Delayed contrast enhanced MRI of meniscus with ionic and non-ionic agents

Purpose:

To evaluate the potential difference in post‐contrast T₁ relaxation time of the meniscus (T_1Gd) between osteoarthritic patients (OA) and healthy subjects (HS), and to verify if charge density has any influence on meniscal T_1Gd.

Materials and Methods:

We performed a retrospective analysis of meniscal T₁ relaxation time on data previously acquired for studying articular cartilage with both ionic and non‐ionic contrast media. MR imaging was performed in 10 OA and 8 HS at 120 min following administration of double‐dose ionic Gd‐DTPA^2? on one day and non‐ionic Gd‐DTPA‐BMA on a different day. A three‐dimensional Look‐Locker sequence with echo time of 2 ms was used for data acquisition to allow T₁ mapping of the meniscus.

Results:

Compared with HS, significantly lower meniscal T_1Gd was observed in OA with either ionic Gd‐DTPA^2? (P < 0.01) or non‐ionic Gd‐DTPA‐BMA (P < 0.001) contrast agent. There was a correlation between meniscal T₁(Gd‐DTPA^2?) versus T₁(Gd‐DTPA‐BMA). Meniscal T₁(Gd‐DTPA‐BMA) showed a larger difference and smaller overlap between OA and HS. No significant differences in either pre‐contrast T₁ or post‐contrast T_1Gd were observed between inner and outer zones of the meniscus with either agent.

Conclusion:

Significant differences in meniscal T_1Gd between OA and HS were observed with both ionic and non‐ionic contrast agents, suggesting that charge density is not responsible for the observed differences. J. Magn. Reson. Imaging 2011;33:731–735. © 2011 Wiley‐Liss, Inc.

     

In vivo transport of Gd-DTPA(2-) in human knee cartilage assessed by depth-wise dGEMRIC analysis

Purpose:

To investigate the transport of Gd‐DTPA^2? in different layers of femoral knee cartilage in vivo.

Materials and Methods:

T₁ measurements (1.5 Tesla) were performed in femoral knee cartilage of 23 healthy volunteers. The weight‐bearing central cartilage was analyzed before contrast and at eight time points after an intravenous injection of Gd‐DTPA^2?: 12–60 min (4 volunteers) and 1–4 h (19 volunteers). Three regions of interest were segmented manually: deep, middle, and superficial.

Results:

Before contrast injection, a depth‐wise variation of T₁ was observed with 50% higher values in the superficial region compared with the deep region. In the deep region, the uptake of Gd‐DTPA^2? was not detected until 36 min and the concentration increased until 240 min, whereas in the superficial region, the uptake was seen already at 12 min and the concentration decreased after 180 min (P < 0.01). There was a difference between medial and lateral compartment regarding bulk, but not superficial Gd‐DTPA^2? concentration. The bulk gadolinium concentration was negatively related to the cartilage thickness (r = ?0.68; P < 0.01).

Conclusion:

The depth‐wise and thickness dependent variations in Gd‐DTPA² transport influence the interpretation of bulk dGEMRIC analysis in vivo. In thick cartilage, incomplete penetration of Gd‐DTPA² will yield a falsely too long T₁. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

     

Delayed contrast‐enhanced MRI of cartilage: Comparison of nonionic and ionic contrast agents

The objective of this study was to evaluate if cartilage fixed charge density is the only factor determining the distribution of the measured delayed gadolinium‐enhanced magnetic resonance imaging of cartilage index, T₁(Gd‐DTPA^2?), across cartilage in the clinical delayed gadolinium‐enhanced magnetic resonance imaging of cartilage protocol. Nineteen subjects with osteoarthritis and 14 controls were included. Cartilage T₁(Gd) was measured following administration of 0.2 mmol kg^?1 of nonionic (Gd‐DTPA‐BMA) and, at a different date, anionic (Gd‐DTPA^2?). T₁(Gd‐DTPA‐BMA) was plotted against T₁(Gd‐DTPA^2?); a slope of 0 would indicate domination by charge effects; a nonzero slope would suggest that other factors influence T₁(Gd‐DTPA‐BMA), and hence potentially T₁(Gd‐DTPA^2?). The low slope of the curve found in osteoarthritis subjects (0.31) indicates that Gd‐DTPA‐BMA penetrated most osteoarthritis cartilage to the same extent, and T₁(Gd‐DTPA‐BMA) did not differentiate cartilages, which were differentiated by T₁(Gd‐DTPA^2?). The higher slopes in control subjects (0.88) are possibly due to inhibited transport of contrast agent into healthier cartilage, potentially exaggerated by the fast body clearance of the nonionic contrast agent. Overall, the use of anionic Gd‐DTPA^2? for delayed gadolinium‐enhanced magnetic resonance imaging of cartilage is indicated for better discrimination of the health status of cartilage. Future studies could be designed to use contrast‐enhanced dynamics to understand the transport properties of tissues in the joint and to evaluate the concentration of tissue constituents. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

In vivo MRI of fresh stored osteochondral allograft transplantation with delayed gadolinium‐enhanced MRI of cartilage: Protocol considerations and recommendations

The protocol for delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) was adapted for the evaluation of transplanted osteochondral allograft cartilage. Eight patients with focal grade 4 cartilage defects of the femoral condyle were treated with single cylindrical osteochondral allografts. At 1 and 2 years, dGEMRIC image sequences were acquired and regions of interest (ROIs) were drawn in repair and native control cartilage. Mean T₁ values of region of interest were used to calculate established dGEMRIC metrics. The correlation was measured between the ΔR₁ and R₁‐Post metrics for repair and native cartilage. T₁ times were measured in deep and superficial zones of cartilage. A strong correlation was identified between full‐thickness, deep, and superficial ΔR₁ and R₁‐Post values for native cartilage and repair cartilage for all years (range: 0.893–1.0). The mean T₁ times and ΔR₁ rate between deep and superficial regions of articular cartilage were statistically different for all regions of the distal femora analyzed at 1 year and 2 years after osteochondral allograft transplantation (P < 0.05). The dGEMRIC pre‐Gadolinium scan is unnecessary when evaluating transplanted osteochondral allograft cartilage. The observation of stratified T₁ and ΔR₁ values indicates a need to re‐evaluate the methodology behind the placement of region of interest in dGEMRIC. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

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.     

Delayed gadolinium‐enhanced magnetic resonance imaging (dGEMRIC) of hip joint cartilage in femoroacetabular impingement (FAI): Are pre‐ and postcontrast imaging both necessary?

The purpose of this study was to assess if delayed gadolinium MRI of cartilage using postcontrast T₁ (T_1Gd) is sufficient for evaluating cartilage damage in femoroacetabular impingement without using noncontrast values (T₁₀). T_1Gd and ΔR₁ (1/T_1Gd ? 1/T₁₀) that include noncontrast T₁ measurements were studied in two grades of osteoarthritis and in a control group of asymptomatic young‐adult volunteers. Differences between T_1Gd and ΔR₁ values for femoroacetabular impingement patients and volunteers were compared. There was a very high correlation between T_1Gd and ΔR₁ in all study groups. In the study cohort with Tonnis grade 0, correlation (r) was ?0.95 and ?0.89 with Tonnis grade 1 and ?0.88 in asymptomatic volunteers, being statistically significant (P < 0.001) for all groups. For both T_1Gd and ΔR₁, a statistically significant difference was noted between patients and control group. Significant difference was also noted for both T_1Gd and ΔR₁ between the patients with Tonnis grade 0 osteoarthritis and those with grade 1 changes. Our results prove a linear correlation between T_1Gd and ΔR₁, suggesting that T_1Gd assessment is sufficient for the clinical utility of delayed gadolinium MRI of cartilage in this setting and additional time‐consuming T₁₀ evaluation may not be needed. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Magnetic resonance imaging and histology of ovine hip joint cartilage in two age populations: a sheep model with assumed healthy cartilage

Objective

To compare morphologically normal appearing cartilage in two age groups with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) and correlate magnetic resonance imaging (MRI) findings with histology.

Materials and methods

Twenty femoral head specimens collected from ten lambs (group I) and ten young adult sheep (group II) underwent dGEMRIC and histological assessment. A region of 2 cm² with morphologically normal-appearing cartilage was marked with a surgical suture for subsequent matching of MRI and histological sections. The MRI protocol included a three-dimensional (3D) double-echo steady-state sequence for morphological cartilage assessment, a B1 pre-scan with various flip angles for B1 field heterogeneity correction, and 3D volumetric interpolated breathhold examination for T1_Gd mapping (dGEMRIC). Histological analysis was performed according to the Mankin scoring system.

Results

A total of 303 regions of interest (ROI; 101 MRI reformats matching 101 histological sections) was assessed. Twenty-six ROIs were excluded owing to morphologically apparent cartilage damage or insufficient MR image quality. Therefore, 277 ROIs were analyzed. Histological analyses revealed distinct degenerative changes in various cartilage samples of group II (young adult sheep). Corresponding T1_Gd values were significantly lower in the group of sheep (mean T1_Gd?=?540.4 ms) compared with the group of lambs (mean T1_Gd?=?623.6 ms; p?<?0.001).

Conclusions

Although morphologically normal, distinct cartilage degeneration may be present in young adult sheep cartilage. dGEMRIC can reveal these changes and may be a tool for the assessment of early cartilage degeneration.     

Cartilage quality in rheumatoid arthritis: comparison of T2* mapping, native T1 mapping, dGEMRIC, ΔR1 and value of pre-contrast imaging

Purpose

To prospectively evaluate four non-invasive markers of cartilage quality—T2* mapping, native T1 mapping, dGEMRIC and ΔR1—in healthy volunteers and rheumatoid arthritis (RA) patients.

Materials and methods

Cartilage of metacarpophalangeal (MCP) joints II were imaged in 28 consecutive subjects: 12 healthy volunteers [9 women, mean (SD) age 52.67 (9.75) years, range 30–66] and 16 RA patients with MCP II involvement [12 women, mean (SD) age 58.06 (12.88) years, range 35–76]. Sagittal T2* mapping was performed with a multi-echo gradient-echo on a 3?T MRI scanner. For T1 mapping the dual flip angle method was applied prior to native T1 mapping and 40?min after gadolinium application (delayed gadolinium-enhanced MRI of cartilage, dGEMRIC, T1_Gd). The difference in the longitudinal relaxation rate induced by gadolinium (ΔR1) was calculated. The area under the receiver operating characteristic curve (AROC) was used to test for differentiation of RA patients from healthy volunteers.

Results

dGEMRIC (AUC 0.81) and ΔR1 (AUC 0.75) significantly differentiated RA patients from controls. T2* mapping (AUC 0.66) and native T1 mapping (AUC 0.66) were not significantly different in RA patients compared to controls.

Conclusions

The data support the use of dGEMRIC for the assessment of MCP joint cartilage quality in RA. T2* and native T1 mapping are of low diagnostic value. Pre-contrast T1 mapping for the calculation of ΔR1 does not increase the diagnostic value of dGEMRIC.     

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.     

Effect of Gd-DTPA-BMA on choline signals of HT29 tumors detected by in vivo 1H MRS

Purpose

To study the impact of Gd‐DTPA‐BMA on choline signals of HT29 colon carcinomas determined by localized ¹H MRS in vivo at 4.7T.

Materials and Methods

PRESS ¹H MR spectra (2‐second repetition time and echo times of 20–272 msec) were acquired from HT29 xenografts prior to and following intravenous administration of 0.1 or 0.2 mmol/kg Gd‐DTPA‐BMA. The magnetic resonance spectroscopy (MRS) data were analyzed by 1) normalizing choline and water peak areas to their precontrast values; and 2) estimating absolute choline concentration relative to tissue water.

Results

Changes in the T₁ and T₂ of choline and water were apparent following administration of Gd‐DTPA‐BMA. Administration of 0.1 mmol/kg Gd‐DTPA‐BMA induced significant increases in the choline peak area, concomitant with enhancements of the water peak area, whereas 0.2 mmol/kg Gd‐DTPA‐BMA induced no enhancement of choline peak area but significant increases in water peak area at short echo times.

Conclusion

The effect of Gd‐DTPA‐BMA on estimation of tumor choline concentration varied with the dose of contrast agent, the echo time, and the time after contrast agent administration. These data highlight the potential pitfalls associated with the modulation of choline and water signals post‐Gd‐DTPA‐BMA and may account for the apparently contradictory results previously reported. J. Magn. Reson. Imaging 2008;28:1201–1208. © 2008 Wiley‐Liss, Inc.     

7 Tesla quantitative hip MRI: T1, T2 and T2* mapping of hip cartilage in healthy volunteers

Objectives

To evaluate the technical feasibility and applicability of quantitative MR techniques (delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T2 mapping, T2* mapping) at 7 T MRI for assessing hip cartilage.

Methods

Hips of 11 healthy volunteers were examined at 7 T MRI with an 8-channel radiofrequency transmit/receive body coil using multi-echo sequences for T2 and T2* mapping and a dual flip angle gradient-echo sequence before (T1₀) and after intravenous contrast agent administration (T1_Gd; 0.2 mmol/kg Gd-DTPA^2? followed by 0.5 h of walking and 0.5 h of rest) for dGEMRIC. Relaxation times of cartilage were measured manually in 10 regions of interest. Pearson’s correlations between R1_delta?=?1/T1_Gd???1/T1₀ and T1_Gd and between T2 and T2* were calculated. Image quality and the delineation of acetabular and femoral cartilage in the relaxation time maps were evaluated using discrete rating scales.

Results

High correlations were found between R1_delta and T1_Gd and between T2 and T2* relaxation times (all p?<?0.01). All techniques delivered diagnostic image quality, with best delineation of femoral and acetabular cartilage in the T2* maps (mean 3.2 out of a maximum of 4 points).

Conclusions

T1, T2 and T2* mapping of hip cartilage with diagnostic image quality is feasible at 7 T. To perform dGEMRIC at 7 T, pre-contrast T1 mapping can be omitted.

Key Points

? dGEMRIC of hip cartilage with diagnostic image quality is feasible at 7 T. ? To perform dGEMRIC at 7 T, pre-contrast T1 mapping can be omitted. ? T2(*) mapping of hip cartilage with diagnostic image quality is feasible at 7 T. ? T2 and T2* relaxation times of cartilage were highly correlated at 7 T. ? Best delineation of femoral and acetabular cartilage was found in T2* maps.

     

Quantitative cartilage degeneration associated with spontaneous osteoarthritis in a guinea pig model

Purpose:

To determine (i) the feasibility and intra‐ and inter‐scan reproducibility of T_1ρ MRI in assessing cartilage degeneration in a guinea pig model with naturally occurring joint disease that closely mimics human osteoarthritis (OA), (ii) demonstrate the sensitivity of T_1ρ MRI in assessing the age dependent cartilage degeneration in OA progression as compared to histopathological changes.

Materials and Methods:

Duncan‐Hartley guinea pigs were obtained at various ages and maintained under an IACUC approved protocol. The left hind stifle joint was imaged using T_1ρ MRI on a 9.4 Tesla Varian horizontal 20 cm bore scanner using a custom surface coil. Reproducibility of T_1ρ MRI was assessed using 4‐month‐old guinea pigs (N = 3). Three age cohorts; 3 month (N = 8), 5 month (N = 6), and 9 month (N = 5), were used to determine the age‐dependent osteoarthritic changes as measured by T_1ρ MRI. Validation of age‐dependent cartilage degeneration was confirmed by histology and Safranin‐O staining.

Results:

T_1ρ values obtained in the cartilage of the stifle joint in guinea pigs were highly reproducible with an inter‐scan mean coefficient of variation (CV) of 6.57% and a maximum intra‐scan CV of 9.29%. Mean cartilage T_1ρ values in animals with late stage cartilage degeneration were 56.3–56.9 ms (5–9 month cohorts) were both significantly (P < 0.01) higher than that obtained from 3‐month‐old cohort (44 ms) demonstrating an age‐dependent variation. T_1ρ was shown to be significantly greater than T₂. T_1ρ dispersion was observed in this animal model for the first time showing an increase of 45% between 500 Hz and 1500 Hz spin‐locking frequency. Cartilage thickness measurements were calculated from single mid‐coronal histology sections from same animals used for T_1ρ MRI. Thickness calculations showed insignificant differences between 3‐ and 5‐month cohorts and was significantly decreased by 9 months of age (P < 0.01). A moderate correlation (R² = 0.45) existed between T_1ρ values and signal intensity of Safranin‐O stain.

Conclusion:

The data presented demonstrate that T_1ρ MRI is highly reproducible in this spontaneous model of OA and may serve as a noninvasive tool to characterize joint cartilage degeneration during OA. Age‐dependent changes, verified with histological measurements of proteoglycan loss, correlated with T_1ρ across different age groups. T_1ρ has adequate dynamic range and is sensitive to detect and track the progression of cartilage degeneration in the guinea pig model before gross anatomical changes such as cartilage thinning has occurred. This study presents a technological advancement that would permit longitudinal studies of evaluating disease‐modifying therapies useful for treating human OA. J. Magn. Reson. Imaging 2012;35:891–898. © 2011 Wiley Periodicals, Inc.     

Using the dGEMRIC technique to evaluate cartilage health in the presence of surgical hardware at 3T: comparison of inversion recovery and saturation recovery approaches

Objective

To evaluate the effect of metal artifact reduction techniques on dGEMRIC T₁ calculation with surgical hardware present.

Materials and methods

We examined the effect of stainless-steel and titanium hardware on dGEMRIC T₁ maps. We tested two strategies to reduce metal artifact in dGEMRIC: (1) saturation recovery (SR) instead of inversion recovery (IR) and (2) applying the metal artifact reduction sequence (MARS), in a gadolinium-doped agarose gel phantom and in vivo with titanium hardware. T₁ maps were obtained using custom curve-fitting software and phantom ROIs were defined to compare conditions (metal, MARS, IR, SR).

Results

A large area of artifact appeared in phantom IR images with metal when TI?≤?700 ms. IR maps with metal had additional artifact both in vivo and in the phantom (shifted null points, increased mean T₁ (+151 % IR ROI_artifact) and decreased mean inversion efficiency (f; 0.45 ROI_artifact, versus 2 for perfect inversion)) compared to the SR maps (ROI_artifact: +13 % T₁ SR, 0.95 versus 1 for perfect excitation), however, SR produced noisier T₁ maps than IR (phantom SNR: 118 SR, 212 IR). MARS subtly reduced the extent of artifact in the phantom (IR and SR).

Conclusions

dGEMRIC measurement in the presence of surgical hardware at 3T is possible with appropriately applied strategies. Measurements may work best in the presence of titanium and are severely limited with stainless steel. For regions near hardware where IR produces large artifacts making dGEMRIC analysis impossible, SR-MARS may allow dGEMRIC measurements. The position and size of the IR artifact is variable, and must be assessed for each implant/imaging set-up.     

Mid-term evaluation of the effects of dynamic neutralization system on lumbar intervertebral discs using quantitative molecular MR imaging

Purpose:

To evaluate the mid‐term effects of implant of dynamic neutralization system (Dynesys) on disc tissue in patients with lumbar discopathy, through the quantification of glycosaminoglycans (GAG) concentration, both in treated and adjacent levels, by analysis of delayed gadolinium‐enhanced MRI contrast (dGEMRIC) images.

Materials and Methods:

Ten patients with low back pain underwent the dGEMRIC diagnostic protocol before, 6‐months and after 2 years from surgery. Each patient was also evaluated with visual analog (VAS), Oswestry, and Prolo scales both at presurgery and during follow‐up. From dGEMRIC images, a ΔT1 parametric map was obtained for each disc, as quantitative indicator of its GAG concentration, and divided in 13 sectors, which were classified at presurgery as normal or abnormal, based on a 70‐ms threshold. Evolution of ΔT1 was studied during the follow‐up.

Results:

Nine of ten patients completed the follow‐up. VAS, Oswestry, and Prolo grades showed an improvement. This was accompanied by a reduction of ΔT1 in abnormal segments while normal segments showed a pattern of initial worsening at 6 months, followed by an improvement after 2 years.

Conclusion:

Our study confirmed the improvement in clinical evaluation, and for the first time related this to the changes in discs GAG concentration. J. Magn. Reson. Imaging 2012;35:1145‐1151. © 2011 Wiley Periodicals, 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.     

Hemodynamic analysis of bladder tumors using T1-dynamic contrast-enhanced fast spin-echo MRI

Objectives

To evaluate the hemodynamics of bladder tumors, we developed a method to calculate change in R₁ value (ΔR₁) from T₁-dynamic contrast-enhanced fast spin-echo magnetic resonance imaging (T₁DCE-FSE-MRI).

Materials and methods

On a 1.5-T MR system, T₁DCE-FSE-MRI was performed. This study was applied to 12 patients with urinary bladder tumor, i.e. urothelial carcinoma. We compared ΔR₁–time and ΔSI–time between a peak in the ΔR₁–time and ΔSI–time curve occurred during the first pass within 60 s. Next, we assessed the slope of increase for 180 s after CA injection (Slope_0–180).

Results

The mean slope of the first pass was significantly higher for bladder tumors on both the ΔR₁–time and the ΔSI–time curve compared with normal bladder walls. Moreover, a significant difference was apparent between bladder tumors and normal bladder walls on the mean Slope_0–180 in the ΔR₁-time curve. However, no significant difference in the mean Slope_0–180 was observed on the ΔSI-time curve between bladder tumors and normal bladder walls.

Conclusion

T₁DCE-FSE-MRI offers three advantages: quantitative analysis; high-quality (i.e., artifact-free) images; and high temporal resolution even for SE images. Use of ΔR₁ analysis with T₁DCE-FSE-MRI allows more detailed information on the hemodynamics of bladder tumors to be obtained and assists in differentiation between bladder tumors and the normal bladder wall.     

Division scheme optimization for the molecular evaluation of the intervertebral disc by gadolinium‐enhanced MRI

Purpose

To evaluate the effects of reducing the number of segments in which the intervertebral disc (IVD) can be subdivided on the accuracy in estimating its sGAG content by computation of the parameter ΔT1 from delayed Gadolinium‐Enhanced MRI of Cartilage (dGEMRIC) protocol.

Materials and Methods

Twenty‐three herniectomy patients underwent dGEMRIC acquisitions for IVD. Thirty‐one tissue samples were obtained at herniectomy from the same patients and biochemically analysed for their sGAG content. Eleven different division schemes (DS) were applied by processing dGEMRIC images, and ΔT1 values of the segments related to the surgical sampling locations were computed and correlated to the corresponding biochemical data. For each DS, the linear regression and Pearson's coefficient were computed.

Results

Reducing the number of segments from 48 (4 annular rings and 12 angular sectors) to 12 (2 rings and 6 sectors), correlation with sGAG biochemical data did not decline (r > 0.7).

Conclusion

A 12‐segment DS provided the best compromise between preserving accuracy and reducing the number of segments. J. Magn. Reson. Imaging 2009;29:1443–1449. © 2009 Wiley‐Liss, Inc.     

T(2) preparation method for measuring hyperemic myocardial O(2) consumption: in vivo validation by positron emission tomography

Purpose

To validate a new T₂‐prepared method for the quantification of regional myocardial O₂ consumption during pharmacologic stress with positron emission tomography (PET).

Materials and Methods

A T₂ prepared gradient‐echo sequence was modified to measure myocardial T₂ within a single breath‐hold. Six beagle dogs were randomly selected for the induction of coronary artery stenosis. Magnetic resonance imaging (MRI) experiments were performed with the T₂ imaging and first‐pass perfusion imaging at rest and during either dobutamine‐ or dipyridamole‐induced hyperemia. Myocardial blood flow (MBF) was quantified using a previously developed model‐free algorithm. Hyperemic myocardial O₂ extraction fraction (OEF) and consumption (MVO₂) were calculated using a two‐compartment model developed previously. PET imaging using ¹¹C‐acetate and ¹⁵O‐water was performed in the same day to validate OEF, MBF, and MVO₂ measurements.

Results

The T₂‐prepared mapping sequence measured regional myocardial T₂ with a repeatability of 2.3%. By myocardial segment‐basis analysis, MBF measured by MRI is closely correlated with that measured by PET (R² = 0.85, n = 22). Similar correlation coefficients were observed for hyperemic OEF (R² = 0.90, n = 9, mean difference of PET – MRI = ?2.4%) and MVO₂ (R² = 0.83, n = 7, mean difference = 4.2%).

Conclusion

The T₂‐prepared imaging method may allow quantitative estimation of regional myocardial oxygenation with relatively good accuracy. The precision of the method remains to be improved. J. Magn. Reson. Imaging 2011;33:320–327. © 2011 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.     

Multicompartmental analysis of late contrast enhancement in areas of myocardial infarction supplied by chronically occluded coronary arteries

Purpose

To analyze the relationship between late contrast enhancement (LCE) and the interstitial distribution volume (V_In) of gadolinium (Gd) tracers in the myocardial infarction (MI) areas supplied by chronically occluded arteries from patients. In animal experimental models, LCE has already been shown to correspond to an enhanced V_In of Gd tracers and thus, to a decrease in the amount of intact cells.

Materials and Methods

A multicompartmental analysis was applied to serial MRI images encompassing both infarct and remote areas and recorded with a conventional two‐dimensional (2D) segmented inversion‐recovery gradient‐echo (IR‐GRE) sequence during a 15‐minute period following Gd‐diethylenetriamine pentaacetic acid (Gd‐DTPA) injection in 12 patients with Q‐wave MI supplied by chronically occluded coronary arteries.

Results

V_In from infarct tissue was: 1) higher than V_In from remote areas (in % of myocardial volume: 74 ± 16% vs. 20 ± 7%, P < 0.001); and 2) correlated with the quantification of LCE between infarct and noninfarct areas at the 15th minute (R² = 0.63, P = 0.002). However, the difference in V_In between infarct and remote myocardium was a much better correlate of this quantified LCE (R² = 0.85, P < 0.001).

Conclusion

Detection of LCE in the MI territories supplied by chronically occluded arteries relates to the difference in the V_In of tracers between the infarct and the noninfarct areas. J. Magn. Reson. Imaging 2009;29:78–85. © 2008 Wiley‐Liss, Inc.