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: Sevente en patients with a known or suspected brain tumor were studied with an echo planar inversion recovery imaging sequence using 10 different in version times. Double injections of Gd chelate (0.1 mmol/ kg + 0.2 mmo l/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 1 121 +/- 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 sh ortened 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 tumor s showed considerable variation and remained, on average, relatively l ong compared to white matter. This should be taken into account when d eciding which pulse sequences, imaging parameters, and contrast agent doses are optimal for brain tumor imaging.