With the rapid increase of MRI systems in hospitals in China,national multi-sectoral strategies have been put forward to clarify requirements for improving image quality of MRI systems and preventing application risks in clinic.Quality control of MRI systems becomes an important task for regulators as well as hospital radiology departments.The tools used for quality control include imaging performance phantom and specialized function phantom,which can realize detection or calibration for parameters such as high contrast resolution,image uniformity and relaxation time.This article mainly reviews the research progress of the operation principles,common types and clinical applications for these two types of phantoms mentioned above.

Purpose To explore the predictive value of CT-enhanced for tumor mutation burden(TMB)in hepatocellular carcinoma(HCC).Materials and Methods A total of 22 patients with pathologically confirmed HCC after undergoing radical resection in the First Affiliated Hospital,Army Medical University(Third Military Medical University)from January 2020 to January 2023 were collected,all of whom were quantified for TMB.Clinical,laboratory tests,CT imaging characteristics and follow-up of patients were recorded.Variables with P<0.2 were screened by stepwise regression analysis for independent risk factors for TMB.The area under the curve of receiver operating characteristic was used to assess the diagnostic efficacy.Results High TMB level was a risk factor for disease-free survival after HCC surgery(HR=1.115,P<0.05).According to the optimal cut-off value,TMB was classified into a high-risk group(>9.25 mutation/Mb)and low-risk group(≤9.25 mutation/Mb).Univariate analysis of intratumor ischemia or necrosis was statistically different between the high-risk and low-risk groups(P=0.005),and only intratumor ischemia or necrosis was an independent risk factor for predicting high TMB level by stepwise regression analysis(P<0.05).The area under the curve for predicting disease-free survival was 0.833(95%CI 0.615-0.956,P<0.001),with a sensitivity of 100.0%and a specificity of 66.7%.Conclusion High TMB level is associated with poor prognosis after HCC resection.Intratumor ischemia or necrosis have certain clinical value in predicting high TMB level,and are expected to provide a reference basis for personalized diagnosis and treatment of HCC patients.

Purpose To explore the clinical features and CT/MRI manifestations of fibro-adipose vascular anomaly(FAVA)in children,and to analyze the misdiagnosis reason,in order to improve the diagnostic accuracy.Materials and Methods A retrospective analysis was conducted on 15 pediatric patients with pathologically confirmed FAVA in Shanghai Children's Hospital,School of Medicine,Shanghai Jiao Tong University from January 2014 to April 2024.Among them,11 underwent CT,10 underwent MRI,and 6 underwent both CT and MRI.Their CT and MRI imaging features were analyzed.Results All 15 cases presented single lesion,including eight boys and seven girls,aged from 1 year 7 months to 14 years and the median age was 8 years(6 years and 4 months to 10 years).Clinical manifestations were slow-growing masses in the soft tissues of the limbs or trunk,of which 11 cases were accompanied by pain,two cases by claudication or activity limitation and two cases by skin bruising.CT showed that the lesions were located in intramuscular,intermuscular or subcutaneous tissues;eight cases were iso-hypo-dense,three cases slightly hyper-dense or mixed-dense,ten cases showed fat density and two cases showed venous stone.MRI showed that the lesions were clearer,with fat signals visible in the internal or peripheral areas.The lesions were well defined,with fat signal inside or around the periphery,located in muscle and growing in a shuttle shape along the long axis of the muscle.The fascial tail sign was seen in six cases.All 15 cases showed significant inhomogeneous enhancement,and increased vascularization was seen around the lesions in four cases.Among the 15 pediatric patients,seven were misdiagnosed as vascular malformations,five as hemangiomas,one as angiolipoma,one as inflammatory myofibroblastoma and one was not qualitatively diagnosed.Conclusion The CT and MRI manifestations of FAVA in children have certain characteristics,but they are still prone to misdiagnosis.When intramuscular lesions are found to grow spindle-shaped along the long-axis,containing fat density/signal and blood vessels or vascular clusters,accompanied by fascial tail sign,combined with clinical manifestations such as pain,the possibility of this disease should be considered.

Purpose To evaluate the effectiveness of deep learning image reconstruction(DLIR)algorithms in reconstructing lumbar vertebrae images from abdominal CT scans,aiming to reduce radiation dose and eliminate the need for repeat lumbar CT examinations.Materials and Methods A retrospective collection was conducted from March to May 2024 in the First Affiliated Hospital of Tianjin University of Traditional Chinese Medicine.Thirty-two patients who underwent both abdominal and lumbar CT scans in a supine head-first position were enrolled.The abdominal CT(DLIR group)utilized a tube voltage of 120 kVp and a current of 200 mA with high-intensity DLIR for lumbar reconstruction.The standard lumbar CT(lumbar group)used the same voltage with a tube current of 260 mA and was reconstructed using 60%weighted adaptive statistical iterative reconstruction.Objective assessments was used to measure the CT values,noise(standard deviation,SD value),signal-to-noise ratio and contrast-to-noise ratio(excluding adipose tissue)at the third lumbar vertebral pedicle level and the L2/L3 intervertebral disc level for muscle,adipose tissue,cancellous bone,intervertebral discs,dura mater and cortical bone.Subjective assessments employed a five-point scale to evaluate image contrast,noise and sharpness.Results The volume CT dose index in lumbar group and DLIR group were 15.25 mGy and 11.74 mGy,respectively.There was no statistical difference in CT values between the structures of both groups(all P>0.05).Compared with the lumbar group,the DLIR group showed significant reductions in SD values across the measured tissues by 31.09%,35.66%,13.48%,27.82%,24.93%and 15.09%(t=5.09-7.21,all P<0.05).The signal-to-noise ratio improved by 36.40%,52.31%,16.56%,34.13%,38.39%and 18.81%,and the contrast-to-noise ratio improved by 51.70%,51.32%,36.24%,34.47%and 53.56%(t=-9.58--4.23,all P<0.001).The DLIR group significantly outperformed the lumbar group in image contrast[4.45(4.00,5.00)points vs.4.75(4.00,5.00)points],image noise[4.06(4.00,4.00)points vs.4.39(4.00,5.00)points],and spatial resolution of fine structures[4.00(4.00,4.00)points vs.4.27(4.00,5.00)points](Z=-3.80,-4.38,-3.55,all P<0.001).Conclusion Using high-intensity DLIR for abdominal examinations can achieve high-quality lumbar CT images with a 25%reduction in radiation dose,enabling simultaneous abdominal and lumbar scanning in a single session.

Cholelithiasis is one of the most common diseases of the digestive system,and the accurate preoperative diagnosis of cholelithiasis is important to guiding treatment and improving prognosis.Dual-energy CT based on material decomposition and post-processing techniques can generate virtual monoenergetic images,virtual noncontrast images,calcium-and fat-based material decomposition images and Rho/Z images which are helpful for detecting isoattenuating gallstones,and offer objective evidence for diagnosing gallstone disease and its complications.This article reviews the principle of dual-energy CT and its progress in cholelithiasis.

Postpartum stress urinary incontinence adversely affects patients'lives and psychological well-being,necessitating timely rehabilitation interventions.Pelvic floor ultrasound holds significant value in the assessment of postpartum stress urinary incontinence.This review article focuses on analyzing the application of pelvic floor ultrasound in the pelvic floor rehabilitation process,including pre-rehabilitation baseline evaluation,auxiliary diagnosis and classification,treatment selection,as well as rehabilitation efficacy assessment and prediction.Additionally,it reviews the current research status of pelvic floor ultrasound in evaluating stress urinary incontinence at different stages of pelvic floor rehabilitation therapy.

After nearly 40 years of development,MRI has become an important imaging diagnostic method in clinical practice.Non-contrast enhanced MRI combined with contrast-enhanced MRI can provide multidimensional information,significantly improving lesion detectability and supporting the entire disease management cycle.With the decentralization of medical resources,contrast-enhanced MR technologies(such as magnetic resonance angiography,dynamic contrast-enhanced MRI and dynamic susceptibility contrast-enhanced MRI,etc.)have become popular in primary healthcare facilities.As a critical adjunct to contrast-enhanced imaging,high-pressure injection technology for contrast agents plays a determinant role in ensuring imaging quality and diagnostic validity.This technology offers distinct advantages in precise control of injection parameters(flow rate,dosage,timing),maintenance of bolus integrity and enhancement of inter-study reproducibility.However,the absence of standardized international and domestic guidelines for its application currently hinders the harmonization of imaging data and limits cross-institutional interoperability of diagnostic results.To address this gap,an expert group has developed the"Expert Consensus on the Application of High-Pressure Injection Technology for Magnetic Resonance Contrast Agents",referencing domestic and international guidelines and literature,and in conjunction with the current application status in the country.This consensus aims to provide radiology professionals with safe and effective technical application guidance and to promote standardized clinical practice.

With the rapid increase in the ownership of MRI equipment in China,quality control,particularly in clinical usage aspects,has become critically important.For clinical quality control of MRI systems,it is essential to establish comprehensive workflow principles encompassing multiple elements such as personnel,equipment,standards,tools and methodologies.To advance the standardization and widespread adoption of clinical quality control for MRI equipment,efforts must focus on strengthening regulatory frameworks,advancing phantom research,development and enhancing professional expertise.Concurrently,continuous improvements in training programs and supervision mechanisms are necessary to ensure the effective implementation of MRI clinical quality control practices.Furthermore,in the era of digital healthcare,clinical quality assurance for MRI equipment is evolving toward automation and intelligent solutions,providing higher-quality and more efficient assurance for clinical applications.

Purpose To explore the feasibility and practical value of using National Institute of Metrology(NIM)calorimetry method to measure whole-body specific absorption rate(SAR)values of in-service MRI equipment.Materials and Methods A NIM calorimetry device for measuring whole-body SAR values was developed,SAR values of different MRI devices were measured by NIM calorimetry,and compared with National Electrical Manufacturers Association(NEMA)calorimetry and pulse-energy method to verify the measurement accuracy and applicability of the NIM calorimetry method.Results The NIM calorimetry device developed in this study had reliable performance,and the experimental results indicated the difference in measurement results between NIM calorimetry(1.63 W/kg)and NEMA calorimetry(1.80 W/kg)was within 10%.The difference between the SAR measurement results of multiple MRI devices based on NIM calorimetry(0.46,0.93,0.61 W/kg)and the pulse energy method(0.42,0.89,0.56 W/kg)was within 10%.Conclusion The NIM calorimetry method in this study can accurately measure whole-body SAR values and has applicability.

Purpose To measure the spatial resolution in MRI quality control testing automatically based on the American College of Radiology(ACR)phantom using the support vector machine(SVM)method,and the feasibility,accuracy and measurement speed of this method are explored.Materials and Methods Quality control tests were performed using eight MRI devices at Beijing Friendship Hospital of Capital Medical University.A retrospective study was conducted on 71 MRI quality control test images collected based on ACR phantoms between 2017 and 2019.The images were preprocessed by binarization,extraction region of interest and so on.An SVM-based classification model was constructed for analyzing the spatial resolution of dot arrays in row and column directions.The dataset was randomly split into a training set and a test set.The generalization performance of the classification model in this study was evaluated through accuracy,precision,recall and F1 score on the test set.Comparing the results of spatial resolution measurements obtained by both manual and automatic method,we demonstrated the feasibility and accuracy of the method.Additionally,the time taken for the automatic spatial resolution measurement was recorded.Results In this study,the proposed method of automatically measuring the spatial resolution of ACR phantom test images using SVM was feasible,high accuracy and short time.In classification performance test,the accuracy of the spatial resolution of the row directional latices was 95%,the precision was 100%.The accuracy of the spatial resolution of the column directional latices was 97%,the precision was 100%.Among the test cases,the results of automatic measurements matched those of manual measurements in 13 out of 14 cases.On average,automatic spatial resolution measurement took 0.158 seconds per case.Conclusion This study achieves automatic measurement of spatial resolution in MRI quality control based on the ACR phantom using SVM method.The method demonstrates high accuracy and fast measurement speeds,holding significant implications for future rapid MRI quality control stability testing.