Isotropic three-dimensional T2 mapping of knee cartilage: Development and validation.

Stereotactic MR-guided Adaptive Radiation Therapy (SMART) dose painting for hypoxia has potential to improve treatment outcomes, but clinical implementation on low-field MR-Linac faces substantial challenges due to dramatically lower signal-to-noise ratio (SNR) characteristics. While quantitative MRI and T1 mapping of hypoxia biomarkers show promise, T1-to-noise ratio (T1NR) optimization at low fields is paramount, particularly for the clinical implementation of oxygen-enhanced (OE)-MRI. The 3D Magnetization Prepared (2) Rapid Gradient Echo (MP2RAGE) sequence stands out for its ability to acquire homogeneous T1-weighted contrast images with simultaneous T1 mapping. To optimize MP2RAGE for low-field T1 mapping; conduct experimental validation in a ground-truth phantom; establish feasibility and reproducibility of low-field MP2RAGE acquisition and T1 mapping in healthy volunteers. The MP2RAGE optimization was performed to maximize the contrast-to-noise ratio (CNR) of T1 values in white matter (WM) and gray matter (GM) brain tissues at 0.35T. Low-field MP2RAGE images were acquired on a 0.35T MR-Linac (ViewRay MRIdian) using a multi-channel head coil. Validation of T1 mapping was performed with a ground-truth Eurospin phantom, containing inserts of known T1 values (400-850ms), with one and two average (1A and 2A) MP2RAGE scans across four acquisition sessions, resulting in eight T1 maps. Mean (±SD) T1 relative error, T1NR, and intersession coefficient of variation (CV) were determined. Whole-brain MP2RAGE scans were acquired in 5 healthy volunteers across two sessions (A and B) and T1 maps were generated. Mean (±SD) T1 values for WM and GM were determined. Whole-brain T1 histogram analysis was performed, and reproducibility was determined with the CV between sessions. Voxel-by-voxel T1 difference maps were generated to evaluate 3D spatial variation. Low-field MP2RAGE optimization resulted in parameters: MP2RAGETR of 3250ms, inversion times (TI1/TI2) of 500/1200ms, and flip angles (α1/α2) of 7/5°. Eurospin T1 maps exhibited a mean (±SD) relative error of 3.45%±1.30%, T1NR of 20.13±5.31, and CV of 2.22%±0.67% across all inserts. Whole-brain MP2RAGE images showed high anatomical quality with clear tissue differentiation, resulting in mean (±SD) T1 values: 435.36±10.01ms for WM and 623.29±14.64ms for GM across subjects, showing excellent concordance with literature. Whole-brain T1 histograms showed high intrapatient and intersession reproducibility with characteristic intensity peaks consistent with voxel-level WM and GM T1 values. Reproducibility analysis revealed a CV of 0.46%±0.31% and 0.35%±0.18% for WM and GM, respectively. Voxel-by-voxel T1 difference maps show a normal 3D spatial distribution of noise in WM and GM. Low-field MP2RAGE proved effective in generating accurate, reliable, and reproducible T1 maps with high T1NR in phantom studies and in vivo feasibility established in healthy volunteers. While current work is focused on refining the MP2RAGE protocol to enable clinically efficient OE-MRI, this study establishes a foundation for TOLD T1 mapping for hypoxia biomarkers. This advancement holds the potential to facilitate a paradigm shift toward MR-guided biological adaptation and dose painting by leveraging 3D hypoxic spatial distributions and improving outcomes in conventionally challenging-to-treat cancers.

Objective: To investigate the value of T2 map and synthetic T2WI generated by T2 mapping in evaluating the histological type, pathological classification and depth of myometrial invasion of endometrial carcinoma (EC). Methods: Seventy-three patients with pathologically proven EC diagnosed at the First Affiliated Hospital of Zhengzhou University from December 2019 to December 2021 and 42 healthy volunteers were enrolled in the study. All subjects underwent conventional MRI, diffusion weighted imaging (DWI) and T2 mapping sequence for the pelvic cavity to test the T2 values and the apparent diffusion coefficient (ADC) of the focus nidus of the patients and the normal endometrium of the volunteers. The T2 and ADC values of EC vs normal endometrium, and those of different histological types and pathological grades were compared. The receiver operating characteristic (ROC) curves were constructed to evaluate the diagnostic performance of T2 and ADC values in determining the pathological type and classification of EC. In addition, two radiologists used synthetic T2WI combined with T2 map and conventional T2WI combined with DWI, respectively, to evaluate the depth of myometrial invasion, and compared the imaging results with the results of pathological diagnosis to evaluate the diagnostic efficacy of the two methods in determining the depth of myometrial invasion. Results: The T2 and ADC values of endometrial carcinoma were 85.0 (80.8, 92.5) ms and 0.71 (0.64, 0.77) ×10(-3) mm(2)/s, respectively, which were significantly lower than those of normal endometrium [147.4 (123.4, 176.7) ms and 1.46 (1.26, 1.76)×10(-3) mm(2)/s, respectively; both P<0.05]. The T2 values of endometrioid carcinoma (EA) [84.1 (79.5, 88.7) ms] were significantly lower than those of non-EA [98.8 (92.1, 102.8) ms; P<0.05]. There was no significant difference in ADC values between EA and non-EA (P=0.075). The T2 values of G1, G2 and G3 groups in EA were 89.1 (84.4, 94.4) ms, 83.6 (80.9, 86.2) ms, and 76.5 (71.4, 80.3) ms, respectively. There were significant differences in the T2 values between G1 vs G2, G1 vs G3, and G2 vs G3 groups, respectively (all P<0.017). Significant difference was also found in the ADC values between the G1 and G3 groups (P<0.017). The area under the ROC curve (AUC) of T2 values in distinguishing EA from non-EA was 0.867. The AUC of T2 values, ADC values and their combination in predicting high-grade EA was 0.888, 0.730 and 0.895, respectively. The accuracy of synthetic T2WI+ T2 map and conventional T2WI+ DWI in the diagnosis of deep myometrial invasion was 78.1% and 79.5%, respectively, with no significant difference (P>0.05). Conclusions: T2 mapping has great potential in preoperative evaluation of EC. The quantitative T2 value can be used in the diagnosis, pathological classification and grading of EC. The combination of synthetic T2WI and T2 map may be helpful to determine the depth of myometrial invasion.

To study the interrelationship between patella cartilage T2 relaxation time, other knee abnormalities, and physical activity levels in asymptomatic subjects from the Osteoarthritis Initiative (OAI) incidence cohort. The study had institutional review board approval and was HIPAA compliant. One hundred twenty subjects from the OAI without knee pain (age, 45-55 years) and with risk factors for knee osteoarthritis (OA) were studied by using knee radiographs, 3.0-T knee magnetic resonance (MR) images (including intermediate-weighted fast spin-echo and T2 mapping sequences), and the Physical Activity Scale for the Elderly. MR images of the right knee were assessed by two musculoskeletal radiologists for the presence and grade of abnormalities. Segmentation of the patella cartilage was performed, and T2 maps were generated. Statistical significance was determined by using analysis of variance, chi(2) analysis, correlation coefficient tests, the Cohen kappa, and a multiple linear regression model. Cartilage lesions were found in 95 (79.0%) of 120 knees, and meniscal lesions were found in 54 (45%) of 120 knees. A significant correlation between patella cartilage T2 values and the severity and grade of cartilage (P = .0025) and meniscus (P = .0067) lesions was demonstrated. Subjects with high activity levels had significantly higher prevalence and grade of abnormalities and higher T2 values (48.7 msec +/-4.35 vs 45.8 msec +/-3.93; P < .001) than did subjects with low activity levels. Middle-aged asymptomatic individuals with risk factors for knee OA had a high prevalence of cartilage and meniscus knee lesions. Physically active individuals had more knee abnormalities and higher patellar T2 values. Additional studies will be needed to determine causality.

Cardiovascular magnetic resonance (CMR) has been studied as an alternative to endomyocardial biopsy (EMB) in orthotopic heart transplant recipients (OHTRs), particularly through breath-hold myocardial T1 and T2 mapping sequences. We aimed to assess the diagnostic performance of the novel free-breathing multiparametric saturation-recovery single-shot acquisition (mSASHA) mapping technique to identify acute cardiac allograft rejection (ACAR) non-invasively against EMB. This retrospective study included n = 21 consecutive OHTRs with suspected ACAR who underwent both a 1.5T CMR scan with mSASHA mapping and an EMB within 5.4 (1.2-14.8) days, and n = 20 healthy controls who underwent CMR with mSASHA mapping. Conventional breath-holding T2-prepared balanced steady-state free precession (T2p-bSSFP) T2 mapping was also acquired. CAR was EMB defined as histological rejection (HR) (acute cellular rejection of ≥ 1 R or acute antibody-mediated rejection of ≥ 1). Overall, n = 21 OHTRs (9 females) with a mean age of 43.2 ± 16.2 years and a median time of 5.4 (1.2-14.8) years since transplantation were included in the study, alongside n = 20 healthy controls. HR was present in n = 9 patients. The HR group showed significantly higher septal mSASHA T2 values compared to the non-HR (n = 12) group (53 ± 6 ms vs. 47 ± 4 ms, p = 0.014). Receiver operator characteristics analysis showed an area under the curve of 0.79 (95% confidence interval 0.59-0.98, p = 0.028) and an optimal cut-off value of 50 ms (sensitivity of 67%, specificity of 75%) for identifying patients with HR using septal mSASHA T2 values. There was at least a moderate correlation of septal and global mSASHA T1 and T2 values (n = 21) with MOLLI T1 (n = 17) and T2p-bSSFP T2 (n = 18) values (r > 0.6, p ≤ 0.003). OHTR patients without HR showed higher septal (T1: 1256 ± 42 ms vs. 1201 ± 46 ms, p = 0.002; T2: 47 ± 4 ms vs. 43 ± 2 ms, p = 0.003) and global mSASHA (T1: 1250 ± 58 ms vs. 1201 ± 45 ms, p = 0.013; T2: 48 ± 5 ms vs. 43 ± 2 ms, p = 0.009) values compared to normal controls (n = 20). In the control group, native mSASHA T1 and T2 values were higher in females (n = 9) than in males. Free-breathing mSASHA T2 mapping may be useful in identifying histological changes associated with ACAR, overcoming the challenges of breath holding and with good diagnostic performance.

The reliability and diagnostic performance of deep learning (DL)-based automated T2 measurements on T2 map of 3.0-T cardiac magnetic resonance imaging (MRI) using multi-institutional datasets have not been investigated. We aimed to evaluate the performance of a DL-based software for measuring automated T2 values from 3.0-T cardiac MRI obtained at two centers. Eighty-three subjects were retrospectively enrolled from two centers (42 healthy subjects and 41 patients with myocarditis) to validate a commercial DL-based software that was trained to segment the left ventricular myocardium and measure T2 values on T2 mapping sequences. Manual reference T2 values by two experienced radiologists and those calculated by the DL-based software were obtained. The segmentation performance of the DL-based software and the non-inferiority of automated T2 values were assessed compared with the manual reference standard per segment level. The software's performance in detecting elevated T2 values was assessed by calculating the sensitivity, specificity, and accuracy per segment. The average Dice similarity coefficient for segmentation of myocardium on T2 maps was 0.844. The automated T2 values were non-inferior to the manual reference T2 values on a per-segment analysis (45.35 vs. 44.32 ms). The DL-based software exhibited good performance (sensitivity: 83.6-92.8%; specificity: 82.5-92.0%; accuracy: 82.7-92.2%) in detecting elevated T2 values. The DL-based software for automated T2 map analysis yields non-inferior measurements at the per-segment level and good performance for detecting myocardial segments with elevated T2 values compared with manual analysis.

Myocardial T1 mapping is a useful technique for the diagnosis of diffuse fibrosis. Although modified look-locker inversion recovery is a widely used T1 mapping method, variation in T1 values has been reported. Non-uniform T1 maps may hinder differentiation between healthy and diseased myocardial tissue. The purpose of this study was to investigate the uniformity of T1 mapping using polarity corrected inversion time preparation (PC TI prep) in a myocardial phantom and healthy volunteers. The myocardial phantom was scanned between polyvinyl alcohol (PVA) and air. T1 values were measured using inversion recovery fast spin-echo (IR-FSE) and PC TI prep in areas adjacent to PVA and air. For the volunteer study, the short-axis plane was imaged using the PC TI prep to compare T1 values in the myocardium of the septal and lateral walls. The T1 value of the phantom using the IR-FSE was not significantly different in the area between PVA and air, whereas the T1 value using the PC TI prep in the air area was significantly lower than that in the PVA area. T1 mapping of the healthy myocardium exhibited no significant difference between the septal and lateral walls. The T1 value using the PC TI prep in the air area was 6.3% lower than that using IR-FSE. In this study, T1 mapping using the PC TI prep exhibited high uniformity of T1 values.

To evaluate differences in T2 values in femoral and tibial cartilage at magnetic resonance (MR) imaging in patients with varying degrees of osteoarthritis (OA) compared with healthy subjects and to develop a mapping and display method based on calculation of T2 z scores for visual grading and assessment of cartilage heterogeneity in patients with OA. Knee cartilage was evaluated in 55 subjects who were categorized with radiography as healthy (n = 7) or as having mild OA (n = 20) or severe OA (n = 28). Cartilage regions were determined with manual segmentation of an MR image acquired with spoiled gradients and fat suppression. The segmentation was applied to a map of T2 relaxation time and was analyzed in four knee cartilage compartments (ie, the medial and lateral tibia and femur). Differences between cartilage compartment T2 values and subject groups were analyzed with analysis of covariance. Correlations of cartilage T2 values with clinically reported symptoms and cartilage thickness and volume were examined. Cartilage T2 values were converted to z scores per voxel on the basis of normal population values in the same cartilage compartment to better interpret cartilage heterogeneity and variation from normal. Healthy subjects had mean T2 values of 32.1-35.0 msec, while patients with mild and severe OA had mean T2 values of 34.4-41.0 msec. All cartilage compartments except the lateral tibia showed significant (P <.05) increases in T2 relaxation time between healthy and diseased knees; however, no significant difference was found between patients with mild and severe OA. Correlation of T2 values with clinical symptoms and cartilage morphology was found predominantly in medial compartments. Femoral and medial tibial cartilage T2 values increase with the severity of OA.

To develop a heart-rate independent breath-held joint T1 -T2 mapping sequence for accurate simultaneous estimation of coregistered myocardial T1 and T2 maps. A novel preparation scheme combining both a saturation pulse and T2 -preparation in a single R-R interval is introduced. The time between these two pulses, as well as the duration of the T2 -preparation is varied in each heartbeat, acquiring images with different T1 and T2 weightings, and no magnetization dependence on previous images. Inherently coregistered T1 and T2 maps are calculated from these images. Phantom imaging is performed to compare the proposed maps with spin echo references. In vivo imaging is performed in ten subjects, comparing the accuracy and precision of the proposed technique to existing myocardial T1 and T2 mapping sequences of the same duration. Phantom experiments show that the proposed technique provides accurate quantification of T1 and T2 values over a wide-range (T1 : 260 ms to 1460 ms, T2 : 40 ms to 200 ms). In vivo imaging shows that the proposed sequence quantifies T1 and T2 values similar to a saturation-based T1 mapping and a conventional breath-hold T2 mapping sequence, respectively. The proposed sequence allows joint estimation of accurate and coregistered quantitative myocardial T1 and T2 maps in a single breath-hold. Magn Reson Med 76:888-896, 2016. © 2015 Wiley Periodicals, Inc.

Quantitative magnetic resonance imaging has been successfully applied to assess the status of cartilage biochemical components. This study aimed to investigate the performance of 3.0T magnetic resonance imaging T2 mapping combined with texture analysis for evaluating the early degeneration of lumbar facet joints. A total of 38 patients (20 in the asymptomatic group and 18 in the symptomatic group) were enrolled. All patients underwent 3.0T magnetic resonance imaging conventional sequences, water excitation three-dimensional spoiled gradient echo sequence (3D-WATSc), and T2 mapping scans. The bilateral L4/5 and L5/S1 lumbar facet joints were morphological graded using the Weishaupt criteria, T2 values, and texture parameters derived from T2 mapping of cartilage. The Kruskal-Wallis H test was used to compare the differences of parameters among different groups. Multivariate logistic regression analysis was used to obtain the independent predictive factors for evaluating the early degeneration of lumbar facet joints. Receiver operating characteristic (ROC) curve was performed and the area under curve (AUC) was calculated. Spearman correlation analysis was used to evaluate the correlation of the independent predictors of cartilage T2 value and texture parameters with the subjects' Japanese Orthopedic Association (JOA) score or Visual Analogue Scale (VAS) score. A total of 148 facet joints were selected, including 70 in Weishaupt 0 (normal) group, 58 in Weishaupt 1 group, and 20 in Weishaupt 2-3 group. T2 value, entropy, and contrast increased significantly as the exacerbation of facet joint degeneration (all P<0.05), while the inverse difference moment, energy, and correlation decreased (all P<0.05). Entropy among different groups was significantly different (all P<0.05), and the differences of T2 value, contrast, inverse difference moment, and energy between Weishaupt 0 and Weishaupt 1 groups, or Weishaupt 0 and Weishaupt 2-3 groups were statistically significant (all P<0.05). Multivariate logistic regression analysis suggested that T2 value and inverse difference moment were the independent predictors for evaluating early degeneration of facet joints. The combination of T2 value with inverse difference moment achieved the best performance in distinguishing Weishaupt 0 from Weishaupt 1 (AUC=0.85), with sensitivity and specificity at 92.7% and 76.5%, respectively. In the symptom group, the cartilage T2 value combined inverse difference moment was positively correlated with JOA score (r=0.475, P<0.05) and VAS score (r=0.452, P<0.05). 3.0T magnetic resonance imaging T2 mapping combined with texture analysis is helpful to quantitatively evaluate the early degeneration of lumbar facet joints, in which the T2 value and inverse difference moment show an indicative significance．.

The goal of this work is to extend prior work on cardiac MR Fingerprinting (cMRF) using rosette k-space trajectories to enable simultaneous T1, T2, and proton density fat fraction (PDFF) mapping in the heart. A rosette trajectory designed for water-fat separation at 1.5T was used in a 2D ECG-triggered 15-heartbeat cMRF sequence. Water and fat specific T1 and T2 maps were generated from the cMRF data. A PDFF map was also retrieved using Hierarchical IDEAL by segmenting the rosette cMRF data into multiple echoes. The accuracy of rosette cMRF in T1, T2, and PDFF quantification was validated in the ISMRM/NIST phantom and an in-house built fat fraction phantom, respectively. The proposed method was also applied for myocardial tissue mapping of healthy subjects and cardiac patients at 1.5T. T1, T2, and PDFF values measured using rosette cMRF in the ISMRM/NIST phantom and the fat fraction phantom agreed well with the reference values. In 16 healthy subjects, rosette cMRF yielded T1 values which were 80~90 ms higher than spiral cMRF and MOLLI. T2 values obtained using rosette cMRF were ~3 ms higher than spiral cMRF and ~5 ms lower than conventional T2-prep bSSFP method. Rosette cMRF was also able to detect abnormal T1 and T2 values in cardiomyopathy patients and may provide more accurate maps due to effective fat suppression. In conclusion, this study shows that rosette cMRF has the potential for efficient cardiac tissue characterization through simultaneous quantification of myocardial T1, T2, and PDFF.

Myocardial involvement may occur during systemic sclerosis (SSc) and can lead to impaired myocardial contraction and/or arrhythmia. Cardiac magnetic resonance imaging (MRI) is used for noninvasive characterization of the myocardium. The aim of this study was to evaluate the utility of cardiac MRI with intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) and longitudinal relaxation time (T1) sequence mapping for assessment of myocardial microvascular and interstitium impairment in SSc. In this single-center prospective cohort study, 40 consecutive patients with SSc and 20 healthy controls were assessed by cardiac MRI with IVIM DWI and T1 mapping sequences on a 3T scanning system. Images were analyzed independently by 2 assessors, and Bland-Altman plots were used to assess interreader concordance and reproducibility. Characteristics of the patients were compared according to quartiles of T1 and perfusion fraction (f-coefficient) values, using exact Cochran-Ermitage trend tests for qualitative variables and analysis of variance for quantitative variables. Kaplan-Meier cardiac events-free survival curves were plotted and compared with a log-rank test for trend. T1 values were higher in SSc patients than in healthy controls, and were higher in the diffuse cutaneous SSc (dcSSc) subset (P=0.02). Higher T1 values were associated with the immunologic pattern seen in patients with the dcSSc form (P=0.0001), a higher modified Rodnan skin thickness score (MRSS) (P=0.003), and a higher frequency of interstitial lung disease (P=0.03). Moreover, higher T1 values were correlated with higher MRSS scores (r=+0.32, P=0.04) and reduced forced vital capacity (r=-0.34, P=0.048), and tended to be correlated with reduced total lung capacity (r=-0.30, P=0.07). Lower f-coefficient values, as a measure of decreased tissue perfusion, were associated with less frequent use of vasodilators (P=0.02 for angiotensin-converting enzyme inhibitors and P=0.06 for calcium-channel blockers) and more frequent use of glucocorticoids (P=0.02). The f-coefficients were inversely correlated with the T1 values (r=-0.31, P=0.02). Furthermore, higher T1 values were associated with higher incidence of cardiac events (log-rank test for trend P=0.03). Increased T1 values, potentially suggesting microscopic fibrosis, were observed more frequently in patients with dcSSc, and higher T1 values were associated with interstitial lung disease and more frequent cardiac events during follow-up. The results of this study show that cardiac MRI with T1 mappingsequences and IVIM DWI may be useful in assessing myocardial involvement in patients with SSc.

To determine whether T2 mapping in liver MRI can predict decompensation and death in cirrhotic patients. This retrospective study included 292 cirrhotic patients who underwent gadoxetic acid-enhanced MRI, including T1 and T2 mapping at 10-min hepatobiliary phase by using the Look-Locker and radial turbo spin-echo sequences, respectively. T1 and T2 values of the liver and spleen were measured. The association of MR parameters and serum markers with decompensation and death was investigated. Risk models combining T2Liver, serum albumin level, and Model for End-Stage Liver Disease (MELD) score were created for predicting decompensation (T2Liver, < 49.3 versus ≥ 49.3 ms) and death (< 57.4 versus ≥ 57.4 ms). In patients with compensated cirrhosis at baseline and in the full patient cohort, 9.6% (19 of 197) and 5.1% (15 of 292) developed decompensation and died during the mean follow-up periods of 18.7 and 19.2 months, respectively. A prolonged T2Liver (hazard ratio (HR), 2.59; 95% confidence interval (CI), 1.26, 5.31) was independently predictive of decompensation along with the serum albumin level (HR, 0.28; 95% CI, 0.12, 0.68) and MELD score (HR, 1.34; 95% CI, 1.08, 1.66). T2Liver (HR, 2.61; 95% CI, 1.19, 5.72) and serum albumin level (HR, 0.46; 95% CI, 0.19, 1.14) were independent predictors of death. The mean times to decompensation (12.9 versus 29.2 months) and death (16.5 versus 29.6 months) were significantly different between the high- and low-risk groups (p < 0.001). T2Liver from T2 mapping can predict decompensation and death in patients with cirrhosis. • Liver T2 values from the radial turbo spin-echo (TSE) T2 mapping sequence with tiered echo sharing and pseudo golden-angle (pGA) reordering were significantly higher in decompensated cirrhosis than compensated cirrhosis. • Liver T2 values from the radial TSE T2 mapping sequence with tiered echo sharing and pGA reordering can predict decompensation and death in patients with cirrhosis. • T2 mapping is recommended as part of liver MRI examinations for cirrhotic patients because it can provide a noninvasive prognostic marker for the development of decompensation and death.

Objective: This study aims to determine how magnetic resonance imaging (MRI) acquisition techniques and calculation methods affect T2 values of knee cartilage at 1.5 tesla and to identify sequences that can be used for high-resolution T2 mapping in short scanning times. Materials and Methods: This study was performed on phantom and 29 patients who underwent MRI of the knee joint at 1.5 tesla. The protocol includes T2 mapping sequences based on Single-Echo Spin Echo (SESE), Multi-Echo Spin Echo (MESE), Fast Spin Echo (FSE) and Turbo Gradient Spin Echo (TGSE). The T2 relaxation times were quantified and evaluated using three calculation methods (MapIt, Syngo Offline and mono-exponential fit). signal-to-noise ratios (SNR) were measured in all sequences. All statistical analyses were performed using the t-test. Results: The average T2 values in phantom were 41.7 ± 13.8 ms for SESE, 43.2 ± 14.4 ms for MESE, 42.4 ± 14.1 ms for FSE and 44 ± 14.5 ms for TGSE. In the patient study, the mean differences were 6.5 ± 8.2 ms, 7.8 ± 7.6 ms and 8.4 ± 14.2 ms for MESE, FSE and TGSE compared to SESE, respectively; these statistical results were not significantly different (p > 0.05). The comparison between the three calculation methods showed no significant difference (p > 0.05). The t-test showed no significant difference between SNR values for all sequences. Conclusion: T2 values depend not only on the sequence type but also on the calculation method. None of the sequences revealed significant differences compared to the SESE reference sequence. TGSE with its short scanning time can be used for high-resolution T2 mapping.

PurposeTo develop and evaluate an efficient precontrast T1 mapping technique suitable for quantitative high‐resolution whole‐brain dynamic contrast‐enhanced–magnetic resonance imaging (DCE‐MRI).MethodsVariable flip angle (VFA) T1 mapping was considered that provides 1 × 1 × 2 mm3 resolution to match a recent high‐resolution whole‐brain DCE‐MRI protocol. Seven FAs were logarithmically spaced from 1.5° to 15°. T1 and M0 maps were estimated using model‐based reconstruction. This approach was evaluated using an anatomically realistic brain tumor digital reference object (DRO) with noise‐mimicking 3T neuroimaging and fully sampled data acquired from one healthy volunteer. Methods were also applied on fourfold prospectively undersampled VFA data from 13 patients with high‐grade gliomas.ResultsT1‐mapping precision decreased with undersampling factor R, althoughwhereas bias remained small before a critical R. In the noiseless DRO, T1 bias was <25 ms in white matter (WM) and <11 ms in brain tumor (BT). T1 standard deviation (SD) was <119.5 ms in WM (coefficient of variation [COV] ~11.0%) and <253.2 ms in BT (COV ~12.7%). In the noisy DRO, T1 bias was <50 ms in WM and <30 ms in BT. For R ≤ 10, T1 SD was <107.1 ms in WM (COV ~9.9%) and <240.9 ms in BT (COV ~12.1%). In the healthy subject, T1 bias was <30 ms for R ≤ 16. At R = 4, T1 SD was 171.4 ms (COV ~13.0%). In the prospective brain tumor study, T1 values were consistent with literature values in WM and BT.ConclusionHigh‐resolution whole‐brain VFA T1 mapping is feasible with sparse sampling, supporting its use for quantitative DCE‐MRI.

A reference database of cartilage 3 T MRI T2 values in knees without diagnostic evidence of cartilage degeneration: data from the osteoarthritis initiative