Lesions involving the fourth ventricle evaluated by CT and MR: a comparative study

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.

123I-metaiodobenzylguanidine single-photon emission computerized tomography in brain tumors - a preliminary study

OBJECTIVE

(123)I-metaiodobenzylguanidine (MIBG) has been developed as a functional analog of the neurotransmitter norepinephrine. The success of MIBG as an imaging agent for neural crest tumors is derived from its chemical similarities to norepinephrine. The present study aimed to explore a potential of (123)I-MIBG to differentiate embryonal tumors from other types of brain tumors.

METHODS

Sixteen patients with brain tumors including three medulloblastomas, one neuroblastoma, six gliomas, and six meningiomas were examined with single-photon emission computerized tomography (SPECT) using (123)I-MIBG. The (123)I-MIBG uptake of tumors was defined as the ratios of tumor/nontumor (early and delayed T/NT) on SPECT images scanned 30 min and 6 h after intravenous injection of the tracer, respectively. Retention index was calculated as (delayed T/NT - early T/NT)/early T/NT.

RESULTS

The T/NT ratios on the early images for embryonal tumors (medulloblastomas and neuroblastoma), gliomas, and meningiomas were 3.2+/-1.7 (mean+/-SD), 1.4+/-0.3, and 1.6+/-0.5, respectively. The early uptake was significantly higher in the embryonal tumors than in gliomas (P<0.05). Delayed T/NT ratios for embryonal tumors were increased compared to the early T/NT ratios, while in contrast delayed T/NT ratios for the other tumors remained low (1.2-1.7). The high retention indices of the embryonal tumors indicate specific uptake of (123)I-MIBG in the tumors.

CONCLUSION

Early high accumulation and high retention on delayed imaging may indicate a possibility of (123)I-MIBG SPECT in differentiating embryonal brain tumors from gliomas and meningiomas.

Canine intracranial epidermoid cyst

A 7-year-old intact male pitbull presented with a 2-month history of progressive dysequilibrium. Cerebrospinal fluid analysis was indicative of a central inflammatory or neoplastic disorder. A cerebellar cystic structure was identified on magnetic resonance imaging which was found to be an epidermoid cyst on histopathology.