Improved performance of prostate DCE-MRI using a 32-coil vs. 12-coil receiver array

Determining the optimal magnetic resonance imaging sequences for the efficient diagnosis of temporomandibular joint disorders

Background

To compare and analyze nine MRI sequences of the TMJ and determine the optimum sequence for the rapid diagnosis of TMDs so as to develop new clinical guidelines.

Methods

Twenty young volunteers (a total of 40 joints) aged 22-26 years were recruited. Three basic sequences, T₁-weighted imaging (T₁WI), T₂-weighted imaging (T₂WI), and proton density-weighted imaging (PDWI), together with three positions, oblique sagittal (OSag) with closed mouth, oblique coronal (OCor) with closed mouth, and OSag with opened mouth, were selected in combination for testing. In the OCor position, four regions of interest (ROIs), the condyle (C), the disc (D), the disc outside (DO), and fat (F), were analyzed. For the OSag with closed mouth position and the OSag with opened mouth position sequences, the four ROIs were the condyle (C), the disc (D), the disc ahead (DA), and the disc rear (DR). The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and signal intensity ratio (SIR) were calculated and analyzed using independent sample t-tests and one-way analysis of variance. Two senior radiologists scored the images of the nine MRI sequences subjectively and selected three optimal sequences. Using the three selected sequences, 1479 patients with anterior disc displacement with reduction (ADDwR) or anterior disk displacement without reduction (ADDwoR) were evaluated by comparing the preoperative TMJ MRI with the outcomes of the maxillofacial arthroscopy or open surgery.

Results

The T₁WI sequence showed the highest SNR while the T₂WI group had the lowest SNR. The ROIs of the T₂WI group had the highest CNR and SIR values in the OCor and OSag sequences. In the OCor sequence, the value for the SIR F/DO group was higher than the SIR C/D and SIR C/DO values. Using subjective analysis to evaluate the quality of the scans, the highest total scores were obtained for the OSag T₂WI with opened mouth and OSag PDWI with closed mouth sequences. From the objective and subjective analysis, the three optimal sequences selected were OSag PDWI, OCor T₂WI with closed mouth, and OSag T₂WI with opened mouth. In patients with anterior disc displacement, the comparisons of the surgery and the selected MRI sequences indicated that the total diagnostic accuracy of the MRI was 96.3% (1,425/1,479 cases). For patients with ADDwoR, the diagnostic accuracy was 98.5% (1,372/1,393 cases), and for those with ADDwR it was 61.6% (53/86 cases). There were significant differences between the ADDwoR and ADDwR groups (χ²=312.92, P<0.01).

Conclusions

The three optimal MRI sequences for the rapid and efficient diagnosis of TMD were determined to be OSag PDWI, OCor T₂WI with closed mouth, and OSag T₂WI with opened mouth.

Impact of different phased-array coils on the quality of prostate magnetic resonance images

•

Image quality is similar for different body phased-array receive coil setups.

•

An 18-channel body phased-array receive coil setup achieved good image quality.

•

60-channel body phased-array receive coil setup slightly improves SNR in T2W images.

Purpose

To evaluate the influence of body phased-array (BPA) receive coil setups on signal-to-noise ratio (SNR) and image quality (IQ) in prostate MRI.

Methods

This prospective study evaluated axial T2-weighted images (T2W-TSE) and DWI of the prostate in ten healthy volunteers with 18-channel (18CH), 30-channel and 60-channel (60CH) BPA receive coil setups. SNR and ADC values were assessed in the peripheral and transition zones (TZ). Two radiologists rated IQ features. Differences in qualitative and quantitative image features between BPA receive coil setups were compared. After correction for multiple comparisons, p-values <0.004 for quantitative and p-values <0.017 for qualitative image analysis were considered statistically significant.

Results

Significantly higher SNR was found in T2W-TSE images in the TZ using 60CH BPA compared to 18CH BPA coil setups (15.20 ± 4.22 vs. 7.68 ± 2.37; p = 0.001). There were no significant differences between all other quantitative (T2W-TSE, p = 0.007−0.308; DWI, p = 0.024−0.574) and qualitative image features (T2W-TSE, p = 0.083–1.0; DWI, p = 0.046–1.0).

Conclusion

60CH BPA receive coil setup showed marginal SNR improvement in T2W-TSE images. Good IQ could be achieved with 18CH BPA coil setups.

Use of kZ -space for high through-plane resolution in multislice MRI: Application to prostate

PURPOSE

The goal of this work is to demonstrate 1 mm through-plane resolution in multislice T2SE MRI using k Z -space processing of overlapping slices and show applicability in prostate MRI.

METHODS

Multiple overlapped slices are acquired and Fourier transformed in the slice-select direction. The slice profile is incorporated into a Tikhonov-regularized reconstruction. Through-plane resolution is tested in a resolution phantom. An anthropomorphic prostate phantom is used to study the SNR, and results are compared with theoretical prediction. The proposed method is tested in 16 patients indicated for clinical prostate MRI who gave written informed consent as overseen by our IRB. The "proposed" vs. "reference" multislice images are compared using multiple evaluation criteria for through-plane resolution.

RESULTS

The modulation transfer function (MTF) plots of the resolution phantom show good modulation at frequency 0.5 lp/mm, demonstrating 1 mm through-plane resolution restoration. The SNR measurements experimentally match the theoretically predicted values. The radiological evaluation shows that the proposed method is superior to the reference method for five criteria of sharpness but inferior with respect to artifacts.

CONCLUSIONS

In conjunction with overlapped slices a k Z -space-based reconstruction approach can be used to improve through-plane resolution in multislice T2SE MRI. 1 mm resolution is demonstrated from 3.2 mm thick slices. The in vivo results from prostate MRI show improved sharpness when compared to the standard multislice method.

Accuracy of the magnetic resonance imaging pathway in the detection of prostate cancer: a systematic review and meta-analysis

BACKGROUND

Although magnetic resonance imaging and subsequent targeted biopsy ('MRI pathway') have been widely adopted in routine clinical practice, it is still a common practice to perform systematic biopsy concurrently, because the accuracy of the MRI pathway is yet to be fully defined. This systematic review of the literature assessed the sensitivity of the MRI pathway for detecting clinically significant prostate cancer.

METHODS

Multiple databases were searched up to May 2017 according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement for studies assessing the accuracy of MR-guided biopsy (MRGB) compared to a reference standard which consisted of both MRGB and systematic biopsy with at least 20-cores. The primary outcome was the sensitivity of detecting clinically significant prostate cancer defined as Gleason ≥7 disease.

RESULTS

A total of 15 studies met the predefined inclusion criteria. Overall, studies were assessed to be of low quality with inadequate blinding of personnel, which could introduce performance and detection bias. The calculated summary sensitivity of the MRI pathway was 78.3% [95%CI 75.0-81.4%]. There was moderate heterogeneity between the included studies (I² = 36%). Subgroup analysis was performed based on clinical setting, the strength of MRI magnet and mode of image fusion as factors but no interaction was identified between any of the subgroups. No publication bias was identified.

CONCLUSION

The MRI pathway cannot yet be solely relied upon to diagnose clinically significant disease and hence additional systematic sampling should still be performed during the biopsy procedure.

Technical Aspects of Contrast-enhanced MR Angiography: Current Status and New Applications

This article is based on a presentation at the meeting of the Japanese Society of Magnetic Resonance in Medicine in September 2016. The purpose is to review the technical developments which have contributed to the current status of contrast-enhanced magnetic resonance angiography (CE-MRA) and to indicate related emerging areas of study. Technical developments include MRI physics-based innovations as well as improvements in MRI engineering. These have collectively addressed not only early issues of timing and venous suppression but more importantly have led to an improvement in spatiotemporal resolution of CE-MRA of more than two orders of magnitude compared to early results. This has allowed CE-MRA to be successfully performed in virtually all vascular territories of the body. Contemporary technical areas of study include improvements in implementation of high rate acceleration, extension of high performance first-pass CE-MRA across multiple imaging stations, expanded use of compressive sensing techniques, integration of Dixon-based fat suppression into CE-MRA sequences, and application of CE-MRA sequences to dynamic-contrast-enhanced perfusion imaging.