Falk Miese

Kidney Transplant: Functional Assessment with Diffusion-Tensor MR Imaging at 3T

PURPOSE To evaluate the feasibility of diffusion-tensor (DT) imaging at 3 T for functional assessment of transplanted kidneys. MATERIALS AND METHODS This study was approved by the local ethics committee; written informed consent was obtained. Between August 2009 and October 2010, 40 renal transplant recipients were prospectively included in this study and examined with a clinical 3-T magnetic resonance (MR) imager. An echo-planar DT imaging sequence was performed in coronal orientation by using five b values (0, 200, 400, 600, 800 sec/mm(2)) and 20 diffusion directions. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were determined for the cortex and medulla of the transplanted kidney. Relationships between FA, ADC, and allograft function, determined by the estimated glomerular filtration rate (eGFR), were assessed by using Pearson correlation coefficient. ADC and FA were compared between patients with good or moderate allograft function (group A; eGFR > 30 mL/min/1.73 m(2)) and patients with impaired function (group B; eGFR ≤ 30 mL/min/1.73 m(2)) by using a student t test. P < .05 indicated a statistically significant difference. RESULTS Mean FA of the renal medulla and cortex was significantly higher in group A (0.39 ± 0.06 and 0.17 ± 0.4) compared with group B (0.27 ± 0.05 and 0.14 ± 0.03) (P < .001 and P = .009, respectively). Mean ADCs of renal cortex and medulla were significantly higher in group A than in group B (P = .007 and P = .01, respectively). In group B, mean medullary FA was significantly lower in patients whose renal function did not recover (0.22 ± 0.02) compared with those with stable allograft function at 6 months (0.29 ± 0.05, P < .001). There was significant correlation between eGFR and medullary FA (r = 0.65, P < .001), cortical ADC (r = 0.43, P = .003), and medullary ADC (r = 0.35, P = .01). CONCLUSION DT imaging is a promising noninvasive technique for functional assessment of renal allografts. FA values in the renal medulla exhibit a good correlation with renal function.

Hybrid 18F-FDG PET-MRI of the hand in rheumatoid arthritis: initial results.

Abstract18F-fluorodeoxyglucose PET (18F-FDG PET) is highly sensitive to inflammatory changes within the synovial tissue in rheumatoid arthritis (RA). However, the highest spatial resolution for soft tissue can be achieved with MRI. Here, we report on the first true hybrid PET–MRI examination of the hand in early RA exploiting the advantages of both modalities. PET–MRI was performed with a prototype of an APD-based magneto-insensitive BrainPET detector (Siemens Healthcare, Erlangen, Germany) operated within a standard 3T MR scanner (MAGNETOM Trio, Siemens). PET images were normalized, random, attenuation and scatter-corrected, iteratively reconstructed and calibrated to yield standardized uptake values (SUV) of 18F-FDG uptake. T1-weighted TSE in coronal as well as sagittal orientation prior to and following Gadolinium administration were acquired. Increased 18F-FDG uptake was present in synovitis and tenovaginitis as identified on contrast-enhanced MRI. The tracer distribution was surrounding the metacarpophalangeal joints II and III. Maximum SUV of 3.1 was noted. In RA, true hybrid 18F-FDG PET–MRI of the hand is technically feasible and bears the potential to directly visualize inflammation.

Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), after slipped capital femoral epiphysis

OBJECTIVE The aim of this study was to assess the glycosaminoglycan (GAG) content in hip joint cartilage in mature hips with a history of slipped capital femoral epiphysis (SCFE) using delayed gadolinium-enhanced MRI of cartilage (dGEMRIC). METHODS 28 young-adult subjects (32 hips) with a mean age of 23.8 ± 4.0 years (range: 18.1-30.5 years) who were treated for mild or moderate SCFE in adolescence were included into the study. Hip function and clinical symptoms were evaluated with the Harris hip score (HHS) system at the time of MRI. Plain radiographic evaluation included Tonnis grading, measurement of the minimal joint space width (JSW) and alpha-angle measurement. The alpha-angle values were used to classify three sub-groups: group 1=subjects with normal femoral head-neck offset (alpha-angle <50°), group 2=subjects with mild offset decrease (alpha-angle 50°-60°), and group 3=subjects with severe offset decrease (alpha-angle >60°). RESULTS There was statistically significant difference noted for the T1(Gd) values, lateral and central, between group 1 and group 3 (p-values=0.038 and 0.041). The T1(Gd) values measured within the lateral portion were slightly lower compared with the T1(Gd) values measured within the central portion that was at a statistically significance level (p-value <0.001). HHS, Tonnis grades and JSW revealed no statistically significant difference. CONCLUSION By using dGEMRIC in the mid-term follow-up of SCFE we were able to reveal degenerative changes even in the absence of joint space narrowing that seem to be related to the degree of offset pathology. The dGEMRIC technique may be a potential diagnostic modality in the follow-up evaluation of SCFE.

T2* mapping of acetabular and femoral hip joint cartilage at 3 T: a prospective controlled study.

ObjectivesThe aim of this study was to identify the pattern of T2* values in acetabular and femoral head cartilage in morphologically normal and abnormal zones at 3 T. Materials and MethodsTwenty-nine patients (mean [SD] age, 30.8 [8.8] years) with symptomatic femoroacetabular impingement and suspected cartilage damage (study group) and 35 healthy, asymptomatic volunteers (mean [SD] age, 24.9 [2.1] years) with no obvious history of hip diseases or abnormalities (control group) were included. Magnetic resonance imaging was performed at 3 T using a 3-dimensional (3D) double-echo steady-state sequence for grading cartilage morphologically and a 3D multiecho data image combination sequence for T2* assessment. Statistical assessment included the Student t test to reveal differences between mean T2* values of the study group and the control group. One-way analysis of variance was used to identify any statistically significant differences between the T2* values in various grades (modified Outerbridge score system) of cartilage damage within the study group. ResultsSignificant differences were noted between the T2* values in the study group and the control group (P < 0.001). We also noted a significant drop in T2* in accordance with the morphologic damage in the study group (P < 0.001). The largest drop in T2* was found between morphologically normal-appearing cartilage (grade 0; T2*, 25.2 milliseconds) and grade I changes (T2*, 18.1 milliseconds) (P < 0.001). ConclusionsIn combination with a 3-T system, T2* mapping offers unique advantages such as high image resolution and the ability of 3D biochemically sensitive cartilage evaluation in the hip joint without the need for contrast medium. Given these advantages, we believe that T2* mapping is another welcome addition to the rapidly evolving era of hip cartilage biochemical imaging. Further studies are necessary that involve a diagnostic histological analysis as gold standard for comparison.

Molecular imaging of cartilage damage of finger joints in early rheumatoid arthritis with delayed gadolinium-enhanced magnetic resonance imaging.

OBJECTIVE To assess cartilage glycosaminoglycan content and cartilage thickness in the metacarpophalangeal (MCP) joints of patients with early rheumatoid arthritis (RA) and healthy volunteers. METHODS After review board approval and informed consent were obtained, 22 subjects were prospectively enrolled (9 patients with early RA [7 women and 2 men with a mean ± SD age of 49 ± 13 years; range 25-68 years] and 13 healthy volunteers [10 women and 3 men with a mean ± SD age of 51 ± 12 years; range 25-66 years). In a total of 44 MCP joints of the index and middle fingers, measurements of cartilage thickness and delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) index (T1 [msec]) were obtained using the variable flip-angle method and a 3T MR scanner. MRIs were evaluated for bone edema, erosions, and synovitis (using the RA MRI Scoring criteria). Students t-test was used to test the significance of differences between groups. RESULTS The mean ± SD dGEMRIC index was 497 ± 86 msec in healthy volunteers and was significantly lower in the early RA group (421 ± 76 msec) (P = 0.042). There was no joint space narrowing seen on standard radiographs. No significant difference was found between cartilage thickness in patients with early RA and that in controls (index finger mean ± SD 1.27 ± 0.23 mm in RA patients versus 1.46 ± 0.34 mm in controls [P = 0.16] and middle finger 1.26 ± 0.23 mm in RA patients versus 0.97 ± 0.47 mm in controls [P = 0.10]). No significant correlation was noted between cartilage thickness and dGEMRIC index (R = 0.36, P = 0.88 in RA patients; R = 0.156, P = 0.445 in controls). CONCLUSION Our findings indicate that cartilage damage is present in the MCP joints of patients with early RA despite the absence of joint space narrowing on standard radiographs and MRI. Cartilage damage in RA can be imaged with dGEMRIC.

Three-dimensional delayed gadolinium-enhanced magnetic resonance imaging of hip joint cartilage at 3 T: 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 T1Gd assessment was performed in seven regions in the hip joint, including anterior to superior and posterior regions. RESULTS T1Gd mapping demonstrated the typical pattern of acetabular cartilage consistent with a higher glycosaminoglycan (GAG) content in the main weight-bearing area. T1Gd values were significantly higher in the control group than in the patient group whereas significant differences in T1Gd 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.

Delayed gadolinium-enhanced magnetic resonance imaging of cartilage in the long-term follow-up after Perthes disease.

Background Aim of this study was to assess the glycosaminoglycan content in hip joint cartilage in mature hips with a history of Legg-Calvé-Perthes (LCPD) disease using delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC). Methods Thirty one hips in 27 adults (mean age: 30.5±10.9 y) with LCPD in childhood were included. Mean follow-up after diagnosis was 24.5±11.4 years. Clinical symptoms and standard radiographic parameters were evaluated. dGEMRIC indices were calculated as T1Gd mean values in four coronal MRI slices medially, centrally, and laterally. For comparison, the morphologically normal appearing contra-lateral hips (21 hips) were assessed. Results The following T1Gd values for the LCPD group were noted: medial (507±100 ms), central (543±104 ms), and lateral (553±105 ms). The total T1Gd mean value was 534±104 ms. The difference between LCPD and normal hips was statistically significant only for the medial compartment (P=0.018). Conclusions Hip joint cartilage after LCPD shows a significant glycosaminoglycan loss in the medial compartment while this decrease is less apparent centrally and laterally. dGEMRIC allows direct assessment of cartilage matrix biochemistry and may depict the complex damage pattern of hip joint cartilage after LCPD spatially and qualitatively better than other radiographic methods. Level of Evidence Prognostic study, Level II-1 (retrospective study).

Prospectively Ecg-triggered High-pitch Spiral Acquisition for Cardiac Ct Angiography in Routine Clinical Practice: Initial Results

Purpose: This study was conducted to evaluate the mode of application, image quality (IQ), and radiation exposure resulting from introduction of a prospectively electrocardiogram-triggered high-pitch cardiac computed tomography angiography (CTA) acquisition mode into routine clinical practice. Materials and Methods: A total of 42 prospectively triggered cardiac CTAs were conducted on 34 patients (11 female, 23 male; mean age 56±15 y) using a high-pitch mode (pitch 3.4) on a dual-source CT. In 8 of these patients with higher heart rates or occasional premature ventricular contractions, 2 immediately subsequent CTAs were performed (“double flash protocol”). Subjective IQ was assessed for coronary arteries using a 4-point scale (1=unevaluable to 4=excellent). Contrast-to-noise ratio (CNR) was measured in 9 locations. CT Dose Index and dose-length product were obtained, and the patients’ effective dose was calculated. Results: Mean effective doses were 2.6±1.4 mSv (range: 1.1 to 6.4) for the entire cardiac examination and 1.4±0.7 mSv (0.4 to 3.1) for individual high-pitch cardiac CTA. z-coverage ranged from 9.9 cm in a native coronary CTA to 31.4 cm in a bypass graft case. The overall subjective IQ was good to excellent (mean score: 3.5), with 1.5% unevaluable coronary segments. The “double flash protocol” resulted in a fully diagnostic CT study in all cases just after taking both scans into consideration. The mean CNR of all locations was 19.7±2.6. Conclusion: Prospectively electrocardiograph-triggered high-pitch-mode cardiac CTA is a feasible and promising technique in clinical routine, allowing for evaluation of coronaries at good-to-excellent IQ and providing high CNR and minimal radiation doses. The “double flash protocol” might become a more robust tool in patients with elevated heart rates or premature ventricular contractions.

Diffusion-Attenuated MRI Signal of Renal Allografts: Comparison of Two Different Statistical Models

OBJECTIVE Contrast-enhanced MRI is considered problematic in renal allograft recipients because of the development of nephrogenic systemic fibrosis. Therefore, we assessed the clinical value of a monoexponential model and a distribution function model of diffusion-weighted imaging (DWI) in renal allografts. MATERIALS AND METHODS A total of 23 patients were divided into three groups, as follows: group A, stable renal allograft function for at least 6 months; group B, transplantation within the past 30 days, with good renal allograft function; and group C, an acute deterioration or decrease in renal allograft function. T2-weighted axial, T1-weighted coronal, and a paracoronal DWI sequences with 16 b values (b = 0-750 s/mm(2)) were performed on a 1.5-T scanner. Region of interest-based analysis of the apparent diffusion coefficient (ADC) of the renal cortex was used. RESULTS Monoexponential analysis showed mean (± SD) ADC values of 1932 ± 98, 2095 ± 246, and 1636 ± 200 10-(6) mm(2)/s for patient groups A, B, and C, respectively. The distribution function revealed a mean ADC of 2487 ± 185, 2850 ± 325, and 2142 ± 31410-(6) mm(2)/s for groups A, B, and C, respectively. The difference between groups A and B combined and group C (p < 0.005) was statistically significant for both models. R(2) yielded the best regression of mathematic fitting for the distribution function model (p < 0.0001). DISCUSSION Unenhanced evaluation of renal allografts with DWI correlated well with renal function for both the monoexponential analysis and the distribution function model. There was no statistically significant difference in ADC values and renal allograft function between both types of analysis, but the distribution function showed the best regression.

Metacarpophalangeal Joints in Rheumatoid Arthritis: Delayed Gadolinium-enhanced MR Imaging of Cartilage—A Feasibility Study

PURPOSE To evaluate the feasibility of delayed gadolinium-enhanced magnetic resonance (MR) imaging of the cartilage of metacarpophalangeal (MCP) joints in patients with rheumatoid arthritis (RA) compared with that in control subjects. MATERIALS AND METHODS Institutional review board approval and informed consent were obtained. Thirty-one MCP joints in 10 patients with RA (mean age, 59 years; range, 35-77 years) and six healthy volunteers (mean age, 51 years; range, 30-71 years) were examined with delayed gadolinium-enhanced MR imaging of cartilage. Sagittal images of the second and third MCP joints (hereafter, MCP II and MCP III) were acquired with a three-dimensional dual-flip-angle gradient-echo sequence at 3.0 T. B(1) field inhomogeneity-corrected T1 maps were calculated, and delayed gadolinium-enhanced MR imaging of cartilage values for phalangeal and metacarpal cartilage were determined. In addition, cartilage thickness was measured. A nonparametric Mann-Whitney U test was used to assess differences between groups. RESULTS Phalangeal and metacarpal delayed gadolinium-enhanced MR imaging of cartilage values in patients with RA (MCP II: 388 msec ± 105 [standard deviation] and 342 msec ± 79, respectively; MCP III: 409 msec ± 96 and 371 msec ± 89, respectively) were significantly lower than in control subjects (MCP II: 598 msec ± 62 and 560 msec ± 51, respectively; MCP III: 586 msec ± 57 and 561 msec ± 80, respectively). Cartilage thickness of both joints was comparable in patients with RA (MCP II: 1.28 mm ± 0.50, MCP III: 1.17 mm ± 0.24) and control subjects (MCP II: 1.42 mm ± 0.33, MCP III: 1.18 mm ± 0.26). CONCLUSION Delayed gadolinium-enhanced MR imaging of cartilage of the MCP joints is feasible at 3.0 T. Delayed gadolinium-enhanced MR imaging of cartilage may help to assess cartilage degeneration in morphologically normal-appearing MCP II and III cartilage in patients with RA.