Evaluation of right ventricular function with multidetector computed tomography: comparison with magnetic resonance imaging and analysis of inter- and intraobserver variability

This study was performed to prospectively compare multidetector computed tomography (MDCT) with 16 simultaneous sections and magnetic resonance imaging (MRI) for the assessment of global right ventricular function in 50 patients. MDCT using a semiautomatic analysis tool showed good correlation with MRI for end-diastolic volume (EDV, r = 0.83, p < 0.001), end-systolic volume (ESV, r = 0.86, p < 0.001) and stroke volume (SV, r = 0.74, p < 0.001), but only a moderate correlation for the ejection fraction (EF, r = 0.67, p < 0.001). Bland Altman analysis revealed a slight, but insignificant overestimation of EDV (4.0 ml, p = 0.08) and ESV (2.4 ml, p = 0.07), and underestimation of EF (0.1%, p = 0.92) with MDCT compared with MRI. All limits of agreement between both modalities (EF: ±15.7%, EDV: ±31.0 ml, ESV: ±18.0 ml) were in a moderate but acceptable range. Interobserver variability of MDCT was not significantly different from that of MRI. For MDCT software, the post-processing time was significantly longer (19.6 ± 5.8 min) than for MRI (11.8 ± 2.6 min, p < 0.001). Accurate assessment of right ventricular volumes by 16-detector CT is feasible but still rather time-consuming.     

Evaluation of pituitary macroadenomas with multidetector-row CT (MDCT): comparison with MR imaging

Introduction It is important to have information on cavernous sinus extension and bony destruction in pituitary macroadenomas before surgery, but magnetic resonance (MR) imaging cannot always depict them. In the present study we sought to determine whether multidetector-row computed tomography (MDCT) could provide preoperative information in addition to that provided by MR imaging in pituitary macroadenoma. Methods The subjects comprised 33 consecutive patients (15 women, 18 men; mean age 50 years) with surgically proven macroadenoma. For MDCT, using the soft-tissue window and bone window, three orthogonal multiplanar reconstruction images were generated from venous-phase contrast-enhanced 0.5-mm isotropic voxel data. MDCT and MR images were evaluated with regard to: (1) clarity of tumor margins; (2) identification of the normal pituitary gland; (3) identification of erosion or destruction of the sellar floor; and (4) visualization of the adjacent optic pathways. Results MDCT more clearly demonstrated the lateral tumor margin than MR imaging (P = 0.002). No significant differences in visualization of the normal pituitary gland were noted between MDCT and dynamic MR imaging (P = 0.7). MDCT more clearly demonstrated sellar floor erosion or destruction at the sphenoid sinus than MR imaging (P < 0.001). MR imaging was superior to MDCT for visualizing the adjacent optic pathways (P < 0.001). Conclusion MDCT is superior to MR imaging for assessing lateral tumor margin and the sellar floor at the sphenoid sinus. MDCT offers useful preoperative information in addition to that obtained from MR imaging. Y.M. and M.K. contributed equally to this study.     

MR elastography of liver fibrosis: preliminary results comparing spin-echo and echo-planar imaging

The purpose of this study was to prospectively compare the performance of magnetic resonance (MR) elastography using echo-planar and spin-echo imaging for staging of hepatic fibrosis. Twenty-four patients who had liver biopsy for suspicion of chronic liver disease had MR elastography performed with both spin-echo and echo-planar sequences. At histology, the fibrosis stage was assessed according to METAVIR. The data acquisition time was about 20 min using spin-echo, and only 2 min using echo-planar imaging. The hepatic signal-to-noise ratios were similar on both images (22.51 ± 5.37 for spin-echo versus 21.02 ± 4.76 for echo-planar, p = 0.33). The elasticity measurements and the fibrosis stages were strongly correlated. The Spearman correlation coefficients were r = 0.91 (p < 0.01) with spin-echo and r = 0.84 (p < 0.01) with echo-planar sequences. These correlation coefficients did not differ significantly (p = 0.17). A strong correlation was also observed between spin-echo and echo-planar elasticity (r = 0.83, p < 0.001), without systematic bias. The results of our study showed that echo-planar imaging substantially decreased the data acquisition time of MR elastography, while maintaining the image quality and diagnostic performance for staging of liver fibrosis. This suggests that echo-planar MR elastography could replace spin-echo MR elastography in clinical practice. This work was supported by grants FRSM 3.4578.00 and 3.4580.06 from the Fonds National de la Recherche Scientifique, Belgium.     

Accurate estimation of global and regional cardiac function by retrospectively gated multidetector row computed tomography

Retrospective reconstruction of ECG-gated images at different parts of the cardiac cycle allows the assessment of cardiac function by multi-detector row CT (MDCT) at the time of non-invasive coronary imaging. We compared the accuracy of such measurements by MDCT to cine magnetic resonance (MR). Forty patients underwent the assessment of global and regional cardiac function by 16-slice MDCT and cine MR. Left ventricular (LV) end-diastolic and end-systolic volumes estimated by MDCT (134±51 and 67±56 ml) were similar to those by MR (137±57 and 70±60 ml, respectively; both P=NS) and strongly correlated (r=0.92 and r=0.95, respectively; both P<0.001). Consequently, LV ejection fractions by MDCT and MR were also similar (55±21 vs. 56±21%; P=NS) and highly correlated (r=0.95; P<0.001). Regional end-diastolic and end-systolic wall thicknesses by MDCT were highly correlated (r=0.84 and r=0.92, respectively; both P<0.001), but significantly lower than by MR (8.3±1.8 vs. 8.8±1.9 mm and 12.7±3.4 vs. 13.3±3.5 mm, respectively; both P<0.001). Values of regional wall thickening by MDCT and MR were similar (54±30 vs. 51±31%; P=NS) and also correlated well (r=0.91; P<0.001). Retrospectively gated MDCT can accurately estimate LV volumes, EF and regional LV wall thickening compared to cine MR. Grant funding: Dr. Belge was supported by a fellowship of the Fondation Nationale de la Recherche Scientifique of the Belgian government. Dr. Gerber was supported by a grant from the Fondation Nationale de la Recherche Scientifique of the Belgian government (FRSM 3.4557.02).     

Variability of bronchial measurements obtained by sequential CT using two computer-based methods

This study aimed to evaluate the variability of lumen (LA) and wall area (WA) measurements obtained on two successive MDCT acquisitions using energy-driven contour estimation (EDCE) and full width at half maximum (FWHM) approaches. Both methods were applied to a database of segmental and subsegmental bronchi with LA > 4 mm² containing 42 bronchial segments of 10 successive slices that best matched on each acquisition. For both methods, the 95% confidence interval between repeated MDCT was between –1.59 and 1.5 mm² for LA, and –3.31 and 2.96 mm² for WA. The values of the coefficient of measurement variation (CV₁₀, i.e., percentage ratio of the standard deviation obtained from the 10 successive slices to their mean value) were strongly correlated between repeated MDCT data acquisitions (r > 0.72; p < 0.0001). Compared with FWHM, LA values obtained using EDCE were higher for LA < 15 mm², whereas WA values were lower for bronchi with WA < 13 mm²; no systematic EDCE underestimation or overestimation was observed for thicker-walled bronchi. In conclusion, variability between CT examinations and assessment techniques may impair measurements. Therefore, new parameters such as CV₁₀ need to be investigated to study bronchial remodeling. Finally, EDCE and FWHM are not interchangeable in longitudinal studies.     

Optimization of b value in diffusion-weighted MRI for the differential diagnosis of benign and malignant vertebral fractures

Objective The objective was to explore the optimal b value in diffusion-weighted imaging (DWI) of MRI for differential diagnosis of benign and malignant vertebral fractures. Materials and Methods Thirty-four consecutive patients with vertebral compression fractures underwent sagittal diffusion-weighted imaging (DWI) with different b values. The group included 14 patients with 18 benign vertebral fractures due to osteoporosis and/or trauma and 20 patients with 27 malignant vertebral fractures due to malignancy. The quality of the images was analyzed qualitatively on a three-point scale and quantitatively by measurement of the signal-to-noise ratio (SNR). Apparent diffusion coefficient (ADC) values were also calculated. Results Smaller b values correlated with better DW image quality. We found significant differences in the qualitative points values among the DW images with different b values (F = 302.18, p < 0.001). The mean SNR of the images ranged from 21.75 ± 3.64 at a b value of 0 s/mm² to 5.31 ± 3.17 at a b value of 800 s/mm². The SNR of DWI with a b value of 300 s/mm² (18.62 ± 2.47) was significantly different from that with other b values (p < 0.01). The mean combined ADC values of malignant fractures were significantly lower than those of benign ones on DWI with a b value of 300 s/mm² (t = 9.097, p < 0.01). Four cases of benign vertebral fractures were misdiagnosed as being malignant when b values of 0 s/mm² and 100 s/mm² were used. Conclusions When DWI with multiple b values is used to differentiate benign from malignant vertebral compression fractures, b values within the range of around 300 s/mm² are recommended, taking into account both SNR and diffusion weighting of water molecules.     

Quantification of Left Ventricular Parameters Obtained by Automated Software for 64-Slice Multidetector Computed Tomography and Comparison with Magnetic Resonance Imaging

The dataset obtained with 64-slice multidetector CT (MDCT) for coronary artery evaluation can be used to calculate important left ventricular (LV) volumetric parameters. We compared LV parameters derived by new, commercially available, fully automated software for MDCT (Syngo Circulation, Siemens, Germany) to cardiac magnetic resonance (CMR) as a reference standard. Twenty patients underwent CMR after completing a clinically indicated MDCT. Ejection fraction (EF), end-systolic volume (ESV), end-diastolic volume (EDV), stroke volume (SV), and myocardial mass (MM) for MDCT were obtained using automated software and were compared to CMR measurements, with papillary muscles (PMs) included in, or excluded from, the blood pool. The Pearson correlation coefficient (r) and Bland-Altman method were used to determine agreement between methods. When PMs were included in the blood pool, the correlation was excellent for EF (r = 0.92, p < 0.001), ESV (r = 0.86, p < 0.001), and EDV (r = 0.80, p < 0.001). When PMs were excluded from CMR, correlation was still very good for EF (r = 0.89, p < 0.001), ESV (r = 0.82, p < 0.001), and EDV (r = 0.82, p < 0.001). MDCT values for SV and MM showed a good correlation compared to both CMR methods. When PMs were included, the correlation was good for SV (r = 0.70, p < 0.001), and MM (r = 0.70, p < 0.001); when they were excluded, the correlation was less robust but still significant for SV (r = 0.71, p < 0.001) and MM (r = 0.73, p < 0.001). In conclusion, EF, ESV, and EDV obtained by MDCT using simple, automated software correlated very well with CMR; SV and MM showed good correlation. Automated analysis of volumetric parameters by MDCT can be reliably utilized for clinical purposes.     

Assessment of intra- and interobserver reproducibility of rest and cold pressor test-stimulated myocardial blood flow with <Superscript>13</Superscript>N-ammonia and PET

Purpose We investigated the intraobserver reproducibility of myocardial blood flow (MBF) measurements with PET at rest and during cold pressor test (CPT), and the interobserver agreement. Methods Twenty normal volunteers were studied. Using ¹³N-ammonia, MBF was measured at rest and during CPT and measurement was repeated in a 1-day session (short-term reproducibility; SR). After a follow-up of 2 weeks, MBF was measured again at rest and during CPT and compared with the initial baseline measurement (long-term reproducibility; LR). In addition, adenosine-induced hyperemic MBF increases were assessed. Results Assessment of the SR did not show a significant absolute difference in MBF at rest, MBF during CPT or the endothelium-related change in MBF from rest to CPT (ΔMBF) (0.09 ± 0.10, 0.11 ± 0.09, and 0.08 ± 0.05 ml/g/min; p = NS), and they were linearly correlated (r = 0.72, r = 0.76 and r = 0.84; p < 0.0001). Corresponding values for standard error of the estimate (SEE), as indicative for the range of MBF measurement error, were 0.14, 0.14, and 0.09 ml/g/min. The LR yielded relatively higher but non-significant absolute differences in the MBF at rest, MBF during CPT and ΔMBF (0.10 ± 0.10, 0.14 ± 0.10, and 0.19 ± 0.10 ml/g/min; p = NS), and paired MBFs significantly correlated (r = 0.75, r = 0.71, and r = 0.60; p < 0.001). Corresponding SEEs were 0.13, 0.15, and 0.16 ml/g/min. The interobserver analysis yielded a high correlation for MBF at rest, MBF during CPT, and hyperemic MBF (r = 0.96, SEE=0.04; r = 0.78, SEE=0.11; and r = 0.87, SEE=0.28; p < 0.0001, respectively), and also a good interobserver correlation for ΔMBF (r = 0.62, SEE=0.09; p < 0.003). Conclusion Short- and long-term MBF responses to CPT, as an index for endothelium-related coronary vasomotion, can be measured reproducibly with ¹³N-ammonia PET. In addition, the high interobserver reproducibility for repeat analysis of MBF values suggests the measurements to be largely operator independent. Thomas H. Schindler and Xiao-Li Zhang contributed equally to this paper.     

Planimetric Measurement of the Regurgitant Orifice Area Using Multidetector CT for Aortic Regurgitation: a Comparison with the Use of Echocardiography

Objective

This study compared the area of the regurgitant orifice, as measured by the use of multidetector-row CT (MDCT), with the severity of aortic regurgitation (AR) as determined by the use of echocardiography for AR.

Materials and Methods

In this study, 45 AR patients underwent electrocardiography-gated 40-slice or 64-slice MDCT and transthoracic or transesophageal echocardiography. We reconstructed CT data sets during mid-systolic to enddiastolic phases in 10% steps (20% and 35-95% of the R-R interval), planimetrically measuring the abnormally opened aortic valve area during diastole on CT reformatted images and comparing the area of the aortic regurgitant orifice (ARO) so measured with the severity of AR, as determined by echocardiography.

Results

In the 14 patients found to have mild AR, the ARO area was 0.18±0.13 cm² (range, 0.04-0.54 cm²). In the 15 moderate AR patients, the ARO area was 0.36 ± 0.23 cm² (range, 0.09-0.81 cm²). In the 16 severe AR patients, the ARO area was 1.00 ± 0.51 cm² (range, 0.23-1.84 cm²). Receiver-operator characteristic curve analysis determined a sensitivity of 85% and a specificity of 82%, for a cutoff of 0.47 cm², to distinguish severe AR from less than severe AR with the use of CT (area under the curve = 0.91; 95% confidence interval, 0.84-1.00; p < 0.001).

Conclusion

Planimetric measurement of the ARO area using MDCT is useful for the quantitative evaluation of the severity of aortic regurgitation.     

Whole-body CT in polytrauma patients: effect of arm positioning on thoracic and abdominal image quality

The purpose of this study is to assess the influence of different arm positioning techniques on thoracic and abdominal image quality and radiation dose of whole-body trauma CT (wbCT). One hundred and fifty polytrauma patients (104 male, mean age 47 ± 19) underwent wbCT with arms elevated above the head (group A, n = 50), alongside the abdomen (group B, n = 50), and on a pillow ventrally to the chest with both arms flexed (group C, n = 50). Two blinded, independent observers measured image noise and rated image quality (scores 1–3) of the liver, aorta, spleen, spine, and lower lungs. Radiation dose parameters were noted, and the abdomens’ anterior–posterior diameter and scan lengths were measured. Interreader agreements for image noise (r = 0.86; p < 0.001) and subjective image quality (k = 0.71–0.84) were good. Noise was lower (p < 0.05), image quality of the liver, aorta, spleen, and spine was higher, and radiation dose lower in group A than in groups B and C (p < 0.001, each). Image quality of the spleen, liver, and aorta were higher in group C than in group B (p < 0.05, each). No significant differences in scan length (p = 0.61) were found among groups. Abdominal anterior–posterior diameter correlated significantly with noise (r = 0.82; p < 0.01) and dose (r = 0.47; p < 0.001). Estimated effective radiation doses were significantly (p < 0.001) higher in groups B (21.2 mSv) and C (21.9 mSv) as compared to A (16.1 mSv). In wbCT for polytrauma patients, positioning of the arms above the head results in better image quality and lower radiation dose. Placing the flexed arms on a large pillow ventrally to the chest significantly improves image quality as compared to positioning alongside the abdomen.     

Variations in 123I-metaiodobenzylguanidine (MIBG) late heart mediastinal ratios in chronic heart failure: a need for standardisation and validation

Background There is lack of validation and standardisation of acquisition parameters for myocardial ¹²³I-metaiodobenzylguanidine (MIBG). This lack of standardisation hampers large scale implementation of ¹²³I-MIBG parameters in the evaluation of patients with chronic heart failure (CHF). Methods In a retrospective multi-centre study ¹²³I-MIBG planar scintigrams obtained on 290 CHF patients (82% male; 58% dilated cardiomyopathy; New York Heart Association [NYHA classification] > I) were reanalysed to determine the late heart-to-mediastinum ratio (H/M). Results There was a large variation in acquisition parameters. Multivariate forward stepwise regression showed that a significant proportion (31%, p < 0.001) of the variation in late H/M could be explained by a model containing patient-related variables and acquisition parameters. Left ventricular ejection fraction (p < 0.001), type of collimation (p < 0.001), acquisition duration (p = 0.001), NYHA class (p = 0.028) and age (p = 0.034) were independent predictors of late H/M. Conclusions Acquisitions parameters are independent contributors to the variation of semi-quantitative measurements of cardiac ¹²³I-MIBG uptake. Improved standardisation of cardiac ¹²³I-MIBG imaging parameters would contribute to increased clinical applicability for this procedure.     

Characterization of pediatric head and neck masses with diffusion-weighted MR imaging

We aimed to assess the clinical usefulness of the ADCs calculated from diffusion-weighted echo-planar MR images in the characterization of pediatric head and neck masses. This study included 78 pediatric patients (46 boys and 32 girls aged 3 months–15 years, mean 6 years) with head and neck mass. Routine MR imaging and diffusion-weighted MR imaging were done on a 1.5-T MR unit using a single-shot echo-planar imaging (EPI) with a b factor of 0.500 and 1,000 s mm⁻². The ADC value was calculated. The mean ADC values of the malignant tumours, benign solid masses and cystic lesions were (0.93 ± 0.18) × 10⁻³, (1.57 ± 0.26) × 10^–3 and (2.01 ± 0.21 )× 10^–3 mm² s⁻¹, respectively. The difference in ADC value between the malignant tumours and benign lesions was statistically significant (p < 0.001). When an apparent diffusion coefficient value of 1.25 × 10^–3 mm² s⁻¹ was used as a threshold value for differentiating malignant from benign head and neck mass, the best results were obtained with an accuracy of 92.8%, sensitivity of 94.4%, specificity of 91.2%, positive predictive value of 91% and negative predictive value of 94.2%. Diffusion-weighted MR imaging is a new promising imaging approach that can be used for characterization of pediatric head and neck mass.     

Intraindividual comparison of myocardial delayed enhancement MR imaging using gadobenate dimeglumine at 1.5 T and 3 T

For contrast-enhanced imaging techniques relying on strong T1 weighting, 3 T provides increased contrast compared with 1.5 T. The aim of our study was the intraindividual comparison of delayed enhancement MR imaging at 1.5 T and at 3 T. Twenty patients with myocardial infarction were examined at 1.5 T and 3 T. Fifteen minutes after injection of contrast agent (0.1 mmol gadobenate dimeglumine per kg body weight), inversion recovery gradient recalled echo (IR-GRE) sequences were acquired (1.5 T/3 T: TR 11.0/9.9 ms, TE 4.4/4.9 ms, flip 30°/30°, slice thickness 6/6 mm) to assess myocardial viability. Two observers rated image quality (Wilcoxon signed rank test). Quantification of hyperenhanced myocardium and standardized SNR/CNR measurements were performed (Student’s t test). There was no significant difference with respect to image quality (1.5 T/3 T: 3.5/3.3, p = 0.34, reader 1; 2.4/2.7, p = 0.12, reader 2) and infarction size (760 ± 566/828 ± 677 mm² at 1.5 T, 808 ± 639/826 ± 726 mm² at 3 T, reader 1/reader 2, p > 0.05). Mean SNR in hyperenhanced/normal myocardium was 19.2/6.2 at 1.5 T and 29.5/8.8 at 3 T (p < 0.05). Mean CNR was 14.3 at 1.5 T and 26.0 at 3 T (p < 0.05). Delayed enhancement MR imaging at 3 T is a robust procedure yielding superior tissue contrast at 3 T compared with 1.5 T which is, however, not reflected by increased image quality.     

Bone marrow changes in beta-thalassemia major: quantitative MR imaging findings and correlation with iron stores

The purpose of this study is to describe the MR imaging features of bone marrow in beta-thalassemia major and investigate their relation to ferritin, liver and spleen siderosis. Spinal bone marrow was prospectively assessed on abdominal MR studies of 40 transfused beta-thalassemic patients and 15 controls using T1-w, Pd, T2*-w Gradient Echo (GRE) and T1-w turbo Spin Echo (TSE) sequences. Signal intensity (SI) ratios of liver, spleen and bone marrow to paraspinous muscles (L/M, S/M, B/M respectively) and the respective T2 relaxation rates (1/T2) were calculated. Serum ferritin levels were recorded. Bone marrow hypointensity in at least T2*-w GRE sequence was noted in 29/40 (72.5%) patients. Eleven/40 patients exhibited normal B/M on all MR sequences. Five/40 patients had normal B/M and low L/M. B/M correlated with L/M in T1-w TSE sequence only (r = 0.471, p = 0.05). B/M correlated with S/M and mean ferritin values in all sequences (r > 0.489, p < 0.01 and r  >  − 0.496, p < 0.03 respectively). Marrow 1/T2 did not correlate with ferritin values or liver and spleen 1/T2. B/M in transfused beta-thalassemic patients is related to splenic siderosis and ferritin levels. Although marrow is usually hypointense, it may occasionally display normal SI coexisting with liver hypointensity, a pattern typical of primary hemochromatosis.     

Evaluation and comparison of cartilage repair tissue of the patella and medial femoral condyle by using morphological MRI and biochemical zonal T2 mapping

The objective of this study was to use advanced MR techniques to evaluate and compare cartilage repair tissue after matrix-associated autologous chondrocyte transplantation (MACT) in the patella and medial femoral condyle (MFC). Thirty-four patients treated with MACT underwent 3-T MRI of the knee. Patients were treated on either patella (n = 17) or MFC (n = 17) cartilage and were matched by age and postoperative interval. For morphological evaluation, the MR observation of cartilage repair tissue (MOCART) score was used, with a 3D-True-FISP sequence. For biochemical assessment, T2 mapping was prepared by using a multiecho spin-echo approach with particular attention to the cartilage zonal structure. Statistical evaluation was done by analyses of variance. The MOCART score showed no significant differences between the patella and MFC (p ≥ 0.05). With regard to biochemical T2 relaxation, higher T2 values were found throughout the MFC (p < 0.05). The zonal increase in T2 values from deep to superficial was significant for control cartilage (p < 0.001) and cartilage repair tissue (p < 0.05), with an earlier onset in the repair tissue of the patella. The assessment of cartilage repair tissue of the patella and MFC afforded comparable morphological results, whereas biochemical T2 values showed differences, possibly due to dissimilar biomechanical loading conditions.     

Validation of a new cardiac image fusion software for three-dimensional integration of myocardial perfusion SPECT and stand-alone 64-slice CT angiography

Purpose Combining the functional information of SPECT myocardial perfusion imaging (SPECT-MPI) and the morphological information of coronary CT angiography (CTA) may allow easier evaluation of the spatial relationship between coronary stenoses and perfusion defects. The aim of the present study was the validation of a novel software solution for three-dimensional (3D) image fusion of SPECT-MPI and CTA. Methods SPECT-MPI with adenosine stress/rest ^99mTc-tetrofosmin was fused with 64-slice CTA in 15 consecutive patients with a single perfusion defect and a single significant coronary artery stenosis (≥50% diameter stenosis). 3D fused SPECT/CT images were analysed by two independent observers with regard to superposition of the stenosed vessel onto the myocardial perfusion defect. Interobserver variability was assessed by recording the X, Y, Z coordinates for the origin of the stenosed coronary artery and the centre of the perfusion defect and measuring the distance between the two landmarks. Results SPECT-MPI revealed a fixed defect in seven patients, a reversible defect in five patients and a mixed defect in three patients and CTA documented a significant stenosis in the respective subtending coronary artery. 3D fused SPECT/CT images showed a match of coronary lesion and perfusion defect in each patient and the fusion process took less than 15 min. Interobserver variability was excellent for landmark detection (r = 1.00 and r = 0.99, p < 0.0001) and very good for the 3D distance between the two landmarks (r = 0.94, p < 0.001). Conclusion 3D SPECT/CT image fusion is feasible, reproducible and allows correct superposition of SPECT segments onto cardiac CT anatomy.     

MR spectroscopy (MRS) and magnetisation transfer imaging (MTI), lesion load and clinical scores in early relapsing remitting multiple sclerosis: a combined cross-sectional and longitudinal study

The purpose of this study was to correlate magnetic resonance imaging (MRI)-based lesion load assessment with clinical disability in early relapsing remitting multiple sclerosis (RRMS). Seventeen untreated patients (ten women, seven men; mean age 33.0 ± 7.9 years) with the initial diagnosis of RRMS were included for cross-sectional as well as longitudinal (24 months) clinical and MRI-based assessment in comparison with age-matched healthy controls. Conventional MR sequences, MR spectroscopy (MRS) and magnetisation transfer imaging (MTI) were performed at 1.5 T. Lesion number and volume, MRS and MTI measurements for lesions and normal appearing white matter (NAWM) were correlated to clinical scores [Expanded Disability Status Scale (EDSS), Multiple Sclerosis Functional Composite (MSFC)] for monitoring disease course after treatment initiation (interferon β-1a). MTI and MRS detected changes [magnetisation transfer ratio (MTR), N-acetylaspartate (NAA)/creatine ratio] in NAWM over time. EDSS and lesional MTR increases correlated throughout the disease course. Average MTR of NAWM raised during the study (p < 0.05) and correlated to the MSFC score (r = 0.476, p < 0.001). At study termination, NAA/creatine ratio of NAWM correlated to the MSFC score (p < 0.05). MTI and MRS were useful for initial disease assessment in NAWM. MTI and MRS correlated with clinical scores, indicating potential for monitoring the disease course and gaining new insights into treatment-related effects. J. Bellmann-Strobl, H. Stiepani and J. Wuerfel contributed equally to this work.     

USPIO-enhanced MR imaging of macrophage infiltration in native and transplanted kidneys: initial results in humans

The purpose of this study was to evaluate the detection and characterization of macrophage infiltration in native and transplanted kidneys using ultrasmall superparamagnetic iron oxide particles (USPIO). Among 21 patients initially enrolled, 12 scheduled for renal biopsy for acute or rapidly progressive renal failure (n = 7) or renal graft rejection (n = 5) completed the study. Three magnetic resonance (MR) sessions were performed with a 1.5-T system, before, immediately after and 72 h after i.v. injection of USPIO at doses of 1.7–2.6 mg of iron/kg. Signal intensity change was evaluated visually and calculated based on a region of interest (ROI) positioned on the kidney compartments. Histological examination showed cortical macrophage infiltration in four patients (>5 macrophages/mm²), two in native kidneys (proliferative extracapillary glomerulonephritis) and two in transplants (acute rejection). These patients showed a 33 ± 18% mean cortical signal loss on T2*-weighted images. In the remaining eight patients, with <5 macrophages/mm², there was no cortical signal loss. However, in three of these, presenting with ischemic acute tubular necrosis, a strong (42 ± 18%) signal drop was found in the medulla exclusively. USPIO-enhanced MR imaging can demonstrate infiltration of the kidneys by macrophages both in native and transplanted kidneys and may help to differentiate between kidney diseases.     

64-slice multidetector computed tomography (MDCT) for detection of aortic regurgitation and quantification of severity

BACKGROUND: Recent advances in 64-slice multidetector computed tomography (MDCT) provide an opportunity to assess coronary artery disease, left ventricular function and, potentially, valvular heart disease. OBJECTIVE: To determine the ability of 64-MDCT to both detect and to quantify the severity of aortic regurgitation (AR), as compared with transthoracic echocardiography (TTE). METHODS: We evaluated a total of 64 patients (43 males, mean age 63+/-11 years), 30 with varying severities of AR as assessed by TTE and 34 matched controls. The severity of AR by TTE was determined using the vena contracta, the ratio of jet to left ventricular outflow tract (LVOT) height, and the ratio of the jet to LVOT cross-sectional area. AR by MDCT was defined as a lack of coaptation of the aortic valve leaflets in diastole and, if detected, the maximum anatomic aortic regurgitant orifice was determined. RESULTS: All 34 control patients without AR were correctly identified by MDCT. There were 14 patients with mild AR, 10 with moderate AR, and 6 with severe AR by TTE. Of these patients, MDCT correctly identified 21 patients with AR (sensitivity 70%, specificity 100%, positive predictive value [PPV] 100%, and negative predictive value [NPV] 79%). Anatomic regurgitant orifice area measured by MDCT correlated well with the TTE-derived vena contracta (r=0.79, P<0.001), ratio of jet to LVOT height (r=0.79, P<0.001), and ratio of jet to LVOT cross-sectional area (r=0.75, P<0.001). CONCLUSIONS: Direct planimetric measurement of the aortic valve anatomic regurgitant orifice area on 64-MDCT provides an accurate, noninvasive technique for detecting and quantifying AR.     

Differentiating high-grade from low-grade chondrosarcoma with MR imaging

The purpose of the study was to evaluate the MR imaging features that differentiate between low-grade chondrosarcoma (LGCS) and high-grade chondrosarcoma (HGCS) and to determine the most reliable predictors for differentiation. MR images of 42 pathologically proven chondrosarcomas (28 LGCS and 14 HGCS) were retrospectively reviewed. There were 13 male and 29 female patients with an age range of 23–72 years (average age 51 years). On MR images, signal intensity, specific morphological characteristics including entrapped fat, internal lobular architecture, and outer lobular margin, soft tissue mass formation and contrast enhancement pattern were analysed. MR imaging features used to identify LGCS and HGCS were compared using univariate analysis and multivariate stepwise logistic regression analysis. On T1-weighted images, a central area of high signal intensity, which was not seen in LGCS, was frequently observed in HGCS (n = 5, 36%) (p < 0.01). Entrapped fat within the tumour was commonly seen in LGCS (n = 26, 93%), but not in HGCS (n = 1, 4%) (p < 0.01). LGCS more commonly (n = 24, 86%) preserved the characteristic internal lobular structures within the tumour than HGCSs (n = 4, 29%) (p < 0.01). Soft tissue formation was more frequently observed in HGCS (n = 11, 79%) than in LGCS (n = 1, 4%) (p < 0.01). On gadolinium-enhanced images, large central nonenhancing areas were exhibited in only two (7.1%) of LGCS, while HGCS frequently (n = 9, 64%) had a central nonenhancing portion (p < 0.01). Results of multivariate stepwise logistic regression analysis showed that soft tissue formation and entrapped fat within the tumour were the variables that could be used to independently differentiate LGCS from HGCS. There were several MR imaging features of chondrosarcoma that could be helpful in distinguishing HGCS from LGCS. Among them, soft tissue mass formation favoured the diagnosis of HGCS, and entrapped fat within the tumour was highly indicative of LGCS.