Spectrum of T2* values in knee joint cartilage at 3 T: a cross-sectional analysis in asymptomatic young adult volunteers

Objective

To establish baseline T2* values in healthy knee joint cartilage at 3 T.

Materials and Methods

Thirty-four volunteers (mean age: 24.6?±?2.7 years) with no history or clinical findings indicative of any knee joint disease were enrolled. The protocol included a double-echo steady-state (DESS) sequence for morphological cartilage evaluation and a gradient-echo multi-echo sequence for T2* assessment. Bulk and zonal T2* values were assessed in eight regions: posterior lateral femoral condyle; central lateral femoral condyle; trochlea; patella; lateral tibial plateau; posterior medial femoral condyle; central medial femoral condyle; and medial tibial plateau. Statistical evaluation comprised a two-tailed t test and a one-way analysis of variance to identify zonal and regional differences.

Results

T2* mapping revealed higher T2* values in the superficial zone in all regions (P values?≤?0.001) except for the posterior medial femur condyle (P?=?0.087), and substantial regional differences demonstrating superior values in trochlear cartilage, intermediate values in patellar and central femoral condylar cartilage, and low T2* values in posterior femoral condylar cartilage and tibial plateau cartilage.

Conclusion

Substantial regional differences in T2* measures should be taken into consideration when conducting T2* mapping of knee joint cartilage.     

Reproducibility of dGEMRIC in assessment of hip joint cartilage: A prospective study

Purpose

To investigate the reproducibility of dGEMRIC in the assessment of cartilage health of the adult asymptomatic hip joint.

Materials and Methods

Fifteen asymptomatic volunteers (mean age, 26.3 years ± 3.0) were preliminarily studied. Any volunteer that was incidentally diagnosed with damaged cartilage on MRI (n = 5) was excluded. Ten patients that had no evidence of prior cartilage damage (mean age, 26.2 years ± 3.4) were evaluated further in this study. The reproducibility of dGEMRIC was assessed with two T1_Gd exams performed 4 weeks apart in these volunteers. The protocol involved an initial standard MRI to confirm healthy cartilage, which was then followed by dGEMRIC. The second scan included only the repeat dGEMRIC. Region of interest (ROI) analyses for T1_Gd‐measurement was performed in seven radial reformats. Statistical analysis included the student's t‐test and intra‐class correlation (ICC) measurement to assess reproducibility.

Results

Overall 70 ROIs were studied. Mean cartilage T1_Gd values at various loci ranged from 560.9 ms to 684.4 ms at the first set of readings and 551.5 ms to 662.2 ms in the second one. The mean difference per region of interest between the two T1_Gd‐measurements ranged from 21.4 ms (3.7%) to 45.0 ms (6.8%), which was not found to be statistically significant (P = 0.153). There was a high reproducibility detected (ICC range, 0.667–0.915). Intra‐ and Inter‐observer analyses proved a high agreement for T1_Gd assessment (0.973 and 0.932).

Conclusion

We found dGEMRIC to be a reliable tool in the assessment of cartilage health status in adult hip joints. J. Magn. Reson. Imaging 2009;30:224–228. © 2009 Wiley‐Liss, Inc.     

T2* mapping and delayed gadolinium-enhanced magnetic resonance imaging in cartilage (dGEMRIC) of glenohumeral cartilage in asymptomatic volunteers at 3 T

Objectives

To establish baseline T2* and T1_Gd values of glenohumeral cartilage at 3 T.

Methods

Forty asymptomatic volunteers (mean age: 24.8?±?2.2 years) without shoulder abnormalities were included. The MRI protocol comprised a double-echo steady-state (DESS) sequence for morphological cartilage evaluation, a gradient-echo multiecho sequence for T2* assessment, and a gradient-echo dual-flip-angle sequence for T1_Gd mapping. Statistical assessment involved a one-way analysis of variance (ANOVA) to identify the differences between various regions of the glenohumeral joint and intraclass correlation (ICC) analysis comparing repetitive T2* and T1_Gd measures to assess intra- and interobserver reliability.

Results

Both techniques revealed significant differences between superior and inferior glenohumeral cartilage demonstrating higher T2* (26.2 ms vs. 23.2 ms, P value?<?0.001) and T1_Gd (750.1 ms vs. 720.2 ms, P value?=?0.014) values in the superior regions. No trend was observed in the anterior-posterior measurement (P value range: 0.279–1.000). High intra- and interobserver agreement (ICC value range: 0.895–0.983) was noted for both T2* and T1_Gd mapping.

Conclusions

T2* and T1_Gd mapping are reliable in the assessment of glenohumeral cartilage. The values from this study can be used for comparison to identify cartilage degeneration in patients suffering from shoulder joint abnormalities.

Key Points

? T2* mapping and dGEMRIC are sensitive to collagen degeneration and proteoglycan depletion. ? This study aimed to establish baseline T2*/dGEMRIC values of glenohumeral cartilage. ? Both techniques revealed significant differences between superior and inferior glenohumeral cartilage. ? High intra-/interreader agreement was noted for both T2* mapping and dGEMRIC. ? These baseline normal values should be useful when identifying potential degeneration.     

The in vivo effects of unloading and compression on T1-Gd (dGEMRIC) relaxation times in healthy articular knee cartilage at 3.0 Tesla

Purpose

The purpose was to investigate the in vivo effects of unloading and compression on T1-Gd relaxation times in healthy articular knee cartilage.

Materials and methods

Ten volunteers were enrolled, and dGEMRIC images of their right knee joints were obtained using 3.0-T MR at three timepoints: directly following exercise (“baseline”), approximately 15 min after unloading (“unloading”) and during application of a compressive force (50% of the body weight) generated by a loading device via a footplate (“compression”).

Results

Our analysis of variance of pooled data from all cartilage zones demonstrated a significant mean T1-Gd decrease of 56.6 ms between baseline and compression (p?<?0.001), and a significant mean decrease of 42.1 ms between unloading and compression (p?<?0.001). No significant difference was found between baseline and unloading. Higher mean T1-Gd values were observed in the cartilage contact zone (central femoral and tibial zones; 698.3?±?162.2 ms) than in the non-contact zone (anterior and posterior femoral and tibial zones, and dorsal femoral zone; 662.9?±?149.3 ms; p?<?0.01).

Conclusion

T1-Gd times appear to be sensitive to mechanical cartilage stress, and thus, further studies are warranted that investigate the relationship between the biochemical load response and the biomechanical properties of articular cartilage.     

High resolution fast T1 mapping technique for dGEMRIC

Purpose

To determine the feasibility of using a high resolution isotropic three‐dimensional (3D) fast T1 mapping sequence for delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) to assess osteoarthritis in the hip.

Materials and Methods

T1 maps of the hip were acquired using both low and high resolution techniques following the administration of 0.2 mmol/kg Gd‐DTPA^2‐ in 35 patients. Both T1 maps were generated from two separate spoiled GRE images. The high resolution T1 map was reconstructed in the anatomically equivalent plane as the low resolution map. T1 values from the equivalent anatomic regions containing femoral and acetabular cartilages were measured on the low and high resolution maps and compared using regression analysis.

Results

In vivo T1 measurements showed a statistically significant correlation between the low and high resolution acquisitions at 1.5 Tesla (R² = 0.958, P < 0.001). These results demonstrate the feasibility of using a fast two‐angle T1 mapping (F2T1) sequence with isotropic spatial resolution (0.8 × 0.8 × 0.8 mm) for quantitative assessment of biochemical status in articular cartilage of the hip.

Conclusion

The high resolution 3D F2T1 sequence provides accurate T1 measurements in femoral and acetabular cartilages of the hip, which enables the biochemical assessment of articular cartilage in any plane through the joint. It is a powerful tool for researchers and clinicians to acquire high resolution data in a reasonable scan time (< 30 min). J. Magn. Reson. Imaging 2009;30:896–900. © 2009 Wiley‐Liss, Inc.     

High-resolution MRI of excised human prostate specimens acquired with 9.4T in detection and identification of cancers: validation of a technique

Purpose:

To evaluate feasibility of high‐resolution, high‐field ex vivo prostate magnetic resonance imaging (MRI) as an aid to guide pathologists' examination and develop in vivo MRI methods.

Materials and Methods:

Unfixed excised prostatectomy specimens (n = 9) were obtained and imaged immediately after radical prostatectomy under an Institutional Review Board‐approved protocol. High‐resolution T2‐weighted (T2W) MRI of specimens were acquired with a Bruker 9.4 T scanner to correlate with whole‐mount histology. Additionally, T2 and apparent diffusion coefficient (ADC) maps were generated.

Results:

By visual inspection of the nine prostate specimens imaged, high‐resolution T2W MRI showed improved anatomical detail compared to published low‐resolution images acquired at 4 T as published by other investigators. Benign prostatic hyperplasia, adenocarcinomas, curvilinear duct architecture distortion due to adenocarcinomas, and normal radial duct distribution were readily identified. T2 was ≈10 msec longer (P < 0.03) and the ADC was ≈1.4 times larger (P < 0.002) in the normal peripheral zone compared to the peripheral zone with prostate cancer.

Conclusion:

Differences in T2 and ADC between benign and malignant tissue are consistent with in vivo data. High‐resolution, high‐field MRI has the potential to improve the detection and identification of prostate structures. The protocols and techniques developed in this study could augment routine pathological analysis of surgical specimens and guide treatment of prostate cancer patients. J. Magn. Reson. Imaging 2011. © 2011 Wiley‐Liss, Inc.     

Longitudinal and multi-echo transverse relaxation times of normal breast tissue at 3 Tesla

Purpose

To measure longitudinal (T₁) and multi‐echo transverse (T₂) relaxation times of healthy breast tissue at 3 Tesla (T).

Materials and Methods

High‐resolution relaxation time measurements were made in six healthy female subjects. Inversion recovery images were acquired at 10 inversion times between 100 ms and 4000 ms, and multiple spin echo images were acquired at 16 echo times between 10 ms and 160 ms.

Results

Longitudinal relaxation times T₁ were measured as 423 ± 12 ms for adipose tissue and 1680 ± 180 ms for fibroglandular tissue. Multi‐echo transverse relaxation times T₂ were measured as 154 ± 9 ms for adipose tissue and 71 ± 6 ms for fibroglandular tissue. Histograms of the voxel‐wise relaxation times and quantitative relaxation time maps are also presented.

Conclusion

T₁ and multi‐echo T₂ relaxation times in normal human breast tissue are reported. These values are useful for pulse sequence design and optimization for 3T breast MRI. Compared with the literature, T₁ values are significantly longer at 3T, suggesting that longer repetition time and inversion time values should be used for similar image contrast. J. Magn. Reson. Imaging 2010;32:982–987. © 2010 Wiley‐Liss, Inc.     

Three-dimensional delayed gadolinium-enhanced magnetic resonance imaging of hip joint cartilage at 3T: A prospective controlled study

Purpose

To assess acetabular and femoral hip joint cartilage with three-dimensional (3D) delayed gadolinium-enhanced magnetic resonance imaging (dGEMRIC) in patients with degeneration of hip joint cartilage and asymptomatic controls with morphologically normal appearing cartilage.

Methods and materials

A total of 40 symptomatic patients (18 males, 22 females; mean age: 32.8 ± 10.2 years, range: 18–57 years) with different hip joint deformities including femoroacetabular impingement (n = 35), residual hip dysplasia (n = 3) and coxa magna due to Legg–Calve–Perthes disease in childhood (n = 2) underwent high-resolution 3D dGEMRIC for the evaluation of acetabular and femoral hip joint cartilage. Thirty-one asymptomatic healthy volunteers (12 males, 19 females; mean age: 24.5 ± 1.8 years, range: 21–29 years) without underlying hip deformities were included as control. MRI was performed at 3 T using a body matrix phased array coil. Region of interest (ROI) analyses for T1_Gd assessment was performed in seven regions in the hip joint, including anterior to superior and posterior regions.

Results

T1_Gd mapping demonstrated the typical pattern of acetabular cartilage consistent with a higher glycosaminoglycan (GAG) content in the main weight-bearing area. T1_Gd values were significantly higher in the control group than in the patient group whereas significant differences in T1_Gd values corresponding to the amount of cartilage damage were noted both in the patient group and in the control group.

Conclusions

Our study demonstrates the potential of high-resolution 3D dGEMRIC at 3 T for separate acetabular and femoral hip joint cartilage assessment in various forms of hip joint deformities.     

Myocardial T1 mapping with MRI: comparison of look-locker and MOLLI sequences

Purpose:

To evaluate the relationship between “Look‐Locker” (LL) and modified Look‐Locker Inversion recovery (MOLLI) approaches for T1 mapping of the myocardium.

Materials and Methods:

A total of 168 myocardial T1 maps using MOLLI and 165 maps using LL were obtained in human subjects at 1.5 Tesla. The T1 values of the myocardium were calculated before and at five time points after gadolinium administration. All time and heart rate normalizations were done. The T1 values obtained were compared to determine the absolute and bias agreement.

Results:

The precontrast global T1 values were similar when measured by the LL and by MOLLI technique (mean, 1004.9 ms ± 120.3 versus 1034.1 ms ± 53.1, respectively, P = 0.26). Postcontrast myocardial T1 time from LL was significantly longer than MOLLI from 5 to 25 min (mean difference, LL ‐ MOLLI was +61.8 ± 46.4 ms, P < 0.001). No significant differences in T1 values were noted between long and short axis measurements for either MOLLI or LL.

Conclusion:

Postcontrast LL and MOLLI showed very good agreement, although LL values are higher than MOLLI. Precontrast T1 values showed good agreement, however LL has greater limits of agreement. Short and long axis planes can reliably assess T1 values. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.     

Quantitative evaluation of liver cirrhosis using T1 relaxation time with 3 tesla MRI before and after oxygen inhalation

Purpose:

To quantify liver T1 relaxation times before and after oxygen inhalation in patients with and without liver cirrhosis using a 3 Tesla (T) MRI.

Materials and Methods:

Institutional Review Board approval and written informed consent were obtained. Ninety‐two noncirrhotic patients and 87 patients with hepatitis B viral liver cirrhosis (72 Child‐Pugh class A and 15 Child‐Pugh class B or C) underwent MRI with a 3.0T system before and after the supply of 100% oxygen at a rate of 15 L/min by means of a nonrebreather ventilation mask for 3 min. T1 maps were acquired using three‐dimensional spoiled gradient echo sequences with two different flip angles (2° and 14°) and a fixed TR/TE (2.54 ms/0.95 ms). Liver T1 values were obtained using a T1 processing tool (MapIT software). The mean baseline T1 values of three groups (control, Child‐Pugh class A, and Child‐Pugh class B/C) were compared using an analysis of variance test. Liver T1 value before and after oxygenation was compared using a paired t‐test for each group.

Results:

The baseline liver T1 value was significantly higher in the control group (941 ± 136 ms) than in Child‐Pugh A (858 ± 143 ms) and Child‐Pugh B/C (783 ± 164 ms) group (P < 0.001 and P < 0.0001). The reduction in the liver T1 value after oxygen inhalation was significant in the control group (P = 0.012) but not significant in Child‐Pugh class A (P = 0.079) and Child‐Pugh class B/C (P = 0.752).

Conclusion:

The baseline liver T1 relaxation time was significantly different between the patients with and without liver cirrhosis. The shortening effect of oxygen on the liver T1 value was significant in the control group but not in the cirrhotic patients. J. Magn. Reson. Imaging 2012;36:405–410. © 2012 Wiley Periodicals, Inc.     

Neuroimaging assessment of memory‐related brain structures in a rat model of acute space‐like radiation

Purpose

To investigate the acute effects on the central nervous system (CNS) of ⁵⁶Fe radiation, a component of high‐energy charged particles (HZE) in space radiation, using quantitative magnetic resonance imaging (MRI) noninvasively.

Materials and Methods

Sprague–Dawley rats were exposed to whole‐brain ⁵⁶Fe (0, 1, 2, and 4 Gy). At 1 week postirradiation, MRI scans were made using T2‐weighted (T2WI), diffusion‐weighted (DWI), and contrast enhanced T1‐(CET1) imaging. T2 relaxation time and apparent diffusion coefficient (ADC) values were obtained from memory‐related brain regions of interest (ROIs). Histopathology was correlated using ex vivo tissues.

Results

No overt abnormalities were visualized using T2WI and DWI at 1 week postradiation. CET1 values did not differ significantly between the irradiated and control animals. Compared to 0 Gy, there were significant prolongations in T2 values and reductions in ADC after irradiation. In the absence of evident neuronal pathology, immunohistochemistry revealed astrocytic activation in 4 Gy animals.

Conclusion

At 1 week after whole‐brain ⁵⁶Fe exposure, T2 and ADC values can differentiate radiosensitivity in regions critical for hippocampal‐related memory. MRI may provide noninvasive assessment of the initial molecular/cellular disturbances in vivo after HZE irradiation. J. Magn. Reson. Imaging 2009;29:785–792. © 2009 Wiley‐Liss, Inc.     

7T head volume coils: Improvements for rostral brain imaging

Purpose

To improve the performance of 7T head coils over the rostral head regions. Due to radiofrequency (RF) field/tissue interactions, the RF magnetic field profile produced by 7T volume head coils is very inhomogeneous, with enhanced sensitivity near the center of the human brain and substantially reduced in the periphery.

Materials and Methods

Two head‐sized quadrature volume coils of similar diameters but substantially different lengths (17 and 10 cm) were constructed and tested using a 7T Varian Inova system.

Results

Experimental data demonstrated that by using a shorter volume head‐sized coil or simply by partially moving a head out of the coil, coil efficiency near the top of a head can be improved by 20%. The homogeneity also improved, largely resulting from an increase in peripheral B₁ values. This resulted in 10%–20% variation in axial slices located near the top of a head.

Conclusion

We have demonstrated a less deeply positioned head or substantially shorter volume coil can significantly improve coil performance and homogeneity for the rostral head at ultrahigh magnetic fields (7T and above). For studies that target superior brain regions, this coil arrangement can be highly effective. J. Magn. Reson. Imaging 2009;29:461–465. © 2009 Wiley‐Liss, Inc.     

T2 values of articular cartilage in clinically relevant subregions of the asymptomatic knee

Purpose

In order for T2 mapping to become more clinically applicable, reproducible subregions and standardized T2 parameters must be defined. This study sought to: (1) define clinically relevant subregions of knee cartilage using bone landmarks identifiable on both MR images and during arthroscopy and (2) determine healthy T2 values and T2 texture parameters within these subregions.

Methods

Twenty-five asymptomatic volunteers (age 18–35) were evaluated with a sagittal T2 mapping sequence. Manual segmentation was performed by three raters, and cartilage was divided into twenty-one subregions modified from the International Cartilage Repair Society Articular Cartilage Mapping System. Mean T2 values and texture parameters (entropy, variance, contrast, homogeneity) were recorded for each subregion, and inter-rater and intra-rater reliability was assessed.

Results

The central regions of the condyles had significantly higher T2 values than the posterior regions (P < 0.05) and higher variance than the posterior region on the medial side (P < 0.001). The central trochlea had significantly greater T2 values than the anterior and posterior condyles. The central lateral plateau had lower T2 values, lower variance, higher homogeneity, and lower contrast than nearly all subregions in the tibia. The central patellar regions had higher entropy than the superior and inferior regions (each P ≤ 0.001). Repeatability was good to excellent for all subregions.

Conclusion

Significant differences in mean T2 values and texture parameters were found between subregions in this carefully selected asymptomatic population, which suggest that there is normal variation of T2 values within the knee joint. The clinically relevant subregions were found to be robust as demonstrated by the overall high repeatability.     

Modulated repetition time look‐locker (MORTLL): A method for rapid high resolution three‐dimensional T1 mapping

Purpose

To demonstrate a modification of the Look‐Locker (LL) technique that enables rapid high resolution T1 mapping over the physiologic range of intracranial T1 values, ranging from white matter to cerebrospinal fluid (CSF). This is achieved by use of a three‐dimensional (3D) balanced steady‐state free precession (b‐SSFP) acquisition (for high signal‐to‐noise and resolution) along with variable repetition time to allow effective full recovery of longitudinal magnetization.

Materials and Methods

Two modifications to the Look‐Locker technique were made to realize high resolution imaging in a clinically reasonable scan time. The 3D b‐SSFP acquisition after an initial inversion pulse was followed by a variable repetition time. This technique makes it possible to image a volume of thin contiguous slices with high resolution and accuracy using a simple fitting procedure and is particularly useful for imaging long T1 species such as CSF. The total scan time is directly proportional to the number of slices to be acquired. The scan time was reduced by almost half when the repetition time was modified using a predesigned smooth function. Phantoms and volunteers were imaged at different resolutions on a 3 Tesla scanner. Results were compared with other accepted techniques.

Results

T1 values in the brain corresponded well with full repetition time imaging as well as inversion recovery spin echo imaging. T1 values for white matter, gray matter, and CSF were measured to be 755 ± 10 ms, 1202 ± 9 ms, and 4482 ± 71 ms, respectively. Scan times were reduced by approximately half over full repetition time measurements.

Conclusion

High resolution T1 maps can be obtained rapidly and with a relatively simple postprocessing method. The technique is particularly well suited for long T1 species. For example, changes in the composition of proteins in CSF are linked to various pathologies. The T1 values showed excellent agreement with values obtained from inversion recovery spin‐echo imaging. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.     

Changes in apparent diffusion coefficient and T2 relaxation during radiotherapy for prostate cancer

Purpose:

To evaluate regional and temporal changes in apparent diffusion coefficient (ADC) and T₂ relaxation during radiation therapy (RT) in patients with low and intermediate risk localized prostate cancer.

Materials and Methods:

Seventeen patients enrolled on a prospective clinical trial where MRI was acquired every 2 weeks throughout eight weeks of image‐guided prostate IMRT (78 Gy/39 fractions). ADC and T₂ quantification used entire prostate, central gland, benign peripheral zone, and tumor‐dense regions‐of‐interest, and mean values were evaluated for common response trends.

Results:

Overall, the RT responses were greater than volunteer measurement repeatability, and week 6 appeared to be an optimum time‐point for early detection. RT effects on the entire prostate were best detected using ADC (5–7% by week 2, P < 0.0125), effects on peripheral zone were best detected using T₂ (19% reduction at week 6; P = 0.004) and effects on tumors were best detected using ADC (14% elevation at week 6; P = 0.004).

Conclusion:

ADC and T₂ may be candidate biomarkers of early response to RT warranting further investigation against clinical outcomes. J. Magn. Reson. Imaging 2013;37:909–916. © 2012 Wiley Periodicals, Inc.     

Significant changes of T2 value in the peripheral zone and seminal vesicles after ejaculation

Objectives

To analyse the quantitative changes of the prostate and seminal vesicles (SV) on magnetic resonance imaging (MRI) after ejaculation.

Methods

Ten healthy young males were enrolled for T2-weighted and T2 mapping MRI before and after two consecutive ejaculations. T2 values of the peripheral zone (PZ) and the central gland (CG) at the midgland of the prostate were compared before and after ejaculation, respectively. T2 values of the PZ at the apex and base were also compared before and after, respectively. Pre- and post-ejaculation SV volumes were compared. The Wilcoxon’s signed rank test with Bonferroni adjustment was used for comparison.

Results

After ejaculation, T2 values of the PZ significantly decreased (mean, 119±20 vs. 105±21, p=0.002) while those of the CG did not significantly change at the midgland. At the apex, T2 values of the PZ also decreased significantly (mean, 114±9 vs. 94±7, p=0.002). On the other hand, T2 values of the PZ did not change at the base. SV volumes were significantly reduced after ejaculation (mean, 11.1±7.7mL vs. 7.2±6.7mL, p=0.002).

Conclusions

Ejaculation decreases T2 values of the PZ at the midgland and apex, and reduces SV volumes. Abstinence periods should be considered in evaluating the prostate and SV on MRI.

Key points

? T2 values decrease after ejaculation in the apical-mid peripheral zone. ? Ejaculation does not affect T2 values of the central gland. ? Volume of the seminal vesicles decreases after ejaculation. ? An abstinence period should be considered before pelvic MRI in men.

     

Myocardial T2 quantitation in patients with iron overload at 3 Tesla

Purpose

To investigate the feasibility of measuring myocardial T2 at 3 Tesla for assessment of tissue iron in thalassemia major and other iron overloaded patients.

Materials and Methods

A single‐breathhold electrocardiogram‐triggered black‐blood multi‐echo spin‐echo (MESE) sequence with a turbo factor of 2 was implemented at 3 Tesla (T). Myocardial and liver T2 values were measured with three repeated breathholds in 8 normal subjects and 24 patients. Their values, together with the T2* values measured using a breathhold multi‐echo gradient‐echo sequence, were compared with those at 1.5T in the same patients.

Results

At 3T, myocardial T2 was found to be 39.6 ± 7.4 ms in normal subjects. In patients, it ranged from 12.9 to 50.1 ms. T2 and T2* were observed to correlate in heart (ρ = 0.93, ρ < 0.0001) and liver (P = 0.95, P < 0.0001). Myocardial T2 and T2* at 3T were also highly correlated with the 1.5T measurements. Preliminary results indicated that myocardial T2 quantitation was relatively insensitive to B1 variation, and reproducible with 3.2% intra‐exam and 3.8% inter‐exam variations.

Conclusion

Myocardial T2 quantitation is feasible at 3T. Given the substantially decreased T2* and increased B0 inhomogeneity, the rapid myocardial T2 measurement protocol demonstrated here may present a robust alternative to study cardiac iron overload at 3T. J. Magn. Reson. Imaging 2009;30:394–400. © 2009 Wiley‐Liss, Inc.     

Using diffusion tensor imaging and immunofluorescent assay to evaluate the pathology of multiple sclerosis

Purpose:

To determine the ability of the principal diffusion tensor imaging (DTI) indices to predict the underlying histopathology evaluated with immunofluorescent assay (IFA).

Materials and Methods:

Conventional T2 and 3D multishot‐diffusion weighted echoplanar imaging (3D ms‐DWEPI) was performed on a fixed, ex vivo human cervical spinal cord (CSC) from a patient with a history of multiple sclerosis (MS). In all, 170 regions of interest (ROIs) were selected within the white matter and categorized as a high intensity lesion (HIL), low intensity lesion (LIL), and normal‐appearing white matter (NAWM). The longitudinal diffusivity (λl), radial diffusivity (λr), and fractional anisotropy (FA) were obtained from each ROI. The underlying histopathology was then evaluated using immunofluorescent assay with antibodies directed to myelin and neurofilament staining.

Results:

The mean values for λl and λr were significantly elevated within HIL relative to NAWM and LIL. IFA analysis of HIL demonstrated significant demyelination, without significant if any axon loss. The FA values were significantly reduced in HIL and LILs. FA values were also reduced in lesions with increased λl and λr values relative to normal.

Conclusion:

Aberrant λl, λr, and FA relative to normal values are strong indicators of demyelination. DTI indices are not specific for axon loss. IFA analysis is a reliable method to demonstrate myelin and axon pathology within the ex vivo setting. J. Magn. Reson. Imaging 2011;33:557–564. © 2011 Wiley‐Liss, Inc.     

T1 mapping using saturation recovery single-shot acquisition at 3-tesla magnetic resonance imaging in hypertrophic cardiomyopathy: comparison to late gadolinium enhancement

Purpose

We evaluated the T1 values of segments and slices and the reproducibility in healthy controls, using saturation recovery single-shot acquisition (SASHA) at 3T magnetic resonance imaging. Moreover, we examined the difference in T1 values between hypertrophic cardiomyopathy (HCM) and healthy controls, and compared those with late gadolinium enhancement (LGE).

Materials and methods

Twenty-one HCM patients and 10 healthy controls underwent T1 mapping before and after contrast administration. T1 values were measured in 12 segments.

Results

Native T1 values were significantly longer in HCM than in healthy controls [1373 ms (1312–1452 ms) vs. 1279 ms (1229–1326 ms); p < 0.0001]. Even in HCM segments without LGE, native T1 values were significantly longer than in healthy control segments [1366 ms (1300–1439 ms) vs. 1279 ms (1229–1326 ms); p < 0.0001]. Using a cutoff value of 1327 ms for septal native T1 values, we differentiated between HCM and healthy controls with 95% sensitivity, 90% specificity, 94% accuracy, and an area under the curve of 0.95.

Conclusions

Native T1 values using a SASHA at 3T could differentiate HCM from healthy controls. Moreover, native T1 values have the potential to detect abnormal myocardium that cannot be identified adequately by LGE in HCM.

     

Effect of intra-articular injection of intermediate-weight hyaluronic acid on hip and knee cartilage: in-vivo evaluation using T2 mapping

Objectives

We used T2 mapping to quantify the effect of intra-articular hyaluronic acid administration (IAHAA) on cartilage with correlation to clinical symptoms.

Methods

One hundred two patients with clinical and MRI diagnosis of hip or knee grade I-III chondropathy were prospectively included. All patients received a standard MRI examination of the affected hip/knee (one joint/patient) and T2-mapping multiecho sequence for cartilage evaluation. T2 values of all slices were averaged and used for analysis. One month after MR evaluation 72 patients (38 males; mean age 51±10 years) underwent IAHAA. As a control group, 30 subjects (15 males; 51 ± 9 years) were not treated. MR and WOMAC evaluation was performed at baseline and after 3, 9, and 15 months in all patients.

Results

T2 mapping in hyaluronic acid (HA) patients showed a significant increase in T2 relaxation times from baseline to the first time point after therapy in knees (40.7 ± 9.8 ms vs. 45.8 ± 8.6 ms) and hips (40.9 ± 9.7 ms; 45.9 ± 9.5 ms) (p < 0.001). At the 9- and 15-month evaluations, T2 relaxation dropped to values similar to the baseline ones (p < 0.001 vs. 3 month). The correlation between T2 increase and pain reduction after IAHAA was statistically significant (r = 0.54, p < 0.01) in patients with grade III chondropathy.

Conclusions

T2 mapping can be used to evaluate the effect over time of IAHAA in patients with hip and knee chondropathy.

Key points

? T2 relaxation times change over time after hyaluronic acid intra-articular administration? T2 relaxation times of the medial femoral condyle correlate with WOMAC variation? T2 relaxation times are different between Outerbridge I and II-III