MR Imaging of the Pituitary Gland and Postsphenoid Ossification in Fetal Specimens.

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 (R(2) = 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 (R(2) = 0.05). No apparent change in the size of pituitary hyperintensity was seen with gestational age (R(2) = 0.001). Postsphenoid ossification showed an increase in size with gestational age (R(2) = 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.

Differentiation between primary central nervous system lymphoma and glioblastoma: a comparative study of parameters derived from dynamic susceptibility contrast-enhanced perfusion-weighted MRI.

AIM: To evaluate the diagnostic performance of parameters derived from dynamic susceptibility contrast-enhanced perfusion-weighted magnetic resonance imaging, including first-pass slope ratio (FSR), which is potentially easier to derive than the other proposed parameters in this study, for differentiating primary central nervous system lymphoma (PCNSL) from glioblastoma. MATERIALS AND METHODS: Twenty-eight patients (10 PCNSLs and 18 glioblastomas) were analysed. Six perfusion parameters - corrected cerebral blood volume ratio (cCBVR), uncorrected CBV ratio (uCBVR), FSR, leakage coefficient (K2), percentage of signal-intensity recovery measured at the end of the first-pass (PSRend), and PSR measured using mean signal-intensity after the first-pass (PSRmean) - were derived from enhancing areas selected semi-automatically. Comparisons of cCBVR and uCBVR and of PSRend and PSRmean were conducted. The differences between PCNSL and glioblastoma were compared for the six parameters, and their diagnostic performance was evaluated by receiver operating characteristic curve analysis. RESULTS: For both tumours, cCBVR was significantly higher than uCBVR, and PSRend was significantly lower than PSRmean. PCNSL demonstrated lower cCBVR, uCBVR and FSR, and higher K2, PSRend and PSRmean compared with glioblastoma (p=0.0044 or less). On receiver operating characteristic curve analysis, the areas under the curve were 0.822 for cCBVR, 0.944 for uCBVR, 0.917 for FSR, 0.917 for K2, 0.933 for PSRend, and 0.894 for PSRmean. No significant difference was observed among the parameters, except cCBVR, which was significantly inferior to uCBVR. CONCLUSIONS: PCNSL can be differentiated from glioblastoma with high diagnostic value using any of the parameters, except cCBVR. FSR demonstrates high differential performance comparable to the other parameters.

Visualization of lenticulostriate arteries by flow-sensitive black-blood MR angiography on a 1.5 T MRI system: a comparative study between subjects with and without stroke.

BACKGROUND AND PURPOSE: The branches of the LSA are the main causative arteries for lacunar infarction, though the vascular changes are largely unknown. Herein, we examined the correlation of LSA imaging findings in patients with lacunar infarction compared with controls by using FSBB-MRA. MATERIALS AND METHODS: Fifteen patients (9 men, 6 women; mean age, 73 years) with infarction at the basal ganglia and/or its vicinity were prospectively enrolled, and 12 aged-matched control subjects (6 men, 6 women; mean age, 68 years) were examined by using FSBB-MRA on a 1.5T MR imaging system. Total number and length of visualized LSA branches were compared by a 2-tailed 2-sample t test. Stepwise multiple regression analyses were performed, including hypertension, hyperlipidemia, smoking history, and diabetes mellitus after evaluation of their colinearity. P<.05 after correction for multiple comparisons was considered significant. RESULTS: Patients with stroke had significantly fewer LSA branches (average, 6.3; 95% CI, 5.4-7.1) than controls (8.7; 95% CI, 7.8-9.5) (P=.0003). The total LSA lengths were 117 mm (95% CI, 96-138 mm) for patients with stroke and 162 mm (95% CI, 133-91 mm) for control subjects (P=.01). In stepwise multiple regression analysis, only the LSA branch numbers were significantly related to infarction (P=.0003), while only hypertension was significantly related to total LSA length (P=.0085). CONCLUSIONS: Using FSBB-MRA to visualize LSA branches, we found a significant reduction in the numbers of LSA branches in patients with stroke, and hypertension was inversely related to total LSA length. FSBB is a promising method to investigate the LSA by using 1.5T MR imaging.

Reduced-distortion diffusion MRI of the craniovertebral junction.

BACKGROUND AND PURPOSE: CVJ lesion suffers from a high sensitivity to susceptibility and distortion artifacts, which sometimes makes diffusion image difficult to interpret. Our purpose was to evaluate the potential for diffusion MR imaging using RS-EPI compared with SS-EPI in the assessment of the CVJ. MATERIALS AND METHODS: RS-EPI and SS-EPI DTI images were acquired from 10 healthy volunteers using 3T MRI with a 32-channel head coil. For both sequences, the following parameters were used: 1-mm(2) in-plane resolution; 3-mm section thickness; TR = 5200 ms; 1 acquisition at b = 0 and 12 different encoding directions at b = 1000 seconds/mm(2). The RS-EPI sequence scan time was 9.44 minutes (1 average). The SS-EPI sequence was 9.37 minutes (8 averages). Diffusion tensor calculation and image analysis were performed using DTIStudio software. Diffusion trace images and color-coded fiber orientation maps were evaluated by 2 independent readers for distortion and delineation of fine structure using a semiquantitative scale in selected landmark locations. The absolute distances between the temporal base and the cerebellar contour between the T2-weighted images and the diffusion trace images obtained with RS-EPI and SS-EPI were also compared. RESULTS: The contours of the temporal lobe and cerebellum were better delineated and distortion artifacts were clearly reduced with the RS-EPI sequence. More fine structures were also visible in the brain stem and cerebellum with the RS-EPI sequence. The amount of distortion was significantly reduced with RS-EPI compared with SS-EPI (P < .01). CONCLUSIONS: The RS-EPI DTI sequence was less prone to geometric distortion than the SS-EPI sequence and allowed a better delineation of CVJ internal structure. Although the acquisition time is still relatively long, the RS-EPI appears as a promising approach to perform DTI studies in CVJ lesions, such as brain stem ischemia, neurodegenerative diseases, brain and skull base tumors, or inflammation.