Compressed SENSE in Pediatric Brain Tumor MR Imaging : Assessment of Image Quality, Examination Time and Energy Release.

PURPOSE: To compare the image quality, examination time, and total energy release of a standardized pediatric brain tumor magnetic resonance imaging (MRI) protocol performed with and without compressed sensitivity encoding (C-SENSE). Recently introduced as an acceleration technique in MRI, we hypothesized that C­SENSE would improve image quality, reduce the examination time and radiofrequency-induced energy release compared with conventional examination in a pediatric brain tumor protocol. METHODS: This retrospective study included 22 patients aged 2.33-18.83 years with different brain tumor types who had previously undergone conventional MRI examination and underwent follow-up C­SENSE examination. Both examinations were conducted with a 3.0-Tesla device and included pre-contrast and post-contrast T1-weighted turbo-field-echo, T2-weighted turbo-spin-echo, and fluid-attenuated inversion recovery sequences. Image quality was assessed in four anatomical regions of interest (tumor area, cerebral cortex, basal ganglia, and posterior fossa) using a 5-point scale. Reader preference between the standard and C­SENSE images was evaluated. The total examination duration and energy deposit were compared based on scanner log file analysis. RESULTS: Relative to standard examinations, C­SENSE examinations were characterized by shorter total examination times (26.1 ± 3.93 vs. 22.18 ± 2.31 min; P = 0.001), reduced total energy deposit (206.0 ± 19.7 vs. 92.3 ± 18.2 J/kg; P < 0.001), and higher image quality (overall P < 0.001). CONCLUSION: C­SENSE contributes to the improvement of image quality, reduction of scan times and radiofrequency-induced energy release relative to the standard protocol in pediatric brain tumor MRI.

Abnormalities in the normal appearing white matter of the cerebral hemisphere contralateral to a malignant brain tumor detected by diffusion tensor imaging.

INTRODUCTION: Malignant brain tumors tend to migration and invasion of surrounding brain tissue. Histopathological studies reported malignant cells in macroscopically unsuspicious parenchyma (normal appearing white matter - NAWM) remote from the tumor localization. In early stages, diffuse interneural infiltration with changes of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) is hypothesized. MATERIAL AND METHODS: Patients' ADC and FA values from NAWM of the hemisphere contralateral to a malignant glioma were compared to age- and sex-matched normal controls. RESULTS: Apparent diffusion coefficient levels of the entire contralateral hemisphere revealed a significant increase and a decrease of FA levels. An even more pronounced ADC increase was found in a region mirroring the glioma location. CONCLUSIONS: In patients with previously untreated anaplastic astrocytoma or glioblastoma, an increase of the ADC and a reduction of FA were found in the brain parenchyma of the hemisphere contralateral to the tumor localization. In the absence of visible MRI abnormalities, this may be an early indicator of microstructural changes of the NAWM attributed to malignant brain tumor.

Precision of pulmonary vein diameter measurements assessed by CE-MRA and steady-state-free precession imaging.

OBJECTIVE: Pulmonary vein (PV) diameter assessment is important for planning and follow-up of PV ablation in atrial fibrillation. Therefore, the aim of our study was to evaluate inter- and intraobserver reliability of PV diameter measurements by contrast-enhanced magnetic resonance angiography (CE-MRA) and ECG-gated 2D multislice unenhanced steady-state-free precession sequences (multislice SSFP). METHODS: Sixty PV diameters in 17 consecutive patients were measured in transverse and coronal orientation with CE-MRA and multislice SSFP by two observers. Statistics to evaluate inter- and intraobserver reliability included Bland-Altman analysis and F-test. RESULTS: Intraobserver limits of agreement (LAG) ranged between ±0.50 cm (transverse) and ±0.86 cm (coronal) for CE-MRA versus ±0.40 cm (transverse) and ±0.67 cm (coronal) for multislice SSFP. Interobserver agreement showed LAG ranging between ±0.59 cm (transverse) and ±0.83 cm (coronal) for CE-MRA versus ±0.34 cm (transverse) and ±0.75 cm (coronal) for multislice SSFP. Intra- and interobserver variances did not reveal significant differences between CE-MRA and multislice SSFP in any orientation (all p-values >0.05). CONCLUSION: Multislice SSFP and CE-MRA enable comparable precision of PV diameter measurements. However, both methods reveal a wide range of intra- and interobserver agreement, which has to be thoroughly considered in clinical use. KEY POINTS: • Unenhanced magnetic resonance imaging can now provide measurement of pulmonary vein diameters • Steady-state-free precession offers a new method of performing unenhanced MR imaging • Both unenhanced and enhanced MRI measurements show wide intra- and interobserver variation • PV diameter measurements assessed by MRI have to be interpreted with care • Nevertheless, unenhanced MRI might replace some CT examinations for pulmonary vein demonstration.