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BACKGROUND: The accurate diagnosis of early bone metastases plays an important role in treatment and prognosis. Bone biopsy is the gold standard for the diagnosis of bone metastases, but it is difficult to implement in clinical practice because of its invasive and small specimen size. In recent years, with the continuous development of magnetic resonance imaging technology, quantitative magnetic resonance imaging techniques such as magnetic resonance spectroscopy and based on chemical shift encoded magnetic resonance imaging have been widely used in the diagnosis of bone metastasis. The derived markers include table signal fat fraction and proton density fat fraction. All of them could reflect the bone marrow fat content. At present, the role of bone marrow fat in the development of bone metastases has become a new focus of attention. OBJECTIVE: To review the effect of bone marrow fat on bone metastasis and the quantitative evaluation techniques of magnetic resonance imaging, to summarize and compare the advantages and disadvantages of different magnetic resonance imaging fat quantification techniques in evaluating bone metastasis and their clinical applications. METHODS: The computer was used to search relevant literature in PubMed and CNKI database. Chinese and English search terms were “bone metastases, bone marrow adipocytes, magnetic resonance imaging, quantitative MRI, fat fraction, magnetic resonance spectrum, chemical shift encoding-based water-fat imaging.” A total of 67 relevant articles were obtained according to the inclusion and exclusion criteria. RESULTS AND CONCLUSION: (1) Bone marrow adipocytes can contribute to the occurrence of bone metastasis by secreting a variety of related hormones and cytokines, providing energy for tumor cells, and inducing osteoclast differentiation. (2) Quantitative magnetic resonance imaging can accurately quantify adipose tissue and measure the change of fat content in bone marrow, which is helpful for the diagnosis of bone metastasis. (3) Magnetic resonance spectroscopy can reflect different metabolites through different proton precession frequencies, so it can be used for fat quantification, and is currently used as an auxiliary test to evaluate metastatic fractures. (4) Chemical shift encoding-based water-fat imaging can separate water and fat signals in positive and inverse phases, so as to measure adipose tissue signals, with high sensitivity, specificity and accuracy in differentiating benign and malignant vertebral fractures. [ABSTRACT FROM AUTHOR]

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BACKGROUND: At present, there are few reports on the application of compressed sensing technology in ankle MRI. OBJECTIVE: To investigate the effect of different acceleration factors in compressed sensing (CS) on image quality and scanning time of conventional 2D-MRI of the ankle joint. METHODS: Totally 24 healthy volunteers (38 ankles) underwent conventional 2D-TSE sequence scanning at 3.0T MR. Based on SENSE parallel imaging (S group) and compressed sensing technique (CS group), sequence images of T1WI-TRA (S1.3, CS1.3, CS1.9, CS2.7), PDWI-Dixon-SAG (S1.8, CS1.8, CS2.6, CS3.2) and PDWI-SPAIR-COR (S1.3, CS1.3, CS1.6, CS2.0) were obtained separately. Other scan parameters of each sequence remained consistent. The tendon, cartilage, ligament and muscle structures of the ankle joint images were subjectively scored by 5 points. The standard deviation of background noise and signal intensity of bone, cartilage, ligament, tendon, muscle, effusion and fat structures were measured, and the signal-to-noise ratio and contrast-to-noise ratio were calculated. The subjective score and objective evaluation of different acceleration factor images were statistically analyzed. SENSE group was used as the standard reference for the image quality of each sequence. RESULTS AND CONCLUSION: (1) When acceleration factor was the same, there were no statistically significant differences in subjective score, signal-to-noise ratio and contrast-to-noise ratio between the S group and the CS group (P > 0.05). (2) The acceleration factor of CS (TRA), CS (SAG) and CS (COR) sequences at CS1.9, CS2.6 and CS1.6 showed no significant difference in the image quality of cartilage, tendon, ligament and other main observed structures of the ankle joint (P > 0.05), and the scanning time was 1 minute and 32 seconds, 1 minute and 42 seconds, 1 minute and 48 seconds, respectively. When the acceleration factor of CS (TRA), CS (SAG) and CS (COR) sequences increased to CS2.7, CS3.2 and CS2.0, respectively, the subjective scores of all anatomical structures were still greater than 3, but signal-to-noise ratio and contrast-to-noise ratio of each sequence decreased significantly (P < 0.05). (3) These findings confirm that when acceleration factor is the same, compared with CS group, the image quality obtained by CS group is generally higher than that of S group. When acceleration factor increases, the scanning time of CS sequence decreases gradually, and the image quality also decreases. On a 3.0T MR, CS technology recommended CS1.9, CS2.6, and CS1.6 accelerators for conventional 2D sequences T1WI-TRA, PDWI-Dixon-SAG, and PDWI-SPAIR-COR, respectively, reducing the overall time by about 27% (1 minute and 53 seconds). [ABSTRACT FROM AUTHOR]

BACKGROUND: 3D printing facilitates the creation of accurate physical models of patient-specific anatomy from medical imaging data sets. Until now, most models have been created from Computed Tomography (CT) data, but more and more people are interested in creating models from other data sets, such as ultrasound and magnetic resonance imaging. In particular, magnetic resonance imaging has great potential in 3D printing due to its good tissue characteristics and lack of ionizing radiation. OBJECTIVE: To systemically introduce the basic concept and process of 3D printing, to discuss the application of magnetic resonance imaging-based 3D printing technology in the clinical applications and bedside teaching in the fields of cardiovascular system, nervous system, osteoarticular system, oral and maxillofacial and genitourinary systems, and to briefly describe the research progress of the bio-3D printing technology. METHODS: We searched WanFang, CNKI, VIP, PubMed and web of science databases for relevant articles published from 2010 until now. The keywords were “3D printing, 3D printed, Additive Manufacturing, Rapid Prototyping, MRI, Magnetic Resonance Imaging” in Chinese and English, respectively. Fifty publications were in included in the final analysis. RESULTS AND CONCLUSION: 3D printing can be widely used in many fields of medicine. Magnetic resonance imaging plays an important role in 3D printing modeling due to its multi-planar reconstruction, multi-parameter MRI, multi-sequence imaging and high soft tissue resolution. It can not only print personalized models before operation, but also print personalized prostheses and implants. In addition, with the gradual development of bio-3D printing, more and more people begin to focus on this new field. [ABSTRACT FROM AUTHOR]