Radionecrosis of malignant glioma and cerebral metastasis: a diagnostic challenge in MRI.

Detecting a new area of contrast-enhancement at MRI after irradiation of malignant brain tumor arises the problem of differential diagnosis between tumor recurrence and radiation necrosis induced by the treatment. The challenge for imaging is to distinguish the two diagnoses given: the prognostic and therapeutic issues. Various criteria have been proposed in the literature based on morphological, functional or metabolic MRI. The purpose of this study was to perform an analysis of these tools to identify MRI best criteria to differentiate radiation necrosis lesions from malignant gliomas and brain metastases recurrence. For gliomas, the morphology of the contrast-enhancement cannot guide the diagnosis and the use of perfusion techniques and spectroscopy (multivoxels if possible) are necessary. In the follow-up of metastasis, a transient increase and moderate lesion volume is possible with a good prognosis. Morphological characteristics (volume ratio T2/T1Gd) and perfusion analysis provide valuable tools for approaching the diagnosis of radionecrosis.

Early-onset dementias: Specific etiologies and contribution of MRI.

Early-onset dementias are defined by onset of first symptoms before the age of 65. They have specific diagnostic features which differ from those of elderly patients in terms of their many causes and atypical clinical presentations. MRI is an essential procedure for identifying the underlying cause of the dementia (degenerative, vascular, infectious, inflammatory, metabolic or toxic). Clinical clues and MRI signs are described, and their defining features are related to the young age of the patients concerned. Diagnostic algorithms are proposed from signs which can be seen on the different MRI sequences (T1-weighted volume acquisition, T2-weighted FLAIR sequences, T2-weighted gradient-echo, diffusion-weighted imaging). Once obvious causes have been excluded, MRI can point towards the rarer causes of dementia which are characteristic in young people (particularly metabolic and autoimmune) and which require specific management and genetic counseling.

[Value of contrast-enhanced ultrasound in the evaluation of indeterminate renal cysts on CT]. / Évaluation de l'apport de l'échographie de contraste dans l'analyse des kystes rénaux de nature indéterminée au scanner.

PURPOSE: To demonstrate the value of contrast-enhanced ultrasound (CEUS) in the management of Bosniak type 2F and 3 renal cysts on CT. PATIENTS AND METHODS: Retrospective study of 14 patients with 15 Bosniak type 2F and 3 renal cysts on contrast enhanced CT. All patients underwent CEUS of the kidneys after injection of SonoVue(®). Using predetermined criteria, the lesions were classified as benign, malignant or indeterminate. Patients either underwent surgery or follow-up CT at one to three years. RESULTS: From the 15 indeterminate cysts on CT, 12 were either benign (n=8) or malignant (n=4) on CEUS. From the eight cysts considered benign on CEUS, seven remained stable on follow-up CT after a minimum of one year interval and one was surgically resected and confirmed to be benign. All four cysts considered malignant on CEUS were surgically resected and three were confirmed to be malignant and one was confirmed to be benign. Three cysts were indeterminate: two lesions were surgically resected and one was benign while the other was malignant and one lesion was stable at one year follow-up CT. CONCLUSION: CEUS was able to characterize indeterminate lesions as benign or malignant in 80% of cases with 92% reliability. Twenty percent of cysts remained indeterminate on CEUS. CEUS is reliable as a complement to CT in the evaluation of Bosniak type 2F and 3 renal cysts.