Showing papers in "Journal of Magnetic Resonance Imaging in 2009"

Biodistribution of gadolinium-based contrast agents, including gadolinium deposition.

Abstract: The biodistribution of approved gadolinium (Gd) based contrast agents (GBCA) is reviewed. After intravenous injection GBCA distribute in the blood and the extracellular space and transiently through the excretory organs. Preclinical animal studies and the available clinical literature indicate that all these compounds are excreted intact. Elimination tends to be rapid and for the most part, complete. In renally insufficient patients the plasma elimination half-life increases substantially from hours to days depending on renal function. In patients with impaired renal function and nephrogenic systemic fibrosis (NSF), the agents gadodiamide, gadoversetamide, and gadopentetate dimeglumine have been shown to result in Gd deposition in the skin and internal organs. In these cases, it is likely that the Gd is no longer present as the GBCA, but this has still not been definitively shown. In preclinical models very small amounts of Gd are retained in the bone and liver, and the amount retained correlates with the kinetic and thermodynamic stability of the GBCA with respect to Gd release in vitro. The pattern of residual Gd deposition in NSF subjects may be different than that observed in preclinical rodent models. GBCA are designed to be used via intravenous administration. Altering the route of administration and/or the formulation of the GBCA can dramatically alter the biodistribution of the GBCA and can increase the likelihood of Gd deposition.

Prostate cancer detection with multi-parametric MRI: logistic regression analysis of quantitative T2, diffusion-weighted imaging, and dynamic contrast-enhanced MRI.

Abstract: Purpose To develop a multi-parametric model suitable for prospectively identifying prostate cancer in peripheral zone (PZ) using magnetic resonance imaging (MRI). Materials and Methods Twenty-five radical prostatectomy patients (median age, 63 years; range, 44–72 years) had T2-weighted, diffusion-weighted imaging (DWI), T2-mapping, and dynamic contrast-enhanced (DCE) MRI at 1.5 Tesla (T) with endorectal coil to yield parameters apparent diffusion coefficient (ADC), T2, volume transfer constant (Ktrans) and extravascular extracellular volume fraction (ve). Whole-mount histology was generated from surgical specimens and PZ tumors delineated. Thirty-eight tumor outlines, one per tumor, and pathologically normal PZ regions were transferred to MR images. Receiver operating characteristic (ROC) curves were generated using all identified normal and tumor voxels. Step-wise logistic-regression modeling was performed, testing changes in deviance for significance. Areas under the ROC curves (Az) were used to evaluate and compare performance. Results The best-performing single-parameter was ADC (mean Az [95% confidence interval]: Az,ADC: 0.689 [0.675, 0.702]; Az,T2: 0.673 [0.659, 0.687]; Az,Ktrans: 0.592 [0.578, 0.606]; Az,ve: 0.543 [0.528, 0.557]). The optimal multi-parametric model, LR-3p, consisted of combining ADC, T2 and Ktrans. Mean Az,LR-3p was 0.706 [0.692, 0.719], which was significantly higher than Az,T2, Az,Ktrans, and Az,ve (P < 0.002). Az,LR-3p tended to be greater than Az,ADC, however, this result was not statistically significant (P = 0.090). Conclusion Using logistic regression, an objective model capable of mapping PZ tumor with reasonable performance can be constructed. J. Magn. Reson. Imaging 2009;30:327–334. © 2009 Wiley-Liss, Inc.

Primer on gadolinium chemistry

Abstract: Gadolinium is widely known by all practitioners of magnetic resonance imaging (MRI) but few appreciate the basic solution chemistry of this trivalent lanthanide ion. Given the recent linkage between gadolinium contrast agents and nephrogenic systemic fibrosis, some basic chemistry of this ion must be more widely understood. This short primer on gadolinium chemistry is intended to provide the reader the background principles necessary to understand the basics of chelation chemistry, water hydration numbers, and the differences between thermodynamic stability and kinetic stability or inertness. We illustrate the fundamental importance of kinetic dissociation rates in determining gadolinium toxicity in vivo by presenting new data for a novel europium DOTA-tetraamide complex that is relatively unstable thermodynamically yet extraordinarily inert kinetically and also quite nontoxic. This, plus other literature evidence, forms the basis of the fundamental axiom that it is the kinetic stability of a gadolinium complex, not its thermodynamic stability, that determines its in vivo toxicity. J. Magn. Reson. Imaging 2009;30:1240-1248. (c) 2009 Wiley-Liss, Inc.

Characterizing iron deposition in multiple sclerosis lesions using susceptibility weighted imaging

Abstract: Results: There were a variety of new lesion characteristics identified by SWI, and these were classified into six types. A total of 75 lesions were seen only with conventional imaging, 143 only with SWI, and 204 by both. From the iron quantification measurements, a moderate linear correlation between signal intensity and iron content (phase) was established. Conclusion: The amount of iron deposition in the brain may serve as a surrogate biomarker for different MS lesion characteristics. SWI showed many lesions missed by conventional methods and six different lesion characteristics. SWI was particularly effective at recognizing the presence of iron in MS lesions and in the basal ganglia and pulvinar

Quantification of hepatic steatosis with MRI: the effects of accurate fat spectral modeling.

Abstract: Purpose To develop a chemical-shift–based imaging method for fat quantification that accounts for the complex spectrum of fat, and to compare this method with MR spectroscopy (MRS). Quantitative noninvasive biomarkers of hepatic steatosis are urgently needed for the diagnosis and management of nonalcoholic fatty liver disease (NAFLD). Materials and Methods Hepatic steatosis was measured with “fat-fraction” images in 31 patients using a multiecho chemical-shift–based water-fat separation method at 1.5T. Fat-fraction images were reconstructed using a conventional signal model that considers fat as a single peak at –210 Hz relative to water (“single peak” reconstruction). Fat-fraction images were also reconstructed from the same source images using two methods that account for the complex spectrum of fat; precalibrated and self-calibrated “multipeak” reconstruction. Single-voxel MRS that was coregistered with imaging was performed for comparison. Results Imaging and MRS demonstrated excellent correlation with single peak reconstruction (r2 = 0.91), precalibrated multipeak reconstruction (r2 = 0.94), and self-calibrated multipeak reconstruction (r2 = 0.91). However, precalibrated multipeak reconstruction demonstrated the best agreement with MRS, with a slope statistically equivalent to 1 (0.96 ± 0.04; P = 0.4), compared to self-calibrated multipeak reconstruction (0.83 ± 0.05, P = 0.001) and single-peak reconstruction (0.67 ± 0.04, P < 0.001). Conclusion Accurate spectral modeling is necessary for accurate quantification of hepatic steatosis with MRI. J. Magn. Reson. Imaging 2009;29:1332–1339. © 2009 Wiley-Liss, Inc.

Liver parenchymal enhancement of hepatocyte-phase images in Gd-EOB-DTPA-enhanced MR imaging: which biological markers of the liver function affect the enhancement?

Abstract: Purpose: To clarify the factors that predict enhancement of the liver parenchyma in hepatocyte-phase of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced MR imaging. Materials and Methods: Gd-EOB-DTPA–enhanced hepatocyte-phase MR images of 198 patients with chronic liver diseases (Child-Pugh class A in 112 patients, class B in 74 patients, and class C in 12 patients) were retrospectively analyzed. The hepatocyte-phase images were obtained using fat-suppressed T1-weighted gradient-echo images with a 3D acquisition sequence 10 min and 20 min after IV administration of Gd-EOB-DTPA (0.025 mmol/kg body weight). The quantitative liver–spleen contrast ratio (Q-LSC) was calculated using the signal intensities of the liver and spleen. Serum albumin levels, total bilirubin levels, prothrombin activity, and the results of indocyanine green clearance tests (ICGs) were recorded and correlated with the Q-LSC. Logistic regression analysis was performed to analyze which factors predict sufficient liver enhancement using a Q-LSC of 1.5 as a cutoff value. Results: Only ICGs and Child-Pugh classifications showed a statistically significant correlation with the Q-LSC. Logistic regression analysis showed that ICGs were the only factors that accurately predicted liver enhancement on hepatocyte-phase images. Conclusion: ICGs were found to be predictors of sufficient liver enhancement on hepatocyte-phase images. J. Magn. Reson. Imaging 2009;30:1042–1046. © 2009 Wiley-Liss, Inc.

Identification of calcification with MRI using susceptibility‐weighted imaging: A case study

Abstract: Susceptibility weighted imaging (SWI) is a new MRI technique that can identify calcification by using phase images. We present a single case with a partially calcified oligodendroglioma, multiple calcified cysticercosis lesions, and multiple physiologic calcifications in the same patient. SWI phase images and computed tomography (CT) images are compared. SWI phase images showed the same calcified lesions as shown on CT and sometimes some new calcifications. Our conclusion is that SWI filtered phase images can identify calcifications as well as CT in this case.

Effect of PRESS and STEAM sequences on magnetic resonance spectroscopic liver fat quantification.

Abstract: Purpose To compare PRESS and STEAM MR spectroscopy for assessment of liver fat in human subjects.

T1 Independent, T2* Corrected MRI with Accurate Spectral Modeling for Quantification of Fat: Validation in a Fat-Water-SPIO Phantom

Abstract: Purpose To validate a T(1)-independent, T(2)*-corrected fat quantification technique that uses accurate spectral modeling of fat using a homogeneous fat-water-SPIO phantom over physiologically expected ranges of fat percentage and T(2)* decay in the presence of iron overload. Materials and methods A homogeneous gel phantom consisting of vials with known fat-fractions and iron concentrations is described. Fat-fraction imaging was performed using a multiecho chemical shift-based fat-water separation method (IDEAL), and various reconstructions were performed to determine the impact of T(2)* correction and accurate spectral modeling. Conventional two-point Dixon (in-phase/out-of-phase) imaging and MR spectroscopy were performed for comparison with known fat-fractions. Results The best agreement with known fat-fractions over the full range of iron concentrations was found when T(2)* correction and accurate spectral modeling were used. Conventional two-point Dixon imaging grossly underestimated fat-fraction for all T(2)* values, but particularly at higher iron concentrations. Conclusion This work demonstrates the necessity of T(2)* correction and accurate spectral modeling of fat to accurately quantify fat using MRI.

Pancreatic diffusion‐weighted imaging (DWI): Comparison between mass‐forming focal pancreatitis (FP), pancreatic cancer (PC), and normal pancreas

Abstract: Purpose To compare diffusion-weighted imaging (DWI) findings and the apparent diffusion coefficient (ADC) values of pancreatic cancer (PC), mass-forming focal pancreatitis (FP), and the normal pancreas. Materials and Methods DWI (b = 0 and 600 seconds/mm2) findings of 14 patients with mass-forming FP proven by histopathology and or clinical follow-up, 10 patients with histopathologically-proven PC, and 14 subjects with normal pancreatic exocrine function and normal imaging findings were retrospectively evaluated. ADC values of the masses, the remaining pancreas, and the normal pancreas were measured. Results On b = 600 seconds/mm2 DWI, mass-forming FP was visually indistinguishable from the remaining pancreas whereas PC was hyperintense relative to the remaining pancreas. The mean ADC value of PC (1.46 ± 0.18 mm2/second) was significantly lower than the remaining pancreas (2.11 ± 0.32 × 10–3 mm2/second; P 0.05). Conclusion Differences on DWI may help to differentiate PC, mass-forming FP, and normal pancreas from each other. J. Magn. Reson. Imaging 2009;29:350–356. © 2009 Wiley-Liss, Inc.

Validation and reproducibility of aortic pulse wave velocity as assessed with velocity‐encoded MRI

Abstract: PURPOSE To validate magnetic resonance imaging (MRI) assessment of aortic pulse wave velocity (PWV(MRI)) with PWV determined from invasive intra-aortic pressure measurements (PWV(INV)) and to test the reproducibility of the measurement by MRI. MATERIALS AND METHODS PWV(MRI) was compared with PWV(INV) in 18 nonconsecutive patients scheduled for catheterization for suspected coronary artery disease. Reproducibility of PWV(MRI) was tested in 10 healthy volunteers who underwent repeated measurement of PWV(MRI) at a single occasion. Velocity-encoded MRI was performed on all participants to assess PWV(MRI) in the total aorta (Ao(total)), the proximal aorta (Ao(prox)), and the distal aorta (Ao(dist)). RESULTS The results are expressed as mean +/- SD, Pearson correlation coefficient (PCC), and intraclass correlation (ICC). Good agreement between PWV(MRI) and PWV(INV) was found for Ao(total) (6.5 +/- 1.1 m/s vs. 6.1 +/- 0.8 m/s; PCC = 0.53), Ao(prox) (6.5 +/- 1.3 m/s vs. 6.2 +/- 1.1 m/s; PCC = 0.69), and for Ao(dist) (6.9 +/- 1.1 m/s vs. 6.1 +/- 1.0 m/s; PCC = 0.71). Reproducibility of PWV(MRI) was high for Ao(total) (4.3 +/- 0.5 m/s vs. 4.6 +/- 0.7 m/s; ICC = 0.90, P < 0.01), Ao(prox) (4.3 +/- 0.9 m/s vs. 4.7 +/- 1.0 m/s; ICC = 0.87, P < 0.01), and Ao(dist) (4.3 +/- 0.6 m/s vs. 4.4 +/- 0.8 m/s; ICC = 0.92, P < 0.01). CONCLUSION MRI assessment of aortic pulse wave velocity shows good agreement with invasive pressure measurements and can be determined with high reproducibility.

Detection of bone metastases in non-small cell lung cancer patients: comparison of whole-body diffusion-weighted imaging (DWI), whole-body MR imaging without and with DWI, whole-body FDG-PET/CT, and bone scintigraphy.

Abstract: Purpose To prospectively compare the capability for bone metastasis assessment of whole-body diffusion-weighted imaging (DWI), magnetic resonance imaging (MRI) without and with DWI, [18F] fluoro-2-D-glucose positron emission tomography with computed tomography (FDG-PET/CT) and bone scintigraphy in non-small cell carcinoma (NSCLC) patients. Materials and Methods In all, 115 consecutive NSCLC patients (66 men, 49 women; mean age 72 years) prospectively underwent whole-body MRI, PET/CT, and bone scintigraphy before treatment. For each method, probability of metastasis was independently assessed by using a 5-point visual scoring system on a per-site basis. Receiver operating characteristic (ROC)-based positive tests were used to determine the practical threshold value for each method on a per-site basis. Sensitivities, specificities, and accuracies were then compared on a per-site and per-patient basis by means of McNemar's test. Results When the practical threshold values were adapted, specificity and accuracy of whole-body MRI with DWI were significantly higher than those of bone scintigraphy and PET/CT (P < 0.05). On a per-patient basis, specificity and accuracy of whole-body MRI with DWI were significantly higher than those of bone scintigraphy (P < 0.05). Conclusion Whole-body MRI with DWI can be used for bone metastasis assessment of NSCLC patients as accurate as bone scintigraphy and/or PET/CT. J. Magn. Reson. Imaging 2009;30:298–308. © 2009 Wiley-Liss, Inc.

Free-breathing diffusion-weighted imaging for the assessment of inflammatory activity in Crohn's disease.

Abstract: Purpose To investigate the application of free-breathing diffusion-weighted MR imaging (DWI) to the assessment of disease activity in Crohn's disease. Materials and Methods Thirty-one patients with Crohn's disease were investigated using free-breathing DWI without special patient preparation or IV or intraluminal contrast agent. The bowel was divided into seven segments, and disease activity was assessed visually on DWI. For quantitative analysis, the apparent diffusion coefficient (ADC) was measured in each segment. The findings of a conventional barium study or surgery were regarded as the gold standard for evaluating the diagnostic ability of DWI to assess disease activity. Results Upon visual assessment, the sensitivity, specificity, and accuracy for the detection of disease-active segments were 86.0, 81.4, and 82.4%, respectively. In the quantitative assessment, the ADC value in the disease-active area was lower than that in disease-inactive area in small and large bowels (1.61 ± 0.44×10−3 mm2/s versus 2.56 ± 0.51 × 10−3 mm2/s in small bowel and 1.52 ± 0.43 × 10−3 mm2/s versus 2.31 ± 0.59 × 10−3 mm2/s in large bowel, respectively, P<0.001). Conclusion Free-breathing DWI is useful in the assessment of Crohn's disease. The accuracy of DWI is high in evaluating disease activity, especially in the small bowel, and the ADC may facilitate quantitative analysis of disease activity. J. Magn. Reson. Imaging 2009;29:880–886. © 2009 Wiley-Liss, Inc.

Intermuscular adipose tissue (IMAT): association with other adipose tissue compartments and insulin sensitivity.

Abstract: Purpose To quantify intermuscular adipose tissue (IMAT) of the lower leg as well as to investigate associations with other adipose tissue (AT) compartments. The relationship between IMAT and insulin sensitivity was also examined. Materials and Methods Standardized quantification of IMAT was performed in a large cohort (N = 249) at increased risk for type 2 diabetes in the right calf by T1-weighted fast spin-echo imaging at 1.5T (Magnetom Sonata; Siemens Healthcare). Additionally, whole-body AT distribution was assessed. Insulin sensitivity was determined by glucose clamp. Results Males showed significantly more IMAT than females (2.1 ± 1.1 cm2 vs. 1.5 ± 0.9 cm2; P < 0.001). IMAT correlated well with other AT depots, especially with visceral AT (VAT; rfemales = 0.52, P < 0.0001 vs. rmales = 0.42, P < 0.0001). Moreover, IMAT showed a negative correlation with the glucose infusion rate (GIR; rfemales = −0.43, P = 0.0002 vs. rmales = −0.40, P = 0.0007). Conclusion Quantification of IMAT is possible by standard MR techniques. AT distribution of the lower leg is comparable to the visceral compartment with males having higher IMAT/VAT but lower subcutaneous AT (SCAT). IMAT seems to be involved in the pathogenesis of insulin resistance, as shown by the significant negative correlation with GIR. J. Magn. Reson. Imaging 2009. © 2009 Wiley-Liss, Inc.

Three-dimensional analysis of segmental wall shear stress in the aorta by flow-sensitive four-dimensional-MRI

Abstract: Purpose To assess the distribution and regional differences of flow and vessel wall parameters such as wall shear stress (WSS) and oscillatory shear index (OSI) in the entire thoracic aorta. Materials and Methods Thirty-one healthy volunteers (mean age = 23.7 ± 3.3 years) were examined by flow-sensitive four-dimensional (4D)-MRI at 3T. For eight retrospectively positioned 2D analysis planes distributed along the thoracic aorta, flow parameters and vectorial WSS and OSI were assessed in 12 segments along the vascular circumference. Results Mean absolute time-averaged WSS ranged between 0.25 ± 0.04 N/m2 and 0.33 ± 0.07 N/m2 and incorporated a substantial circumferential component (–0.05 ± 0.04 to 0.07 ± 0.02 N/m2). For each analysis plane, a segment with lowest absolute WSS and highest OSI was identified which differed significantly from mean values within the plane (P < 0.05). The distribution of atherogenic low WSS and high OSI closely resembled typical locations of atherosclerotic lesions at the inner aortic curvature and supraaortic branches. Conclusion The normal distribution of vectorial WSS and OSI in the entire thoracic aorta derived from flow-sensitive 4D-MRI data provides a reference constituting an important perquisite for the examination of patients with aortic disease. Marked regional differences in absolute WSS and OSI may help explaining why atherosclerotic lesions predominantly develop and progress at specific locations in the aorta. J. Magn. Reson. Imaging 2009;30:77–84. © 2009 Wiley-Liss, Inc.

Diffusion‐weighted imaging of breast cancer: Correlation of the apparent diffusion coefficient value with prognostic factors

Abstract: Purpose To evaluate the role of diffusion-weighted imaging (DWI) in the detection of breast cancers, and to correlate the apparent diffusion coefficient (ADC) value with prognostic factors. Materials and Methods Sixty-seven women with invasive cancer underwent breast MRI. Histological specimens were analyzed for tumor size and grade, and expression of estrogen receptors (ER), progesterone receptors, c-erbB-2, p53, Ki-67, and epidermal growth factor receptors. The computed mean ADC values of breast cancer and normal breast parenchyma were compared. Relationships between the ADC values and prognostic factors were determined using Wilcoxon signed rank test and Kruskal-Wallis test. Results DWI detected breast cancer as a hyperintense area in 62 patients (92.5 %). A statistically significant difference in the mean ADC values of breast cancer (1.09 ± 0.27 × 10−5 mm2/s) and normal parenchyma (1.59 ± 0.27 × 10−5 mm2/s) was detected (P < 0.0001). There were no correlations between the ADC value and prognostic factors. However, the median ADC value was lower in the ER-positive group than the ER negative group, and this difference was marginally significant (1.09 × 10−5 mm2/s versus 1.15 × 10−5 mm2/s, P = 0.053). Conclusion The ADC value was a helpful parameter in detecting malignant breast tumors, but ADC value could not predict patient prognosis. J. Magn. Reson. Imaging 2009;30:615–620. © 2009 Wiley-Liss, Inc.

MRI and histological analysis of beta-amyloid plaques in both human Alzheimer's disease and APP/PS1 transgenic mice.

Abstract: Purpose To investigate the relationship between MR image contrast associated with Aβ plaques and their histology and compare the histo-pathological basis of image contrast and the relaxation mechanism associated with Aβ plaques in human Alzheimer’s disease and transgenic APP/PS1 mouse tissues.

High-b-value diffusion-weighted MR imaging of hepatocellular lesions: estimation of grade of malignancy of hepatocellular carcinoma.

Abstract: Purpose: To evaluate the effectiveness of diffusion-weighted magnetic resonance imaging (DWI) in estimating the grade of malignancy of hepatocellular carcinoma. Materials and Methods: Dynamic contrast-enhanced computed tomography (CE-CT) and DWI (b value, 1000 s/mm2) were performed on 73 patients. Using DW images, the lesions were classified as “visible” or “invisible.” The apparent diffusion coefficient (ADC) of the lesions was measured. Furthermore, the lesions were classified as hypervascular or iso-hypovascular using arterial phase CE-CT images. The image findings for each lesion type were compared. Results: The 73 patients had 98 hepatocellular lesions, of which 12 were histologically diagnosed as dysplastic nodules; 39, well-differentiated HCCs; 33, moderately differentiated HCCs; and 14, poorly differentiated HCCs. The mean ADC values of moderately poorly-differentiated HCCs were significantly lower than well-differentiated HCCs and dysplastic nodules (P 90% of moderately (30/33) and poorly differentiated HCCs (13/14) were visible, while 51% of well-differentiated HCCs (20/39) and all dysplastic nodules were invisible. Of 22 iso-hypovascular lesions, 4 were visible on DW images and were poorly differentiated HCCs, whereas 18 were invisible and were dysplastic nodules (12/18) or well-differentiated HCCs (6/18). Conclusion: A combination of hypovascularity and visibility on DW images can help distinguish poorly differentiated HCCs from low-grade hepatocellular lesions (dysplastic nodules and well-differentiated HCCs). J. Magn. Reson. Imaging 2009;30:1005–1011. © 2009 Wiley-Liss, Inc.

Relationship of temporal resolution to diagnostic performance for dynamic contrast enhanced MRI of the breast.

Abstract: Purpose To investigate the relationship between temporal resolution of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and classification of breast lesions as benign versus malignant.

Role of thermodynamic and kinetic parameters in gadolinium chelate stability.

Abstract: In recent years there has been a renewed interest in the physicochemical properties of gadolinium chelates (GC). The aim of this review is to discuss the physicochemical properties of marketed GC with regard to possible biological consequences. GC can be classified according to three key molecular features: 1) the nature of the chelating moiety: either macrocyclic molecules in which Gd(3+) is caged in the preorganized cavity of the ligand, or linear, open-chain molecules; 2) ionicity: the ionicity of the molecule varies from neutral to tri-anionic agents; and 3) the presence or absence of an aromatic lipophilic moiety, which has a profound impact on the biodistribution of the GC. These parameters can also explain why GC differ considerably with regard to their thermodynamic stability constants and kinetic stability, as demonstrated by numerous studies. The concept of thermodynamic and kinetic stability is critically discussed, as it remains somewhat controversial, especially in predicting the amount of free gadolinium that may result from decomplexation of chelates in physiologic or pathologic situations. This review examines the possibility that the high kinetic stability provided by the macrocyclic structure combined with a high thermodynamic stability (reinforced by ionicity for macrocyclic chelates) can minimize the amount of free Gd(3+) released in the body. J. Magn. Reson. Imaging 2009;30:1249-1258. (c) 2009 Wiley-Liss, Inc.

Diffusion‐weighted imaging of the liver: Comparison of navigator triggered and breathhold acquisitions

Abstract: Purpose To compare a free breathing navigator triggered single shot echoplanar imaging (SS EPI) diffusion-weighted imaging (DWI) sequence with prospective acquisition correction (PACE) with a breathhold (BH) DWI sequence for liver imaging. Materials and Methods Thirty-four patients were evaluated with PACE-DWI and BH DWI of the liver using b-values of 0, 50, and 500 s/mm2. There were 29 focal liver lesions in 18 patients. Qualitative evaluation was performed on a 3-point scale (1–3) by two independent observers (maximum score 9). Quantitative evaluation included estimated SNR (signal to noise ratio), lesion-to-liver contrast ratio, liver and lesion apparent diffusion coefficients (ADCs), and coefficient of variation (CV) of ADC in liver parenchyma and focal liver lesions (estimate of noise contamination in ADC). Results PACE-DWI showed significantly better image quality, higher SNR and lesion-to-liver contrast ratio when compared with BH DWI. ADCs of liver and focal lesions with both sequences were significantly correlated (r = 0.838 for liver parenchyma, and 0.904 for lesions, P < 0.0001), but lower with the BH sequence (P < 0.02). There was higher noise contamination in ADC measurement obtained with BH DWI (with a significantly higher SD and CV of ADC). Conclusion The use of a navigator echo to trigger SS EPI DWI improves image quality and liver to lesion contrast, and enables a more precise ADC quantification compared with BH DWI acquisition. J. Magn. Reson. Imaging 2009;30:561–568. © 2009 Wiley-Liss, Inc.

Acquisition and reconstruction of undersampled radial data for myocardial perfusion magnetic resonance imaging

Abstract: Purpose To improve myocardial perfusion MRI by reconstructing undersampled radial data with a spatiotemporal constrained reconstruction method (STCR).

Prediction of locally recurrent prostate cancer after radiation therapy: incremental value of 3T diffusion-weighted MRI.

Abstract: Purpose To prospectively evaluate the incremental value of diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) maps in addition to T2-weighted imaging (T2WI) for predicting locally recurrent prostate cancer in patients with biochemical failure after radiation therapy. Materials and Methods Thirty-six consecutive patients with an increased prostate-specific antigen level after radiation therapy underwent 3T MRI followed by transrectal biopsy. The MRI findings and biopsy results were correlated in sextant prostate sectors of peripheral zones (PZs). Two radiologists in consensus reviewed T2WI and combined T2WI and DWI with ADC maps, and rated the likelihood of recurrent cancer on a five-point scale. ADC values were calculated for recurrent cancer and benign tissue. Results Of 216 sectors, 65 prostate sectors (30%) were positive for cancer in 18 patients. For predicting recurrent cancer, combined T2WI and DWI showed a greater sensitivity compared to T2WI (P < 0.001). A significantly greater area under the receiver operating characteristics curve (Az) was determined for combined T2WI and DWI (Az = 0.879, P < 0.01) as compared to T2WI (Az = 0.612). Mean ADC values between recurrent cancer and benign tissue showed a statistically significant difference (P < 0.01). Conclusion For predicting locally recurrent prostate cancer after radiation therapy, the use of combined T2WI and DWI showed a better diagnostic performance compared to T2WI. J. Magn. Reson. Imaging 2009;29:391–397. © 2009 Wiley-Liss, Inc.

Magnetic resonance (MR) differential diagnosis of breast tumors using apparent diffusion coefficient (ADC) on 1.5-T

Abstract: To review the published reports concerning the apparent diffusion coefficient (ADC) value evaluation for the differentiation between malignant and benign breast tumors, articles were searched with the inclusion criteria: (a) a 1.5-T unit was used; (b) the diagnostic criteria were clearly stated; (c) diffusion-weighted images (DWIs) were obtained, and ADC value was calculated; (d) ADC values of breast tumors were reported with mean +/- standard deviation (SD). Meta-analysis from 12 articles revealed that the pooled sensitivity and specificity were 0.89 (95% confidence interval [CI], 0.85-0.91) and 0.77 (95% CI, 0.69-0.84), respectively, and that only the maximum b factor correlated with the mean ADC values of malignant and benign tumors, and the noncancerous breast tissue (P< 0.05,P < 0.01,P< 0.05, respectively). In conclusion, ADC evaluation is useful for the differentiation between malignant and benign breast tumors.

Preoperative evaluation of pancreatic cancer: comparison of gadolinium-enhanced dynamic MRI with MR cholangiopancreatography versus MDCT.

Abstract: Purpose To determine the accuracy of magnetic resonance imaging (MRI) including dynamic imaging using three-dimensional gradient-echo (3D-GRE) sequences and MR cholangiopancreatograpy (MRCP) compared with that of multidetector row CT (MDCT) with regard to resectability in pancreas cancer. Materials and Methods From February 2004 to July 2008, 54 patients (32 men, 22 women: age range, 28–83 years; mean age, 63.1 years old) with surgically proven pancreatic carcinoma, who had undergone preoperative gadolinium-enhanced 3D-GRE MRI with MRCP and triple-phase MDCT, were included in this retrospective study. Two, clinically experienced attending radiologists independently reviewed the two image sets. These readers evaluated the tumor conspicuity, presence of vascular invasion, choledochal and duodenal invasion, lymph node metastases, distant metastasis, and tumor resectability. The results were compared with the surgical and histopathologic findings using receiver operating characteristic analysis (Az) and kappa statistics. Results Curative resections were performed on 42 patients. Regarding the tumor conspicuity, MRI had a significantly higher Az value compared with MDCT according to both reviewers (P 0.05). Two imaging sets showed a similar diagnostic performance in the evaluation of vascular involvement, lymph node metastasis, and distant metastasis. Conclusion Dynamic 3D-GRE MRI with MRCP shows superior tumor conspicuity and similar diagnostic performance compared with MDCT in evaluating the resectability of pancreatic cancer. J. Magn. Reson. Imaging 2009;30:586–595. © 2009 Wiley-Liss, Inc.

Spatiotemporal dynamics of low frequency fluctuations in BOLD fMRI of the rat.

Abstract: LOW FREQUENCY FLUCTUATIONS (LFFs) in the blood oxygenation level dependent (BOLD) functional MRI (fMRI) signal from areas known to be strongly connected anatomically are correlated even in the absence of a task or stimulus (1). These spontaneous fluctuations appear to originate from the same source as the task-related BOLD response, leading to the hypothesis that correlated fluctuations reflect coordinated variations in neural activity (2). The possibility that correlated LFFs reflect the spontaneous “functional connectivity” of the brain has excited the interest of the fMRI and neuroscience communities, and the number of studies using the technique is growing rapidly. Most research performed on LFFs falls into three categories. The first involves mapping functional networks in the brain. Networks associated with different systems including visual, motor, auditory, memory, and language have been detected in resting state fMRI studies (3,4). In addition, researchers have identified two widely present networks, one containing areas that are typically deactivated during a task (the “default mode” network) and another containing areas that are active during a wide variety of tasks and that may be related to attention (5). Studies in the second category focus on the effect of different interventions or pathological conditions on functional connectivity and LFFs. Anesthesia, hypercapnia, and cocaine administration have been reported to disrupt functional connectivity (6-8). Also, changes in functional connectivity have been observed in conditions including autism, Alzheimer’s disease, schizophrenia, and blindness (9-12). The third group of studies addresses the origin of the LFFs. Physiological processes such as respiration can introduce spatially localized correlations in functional MRI data, and several groups have examined the effects of physiological noise on functional connectivity (13-16). Networks of correlated areas persisted despite significant attenuation of physiological noise, indicating that the noise is not the primary source of the correlation (15,17). Recent work by several groups has provided additional support for the neural basis of functional connectivity. A strong reduction of functional connectivity between hemispheres has been reported after surgical severance of the corpus callosum, the primary interhemispheric fiber tract. Intrahemispheric connectivity, however, was retained (18). It has also been shown that functional connectivity and the relationship between correlated networks is related to behavioral variability and the ability to learn new muscle synergies, more evidence that the correlated signal fluctuations are closely related to functional changes in the brain (19,20). Additional support comes from combined electroencephalography (EEG) -fMRI studies, although the findings are not consistent between the studies (21-24), possibly due to differences in the areas examined or recording methods used. To better understand the relationship between neural activity and functional connectivity, several groups have recently turned to animal models (25-30). The use of animal models allows for more invasive experimental designs, which can give deeper insight into the LFFs. These studies have provided additional evidence of a link between coordinated neural activity and functional connectivity. Anesthesia-dependent changes in delta power correlation were shown to co-vary with changes in functional connectivity in rats, although the measurements were not performed simultaneously due to technical limitations (30). Shmuel and Leopold reported correlations between spontaneous neural activity and BOLD fluctuations in the visual cortex of monkeys in the absence of any stimulus (27). These results are an extension of previous work showing very slow (< 0.1 Hz) coherent oscillations in the band limited power of local field potentials obtained from monkey visual cortex (31). Current functional connectivity analysis techniques such as cross-correlation of time-courses (1) or independent component analysis (ICA) (32) provide only steady-state information about networks where the relationship between the areas involved is assumed to be maintained over the entire length of the scan. These analysis methods do not give any information about the spatiotemporal dynamics of the LFFs. From EEG and magnetoencephalography (MEG) studies, it is known that behaviorally relevant changes in network activity occur on much shorter time scales than the minutes required for the acquisition of functional connectivity data. If the LFFs used to map functional connectivity have a neural basis, it should be possible to identify dynamic changes in network activity using MRI. In support of this idea, the envelope of EEG is shown to predict fluctuations in cerebral blood flow measured using laser Doppler flowmetry in rats (33). The spatiotemporal dynamics of the LFFs might, therefore, enhance our interpretation of functional connectivity data and provide us with clues to the origin of the low frequency fluctuations. In this study, we report a preliminary investigation into the spatiotemporal dynamics of LFFs in the rodent model. The use of an animal model is conducive to future experiments combining functional connectivity MRI and electrophysiology. In addition, acquisition with very short repetition time (TR) and high spatial resolution is possible with the high-field animal scanners, which is necessary for obtaining spatiotemporal information from the data while avoiding aliasing. This will also allow us to address questions that remain unanswered for animal studies, including the relative contribution of different frequency components and the extent of physiological noise contamination. In previous animal studies, acquisition parameters did not allow the visualization of fine spectral details needed to address this issue. In addition, most animal studies were conducted using a fairly long repetition time and no physiological correction was performed. The contributions of respiration and the cardiac cycle have not been examined in the rodent model, and could be more severe than in humans due to the widespread use of high-field scanners (34). In this study, we describe the acquisition of functional connectivity data from the rat with high temporal resolution that allows separation of the primary cardiac and respiratory components from the frequencies of interest. High spectral resolution allows the identification of two low frequency peaks in the data acquired from the rat cortex. The peaks exhibit different functional connectivity specificity. We further characterize spatiotemporal characteristics of both peaks and identify patterns of LFF propagation, which may not be deduced from typical functional connectivity analysis methods.

Risk factors for NSF: a literature review.

Abstract: Emerging evidence linking gadolinium-based contrast agents (GBCAs) to nephrogenic systemic fibrosis (NSF) has changed medical practice patterns toward forgoing GBCA-enhanced magnetic resonance imaging (MRI) or substituting other imaging methods, which are potentially less accurate and often radiation-based. This shift has been based on reports of high NSF incidence at sites where a confluence of risk factors occurred in patients with severe renal dysfunction. This review article explores the factors that affect NSF risk, compares risks of alternative imaging procedures, and demonstrates how risk can be managed by careful selection of GBCA dose, timing of injection with respect to dialysis, and other factors. Nearly half of NSF cases are a milder form that does not cause contractures or reduce mobility. It appears that eliminating even a single risk factor can reduce NSF incidence/risk at least 10-fold. Elimination of multiple risk factors by using single-dose GBCA, dialyzing dialysis patients quickly following GBCA administration, avoiding GBCA in acute renal failure while serum creatinine is rising, and avoiding nonionic linear GBCA in renal failure patients may reduce NSF risk more than a thousand-fold, thereby allowing safe GBCA-enhanced MRI in virtually all patients. J. Magn. Reson. Imaging 2009;30:1298-1308. (c) 2009 Wiley-Liss, Inc.

Diminished visibility of cerebral venous vasculature in multiple sclerosis by susceptibility‐weighted imaging at 3.0 Tesla

Abstract: Multiple sclerosis (MS) is a disease of the central nervous system characterized by widespread demyelination, axonal loss and gliosis, and neurodegeneration; susceptibility-weighted imaging (SWI), through the use of phase information to enhance local susceptibility or T2* contrast, is a relatively new and simple MRI application that can directly image cerebral veins by exploiting venous blood oxygenation. Here, we use high-field SWI at 3.0 Tesla to image 15 patients with clinically definite relapsing-remitting MS and to assess cerebral venous oxygen level changes. We demonstrate significantly reduced visibility of periventricular white matter venous vasculature in patients as compared to control subjects, supporting the concept of a widespread hypometabolic MS disease process. SWI may afford a noninvasive and relatively simple method to assess venous oxygen saturation so as to closely monitor disease severity, progression, and response to therapy.

Dynamic contrast-enhanced magnetic resonance imaging of abdominal solid organ and major vessel: Comparison of enhancement effect between Gd-EOB-DTPA and Gd-DTPA

Abstract: Purpose To evaluate the differences in enhancement of the abdominal solid organ and the major vessel on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) obtained with gadolinium ethoxybenzyldiethylenetriamine pentaacetic acid (Gd-EOB-DTPA: EOB) and gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) in the same patients. Materials and Methods A total of 13 healthy volunteers underwent repeat assessments of abdominal MR examinations with DCE-MRI using either Gd-DTPA at a dose of 0.1 mmol/kg body weight or EOB at a dose of 0.025 mmol/kg body weight. DCE images were obtained at precontrast injection and in the arterial phase (AP: 25 seconds), portal phase (PP: 70 seconds), and equilibrium phase (EP: 3 minutes). The signal intensities (SIs) of liver at AP, PP, and EP; the SIs of spleen, renal cortex, renal medulla, pancreas, adrenal gland, aorta at AP; and the SIs of portal vein and inferior vena cava (IVC) at PP were defined using region-of-interest measurements, and were used for calculation of signal intensity ratio (SIR). Results The mean SIRs of liver (0.195 ± 0.140), spleen (1.35 ± 0.353), renal cortex (1.58 ± 0.517), renal medulla (0.548 ± 0.259), pancreas (0.540 ± 0.183), adrenal gland (1.04 ± 0.405), and aorta (2.44 ± 0.648) at AP as well as the mean SIRs of portal vein (1.85 ± 0.477) and IVC (1.16 ± 0.187) at PP in the EOB images were significantly lower than those (0.337 ± 0.200, 1.99 ± 0.443, 2.01 ± 0.474, 0.742 ± 0.336, 0.771 ± 0.227, 1.26 ± 0.442, 3.22 ± 1.20, 2.73 ± 0.429, and 1.68 ± 0.366, respectively) in the Gd-DTPA images (P < 0.05 each). There was no significant difference in mean SIR of liver at PP between EOB (0.529 ± 0.124) and Gd-DTPA (0.564 ± 0.139). Conversely, the mean SIR of liver at EP was significantly higher with EOB (0.576 ± 0.167) than with Gd-DTPA (0.396 ± 0.093) (P < 0.001). Conclusion Lower arterial vascular and parenchymal enhancement with Gd-EOB, as compared with Gd-DTPA, may require reassessment of its dose, despite the higher late venous phase liver parenchymal enhancement. J. Magn. Reson. Imaging 2009;29:636–640. © 2009 Wiley-Liss, Inc.

Normal biventricular function, volumes, and mass in children aged 8 to 17 years.

Abstract: Purpose To assess normal values for biventricular function, volumes, and mass with current cardiovascular magnetic resonance (CMR) imaging sequences in children Materials and Methods Included in the study were 60 healthy children aged 8–17 years A short axis set of contiguous slices was acquired with CMR imaging employing steady-state free precession Biventricular end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), and mass were determined Uni- and multivariate linear regression analyses were performed to study the interrelation of age, gender, and body surface area (BSA) on biventricular volumes and mass The coefficient of variation was calculated for intra- and interobserver variability Results EF did not differ between boys and girls (mean LV-EF 69 ± (SD) 5%, mean RV-EF 65 ± 5%) BSA had good (EDV, mass) and modest (ESV) correlation with biventricular measurements Gender appeared a significant modifier of these relations, whereas age had no independent contribution The intra- and interobserver coefficient of variation was in the range 21%–139% for biventricular EDV, ESV, and mass Conclusion This study reveals gender-specific normative data for biventricular function, volumes, and mass in children age 8–17 years that can be used as reference data in the follow-up of pediatric cardiac patients J Magn Reson Imaging 2009;29:552–559 © 2009 Wiley-Liss, Inc