The effect of paramagnetic contrast media on T1 relaxation times in brain tumors

Purpose: To study T1 relaxation times in brain tumors before and after paramagnetic contrast medium injection. Material and Methods: Seventeen patients with a known or suspected brain tumor were studied with an echo planar inversion recovery imaging sequence using 10 different inversion times. Double injections of Gd chelate (0.1 mmol/ kg + 0.2 mmol/kg were administered in 5 patients, and a single 0.2-mmol/kg dose in 12 patients. Results. After the 0.2-mmol/kg dose, T1 decreased from 1121 +/- 130 ms to 987 +/- 103 ms in gray matter (p < 0.001), and from 666 +/- 29 ms to 646 +/- 27 ms in white matter p < 0.001). Tumor T1 shortened from 1515 +/- 319 ms to 717 +/- 383 ms. After the 0.1-mmol/kg;g dose (n = 5), tumor TI decreased from 1116 +/- 261 ms to 793 +/- 202 ms and after the additional 0.2-mmol/kg dose it, decreased further to 526 +/- 141 ms. Conclusion: Postcontrast T1 relaxation times in tumors showed considerable variation and remained, on average, relatively long compared to white matter. This should be taken into account when deciding which pulse sequences, imaging parameters, and contrast agent doses are optimal for brain tumor imaging.