Fat-suppressed T1-weighted Sequences Research Articles

The role of sacro-iliac joint magnetic resonance imaging in the diagnosis of axial spondyloarthritis: focus on differential diagnosis in women.

To review the role of sacro-iliac magnetic resonance imaging (MRI) in the diagnosis of axial spondyloarthritis (AxSpA), with a focus on gender differences. The experience of the authors and the results of an informal literature review are reported. Inflammatory changes of the sacro-iliac joint are the hallmark of AxSpA. Early, non-radiographic sacroiliitis may be diagnosed with MRI through the assessment of bone marrow edema (BMO) as well as concomitant structural damage. The MRI protocol should include three necessary sequences, i.e., fat-saturated T2-weighted sequences on two orthogonal planes, T1-weighted semi-coronal sequence, and fat-suppressed T1-weighted semi-coronal sequence. Inflammatory changes comprise required signs (BMO and/or osteitis) and additional signs, including synovitis (better defined as joint space enhancement), enthesitis, and capsulitis. Structural changes consist of erosions, sclerosis, fat metaplasia, and ankylosis. Due to mechanical axial strain, inflammatory changes in the sacro-iliac joint can be found in healthy individuals, runners, and patients with nonspecific low back pain. The prevalence of BMO is higher in women during pregnancy and postpartum, even 12 months after childbirth, but the extent and distribution of MRI findings may help in the differential diagnosis. Other challenges in the MRI diagnosis of sacroiliitis are subchondral T2 hyperintensity during developmental age, periarticular sclerosis in healthy subjects, or osteitis condensans ilii, and several pathological conditions that may mimic AxSpA, some of which are more frequently found in women. The described diagnostic challenges impose a multidisciplinary approach combining imaging findings with clinical and laboratory data.

Deep Learning-Based Synthesis of Contrast-Enhanced MRI for Automated Delineation of Primary Gross Tumor Volume in Radiotherapy of Nasopharyngeal Carcinoma.

Contrast-enhanced MRIs are necessary to delineate the primary gross tumor volume (GTVp) in radiotherapy of nasopharyngeal carcinoma (NPC). However, using contrast agents to scan contrast-enhanced MRIs is not applicable to some patients due to metal implants or their allergy, and it increases the treatment cost of patients. To address these problems, this work aims at synthesizing contrast-enhance MRIs from unenhanced MRIs by implementing generative adversarial network (GAN). In this work, 324 MRI datasets of patients with NPC were retrospectively collected between September 2016 and September 2017 from a single institute. MRI examinations were performed with un-enhanced T1-weighted (T1) and T2-weighted (T2) sequences, and contrast-enhanced T1-weighted (T1C) and fat-suppressed T1-weighted (T1FSC) sequences. We designed and developed a modified pix2pix network to synthesize T1C (sT1C) and T1FSC (sT1FSC) from real T1. The end of the generator in this network was assembled with multiple heads (the classification head and gradient head) to learn more representation information and features from real images, the discriminator in this network distinguished whether the synthesized image is real and fake and supervised that the generator outputs more realistic synthesized image. We verified the performance of the synthesized images for automated delineation of GTVp. In an independent testing set of 11 patients, the synthesized sT1C and sT1FSC were inputted into the segmentation deep learning network along with their corresponding T1 and T2 sequences to generate GTVp contours. Delineation performance of the synthesized images and real images for automated delineation were evaluated by dice similarity coefficient (DSC), and average surface distance (ASD), using human expert contours as the ground truth. In automated contouring of GTVp for NPC, the segmentation deep learning network using one or two synthesized MRIs showed equivalent performance when compared with the automated contours which generated from four real MRI sequences. Mean DSCs between automated contours by sT1C-replaced or sT1C and sT1FSC-replaced network and ground truth contours were 0.726 ± 0.143 and 0.711 ± 0.157, respectively, slightly inferior to that of contours generated from four real MRI sequences (0.740 ± 0.154, both P >0.05). In terms of mean ASD, there was also no significant difference between automated contours generated from synthesized images and real images (3.056 ± 4.216 mm and 3.537 ± 4.793 mm vs. 3.124 ± 4.637 mm; both P > 0.05). We proposed an MRI-synthesis method based on GAN and the synthesized contrast-enhanced MRIs performed equivalent as the real contrast-enhanced MRIs in the automated delineation of gross tumor volume for radiotherapy of NPC.

Machine Learning Predicts Pathologic Complete Response to Neoadjuvant Chemotherapy for ER+HER2- Breast Cancer: Integrating Tumoral and Peritumoral MRI Radiomic Features.

This study aimed to predict pathologic complete response (pCR) in neoadjuvant chemotherapy for ER+HER2- locally advanced breast cancer (LABC), a subtype with limited treatment response. We included 265 ER+HER2- LABC patients (2010-2020) with pre-treatment MRI, neoadjuvant chemotherapy, and confirmed pathology. Using data from January 2016, we divided them into training and validation cohorts. Volumes of interest (VOI) for the tumoral and peritumoral regions were segmented on preoperative MRI from three sequences: T1-weighted early and delayed contrast-enhanced sequences and T2-weighted fat-suppressed sequence (T2FS). We constructed seven machine learning models using tumoral, peritumoral, and combined texture features within and across the sequences, and evaluated their pCR prediction performance using AUC values. The best single sequence model was SVM using a 1 mm tumor-to-peritumor VOI in the early contrast-enhanced phase (AUC = 0.9447). Among the combinations, the top-performing model was K-Nearest Neighbor, using 1 mm tumor-to-peritumor VOI in the early contrast-enhanced phase and 3 mm peritumoral VOI in T2FS (AUC = 0.9631). We suggest that a combined machine learning model that integrates tumoral and peritumoral radiomic features across different MRI sequences can provide a more accurate pretreatment pCR prediction for neoadjuvant chemotherapy in ER+HER2- LABC.

Prediction of Primary Tumor Sites in Spinal Metastases Using a ResNet-50 Convolutional Neural Network Based on MRI.

We aim to investigate the feasibility and evaluate the performance of a ResNet-50 convolutional neural network (CNN) based on magnetic resonance imaging (MRI) in predicting primary tumor sites in spinal metastases. Conventional sequences (T1-weighted, T2-weighted, and fat-suppressed T2-weighted sequences) MRIs of spinal metastases patients confirmed by pathology from August 2006 to August 2019 were retrospectively analyzed. Patients were partitioned into non-overlapping sets of 90% for training and 10% for testing. A deep learning model using ResNet-50 CNN was trained to classify primary tumor sites. Top-1 accuracy, precision, sensitivity, area under the curve for the receiver-operating characteristic (AUC-ROC), and F1 score were considered as the evaluation metrics. A total of 295 spinal metastases patients (mean age ± standard deviation, 59.9 years ± 10.9; 154 men) were evaluated. Included metastases originated from lung cancer (n = 142), kidney cancer (n = 50), mammary cancer (n = 41), thyroid cancer (n = 34), and prostate cancer (n = 28). For 5-class classification, AUC-ROC and top-1 accuracy were 0.77 and 52.97%, respectively. Additionally, AUC-ROC for different sequence subsets ranged between 0.70 (for T2-weighted) and 0.74 (for fat-suppressed T2-weighted). Our developed ResNet-50 CNN model for predicting primary tumor sites in spinal metastases at MRI has the potential to help prioritize the examinations and treatments in case of unknown primary for radiologists and oncologists.

Development and Evaluation of MR-Based Radiogenomic Models to Differentiate Atypical Lipomatous Tumors from Lipomas

The aim of this study was to develop and validate radiogenomic models to predict the MDM2 gene amplification status and differentiate between ALTs and lipomas on preoperative MR images. MR images were obtained in 257 patients diagnosed with ALTs (n = 65) or lipomas (n = 192) using histology and the MDM2 gene analysis as a reference standard. The protocols included T2-, T1-, and fat-suppressed contrast-enhanced T1-weighted sequences. Additionally, 50 patients were obtained from a different hospital for external testing. Radiomic features were selected using mRMR. Using repeated nested cross-validation, the machine-learning models were trained on radiomic features and demographic information. For comparison, the external test set was evaluated by three radiology residents and one attending radiologist. A LASSO classifier trained on radiomic features from all sequences performed best, with an AUC of 0.88, 70% sensitivity, 81% specificity, and 76% accuracy. In comparison, the radiology residents achieved 60-70% accuracy, 55-80% sensitivity, and 63-77% specificity, while the attending radiologist achieved 90% accuracy, 96% sensitivity, and 87% specificity. A radiogenomic model combining features from multiple MR sequences showed the best performance in predicting the MDM2 gene amplification status. The model showed a higher accuracy compared to the radiology residents, though lower compared to the attending radiologist.

Prediction of lipomatous soft tissue malignancy on MRI: comparison between machine learning applied to radiomics and deep learning

ObjectivesMalignancy of lipomatous soft-tissue tumours diagnosis is suspected on magnetic resonance imaging (MRI) and requires a biopsy. The aim of this study is to compare the performances of MRI radiomic machine learning (ML) analysis with deep learning (DL) to predict malignancy in patients with lipomas oratypical lipomatous tumours.MethodsCohort include 145 patients affected by lipomatous soft tissue tumours with histology and fat-suppressed gadolinium contrast-enhanced T1-weighted MRI pulse sequence. Images were collected between 2010 and 2019 over 78 centres with non-uniform protocols (three different magnetic field strengths (1.0, 1.5 and 3.0 T) on 16 MR systems commercialised by four vendors (General Electric, Siemens, Philips, Toshiba)).Two approaches have been compared: (i) ML from radiomic features with and without batch correction; and (ii) DL from images. Performances were assessed using 10 cross-validation folds from a test set and next in external validation data.ResultsThe best DL model was obtained using ResNet50 (resulting into an area under the curve (AUC) of 0.87 ± 0.11 (95% CI 0.65−1). For ML/radiomics, performances reached AUCs equal to 0.83 ± 0.12 (95% CI 0.59−1) and 0.99 ± 0.02 (95% CI 0.95−1) on test cohort using gradient boosting without and with batch effect correction, respectively. On the external cohort, the AUC of the gradient boosting model was equal to 0.80 and for an optimised decision threshold sensitivity and specificity were equal to 100% and 32% respectively.ConclusionsIn this context of limited observations, batch-effect corrected ML/radiomics approaches outperformed DL-based models.

Whole body magnetic resonance imaging in healthy children and adolescents: Bone marrow appearances of the appendicular skeleton

ObjectiveTo describe the appearances of bone marrow in the appendicular skeleton on fat-suppressed T2-weighted sequences as assessed by whole-body MRI in healthy and asymptomatic children and adolescents. Material and methodsFollowing ethical approval, we assessed the bone marrow of the extremities on water-only Dixon T2-weighted images as part of a whole-body MRI in 196 healthy and asymptomatic children aged 5–19 years. Based on a newly devised and validated scoring system, we graded intensity (0–2 scale) and extension (1–4 scale) of focal high signal bone marrow areas, and divided them into minor or major findings, based on intensity and extension, reflecting their potential conspicuousness in a clinical setting. ResultsIn the upper extremity, we registered 366 areas with increased signal whereof 79 were major findings. In the lower extremities there were 675 areas of increased signal of which 340 were major findings. Hundred-and-fifteen (58.79%) individuals had at least one major finding, mainly located in the hand and proximal humerus, and the feet and knees. We found no differences according to gender, reported hours of sports activity, handedness, or age group, except for more minor findings in the upper extremities amongst 15–18-year-olds as compared to those aged 5–8 years. ConclusionFocal areas of high signal intensity on whole-body MRI, T2-weighted fat suppressed images that, in a clinical setting could cause concern, were seen in more than half of healthy, asymptomatic children and adolescents. Awareness of this is important when interpreting whole-body MRI in this age group, particularly in the assessment of clinically silent lesions.

Abbreviated Gadoxetic Acid-Enhanced MRI for the Detection of Liver Metastases in Patients With Potentially Resectable Pancreatic Ductal Adenocarcinoma.

Gadoxetic acid-enhanced magnetic resonance imaging (MRI) is useful in detecting liver metastases from pancreatic ductal adenocarcinoma (PDAC). However, the long examination time limits its utility in the initial workup of patients with PDAC. To evaluate the incremental value of an abbreviated gadoxetic acid-enhanced MRI for the detection of liver metastases in patients with PDAC. Retrospective. Patients (N=130) with potentially resectable PDAC (women, 58 [44.6%]). 1.5 T and 3T; gradient dual-echo T1-weighted (in-phase and opposed-phase), fat-suppressed fast spin-echo T2-weighted, single-shot echo-planar diffusion-weighted, and three-dimensional fat-suppressed T1-weighted gradient-echo dynamic contrast-enhanced and hepatobiliary phase sequences, as well as contrast-enhanced computed tomography (CECT). Three radiologists independently reviewed three different image sets to detect liver metastases: set 1, CECT alone; set 2, CECT and abbreviated MRI comprising fat-suppressed T2-weighted, diffusion-weighted, and hepatobiliary phase images; and set 3, CECT and standard gadoxetic acid-enhanced MRI. Figure of merit (FOM) was compared using the jackknife alternative free-response receiver operating characteristics, and other per-lesion and per-patient diagnostic parameters for each image set were compared using McNemar's and Fisher's test. P < 0.05 was considered statistically significant. A total of 43 liver metastases were identified in 13 patients. Reader-averaged FOM to detect liver metastases were significantly higher for sets 2 (0.884) and 3 (0.886) than for set 1 (0.609), while they were comparable between sets 2 and 3 (P=0.96). The mean per-patient sensitivities, negative predictive values, and accuracies were significantly higher for sets 2 and 3 than for set 1, while those between sets 2 and 3 were not significantly different (not applicable, P > 0.99, and P > 0.99, respectively). Gadoxetic acid-enhanced MRI combined with CECT had higher diagnostic performance than CECT alone for the detection of liver metastases in patients with PDAC. The incremental values were comparable for the abbreviated MRI and standard MRI. 3 TECHNICAL EFFICACY: Stage 2.

Definitions, pathogenesis, and pharmacological options for bone marrow lesions: an updated review

The term “Bone Marrow Lesions” (BMLs) identifies a pathological state characterized by a structural degeneration of the osteochondral unit (OCU) and by an alteration of the biochemical balance existing between articular cartilage and subchondral bone. These lesions, if they do not resolve spontaneously and if not adequately treated, can give rise to chronic degenerative diseases such as osteoarthritis and, in the most serious cases, evolve into stress fractures. The technique considered to be the gold standard for the detection of BMLs is Magnetic Resonance Imaging (MRI), to which BMLs appear as an area of ill-defined hyperintensity (high signal) in subchondral bone in fat-suppressed T2-weighted sequences, and hypointense areas (low signal) in T1-weighted sequences. There are several pharmacological intervention strategies for the treatment of BMLs, primarily the administration of bisphosphonates, but in recent years Iloprost treatment is also proving to be an effective therapeutic strategy. The aim of this review is to provide further evidence on the sequence of clinical-biological events leading to the appearance of these lesions, and on the current treatment strategies with the best outcome, in order to shed light on the importance of conducting further research in this field, since BMLs are part of a pathological picture characterised by numerous variables.

MR Neurography of Peripheral Nerve Injury in the Presence of Orthopedic Hardware: Technical Considerations.

As the frequency of orthopedic procedures performed each year in the United States continues to increase, evaluation of peripheral nerve injury (PNI) in the presence of pre-existing metallic hardware is in higher demand. Advances in metal artifact reduction techniques have substantially improved the capability to reduce the susceptibility effect at MRI, but few reports have documented the use of MR neurography in the evaluation of peripheral nerves in the presence of orthopedic hardware. This report delineates the challenges of MR neurography around metal given the high spatial resolution often required to adequately depict small peripheral nerves. It offers practical tips, including strategies for prescan assessment and protocol optimization, including use of more conventional two-dimensional proton density and T2-weighted fat-suppressed sequences and specialized three-dimensional techniques, such as reversed free-induction steady-state precession and multispectral imaging, which enable vascular suppression and metal artifact reduction, respectively. Finally, this article emphasizes the importance of real-time monitoring by radiologists to optimize the diagnostic yield of MR neurography in the presence of orthopedic hardware. © RSNA, 2021.

POS0257 TOWARDS A SIMPLIFIED FLUID-SENSITIVE MRI-PROTOCOL IN SMALL JOINTS OF THE HAND IN EARLY ARTHRITIS PATIENTS: RELIABILITY BETWEEN MDIXON AND REGULAR FSE FAT SATURATION MRI-SEQUENCES

Background:MRI facilitates early recognition of rheumatoid arthritis (RA) by depicting inflammation. Contrast-enhanced T1-weighted and T2-weighted fat-suppressed sequences have been sensitive and thus recommended, but are hampered by invasiveness, costs and long scan time. Therefore we introduced a modified Dixon-sequence (mDixon) which is more patient-friendly, reduces cost, and scan times by 83%. However, it is not known if this mDixon-sequence is reliable in relation to regular MRI-sequences with and without contrast (T1- and T2-weighted, respectively).Objectives:We determined the reliability between regular MRI-sequences with and without contrast (T1- and T2-weighted, respectively) and mDixon-MRI in early arthritis patients.Methods:29 early arthritis patients underwent regular fat-suppressed-MRI (T1- and T2-weighted) and mDixon-sequences, of metacarpophalangeal-2-5 and wrist-joints. Two readers scored erosions, osteitis, synovitis and tenosynovitis. Intraclass correlation coefficients (ICCs) between readers, and comparing the two sequences, were studied. Spearman correlations were determined.Results:Performance between the two readers with the regular-MRI sequences, was good to excellent (ICCs all ≥0.88). The between reader ICC was also good to excellent for the mDixon-MRI (ICCs all ≥0.76). Next, ICCs between the two sequences was investigated to determine the reliability of mDixon. ICCs were good to excellent for total RAMRIS score 0.87 (95%CI 0.74-0.94), for erosions 0.88 (95%CI 0.69-0.95), and total inflammation score 0.84 (95%CI 0.69-0.82). The individual MRI-inflammation scores, had ICCs for osteitis 0.97 (95%CI 0.93-0.98), for tenosynovitis 0.78 (95%CI 0.58-0.89), and for synovitis 0.57 (95%CI 0.26-0.77). In addition, scores were highly correlated for total RAMRIS, erosions, and total MRI-inflammation score (ρ=0.82, ρ=0.81, ρ=0.80, respectively).Conclusion:Regular-MRI sequences and mDixon-MRI perform equally well, this suggests that mDixon-sequence is reliable to detect joint inflammation. Thus, this is the first step towards an simplified and abridged MRI-protocol in small hand-joints in early arthritis patients. The ultimate goal will be implementation of this mDixon-MRI sequence. Validation in larger studies is warranted.Disclosure of Interests:None declared

Can MRI differentiate surrounding vertebral invasion from reactive inflammatory changes in superior sulcus tumor?

Vertebral invasion is a key prognostic factor and a critical aspect of surgical planning for superior sulcus tumors. This study aims to further evaluate MRI features of vertebral invasion in order to distinguish it from reactive inflammatory changes. Between 2000 and 2016, a retrospective study was performed at a single institution. All patients with superior sulcus tumors undergoing surgery, including at least two partial vertebrectomies, were included. An expert radiologist evaluated qualitative and quantitative MRI signal intensity characteristics (contrast-to-noise ratio [CNR]) of suspected involved and non-involved vertebrae. A comparison of CNR of invaded and sane vertebrae was performed using non-parametric tests. Imaging data were correlated with pathological findings. A total of 92 surgical samples of vertebrectomy were analyzed. The most specific sequences for invasion were T1 and T2 weighted (92% and 97%, respectively). The most sensitive sequences were contrast enhanced T1 weighted fat suppressed and T2 weighted fat suppressed (100% and 80%). Loss of extrapleural paravertebral fat on the T1-weighted sequence was highly sensitive (100%) but not specific (63%). Using quantitative analysis, the optimum cut-off (p < 0.05) to distinguish invasion from reactive inflammatory changes was CNR > 11 for the T2-weighted fat-sat sequence (sensitivity 100%), CNR > 9 for contrast-enhanced T1-weighted fat-suppressed sequence (sensitivity 100%), and CNR < - 30 for the T1-weighted sequence (specificity 97%). Combining these criteria, 23 partial vertebrectomies could have been avoided in our cohort. Qualitative and quantitative MRI analyses are useful to discriminate vertebral invasion from reactive inflammatory changes. • Abnormal signal intensity in a vertebral body adjacent to a superior sulcus tumor may be secondary to direct invasion or reactive inflammatory changes. • Accurate differentiation between invasion and reactive inflammatory changes significantly impacts surgical planning. T1w and T2w are the best sequences to differentiate malignant versus benign bone marrow changes. The use of quantitative analysis improves MRI specificity. • Using contrast media improves the sensitivity for the detection of tumor invasion.

Accelerated single-shot T2-weighted fat-suppressed (FS) MRI of the liver with deep learning-based image reconstruction: qualitative and quantitative comparison of image quality with conventional T2-weighted FS sequence.

To compare the image quality of an accelerated single-shot T2-weighted fat-suppressed (FS) MRI of the liver with deep learning-based image reconstruction (DL HASTE-FS) with conventional T2-weighted FS sequence (conventional T2 FS) at 1.5 T. One hundred consecutive patients who underwent clinical MRI of the liver at 1.5 T including the conventional T2-weighted fat-suppressed sequence (T2 FS) and accelerated single-shot T2-weighted MRI of the liver with deep learning-based image reconstruction (DL HASTE-FS) were included. Images were reviewed independently by three blinded observers who used a 5-point confidence scale for multiple measures regarding the artifacts and image quality. Descriptive statistics and McNemar's test were used to compare image quality scores and percentage of lesions detected by each sequence, respectively. Intra-class correlation coefficient (ICC) was used to assess consistency in reader scores. Acquisition time for DL HASTE-FS was 51.23 +/ 10.1 s, significantly (p < 0.001) shorter than conventional T2-FS (178.9 ± 85.3 s). DL HASTE-FS received significantly higher scores than conventional T2-FS for strength and homogeneity of fat suppression; sharpness of liver margin; sharpness of intra-hepatic vessel margin; in-plane and through-plane respiratory motion; other ghosting artefacts; liver-fat contrast; and overall image quality (all, p < 0.0001). DL HASTE-FS also received higher scores for lesion conspicuity and sharpness of lesion margin (all, p < .001), without significant difference for liver lesion contrast (p > 0.05). Accelerated single-shot T2-weighted MRI of the liver with deep learning-based image reconstruction showed superior image quality compared to the conventional T2-weighted fat-suppressed sequence despite a 4-fold reduction in acquisition time. • Conventional fat-suppressed T2-weighted sequence (conventional T2 FS) can take unacceptably long to acquire and is the most commonly repeated sequence in liver MRI due to motion. • DL HASTE-FS demonstrated superior image quality, improved respiratory motion and other ghosting artefacts, and increased lesion conspicuity with comparable liver-to-lesion contrast compared to conventional T2FS sequence. • DL HASTE- FS has the potential to replace conventional T2 FS sequence in routine clinical MRI of the liver, reducing the scan time, and improving the image quality.

Noncontrast Magnetic Resonance Radiomics and Multilayer Perceptron Network Classifier: An approach for Predicting Fibroblast Activation Protein Expression in Patients With Pancreatic Ductal Adenocarcinoma.

Fibroblast activation protein (FAP) in pancreatic ductal adenocarcinoma (PDAC) is closely related to the prognosis and treatment of patients. Accurate preoperative FAP expression can better identify the population benefitting from FAP-targeting drugs. To develop and validate a machine learning classifier based on noncontrast MRI for the preoperative prediction of FAP expression in patients with PDAC. Retrospective cohort study. Altogether, 129 patients with pathology-confirmed PDAC undergoing MR scan and surgical resection; 90 patients in a training cohort, and 39 patients in a validation cohort. FIELD STRENGTH/SEQUENCE/3T: Breath-hold single-shot fast-spin echo T2-weighted sequence and unenhanced and noncontrast T1-weighted fat-suppressed sequences. FAP expression was quantified using immunohistochemistry. For each patient, 1409 radiomics features were extracted from T1- and T2-weighted images and reduced using the least absolute shrinkage and selection operator logistic regression algorithm. A multilayer perceptron (MLP) network classifier was developed using the training and validation set. The MLP network classifier performance was determined by its discriminative ability, calibration, and clinical utility. Kaplan-Meier estimates, student's t-test, the Kruskal-Wallis H test, and the chi-square test, univariable regression analysis, receiver operating characteristic curve, and decision curve analysis were used. A log-rank test showed that the survival of patients with low FAP expression (24.43 months) was significantly longer (P < 0.05) than that in the FAP-high group (13.50 months). The prediction model showed good discrimination in the training set (area under the curve [AUC], 0.84) and the validation set (AUC, 0.77). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for the training set were 75.00%, 79.41%, 0.77, 0.86, and 0.66, respectively, whereas those for the validation set were 85.00%, 63.16%, 0.74, 0.71, and 0.80, respectively. The MLP network classifier based on noncontrast MRI can accurately predict FAP expression in patients with PDAC. 2 TECHNICAL EFFICACY: Stage 2.

Intramuscular Orbital Schwannoma With Cystic Degeneration: Serial Changes in MRI Signal Characteristics.

A 37-year-old male with a known history of neurofibromatosis type 2 presented with progressive right-sided proptosis. Serial MRI studies (Fig. 1) from 6 years (Fig. 1A,D), 3 years (Fig. 1B,E), and 1 year (Fig. 1C,F) before presentation demonstrated an enlarging tumor within the medial rectus muscle. On T1-weighted fat-suppressed gadolinium-enhanced sequences, diffuse contrast enhancement (A) was followed by a small patch of hypoenhancement (B, black arrow), and finally a thin peripheral rim of enhancement (C). On T2-weighted fat-suppressed sequences, the lesion initially isointense to muscle (D) developed a small central patch of hyperintensity (E, white arrow), followed by avid hyperintensity filling the tumor (F). The T2 hyperintensity in (E) was thought to represent the histologic Antoni B pattern, which then underwent cystic degeneration to produce the avid T2 hyperintensity in (F). The Antoni A pattern is represented by regions of T2 hypo- or isointensity and contrast enhancement.FIG. 1.: Serial MRI imaging of orbital schwannoma within the right medial rectus muscle, (A,D), 6 years, (B,E), 3 years, and (C,F), 1 year prior to presentation.Surgical resection was performed through a transcaruncular approach with cryoprobe assistance (Fig. 2A). The tumor, which was encased within the medial rectus muscle, leaked clear fluid during removal. Gross examination (Fig. 2B) showed a complete capsule (arrow) with cystic degeneration (dotted line), and histopathologic evaluation confirmed the diagnosis of schwannoma, with Antoni A and B patterns (Fig. 2C and D, respectively), Verocay bodies, and immunohistochemical staining positive for S100 and negative for CD34. At 3 months follow up, the patient’s proptosis was resolved and extraocular motility was intact in all directions of gaze.FIG. 2.: Operative photographs and photomicrographs. A, Intraoperative photograph during tumor removal. B, Gross photograph of bisected tumor. Histopathology of schwannoma with (C), Antoni A and (D), Antoni B patterns.

Textural Characteristics of Biopsy-proven Metastatic Axillary Nodes on Preoperative Breast MRI in Breast Cancer Patients: A Feasibility Study.

To determine the diagnostic accuracy of MRI textural analysis (TA) to differentiate malignant from benign axillary lymph nodes in patients with breast cancer. This was an institutional review board-approved retrospective study of axillary lymph nodes in women with breast cancer that underwent ultrasound-guided biopsy and contrast-enhanced (CE) breast MRI from January 2015 to December 2018. TA of axillary lymph nodes was performed on 3D dynamic CE T1-weighted fat-suppressed, 3D delayed CE T1-weighted fat-suppressed, and T2-weighted fat-suppressed MRI sequences. Quantitative parameters used to measure TA were compared with pathologic diagnoses. Areas under the curve (AUC) were calculated using receiver operating characteristic curve analysis to distinguish between malignant and benign lymph nodes. Twenty-three biopsy-proven malignant lymph nodes and 24 benign lymph nodes were analyzed. The delayed CE T1-weighted fat-suppressed sequence had the greatest ability to differentiate malignant from benign outcome at all spatial scaling factors, with the highest AUC (0.84-0.93), sensitivity (0.78 [18/23] to 0.87 [20/23]), and specificity (0.76 [18/24] to 0.88 [21/24]). Kurtosis on the 3D delayed CE T1-weighted fat-suppressed sequence was the most prominent TA parameter differentiating malignant from benign lymph nodes (P < 0.0001). This study suggests that MRI TA could be helpful in distinguishing malignant from benign axillary lymph nodes. Kurtosis has the greatest potential on 3D delayed CE T1-weighted fat-suppressed sequences to distinguish malignant and benign lymph nodes.

Multiple b-value diffusion-weighted imaging in differentiating benign from malignant breast lesions: comparison of conventional mono-, bi- and stretched exponential models

To prospectively evaluate multiple b-value diffusion-weighted imaging (DWI) in differentiating malignant from benign breast lesions. The study cohort included 103 patients who underwent 3 T magnetic resonance imaging (MRI). The conventional sequences included T1-weighted dynamic contrast-enhanced, T1-weighted and T2-weighted fat-suppressed sequences, single b-value (b=0, 1000 s/mm2) DWI, and multiple b-values (12 values, from 0 to 3,000 s/mm2) DWI. Pathological diagnosis of breast lesions was based on the latest World Health Organization (WHO) guide on the pathology and immunohistochemistry of the breast. SPSS Statistics V19.0 was used for the statistics analysis. The following parameters were calculated: apparent diffusion coefficient (ADC), tissue diffusivity (D), perfusion fraction (f), pseudo-diffusion coefficient (D∗), distributed diffusion coefficient (DDC), and alpha (α) by the same radiologist twice (interval time of 3 months). There was good inter/intra-observer agreement for each of the parameters. The D, D∗, f, DDC, and α values were significantly different among malignant tumours, benign lesions, and normal breast tissue (p<0.05). D, f, DDC, α, and ADC values have good sensitivity and specificity, respectively. In addition, the combined use of D and f or DDC and α has good diagnostic performance. Thus, the applications of the new multi-b DWI variables or combined variables are promising.

MRI of non-specific low back pain and/or lumbar radiculopathy: do we need T1 when using a sagittal T2-weighted Dixon sequence?

ObjectiveTo show that for the MRI workup of non-specific low back pain and/or lumbar radiculopathy, the acquisition of T1-weighted sequences in the sagittal plane could be waived when using an FSE T2-weighted Dixon sequence.Materials and methodsThree musculoskeletal radiologists retrospectively reviewed fifty lumbar spine MRI examinations performed for non-specific low back pain and/or lumbar radiculopathy. Two protocols were separately analyzed in the sagittal plane: a standard protocol (T1-weighted, in-phase, and water-only images of an FSE T2-weighted Dixon sequence) and a simplified protocol (fat-only, in-phase, and water-only images of an FSE T2-weighted Dixon sequence). Eight items usually assessed on T1-weighted sequences were analyzed for each of the vertebrae (n = 250), vertebral endplates (n = 500), vertebral corners (n = 1000), foramina (n = 500), lamina (n = 500), and facet joints (n = 500). Interchangeability of these protocols was tested using the individual equivalence index. A decrease in interobserver agreement of ≥ 5% when one reader used the simplified protocol compared with when both readers used the standard protocol was considered clinically significant. Interreader and intrareader agreement were assessed using kappa statistics. Rates of findings with each protocol were compared using odd ratios.ResultsThe standard and simplified protocols were interchangeable (range of upper bound of the 95%CI of individual equivalence index = 0.25 to 1.38%). Intraprotocol and interprotocol interreader kappa values were similar (0.253–0.671 vs. 0.236–0.723, respectively). Rates of findings were not statistically significantly different (p ≥ 0.074), or were higher with the simplified protocol (p ≤ 0.036).ConclusionIn our target population, a single sagittal T2-weighted Dixon sequence may replace the recommended combination of T1-, T2-, and fat-suppressed T2-weighted sequences.Key Points• In patients with non-specific low back pain or lumbar radiculopathy, spine MRI in the sagittal plane could be limited to a single FSE T2-weighted Dixon sequence, hereby reducing the acquisition time.• A simplified protocol of spine MRI in the sagittal plane combining FSE T2-weighted Dixon sequence provides the same information as a standard protocol including T1-, T2-, and fat-suppressed T2-weighted sequences for the workup of degenerative lumbar spine lesions.• For some findings shown on the simplified protocol, such as focal bone marrow replacement lesions or signs of infection, additional sequences including pre- and post-contrast T1-weighted sequences may be required, as is currently the case when using the standard protocol.

Whole Body Diffusion Weighted MRI (WB DWI) for the Management of Multiple Myeloma: High Concordance between MRI Diffuse Pattern and BONE Marrow Plasma CELL Infiltration RATE

Background: Diffusion-weighted whole body MRI (WB-DWI) is a new functional imaging technique comprising anatomical and functional sequences with an emerging role in the management of multiple myeloma (MM) patients (pts) since it allows highly sensitive detection of diffuse bone marrow (BM) infiltration pattern and focal lesions, avoiding intravenous injections and radiation exposure. The aims of our study were 1) to test the correlation between plasma cells infiltration (BMPC) rate at BM biopsy and the presence of diffuse infiltration pattern at WB-DWI. 2) to compare response according to IMWG criteria and WB-DWI response and to establish the rate of discordancy (WB-DWI progression with increased focal lesions and at least a partial response according to IMWG criteria) Methods: We reviewed data regarding 45 MM patients (pts) observed in our Centre between September 2018 and July 2019 for whom quantification of serum and urine monoclonal component (MC), free light chains value (FLC), BM biopsy, whole body CT scan and WB-DWI data were available at the same time point. Sequential assessment of WB-DWI and laboratory data was available in 20 pts. Patients performed a WB-DWI (Magnetom Area, 1.5T, Siemens Enlarged Germany) for head to knee. The protocol included anatomical sequences T1 and T2 weighted with fat suppression on the sagittal plane specifically for the spine. Coronal T2 weighted fat suppression sequences are performed for the study of femural bone. Axial Dixon T1 weighted sequences of the whole scan region, in breath-old. The functional part is formed by diffusion weighted sequences in the axial plane. MM diagnosis and response were assessed by IMWG criteria. Response were categorized as follows: responsive patients if ≥PR, progressive disease if &lt;PR. BM infiltration rate was used as a continuous variable. WB-DWI findings at first evaluation were categorized as follows: presence/absence of focal lesions, presence/absence of diffuse pattern of BM infiltration. Radiological re-assessment of both focal lesions and diffuse pattern was categorized as follows: reduced/stable/increased. Discordant pattern of progression was defined as: ≥PR + diffuse pattern stable/reduced + focal lesions increased. Association between two categorical variables was evaluated by Fisher's exact test. Mann-Whitney test was used to compare a quantitative variable among two independent groups of patients. P-values&lt;0.05 were considered significant. Results: Table 1 summarizes the clinical and radiological data of the population on study. Median age was 64 years (range 38-86), median number of previous lines of therapy at time of evaluation was 0 (range 0-)2; 47% pts were at the onset, 31% were in follow-up after treatment completion, 22% had progressive disease. WB-DWI showed a diffuse pattern in 22 pts (49%); in 23 patients without a diffuse pattern, 7 (30%) had PBMC &gt;10%; BMPC infiltration rate was significantly higher in pts with presence of diffuse pattern at WB-DWI (p&lt;0.001; Figure 1). WB-DWI showed focal lesions in 35 pts (78%): 19 of them were at onset of disease. Most of the patients performing sequential assessment of WB-DWI were responsive according to IMWG criteria at time of WB-DWI re-evaluation (17 pts with ≥PR, 85%). Table 2 shows radiological findings according to IMWG response. Focusing on patients with ≥PR, WB-DWI diffuse pattern was reduced in 13 pts (76.5%) and stable in 4 pts (23.5%) with complete concordance between hematological and radiological findings (increased diffuse pattern in no pt with ≥PR); focal lesions were reduced in 76.5% and increased in 23.5%; a discordant pattern of progression was found in 4 patients (20%). Conclusions: Our study findsa significant correlation between presence of WB-DWI diffuse infiltration patter and BMPC rate, highlighting the possible future use of this radiological technique for monitoring BM residual disease. In addition, this study shows the possible not negligible emergence of discordant pattern of progression, probably deriving from the spatial heterogeneity of MM clones and their different sensitivity to therapy. Disclosures Mangiacavalli: celgene: Consultancy; Janssen cilag: Consultancy; Amgen: Consultancy. Varettoni:Gilead: Other: travel expenses; ABBVIE: Other: travel expenses; Roche: Consultancy; Janssen: Consultancy. Arcaini:Celgene: Speakers Bureau; Celgene, Roche, Janssen-Cilag, Gilead: Other: Travel expenses; Gilead Sciences: Research Funding; Bayer, Celgene, Gilead Sciences, Roche, Sandoz, Janssen-Cilag, VERASTEM: Consultancy.

High-concentration iodinated contrast media for T1-weighted direct magnetic resonance arthrography

To quantify invitro the T1-weighted (T1W) expression of iodinated contrast media (CM), and to compare the invivo performances of iodinated CM and gadolinium-based CM for T1W direct magnetic resonance imaging (MRI) arthrography. An invitro study on a 1.5 T MRI system was performed using Gd-DOTA, a mixture of iopromide and Gd-DOTA, and iopromide alone. The fat-suppressed (FS) T1W signal intensities were measured and analysed. In an invivo study, 15 normal rabbits were used to compare the expression of iopromide (370 mg iodine/ml), and the mixture of iopromide and diluted Gd-DOTA. In nine of the 15 rabbits, extra-articular administrations of CM were performed to mimic the situation of CM leak. The rabbits were scanned on a 1.5 T MRI system, and the FS T1W sequence and an axial iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) T1W sequence were acquired. Signal intensities were measured and signal-to-noise ratios (SNR) were analysed. In the invitro study, a higher SNR was noted in a higher concentration of iopromide, and the highest SNR of iopromide was 45.9% of that of Gd-DOTA. In the invivo study, the iopromide and the mixture were well identified in all rabbits. The SNRs of the intra-articular and extra-articular iopromide and the mixture were significantly higher than the SNR of the muscles in the FS T1W images (all, p<0.01) and the IDEAL images (all, p<0.01). A high-concentration iodinated CM can provide good imaging quality for T1W direct MRI arthrography, and may be an alternative option in certain clinical situations.