Quantitative magnetic resonance imaging in prostate cancer:A review of current technology

Prostate cancer(PCa)imaging forms an important part of PCa clinical management.Magnetic resonance imaging is the modality of choice for prostate imaging.Most of the current imaging assessment is qualitative i.e.,based on visual inspection and thus subjected to inter-observer disagreement.Quantitative imaging is better than qualitative assessment as it is more objective,and standardized,thus improving interobserver agreement.Apart from detecting PCa,few quantitative parameters may have potential to predict disease aggressiveness,and thus can be used for prognosis and deciding the course of management.There are various magnetic resonance imaging-based quantitative parameters and few of them are already part of PIRADS v.2.1.However,there are many other parameters that are under study and need further validation by rigorous multicenter studies before recommending them for routine clinical practice.This review intends to discuss the existing quantitative methods,recent developments,and novel techniques in detail.

Future of prostate imaging:Artificial intelligence in assessing prostatic magnetic resonance imaging

Prostate cancer(Pca;adenocarcinoma)is one of the most common cancers in adult males and one of the leading causes of death in both men and women.The diagnosis of Pca requires substantial experience,and even then the lesions can be difficult to detect.Moreover,although the diagnostic approach for this disease has improved significantly with the advent of multiparametric magnetic resonance,that technology has certain unresolved limitations.In recent years artificial intelligence(AI)has been introduced to the field of radiology,providing new software solutions for prostate diagnostics.Precise mapping of the prostate has become possible through AI and this has greatly improved the accuracy of biopsy.AI has also allowed for certain suspicious lesions to be attributed to a given group according to the Prostate Imaging-Reporting&Data System classification.Finally,AI has facilitated the combination of data obtained from clinical,laboratory(prostate-specific antigen),imaging(magnetic resonance),and biopsy examinations,and in this way new regularities can be found which at the moment remain hidden.Further evolution of AI in this field is inevitable and it is almost certain to significantly expand the efficacy,accuracy and efficiency of diagnosis and treatment of Pca.

Discrimination of Metastatic from Non-metastatic Mesorectal Lymph Nodes in Rectal Cancer Using Quantitative Dynamic Contrast-Enhanced Magnetic Resonance Imaging

Preoperative detection of lymph nodes（LNs） metastasis is always highly challenging for radiologists nowadays. The utility of quantitative dynamic contrast-enhanced magnetic resonance imaging（QDCE-MRI） in identifying LNs metastasis is not well understood. In the present study, 59 patients with histologically proven rectal carcinoma underwent preoperative QDCE-MRI. The short axis diameter ratio, long axis diameter ratio, short-to-long axis diameter ratio and QDEC-MRI parameters（Ktrans, Kep, fPV and Ve） values were compared between the non-metastatic（n=44） and metastatic（n=35） LNs groups based on pathological examination. Compared with the non-metastatic group, the metastatic group exhibited significantly higher short axis diameter（7.558±0.668 mm vs. 5.427±0.285 mm）, Ktrans（0.483±0.198 min-1 vs. 0.218±0.116 min^-1） and Ve（0.399±0.118 vs. 0.203±0.096） values（all P〈0.05）. The short-to-long axis diameter ratio, long axis diameter ratio, Kep and fPV values did not show significant differences between the two groups. In conclusion, our results showed that for LNs larger than 5 mm in rectal cancer, there are distinctive differences in the Ktrans and Ve values between the metastatic and non-metastatic LNs, suggesting that QDCE-MRI may be potentially helpful in identifying LNs status.

Quantitative evaluation of diffusion-weighted magnetic resonance imaging of focal hepatic lesions

AIM: To explore the quantitative analysis of diffusionweighted magnetic resonance imaging (DWMRI) in differential diagnosis of focal hepatic lesions.METHODS: DWMRI was performed in 149 hepatic lesions, including hepatocellular carcinoma (34 cases),hepatic metastases (37 cases), cavernous hemangioma (42 cases), hepatic cyst (36 cases). Apparent diffusion coefficient (ADC) values were evaluated using four different b values in different sequences. The ratio of ADC values of lesion/liver in hepatocellular carcinoma and hepatic metastases was also calculated.RESULTS: The mean ADC values of hepatic lesions were as follows: hepatocellular carcinoma (0.95 ± 0.11) × 10-3 mm2/s, hepatic metastasis (1.13 ± 0.21)× 10-3 mm2/s, cavernous hemangioma (1.86±0.36)×10-3 mm2/s,hepatic cyst(3.14±0.31)×10-3 mm2/s. The ratio of ADC values in lesion/liver in hepatocellular carcinoma was 0.91 ±0.11, being significantly different from that in hepatic metastasis (1.21 ± 0.18, P＜ 0.05).CONCLUSION: ADC values and quantitative analysis of focal hepatic lesions are of significant values in differential diagnosis of focal hepatic lesions.

Research progress of magnetic resonance imaging on the correlation between coronary plaque properties and pericoronal fat

Because of the small size of coronary plaque and its continuous beating with the heart,the assessment of the nature of coronary atherosclerotic plaques by magnetic resonance imaging remains a challenge in current research.Recent studies have shown that changes in the pericoronary fat environment are closely related to the nature of coronary atherosclerotic plaques.At present,the new multi-modal magnetic resonance technology can quantitatively assess the changes of pericorral fat environment,which is expected to effectively evaluate the properties of coronary artery plaque.Therefore,it is of greater clinical importance to study pericoronary fat.Advances in the biological significance of pericoronary fat,comparative imaging for pericoronary fat assessment and clinical applications of its imaging will be reviewed.

Evaluation of diffusion weighted imaging of magnetic resonance imaging in small focal hepatic lesions:a quantitative study in 56 cases

Diffusion-weighted imaging (DWI) as a new technique of magnetic resonance imaging (MRI) is used to detect focal hepatic lesions. This study was designed to evaluate the significance of DWI to differentiate focal hepatic lesions less than 3 cm in diameter by the quantitation of apparent diffusion coefficient (ADC) values. METHODS:DWI using 1.5T MRI scanner unit was performed with a spin-echo single-shot echo planar imaging (EPI) in 56 cases of small focal hepatic lesions, including hepatocellular carcinoma (11), hepatic metastatic tumor (15 ), hepatic cavernous hemangioma (14), and hepatic cyst (16).The ADC values of these lesions were calculated respectively. The ratios of the ADC values of lesion/liver in hepatocellular carcinomas and hepatic metastatic tumors were also estimated. RESULTS:The mean ADC values (mm2/s) were (0.93±0.06) ×10-3 in hepatocellular carcinomas, (1.09±0.18)×10-3 in hepatic metastatic tumors,(1.95±0.38)×10-3 in hepatic cavernous hemangiomas, and (3.18±0.33) ×10-3 in hepatic cysts. The ratios of ADC values of lesion/liver were 0.90±0.06 and 1.15±0.14 in hepatocellular carcinoma and hepatic metastatic tumors respectively, which were significantly different (P<0.05). CONCLUSION:The measurement of ADC values and the ratios of ADC values of lesion/liver are helpful in MR diagnosis and differentiation of focal hepatic lesions.

Computed tomography vs liver stiffness measurement and magnetic resonance imaging in evaluating esophageal varices in cirrhotic patients:A systematic review and meta-analysis

BACKGROUND Computed tomography(CT),liver stiffness measurement(LSM),and magnetic resonance imaging(MRI)are non-invasive diagnostic methods for esophageal varices(EV)and for the prediction of high-bleeding-risk EV(HREV)in cirrhotic patients.However,the clinical use of these methods is controversial.AIM To evaluate the accuracy of LSM,CT,and MRI in diagnosing EV and predicting HREV in cirrhotic patients.METHODS We performed literature searches in multiple databases,including Pub Med,Embase,Cochrane,CNKI,and Wanfang databases,for articles that evaluated the accuracy of LSM,CT,and MRI as candidates for the diagnosis of EV and prediction of HREV in cirrhotic patients.Summary sensitivity and specificity,positive likelihood ratio and negative likelihood ratio,diagnostic odds ratio,and the areas under the summary receiver operating characteristic curves were analyzed.The quality of the articles was assessed using the quality assessment of diagnostic accuracy studies-2 tool.Heterogeneity was examined by Q-statistic test and I2 index,and sources of heterogeneity were explored using metaregression and subgroup analysis.Publication bias was evaluated using Deek’s funnel plot.All statistical analyses were conducted using Stata12.0,Meta Disc1.4,and Rev Man5.3.RESULTS Overall,18,17,and 7 relevant articles on the accuracy of LSM,CT,and MRI in evaluating EV and HREV were retrieved.A significant heterogeneity was observed in all analyses(P<0.05).The areas under the summary receiver operating characteristic curves of LSM,CT,and MRI in diagnosing EV and predicting HREV were 0.86(95%confidence interval[CI]:0.83-0.89),0.91(95%CI:0.88-0.93),and 0.86(95%CI:0.83-0.89),and 0.85(95%CI:0.81-0.88),0.94(95%CI:0.91-0.96),and 0.83(95%CI:0.79-0.86),respectively,with sensitivities of 0.84(95%CI:0.78-0.89),0.91(95%CI:0.87-0.94),and 0.81(95%CI:0.76-0.86),and 0.81(95%CI:0.75-0.86),0.88(95%CI:0.82-0.92),and 0.80(95%CI:0.72-0.86),and specificities of 0.71(95%CI:0.60-0.80),0.75(95%CI:0.68-0.82),and 0.82(95%CI:0.70-0.89),and 0.73(95%CI:0.66-0.80),0.87(95%CI:0.81-0.92),and 0.72(95%CI:0.62-0.80),respectively.The corresponding positive likelihood ratios were 2.91,3.67,and 4.44,and 3.04,6.90,and2.83;the negative likelihood ratios were 0.22,0.12,and 0.23,and 0.26,0.14,and 0.28;the diagnostic odds ratios were 13.01,30.98,and 19.58,and 11.93,49.99,and 10.00.CT scanner is the source of heterogeneity.There was no significant difference in diagnostic threshold effects(P>0.05)or publication bias(P>0.05).CONCLUSION Based on the meta-analysis of observational studies,it is suggested that CT imaging,a non-invasive diagnostic method,is the best choice for the diagnosis of EV and prediction of HREV in cirrhotic patients compared with LSM and MRI.

Non-iterative image reconstruction from sparse magnetic resonance imaging radial data without priors

The state-of-the-art approaches for image reconstruction using under-sampled k-space data are compressed sensing based.They are iterative algorithms that optimize objective functions with spatial and/or temporal constraints.This paper proposes a non-iterative algorithm to estimate the un-measured data and then to reconstruct the image with the efficient filtered backprojection algorithm.The feasibility of the proposed method is demonstrated with a patient magnetic resonance imaging study.The proposed method is also compared with the state-of-the-art iterative compressed-sensing image reconstruction method using the total-variation optimization norm.

A multiple-tissue-specific magnetic resonance imaging model for diagnosing Parkinson’s disease: a brain radiomics study

Brain radiomics can reflect the characteristics of brain pathophysiology.However,the value of T1-weighted images,quantitative susceptibility mapping,and R2*mapping in the diagnosis of Parkinson’s disease(PD)was underestimated in previous studies.In this prospective study to establish a model for PD diagnosis based on brain imaging information,we collected high-resolution T1-weighted images,R2*mapping,and quantitative susceptibility imaging data from 171 patients with PD and 179 healthy controls recruited from August 2014 to August 2019.According to the inclusion time,123 PD patients and 121 healthy controls were assigned to train the diagnostic model,while the remaining 106 subjects were assigned to the external validation dataset.We extracted 1408 radiomics features,and then used data-driven feature selection to identify informative features that were significant for discriminating patients with PD from normal controls on the training dataset.The informative features so identified were then used to construct a diagnostic model for PD.The constructed model contained 36 informative radiomics features,mainly representing abnormal subcortical iron distribution(especially in the substantia nigra),structural disorganization(e.g.,in the inferior temporal,paracentral,precuneus,insula,and precentral gyri),and texture misalignment in the subcortical nuclei(e.g.,caudate,globus pallidus,and thalamus).The predictive accuracy of the established model was 81.1±8.0%in the training dataset.On the external validation dataset,the established model showed predictive accuracy of 78.5±2.1%.In the tests of identifying early and drug-naïve PD patients from healthy controls,the accuracies of the model constructed on the same 36 informative features were 80.3±7.1%and 79.1±6.5%,respectively,while the accuracies were 80.4±6.3%and 82.9±5.8%for diagnosing middle-to-late PD and those receiving drug management,respectively.The accuracies for predicting tremor-dominant and non-tremor-dominant PD were 79.8±6.9%and 79.1±6.5%,respectively.In conclusion,the multiple-tissue-specific brain radiomics model constructed from magnetic resonance imaging has the ability to discriminate PD and exhibits the advantages for improving PD diagnosis.

Imaging in multiple myeloma: Computed tomography or magnetic resonance imaging?

Multiple myeloma(MM)is the second most common type of hematological disease with its incidence rising in the elderly.In MM,the extent of the bone disease increases both morbidity and mortality.The detection of lytic bone lesions on imaging,especially computerized tomography(CT)and magnetic resonance imaging(MRI)is crucial to separate asymptomatic from symptomatic MM patients even when no clinical symptoms are present.Although radiology is essential in the staging and management of patients with MM there is still high variability in the choice between MRI and CT.In addition,there is still suboptimal agreement among readers.The potential of medical imaging in MM is largely under-evaluated:artificial intelligence,radiomics and new quantitative methods to report CT and MRI will improve imaging usage.

Comparison Thigh Skeletal Muscles between Snowboarding Halfpipe Athletes and Healthy Volunteers Using Quantitative Multi-Parameter Magnetic Resonance Imaging at Rest

Background：Magnetic resonance （MR） imaging provides a unique,noninvasive diagnostic platform to quantify the physiological and biochemical variables of skeletal muscle at rest.This study was to investigate the difference in thigh skeletal muscles between snowboarding halfpipe athletes and healthy volunteers via multiparametric MR imaging.Methods：A comparative study was conducted between 12 healthy volunteers and 14 snowboarding halfpipe athletes.MR scanning targeted the left leg at the level of the proximal thigh on a 3.0T MR system.The measured parameters compared between the two groups included T1,T2,T2＊ relaxation times,fat fraction （FF）,and cross-sectional area （CSA） of the quadriceps femoris and the hamstring muscles.Statistical analysis was carried out using independent sample t-test.Interrater reliability was also assessed with intraclass correlation coefficients （ICCs）.Results：It was statistically equivalent between two groups in age,body mass index,thigh circumference,calf circumference,systolic blood pressure,and resting heart rate （all P ＞ 0.05）.However,the T1 and T2 values of the hamstring muscles in the athlete group were found to be significantly shorter than those in control group （T1：1063.3 ± 24.1 ms vs.1112.0 ± 38.2 ms in biceps femoris,1050.4 ± 31.2 ms vs.1095.0 ± 39.5 ms in semitendinosus,1053.1 ± 31.7 ms vs.1118.4 ± 40.0 ms in semimembranosus,respectively;T2：33.4 ± 0.7 ms vs.36.1 ± 1.9 ms in biceps femoris,34.6 ± 2.0 ms vs.37.0 ± 1.9 ms in semitendinosus,36.9 ± 1.5 ms vs.38.9 ± 2.4 ms in semimembranosus,respectively;all P ＜ 0.05） although T2＊ relaxation time was detected with no significant difference.The FF of the hamstring muscles was obviously less than the control group （5.5 ± 1.9％ vs.10.7 ± 4.7％,P ＜ 0.001）.In addition,the quadriceps＇ CSA in the athlete group was substantially larger than the control group （8039.0 ± 1072.3 vs.6258.2 ± 852.0 mm2,P ＜ 0.001）.Interrater reliability was excellent （ICC：0.758-0.994）.Conclusion：Multiple MR imaging parameters indicated significant differences between snowboarding halfpipe athletes and healthy volunteers in the thigh skeletal muscles.

Quantitative magnetic resonance imaging biomarkers in oncological clinical trials: Current techniques and standardization challenges

Radiological imaging plays an important role in oncological trials to provide imaging biomarkers for disease staging, stratifying patients, defining dose setting, and evaluating the safety and efficacy of new candidate drugs and innovative treatment. This paper reviews the techniques of most commonly used quantitative magnetic resonance imaging (qMRI) biomarkers (dynamic contrast enhanced, dynamic susceptibility contrast, and diffusion weighted imaging) and their applications in oncological trials. Challenges of incorporating qMRI biomarkers in oncological trials are discussed including understanding biological mechanisms revealed by MRI biomarkers, consideration of rigorous trial design and standardized implementation of qMRI protocols.

Measurement of lateral ventricle volume of normal infant based on magnetic resonance imaging

Background:Many neurophysiological diseases during infancy stage are associated with the morphology and size of the lateral ventricle.This research aims to measure the normal value range of lateral ventricle volume of normal infant and thus provide basic data for clinical treatment.Method:By retrospective analysis of magnetic resonance inspection (MRI) cranial image of 165 infants in the Department of Pediatric Neurosurgery,Beijing Tiantan Hospital,the infants were divided into four groups according to their age,including the first group (1~3 month,n =12),the second group (4~6 month,n =33),the third group (7~9 month,n =51),and the fourth group (10~12 month,n =69).On Neurosoft image workstation,it can measure the sectional area of the lateral ventricle volume at each layer of axis T2W image and calculate the lateral ventricle volume using the Cavalieri method.Moreover,the correlations between lateral ventricle volume and gender,side difference,and month age were analyzed.Results:95% confidence interval of total bilateral ventricle volume of normal infant:11920.22~14,266.28 mm3 for male infant and 9922.22~12,263.17 mm3 for female infant;95% confidence interval of left side ventricle volume:6254.72~7546.94 mm3 for male infant and 5206.03~6479.99 mm3 for female infant;95% confidence interval of right side ventricle volume:5041.56~6743.29 mm3 for male infant and 4695.00~5804.40 mm3 for female infant.The lateral ventricle volume of the male infant was normally larger than that of the female infant (p < 0.05).For both male and female infants,the left side ventricle volume was larger than the right ventricle volume (p < 0.01).There was no significant difference in lateral ventricle volume between infants over 3 months old.Conclusion:The normal value range of lateral ventricle volume of the infant can be obtained via referring MRI image.The lateral ventricle volume of infant varies upon gender and ventricle side.

Combining quantitative and qualitative magnetic resonance imaging features to differentiate anorectal malignant melanoma from low rectal cancer

Background:Distinguishing anorectal malignant melanoma from low rectal cancer remains challenging because of the overlap of clinical symptoms and imaging findings.We aim to investigate whether combining quantitative and qualitative magnetic resonance imaging(MRI)features could differentiate anorectal malignant melanoma from low rectal cancer.Methods:Thirty-seven anorectal malignant melanoma and 98 low rectal cancer patients who underwent preoperative rectal MRI from three hospitals were retrospectively enrolled.All patients were divided into the primary cohort(N=84)and validation cohort(N=51).Quantitative image analysiswas performed on T1-weighted(T1WI),T2-weighted(T2WI),and contrast-enhanced T1-weighted imaging(CE-T1WI).The subjective qualitative MRI findings were evaluated by two radiologists in consensus.Multivariable analysis was performed using stepwise logistic regression.The discrimination performance was assessed by the area under the receiver operating characteristic curve(AUC)with a 95%confidence interval(CI).Results:The skewness derived from T2WI(T2WI-skewness)showed the best discrimination performance among the entire quantitative image features for differentiating anorectal malignant melanoma from low rectal cancer(primary cohort:AUC=0.852,95%CI 0.788–0.916;validation cohort:0.730,0.645–0.815).Multivariable analysis indicated that T2WI-skewness and the signal intensity of T1WI were independent factors,and incorporating both factors achieved good discrimination performance in two cohorts(primary cohort:AUC=0.913,95%CI 0.868–0.958;validation cohort:0.902,0.844–0.960).Conclusions:Incorporating T2WI-skewness and the signal intensity of T1WI achieved good performance for differentiating anorectal malignant melanoma from low rectal cancer.The quantitative image analysis helps improve diagnostic accuracy.

Comparison of magnetic resonance imaging and computed tomography to measure preoperative parameters of children with pectus excavatum

Importance:Pectus excavatum (PE) is the most common thoracic wall deformity in children,we need a method which could be used to evaluate pulmonary functions and effects on development.Objective:To evaluate the use of 3D T 1-weighted (3 DT 1) and mDIXON magnetic resonance imaging (MRI) sequences for measuring the thoracic parameters and morphology of children with PE,comparing the measurements with those made on computed tomography (CT).Methods:This is a retrospective study of children with thoracic deformities who were hospitalized at the Department of Thoracic Surgery of the Heart Center,Beijing Children's Hospital,between June 2014 and June 2015.Chest CT was performed first,with the MRI scanning then being performed 0-3 days later.The mDIXON sequences were obtained in inspiratory and expiratory phases and the 3DT1 sequences were obtained during free breathing.Thoracic volume was measured using the acquired images.Results:The lung volumes measured on mDIXON MRI and CT were highly correlated,with the Haller index not being significantly different between the two methods.Bland-Altman analyses showed that lung,cardiac,and retrosternal parameters were similar between the two methods.Pulmonary parameters were higher with the end-inspiratory phase mDIXON images than with the end-expiratory phase images,as expected,while cardiac parameters were unaffected by the respiratory phase.Interpretation:Thoracic volumes measured on mDIXON MRI in combination with held respiration could reflect lung volume functions and help in observing the movement functions of the lungs and heart.The method could be used instead of CT,avoiding subjecting the patient to potentially harmful radiation.

Subclinical synovitis detected by magnetic resonance imaging and ultrasonography following clinical remission in patients with rheumatoid arthritis:A retrospective study

Background:Subjective residual symptoms persist after clinical remission of rheumatoid arthritis(RA)in Japanese patients.Few studies have examined the relationship between these symptoms and subclinical inflammation using high-sensitivity imaging(musculoskeletal ultrasound[MSUS]and magnetic resonance imaging[MRI]).We examined the relationship between subjective residual symptoms and imaging findings in patients with RA who achieved clinical remission.Methods:We enrolled 30 patients with RA.The primary endpoint was the patients'subjective residual symptoms.The secondary endpoint was the relationship between the aforementioned symptoms and imaging findings.Results:Despite a mean Simplified Disease Activity Index of 1.3,imaging evaluation revealed inflammatory findings.In the multivariate analysis,the Health Assessment Questionnaire Disability Index(HAQ-DI)and pain visual analog scale(VAS)scores were extracted as independent related factors of subjective residual symptoms.The stratified analysis according to HAQ-DI showed a significant difference in synovitis on MRI between patients with and without residual disability(12.0±8.7 vs.5.3±5.3,respectively;p=0.0192).However,MSUS scores showed no significant difference in these two groups.In addition,no significant differences were found in MSUS and MRI scores between patients with and without residual pain VAS.Conclusions:Our findings demonstrated residual synovitis related to patientreported outcomes in patients with RA who achieved clinical remission.In particular,patients with an HAQ-DI score of>0.25 even after achieving clinical remission should be further examined by MRI and/or MSUS for the evaluation of residual synovitis.

Volumetric measurement techniques for assessment of cutaneous neurofibromas:A review

Cutaneous neurofibroma(cNF)is a prevalent clinical manifestation of neurofibromatosis type 1,significantly affecting the well-being and quality of life of the affected individuals.The adoption of reliable and reproducible volumetric measurement techniques is essential for precisely evaluating tumor burden and plays a critical role in the development of effective treatments for cNF.This study focuses on widely used volumetric measurement techniques,including vernier calipers,ultrasound,computed tomography,magnetic resonance imaging,and three-dimensional scanning imaging.It outlines the merits and drawbacks of each technique in assessing the cNF load,providing an overview of their current applications and ongoing research advancements in this domain.

Detection of 100% oxygen induced changes in retina using magnetic resonance imaging： a human study

Background Inner retinal oxygenation response （△PO2） is a worldwide study focus. However, the relevant reports on its radiological measurments are limited. In this study, magnetic resonance imaging （MRI）, employing T1 weighted image （T1WI）, was used to detect changes in APO2 following 100% oxygen inhalation in human subjects. Methods MRI was performed on a 1.5-T GE scanner system. After obtaining ophthalmologic data, eleven healthy individuals were given room air and 100% oxygen inhalation in order with different intervals. The MRI TlWl data were collected for 50 minutes. Data were analyzed with NIH IMAGE software. Results APO2 was not panretinally uniform, and changes in oxygenation response were spatially inhomogeneous. During the initial phase （before 5 minutes） of 100% oxygen inhalation, preretinal vitreous water signals in the region of papilla optica increased rapidly. On the contrary, in other regions signals declined. In a later period （35 minutes）, APO2 was panretinally fluctuated and increased slowly and attained homeostasis. After hyperoxia （45 minutes）, delayed-enhancement of preretinal vitreous water signals in regions other than the papilla optica occurred, and then dropped down. There was no significant difference （P 〉0.05） at any consecutive time point during and after hyperoixa. Conclusions These results reveal that hyperoxia can induce region-specific signal changes in preretinal vitreous water. Regulatory activity of the retinal vessel network may be the mechanism during 100% oxygen inhalation. Moreover, MRI is a valuable tool for investigating APO2 and exploring the mechanism of retinal oxygenation response physiologically or pathologically in vivo.

Quantitative differentiation of malignant and benign thyroid nodules with multi-parameter diffusion-weighted imaging

BACKGROUND The value of conventional magnetic resonance imaging in the differential diagnosis of thyroid nodules is limited;however,the value of multi-parameter diffusion-weighted imaging(DWI)in the quantitative evaluation of thyroid nodules has not been well determined.AIM To determine the utility of multi-parametric DWI including mono-exponential,biexponential,stretched exponential,and kurtosis models for the differentiation of thyroid lesions.METHODS Seventy-nine patients(62 with benign and 17 with malignant nodules)underwent multi-b value diffusion-weighted imaging of the thyroid.Multiple DWI parameters were obtained for statistical analysis.RESULTS Good agreement was found for diffusion parameters of thyroid nodules.Malignant lesions displayed lower diffusion parameters including apparent diffusion coefficient(ADC),the true diffusion coefficient(D),the perfusion fraction(f),the distributed diffusion coefficient(DDC),the intravoxel water diffusion heterogeneity(α)and kurtosis model-derived ADC(Dapp),and higher apparent diffusional kurtosis(Kapp)than benign entities(all P<0.01),except for the pseudodiffusion coefficient(D*)(P>0.05).The area under the ROC curve(AUC)of the ADC(0 and 1000)was not significantly different from that of the ADC(0 and 2000),ADC(0 to 2000),ADC(0 to 1000),D,DDC,Dapp and Kapp(all P>0.05),but was significantly higher than the AUC of D*,f andα(all P<0.05)for differentiating benign from malignant lesions.CONCLUSION Multiple DWI parameters including ADC,D,f,DDC,α,Dapp and Kapp could discriminate benign and malignant thyroid nodules.The metrics including D,DDC,Dapp and Kapp provide additional information with similar diagnostic performance of ADC,combination of these metrics may contribute to differentiate benign and malignant thyroid nodules.The ADC calculated with higher b values may not lead to improved diagnostic performance.

基于MRI定量非对称回波最小二乘估算水脂分离技术的成人腰椎骨髓脂肪与年龄和性别的相关性研究

目的:基于MRI定量非对称回波最小二乘估算水脂分离(iterative decomposition of water and fat with echo asymmetry and least-squares estimation image quantitation,IDEAL-IQ)技术探讨成年人腰椎不同节段骨髓脂肪与年龄和性别的关系。方法:收集298例受检者的MRI IDEAL-IQ脂肪分数图像,其中男性138例,女性160例,年龄20~69岁。将所有患者按照每10岁为一个年龄段分为5组:20~29岁(20~组),男24例,女20例;30~39岁(30~组),男47例,女39例;40~49岁(40~组),男36例,女47例;50~59岁(50~组),男20例,女37例;60~69岁(60~组),男11例,女17例。使用脂肪分数图在GE ADW4.6工作站测量L1~L5的骨髓质子密度脂肪分数(proton density fat fraction,PDFF)。结果:同一年龄组、不同性别间PDFF存在差异,20~、30~、40~组人群中,男性L1~L5椎体PDFF均高于女性(P<0.05);50~组人群中男性L1~L5椎体PDFF与女性的差异无统计学意义(P>0.05);60~组人群,男性L1~L5椎体PDFF均低于女性(P<0.05)。腰椎椎体PDFF与年龄呈正相关,女性(r=0.72,P<0.05)相关性高于男性(r=0.32,P<0.05)。从20~69岁,男性L4 PDFF增长率最大(21.08%),女性L1 PDFF增长率最大(65.68%);男性各椎体PDFF增长主要集中在30~及50~组,其中L1、L4、L5椎体PDFF在50~组增长率最大,L2、L3椎体PDFF在30~岁组增长率最大;女性各椎体PDFF在30~组呈轻微下降趋势,此后各椎体PDFF逐渐升高,增长主要集中在40~、50~、60~三个年龄组,其中50~组增长率最大。结论:成人不同年龄组男女性各椎体脂肪分布存在差异,椎体PDFF增长率也有所不同;腰椎不同节段椎体PDFF均与年龄呈正相关。