Three-dimensional T1-weighted Gradient Echo Research Articles

Using Machine Learning Methods to Assess Lymphovascular Invasion and Survival in Breast Cancer: Performance of Combining Preoperative Clinical and MRI Characteristics.

Preoperative assessment of lymphovascular invasion (LVI) in invasive breast cancer (IBC) is of high clinical relevance for treatment decision-making and prognosis. To investigate the associations of preoperative clinical and magnetic resonance imaging (MRI) characteristics with LVI and disease-free survival (DFS) by using machine learning methods in patients with IBC. Retrospective. Five hundred and seventy-five women (range: 24-79 years) with IBC who underwent preoperative MRI examinations at two hospitals, divided into the training (N=386) and validation datasets (N=189). Axial fat-suppressed T2-weighted turbo spin-echo sequence and dynamic contrast-enhanced with fat-suppressed T1-weighted three-dimensional gradient echo imaging. MRI characteristics (clinical T stage, breast edema score, MRI axillary lymph node status, multicentricity or multifocality, enhancement pattern, adjacent vessel sign, and increased ipsilateral vascularity) were reviewed independently by three radiologists. Logistic regression (LR), eXtreme Gradient Boosting (XGBoost), k-Nearest Neighbor (KNN), and Support Vector Machine (SVM) algorithms were used to establish the models by combing preoperative clinical and MRI characteristics for assessing LVI status in the training dataset, and the methods were further applied in the validation dataset. The LVI score was calculated using the best-performing of the four models to analyze the association with DFS. Chi-squared tests, variance inflation factors, receiver operating characteristics (ROC), Kaplan-Meier curve, log-rank, Cox regression, and intraclass correlation coefficient were performed. The area under the ROC curve (AUC) and hazard ratios (HR) were calculated. A P-value <0.05 was considered statistically significant. The model established by the XGBoost algorithm had better performance than LR, SVM, and KNN models, achieving an AUC of 0.832 (95% confidence interval [CI]: 0.789, 0.876) in the training dataset and 0.838 (95% CI: 0.775, 0.901) in the validation dataset. The LVI score established by the XGBoost model was an independent indicator of DFS (adjusted HR: 2.66, 95% CI: 1.22-5.80). The XGBoost model based on preoperative clinical and MRI characteristics may help to investigate the LVI status and survival in patients with IBC. 3 TECHNICAL EFFICACY: Stage 2.

Assessment of qualitative and quantitative parameters of healthy thyroid gland in adult horses by magnetic resonance imaging.

In humans and pets, magnetic resonance imaging (MRI) provides important adjunctive anatomic information about the thyroid and its adjacent structures. To the best of our knowledge, however, no studies have been reported regarding the use of MRI for thyroid evaluation in horses. The aim of this study was to obtain qualitative and quantitative parameters of healthy thyroid gland in adult horses by MRI. Eleven horses were submitted to thyroid MRI evaluation. The healthy thyroid of these animals was ensured by normal examinations performed before (free thyroxine and ultrasound) and after (cytology) to MRI. It was concluded that the dorsal spin-echo T1-weighted, fast spin-echo T2-weighted, sagittal STIR and a three-dimensional T1-weighted gradient echo were the sequences that best characterized the thyroid lobes. Qualitatively, there was a significant variation in the elliptical format of some lobes considering the sagittal plane, which oscillated between rounded and flattened conformation. Excellent reproducibility of the quantitative thyroid parameters obtained was verified. The thyroid gland total volume mean of observers was 14.31cm3 (±0.69). In relation with comparisons between quantitative parameters of left and right lobes, only differences regarding their respective lengths were observed. Thus, we can infer that the difference in some thyroid lobes format can be explained by the significant variation identified between left and right lobes lengths.

Motor Sequence Learning Is Associated With Hippocampal Subfield Volume in Humans With Medial Temporal Lobe Epilepsy.

Objectives: Medial temporal lobe epilepsy (mTLE) is characterized by decreased hippocampal volume, which results in motor memory consolidation impairments. However, the extent to which motor memory acquisition are affected in humans with mTLE remains poorly understood. We therefore examined the extent to which learning of a motor tapping sequence task is affected by mTLE.Methods: MRI volumetric analysis was performed using a T1-weighted three-dimensional gradient echo sequence in 15 patients with right mTLE and 15 control subjects. Subjects trained on a motor sequence tapping task with the left hand in right mTLE and non-dominant hand in neurologically-intact controls.Results: The number of correct sequences performed by the mTLE patient group increased after training, albeit to a lesser extent than the control group. Although hippocampal subfield volume was reduced in mTLE relative to controls, no differences were observed in the volumes of other brain areas including thalamus, caudate, putamen and amygdala. Correlations between hippocampal subfield volumes and the change in pre- to post-training performance indicated that the volume of hippocampal subfield CA2–3 was associated with motor sequence learning in patients with mTLE.Significance: These results provide evidence that individuals with mTLE exhibit learning on a motor sequence task. Learning is linked to the volume of hippocampal subfield CA2–3, supporting a role of the hippocampus in motor memory acquisition.Highlights -Humans with mTLE exhibit learning on a motor tapping sequence task but not to the same extent as neurologically-intact controls.-Hippocampal subfield volumes are significantly reduced after mTLE. Surrounding brain area volumes do not show abnormalities.-Hippocampal subfield CA2–3 volume is associated with motor sequence learning in humans with mTLE.

Differentiation of lipid-poor adrenal adenomas from non-adenomas with magnetic resonance imaging: Utility of dynamic, contrast enhancement and single-shot T2-weighted sequences

PurposeTo evaluate the utility of dynamic, contrast-enhanced magnetic resonance imaging (MRI) in combination with single-shot T2-weighted (ssT2) sequences in the differentiation of lipid-poor adrenal adenomas from non-adenomas. Materials and methodsThis retrospective study was approved by the institutional review board and is HIPAA compliant. Between January 2007 and December 2010, 46 patients with MRI demonstrating a lipid-poor adrenal lesion who underwent either surgical resection or a minimum of 24 months of imaging follow-up were identified retrospectively. All images were retrospectively reviewed in blinded fashion by two radiologists. Each adrenal lesion was categorized by dynamic enhancement features and qualitative signal on ssT2 images and was categorized as an adenoma if it demonstrated homogenous enhancement in the arterial phase, washout with capsule enhancement in the delayed phase, and T2 signal isointense to normal adrenal tissue. Any lesion that did not fulfill all the criteria was classified as a non-adenoma. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for characterization of adenoma were calculated for each reader with 95% confidence intervals. A κ test assessed level of agreement between readers. ResultsApplication of our criteria lead to an MRI diagnosis of lipid-poor adrenal adenoma with a sensitivity of 84.2–89.5% (16/19–17/19), specificity of 96.3% (26/27), positive predictive value of 94.1–94.4% (16/17–17/18), negative predictive value of 89.7–92.9% (26/29–26/28), and accuracy of 91.3–93.5% (42/46–43/46). Agreement between the two readers showed substantial κ agreement for the differentiation of adenoma from non-adenoma. ConclusionsDynamic, contrast-enhanced T1-weighted three-dimensional gradient echo sequences in combination with ssT2 images can accurately differentiate lipid-poor adrenal adenomas from non-adenomas.

The Dixon technique and the frequency-selective fat suppression technique in three-dimensional T1 weighted MRI of the liver: a comparison of contrast-to-noise ratios of hepatocellular carcinomas-to-liver.

The use of three-dimensional T1 weighted gradient echo sequences such as the Dixon technique and the frequency-selective fat suppression (FS) technique is currently widely accepted method in MRI examinations of the liver. To assess the image qualities of the Dixon technique and the frequency-selective FS technique, the contrast-to-noise ratios (CNRs) of hepatocellular carcinoma (HCC)-to-liver and fat-to-liver were compared between the two techniques in the hepatobiliary phase (HBP) following administration of gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid. MR images of 59 patients with a total of 86 HCCs were retrospectively evaluated. Images were consecutively obtained with the Dixon and frequency-selective FS methods in the HBP and their CNRs of HCC-to-liver and fat-to-liver were compared. CNRs and contrast ratios were calculated by the mean value of the liver parenchyma, HCC, fat and standard deviation of the liver parenchyma. The Wilcoxon signed-ranks test was used for statistical analysis. The median CNRs for the frequency-selective FS and Dixon techniques of HCC-to-liver were 4.3 and 5.4 (p < 0.01), mesenteric fat-to-liver were 9.9 and 12.8 (p < 0.01) and subcutaneous fat-to-liver were 9.9 and 13.2 (p < 0.01), respectively. The Dixon technique yielded higher CNRs of HCC-to-liver than that of the frequency-selective FS technique. There are a limited number of reports on quantitative analysis of the image qualities of the Dixon technique and the frequency-selective FS technique, particularly within the same patient and examination.

Titanium vs Carbon Coated Ceramic Breast Tissue Marker Clips:: 3T MR Susceptibility Artifact and Local Signal Disturbance

Spectroscopy signal of a breast lesion may be disrupted by the presence of metal from a biopsy marking clip. This study compares the size of magnetic resonance (MR) susceptibility artifacts and degree of local spectroscopy signal disturbance created by conventional titanium tissue marker clips to that of a novel carbon coated ceramic breast tissue marker clip. Five breast tissue marker clips were embedded in a gelatin breast phantom. The phantoms were imaged on a 3T MR scanner, and three-dimensional T1-weighted gradient echo images were obtained. The area of the susceptibility artifact was calculated and compared for each clip. Single voxel point resolved spectroscopy spectra (SVS) were acquired for three ceramic clips aligned along the superoinferior, anteroposterior, and left-right axes, respectively. Measurements were repeated for an area of pure gelatin and for one similarly sized titanium clip located arbitrarily in the main field. Water spectra were obtained, and line widths and areas of the water peaks were compared. All five clips were easily visible on MR imaging. The ceramic marker clip produced less apparent artifact when compared with the metallic clips. Spectral analysis demonstrated local frequency shifts around all clips. Line widths varied from 7 to 92 Hz in the voxels on and around the titanium clip and from 4 to 18 Hz around the ceramic clips. The ceramic breast tissue marker clip produced less susceptibility artifact and less line broadening on 3T MR imaging than conventional titanium clips. This tissue marker may reduce artifact and improve consistency of breast MR spectroscopy.

Hippocampal atrophy rates in Alzheimer disease

To investigate the added value of hippocampal atrophy rates over whole brain volume measurements on MRI in patients with Alzheimer disease (AD), patients with mild cognitive impairment (MCI), and controls. We included 64 patients with AD (67 +/- 9 years; F/M 38/26), 44 patients with MCI (71 +/- 6 years; 21/23), and 34 controls (67 +/- 9 years; 16/18). Two MR scans were performed (scan interval: 1.8 +/- 0.7 years; 1.0 T), using a coronal three-dimensional T1-weighted gradient echo sequence. At follow-up, 3 controls and 23 patients with MCI had progressed to AD. Hippocampi were manually delineated at baseline. Hippocampal atrophy rates were calculated using regional, nonlinear fluid registration. Whole brain baseline volumes and atrophy rates were determined using automated segmentation and registration tools. All MRI measures differed between groups (p < 0.005). For the distinction of MCI from controls, larger effect sizes of hippocampal measures were found compared to whole brain measures. Between MCI and AD, only whole brain atrophy rate differed significantly. Cox proportional hazards models (variables dichotomized by median) showed that within all patients without dementia, hippocampal baseline volume (hazard ratio [HR]: 5.7 [95% confidence interval: 1.5-22.2]), hippocampal atrophy rate (5.2 [1.9-14.3]), and whole brain atrophy rate (2.8 [1.1-7.2]) independently predicted progression to AD; the combination of low hippocampal volume and high atrophy rate yielded a HR of 61.1 (6.1-606.8). Within patients with MCI, only hippocampal baseline volume and atrophy rate predicted progression. Hippocampal measures, especially hippocampal atrophy rate, best discriminate mild cognitive impairment (MCI) from controls. Whole brain atrophy rate discriminates Alzheimer disease (AD) from MCI. Regional measures of hippocampal atrophy are the strongest predictors of progression to AD.

Detection of small pulmonary nodules in high-field MR at 3 T: evaluation of different pulse sequences using porcine lung explants

To evaluate two MR imaging sequences for the detection of artificial pulmonary nodules inside porcine lung explants. 67 agarose nodules ranging 3-20 mm were injected into ten porcine lungs within a dedicated chest phantom. The signal on T1-weighted images and radiopacity were adjusted by adding 0.125 mmol/l Gd-DTPA and 1.5 g/l of iodine. A T1-weighted three-dimensional gradient-echo (T1-3D-GRE; TR/TE:3.3/1.1 ms, slice:8 mm, flip-angle:10 degrees ) and a T2-weighted half-Fourier fast-spin echo sequence (T2-HF-FSE; TR/TE:2000/66 ms, slice:7 mm, flip-angle:90 degrees ) were applied in axial orientation using a 3-T system (Intera, Philips Medical Systems, Best, The Netherlands), followed by CT (16x0.5 mm) as reference. Nodule sizes and locations were assessed by three blinded observers. In nodules of >10 mm, sensitivity was 100% using 3D-GRE-MRI and 94% using the HF-FSE sequence. For nodules 6-10 mm, the sensitivity of MRI was lower than with CT (3D-GRE:92%; T2-HF-FSE:83%). In lesions smaller than 5 mm, the sensitivity declined to 80% (3D-GRE) and 53% (HF-FSE). Small lesion diameters were overestimated with both sequences, particularly with HF-FSE. This study confirms the feasibility of 3 T-MRI for lung nodule detection. In lesions greater than 5 mm, the sensitivity of the 3D-GRE sequence approximated CT (>90%), while sensitivity and PPV with the HF-FSE sequence were slightly inferior.

MRI assessment of knee osteoarthritis: Knee Osteoarthritis Scoring System (KOSS)--inter-observer and intra-observer reproducibility of a compartment-based scoring system.

To develop a scoring system for quantifying osteoarthritic changes of the knee as identified by magnetic resonance (MR) imaging, and to determine its inter- and intra-observer reproducibility, in order to monitor medical therapy in research studies. Two independent observers evaluated 25 consecutive MR examinations of the knee in patients with previously defined clinical symptoms and radiological signs of osteoarthritis. We acquired on a 1.5 T system: coronal and sagittal proton density- and T2-weighted dual spin echo (SE) images, sagittal three-dimensional T1-weighted gradient echo (GE) images with fat suppression, and axial dual turbo SE images with fat suppression. Images were scored for the presence of cartilaginous lesions, osteophytes, subchondral cysts, bone marrow edema, and for meniscal abnormalities. Presence and size of effusion, synovitis and Baker's cyst were recorded. All parameters were ranked on a previously defined, semiquantitative scale, reflecting increasing severity of findings. Kappa, weighted kappa and intraclass correlation coefficient (ICC) were used to determine inter- and intra-observer variability. Inter-observer reproducibility was good (ICC value 0.77). Inter- and intra-observer reproducibility for individual parameters was good to very good (inter-observer ICC value 0.63-0.91; intra-observer ICC value 0.76-0.96). The presented comprehensive MR scoring system for osteoarthritic changes of the knee has a good to very good inter-observer and intra-observer reproducibility. Thus the score form with its definitions can be used for standardized assessment of osteoarthritic changes to monitor medical therapy in research studies.

Sequential 3-D MRI frontal volume changes in subacute sclerosing panencephalitis

In patients with subacute sclerosing panencephalitis, clinical stages defined according to Jabbour correlate strongly with frontal lobe dysfunctions. Nonquantitative radiologic investigations in these patients have confirmed cerebral atrophy without identifying predominantly affected regions. We addressed this issue over an 8-year-old boy's course using volumetry based on three-dimensional T1-weighted gradient echo magnetic resonance imaging. Seven normal 6–12-year-old subjects served as controls. Whole-brain volume declined as Jabbour stage advanced from I to III. Frontal lobe volume and frontal-to-whole-brain volume ratios fell significantly as clinical stage progressed. Thus, cerebral atrophy in this SSPE patient was predominantly frontal, and paralleled clinical progression.

Effect of apolipoprotein E genotype on hippocampal volume loss in aging healthy women.

To determine whether the presence of a single epsilon4 allele of the APOE gene is associated with an increased rate of hippocampal volume loss or decline in cognition in healthy women in their sixth decade of life. Nine APOE-epsilon4 allele-negative (mean age +/- SD, 60.6 +/- 10.2 years) and 16 APOE-epsilon4 allele-positive (mean age +/- SD, 55.1 +/- 6.0 years) healthy women underwent neurocognitive testing and MRI at the time of entry into the study (baseline) and 2 years later. Neurocognitive testing consisted of the Buschke-Fuld Free Recall, verbal fluency tests, the Rey Figure Test, the Wechsler Memory Scale-Revised, and the Wechsler Adult Intelligence Survey-Revised Block Design. Hippocampal volume determinations were based on manual outlining of sagittal slices aided by axial, coronal, and three-dimensional views of high-resolution 124-slice whole-brain scans; the scans were obtained with a 1.5-tesla scanner using a T1-weighted three-dimensional gradient echo sequence with RF spoiling (TR/TE/flip angle, 24 msec/3 msec/30 degrees ). The percent change in hippocampal volume per year was greater in the APOE-epsilon4 allele-positive group (mean +/- SD, 2.32 +/- 1.75%) than in the APOE-epsilon4 allele-negative group (mean +/- SD, 0.77 +/- 1.02%; t = 2.41; p < 0.03, two-tailed test). There were no significant differences between the two groups in terms of any of the cognitive measures, and hippocampal volume loss was not correlated with changes in any of the above-mentioned cognitive measures. The presence of a single APOE-epsilon4 allele is associated with an increased rate of hippocampal volume loss in healthy women in their sixth decade of life that is not related to any detectable memory changes.

Entorhinal cortex atrophy in epilepsy patients exhibiting normal hippocampal volumes.

To determine whether MRI volumetric measurement of the entorhinal cortex could detect structural damage and lateralize the seizure focus in patients with temporal lobe epilepsy in whom no measurable hippocampal abnormalities were found. A reduction in the volume of the entorhinal cortex ipsilateral to the seizure focus in patients with intractable temporal lobe epilepsy and hippocampal atrophy was recently shown. MRI volumetric analysis of the entorhinal cortex was performed using a T1-weighted three-dimensional gradient echo sequence in 24 control subjects and 22 patients with temporal lobe epilepsy and normal hippocampal volumes. Thirteen patients underwent surgery, with a mean postoperative follow-up of 36 months. Group analysis (multivariate analysis of variance) showed a reduction in the volume of the entorhinal cortex ipsilateral to the seizure focus in patients with left (p < 0.0001) and right temporal lobe epilepsy (p < 0.0001). Lateralization of the seizure focus could be done in 14 of 22 patients (64%) based on entorhinal cortex volumetry. Entorhinal cortex atrophy ipsilateral to the seizure focus supports the presence of structural damage in the mesial temporal lobe in patients with temporal lobe epilepsy and normal hippocampal volumes and emphasizes the participation of the entorhinal cortex in the pathogenesis of this disorder.

Transnasal and transsphenoidal MRI-guided biopsies of petroclival tumors.

Magnetic resonance imaging (MRI) allows excellent tissue characterization in the area of the petroclival region and can depict lesions not visualized with ultrasound or computed tomography (CT). The aim of this study was to demonstrate the clinical feasibility and utility of an interactive MR-guidance system to target and biopsy tumors in the petroclival region. MRI-guided biopsies of 10 patients with tumors in the clivus and petrous apex were performed in an open 0.5-T MR system. Lesions were targeted through a transsphenoidal or transnasal approach. Imaging during biopsies was achieved by a combination of standard and interactive mode. T1-weighted spin-echo, T2-weighted fast spin-echo (FSE), and three-dimensional T1-weighted gradient-echo (GRE) scans (standard mode) were selected to provide optimal tissue characterization for both the lesion and surrounding structures and varied according to the anatomic site. For interactive imaging, T1-weighted GRE and T2-weighted FSE sequences were used. We performed MRI-guided transsphenoidal biopsies in 10 patients who had lesions identified by CT (n = 5) and/or MRI (n = 10). The indications for biopsies were to differentiate between suspected malignant processes (n = 4 ) and benign processes (n = 6). Lesions adjacent to structures like the internal carotid artery were accurately targeted in particular. All biopsies were performed successfully and were the basis for selection of further treatment. No complications occurred during the procedures. An open MR system allows interactive control of biopsies in the area of the petroclival region, providing maximum patient safety and diagnostic accuracy not possible in other systems. The advantages of MRI tissue characterization are combined with an interactive, one-step method of localization and targeting, as well as tissue sampling. J. Magn. Reson. Imaging 2001;13:3-11.

Optimization of three-dimensional T1-weighted gradient-echo imaging of the cervical spine.

Various parameters of the three-dimensional (3D) T1-weighted magnetization-prepared rapid acquisition gradient-echo (MP-RAGE) sequence were evaluated to improve spatial resolution while maintaining T1 contrast and a short examination time in imaging of the cervical spine in volunteers. The most dramatic improvements in image resolution occurred by decreasing section thickness to 1.2 mm and increasing the in-plane matrix to 192 x 256, with a 230-mm field of view. The increase in imaging time due to the increased matrix was offset by the elimination of the preparation pulse and wait time, without dramatic changes in contrast-to-noise ratio or overall image quality. Optimum parameters included elimination of the preparation pulse and wait time, 12 degrees flip angle, 192 x 256 matrix, 1.2-mm section thickness, nonselective excitation (coronal acquisition), RF spoiling, and standard k-space ordering, for an examination time of 5 minutes 21 seconds.