© 2003 by Society
© 2003 by the Society forNeuro-Oncology
Importance of MR technique for stereotactic radiosurgery
Departments of Radiation Oncology (B.R.D., K.H.,J.S.C.) and Neurosurgery (J.G.G., E.A.K., J.C.)and Division of Biostatistics (J.D.G., V.M.), New YorkUniversity Medical Center, New York, NY 10016; NassauRadiologic Group (S.C.R.), Garden City, NY 11530
2 Address correspondence to Bernadine Donahue, Department of Radiation Oncology,New York University Medical Center, 566 First Avenue, Room HC107, New York, NY10016(bernadine.donahue{at}med.nyu.edu).
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Abstract |
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We investigated how frequently the imaging procedure we use immediatelyprior to radiosurgery— triple-dose gadolinium-enhanced MR performed withthe patient immobilized in a nonrelocatable head frame and 1-mm-thick MPRAGE(magnetization-prepared rapid gradient echo) images(SRS3xGado)—identifies previously unrecognized cerebral metastases inpatients initially imaged by conventional MR with single-dose gadolinium(1xGado). Between July 1998 and July 2000, the diagnoses established for 47patients who underwent radio-surgical procedures for treatment of cerebralmetastases at The Gamma Knife Center of New York University were basedinitially on the 1xGado protocol. In July 1998, we began using SRS3xGado asour routine imaging protocol in preparation for targeting lesions forradiosurgery, using triple-dose gadolinium and acquisition of contiguous 1-mmT1-weighted axial images. Because our SRS3xGado scans sometimes unexpectedlyrevealed additional metastases, we sought to learn how frequently the initial1xGado scans would underestimate the number of metastases. We thereforereviewed the number of brain metastases identified on the SRS3xGado studiesand compared the results to the number found by the 1xGado protocol, which hadinitially identified the brain metastases. Additional metastases, ranging from1 to 23 lesions per patient, were identified on the SRS3xGado scan in 23 of 47patients (49%). In 57% of the 23 patients, only one additional lesion wasidentified. The mean time interval between the 1xGado and the SRS3xGado scanswas 20.6 days (range, 4 - 83 days), and the number of additional lesionsdetected and the time interval between two scans were negatively correlated(-0.11). The number of lesions detected on the SRS3xGado was associated onlywith the number of lesions on the 1xGado and not with any other patient ortumor pretreatment characteristics such as age, gender, largest tumor volumeon the 1xGado, or number of days between the 1xGado and the SRS3xGado or priorsurgery. The identification of additional lesions with SRS3xGado MR may haveimplications for patients who are treated with stereotactic radiosurgery alone(without whole-brain irradiation) with single-dose gadolinium imaging, in thatunidentified lesions may go untreated. As a result of these findings wecontinue to use and advocate SRS3xGado scans for radiosurgery.
Received January 29, 2003; Accepted June 17, 2003