Keywords: Bone, Head & Neck/ENT, craniosynostosis, skull, ultrashort echo time, dual-echo

Motivation: Reduction of ionizing radiation for repeat CT imaging of pediatric patients with craniosynostosis.

Goal(s): Develop an MRI method for rapid, high-resolution skull imaging with CT-like contrast. 

Approach: A dual-echo UTE sequence acquires 2 image echoes (proton density-weighted and T₁-weighted) in 3 minutes at a voxel size of 0.65x0.65x0.65 mm. A new joint ℓ₀-wavelet regularizer and an improved method for calculating the third image with CT-like contrast are developed.

Results: In 3 minutes of scan time, 3 co-registered high-resolution images with 3 different contrasts are simultaneously acquired. Image quality is not hindered by the aggressive acceleration factor. Short-T₂ specific images strongly resemble CT images.

Impact: We present a bone-specific dual-echo UTE MRI method that facilitates unimodal, single-session radiology for pediatric patients with craniosynostosis. The method does not involve ionizing radiation and may reduce the lifetime risk of cancer for patients indicated for repeat CT scans.

Keywords: Skeletal, Quantitative Imaging, Musculoskeletal

Motivation: The development of ankylosing spondylitis(AS) is associated with alterations in bone marrow microenvironment.

Goal(s): To quantitatively analyze changes and correlations of the lumbar and sacroiliac joints bone marrow microenvironment in AS using MRI mDixon-Quant. 

Approach:  Fat fraction (FF) and T2* were measured in the lumbar, bone marrow edema (BME), fat metaplasia (FM) of sacroiliac joints. 

Results: FF value in the lumbar of the AS group demonstrated a significant increase compared to the normal control group, positively correlating with FF value in FM of sacroiliac joints. FF and T2* showed significant differences between BME and FM in sacroiliac joints.

Impact: FF and T2* values help to quantitatively analyze variations in the bone marrow microenvironment of lumbar and sacroiliac joints in AS, providing MRI evidence for the mechanism of osteoporosis in AS, while also guiding clinical treatment for inflammation-associated osteopenia.

Keywords: Bone, Bone, Fat

Motivation: The relationship between vertebral bone mineral density (BMD) and fat composition of adjacent vertebral body and paraspinal muscle in patients with low back pain (LBP) remains unclear.

Goal(s): To investigate the association between vertebral BMD and the fat fractions of vertebral bone marrow and paraspinal muscle in LBP patients.

Approach: A retrospective study was conducted on LBP patients who underwent both quantitative computed tomography (QCT) and chemical shift-encoded MRI examinations.

Results: Age, fat fractions of bone marrow and psoas major are independent factors that influence vertebral bone mineral density.

Impact: The fat fraction of vertebral bone marrow and paraspinal muscles independently influences bone mineral density. The MR-based fat fractions may potentially predict osteoporosis and osteoporotic fractures without radiation, providing a safer way to diagnose osteoporotic vertebral fractures and associated complications.

Keywords: Vascular, DSC & DCE Perfusion

Motivation: By investigating changes in bone marrow microvascular permeability and bone microstructure, we can explore the key pathological and physiological mechanisms underlying impaired vascular repair in diabetes

Goal(s): To assess the functional changes in endothelial progenitor cells (EPCs) and alterations in bone microstructure in rabbits with severe limb ischemia complicated by diabetes mellitus using DCE-MRI and micro Micro-CT

Approach: 30 healthy male New Zealand white rabbits  underwent sagittal MR imaging of the femoral bone proximal coronal plane at fixed time points

Results: DCE-MRI combined with Micro-CT quantitative parameters is feasible to evaluate endothelial progenitor cell function and changes in bone microstructure in diabetes mellitus

Impact: The results of this study will provide a new perspective on the pathological and physiological mechanisms underlying bone marrow changes in diabetic patients with concurrent critical limb ischemia.

Keywords: Bone, Bone, ZTE long-T2 subspace

Motivation: Recent work has shown that achieving CT-like contrast highlighting bone can be obtained either indirectly through contrast inversion or directly through long-T2 suppression. While direct methods offer advantages, existing techniques are inefficient, resulting in long scan times.

Goal(s): To create an efficient long-T2 suppressed bone imaging MR scan.

Approach: We combined inversion recovery long-T2 suppression in a Zero Echo-Time sequence with subspace reconstruction to allow continuous data collection during the scan, eliminating dead time and improving efficiency.

Results: A two minute silent scan that produces bright bone and suppressed soft tissues

Impact: We have created a fast positive contrast bone MRI scan that has potential as an alternative to CT

Keywords: Skeletal, Bone

Motivation: Visualizing cortical bone with short T2 value is challenging since long-T2 tissues and fat usually obscure it. 

Goal(s): This study develops a new long-T2- and lipidic tissue-suppressed sequence with silent acoustic noise to improve patient scanning comfort. 

Approach: We use an AFP inversion RF with controlled timing to maintain the long-T2 components at a low level and optimize the sequence parameters to null the fat signal. 

Results: We apply the PETRA to reduce the SPL to only 1.9 dBA higher than the background. The head cortical bone structure can be successfully visualized with positive contrast.

Impact: The designed silent long-T2 tissue-suppressed PETRA sequence can be potentially useful for investigating the newborns bone development, which can decrease neonatal hearing injury risks and might be helpful for early-age skeletal maturation assessment.  

Keywords: Bone, Bone, Deep Learning reconstruction

Motivation: Bone MRI using ZTE has the potential to provide clinically relevant information on mineral bone but its routine use remains limited by its low SNR and chemical shift artifacts especially at 3.0T

Goal(s): We evaluated the impact of a deep learning reconstructions for ZTE which performs denoising, improves resolution and minimizes chemical shift artifacts (DLCSC).

Approach: ZTE sequences prospectively obtained in 10 patients were reconstructed with the DLCSC algorithm. Native and processed images were compared for their performance to detect bone lesions, taking CT as gold standard.

Results: DLCSC increased image quality and significantly improved bone lesion detection compared to native ZTE images.

Impact: DLCSC reconstruction overcomes the pitfalls of the ZTE sequence (low SNR and chemical shift artifacts) and improves its diagnostic performance. A complete study of the skeleton, including mineral bone assessment, becomes possible within a single MRI examination.

Keywords: Bone, Bone, Ultra High Field, 7T, knee, bone marrow, pTx RF pulse, spatial-spectral RF pulse design, water excitation, fat supression

Motivation: To make knee bone marrow arterial spin labeling (ASL) imaging a viable and clinically practical approach.

Goal(s): To increase knee bone marrow ASL imaging signal-to-noise efficiency and quality by using parallel transmit spatial-spectral localized water excitation pulses for ASL image readouts.

Approach: Spatial-spectral water excitation pulses inside a 2D arbitrarily-shaped region of interest were designed and validated in a knee phantom and healthy volunteers using an 8-channel transceiver knee coil.

Results: The designed spatial-spectral pulses could produce localized water excitation inside targeted regions with effective fat suppression.

Impact: The validated pulse design provides an effective way for localized water excitation and eliminate the need for additional fat saturation with reduced RF power deposition, having a great potential to improve knee ASL imaging efficiency at ultrahigh field.

Keywords: Bone, Bone, Plug-and-Play Denoiser, IR-UTE, AI and Machine Learning

Motivation: (IR-)UTE MRI enables (quantitative) investigation of bony tissue. Imaging protocols, however, are still time consuming. 

Goal(s): To develop a reconstruction method, which can transfer undersampled / accelerated IR-UTE scans of bone into high quality images.

Approach: A thresholded Landweber algorithm was implemented, which uses both an L1-sparsity model and a pre-trained denoising convolutional network as regularizers of the physical MR model.

Results: The reconstruction method was capable of delivering superior image quality compared to reconstructions based on straightforward NUFFT or iterative SENSE, especially in the case of significant undersampling.

Impact: IR-UTE imaging accelerated by our proposed reconstruction based on L1-sparsity and a pre-trained denoising convolutional neural network shortens investigations by a factor of up to five, thereby facilitating further research on the topic as well as clinical transfer.

Keywords: Functional/Dynamic, Visualization, kinematic, real-time

Motivation: Joint Maltracking or improper loading cannot be assessed with conventional, static MRI.

Goal(s): Demonstrate the feasibility of using images without motion to de-noise and segment real-time 4D images and generate 4D moving models.

Approach: In 31 subjects, a fully sampled image and many highly-undersampled images reconstructed from the same data acquired without motion are used to train a neural network to generate artifact-free images and bone segmentations for images acquired with motion.

Results: The resulting real-time images are recognizable however more work is needed to improve the reliability of the segmentation, especially in cases of large-scale or fast motion.

Impact: Deep learning based de-noising and segmentation of real-time 3D kinematic MR imaging make it possible to model knee kinematics and open the doors for the study of the knee in motion and under load for improved identification of pain generators.

Keywords: Bone, MR Value

Motivation: The relationship between vertebral bone marrow T2* value and bone mineral density (BMD) has been rarely reported and remains controversial.

Goal(s): The study aimed to analyze the correlation between T2* and BMD and evaluate the efficacy of T2* in diagnosing osteoporosis. 

Approach: The IDEAL IQ MR Sequence was used to measure vertebral bone marrow T2* and quantitative computed tomography (QCT) was used to measure BMD. 

Results: Vertebral T2* was negatively correlated with BMD. While T2* can serve as a supplementary indicator for diagnosing osteoporosis, it should not be relied upon as the sole diagnostic indicator.

Impact: MRI-based T2* value provides a safer way for quantitative assessment of OP, and may be used as a complement to BMD to improve the accuracy of early diagnosis of OP.

Keywords: Bone, Relaxometry

Motivation: Denoising algorithms may significantly improve the SNR of relaxation time maps of the bone and cartilage. 

Goal(s): To compare the performance of T-NORDIC and MPPCA denoising techniques for 3D T2 mapping of the femoral head.

Approach: 3D T2 maps of the femoral heads from 12 piglets imaged at 3T MRI were denoised using MPPCA and T-NORDIC with parametric dimensions of 4 and 12. The results of qualitatively and quantitatively compared for image quality and quantitative accuracy.
 

Results: T-NORDIC provided superior performance with limited parametric dimension (4 weighted images), demonstrating its promise for magnetization-prepared mapping sequences of the hip joint.

Impact: T2 relaxation time mapping is critically investigated for addressing several MSK related diagnosis, but possibly due to thin and sensitive structures in the femoral head even slightest of the perturbations can lead to ineffective computation of quantitative mapping.

Keywords: Bone, Quantitative Imaging, Synthetic MR, ONFH

Motivation: Both qualitative and quantitative diagnosis of ONFH can be achieved through Synthetic MRI.

Goal(s): To investigate the value of Synthetic MRI in evaluating the osteonecrosis of femoral head(ONFH).

Approach: 336 hips in 168  cases of clinically diagnosed patients with ONFH were recruited and measured with T1, T2 and PD mapping derived by Synthetic MRI, 70 hips were normal as controls and 256 were ONFH.

Results: T1 , T2 and PD values showed significantly different values between ONFH and normal hip(all P<0.001). .With further ROC analysis, the diagnostic efficacy of T1 in the necrosis region and edema region was better than T2 and PD.

Impact: MRI images are important for clinical diagnosis of ONFH, while conventional MRI is qualitative diagnosis, quantitative diagnosis of ONFH is not yet available, therefore, Synthetic MRI may be considered an effective quantitative method in differentiating ONFH from normal femoral.

Keywords: Bone, Diffusion/other diffusion imaging techniques, RESOLVE DWI; multi-b-values-fitting; axial spondyloarthritis; quantitative; tumour necrosis factor inhibitors

Motivation:  Methods to quantitatively assess disease activity and efficacy of axSpA are still being explored.

Goal(s): To find a reliable quantitative indicator for evaluating disease activity and curative effect of axSpA, using multi-b-values-fitting RESOLVE DWI. 

Approach: By comparing the ADC values calculated by fitting different b values between different groups, a relatively reliable b-values-fitting sequence was obtained, further evaluating curative effect of the treatment group in different cycles. 

Results: Multi-b-values-fitting (b=50,500,700s/mm²) RESOLVE DWI has a certain advantage in evaluating disease activity and efficacy of axSpA, but the effect of short-term review (3 weeks or less) is unsatisfactory.

Impact: Multi-b-Values-Fitting RESOLVE DWI can differentiate the severity of axSpA disease activity more intuitively, by measuring the ADC values of bone marrow edema of sacroiliac joints, providing a new idea for clinical search for more objective and accurate quantitative parameters.

Keywords: Other Musculoskeletal, Magnetization transfer, osteoporosis、Q-Dixon

Motivation: More research has confirmed the important role of new MRI techniques in early screening and efficacy evaluation of osteoporosis. 

Goal(s): The purpose of this study is to construct a nomogram clinical prediction model for predicting osteoporosis based on Q-Dixon、MT technology and clinical data

Approach: logistic regression analysis confirmed that four risk factors (gender, age, FF value, MTR value) were significant independent predictors of osteoporosis, and the calibration curve of the nomogram had good reliability in evaluating osteoporosis in training and validation cohorts

Results: The Nomogram model has more advantages in predicting osteoporosis than the FF model and MTR model

Impact: The clinical prediction model based on gender, age, FF value, and MT value nomogram has good universality and clinical benefits, is easy to promote, and helps to better screen for osteoporosis in the general elderly population, achieve early detection.

Keywords: Bone, Bone

Motivation: Hip fractures pose a substantial health concern commonly associated with osteoporosis. Bone mineral density from Dual-energy X-ray absorptiometry (DXA) is the standard-of-care test for assessment of osteoporosis and fracture risk, yet many who sustain fragility fractures are above the diagnosis threshold. 

Goal(s): The objective of this study was to conduct a preliminary investigation into the validity of MRI Finite Element Analysis (FEA) for predicting bone strength.

Approach: Ultrashort Echo Time MRI was used on cadaveric human femur sections and FEA was performed.

Results: The stiffness derived from UTE FEA showed a strong correlation with stiffness derived from mechanical testing.

Impact: This study compared UTE-based Finite Element Analysis to mechanical testing and found that there was a significant correlation between computational and experimental values. This indicates the potential for UTE MRI to be used in the clinical evaluation of bone strength.