MR perfusion measurement of contrast uptaking lesions: consideration of T2* shortening due to interstitial contrast agent.
OBJECTIVE
In MR perfusion measurements of contrast uptaking lesions, time intensity curves are hampered by T 1 shortening as well as by the change of T 2 * due to interstitial contrast material (CM). Using double echo sequences, the influence of T 1 can be mathematically eliminated. For correction of the T 2 * influence an empirical algorithm using time-intensity-curves exclusively measured in the suspected lesion is proposed.


METHODS
The interstitial CM concentration is assumed to be proportional to the change of the intensity for T E = 0 or to the change of the relaxation rate DeltaR 1 respectively. The intravascular CM concentration is estimated from DeltaR 2 *. It is adjusted to zero for a time point sufficiently late after the bolus injection by subtraction of the interstitial concentration. This method was applied to double echo FLASH measurements on 15 pharyngeal tumors.


RESULTS
The proposed correction transforms the time dependence of the estimated intravascular CM concentration into a plausible course.


CONCLUSIONS
Double echo perfusion measurements can be corrected for the interstitial CM induced T 2 * shortening without additional measurements with proneness to errors. This does not necessarily improve the diagnostic value, since possibly "implied multivariate aspects" of uncorrected parameters (here: contrast uptake of the lesion is related to tumor neoangiogenesis as well) are eliminated.
Hietschold
V
V
Institut und Poliklinik für Radiologische Diagnostik, Universitätsklinikum Carl Gustav Carus, Dresden, Germany. Volker.Hietschold@mailbox.TU-Dresden.de
Kittner
T
T
Appold
S
S
Abolmaali
N
N
Laniado
M
M
D000465:Algorithms; D016477:Artifacts; D002294:Carcinoma, Squamous Cell / Q000098:blood supply / Q000175:diagnosis* / Q000532:radiotherapy; D003287:Contrast Media / Q000493:pharmacokinetics*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008833:Microcirculation / Q000503:physiopathology; D009389:Neovascularization, Pathologic / Q000175:diagnosis; D010101:Oxygen Consumption / Q000502:physiology / Q000528:radiation effects; D010610:Pharyngeal Neoplasms / Q000098:blood supply / Q000175:diagnosis* / Q000532:radiotherapy; D012680:Sensitivity and Specificity
D003287:Contrast Media