UTILITY OF RELATIVE CEREBRAL BLOOD-VOLUME MAPPING DERIVED FROM PERFUSION MAGNETIC-RESONANCE-IMAGING IN THE ROUTINE FOLLOW-UP OF BRAIN-TUMORS

It was recently demonstrated that imaging of brain tumors by relative cerebral blood volume (CBV) maps reconstructed from dynamic magnetic r esonance (MR) data provide similar diagnostic information compared to positron emission tomography (PET) or Tl-201 single-photon emission co mputerized tomography (Tl-201-SPECT) scans. The authors used relative CBV mapping for routine follow-up evaluation of patients with brain tu mors and compared its sensitivity to diagnostic MR imaging, Tl-201-SPE CT and clinical assessment. Fifty-nine patients were prospectively fol lowed using 191 concomitant studies of dual section relative CBV maps, MR imaging, Tl-201-SPECT, and neurological evaluations. Studies were repeated every 2 to 3 months (median three evaluations/patient). The r elative CBV maps were graded as relative CBV 0 to 3, where Grades 3 an d 4 are indicative of proliferating tumors (four = rapid leak). There were 44 high-grade and 15 low-grade tumors followed during treatment. During the follow-up period a change in relative CBV grade was observe d in 56% of the patients, revealing an increasing grade in 72% of them . The rapid leak phenomenon was detected in 35% of all studies and in 81% of those with a worsening relative CBV grade. Tumor progression wa s detected earlier by relative CBV maps as follows: earlier than MR im aging in 32% of the studies (earlier by a median of 4.5 months; p < 0. 01): earlier than Tl-201-SPECT in 63% (median 4.5 months; p < 0.01), a nd earlier than clinical assessment in 55% (median 6 months; p < 0.01) . In 82% of studies with positive MR imaging but negative Tl-201-SPECT , the lesions were smaller than 1.5 cm. The relative CBV maps clearly delineated the appearance of rapid leak in these lesions. Routine use of relative CBV maps that can be implemented on any high-field MR unit and added to the regular MR evaluation provides useful functional inf ormation in patients with brain tumors. When used as an adjunct follow -up evaluation it proved more sensitive than the other modalities for early prediction of tumor growth. It is very sensitive to small region al changes, unlike functional imaging such as PET or SPECT scans. Base d on previous experience with 76 regional CBV studies, the authors con clude that regional CBV mapping correlates with active tumor and it ma y separate enhancing scar and radiation injury from infiltrative tumor . A new effect named the rapid leak phenomenon was also observed; this phenomenon, as identified on the regional CBV maps, correlates with h igh malignancy.