Instability of background fat intensity suppression using fat-saturated (FS) MR imaging techniques according to region and reconstruction procedure in patients with oral cancer

Robustness of a Combined Modified Dixon and PROPELLER Sequence with Two Interleaved Echoes in Clinical Head and Neck MRI

Purpose:

The combination of modified Dixon (mDixon) and periodically rotated overlapping parallel lines with enhanced reconstruction sequence with two interleaved echoes, which promotes uniform fat-suppression and motion insensitivity, has recently become available for commercial magnetic resonance imaging (MRI) scanners. To compare the robustness of this combination sequence with that of standard Cartesian mDixon sequence for fat-suppressed T₂-weighted imaging in clinical head and neck MRI.

Methods:

Fifty patients with head and neck tumors were involved this study. All patients underwent MRI using both the combination and standard sequences. Two radiologists independently scored motion artifacts and water–fat separation error using a 4-point scale (1, unacceptable; 4, excellent). Furthermore, comprehensive comparative evaluation was performed using a 5-point scale (1, substantially inferior; 5, substantially superior). Data were statistically analyzed using the Wilcoxon signed-rank test.

Results:

In the motion artifact assessment, ratings of 3 or 4 points were assigned to 45% (observer-1, 58.0%; observer-2, 32.0%) and 97% (100%; 94.0%) of images for the standard and combination sequences, respectively (P < 0.001). For the water–fat separation error assessment, ratings of 3 or 4 points were assigned to 100% (100%; 100%) and 85% (84.0%; 86.0%) of images, respectively (P < 0.001). In the comprehensive evaluation, of the 100 cases (observer-1, 50; observer-2, 50), 96 were rated at four or five points. In cases with slight or no motion artifacts and water–fat separation errors, the combination sequence was superior to the standard sequence in term of noise and sharpness, and equal in terms of contrast.

Conclusion:

Although water–fat separation errors increased significantly in the combination sequence, most of these were acceptable. The significantly decreased motion artifacts in the combination sequence significantly improved image quality overall.

Magnetic resonance angiography with fresh blood imaging for identification of hemangiomas and blood vessels around hemangiomas in oral and maxillofacial regions

OBJECTIVES

To evaluate fresh blood imaging (FBI), a magnetic resonance imaging technique that does not use contrast, for identifying hemangiomas and feeding arteries in the oral and maxillofacial regions.

STUDY DESIGN

For 16 patients with hemangiomas, FBI visualizations of hemangiomas and feeding arteries in the oral and maxillofacial regions were compared with those from 3-dimensional (3D) phase-contrast magnetic resonance angiography (PC-MRA). Comparisons were based on the conspicuities of blood vessels and the 3D relationships of hemangiomas with the surrounding blood vessels.

RESULTS

The conspicuity of hemangiomas, feeding arteries, and blood vessels were significantly better with FBI than with PC-MRA. After differentiating arteries from veins, 3D visualizations of hemangiomas and arteries or veins could be performed with FBI.

CONCLUSIONS

FBI is a useful method in oral and maxillofacial regions for identifying the relationships between hemangiomas and the surrounding arteries or veins.

Relationship between cortical bone formation on mandibular condyles and alternation of the magnetic resonance signals characteristic of growth

INTRODUCTION

The purpose of this study was to elucidate the significance of double contour-like structures (DCLS) relative to the maturity of mandibular condyles and the possible constituents of DCLS. We evaluated the relationship between the alternation of DCLS and the ossification on the top of mandibular condyles.

METHODS

In 36 subjects, aged 9 to14 years at the first examination, magnetic resonance imaging characteristics of the mandibular condyles were obtained from fast spin echo intermediate-weighted images and T2-weighted images; 2 or 3 years later, magnetic resonance images were again obtained from 23 of the same 36 subjects.

RESULTS

A significant relationship was found between the absence of DCLS and the continuity of void-signal lines on the tops of the mandibular condyles. DCLS disappeared, and the void-signal lines on the tops of the mandibular condyles became continuous as the children grew. The top of DCLS was seen as a hypersignal on T2-weighted images.

CONCLUSIONS

Alternations of DCLS might be a useful criterion for evaluating the maturity of mandibular condyles in children. Possible constituents of DCLS might be hypervascular loose fibrous tissue and a proliferation of cartilage accompanied by active ossification on the tops of the mandibular condyles.