SPGR Sequence Research Articles

Teknik Pemeriksaan MRI Genu Dengan Penambahan Sequence Axial 3D Spoiled Gradient Recalled Echo

Magnetic Resonance Imaging (MRI) is a medical diagnostic imaging technique that works on the principle of nuclear magnetic resonance. MRI aircraft can produce diagnostic images of the inside of the human body in both sagittal, coronal, and transverse cuts, Magnetic resonance imaging (MRI) is a widely accepted non-invasive technique for the evaluation of cartilage lesions. The femur, tibia, fibula, and patella are united into one complex group by ligaments. According to Moeller, Genu Examination uses STIR Sequence, Sagital T2 Weighted Fat saturated, Sagittal 3D GRE, Proton Density weighted fat saturated T1 Coronal. The author's purpose in conducting this study is because Genu Examination at one of the Jakarta Hospital in the Case of Soft Tissue Tumor, Meniscus Tear and Oesteoarthritis added the Axial 3D SPGR sequence. The research method used is descriptive research with an observational approach. Data collection was carried out on June 5 to August 31 using Mri GE aircraft with a power of 1.5 Tesla. The patient samples used in this study were three patients with clinical Soft Tissue Tumor, Meniscus Tear, and Osteoarthritis. Data collection was carried out through observation, interviews and Genu Examination Documentation with the addition of Axial 3D SPGR. The examination is carried out using Quad Knee Coil, the patient's position is supine, feet first. The sequences used in the examination at one of the Jakarta hospitals are Axial Proton Density Fat saturated, Sagital Proton Density Fat saturated, Sagital T2, Coronal Proton Density Fat saturated, Coronal STIR. The role of the Axial 3D SPGR sequence is to evaluate articular cartilage due to its clear depiction of cartilage morphology and high signal to noise ratio (SNR) images.

DYNAMIC CONTRAST-ENHANCED MRI OF THE SYNOVIUM IN KNEE OSTEOARTHRITIS: SEMI-AUTOMATIC SEGMENTATION OF SYNOVIAL SUBREGIONS AND TEST-RETEST REPEATABILITY

Inflammation of the joint lining (synovitis) is often seen in OA, and is strongly associated with both knee pain severity and disease progression. Dynamic contrast-enhanced MRI (DCE-MRI) can be used to visualize the uptake and washout of gadolinium-based contrast, and enables quantification of blood perfusion as a surrogate measure of inflammation. DCE-MRI could therefore be used to characterize the extent of synovitis and serve as a biomarker for response to treatment in clinical trials. However, (semi)-automatic segmentation methods and thorough technical and clinical validation are needed to fully adopt DCE-MRI in this setting. We aim to evaluate semi-automatic segmentation of synovial subregions and test-retest repeatability of DCE-MRI to measure synovial perfusion in patients with knee OA. Patients with mild-to-moderate knee OA (KLG 1-3) who were allocated to the control group in a prospective randomized controlled trial of genicular artery embolization were included. Patients underwent MRI at 3T (GE Healthcare) at baseline and after 1 month. Image acquisition consisted of native T1 mapping with variable flip angle, followed by a dual-echo SPGR sequence (DISCO; DIfferential Sub-sampling with Cartesian Ordering), in which the spatial resolution was optimized to allow for visualization of small vessels. After the initial phase, 0.1 ml/kg gadovist was injected and subsequently 34 dynamic phases were acquired, with a temporal resolution of 10.2 seconds. Segmentation of the synovium comprised an initial rough manual segmentation followed by selection of enhancing voxels using a shuffle transform method. Synovial subregions were created by semi-automatic vessel mapping using MeVisLab and mathematically assigning synovial voxels to the corresponding closest genicular artery. Motion compensation was performed using Elastix (Elastix, version 5.0.1), and native T1 mapping and pharmacokinetic modelling was done using open source software for DCE analysis (MADYM, version 4.21.1). The commonly used combination of the Parker literature arterial input function, and the Extended Toft's model pharmacokinetic model was implemented. Voxelwise perfusion parameters were calculated, after which median Ktrans values were extracted for the whole synovium and separately for each synovial subregion. Agreement was visualized with a Bland-Altman plot, and test-retest repeatability was evaluated using intraclass correlation coefficients (ICC; single rating random sample) and within-subject coefficients of variation (CV). 30 patients were included, of which two patients were lost to follow-up and one patient was excluded due to errors during image acquisition. For the remaining 27 participants, median Ktrans values ranged from 0.017 to 0.121. ICC of Ktrans for the whole synovium was 0.51, and CV was 0.14. Sensitivity analysis by exclusion of two statistical outliers yielded an ICC of 0.66 and a CV of 0.11. For the individual synovial regions, ICCs ranged between 0.27 and 0.58 while CVs ranged between 0.13 and 0.25. Semi-automatic segmentation of the synovium and synovial subregions through vessel mapping on DCE-MRI in knee OA is feasible. Perfusion parameters determined through pharmacokinetic modeling have moderate repeatability and should be interpreted with caution. Stichting Coolsingel, Cook Medical, Erasmus MRace Doelmatigheid E.H.G. Oei has received research support from GE Healthcare. The University of Wisconsin receives research support from Bracco Diagnostics. CORRESPONDENCE ADDRESS: [email protected]

Managing the effect of magnetic resonance imaging pulse sequence on radiomic feature reproducibility in the study of brain metastases

Background: Despite the promise of radiomics studies, their limited reproducibility has hindered meaningful clinical translation. Variability in study designs as well as image acquisition and processing contribute to unreproducible radiomic results. This work’s purpose was to (i) quantitatively compare variability of radiomic features extracted from 2-D spin echo (SE) and 3-D spoiled gradient echo (SPGR) T1-weighted post-contrast magnetic resonance (MR) images of brain metastases acquired within the same patient in a single imaging session, and (ii) provide a framework to inform data acquisition for reproducible radiomics studies. Methods: A retrospective cohort of 29 patients with pathologically-confirmed brain metastases and contrast-enhanced T1-weighted MR images acquired using 2-D SE and 3-D SPGR sequences within one exam was identified. Metastases were segmented twice by different physicians using semi-automated methods. Radiomic features were extracted using PyRadiomics for 264 preprocessing variable combinations. Lin’s concordance correlation coefficient (CCC) was computed between features extracted from images acquired by both pulse sequences and different tumor segmentations. Results: We provided general recommendations to improve MR-based radiomic feature reproducibility by clustering and identifying low-concordance features and processing variables. Median CCC between 2-D SE and 3-D SPGR (measuring feature agreement between pulse sequences) was greater for fixed bin count intensity discretization (0.76 versus 0.63) and specific high-concordance features (0.74 versus 0.53). Applying all recommendations improved median CCC from 0.51 to 0.79. Median CCC between contours (measuring feature sensitivity to inter-observer variability) was higher for 2-D SE (0.93 versus 0.86) but improved to 0.93 for 3-D SPGR after low-concordance feature exclusion. Conclusions: The following recommendations are proposed to improve reproducibility: 1) Fixed bin count intensity discretization for all studies, 2) for studies with 2-D and 3-D datasets, excluding high-variability features from downstream analyses, 3) when segmentation is manual or semi-automated, using only 2-D SE images or excluding features susceptible to segmentation variability.

Motion modeling from 4D MR images of liver simulating phantom.

Background and purposeA novel method of retrospective liver modeling was developed based on four‐dimensional magnetic resonance (4D‐MR) images. The 4D‐MR images will be utilized in generation of the subject‐specific deformable liver model to be used in radiotherapy planning (RTP). The purpose of this study was to test and validate the developed 4D‐magnetic resonance imaging (MRI) method with extensive phantom tests. We also aimed to build a motion model with image registration methods from liver simulating phantom images.Materials and methodsA deformable phantom was constructed by combining deformable tissue‐equivalent material and a programmable 4D CIRS‐platform. The phantom was imaged in 1.5 T MRI scanner with T2‐weighted 4D SSFSE and T1‐weighted Ax dual‐echo Dixon SPGR sequences, and in computed tomography (CT). In addition, geometric distortion of the 4D sequence was measured with a GRADE phantom. The motion model was developed; the phases of the 4D‐MRI were used as surrogate data, and displacement vector fields (DVF's) were used as a motion measurement. The motion model and the developed 4D‐MRI method were evaluated and validated with extensive tests.ResultThe 4D‐MRI method enabled an accuracy of 2 mm using our deformable phantom compared to the 4D‐CT. Results showed a mean accuracy of <2 mm between coordinates and DVF's measured from the 4D images. Three‐dimensional geometric accuracy results with the GRADE phantom were: 0.9‐mm mean and 2.5 mm maximum distortion within a 100 mm distance, and 2.2 mm mean, 5.2 mm maximum distortion within a 150 mm distance from the isocenter.ConclusionsThe 4D‐MRI method was validated with phantom tests as a necessary step before patient studies. The subject‐specific motion model was generated and will be utilized in the generation of the deformable liver model of patients to be used in RTP.

MR Imaging Provides Practical Information for Preoperative Assessment of Radial Polydactyly with Bifurcation at the Metacarpophalangeal Joint Level.

PurposeWe aimed to evaluate the use of magnetic resonance imaging (MRI) to visualize unossified bone sites that are often not visible with radiography in pediatric radial polydactyly patients with bifurcation at the metacarpophalangeal (MP) joint level. The MRI validation could help in planning for surgical procedures.Patients and MethodsA total of 141 thumbs in 139 pediatric patients with bifurcation at the MP joint on radiography were included in this study. All the patients had undergone MRI with proton density-weighted fat-suppressed fast spin-echo (FS PDWI) sequence and fast fat-suppressed 3D spoiled gradient-recalled echo (FS 3D SPGR) sequence. The MR images of the cartilaginous structure and joint characteristics at the MP joint were evaluated and categorized by two experienced radiologists.ResultsOur analysis demonstrated that MR imaging, especially the FS 3D SPGR sequence, yields better visibility of the cartilaginous structure and shows clearer joint characteristics that could not be detected by radiography. The abnormalities included a cartilaginous connection on the base of duplicated proximal phalanx, cartilaginous joint connection and the shape of articular cartilage on the head of metacarpal and soft tissue band. Radiologically encountered duplications at the MP joint level were successfully classified into six types based on the MRI-detected structural changes. The distribution of the six types was 17.7% (25/141) in type 1, 53.9% (76/141) in type 2, 2.8% (4/141) in type 3, 9.9% (14/141) in type 4, and 13.5% (19/141) in type 5.ConclusionThis data showed that MR imaging provides practical information on the anatomic characteristics in radial polydactyly with bifurcation at the MP joint level that could aid surgical decision-making processes. Thus, the FS 3D SPGR sequence could be used as a MR imaging technique in radial polydactyly.

CT-like MRI: a qualitative assessment of ZTE sequences for knee osseous abnormalities.

To qualitatively evaluate the utility of zero echo-time (ZTE) MRI sequences in identifying osseous findings and to compare ZTE with optimized spoiled gradient echo (SPGR) sequences in detecting knee osseous abnormalities. ZTE and standard knee MRI sequences were acquired at 3T in 100 consecutive patients. Three radiologists rated confidence in evaluating osseous abnormalities and image quality on a 5-grade Likert scale in ZTE compared to standard sequences. In a subset of knees (n = 57) SPGR sequences were also obtained, and diagnostic confidence in identifying osseous structures was assessed, comparing ZTE and SPGR sequences. Statistical significance of using ZTE over SPGR was characterized with a paired t-test. Image quality of the ZTE sequences was rated high by all reviewers with 278 out of 299 (100 studies, 3 radiologists) scores ≥ 4 on the Likert scale. Diagnostic confidence in using ZTE sequences was rated "very high confidence" in 97%, 85%, 71%, and 73% of the cases for osteophytosis, subchondral cysts, fractures, and soft tissue calcifications/ossifications, respectively. In 74% of cases with osseous findings, reviewer scores indicated confidence levels (score ≥ 3) that ZTE sequences improved diagnostic certainty over standard sequences. The diagnostic confidence in using ZTE over SPGR sequences for osseous structures as well as abnormalities was favorable and statistically significant (p < 0.01). Incorporating ZTE sequences in the standard knee MRI protocol was technically feasible and improved diagnostic confidence for osseous findings in relation to standard MR sequences. In comparison to SPGR sequences, ZTE improved assessment of osseous abnormalities.

RESEARCH ON KNEE SPORTS INJURY CLASSIFICATION BASED ON MEDICAL IMAGES AND KWON3D SOFTWARE

ABSTRACT Introduction: The integrity of articular cartilage determines the functional state of the joint. In recent years, the development of MRI sequences of various articular cartilage has become the focus of many research topics. Objective: The accuracy of diagnosis of knee cartilage injury caused by motion injury was studied retrospectively by meta-three-dimensional software. Methods: Forty-six knee joints of 45 patients with sports injuries, multi-sequence MRI was performed before surgery, including conventional knee MRI (SET1WI, FSEPD/T2WI), 3D SPGR, and 3D FIESTA sequences. Results: According to the operation results, the sensitivity, specificity, positive predictive value, and negative predictive value of 3D SPGR combined with conventional MRI sequence evaluation of cartilage damage are the highest, 73%, 98%, 95%, and 90%. Conclusions: 3D SPGR combined with conventional MRI sequences can improve accurate evaluation and diagnosis of cartilage disease over a reasonable scan time. Level of evidence II; Therapeutic studies - investigation of treatment results.

Influence of Magnetic Field Strength on Magnetic Resonance Imaging Radiomics Features in Brain Imaging, an In Vitro and In Vivo Study.

BackgroundThe development and clinical adoption of quantitative imaging biomarkers (radiomics) has established the need for the identification of parameters altering radiomics reproducibility. The aim of this study was to assess the impact of magnetic field strength on magnetic resonance imaging (MRI) radiomics features in neuroradiology clinical practice.MethodsT1 3D SPGR sequence was acquired on two phantoms and 10 healthy volunteers with two clinical MR devices from the same manufacturer using two different magnetic fields (1.5 and 3T). Phantoms varied in terms of gadolinium concentrations and textural heterogeneity. 27 regions of interest were segmented (phantom: 21, volunteers: 6) using the LIFEX software. 34 features were analyzed.ResultsIn the phantom dataset, 10 (67%) out of 15 radiomics features were significantly different when measured at 1.5T or 3T (student’s t-test, p < 0.05). Gray levels resampling, and pixel size also influence part of texture features. These findings were validated in healthy volunteers.ConclusionsAccording to daily used protocols for clinical examinations, radiomic features extracted on 1.5T should not be used interchangeably with 3T when evaluating texture features. Such confounding factor should be adjusted when adapting the results of a study to a different platform, or when designing a multicentric trial.

49 Performance Assessment of Magnetic Resonance Imaging (MRI) pelvimetry using ex vivo anatomic pieces and a 3D-printed geometric-distortion phantom

Introduction Feto-maternal morbidity and mortality increase with prolonged labor which can be related with fetalpelvic disproportion. Pelvimetric imaging is useful for assessing the eligibility of vaginal delivery in patients suspected of having disproportion [1] . Commonly performed using Computed Tomography (CT), pelvimetry is being increasingly done in MRI in order to tackle issues of ionizing-radiation exposure and take advantage of the rich contrast provided in MRI [2] . Nonetheless, MR images can be subjected to geometric distortions because of hardware design limitations [3] . Such distortions may impair MRIpelvimetric measurements. In this study, we assessed the accuracy of MRI-pelvimetry compared with CTpelvimetry using ex-vivo pelvises and a 3D-printed geometric-distortion phantom. Method We scanned ten ex-vivo pelvises on a CT scanner (Siemens Sensation) using the implemented clinical low-dose (LD-CT) and high-dose (HD-CT) pelvimetry protocol. MRI was performed on four 1.5T MRI scanners (Siemens Avanto, GE Signa, Philips Achieva, Toshiba Elan). Pelvises were scanned in sagittal and oblique axial using T1-, T2-weighted FSE and T1-weighted SPGR sequences. A trained radiologist performed pelvimetry measurements. Pelvic inlet and outlet anteroposterior diameters were measured using sagittal images. Pelvic inlet and outlet transverse diameters were measured using oblique axial images. For data analysis, MRI measurements were compared with CT using Bland-Altman plots and discrepancy analysis. MRI measurements were also analyzed for inter-scanner variability. Geometric distortion (GD) measurement: we used a custom previously-published methodology which relies on a 3D-printed phantom made up of 3621 control points which are 5 mm-diameter spheres equally spaced within a cylinder (diameter = length = 170 mm) [4] . GD images were acquired on the Siemens Avanto MR unit with and without the manufacturer’s correction that is available but commonly unused by clinical teams. Results The discrepancy between LD-CT and HD-CT measurements was up to 10%. The discrepancy between MRI and LD-CT was up to 11%. As for MRI and HD-CT, the discrepancy was up to 7%. MRI inter-scanner variation was up to 8%. As for geometric distortions, measurements were −1.4 mm Conclusion For pelvimetry purposes, our preliminary results show that MRI is as much accurate as high-dose CT and outperforms low-dose CT. We also show that geometric distortions can be minimized in MR images by using the implemented corrections. Hence MRI pelvimetry appears as an excellent alternative to CT pelvimetry in an endeavor to reduce fetuses exposure to ionizing radiation. Upcoming works in this study include assessment of interobserver reproducibility with the intervention of a second radiologist and geometric distortion measurement on the three remaining MRI scanners.

Comparative studies with EPR and MRI on the in vivo tissue redox status estimation using redox-sensitive nitroxyl probes: influence of the choice of the region of interest

In vivo decay rates of a nitroxyl contrast agent were estimated by a MR redox imaging (MRRI) technique and compared with the decay rates obtained by the electron paramagnetic resonance spectroscopy (EPRS) and imaging (EPRI). MRRI is a dynamic imaging technique employing T1-weighted pulse sequence, which can visualise a nitroxyl-induced enhancement of signal intensity by T1-weighted contrast. EPR techniques can directly measure the paramagnetic nitroxyl radical. Both the squamous cell carcinoma (SCC) tumour-bearing and normal legs of a female C3H mouse were scanned by T1-weighted SPGR sequence at 4.7 T with the nitroxyl radical, carbamoyl-proxyl (CmP), as the contrast agent. Similarly, the time course of CmP in normal muscle and tumour tissues was obtained using a 700-MHz EPR spectrometer with a surface coil. The time course imaging of CmP was also performed by 300 MHz CW EPR imager. EPRS and EPRI gave slower decay rates of CmP compared to the MRRI. Relatively slow decay rate at peripheral region of the tumour tissues, which was found in the image obtained by MRRI, may contribute to the slower decay rates observed by EPRS and/or the EPRI measurements. To reliably determine the tissue redox status from the reduction rates of nitroxyls such as CmP, heterogenic structure in the tumour tissue must be considered. The high spatial and temporal resolution of T1-weighted MRI and the T1-enhancing capabilities of nitroxyls support the use of this method to map tissue redox status which can be a useful biomarker to guide appropriate treatments based on the tumour microenvironment.

Dynamic Contrast-Enhanced Magnetic Resonance Imaging Suggests Normal Perfusion in Normal-Appearing White Matter in Multiple Sclerosis.

Multiple sclerosis (MS) is a chronic, inflammatory disease of the central nervous system and has been associated with reduced perfusion in normal-appearing white matter (NAWM). The magnitude of this hypoperfusion is unclear. The present study aims to quantify NAWM perfusion with dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) in patients with relapsing-remitting (RR) MS and in a control group. The statistical power of a DCE-MRI acquisition to reveal hypoperfusion in MS was estimated using a Monte Carlo simulation: synthetic tissue curves with a contrast-to-noise ratio of 8 were generated for MS patients and control group using perfusion values reported in previous studies. A compartment-uptake model was fitted to these curves, yielding estimates of cerebral blood flow (CBF), cerebral blood volume (CBV), and permeability-surface area product (PS). This was repeated 1000 times. Mean and standard deviation of the resulting distributions were used to calculate the statistical power of a DCE-MRI study to detect perfusion differences between 16 control subjects and 24 MS subjects.In an institutional review board-approved study, patients with RR-MS (n = 24; mean age, 36 years; 17 women, mean Enhanced Disability Status Scale score, 3.25) and patients without history or symptoms of neurological disorder (n = 16; mean age, 49 years; 9 women) underwent a DCE-MRI examination with a previously established MRI protocol (3D SPGR sequence; 2.1 seconds temporal resolution; 44 slices; spatial resolution, 1.7 × 1.7 × 3 mm). Regions were defined manually in the middle cerebral artery; in the frontal, periventricular, and occipital NAWM; in the pons; and in the thalamus, and CBF, CBV, and PS were quantified using a compartment-uptake model.Parameter differences between MS and control groups were evaluated using a mixed linear model with subjects as random effect and controlling for age and sex. A P value of less than 0.05 was considered to indicate statistical significance. For all but one of previously reported effect sizes, the simulation study estimated a statistical power of 80% to 100% to detect reduced CBF in MS. In the patient study, mean (standard deviation) CBF in NAWM was 11.0 (15.1) and 10.4 (8.2) mL/100 mL per minute in the MS and control groups, respectively. Mean CBV in NAWM was 0.50 (0.45) mL/100 mL in the MS group and 0.48 (0.28) mL/100 mL in the control group. Mean values of PS in NAWM were 0.002 mL (0.027)/100 mL per minute in the control group and -0.001 (0.015) mL/100 mL per minute in the MS patients. Differences between patient groups were not statistically significant for CBF, CBV, mean transit time, and PS (P = 0.44, P = 0.20, P = 0.78, P = 0.66, respectively). In both groups, the influence of age on any parameter was nonsignificant. Cerebral blood flow and CBV in the thalamus and pons were significantly higher than in NAWM regions (P < 1e-4); mean transit time was significantly shorter than in NAWM (P < 1e-4). Permeability-surface area product was not significantly different from zero (P > 0.25) in all evaluated regions. Despite high statistical power, we could not confirm previous reports of NAWM hypoperfusion in MS. This indicates that, at least in our patient cohort, potential hypoperfusion is much less pronounced than reported in previous studies.

Magnetic resonance imaging and histology correlation in Cushing's disease

IntroductionWe continuously look for new techniques to improve the radicality of resection and to eliminate the negative effects of surgery. One of the methods that has been implemented in the perioperative management of Cushing's disease was the combination of three magnetic resonance imaging (MRI) sequences: SE, SPGR and fSPGR. Material and methodsWe enrolled 41 patients (11 males, 30 females) diagnosed with Cushing's disease. A 3D tumour model with a navigation console was developed using each SPGR, fSPGR and SE sequence. The largest model was then used. In all cases, a standard four-handed, bi-nostril endoscopic endonasal technique was used. Endocrinological follow-up evaluation using morning cortisol sampling was performed for 6–34 months in our study. ResultsIn total, 36 patients (88%) were disease-free following surgery. Our results indicate we achieved 100% sensitivity of MR. Overall, the conformity of at least one donor site, as compared with the places designated on MR, was in 78% of patients. We searched the place of compliance in individual locations. There is a consensus in individual locations in 63 of the 123 cases (or 56%). The correlation gamma function at a 5% significance level was then 0.27. DiscussionThe combination of MR sequences (SE, SPGR, fSPGR), neuronavigation system and iMRI led to increased sensitivity of up to 100%. Specificity reached 56% in our study. ConclusionWe found a high success rate in surgical procedure in terms of the correlation between MR findings and histology, which leads to remission of Cushing's disease.

Longitudinal study using voxel-based relaxometry: Association between cartilage T1ρ and T2 and patient reported outcome changes in hip osteoarthritis.

To study the local distribution of hip cartilage T1ρ and T2 relaxation times and their association with changes in patient reported outcome measures (PROMs) using a fully automatic, local, and unbiased method in subjects with and without hip osteoarthritis (OA). The 3 Tesla MRI studies of the hip were obtained for 37 healthy controls and 16 subjects with radiographic hip OA. The imaging protocol included a three-dimensional (3D) SPGR sequence and a combined 3D T1ρ and T2 sequence. Quantitative cartilage analysis was compared between a traditional region of interest (ROI)-based method and a fully automatic voxel-based relaxometry (VBR) method. Additionally, VBR was used to assess local T1ρ and T2 differences between subjects with and without OA, and to evaluate the association between T1ρ and T2 and 18-month changes PROMs. Results for the two methods were consistent in the acetabular (R = 0.79; coefficients of variation [CV] = 2.9%) and femoral cartilage (R = 0.90; CV = 2.6%). VBR revealed local patterns of T1ρ and T2 elevation in OA subjects, particularly in the posterosuperior acetabular cartilage (T1ρ : P = 0.02; T2 : P = 0.038). Overall, higher T1ρ and T2 values at baseline, particularly in the anterosuperior acetabular cartilage (T1ρ : Rho = -0.42; P = 0.002; T2 : Rho = -0.44; P = 0.002), were associated with worsening PROMS at 18-month follow-up. VBR is an accurate and robust method for quantitative MRI analysis in hip cartilage. VBR showed the capability to detect local variations in T1ρ and T2 values in subjects with and without osteoarthritis, and voxel based correlations demonstrated a regional dependence between baseline T1ρ and T2 values and changes in PROMs. 1 J. MAGN. RESON. IMAGING 2017;45:1523-1533.

Radial simultaneous multi-slice CAIPI for ungated myocardial perfusion

ObjectiveSimultaneous multi-slice (SMS) imaging is a slice acceleration technique that acquires multiple slices in the same time as a single slice. Radial controlled aliasing in parallel imaging results in higher acceleration (radial CAIPIRINHA or CAIPI) is a promising SMS method with less severe slice aliasing artifacts as compared to its Cartesian counterpart. Here we use radial CAIPI with data undersampling and constrained reconstruction to improve the utility of ungated cardiac perfusion acquisitions. We test the proposed framework with a traditional saturation recovery fast low-angle shot (turboFLASH) sequence and also without saturation recovery as a steady-state spoiled gradient echo (SPGR) sequence on animal and human studies. MethodsSimulations and phantom studies were performed for both the turboFLASH and the SPGR radial CAIPI methods. Ungated undersampled golden ratio radial CAIPI data with saturation recovery were acquired in 8 dogs and 2 human subjects. The CAIPI data without saturation pulses were acquired in 4 human subjects. For both methods, slice acceleration factors of two and three were used. A new spatio-temporal reconstruction using total variation and patch-based low rank constraints was used to jointly reconstruct the multi-slice multi-coil images. ResultsPhantom scans and computer simulations showed that ungated SPGR generally provides better contrast to noise ratio (CNR) than the saturation recovery sequence if the saturation recovery time is less than 100ms. Both of the ungated radial CAIPI methods demonstrated promising image quality in terms of preserving dynamics of the contrast agent and maintaining anatomical structures, even with three slices acquired simultaneously. ConclusionUngated simultaneous multi-slice acquisitions with either a saturation recovery turboFLASH sequence or a steady-state gradient echo SPGR sequence are feasible and provide increased slice coverage without loss of temporal resolution. Compared with a sensitivity encoding (SENSE) SMS reconstruction, the constrained reconstruction method provides better image quality for undersampled radial CAIPI data.

Thalamic segmentation based on improved fuzzy connectedness in structural MRI

Thalamic segmentation serves an important function in localizing targets for deep brain stimulation (DBS). However, thalamic nuclei are still difficult to identify clearly from structural MRI. In this study, an improved algorithm based on the fuzzy connectedness framework was developed. Three-dimensional T1-weighted images in axial orientation were acquired through a 3D SPGR sequence by using a 1.5T GE magnetic resonance scanner. Twenty-five normal images were analyzed using the proposed method, which involved adaptive fuzzy connectedness combined with confidence connectedness (AFCCC). After non-brain tissue removal and contrast enhancement, the seed point was selected manually, and confidence connectedness was used to perform an ROI update automatically. Both image intensity and local gradient were taken as image features in calculating the fuzzy affinity. Moreover, the weight of the features could be automatically adjusted. Thalamus, ventrointermedius (Vim), and subthalamic nucleus were successfully segmented. The results were evaluated with rules, such as similarity degree (SD), union overlap, and false positive. SD of thalamus segmentation reached values higher than 85%. The segmentation results were also compared with those achieved by the region growing and level set methods, respectively. Higher SD of the proposed method, especially in Vim, was achieved. The time cost using AFCCC was low, although it could achieve high accuracy. The proposed method is superior to the traditional fuzzy connectedness framework and involves reduced manual intervention in time saving.

Relevance of 3D magnetic resonance imaging sequences in diagnosing basal subarachnoid neurocysticercosis

Imagenological diagnosis of subarachnoid neurocysticercosis is usually difficult when classical magnetic resonance imaging (MRI) sequences are used. The purpose of this study was to evaluate the advantages of 3D MRI sequences (Fast Imaging Employing Steady-state Acquisition (FIESTA) and Spoiled Gradient Recalled Echo (SPGR)) with respect to classical sequences (Fluid Attenuation Inversion Recovery (FLAIR) and T1) in visualizing Taenia solium cyst in these locations. Forty-seven T. solium cysts located in the basal cisterns of the subarachnoid space were diagnosed in eighteen Mexican patients. A pre-treatment MRI was performed on all patients, and all four sequences (FIESTA, FLAIR, T1 SPGR, and T2) were evaluated independently by two neuroradiologists. The sensitivity of each sequence to detect the parasite membrane and scolex was evaluated, along with its capacity to detect differences in signal intensity between cerebrospinal fluid (CSF) and cysts. FIESTA sequences allowed the visualization of cyst membrane in 87.2% of the parasites evaluated, FLAIR in 38.3%, SPGR in 23.4%, and T2 in 17.0%. The superiority of FIESTA sequences over the other three imaging methods was statistically significant (P<0.001). Scolices were detected by FIESTA twice as much as the other sequences did, although this difference was not significant (P>0.05). Differences in signal intensity between CSF and parasite cysts were significant in FIESTA (P<0.0001), SPGR (P<0.0001), and FLAIR (P=0.005) sequences. For the first time, the usefulness of 3D MRI sequences to diagnose T. solium cysts located in the basal cisterns of the subarachnoid space was demonstrated. The routine use of these sequences could favor an earlier diagnosis and greatly improve the prognosis of patients affected by this severe form of the disease.

TU-F-CAMPUS-J-02: Evaluation of Textural Feature Extraction for Radiotherapy Response Assessment of Early Stage Breast Cancer Patients Using Diffusion Weighted MRI and Dynamic Contrast Enhanced MRI

Purpose: To investigate the feasibility of using classic textural feature extraction in radiotherapy response assessment, we studied a unique cohort of early stage breast cancer patients with paired pre - and post-radiation Diffusion Weighted MRI (DWI-MRI) and Dynamic Contrast Enhanced MRI (DCE-MRI). Methods: 15 female patients from our prospective phase I trial evaluating preoperative radiotherapy were included in this retrospective study. Each patient received a single-fraction radiation treatment, and DWI and DCE scans were conducted before and after the radiotherapy. DWI scans were acquired using a spin-echo EPI sequence with diffusion weighting factors of b = 0 and b = 500 mm2 /s, and the apparent diffusion coefficient (ADC) maps were calculated. DCE-MRI scans were acquired using a T1-weighted 3D SPGR sequence with a temporal resolution of about 1 minute. The contrast agent (CA) was intravenously injected with a 0.1 mmol/kg bodyweight dose at 2 ml/s. Two parameters, volume transfer constant (Ktrans ) and kep were analyzed using the two-compartment Tofts kinetic model. For DCE parametric maps and ADC maps, 33 textural features were generated from the clinical target volume (CTV) in a 3D fashion using the classic gray level co-occurrence matrix (GLCOM) and gray level run length matrix (GLRLM). Wilcoxon signed-rank test was used to determine the significance of each texture feature’s change after the radiotherapy. The significance was set to 0.05 with Bonferroni correction. Results: For ADC maps calculated from DWI-MRI, 24 out of 33 CTV features changed significantly after the radiotherapy. For DCE-MRI pharmacokinetic parameters, all 33 CTV features of Ktrans and 33 features of kep changed significantly. Conclusion: Initial results indicate that those significantly changed classic texture features are sensitive to radiation-induced changes and can be used for assessment of radiotherapy response in breast cancer.

Comparison of T1rho imaging between spoiled gradient echo (SPGR) and balanced steady state free precession (b-FFE) sequence of knee cartilage at 3 T MRI

PurposeTo investigate the difference in T1rho profiles of the entire femoral cartilage between SPGR and b-FFE sequences at 3.0T. Materials and methods20 healthy volunteers were enrolled in this study. T1rho images of each subject were acquired with two types of pulse sequences: SPGR and b-FFE. Femoral cartilage segmentation was performed by two independent raters slice-by-slice using Matlab. Inter- and intra-observer reproducibility between the two imaging protocols was calculated. The relative signal intensity (SI) of cartilage, subchondral bone marrow, joint effusion, and the relative signal contrast between structures of the knee were quantitatively measured. The difference in T1rho values between SPGR and b-FFE sequences was statistically analyzed using the Wilcoxon signed-rank test. ResultsThe average T1rho value of the entire femoral cartilage with b-FFE was significantly higher compared to SPGR (p<0.05). The reproducibility of the segmented area and T1rho values was superior with SPGR compared to b-FFE. The inter-class correlation coefficient was 0.846 on SPGR and 0.824 on b-FFE. The intra-class correlation coefficient of T1rho values was 0.878 on SPGR and 0.836 on b-FFE. The two imaging techniques demonstrated different signal and contrast characteristics. The relative SI of fluid was significantly higher on SPGR, while the relative SI of subchondral bone was significantly higher on b-FFE (p<0.001). There were also significant differences in the relative contrast between fluid–cartilage, fluid–subchondral bone, and cartilage–subchondral bone between the two sequences (all p<0.001). ConclusionWe need to pay attention to differences in T1rho values between SPGR and b-FFE in clinical applications.

Cardiac MRI in patients with cardiac pacemakers: practical methods for reducing susceptibility artifacts and optimizing image quality.

Magnetic resonance imaging (MRI) of pacemaker patients has become available despite of previous contraindications. However, pacing systems containing ferromagnetic material may hamper the diagnostic quality of cardiac MR (CMR) images. To study methods for reducing susceptibility-based artifacts in CMR examinations of pacemaker patients. Altogether 16 patients were scanned with 1.5T MRI scanner using cine balanced steady-state free-precession (bSSFP) and spoiled gradient echo (SPGR) sequences. The use of frequency-scout was also evaluated. For myocardial late gadolinium-enhanced (LGE) imaging, SPGR or bSSFP readout inversion-recovery prepared gradient echo sequences were used with and without phase-sensitive inversion-recovery (PSIR). Two radiologists subjectively compared the image quality (IQ) and the ranges of susceptibility artifacts were evaluated objectively. The IQ proved adequate for diagnosing each patient, although in a few patients with a left-side implanted generator, artifacts hampered IQ in the anterior and anteroseptal segments of the myocardium in bSSFP cine and LGE sequences. In bSSFP cine, the use of frequency-scout could often transfer the banding artifacts away from the left ventricular myocardium. In LGE imaging, the artifacts were more pronounced in IR-bSSFP and PSIR than in IR-SPGR sequences. The ranges of generator-based artifacts were greater in bSSFP (10-12 cm) than in SPGR (6 cm) sequences due to banding artifacts. The artifacts caused by pacemakers typically did not compromise the diagnostic IQ. The use of frequency-scout prior to bSSFP cine or the use of SPGR-based sequences could also improve IQ.

Comparison of doses received by the hippocampus in patients treated with single isocenter– vs multiple isocenter–based stereotactic radiation therapy to the brain for multiple brain metastases

To investigate the doses received by the hippocampus and normal brain tissue during a course of stereotactic radiation therapy using a single isocenter (SI)–based or multiple isocenter (MI)–based treatment planning in patients with less than 4 brain metastases. In total, 10 patients with magnetic resonance imaging (MRI) demonstrating 2-3 brain metastases were included in this retrospective study, and 2 sets of stereotactic intensity-modulated radiation therapy (IMRT) treatment plans (SI vs MI) were generated. The hippocampus was contoured on SPGR sequences, and doses received by the hippocampus and the brain were calculated and compared between the 2 treatment techniques. A total of 23 lesions in 10 patients were evaluated. The median tumor volume, the right hippocampus volume, and the left hippocampus volume were 3.15, 3.24, and 2.63mL, respectively. In comparing the 2 treatment plans, there was no difference in the planning target volume (PTV) coverage except in the tail for the dose-volume histogram (DVH) curve. The only statistically significant dosimetric parameter was the V100. All of the other measured dosimetric parameters including the V95, V99, and D100 were not significantly different between the 2 treatment planning techniques. None of the dosimetric parameters evaluated for the hippocampus revealed any statistically significant difference between the MI and SI plans. The total brain doses were slightly higher in the SI plans, especially in the lower dose region, although this difference was not statistically different. The use of SI-based treatment plan resulted in a 35% reduction in beam-on time. The use of SI treatments for patients with up to 3 brain metastases produces similar PTV coverage and similar normal tissue doses to the hippocampus and the brain when compared with MI plans. SI treatment planning should be considered in patients with multiple brain metastases undergoing stereotactic treatment.