astrocytoma (0.80, n =8) and low in others (0.45, n = 11). Considering contamination and spectral noise, a PCr ratio of less than 0.4 does not strongly suggest the existence of PCr in tumors. Among 25 cases whose therapeutic processes were monitored by MRS, signal disappearance was observed in two cases in the localized spectra after therapy. In both of them, tumor necrosis was proved pathologically and correlated well with spectroscopic findings. It was found that the ISIS technique suppressed signal contamination to the level of several percents, providing spectra of acceptable quality through localization.
Imamura
K
K
Department of Radiology, St. Marianna University School of Medicine.
Fukui
A
A
Ashida
H
H
Saeki
M
M
Ito
T
T
Endo
M
M
Ishikawa
T
T
D006801:Humans; D007091:Image Processing, Computer-Assisted; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D009369:Neoplasms / Q000378:metabolism*; D013679:Technology, Radiologic