Rice and perfluorocarbon liquid pads: comparison of fat suppression effects

Is 3T MR nerve-bone fusion imaging a viable alternative to MRI-CBCT to identify the relationship between the inferior alveolar nerve and mandibular third molar

OBJECTIVES

To investigate the feasibility of MRI nerve-bone fusion imaging in assessing the relationship between inferior alveolar nerve (IAN) / mandibular canal (MC) and mandibular third molar (MTM) compared with MRI-CBCT fusion.

MATERIALS AND METHODS

The MRI nerve-bone fusion and MRI-CBCT fusion imaging were performed in 20 subjects with 37 MTMs. The Hausdorff distance (HD) value and dice similarity coefficient (DSC) was calculated. The relationship between IAN/MC and MTM roots, inflammatory, and fusion patterns were compared between these two fused images. The reliability was assessed using a weighted κ statistic.

RESULTS

The mean HD and DSC ranged from 0.62 ~ 1.35 and 0.83 ~ 0.88 for MRI nerve-bone fusion, 0.98 ~ 1.50 and 0.76 ~ 0.83 for MRI-CBCT fusion. MR nerve-bone fusion had considerable reproducibility compared to MRI-CBCT fusion in relation classification (MR nerve-bone fusion κ = 0.694, MRI-CBCT fusion κ = 0.644), direct contact (MR nerve-bone fusion κ = 0.729, MRI-CBCT fusion κ = 0.720), and moderate to good agreement for inflammation detection (MR nerve-bone fusion κ = 0.603, MRI-CBCT fusion κ = 0.532, average). The MR nerve-bone fusion imaging showed a lower ratio of larger pattern compared to MR-CBCT fusion (16.2% VS 27.3% in the molar region, and 2.7% VS 5.4% in the retromolar region). And the average time spent on MR nerve-bone fusion and MRI-CBCT fusion was 1 min and 3 min, respectively.

CONCLUSIONS

Both MR nerve-bone fusion and MRI-CBCT fusion exhibited good consistency in evaluating the spatial relationship between IAN/MC and MTM, fusion effect, and inflammation detection.

CLINICAL RELEVANCE

MR nerve-bone fusion imaging can be a preoperative one-stop radiation-free examination for patients at high risk for MTM surgery.

Effectiveness of a silicone device for foot MRI in order to obtain homogeneous fat suppression images

BACKGROUND

Incomplete fat suppression induced by magnetic field inhomogeneity is difficult to compensate for with hardware magnetic-field shimming.

PURPOSE

To evaluate the effectiveness of a silicone device used to obtain homogeneous fat suppression during 3T magnetic resonance imaging (MRI) scans of the foot.

MATERIAL AND METHODS

Thirty-eight healthy volunteers were enrolled and examined twice, before (group A) and after (group B) the application of a silicone device. Fat-saturated, T2-weighted, fast spin-echo images were acquired using the same scanning protocol at both examinations. Signal- and contrast-to-noise ratios (SNR and CNR) were calculated and compared in the four regions of interest (ROIs). ROI 1 and 2 were selected from toe-side bone and soft tissue, while ROI 3 and 4 were selected from proximal bone and soft tissue. Qualitative analysis using a four-point scale was performed for three categories. The categories are as follows: the overall image quality, homogeneity of the first phalange and metatarsal bone, respectively.

RESULTS

The SNR and CNR in ROI 1 and 2 were significantly higher in group A than in group B (SNR; P < 0.001, CNR; P < 0.001), and there were no significant difference in ROI 3 and 4. The qualitative score of the overall fat suppression in group B was significantly higher than that in group A (P < 0.001). Homogeneity of the first phalange in group B was also significantly higher than that in group A (P < 0.001). On the other hand, the homogeneity of the metatarsal bone was not significantly different in the two groups.

CONCLUSION

The use of a silicone device provides homogeneous fat suppression in 3T MRI of the foot and can significantly improve image quality.

Diffusion-weighted echo-planar imaging of the head and neck using 3-T MRI: Investigation into the usefulness of liquid perfluorocarbon pads and choice of optimal fat suppression method

PURPOSE

To investigate whether image quality can be improved using liquid perfluorocarbon pads (Sat Pad) and clarify the optimal fat-suppression method among chemical shift selective (CHESS), water excitation (WEX), and short TI inversion recovery (STIR) methods in diffusion-weighted imaging (DWI) of the head and neck using 3-T magnetic resonance imaging. Correlations between results of visual inspection and quantitative analysis were also examined.

MATERIAL AND METHODS

This study was approved by our Institutional Review Board and informed consent was waived. DWI was performed on 25 subjects with/without Sat Pad and using three fat-suppression methods (6 patterns). Image quality was evaluated visually (4-point scales and lesion-depiction capability) and by quantitative analysis (signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)). Two-way repeated-measures analysis of variance (ANOVA) was used to detect significant differences in scores of visual evaluation, SNR, and CNR.

RESULTS

Mean visual evaluation scores were significantly higher with Sat Pad using STIR than without Sat Pad for all fat-suppression methods (P<0.05). DWI with Sat Pad using STIR tended to be useful for depicting lesions. DWI using STIR showed reduced W-SNR (W: whole area of depicted structure) and CNR (between semispinalis capitis muscle and subcutaneous fat) due to fewer artifacts and uniform fat suppression.

CONCLUSION

Combining Sat Pad with STIR provides good image quality for visual inspections. When numerous artifacts are present and fat suppression is insufficient, higher SNR and CNR do not always provide good diagnostic image quality.