BACKGROUND AND PURPOSE: A thorough knowledge of fetal growth and development is key to understanding both the normal and abnormal fetal MR imaging findings. We investigated the size and signal intensity of the normal pituitary gland and the intrasphenoidal ossification around the Rathke pouch in formalin-fixed fetuses on MR imaging.

MATERIALS AND METHODS: Thirty-two fetuses with undamaged brains were included in this study (mean age, 19.93 weeks; age range, 12–31 weeks). Visual inspection of the pituitary and ossification around the Rathke pouch in the sphenoid bone or the postsphenoid ossification was conducted. The extent of pituitary and postsphenoid ossification, pituitary/pons signal ratio, and postsphenoidal ossification/sphenoid bone signal ratio was compared according to gestational age.

RESULTS: The pituitary gland was identified as a hyperintense intrasellar structure in all cases, and postsphenoid ossification was identified as an intrasphenoidal hyperintense area in 27 of the 32 cases (84%). The mean pituitary/pons signal ratio was 1.13 ± 0.18 and correlated weakly with gestational age (R2 = 0.243), while the mean postsphenoid ossification/sphenoid bone signal ratio was 2.14 ± 0.56 and did not show any increase with gestational age (R2 = 0.05). No apparent change in the size of pituitary hyperintensity was seen with gestational age (R2 = 0.001). Postsphenoid ossification showed an increase in size with gestational age (R2 = 0.307).

CONCLUSIONS: The fetal pituitary gland was hyperintense on T1-weighted images and the pituitary/pons ratio and extent of postsphenoid ossification correlated weakly with gestational age.

Objective: We qualitatively evaluated the differences among susceptibility-weighted (SWI), magnitude (MAG), and high pass filtered phase (PHA) images in depicting interlobar differences in the appearance of the signal of the corticomedullary junction (CMJ). We conducted quantitative evaluation to validate the qualitative results.

Materials and Methods: We obtained SWI images from 25 preoperative brain tumor patients (12 men, 13 women, aged 19 to 82 years, mean, 52 years). Two trained neuroradiologists evaluated MAG, PHA, and SWI images. Qualitative evaluation of the CMJ signal and quantitative calculation of the relative signal ratio (RSR) percentages between the CMJ and deep white matter (WM) were conducted at 3 different slice levels of the brain independently for 4 different lobes (frontal, parietal, temporal, and occipital) and compared among MAG, PHA, and SWI. The extent of the area of the CMJ signal was graded on a 4-point scale (Grade 3, >75%; Grade 2, 50 to 75%; Grade 1, 25 to 50%; Grade 0, <25%). Data were statistically analyzed using a nonparametric Friedman test.

Results: The Kappa coefficients between the qualitative and quantitative grades were 0.002 for MAG, 0.0047 for PHA, and 0.050 for SWI. Qualitatively, on the PHA images and SWI, grades of the occipital lobes were significantly higher than those of the other lobes (P < 0.005). Quantitatively, PHA images showed statistically significant interlobar differences in RSR percentage values of the CMJ (P = 0.025).

Conclusion: Qualitatively, the appearance of the CMJ differed significantly among the different lobes of the brain on SWI and underlying PHA images but not on MAG images. Quantitatively, only PHA images showed significant interlobar differences in the RSR. PHA images are most sensitive to the CMJ signal contrast due to local paramagnetic iron content.

Purpose

To investigate the diffusion tensor imaging parameters of the optic radiation and surrounding structures using the high-resolution readout-segmented diffusion tensor imaging method.

Materials and methods

Coronal readout-segmented diffusion tensor images were acquired in 15 healthy volunteers. On three slices of each image, eigenvalue 1, fractional anisotropy, radial diffusivity, apparent diffusion coefficient, and signal intensity on T2-weighted images were measured in the lateral inferior longitudinal fasciculus, external and internal layers of the optic radiation, and the tapetum within regions of interest delineated by two independent observers. Profile curve analysis of regions of interest across the optic radiation and surrounding structures was performed for a representative typical case.

Results

Significant differences in fractional anisotropy, radial diffusivity and apparent diffusion coefficient were observed between external and internal layers of the optic radiation, while there was no significant difference in eigenvalue 1. In fractional anisotropy maps, two low signal bands were observed between the inferior longitudinal fasciculus, the optic radiation and the tapetum. Profile curve analysis showed a minimum on the fractional anisotropy and eigenvalue 1 images and a maximum in the radial diffusivity image.

Conclusion

Readout-segmented diffusion tensor imaging revealed significant differences in the diffusion tensor imaging parameters between internal and external layers of the optic radiation.

Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF) space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF. We also focused on the differences of oxygen enhancement at sulcal and ventricular CSF. Our results revealed that CSF signal after administration of oxygen shows rapid signal increase in both sulcal CSF and ventricular CSF on both sequences, with statistically significant predominant increase in sulcal CSF compared with ventricular CSF. CSF is traditionally thought to mainly form from the choroid plexus in the ventricles and is absorbed at the arachnoid villi, however, it is also believed that cerebral arterioles contribute to the production and absorption of CSF, and controversy remains in terms of the precise mechanism. Our results demonstrated rapid oxygen enhancement in sulcal CSF, which may suggest inhaled oxygen may diffuse into sulcal CSF space rapidly probably due to the abundance of pial arterioles on the brain sulci.

Rationale and Objectives

To optimize visualization of lenticulostriate artery (LSA) by time-of-flight (TOF) magnetic resonance angiography (MRA) with slice-selective off-resonance sinc (SORS) saturation transfer contrast pulses and to compare capability of optimal TOF-MRA and flow-sensitive black-blood (FSBB) MRA to visualize the LSA at 3T.

Materials and Methods

This study was approved by the local ethics committee, and written informed consent was obtained from all the subjects. TOF-MRA was optimized in 20 subjects by comparing SORS pulses of different flip angles: 0, 400°, and 750°. Numbers of LSAs were counted. The optimal TOF-MRA was compared to FSBB-MRA in 21 subjects. Images were evaluated by the numbers and length of visualized LSAs.

Results

LSAs were significantly more visualized in TOF-MRA with SORS pulses of 400° than others (P < .003). When the optimal TOF-MRA was compared to FSBB-MRA, the visualization of LSA using FSBB (mean branch numbers 11.1, 95% confidence interval (CI) 10.0–12.1; mean total length 236 mm, 95% CI 210–263 mm) was significantly better than using TOF (4.7, 95% CI 4.1–5.3; 78 mm, 95% CI 67–89 mm) for both numbers and length of the LSA (P < .0001).

Conclusions

LSA visualization was best with 400° SORS pulses for TOF-MRA but FSBB-MRA was better than TOF-MRA, which indicates its clinical potential to investigate the LSA on a 3T magnetic resonance imaging.

OBJECTIVE. In a clinical setting, lipoma can sometime show low signal intensity on susceptibility-weighted imaging (SWI) mimicking hemorrhage. The purpose of this study was to evaluate the fat-water interface chemical-shift artifacts between SWI and T2*-weighted imaging with a phantom study and evaluate SWI in lipoma cases.

MATERIALS AND METHODS. SWI, magnitude, high-pass filtered phase, and T2*-weighted imaging of a lard-water phantom were evaluated in the in-phase, out-of phase, and standard partially out-of-phase TE settings used for clinical 3-T SWI (19.7, 20.9, and 20.0 ms, respectively) to identify the most prominent fat-water interface low signal. SWI of five cases of CNS lipoma were retrospectively evaluated by two neuroradiologists.

RESULTS. TE at 19.7 ms (in-phase) showed the minimum fat-water interface low signal in the phase-encoding direction on magnitude, high-pass filtered phase, and SWI. TE at 20.9 ms (out-of-phase) showed the maximum fat-water interface in the phase-encoding direction on magnitude, high-pass filtered phase, and SWI. TE at 20.0 ms (partially out-of-phase) showed more fat-water interface low signal on SWI than on T2*-weighted imaging, especially in the phase-encoding direction. All lipomas in the five patients showed high signal intensity with surrounding peripheral dark rim on SWI.

CONCLUSION. Fat-water interface is more prominent on the standard TE setting used for clinical SWI (20.0 ms) than that of T2*-weighted imaging and shows a characteristic surrounding peripheral low-signal-intensity rim in lipoma. Knowing the fat-water appearance on SWI is important to avoid misinterpreting intracranial lipomas as hemorrhages.

We read with interest the article entitled “Detection of Intratumoral Calcification in Oligodendrogliomas by Susceptibility-Weighted MR Imaging” and would like to comment on the appearance of calcification on the high-pass-filtered phase images.

The authors reported that the paramagnetic (authors wrote “diamagnetic”) hemorrhagic component of the tumor would cause a negative phase shift and appear as dark signal on the high-pass-filtered phase images, while the diamagnetic (authors wrote “paramagnetic”) intratumoral calcifications would cause an opposite positive phase shift and appear as bright signal on the high-pass-filtered phase images. This description is true, but only in the case of right-handed MR imaging systems, while in left-handed MR imaging systems, the complete opposite signal would be seen: Paramagnetic substances would appear bright, while diamagnetic substances would appear dark.

In Figs 2D and 3D of the above-mentioned article, the high-pass-filtered phase images are those of a left-handed MR imaging system, evident by the bright signal of the veins (paramagnetic deoxyhemoglobin).

The article showed that high-pass-filtered phase images can depict intratumoral calcification in oligodendrogliomas better than conventional MR images; this finding has been reported before. Understanding the contrast appearance of high-pass-filtered phase images on left-handed versus right-handed MR imaging systems would make distinguishing diamagnetic calcification from paramagnetic hemorrhage a much easier task and prevent any possible confusion.