Faculty Bibliography

BACKGROUND AND PURPOSE: The measurement of relative cerebral blood volume (rCBV) and the volume transfer constant (K(trans)) by means of dynamic contrast-enhanced (DCE) perfusion MR imaging (pMRI) can be useful in characterizing brain tumors. The purpose of our study was to evaluate the utility of these measurements in differentiating typical meningiomas and atypical meningiomas. METHODS: Fifteen patients with pathologically confirmed typical meningiomas and seven with atypical meningiomas underwent conventional imaging and DCE pMRI before resection. rCBV measurements were calculated by using standard intravascular indicator dilution algorithms. K(trans) was calculated from the same DCE pMRI data by using a new pharmacokinetic modeling (PM) algorithm. Results were compared with pathologic findings. RESULTS: Mean rCBV was 8.02 +/- 4.74 in the 15 typical meningiomas and 10.50 +/- 2.1 in the seven atypical meningiomas. K(trans) was 0.0016 seconds(-1) +/- 0.0012 in the typical group and 0.0066 seconds(-1) +/- 0.0026 in the atypical group. The difference in K(trans) was statistically significant (P <.01, Student t test). Other parameters generated with the PM algorithm (plasma volume, volume of the extravascular extracellular space, and flux rate constant) were not significantly different between the two tumor types. CONCLUSION: DCE pMRI may have a role in the prospective characterization of meningiomas. Specifically, the measurement of K(trans) is of use in distinguishing atypical meningiomas from typical meningiomas

We investigated how frequently the imaging procedure we use immediately prior to radiosurgery--triple-dose gadolinium-enhanced MR performed with the patient immobilized in a nonrelocatable head frame and 1-mm-thick MPRAGE (magnetization-prepared rapid gradient echo) images (SRS3xGado)-identifies previously unrecognized cerebral metastases in patients initially imaged by conventional MR with single-dose gadolinium (1xGado). Between July 1998 and July 2000, the diagnoses established for 47 patients who underwent radio-surgical procedures for treatment of cerebral metastases at The Gamma Knife Center of New York University were based initially on the 1xGado protocol. In July 1998, we began using SRS3xGado as our routine imaging protocol in preparation for targeting lesions for radio-surgery, using triple-dose gadolinium and acquisition of contiguous 1-mm Tl-weighted axial images. Because our SRS3xGado scans sometimes unexpectedly revealed additional metastases, we sought to learn how frequently the initial 1xGado scans would underestimate the number of metastases. We therefore reviewed the number of brain metastases identified on the SRS3xGado studies and compared the results to the number found by the 1xGado protocol, which had initially identified the brain metastases. Additional metastases, ranging from 1 to 23 lesions per patient, were identified on the SRS3xGado scan in 23 of 47 patients (49%). In 57% of the 23 patients, only one additional lesion was identified. The mean time interval between the 1xGado and the SRS3xGado scans was 20.6 days (range, 4-83 days), and the number of additional lesions detected and the time interval between two scans were negatively correlated (-0.11). The number of lesions detected on the SRS3xGado was associated only with the number of lesions on the 1xGado and not with any other patient or tumor pretreatment characteristics such as age, gender, largest tumor volume on the 1xGado, or number of days between the 1xGado and the SRS3xGado or prior surgery. The identification of additional lesions with SRS3xGado MR may have implications for patients who are treated with stereotactic radiosurgery alone (without whole-brain irradiation) with single-dose gadolinium imaging, in that unidentified lesions may go untreated. As a result of these findings we continue to use and advocate SRS3xGado scans for radiosurgery

The incidence and character of neurological deficits following resection of glial neoplasms localized to the Heschl gyrus are currently unknown. In this series, the authors report the clinical presentation, management, and postoperative course of three patients with right hemisphere Heschl gyrus gliomas, one of whom developed difficulty with music production and comprehension postoperatively. Resection of right hemisphere Heschl gyms gliomas can result in deficits involving music comprehension. Preliminary evidence suggests that when these deficits occur, they may be transient in nature

BACKGROUND: Choroid plexus papillomas (CPPs) are rare intracranial neoplasms, especially in the third ventricle. We report a patient with a posterior third ventricular CPP extending into the pineal that radiographically and clinically presented as a pineal region lesion. CASE DESCRIPTION: In a 51-year-old female with headache and upward gaze impairment radiological examination showed a mass in the pineal region obstructing the aqueduct of Sylvius and causing hydrocephalus. After ventriculoperitoneal shunting the tumor was approached through the infratentorial-supracerebellar approach and pathological examination revealed a typical CPP. CONCLUSIONS: This case represents an unusual presentation of an intracranial CPP. This entity should be considered an extremely rare cause of a lesion in the pineal region

BACKGROUND AND PURPOSE: In evaluating intracranial tumors, a safe low-cost alternative that provides information similar to that of digital subtraction angiography (DSA) may be of interest. Our purpose was to determine the utility and limitations of a combined MR protocol in assessing (neo-) vascularity in intracranial tumors and their relation to adjacent vessels and to compare the results with those of DSA. METHODS: Twenty-two consecutive patients with an intracranial tumor who underwent preoperative stereoscopic DSA were examined with contrast-enhanced dynamic T2*-weighted perfusion MR imaging followed by a T1-weighted three-dimensional (3D) MR study (volumetric interpolated brain examination [VIBE]). The maximum relative cerebral blood volume (rCBV) of the tumor was compared with tumor vascularity at DSA. Critical vessel structures were defined in each patient, and VIBE images of these structures were compared with DSA findings. For full exploitation of the 3D data sets, maximum-intensity projection algorithms reconstructed in real time with any desired volume and orientation were used. RESULTS: Tumor blush scores at DSA were significantly correlated with the rCBV measurements (r = 0.75; P <.01, Spearman rank correlation coefficient). In 17 (77%) patients, VIBE provided all relevant information about the venous system, whereas information about critical arteries were partial in 50% of the cases and not relevant in the other 50%. CONCLUSION: A fast imaging protocol consisting of perfusion MR imaging and a volumetric MR acquisition provides some of the information about tumor (neo-) vascularity and adjacent vascular anatomy that can be obtained with conventional angiography. However, the MR protocol provides insufficient visualization of distal cerebral arteries

BACKGROUND: For radiobiological experiments using the Gamma Knife model B, we constructed a stereotactic device to irradiate rat and mouse brains and verify the absorbed dose at the target using thermoluminescence dosimetry and a head phantom. METHODS: Our stereotactic device is primarily designed for rats using the fixation principles of a stereotactic atlas. A head-fixation adapter for a mouse was constructed to enable targeted irradiation of mouse brains. We built simple phantoms to simulate rat and mouse heads. We placed thermoluminescent dosimeters at various positions on the phantom for dose measurements. Dose planning employed the Leksell Gamma Plan version 4.11 software, assuming a spherical skull geometry for all calculations. FINDINGS: The measurements demonstrated that the actual absorbed dose agreed with our calculations within the errors of thermoluminescence dosimetry and the accuracy of our irradiation technique and dose calculations. INTERPRETATION: This device provides an accurate method for irradiating rat and mouse brains using the Gamma Knife model B