Imaging after GliaSite brachytherapy: prognostic MRI indicators of disease control and recurrence.

PURPOSE: In this study, we analyzed the magnetic resonance imaging (MRI) changes in patients after GliaSite treatment and characterized the prognostic MRI indicators in these patients. METHODS AND MATERIALS: A total of 25 patients with recurrent glioblastoma multiforme were treated with the GliaSite Radiation Therapy System. Patients at the Johns Hopkins Hospital with recurrent glioblastoma multiforme underwent surgical resection followed by GliaSite balloon implantation. Available MRI scans for 20 patients were obtained throughout the post-GliaSite treatment course. These were reviewed and analyzed for prognostic significance. RESULTS: After GliaSite treatment, all patients developed some degree of T(1)-weighted contrast and T(2)-weighted hyperintensity around the resection cavity. The development of enhancement on T(1)-weighted contrast-enhanced imaging and the size of these lesions, in the absence of increasing T(2)-weighted hyperintensity, before clinical progression was not associated with decreased survival. Patients with T(1)-weighted enhancement >1 cm had a median survival of 13.6 months and those with T(1)-weighted lesions

Correlation of hindbrain CSF flow and outcome after surgical decompression for Chiari I malformation.

OBJECTIVE: Many patients with symptomatic Chiari I malformation experience symptom recurrence after surgical decompression. Improved radiographic predictors of outcome are needed to better select patients most likely to benefit from surgical intervention. We examined whether ventral or dorsal cerebrospinal fluid (CSF) flow dynamics assessed by cine phase-contrast MRI scans could predict response to posterior fossa decompression for Chiari I malformation. METHODS: Forty-four consecutive pediatric patients undergoing pre-operative cine phase-contrast MRI followed by posterior fossa decompression for Chiari I malformation were retrospectively reviewed. The association of pre-operative ventral or dorsal CSF flow abnormalities at the foramen magnum with symptom-free survival after surgical decompression was assessed via Kaplan-Meier plots and log-rank analysis. RESULTS: Mean +/- SD age at time of surgery was 8 +/- 6 years. Sixteen (36%) patients demonstrated decreased CSF flow dorsal to the cervico-medullary brainstem alone. Fourteen (32%) patients demonstrated abnormal CSF flow both ventral and dorsal to the cervico-medullary brainstem. Fourteen (32%) had normal hindbrain CSF flow. Overall, 13 (30%) patients experienced some degree of symptom recurrence by last follow-up (mean of 27 +/- 16 months post-operatively). Symptom recurrence did not differ as a function of degree of tonsilar ectopia (p = 0.55). Abnormal CSF flow dorsal to the cervico-medullary brainstem was not associated with symptom recurrence after surgical decompression (p = 0.10). However, combined pre-operative ventral and dorsal CSF flow abnormality was associated with a significant reduction (2.6-fold) in the risk of post-operative symptom recurrence (p < 0.05). Only one patient (7%) with pre-operative ventral and dorsal CSF flow pathology experienced symptom recurrence 3.5 years after surgery versus 12 (40%) patients without ventral CSF flow pathology. There were otherwise no differences in baseline clinical, radiological, or operative variables between patients with abnormal versus normal ventral CSF flow. CONCLUSION: The presence of decreased CSF flow both ventral and dorsal to the cervico-medullary brainstem was associated with improved response to hindbrain decompression for Chiari I malformation in children. Cine phase-contrast MRI may be a useful tool for surgical risk stratification and identifying patients that may be optimal surgical candidates. Combined ventral and dorsal hindbrain CSF flow pathology may better predict response to posterior fossa decompression compared to dorsal CSF flow pathology alone.

Proton magnetic resonance spectroscopic imaging to differentiate between nonneoplastic lesions and brain tumors in children.

PURPOSE: To investigate whether in vivo proton magnetic resonance spectroscopic imaging (MRSI) can differentiate between 1) tumors and nonneoplastic brain lesions, and 2) high- and low-grade tumors in children. MATERIALS AND METHODS: Thirty-two children (20 males and 12 females, mean age = 10 +/- 5 years) with primary brain lesions were evaluated retrospectively. Nineteen patients had a neuropathologically confirmed brain tumor, and 13 patients had a benign lesion. Multislice proton MRSI was performed at TE = 280 msec. Ratios of N-acetyl aspartate/choline (NAA/Cho), NAA/creatine (Cr), and Cho/Cr were evaluated in the lesion and the contralateral hemisphere. Normalized lesion peak areas (Cho(norm), Cr(norm), and NAA(norm)) expressed relative to the contralateral hemisphere were also calculated. Discriminant function analysis was used for statistical evaluation. RESULTS: Considering all possible combinations of metabolite ratios, the best discriminant function to differentiate between nonneoplastic lesions and brain tumors was found to include only the ratio of Cho/Cr (Wilks' lambda, P = 0.012; 78.1% of original grouped cases correctly classified). The best discriminant function to differentiate between high- and low-grade tumors included the ratios of NAA/Cr and Cho(norm) (Wilks' lambda, P = 0.001; 89.5% of original grouped cases correctly classified). Cr levels in low-grade tumors were slightly lower than or comparable to control regions and ranged from 53% to 165% of the control values in high-grade tumors. CONCLUSION: Proton MRSI may have a promising role in differentiating pediatric brain lesions, and an important diagnostic value, particularly for inoperable or inaccessible lesions.