Deep Learning-reconstructed Parallel Accelerated Imaging for Knee MRI

BACKGROUND: Deep learning (DL) can improve image quality by removing noise from accelerated MRI. OBJECTIVE: To compare the quality of various accelerated imaging applications in knee MRI with and without DL. METHOD: We analyzed 44 knee MRI scans from 38 adult patients using the DL-reconstructed parallel acquisition technique (PAT) between May 2021 and April 2022. The participants underwent sagittal fat-saturated T2-weighted turbo-spin-echo accelerated imaging without DL (PAT-2 [2-fold parallel accelerated imaging], PAT-3, and PAT-4) and with DL (DL with PAT-3 [PAT-3DL] and PAT-4 [PAT-4DL]). Two readers independently evaluated subjective image quality (diagnostic confidence of knee joint abnormalities, subjective noise and sharpness, and overall image quality) using a 4-point grading system (1-4, 4=best). Objective image quality was assessed based on noise (noise power) and sharpness (edge rise distance). RESULTS: The mean acquisition times for PAT-2, PAT-3, PAT-4, PAT-3DL, and PAT-4DL sequences were 2:55, 2:04, 1:33, 2:04, and 1:33 min, respectively. Regarding subjective image quality, PAT-3DL and PAT-4DL scored higher than PAT-2. Objectively, DL-reconstructed imaging had significantly lower noise than PAT-3 and PAT-4 (P <0.001), but the results were not significantly different from those for PAT-2 (P >0.988). Objective image sharpness did not differ significantly among the imaging combinations (P =0.470). The inter-reader reliability ranged from good to excellent (κ = 0.761­0.832). CONCLUSION: PAT-4DL imaging in knee MRI exhibits similar subjective image quality, objective noise, and sharpness levels compared with conventional PAT-2 imaging, with an acquisition time reduction of 47%.

Deep Learning-Enhanced Parallel Imaging and Simultaneous Multislice Acceleration Reconstruction in Knee MRI.

OBJECTIVES: This study aimed to examine various combinations of parallel imaging (PI) and simultaneous multislice (SMS) acceleration imaging using deep learning (DL)-enhanced and conventional reconstruction. The study also aimed at comparing the diagnostic performance of the various combinations in internal knee derangement and provided a quantitative evaluation of image sharpness and noise using edge rise distance (ERD) and noise power (NP), respectively. MATERIALS AND METHODS: The data from adult patients who underwent knee magnetic resonance imaging using various DL-enhanced acquisitions between June 2021 and January 2022 were retrospectively analyzed. The participants underwent conventional 2-fold PI and DL protocols with 4- to 8-fold acceleration imaging (P2S2 [2-fold PI with 2-fold SMS], P3S2, and P4S2). Three readers evaluated the internal knee derangement and the overall image quality. The diagnostic performance was calculated using consensus reading as a standard reference, and we conducted comparative evaluations. We calculated the ERD and NP for quantitative evaluations of image sharpness and noise, respectively. Interreader and intermethod agreements were calculated using Fleiss κ. RESULTS: A total of 33 patients (mean age, 49 ± 19 years; 20 women) were included in this study. The diagnostic performance for internal knee derangement and the overall image quality were similar among the evaluated protocols. The NP values were significantly lower using the DL protocols than with conventional imaging ( P < 0.001), whereas the ERD values were similar among these methods ( P > 0.12). Interreader and intermethod agreements were moderate-to-excellent (κ = 0.574-0.838) and good-to-excellent (κ = 0.755-1.000), respectively. In addition, the mean acquisition time was reduced by 47% when using DL with P2S2, by 62% with P3S2, and by 71% with P4S2, compared with conventional P2 imaging (2 minutes and 55 seconds). CONCLUSIONS: The combined use of DL-enhanced 8-fold acceleration imaging (4-fold PI with 2-fold SMS) showed comparable performance with conventional 2-fold PI for the evaluation of internal knee derangement, with a 71% reduction in acquisition time.

Clinical feasibility of simultaneous multislice acceleration in knee MRI.

PURPOSE: To find the best simultaneous multislice (SMS) accelerated setting for clinical application in knee MRI. MATERIAL AND METHODS: Thirty-three patients (mean age, 54 years; 21 women) who underwent knee MRI (conventional/SMS sequences) between June and October 2020 were enrolled. Two radiologists retrospectively evaluated sagittal T1- and T2-weighted conventional (2-fold parallel acquisition technique [PAT-2]) and SMS (SMS-2 [PAT-2 with 2-fold SMS], SMS-3, and SMS-4) images. For qualitative analysis, artifacts (zebra/residual aliasing) and diagnostic confidence for internal derangement of knee (bone marrow, cartilage, meniscus, anterior cruciate ligament, and synovium abnormalities) were evaluated. For quantitative analysis, contrast-to-noise ratios of bone marrow, meniscus, joint effusion, and ligament were evaluated. RESULTS: Compared to PAT-2 (2 min 32 s), mean acquisition time was reduced by 47% in SMS-2; 64%, SMS-3; and 70%, SMS-4. In qualitative analysis, zebra artifacts were only seen on T2-weighted SMS images. The more SMS was applied, the more zebra and residual aliasing artifacts were seen and the lower diagnostic confidence was for internal derangement. However, qualitative analysis showed acceptable image quality in SMS-2 and SMS-3 images, but not in SMS-4 images. In quantitative analysis, SMS-4 images showed the lowest contrast-to-noise ratios and there were no significant differences among PAT-2, SMS-2, and SMS-3 images. CONCLUSION: Applying SMS-3 to knee MRI reduced scan time and showed acceptable image quality compared to conventional (PAT-2). However, when evaluating SMS images, radiologists should know that when more SMS is applied, more zebra and residual aliasing artifacts appear.

Clinical feasibility of MR-generated synthetic CT images of the cervical spine: Diagnostic performance for detection of OPLL and comparison of CT number.

ABSTRACT: We aimed to determine the incremental value of magnetic resonance generated synthetic computed tomography (MRCT), evaluate cervical ossification of the posterior longitudinal ligament (OPLL), and compare the computed tomography (CT) numbers between MRCT and conventional CT.Twenty-two patients who underwent magnetic resonance imaging (MRI) with MRCT protocols and CT were enrolled. MRCT images were generated from 3D-T2-weighted imaging, 3D-pointwise-encoding time reduction with radial acquisition, 3D-T1-Dixon, and 3D-time-of-flight sequences. Two radiologists independently evaluated the presence of OPLL at each cervical spine level during sessions 1 (MRI alone) and 2 (MRI + MRCT). CT was the reference standard for the presence of OPLL. One reader measured the mean CT number of the vertebral body and spinous process at each cervical spine level in the MRCT and CT images.Sensitivity for the detection of OPLL was markedly higher in session 2 (MRI + MRCT) than in session 1 (MRI alone), as measured by both readers (47% vs. 90%, reader 1; 63% vs. 93%, reader 2). The mean CT number of MRCT and CT showed a moderate to strong positive correlation (ρ = .42-.72, P < .001).The combined use of MRCT and MRI showed improved sensitivity for the evaluation of cervical OPLL. The mean CT number of MRCT and CT showed a positive correlation.

Compressed sensing time-of-flight magnetic resonance angiography with high spatial resolution for evaluating intracranial aneurysms: comparison with digital subtraction angiography.

BACKGROUND AND PURPOSE: Compressed sensing is used for accelerated acquisitions with incoherently under-sampled k-space data, and intracranial time-of-flight magnetic resonance angiography is suitable for compressed sensing. Compressed sensing time-of-flight is beneficial in decreasing acquisition time and increasing spatial resolution while maintaining acquisition time. In this retrospective study, we aimed to evaluate the image quality and diagnostic performance of compressed sensing time-of-flight with high spatial resolution and compare with parallel imaging time-of-flight using digital subtraction angiography as a reference. MATERIAL AND METHODS: In total, 39 patients with 46 intracranial aneurysms underwent parallel imaging and compressed sensing time-of-flight in the same imaging session and digital subtraction angiography before or after magnetic resonance angiography. The overall image quality, artefacts and diagnostic confidence were assessed by two observers. The contrast ratio, maximal aneurysm diameters and diagnostic performance were evaluated. RESULTS: Compressed sensing time-of-flight showed significantly better overall image quality, degree of artefacts and diagnostic confidence in both observers, with better inter-observer agreement. The contrast ratio was significantly higher for compressed sensing time-of-flight than for parallel imaging time-of-flight in both observers (source images, P < 0.001; maximum intensity projection images, P < 0.05 for both observers); however, the measured maximal diameters of aneurysms were not significantly different. Compressed sensing time-of-flight showed higher sensitivity, specificity, accuracy and positive and negative predictive values for detecting aneurysms than parallel imaging time-of-flight in both observers, with better inter-observer agreement. Compressed sensing time-of-flight was preferred over parallel imaging time-of-flight by both observers; however, parallel imaging time-of-flight was preferred in cases of giant and large aneurysms. CONCLUSIONS: Compressed sensing-time-of-flight provides better image quality and diagnostic performance than parallel imaging time-of-flight. However, neuroradiologists should be aware of under-sampling artefacts caused by compressed sensing.

Vocal fundamental frequency and perturbation measurements of vowels by normal Malaysian Chinese adults.

The acoustic properties of vowel phonation vary across cultures. These specific characteristics, including vowel fundamental frequency (F(0)) and perturbation measures (Absolute Jitter [Jita], Jitter [Jitt], Relative Average Perturbation [RAP], five-point Period Perturbation Quotient [PPQ5], Absolute Shimmer [ShdB], Shimmer [Shim], and 11-point Amplitude Perturbation Quotient [APQ11]) are not well established for Malaysian Chinese adults. This article investigates the F(0) and perturbation measurements of sustained vowels in 60 normal Malaysian Chinese adults using acoustical analysis. Malaysian Chinese females had significantly higher F(0) than Malaysian males in all six vowels. However, there were no significant differences in F(0) across the vowels for each gender. Significant differences between vowels were observed for Jita, Jitt, PPQ5, ShdB, Shim, and APQ11 among Chinese males, whereas significant differences between vowels were observed for all the perturbation parameters among Chinese females. Chinese males had significantly higher Jita and APQ11 in the vowels than Chinese females, whereas no significant differences were observed between males and females for Jitt, RAP, PPQ5, and Shim. Cross-ethnic comparisons indicate that F(0) of vowel phonation varies within the Chinese ethnic group and across other ethnic groups. The perturbation measures cannot be simply compared, where the measures may vary significantly across different speech analysis softwares.