[The heterogeneity of blood flow on magnetic resonance imaging: a biomarker for grading cerebral astrocytomas].
OBJECTIVE
To study whether the histograms of quantitative parameters of perfusion in MRI obtained from tumor volume and peritumor volume make it possible to grade astrocytomas in vivo.


METHODS
We included 61 patients with histological diagnoses of grade II, III, or IV astrocytomas who underwent T2*-weighted perfusion MRI after intravenous contrast agent injection. We manually selected the tumor volume and peritumor volume and quantified the following perfusion parameters on a voxel-by-voxel basis: blood volume (BV), blood flow (BF), mean transit time (TTM), transfer constant (K(trans)), washout coefficient, interstitial volume, and vascular volume. For each volume, we obtained the corresponding histogram with its mean, standard deviation, and kurtosis (using the standard deviation and kurtosis as measures of heterogeneity) and we compared the differences in each parameter between different grades of tumor. We also calculated the mean and standard deviation of the highest 10% of values. Finally, we performed a multiparametric discriminant analysis to improve the classification.


RESULTS
For tumor volume, we found statistically significant differences among the three grades of tumor for the means and standard deviations of BV, BF, and K(trans), both for the entire distribution and for the highest 10% of values. For the peritumor volume, we found no significant differences for any parameters. The discriminant analysis improved the classification slightly.


CONCLUSIONS
The quantification of the volume parameters of the entire region of the tumor with BV, BF, and K(trans) is useful for grading astrocytomas. The heterogeneity represented by the standard deviation of BF is the most reliable diagnostic parameter for distinguishing between low grade and high grade lesions.
Servicio de Radiología, Hospital de Manises, Manises, Valencia, España. Electronic address: ajrevert@telefonica.net.
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Revert Ventura
Servicio de Radiología, Hospital Quirón Valencia, Valencia, España.
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Sanz Requena
Servicio de Radiología, Hospital Quirón Valencia, Valencia, España; Servicio de Radiología, Hospital Universitario y Politécnico La Fe, Valencia, España.
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Martí-Bonmatí
Servicio de Radiología, Hospital de Manises, Manises, Valencia, España.
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Y
Pallardó
Servicio de Radiología, Hospital de la Ribera, Alzira, Valencia, España.
J
J
Jornet
Servicio de Oncología, Hospital de la Ribera, Alzira, Valencia, España.
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C
Gaspar
D000328:Adult; D000368:Aged; D001254:Astrocytoma / Q000098:blood supply / Q000473:pathology* / Q000503:physiopathology*; D001932:Brain Neoplasms / Q000098:blood supply / Q000473:pathology* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D012189:Retrospective Studies