IVIM imaging can be used as a noninvasive imaging method to differentiate malignant brain tumors that show similar conventional MR imaging features.

BACKGROUND AND PURPOSE:Dissecting vertebrobasilar aneurysms are challenging to treat, and standard treatment modalities remain controversial. We retrospectively evaluated our experience using endovascular techniques to treat these aneurysms.

A study was performed to evaluate the relationship between the imaging features and clinical presentation of vertebral artery (VA) dissection. Twenty-two patients with 24 VA dissections at angiography and clinical evaluation also underwent computed tomography and magnetic resonance imaging. The angiographic patterns of VA dissection were categorized as aneurysmal (n = 10) or steno-occlusive (n = 14). All 10 patients (10 lesions) with the aneurysmal pattern had dissection in the V4 (intradural) segment and presented with headache (n = 5), neurologic deficit (n = 2), dizziness (n = 2), or altered mentality (n = 1). However, the 12 patients (14 lesions) with the steno-occlusive pattern had dissection from the V1 segment to the V4 segment and presented with neurologic deficits caused by infarction of an embolic nature. Overall, the most frequent VA dissection site was the V4 segment. The distribution of the dissection sites and the clinical presentation tended to differ according to the angiographic patterns of aneurysm or stenosis-occlusion.

Background and PurposeBrain tumor cellularity has been assessed by using apparent diffusion coefficient (ADC). However, the ADC value might be influenced by both perfusion and true molecular diffusion, and the perfusion effect on ADC can limit the reliability of ADC in the characterization of tumor cellularity, especially, in hypervascular brain tumors. In contrast, the IVIM technique estimates parameter values for diffusion and perfusion effects separately. The purpose of our study was to compare ADC and IVIM for differentiating among glioblastoma, metastatic tumor, and primary CNS lymphoma (PCNSL) focusing on diffusion-related parameter.Materials and MethodsWe retrospectively reviewed the data of 128 patients with pathologically confirmed glioblastoma (n = 55), metastasis (n = 31), and PCNSL (n = 42) prior to any treatment. Two neuroradiologists independently calculated the maximum IVIM-f (fmax) and minimum IVIM-D (Dmin) by using 16 different b-values with a bi-exponential fitting of diffusion signal decay, minimum ADC (ADCmin) by using 0 and 1000 b-values with a mono-exponential fitting and maximum normalized cerebral blood volume (nCBVmax). The differences in fmax, Dmin, nCBVmax, and ADCmin among the three tumor pathologies were determined by one-way ANOVA with multiple comparisons. The fmax and Dmin were correlated to the corresponding nCBV and ADC using partial correlation analysis, respectively.ResultsUsing a mono-exponential fitting of diffusion signal decay, the mean ADCmin was significantly lower in PCNSL than in glioblastoma and metastasis. However, using a bi-exponential fitting, the mean Dmin did not significantly differ in the three groups. The mean fmax significantly increased in the glioblastomas (reader 1, 0.103; reader 2, 0.109) and the metastasis (reader 1, 0.105; reader 2, 0.107), compared to the primary CNS lymphomas (reader 1, 0.025; reader 2, 0.023) (P < .001 for each). The correlation between fmax and the corresponding nCBV was highest in glioblastoma group, and the correlation between Dmin and the corresponding ADC was highest in primary CNS lymphomas group.ConclusionUnlike ADC value derived from a mono-exponential fitting of diffusion signal, diffusion-related parametric value derived from a bi-exponential fitting with separation of perfusion effect doesn’t differ among glioblastoma, metastasis, and PCNSL.