Fat-signal suppression in breast diffusion-weighted imaging: the Good, the Bad, and the Ugly.

OBJECTIVES: Fat-signal suppression is essential for breast diffusion magnetic resonance imaging (or diffusion-weighted MRI, DWI) as the very low diffusion coefficient of fat tends to decrease absolute diffusion coefficient (ADC) values. Among several methods, the STIR (short-tau inversion recovery) method is a popular approach, but signal suppression/attenuation is not specific to fat contrary to other methods such as SPAIR (spectral adiabatic (or attenuated) inversion recovery). This article focuses on those two techniques to illustrate the importance of appropriate fat suppression in breast DWI, briefly presenting the pros and cons of both approaches. METHODS AND RESULTS: We show here through simulation and data acquired in a dedicated breast DWI phantom made of vials with water and various concentrations of polyvinylpyrrolidone (PVP) how ADC values obtained with STIR DWI may be biased toward tissue components with the longest T1 values: ADC values obtained with STIR fat suppression may be over/underestimated depending on the T1 and ADC profile within tissues. This bias is also illustrated in two clinical examples. CONCLUSION: Fat-specific methods should be preferred over STIR for fat-signal suppression in breast DWI, such as SPAIR which also provides a higher sensitivity than STIR for lesion detection. One should remain aware, however, that efficient fat-signal suppression with SPAIR requires good B0 shimming to avoid ADC underestimation from residual fat contamination. CLINICAL RELEVANCE STATEMENT: The spectral adiabatic (or attenuated) inversion recovery (SPAIR) method should be preferred over short-tau inversion recovery (STIR) for fat suppression in breast DWI. KEY POINTS: Fat-signal suppression is essential for breast DWI; the SPAIR method is recommended. Short-tau inversion recovery (STIR) is not specific to fat; as a result, SNR is decreased and ADC values may be over- or underestimated. The STIR fat-suppression method must not be used after the injection of gadolinium-based contrast agents.

Fat-suppression T2 relaxation time and water fraction predict response to intravenous glucocorticoid therapy for thyroid-associated ophthalmopathy.

OBJECTIVE: To investigate the value of fat-suppression (FS) T2 relaxation time (T2RT) derived from FS T2 mapping and water fraction (WF) derived from T2 IDEAL to predict the treatment response to intravenous glucocorticoids (IVGC) in patients with thyroid-associated ophthalmopathy (TAO) based on texture analysis. MATERIALS AND METHODS: In this study, 89 patients clinically diagnosed with active and moderate-to-severe TAO were enroled (responsive group, 48 patients; unresponsive group, 41 patients). The baseline clinical characteristics and texture features were compared between the two groups. Multivariate analysis was performed to identify the independent predictors of treatment response to IVGC. ROC analysis and the DeLong test were used to assess and compare the predictive performance of different models. RESULTS: The responsive group exhibited significantly shorter disease duration and higher 90th percentile of FS T2RT and kurtosis of WF in the extraocular muscle (EOM) and 95th percentile of WF in the orbital fat (OF) than the unresponsive group. Model 2 (disease duration + WF; AUC, 0.816) and model 3 (disease duration + FS T2RT + WF; AUC, 0.823) demonstrated superior predictive efficacy compared to model 1 (disease duration + FS T2RT; AUC, 0.756), while there was no significant difference between models 2 and 3. CONCLUSIONS: The orbital tissues of responders exhibited more oedema and heterogeneity. Furthermore, OF is as valuable as EOM for assessing the therapeutic efficacy of IVGC. Finally, WF derived from T2 IDEAL processed by texture analysis can provide valuable information for predicting the treatment response to IVGC in patients with active and moderate-to-severe TAO. CLINICAL RELEVANCE STATEMENT: The texture features of FS T2RT and WF are different between responders and non-responders, which can be the predictive tool for treatment response to IVGC. KEY POINTS: Texture analysis can be used for predicting response to IVGC in TAO patients. TAO patients responsive to IVGC show more oedema and heterogeneity in the orbital tissues. WF from T2 IDEAL is a tool to predict the therapeutic response of TAO.

Improved abdominal T1 weighted imaging at 0.55T.

PURPOSE: Breath-held fat-suppressed volumetric T1-weighted MRI is an important and widely-used technique for evaluating the abdomen. Both fat-saturation and Dixon-based fat-suppression methods are used at conventional field strengths; however, both have challenges at lower field strengths (<1.5T) due to insufficient fat suppression and/or inadequate resolution. Specifically, at lower field strengths, fat saturation often fails due to the short T1 of lipid; and Cartesian Dixon imaging provides poor spatial resolution due to the need for a long ∆TE, due to the smaller ∆f between water and lipid. The purpose of this work is to demonstrate a new approach capable of simultaneously achieving excellent fat suppression and high spatial resolution on a 0.55T whole-body system. METHODS: We applied 3D stack-of-spirals Dixon imaging at 0.55T, with compensation of concomitant field phase during reconstruction. The spiral readouts make efficient use of the requisite ∆TE. We compared this with 3D Cartesian Dixon imaging. Experiments were performed in 2 healthy and 10 elevated liver fat volunteers. RESULTS: Stack-of-spirals Dixon imaging at 0.55T makes excellent use of the required ∆TE, provided high SNR efficiency and finer spatial resolution (1.7 × 1.7 × 5 mm3) compared Cartesian Dixon (3.5 × 3.5 × 5 mm3), within a 17-s breath-hold. We observed successful fat suppression, and improved definition of structures such as the liver, kidneys, and bowel. CONCLUSION: We demonstrate that high-resolution single breath-hold volumetric abdominal T1-weighted imaging is feasible at 0.55T using spiral sampling and concomitant field correction. This is an attractive alternative to existing Cartesian-based methods, as it simultaneously provides high-resolution and excellent fat-suppression.

Acceleration of uterine 3D T2-weighted imaging by compressed SENSE-a multicentre study.

OBJECTIVES: To find the optimal acceleration factor (AF) of the compressed SENSE (CS) technique for uterine isotropic high-resolution 3D T2-weighted imaging (3D-ISO-T2WI). METHODS: A total of 91 female volunteers from the First Affiliated Hospital of Dalian Medical University, Chu Hsien-I Memorial Hospital and Tianjin Institute of Endocrinology, and The Fourth Hospital of Harbin were recruited. A total of 44 volunteers received uterus sagittal 3D-ISO-T2WI scans on 3.0T MRI device with different CS AFs (including SENSE3, CS3, CS4, CS5, CS6, and CS7), 51 received 3D-ISO-T2WI scans with different degrees of fat suppression (none, light, moderate, and severe), while 4 volunteers received both series of scans. Image quality was subjectively evaluated with a 3-point scoring system. Junction zone signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and myometrial SNR were also calculated. Intraclass correlation coefficients were used to analyse the consistency of the measurement results by 2 observers. Analysis of variance test or Friedman rank sum test was used to compare the differences in subjective scores, SNR, and CNR under different AFs/different degrees of fat suppression. RESULTS: Images by AFs of CS3, CS4, and CS5 had the highest SNR and CNR. Among them, CS5 had the shortest scan time. CS5 also had one of the highest subjective scores. There was no significant difference in SNR and CNR among images acquired with different degrees of fat suppression. Also, images with moderate fat suppression had the highest subjective scores. CONCLUSION: The CS5 combined with moderate fat suppression is recommended for routine female pelvic 3D-ISO-T2WI scan. ADVANCES IN KNOWLEDGE: The CS5 has the highest image quality and has the shortest scan time, which is the best AF. Moderate fat suppression has the highest subjective scores. The CS5 and moderate fat suppression are the best combination for a female pelvic 3D-ISO-T2WI scan.

Fat suppression using frequency-sweep RF saturation and iterative reconstruction.

PURPOSE: To introduce an alternative idea for fat suppression that is suited both for low-field applications where conventional fat-suppression approaches become ineffective due to narrow spectral separation and for applications with strong B0 homogeneities. METHODS: Separation of fat and water is achieved by sweeping the frequency of RF saturation pulses during continuous radial acquisition and calculating frequency-resolved images using regularized iterative reconstruction. Voxel-wise signal-response curves are extracted that reflect tissue's response to RF saturation at different frequencies and allow the classification into fat or water. This information is then utilized to generate water-only composite images. The principle is demonstrated in free-breathing abdominal and neck examinations using stack-of-stars 3D balanced SSFP (bSSFP) and gradient-recalled echo (GRE) sequences at 0.55 and 3T. Moreover, a potential extension toward quantitative fat/water separation is described. RESULTS: Experiments with a proton density fat fraction (PDFF) phantom validated the reliability of fat/water separation using signal-response curves. As demonstrated for abdominal imaging at 0.55T, the approach resulted in more uniform fat suppression without loss of water signal and in improved CSF-to-fat signal ratio. Moreover, the approach provided consistent fat suppression in 3T neck exams where conventional spectrally-selective fat saturation failed due to strong local B0 inhomogeneities. The feasibility of simultaneous fat/water quantification has been demonstrated in a PDFF phantom. CONCLUSION: The proposed principle achieves reliable fat suppression in low-field applications and adapts to high-field applications with strong B0 inhomogeneity. Moreover, the principle potentially provides a basis for developing an alternative approach for PDFF quantification.

T2 Relaxation Time in Extraocular Muscles of Patients with Mild Thyroid- Associated Ophthalmopathy: Comparing T2 Mapping With and Without Fat Suppression Using Different Measurement Methods.

OBJECTIVE: This study aimed to compare the parametric value of T2 with and without fat suppression (FS) on T2 mapping for the evaluation of extraocular muscles (EOMs) in mild thyroid-associated ophthalmopathy (TAO). METHODS: We prospectively recruited 44 consecutive patients with mild TAO seen between May 2020 and October 2022 and 26 healthy controls with no history of eye- or thyroid-related or other autoimmune diseases. Patients with mild TAO were subdivided into active and inactive groups based on their clinical activity scores. The T2 of each EOM was measured over a large and small area of interest on T2-mapping images with and without FS. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic efficacy of T2 for detecting TAO activity. RESULTS: The T2 was significantly and heterogeneously higher in the active group than in the inactive and control groups (P < 0.05). FS-T2-mapping images had better signal display within and at the edges of the EOMs than those without FS. It was possible to observe high-signal aggregation visible in the periphery of some EOMs, and the central part showed relatively low signals. The maximum T2 measured in small or large areas with and without FS had good diagnostic efficacy for TAO activity, with that of no-FS being better (the area under the ROC curve of the maximum T2 measured in a small area and a large area without FS was 1.0 and 1.0 and P values of < 0.001 and < 0.001, respectively). CONCLUSION: Maximal T2 with or without FS can facilitate the early clinical detection of mild TAO activity. The maximum T2 in a small area can facilitate active staging of patients with mild TAO.

Use of Dixon in magnetic resonance breast contrast-enhanced T1 weighted high-resolution imaging for mastectomy patients at 3T: A prospective study in single center.

BACKGROUND: For patients with complete breast resection, conventional contrast-enhanced T1-weighted imaging (CE-T1WI) with frequency-selective spectral attenuated inversion recovery (SPAIR) provides limited fat suppression on the postoperative side due to the uneven skin surface, inhomogeneous tissue environment, and frequency-selective feature of the SPAIR scheme, leading to difficulties in precise diagnosis. This study aimed to investigate the image quality and performance of the Dixon method compared with SPAIR in breast high-resolution CE-T1WI for mastectomy patients. MATERIALS AND METHODS: Sixty female patients who had not performed any breast surgeries were randomly selected retrospectively as the control group. Postmastectomy female patients were enrolled to undergone high-resolution CE-T1WI with SPAIR and Dixon breast scans. Subjective scores were rated using a 5-point scale. Objective parameters, including contrast-to-noise ratio (CNR), edge sharpness, and signal uniformity were measured and calculated. The Wilcoxon rank-sum test and Kappa statistic were used. RESULTS: A total of 114 consecutive postmastectomy patients were included. Subjective scores of T1WI-SPAIR in the control group were all significantly better than those with SPAIR on the postoperative side of mastectomy patients (P < 0.01). Dixon outperformed SPAIR with significantly better subjective scores in regards to uniformity and degree of fat-suppression, anatomical structures depiction, lesion conspicuity, and axillary visibility (p < 0.05) in both post- and non-operative sides and bilateral axillary areas through the paired comparison. The objective parameters of Dixon were significantly better than those of SPAIR. CONCLUSION: The Dixon method provided better image uniformity and higher fat suppression efficiency, and showed significant advantages in delineating the anatomical structures, with better axillary and lesion visibilities, especially on the completely removed breast side.

The application value of LAVA-flex sequences in enhanced MRI scans of nasopharyngeal carcinoma: comparison with T1WI-IDEAL.

Introduction: Magnetic resonance imaging (MRI) staging scans are critical for the diagnosis and treatment of patients with nasopharyngeal cancer (NPC). We aimed to evaluate the application value of LAVA-Flex and T1WI-IDEAL sequences in MRI staging scans. Methods: Eighty-four newly diagnosed NPC patients underwent both LAVA-Flex and T1WI-IDEAL sequences during MRI examinations. Two radiologists independently scored the acquisitions of image quality, fat suppression quality, artifacts, vascular and nerve display. The obtained scores were compared using the Wilcoxon signed rank test. According to the signal intensity (SI) measurements, the uniformity of fat suppression, contrast between tumor lesions and subcutaneous fat tissue, and signal-to-noise ratio (SNR) were compared by the paired t-test. Results: Compared to the T1WI-IDEAL sequence, LAVA-Flex exhibited fewer artifacts (P<0.05), better visualization of nerves and vessels (P<0.05), and performed superior in the fat contrast ratio of the primary lesion and metastatic lymph nodes (0.80 vs. 0.52, 0.81 vs. 0.56, separately, P<0.001). There was no statistically significant difference in overall image quality, tumor signal-to-noise ratio (SNR), muscle SNR, and the detection rate of lesions between the two sequences (P>0.05). T1WI-IDEAL was superior to LAVA-Flex in the evaluation of fat suppression uniformity (P<0.05). Discussion: LAVA-Flex sequence provides satisfactory image quality and better visualization of nerves and vessels for NPC with shorter scanning times.

Application of rice bag in 1.5T MR imaging in maxillofacial / 实用放射学杂志

Objective To investigate the application value of rice bag in 1.5T MR imaging of maxillofacial frequency selective saturated fat suppression(FS)sequence.Methods Forty-one patients with maxillofacial MR examination were collected.Rapid fast spin echo(FSE)FS T2 routine scan and rice bag FSE FS T2 special scan were used to evaluate and analyze the sequence images of the two kinds by two experienced associate chief physicians in the department according to the Likert 7-point scoring system.The evaluation included FS,magnetic sensitive artifact,motion artifact,and overall image quality.Wilcoxon sign rank sum test was used to analyze the difference of image quality scores,and Kappa consistency test was used to analyze the correlation between two viewers.Results All the 41 patients completed the examination,and the FSE FS T2 plus rice bag group had significantly higher FS,magnetic sensitive artifact,motion artifact and overall image quality than the conventional FSE FS T2 group,with statistical significance(P<0.01).Kappa consistency was good in correlation analysis between the two viewers(Kappa value=0.737-0.877,P<0.01).Conclusion The application of rice bag in the 1.5T MR maxillofacial FS sequence scan has the advantages of good image quality,good FS effect and few artifacts,which can better display the maxillofacial anatomical structure and lesions,and has important clinical application value for the diagnosis of maxillofacial diseases.

Assessment of ultrashort echo time (UTE) T2* mapping at 3T for the whole knee: repeatability, the effects of fat suppression, and knee position.

Background: Knee tissues such as tendon, ligament and meniscus have short T2* relaxation times and tend to show little to no signal in conventional magnetic resonance acquisitions. An ultrashort echo time (UTE) technique offers a unique tool to probe fast-decaying signals in these tissues. Clinically relevant factors should be evaluated to quantify the sensitivity needed to distinguish diseased from control tissues. Therefore, the objectives of this study were to (I) quantify the repeatability of UTE-T2* relaxation time values, and (II) evaluate the effects of fat suppression and (III) knee positioning on UTE-T2* relaxation time quantification. Methods: A dual-echo, three-dimensional center-out radially sampling UTE and conventional gradient echo sequences were utilized to image gadolinium phantoms, one ex-vivo specimen, and five in-vivo subjects on a clinical 3T scanner. Scan-rescan images from the phantom and in-vivo experiments were used to evaluate the repeatability of T2* relaxation time values. Fat suppressed and non-suppressed images were acquired for phantoms and the ex-vivo specimen to evaluate the effect of fat suppression on T2* relaxation time quantifications. The effect of knee positioning was evaluated by imaging in-vivo subjects in extended and flexed positions within the knee coil and comparing T2* relaxation times quantified from tissues in each position. Results: Phantom and in-vivo measurements demonstrated repeatable T2* mapping, where the percent difference between T2* relaxation time quantified from scan-rescan images was less than 8% for the phantom and knee tissues. The coefficient of variation across fat suppressed and non-suppressed images was less than 5% for the phantoms and ex-vivo knee tissues, showing that fat suppression had a minimal effect on T2* relaxation time quantification. Knee position introduced variability to T2* quantification of the anterior cruciate ligament, posterior cruciate ligament, and patellar tendon, with percent differences exceeding 20%, but the meniscus showed a percent difference less than 10%. Conclusions: The 3D radial UTE sequence presented in this study could potentially be used to detect clinically relevant changes in mean T2* relaxation time, however, reproducibility of these values is impacted by knee position consistency between scans.

Feasibility of the fat-suppression image-subtraction method using deep learning for abnormality detection on knee MRI.

Purpose: To evaluate the feasibility of using a deep learning (DL) model to generate fat-suppression images and detect abnormalities on knee magnetic resonance imaging (MRI) through the fat-suppression image-subtraction method. Material and methods: A total of 45 knee MRI studies in patients with knee disorders and 12 knee MRI studies in healthy volunteers were enrolled. The DL model was developed using 2-dimensional convolutional neural networks for generating fat-suppression images and subtracting generated fat-suppression images without any abnormal findings from those with normal/abnormal findings and detecting/classifying abnormalities on knee MRI. The image qualities of the generated fat-suppression images and subtraction-images were assessed. The accuracy, average precision, average recall, F-measure, sensitivity, and area under the receiver operator characteristic curve (AUROC) of DL for each abnormality were calculated. Results: A total of 2472 image datasets, each consisting of one slice of original T1WI, original intermediate-weighted images, generated fat-suppression (FS)-intermediate-weighted images without any abnormal findings, generated FS-intermediate-weighted images with normal/abnormal findings, and subtraction images between the generated FS-intermediate-weighted images at the same cross-section, were created. The generated fat-suppression images were of adequate image quality. Of the 2472 subtraction-images, 2203 (89.1%) were judged to be of adequate image quality. The accuracies for overall abnormalities, anterior cruciate ligament, bone marrow, cartilage, meniscus, and others were 89.5-95.1%. The average precision, average recall, and F-measure were 73.4-90.6%, 77.5-89.4%, and 78.4-89.4%, respectively. The sensitivity was 57.4-90.5%. The AUROCs were 0.910-0.979. Conclusions: The DL model was able to generate fat-suppression images of sufficient quality to detect abnormalities on knee MRI through the fat-suppression image-subtraction method.

Fascial Signal Change on the Cervical MRI of a Patient with Systemic Lupus Erythematosus.

Here, we present a case of a 53-year-old female patient with chronic neck pain and systemic inflammation who was ultimately diagnosed with systemic lupus erythematosus. Notably, applying fat-suppressed T2-weighted MRI sequences was pivotal in detecting structural fascial changes commonly associated with systemic inflammatory diseases. PET-CT scans further revealed systemic inflammation around multiple joints, providing valuable insights into MRI signal alterations. This case underscores the importance of considering systemic autoimmune pathology as a potential underlying cause of chronic musculoskeletal pain. It also highlights the clinical utility of MRI with fat suppression sequences in identifying inflammation-related fascial changes. This case emphasizes the significance of a comprehensive evaluation, particularly in situations where clinical features overlap between autoimmune and degenerative skeletal pathologies. Fat-suppressed MRI can provide information about fascial pathology related to systemic inflammatory diseases. In this context, it is worth noting that PET-CT and fat suppression MRI complement each other by providing complementary information about inflammation and the underlying causes of a patient's pain.

Differential diagnosis of brucellar spondylitis and tuberculous spondylitis based on FS-T2WI sequence combined with machine learning / 中华地方病学杂志

Objective:To investigate the performance of a predictive model based on fat suppression (FS)-T2WI sequence combined with machine learning in the differential diagnosis of brucellar spondylitis (BS) and tuberculous spondylitis (TS).Methods:The clinical and imaging data of 74 patients with BS and 81 patients with TS diagnosed clinically or pathologically in the First Affiliated Hospital of Xinjiang Medical University from January 2017 to January 2022 were retrospectively analyzed, and all patients underwent spinal magnetic resonance imaging (MRI) examination before treatment. Patients were randomly divided into a training group ( n = 123) and a testing group ( n = 32) in an 8 ∶ 2 allocation ratio, and radiomics feature extraction and dimensionality reduction analysis were performed on FS-T2WI sequence images. Four machine learning algorithms, including K-nearest neighbor (KNN), support vector machine (SVM), random forest (RF) and logistic regression (LR), were used to construct a radiomics model, and receiver operating characteristic (ROC) curve was used to analyze the differential diagnostic performance of each model for BS and TS. Results:A total of 1 409 radiomics features were extracted, and 7 related features were screened and included for identification of BS and TS, among which the Maximum2DDiameterColumn feature value showed a strong correlation, and there was a statistically significant difference between BS and TS patients ( P < 0.001). In the testing group, the area under the ROC curve (AUC) value of the SVM model for identifying BS and TS was 0.886, with a sensitivity of 0.53, a specificity of 0.88, and a diagnostic accuracy of 0.81; in the training group, the AUC value of the SVM model for identifying BS and TS was 0.811, the sensitivity was 0.68, the specificity was 0.72, and the diagnostic accuracy of the model was 0.78. Conclusion:The prediction model based on FS-T2WI sequence combined with machine learning can be used to identify BS and TS, and the diagnostic performance of SVM model is prominent and stable.

Applications of the Dixon technique in the evaluation of the musculoskeletal system / Aplicações da técnica Dixon na prática radiológica do sistema musculoesquelético

Abstract The acquisition of images with suppression of the fat signal is very useful in clinical practice and can be achieved in a variety of sequences. The Dixon technique, unlike other fat suppression techniques, allows the signal of fat to be suppressed in the postprocessing rather than during acquisition, as well as allowing the visualization of maps showing the distribution of water and fat. This review of the Dixon technique aims to illustrate the basic physical principles, to compare the technique with other magnetic resonance imaging sequences for fat suppression or fat quantification, and to describe its applications in the study of diseases of the musculoskeletal system. Many variants of the Dixon technique have been developed, providing more consistent separation of the fat and water signals, as well as allowing correction for many confounding factors. It allows homogeneous fat suppression, being able to be acquired in combination with several other sequences, as well as with different weightings. The technique also makes it possible to obtain images with and without fat suppression from a single acquisition. In addition, the Dixon technique can be used as a quantitative method, allowing the proportion of tissue fat to be determined, and, in more updated versions, can quantify tissue iron.

Resumo A aquisição de imagens com supressão do sinal da gordura é um recurso de grande utilidade diagnóstica, existindo várias sequências capazes de realizá-la. A técnica Dixon, ao contrário de outras técnicas de supressão de gordura, permite suprimir a contribuição do sinal de gordura no pós-processamento e não durante a aquisição, além de permitir a visualização de mapas com a distribuição da água e da gordura. Esta revisão sobre a técnica Dixon almeja ilustrar os princípios físicos básicos, comparar a técnica com outras sequências de ressonância magnética para supressão ou quantificação de gordura, e descrever suas aplicações no estudo de doenças do sistema musculoesquelético. Muitas variantes da técnica Dixon foram desenvolvidas, proporcionando separação mais consistente dos sinais de gordura e água e permitindo correção de muitos fatores de confusão. Permite obter supressão homogênea de gordura, podendo ser adquirida de forma combinada com várias outras sequências, bem como com diferentes ponderações. Esta técnica possibilita também a obtenção de imagens com e sem supressão de gordura a partir de uma única aquisição. Adicionalmente, a técnica Dixon pode ser utilizada como recurso quantitativo, pois permite a mensuração do porcentual de gordura e, em versões mais atualizadas, consegue quantificar ferro tecidual.

Evaluation of Shimming Techniques on MRI Breast Image Quality at 1.5T.

OBJECTIVE: The quality of all clinical MRI is dependent on B0 homogeneity, which is optimized during the shimming part of a prescan or preparatory phase before image acquisition. The purpose of this study was to assess shimming techniques clinically employed for breast MRI across our practice, and to determine factors that correlate with higher image quality for contrast-enhanced breast MRI at 1.5T. METHODS: One hundred consecutive female patients were retrospectively collected with Institutional Review Board approval. Shimming-related parameters, including shim-box placement and shimming gradient offsets were extracted from prior contrast-enhanced 3D fat-suppressed T1-weighted gradient echo image acquisitions. Three breast radiologists evaluated these images for fat saturation, breast density, overall image quality, and artifacts. Technologist experience was also evaluated for variability of shimming. Generalized linear mixed models were used to compare acquisition parameters between fat saturation. P < 0.05 was considered as statistical significance. RESULTS: The percentage of soft tissue inside the field of view (FOV) (ie, Tissue/FOV) in the good fat-saturation group (0.37 ± 0.06) was significantly lower (P < 0.01) than that in the poor fat-saturation group (0.39 ± 0.06). Other shimming-related parameters were found not significantly affecting the fat-saturation outcomes. Technologists with more experience tended to have less variable shimming performance than junior technologists did. CONCLUSIONS: The quality of clinical MRI and especially breast MRI is highly dependent on shimming. Decreasing Tissue/FOV was associated with good image quality (good fat saturation). Optimization of shimming may require manual shimming or higher-order field-correction strategies.

Effects of different fat suppression techniques on introvoxel incoherent motion parameters of the hip / 实用放射学杂志

Objective To investigate the influence of fat suppression technique on the parameters obtained with introvoxel incoherent motion (IVIM)for the normal hip.Methods 47 female volunteers were randomly selected to perform 1.5T MR examination with common sequence and IVIM sequence.The three different Fat suppression techniques:Fat sat,SPAIR and Water Excit were utilized respectively in T2WI sequence and IVIM sequence.The value of signal-to-noise ratio (SNR),contrast-to-noise ratio (CNR),coefficient of variation(CV), ADC,Dfast,Dslowand F values for three methods were calculated and compared quantitatively.The consistency evaluation of these methods were also conducted.Results (1)ADC value and Dslowvalue obtained with the Water Excit method were higher than those with Fat sat and SPAIR statistically(P<0.05),however there was no significant differences between the SNR,CNR,CV,Dfastand F values measured in three fat suppression methods(P>0.05).(2)The results of Fat sat and SPAIR techniques exhibited good consistency.Conclusion In Water Excit technique,overestimation of the ADC and Dslowvalues may be presented,while the IVIM measurement results are not influenced by the use of Fat sat or SPAIR method.

Three-Dimensional Fast Spin-Echo Imaging without Fat Suppression of the Knee: Diagnostic Accuracy Comparison to Fat-Suppressed Imaging on 1.5T MRI

PURPOSE: To evaluate the diagnostic performance of three-dimensional fast spin-echo (3D FSE-Cube) without fat suppression (NFS) for detecting knee lesions, using comparison to 3D FSE-Cube with fat suppression (FS). MATERIALS AND METHODS: One hundred twenty-four patients who underwent 1.5T knee magnetic resonance imaging (MRI) scans and 25 subsequent arthroscopic surgeries were retrospectively reviewed. Using arthroscopic results and two-dimensional images as reference standards, diagnostic performances of 3D FSE-Cube-NFS and FS imaging about lesions of ligament, meniscus, subchondral bone marrow edema (BME), and cartilage were compared. Scan parameters of 3D FSE-Cube imaging were previously optimized by a porcine knee phantom. RESULTS: No significant differences were observed between detection rates of NFS and FS imaging for detecting lesions of meniscus and cartilage (p>0.05). However, NFS imaging had lower sensitivity for detection of medial collateral ligament (MCL) tears, and lower sensitivity and specificity for detection of BME lesions, compared to FS imaging (p<0.05). CONCLUSION: 3D FSE-Cube-NFS imaging showed similar diagnostic performance for detecting lesions of meniscus or cartilage compared to FS imaging, unlike MCL or BME lesions.

Quantitative Assessment and Ligament Traceability of Volume Isotropic Turbo Spin Echo Acquisition (VISTA) Ankle Magnetic Resonance Imaging: Fat Suppression versus without Fat Suppression

PURPOSE: To compare the image quality and ligament traceability in ankle images obtained using Volume Isotropic Turbo Spin Echo Acquisition (VISTA) MRI with and without fat suppression. MATERIALS AND METHODS: The signal-to-noise ratios (SNRs) in images from a phantom and from the ankle of a volunteer were compared. Ten ankles from 10 non-symptomatic volunteers were imaged for comparisons of contrast ratio (CR) and ligament traceability. All examinations were performed using VISTA sequences with and without fat suppression on a 3T MRI scanner. The SNRs were obtained from images with subjects and without subjects (noise-only). Contrast ratios from images of the 10 ankles were acquired between fluid and tendon (F-T), F-cartilage (C), F-ligament (L), fat (f)-T, f-C and f-L. Two musculoskeletal radiologists independently scored the traceability of 7 ligaments, in sagittal, axial and coronal images respectively, based on a 4-point scale (1 as not traceable through 4 as clearly traceable). The Wilcoxon signed-rank test was used to compare the CR. Fisher's exact test and Pearson's chi-squared test were used to compare the ligament traceability. RESULTS: The SNRs did not differ significantly between the two sequences except in bone marrow. VISTA SPAIR showed the higher CR only in F-T (p = 0.04), whereas VISTA showed higher CR in f-T (p = 0.005), f-C (p = 0.005) and f-L (p = 0.005). The calcaneofibular ligament traceability with VISTA was superior to that obtained with VISTA SPAIR (p < 0.05) in all planes. CONCLUSION: VISTA showed significant superiority to VISTA SPAIR in tracing CFL due to the superior CR between fat and ligament.

MR Imaging of the Spine at 3.0T with T2-Weighted IDEAL Fast Recovery Fast Spin-Echo Technique

OBJECTIVE: To compare the iterative decomposition of water and fat with echo asymmetry and the least-squares estimation (IDEAL) method with a fat-saturated T2-weighted (T2W) fast recovery fast spin-echo (FRFSE) imaging of the spine. MATERIALS AND METHODS: Images acquired at 3.0 Tesla (T) in 35 patients with different spine lesions using fat-saturated T2W FRFSE imaging were compared with T2W IDEAL FRFSE images. Signal-to-noise ratio (SNR)-efficiencies measurements were made in the vertebral bodies and spinal cord in the mid-sagittal plane or nearest to the mid-sagittal plane. Images were scored with the consensus of two experienced radiologists on a four-point grading scale for fat suppression and overall image quality. Statistical analysis of SNR-efficiency, fat suppression and image quality scores was performed with a paired Student's t test and Wilcoxon's signed rank test. RESULTS: Signal-to-noise ratio-efficiency for both vertebral body and spinal cord was higher with T2W IDEAL FRFSE imaging (p < 0.05) than with T2W FRFSE imaging. T2W IDEAL FRFSE demonstrated superior fat suppression (p < 0.01) and image quality (p < 0.01) compared to fat-saturated T2W FRFSE. CONCLUSION: As compared with fat-saturated T2W FRFSE, IDEAL can provide a higher image quality, higher SNR-efficiency, and consistent, robust and uniform fat suppression. T2W IDEAL FRFSE is a promising technique for MR imaging of the spine at 3.0T.

Age-related Marrow Conversion and Developing Epiphysis in the Proximal Femur: Evaluation with STIR MR Imaging / 华中科技大学学报（医学）（英德文版）

In order to observe the feature of age-related marrow conversion and maturation of epi-physeal cartilage and analyze the distribution of red and yellow marrow in the proximal femur at STIR MR imaging, STIR and T1 weighted MR imaging of the proximal femur in 52 subjects, aged 4 months to 25 years old, were retrospectively analyzed for the distribution and appearance of red and yellow marrow. The subjects with no known bone marrow abnormalities were divided into 6 age groups. The signal intensity of the marrow in the proximal epiphysis, proximal metaphysis, proximal diaphysis, distal diaphysis and greater trochanter was compared with the signal intensity and homo- geneity of surrounding muscle and fat and graded by two observers. The results showed that the con- version of hematopoietic marrow in the proximal femur followed a well-defined sequence, occurring first in the proximal epiphysis, followed by the distal diaphysis, and then greater trochanter and metaphysis. STIR in combination with T1-weighted imaging could display clearly the origin of ossi-fication center and the course of conversion from red to yellow marrow in proximal epiphysis and greater trochanter. STIR imaging showed that the marrow conversion in proximal metaphysic began below epiphyseal plate and intertrochanter. The site of red yellow was distributed in weight-bearing axis by 20 years of age. The marrow conversion of diaphysis was from distal end to proximal end, and the consequence of conversion was that distal diaphysis contained yellow marrow but proximal diaphysis partly red marrow connected with the red marrow of metaphysic. The epiphyseal cartilage had different characters of signal-intensity with age in STIR sequence. The distribution of red marrow in STIR imaging was more close to that of anatomy than T1-weighted imaging. It was concluded that STIR could dynamically display the feature of morrow conversion and the development of epiphyseal cartilage and accurately reveal the age-related distribution of red and yellow marrow on STIR imag-ing in the proximal femur.