Dynamic susceptibility contrast perfusion imaging in biopsy-proved adult medulloblastoma

Prediction of intraoperative blood loss in pediatric posterior fossa tumors by neuroradiological evaluation: preliminary study

BACKGROUND

Hemorrhage management is crucial for surgical resection of pediatric posterior-fossa tumors (PPFTs). Tumor volume and vascularity on preoperative magnetic resonance imaging (MRI) can help predict and control intraoperative blood loss (IBL). The present study aimed to assess the correlation between MRI features and IBL in PPFTs.

METHODS

Eleven patients treated for PPFTs at our hospital using the transcerebellomedullary fissure approach were enrolled, including five (45.5%) males and six (54.5%) females, with a median age of 10 (range, 4-16) years. Nine patients with medulloblastoma, one with ependymoma, and one with atypical teratoid/rhabdoid tumor were included. Using susceptibility-weighted imaging-based intratumoral susceptibility signal (ITSS) grade as an index of tumor vascularity, we performed univariate analysis of the association of degree of vascularity (ITSS grade 0-2 vs. 3) and multivariate analysis of IBL.

RESULTS

Univariate analysis showed that the high vascularity group (ITSS grade 3) had significantly larger tumor volume (p = 0.009) and higher IBL (p = 0.004). In multivariate analysis of age, tumor volume, ITSS grade, cerebral blood volume, and extent of resection, tumor volume was the only significant factor (p = 0.001); however, ITSS grade was also positively associated with IBL (p = 0.074).

CONCLUSION

In this study, tumor volume and vascularity of PPFTs were strongly correlated, and tumor volume was the sole factor significantly associated with IBL. This study suggests that ITSS grade and tumor volume collaboratively influence IBL in surgical resection of PPFTs. IBL should be assessed based on MRI features, and suitable treatment strategies should be established.

Medulloblastomas in adolescents and adults - Can the pediatric experience be extrapolated?

Adult medulloblastomas are orphan diseases that differ from their pediatric counterpart. Most are classified as classic or desmoplastic and fall in the SHH subgroup, mainly with loss-of-function mutations in PTCH1 and some by TP53-mutation due to underlying germline mutation. Activation of the WNT pathway is sporadic, although underlying Turcot syndrome may be present. One-third of tumors are issued from group 4. Most adult studies are small non-randomized retrospective heterogeneous studies performed at a single center with short follow-up. Standard craniospinal irradiation followed by maintenance chemotherapy (CCNU, cisplatin-vincristine) results in a 4-year event-free survival (EFS) and overall survival (OS) of 68% and 89% respectively in standard-risk adults, and in a 4-year EFS and OS of 50% and 90%, respectively in high-risk adults. Several pooled analyses point out the potential role of chemotherapy in adults. The feasibility of pediatric protocols in adults is sometimes hampered because of blood and peripheral nerve toxicity. In the near future, subgroups of medulloblastomas may be treated by personalized therapies. With prolonged follow-up, adults fare worse. Long-term sequelae and second line treatment are not well defined in adults. Prospective studies are ongoing to define optimal first-line and relapse treatments.

Imaging features of medulloblastoma: Conventional imaging, diffusion-weighted imaging, perfusion-weighted imaging, and spectroscopy: From general features to subtypes and characteristics

Medulloblastoma is a frequent high-grade neoplasm among pediatric brain tumours. Its classical imaging features are a midline tumour growing into the fourth ventricle, hyperdense on CT-scan, displaying a hypersignal when using diffusion-weighted imaging, with a variable contrast enhancement. Nevertheless, atypical imaging features have been widely reported, varying according to the age of the patient, and histopathological subtype. In this study, we review the classical and atypical imaging features of medulloblastomas, with emphasis on advanced MRI techniques, histopathological and molecular subtypes and characteristics, and follow-up modalities.

Consistency of normalized cerebral blood volume values in glioblastoma using different leakage correction algorithms on dynamic susceptibility contrast magnetic resonance imaging data without and with preload

BACKGROUND AND PURPOSE

Several leakage correction algorithms for dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI)-based cerebral blood volume (CBV) measurement have been proposed, and combination with a preload of contrast agent is generally recommended. A single bolus application scheme would largely simplify and facilitate standardized clinical applications, while reducing contrast agent (CA) dose. The aim of this study was, therefore, to investigate whether appropriate leakage correction redundantizes prebolus application by comparing normalized DSC-based CBV (nCBV) measures of two consecutive CA boli.

MATERIALS AND METHODS

Twenty-seven patients with suspected glioblastoma (WHO-grade-IV) underwent DSC-MRI during two consecutive boli of Gd-based CA. Four variants of two post-processing leakage correction techniques were compared with respect to nCBV in contrast enhancing tumor tissue. First, a reference curve approach with first pass and full integration of corrected ΔR2*(t), and second, a deconvolution-based approach using singular value decomposition (SVD) with a standard noise-dependent cutoff or Tikhonov regularization.

RESULTS

Compared to respective uncorrected values, all leakage correction techniques increased nCBV for data acquired without prebolus, while there was no consistent trend for data acquired with prebolus. The best agreement between corrected nCBV values in contrast enhancing tumor, obtained in the same patients without and with prebolus, respectively, was obtained for the reference curve-based correction approach with either first pass or full integration.

CONCLUSION

The reference curve-based leakage correction approach with integration-based nCBV calculation yielded a high accordance between nCBV values without and with prebolus, respectively. Thus, it appears possible to obtain valid nCBV in glioblastoma with a single CA injection.

[Value of diffusion-weighted imaging, 1H-magnetic resonance spectroscopy and 3D whole-brain arterial spin labeling in the diagnosis of medulloblastoma]

OBJECTIVE

To explore the value of diffusion-weighted imaging (DWI), ¹H-magnetic resonance spectroscopy (1H-MRS) and 3D whole-brain arterial spin labeling (3D ASL) in the diagnosis of medulloblastoma in the posterior cranial fossa.

METHODS

The magnetic resonance imaging (MRI) findings of 16 patients with pathologically confirmed medulloblastoma in the posterior cranial fossa were analyzed retrospectively. All the patients were examined with plane and enhanced brain MRI scans; 5 patients also underwent examinations with DWI, 12 with MRS, and 5 with 3D ASL.

RESULTS

Medulloblastomas were found in the vermis and the fourth ventricle in 9 cases, in the cerebellar hemisphere in 5 cases, and in the cerebellopontine angle in 1 case; in 1 case multiple lesions were detected. The tumors showed iso-intense or slightly hypo-intense signals on T₁WI, and iso-intense or hyper-intense signals on T₂WI and FLAIR. The lesions showed high signals in DWI and low signals in ADC. Intra-lesion cysts were common (n=12), and calcification and bleeding were rarely seen. Mild patchy enhancement (n=6) or significant enhancement (n=10) was seen after contrast agent administration. Obstructive hydrocephalus was found in 12 cases and the subarachnoid space was involved in 3 cases. In all the 12 patients receiving MRS examination, high Cho and low NAA were found with significantly increased Cho/Cr (≥3.5) and Cho/NAA (≥4.0) ratios; Tau peak was seen in 8 cases, and Lip peak was found in 4 cases. All the 5 patients receiving 3D ASL examination showed decreased cerebral blood flow (CBF).

CONCLUSION

The characteristic features of medulloblastomas in DWI, MRS and 3D ASL offer assistance to the diagnosis of atypical medulloblastoma.