Evaluation of aqueductal stenosis by 3D sampling perfection with application-optimized contrasts using different flip angle evolutions sequence: preliminary results with 3T MR imaging

Abstract

Background and purpose: Diagnosis of AS and periaqueductal abnormalities by routine MR imaging sequences is challenging for neuroradiologists. The aim of our study was to evaluate the utility of the 3D-SPACE sequence with VFAM in patients with suspected AS.

Materials and methods: PC-MRI and 3D-SPACE images were obtained in 21 patients who had hydrocephalus on routine MR imaging scans and had clinical suspicion of AS, as well as in 12 control subjects. Aqueductal patency was visually scored (grade 0, normal; grade 1, partial obstruction; grade 2, complete stenosis) by 2 experienced radiologists on PC-MRI (plus routine T1-weighted and T2-weighted images) and 3D-SPACE images. Two separate scores were statistically compared with each other as well as with the consensus scores obtained from general agreement of both radiologists.

Results: There was an excellent correlation between 3D-SPACE and PC-MRI scores (κ = 0.828). The correlation between 3D-SPACE scorings and consensus-based scorings was higher compared with the correlation between PC-MRI and consensus-based scorings (r = 1, P < .001 and r = 0.966, P < .001, respectively).

Conclusions: 3D-SPACE sequence with VFAM alone can be used for adequate and successful evaluation of the aqueductal patency without the need for additional sequences and examinations. Noninvasive evaluation of the whole cranium is possible in a short time with high resolution by using 3D-SPACE.

Fig 1.

A 23-year-old woman (control). A, Sagittal 3D-SPACE with VFAM image shows a normal aqueduct (grade 0, arrow). B, Thin-section axial reformatted 3D-SPACE with VFAM image demonstrates hypointense flow-void signal intensity consistent with an open aqueduct (arrow). C and D, Sagittal (C) and axial (D) PC-MRI are well-matched with 3D-SPACE sequence results (arrows).

Fig 2.

A 35-year-old man with partial aqueductal stenosis (patient 12). A, Sagittal T2-weighted image shows a narrowed aqueduct (arrow). B, Sagittal 3D-SPACE with VFAM image clearly demonstrates a prominent hypointense signal intensity in the cerebral aqueduct (arrow). The hypointense signal intensity (also called flow-void sign) on the 3D-SPACE MR image indicates the absence of a complete stenosis. C, Coronal oblique curved reconstructed 3D-SPACE image demonstrates a narrow but open aqueduct (arrow). D and E, Axial (D) and sagittal (E) PC-MRI indicate a narrowed but open aqueduct, consistent with partial aqueductal stenosis (arrows).

Fig 3.

A 7-year-old boy with a complete aqueductal stenosis and hydrocephalus (patient 1). A, Axial FLAIR image shows a compensated hydrocephalus. B, Sagittal thin-section T1-weighted image demonstrates a narrowed distal aqueduct and a prestenotic aqueductal dilation (arrow). C, Sagittal 3D-SPACE with VFAM MR image shows a restricted hyperintense CSF flow proximal to the stenotic segment, whereas the unrestricted flow of CSF distal to the stenosis appears hypointense (arrow). Sagittal (D and E) and axial (F) PC-MRI shows a complete aqueductal stenosis, consistent with 3D-SPACE images.

Fig 4.

A 9-year-old boy with complete aqueductal stenosis and neurofibromatosis type 1 (patient 21). A and B, Coronal T2-weighted MR image obtained 2 years ago shows no evidence of hydrocephalus (A), whereas a recent T1-weighted MR image shows a progressive hydrocephalus (B). C, Sagittal PC-MRI obtained at the level of the aqueduct shows absence of aqueductal flow (white arrow). Sagittal PC-MRI shows a flow representing the deep venous system in the posteroinferior part of the aqueduct (black arrow, C). The pulsation secondary to the venous flow in the quadrigeminal cistern can mimic the aqueductal flow. D, Sagittal 3D-SPACE with VFAM MR image clearly demonstrates the venous structures located in the third ventricular outlet–the quadrigeminal cistern (black arrow). This image demonstrates a complete aqueductal stenosis (white arrow, D). E and F, Axial thin-section (1 mm) reformatted images obtained from sagittal 3D-SPACE images (E) show multiple hamartomas (arrows, F).

Fig 5.

Timing diagram of the 3D-SPACE with different flip angles (3D-SPACE with VFAM). The diagram shows 1 TR of the pulse sequence. The first line shows the variation in the heights of the radio-frequency pulses during the echo-train. G_s is the section-selection gradient, which varies to select different sections in k-space. G_k and G_r are the phase-encoding and readout gradients, respectively. The timing diagram was drawn by John P. Mugler III and modified with his permission.