Brain metabolism and cognitive impairment in HIV infection: a 3-T magnetic resonance spectroscopy study

Background and Purpose

Human immunodeficiency virus (HIV)-associated dementia (HAD) has been extensively studied using magnetic resonance spectroscopy (MRS) at field strengths of 1.5 T. Higher magnetic field strengths (such as 3 T) allow for more reliable determination of certain compounds, such as glutamate (Glu) and glutamine (Gln). The current study was undertaken to investigate the utility of 3-T MRS for evaluating HIV+ patients with different levels of cognitive impairment with emphasis on the measurement of Glu and Glx (the sum of Glu and Gln).

Methods

Eighty-six HIV+ subjects were evaluated at 3 T using quantitative short echo time single-voxel MRS of frontal white matter (FWM) and basal ganglia (BG). Subjects were divided into three groups according to the Memorial Sloan Kettering (MSK) HIV dementia stage: 21 had normal cognition (NC) (MSK 0), 31 had mild cognitive impairment (MCI) without dementia (clinical MSK stage=0.5), and 34 had dementia (HAD) (MSK≥1). HIV+ subjects had also undergone standardized cognitive testing covering the domains of executive function, verbal memory, attention, information processing speed and motor and psychomotor speed. Between-group differences in metabolite levels in FWM and BG were evaluated using ANOVA. Pearson correlation coefficients were used to explore the associations between the Glu and Glx metabolites and neurocognitive results.

Results

FWM Glx was lower in HAD (8.1±2.1 mM) compared to both the MCI (9.17±2.1 mM) and NC groups (10.0±1.6 mM) (P=.006). FWM myo-inositol (mI) was higher in HAD (4.15±0.75 mM) compared to both MCI (3.86±0.85 mM) and NC status (3.4±0.67 mM) (P=.006). FWM Glx/creatine (Cr) was lower and FWM mI/Cr was significantly higher in the HAD compared to the MCI and NC groups (P=.01 and P=.004, respectively). BG N-acetyl aspartate (NAA) was lower in the HAD group (6.79±1.53 mM), compared to the MCI (7.5±1.06 mM) and NC (7.6±1.01 mM) groups (P=.036). Significant negative correlations were observed between Glu, Glx and NAA concentrations with Trail-Making Test B (P=.006, P=.0001 and P=.007, respectively), and significant positive correlation was found with the Digit symbol test (P=.02, P=.002 and P=.008, respectively). FWM Glx and NAA concentrations showed negative correlation with Grooved Pegboard nondominant hand (P=.02 and P=.04, respectively).

Conclusion

Patients with HAD have lower levels of Glx concentrations and Glx/Cr ratio in FWM, which was associated with impaired performance in specific cognitive domains, including executive functioning, fine motor, attention and working memory performance. Three-Tesla MRS measurements of Glx may be a useful indicator of neuronal loss/dysfunction in patients with HIV infection.     

Effect of Gd-EOB-DTPA on hepatic fat quantification using high-speed T2-corrected multi-echo acquisition in H MR spectroscopy

Purpose

To determine whether gadolinium ethoxybenzyldiethylenetriaminepentaacetic acid (Gd-EOB-DTPA) administration affects hepatic fat quantification by magnetic resonance spectroscopy (MRS) using the fast breath-hold high-speed T2-corrected multiecho (HISTO) technique.

Materials and Methods

Seventy-six patients underwent Gd-EOB-DTPA-enhanced liver MR and 15 sec breath-hold HISTO MRS (4 times), twice before and twice after Gd-EOB-DTPA administration. Two consecutive MRSs were performed immediately before the dynamic study. Post-contrast MRS was performed twice continuously, approximately 15 min after contrast injection, prior to obtaining 20-min hepatobiliary phase images. We used paired t-test and intraclass correlation coefficient (ICC) to evaluate the variability of the mean fat fraction (FF) on pre-contrast MRS and post-contrast MRS and the effect of the contrast agent on the mean FF.

Results

The mean FFs were not significantly different between pre-contrast MRS and post-contrast MRS (6.50% ± 6.54 versus 6.70% ± 6.61, P = 0.15). The ICC of FF calculation between pre- and post-contrast MRS was 0.984. The ICCs for the FF magnitude between pre- and post-contrast MRS were 0.452, 0.771, and 0.995 for FF < 5%, FF 5–10%, and FF ≥ 10%, respectively.

Conclusion

Gd-EOB-DTPA does not appear to influence hepatic fat quantification, especially for patients with hepatic steatosis.     

MRS study of the effects of minocycline on markers of neuronal and microglial integrity in ALS

Objective

Magnetic resonance spectroscopy (MRS) allows to monitor brain metabolites noninvasively in amyotrophic lateral sclerosis (ALS). The objective of this study was to use MRS to monitor the effect of minocycline treatment (200 mg/day) over a short period (6 weeks) on the brain metabolites in the precentral gyrus and brainstem in newly diagnosed ALS patients.

Methods

Ten ALS patients (not on riluzole treatment) were recruited and submitted to single-voxel proton MRS longitudinal examinations (1) before minocycline treatment, (2) 3 weeks and (3) 6 weeks after initiation of treatment.

Results

Results did not show the expected decrease of N-acetylaspartate/creatine (NAA/Cr) in the precentral gyrus, and an increased NAA/Cr ratio in the brainstem suggested neuronal recovery. The myo-inositol (mI)/Cr ratio was unchanged in the precentral gyrus, but increased in the brainstem, indicating a glial reaction.

Conclusions

MRS results suggest that minocycline treatment could be beneficial in the early stages of ALS.     

Quantitative liver iron measurement by magnetic resonance imaging: in vitro and in vivo assessment of the liver to muscle signal intensity and the R2* methods

Purpose

To evaluate the liver-to-muscle signal intensity and R2* methods to gain a transferable, clinical application for liver iron measurement.

Materials and Methods

Sixteen liver phantoms and 33 human subjects were examined using three 1.5-T MRI scanners from two different vendors. Phantom-to-muscle and liver-to-muscle signal intensity ratios were analyzed to determine MRI estimated phantom and hepatic iron concentration (M-PIC and M-HIC, respectively). R2* was calculated for the phantoms and the liver of human subjects. Seven patients' biochemical hepatic iron concentration was obtained.

Results

M-PIC and R2* results of three scanners correlated linearly to phantom iron concentrations (r=0.984 to 0.989 and r=0.972 to 0.981, respectively), and no significant difference between the scanners was found (P=.482 and P=.846, respectively) in vitro. The patients' R2* correlated linearly to M-HIC of the standard scanner (r=0.981). M-HIC values did not differ from those obtained from the biopsy specimens (P=.230). The difference in M-HIC was significant, but the difference in R2* was not significant between the scanners (P<.0001 and P=.505, respectively) in vivo.

Conclusion

Both methods, M-HIC and R2*, are reliable iron concentration indicators with linear dependence on iron concentration in vivo and in vitro. The R2* method was found to be comparable among different scanners. Transferability testing is needed for the use of the methods at various scanners.     

Potential clinical factors affecting hepatobiliary enhancement at Gd-EOB-DTPA-enhanced MR imaging

Objective

The objective was to clarify the clinical factors that might affect the degree of hepatic parenchymal enhancement at gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) imaging.

Materials and Methods

A total of 84 patients with (n=63) and without chronic liver disease (n=21) underwent Gd-EOB-DTPA-enhanced MR imaging. Contrast-enhanced MR images of hepatobiliary phase (HP) were obtained at 20 min after Gd-EOB-DTPA administration. The relative enhancement (RE) of liver parenchyma at 20 min HP was calculated from region of interest measurements at each patient. Then, these results were correlated with various clinical parameters using Pearson correlation coefficient or Spearman rank correlation coefficient. Furthermore, the predictor of the degree of hepatic parenchymal enhancement was determined using multiple regression analysis.

Results

The presence or absence of chronic liver disease (P=.002), ascites (P=.005) and splenomegaly (P=.027), and the values of prothrombin activity (P=.008), total bilirubin (T-Bil) (P=.001), albumin (P=.001), aspartate aminotransferase (AST) (P=.002) and cholinesterase (P=.007) were significantly correlated with the RE of liver parenchyma at 20 min HP. Among these parameters, increases of T-Bil (P=.011 to .028) and AST (P=.018 to .049) were predictors of decreased hepatic parenchymal enhancement.

Conclusions

Hepatic parenchymal enhancement of Gd-EOB-DTPA was affected by various clinical parameters. Impaired hepatobiliary enhancement may be predicted by routine biochemical tests, such as T-Bil and AST.     

Diffusion-weighted imaging versus superparamagnetic iron oxide (SPIO)-enhanced MRI: exclusive and combined values in the assessment of hepatic metastases

Purpose

The purpose was to validate diffusion-weighted imaging (DWI) in the assessment of hepatic metastases compared with superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging.

Materials and Methods

For 21 consecutive patients with 160 metastases from extrahepatic malignancy and 25 benign focal lesions, two radiologists evaluated four separate review sessions (I, SPIO-enhanced T2?-weighted images; II, precontrast DWI; III, SPIO-enhanced T2?-weighted images and precontrast DWI; IV, SPIO-enhanced T2?-weighted images plus precontrast and SPIO-enhanced DWI) and assigned confidence levels using a five-grade scale for each hepatic lesion.

Results

The A_z values after receiver operating characteristic curve analysis for Reader 1 and Reader 2 were 0.80 and 0.75 on session I, 0.91 and 0.91 on session II, 0.97 and 0.96 on session III and 0.96 and 0.96 on session IV, respectively. The A_z value of session II was significantly higher than that of session I (Reader 1, P=.004; Reader 2, P<.001), and that of session III was significantly higher than that of session I (P<.001 for each reader) or session II (Reader 1, P=.004; Reader 2, P=.003). Although there was no significant difference of A_z value between session III and session IV (Reader 1, P=.231; Reader 2, P=.878), the sensitivity improved for session IV compared with that for session III (Reader 1, P=.031; Reader 2, P=.039).

Conclusion

In the assessment of hepatic metastases, DWI can provide more accurate information than can SPIO-enhanced images. Diagnostic accuracy can be increased even more through the combination of both techniques.     

White matter hyperintensities and dynamics of postural control

Background

White matter hyperintensities (WMHs) on MRI have been associated with age, cardiovascular risk factors and falls in the elderly. This study evaluated the relationship between WMHs and dynamics of postural control in older adults without history of falls.

Methods

We studied 76 community-living subjects without history of falls (age 64.5±7.3 years). Brain and WMH volume calculations and clinical rating were done on fluid-attenuation inversion recovery (FLAIR) and MP-RAGE MR images on 3 T. Balance was assessed from the center of pressure displacement using the force platform during 3 min of quiet standing using traditional and dynamic measures (using stabilogram-diffusion analysis). Gait speed was measured from 12-min walk.

Results

Age-adjusted periventricular and focal WMHs were associated with changes in certain dynamic balance measures, including reduced range of postural sway in anteroposterior direction (fronto-temporal WMHs, P=.045; parieto-occipital WMHs, P=.009) and more irregular long-term mediolateral fluctuations (P=.046). Normal walking speed was not affected by WMHs.

Conclusions

Periventricular and focal WMHs affect long-term dynamics of postural control, which requires engagement of feedback mechanisms, and may contribute to mobility decline in the elderly.     

Similarity in the metabolic profile in macroscopically involved and un-involved colonic mucosa in patients with inflammatory bowel disease: an in vitro proton (H) MR spectroscopy study

Background

The histological extent of inflammatory bowel disease (IBD) is greater than that evident by colonoscopic evaluation. We hypothesized that metabolic profile in macroscopically un-involved colonic mucosa in IBD is similar to that of controls with healthy colon. We thus assessed the differences in metabolic profile in macroscopically involved and un-involved colonic mucosa of IBD patients to further substantiate the extent of disease.

Patients and Methods

Colonic mucosal biopsies were obtained and snap frozen from both the macroscopically un-involved and involved colonic mucosa of IBD patients and macroscopically normal colonic mucosa of controls and were subjected to in-vitro high-resolution proton (¹H) magnetic resonance (MR) spectroscopy and the concentrations of metabolites were determined.

Results

Thirty-two metabolites were assigned in the proton MR spectrum of colonic mucosa of IBD patients. The concentrations of amino acids (isoleucine, leucine, valine, arginine, lysine, glutamine/glutamate, alanine), membrane metabolites (choline, glycerophosphorylcholine/phosphorylcholine), glycolytic product (lactate) and short chain fatty acid (formate) were significantly lower while significantly high level of glucose were observed in the macroscopically un-involved colonic mucosa of IBD patients compared to the macroscopically normal mucosa of controls. There was no significant difference in the concentrations of metabolites in macroscopically involved and un-involved colonic mucosa of IBD patients.

Conclusions

The metabolic profile in macroscopically un-involved colonic mucosa of IBD patients is similar to that of macroscopically involved mucosa but different from colonic mucosa of controls. This suggests that even macroscopically un-involved colonic mucosa is metabolically abnormal and may explain the increase in extent of disease with time.     

In vivo C magnetic resonance spectroscopy of a human brain tumor after application of C-1-enriched glucose

Objectives

As a unique tool to assess metabolic fluxes noninvasively, ¹³C magnetic resonance spectroscopy (MRS) could help to characterize and understand malignancy in human tumors. However, its low sensitivity has hampered applications in patients. The aim of this study was to demonstrate that with sensitivity-optimized localized ¹³C MRS and intravenous infusion of [1-¹³C]glucose under euglycemia, it is possible to assess the dynamic conversion of glucose into its metabolic products in vivo in human glioma tissue.

Materials and Methods

Measurements were done at 3 T with a broadband single RF channel and a quadrature ¹³C surface coil inserted in a ¹H volume coil. A ¹H/¹³C polarization transfer sequence was applied, modified for localized acquisition, alternatively in two (50 ml) voxels, one encompassing the tumor and the other normal brain tissue.

Results

After about 20 min of [1-¹³C]glucose infusion, a [3-¹³C]lactate signal appeared among several resonances of metabolic products of glucose in MR spectra of the tumor voxel. The resonance of [3-¹³C]lactate was absent in MR spectra from contralateral tissue. In addition, the intensity of [1-¹³C]glucose signals in the tumor area was about 50% higher than that in normal tissue, likely reflecting more glucose in extracellular space due to a defective blood–brain barrier. The signal intensity for metabolites produced in or via the tricarboxylic acid (TCA) cycle was lower in the tumor than in the contralateral area, albeit that the ratios of isotopomer signals were comparable.

Conclusion

With an improved ¹³C MRS approach, the uptake of glucose and its conversion into metabolites such as lactate can be monitored noninvasively in vivo in human brain tumors. This opens the way to assessing metabolic activity in human tumor tissue.     

Impact of diffusion-weighted MR imaging on the characterization of small hepatocellular carcinoma in the cirrhotic liver

Purpose

The purpose of this study was to determine whether or not adding diffusion-weighted magnetic resonance imaging (DWI) to conventional magnetic resonance (MR) imaging sequences improves the characterization of small hepatocellular carcinoma (HCC) (≤2 cm) in the setting of cirrhotic liver compared to conventional sequences alone.

Materials and Methods

A total of 62 cirrhotic liver patients with 82 nodules smaller than 2 cm in diameter were enrolled, and all lesions were pathologically confirmed. For the first reading session, which included precontrast T1- and T2-weighted images and T1 dynamic contrast-enhanced images, preindicated lesions by a study coordinator were characterized by two radiologists. They determined the confidence levels in consensus for the presence of small HCC into four grades. In another session, respiratory-triggered diffusion-weighted MR images (b factor=50, 400 and 800 s/mm²) were added to the previously reviewed images, and the same two radiologists again determined the confidence levels. The diagnostic performance of the combined DWI–conventional sequences set and the conventional sequences alone set was evaluated using receiver operating characteristic curves. Sensitivity and specificity values for characterizing small HCCs were also calculated.

Results

The area under the receiver operating characteristic curve for the second interpretation session (0.86) was significantly higher (P=.038) than that of the first session (0.76). The sensitivity was significantly increased from 75.7% to 87.8% by adding DWI to the conventional sequences (P=.015). No significant differences were observed for specificity values.

Conclusion

Adding DWI to conventional imaging modalities improves the diagnosis of small HCCs in the cirrhotic liver in terms of diagnostic performance and sensitivity by increasing reader confidence.     

GESFIDE-PROPELLER Approach for Simultaneous R2 and R2* Measurements in the Abdomen

Purpose

To investigate the feasibility of combining GESFIDE with PROPELLER sampling approaches for simultaneous abdominal R2 and R2* mapping.

Materials and Methods

R2 and R2* measurements were performed in 9 healthy volunteers and phantoms using the GESFIDE-PROPELLER and the conventional Cartesian-sampling GESFIDE approaches.

Results

Images acquired with the GESFIDE-PROPELLER sequence effectively mitigated the respiratory motion artifacts, which were clearly evident in the images acquired using the conventional GESFIDE approach. There was no significant difference between GESFIDE-PROPELLER and reference MGRE R2* measurements (p = 0.162) whereas the Cartesian-sampling based GESFIDE methods significantly overestimated R2* values compared to MGRE measurements (p < 0.001).

Conclusion

The GESFIDE-PROPELLER sequence provided high quality images and accurate abdominal R2 and R2* maps while avoiding the motion artifacts common to the conventional Cartesian-sampling GESFIDE approaches.     

Optimization of MR diffusion-weighted imaging acquisitions for pancreatic cancer at 3.0 T

Objectives

To investigate and optimize diffusion-weighted imaging (DWI) acquisitions for pancreatic cancer at 3.0 T.

Methods

Forty-five patients with pancreatic cancer were examined by four DWI acquisitions with b values = 0 and 600 s/mm² at 3.0 T, including breath-holding DWI (BH-DWI), respiratory-triggered DWI (TRIG-DWI), respiratory-triggered DWI with inversion–recovery technique (TRIGIR-DWI), and free-breathing DWI with inversion–recovery technique (FBIR-DWI). Artifacts, contrast ratio (CR), contrast-to-noise ratio (CNR) and apparent diffusion coefficient (ADC) of pancreatic cancer were statistically compared among DWI acquisitions.

Results

TRIGIR-DWI displayed the lowest artifacts and highest CR compared to other DWI acquisitions. CNRs of pancreatic cancer in TRIG-DWI and TRIGIR-DWI were statistically higher than that in FBIR-DWI and BH-DWI. Different ADCs between pancreatic cancer and noncancerous pancreatic tissues were noticed by a paired-samples T test in TRIG-DWI (p = 0.017), TRIGIR-DWI (p = 0.00001) and FBIR-DWI (p = 0.000041).

Conclusions

TRIGIR-DWI may be the optimal acquisition of DWI for pancreatic cancer at 3.0 T.     

Dual-source parallel radiofrequency transmission for magnetic resonance breast imaging at 3 T: Any added clinical value?

Purpose

To investigate the influence of dual-source parallel radiofrequency (RF) excitation on clinical breast MR images.

Methods

A 3 T MR system with both dual-source and conventional single-source RF excitations was used to examine 22 patients. Axial TSE-T₂WI with fat suppression, TSE-T₁WI without fat suppression, THRIVE (3D field echo) and DWI (SE-EPI) were obtained by using both excitation techniques. Image homogeneity, image contrast and lesion conspicuity were measured or independently scored by two radiologists and were compared by paired-sample t test or Wilcoxon test.

Results

Both excitations revealed 24 lesions. For SE sequences using dual-source mode, image homogeneity was improved (P = 0.00), scan time was reduced, and ghost artifacts on DWI were significantly reduced (P = 0.00). However, image contrast was not increased and lesion conspicuity had no significant difference between two modes, except DWI on which lesion conspicuity was significantly improved (P = 0.00), due to less ghost artifacts. For field-echo sequence, image homogeneity, acquisition time, image contrast and lesion conspicuity had no significant difference between the two modes.

Conclusions

Dual-source parallel RF transmission has some added value for improving breast image quality. However, its value is limited in terms of improving lesion detection and characterization.     

Using Gd-EOB-DTPA-enhanced 3-T MRI for the differentiation of infiltrative hepatocellular carcinoma and focal confluent fibrosis in liver cirrhosis

Purpose

The purpose of the study was to determine significant imaging features to differentiate between infiltrative hepatocellular carcinoma (HCC) and confluent fibrosis (CF) in liver cirrhosis using Gd-EOB-DTPA-enhanced 3-T magnetic resonance imaging.

Material and methods

Nineteen infiltrative HCCs and eight CFs were included. We evaluated the difference in imaging findings and apparent diffusion coefficient (ADC) between the two entities. We compared T2-weighted image (WI) and hepatobiliary phase (HBP) in terms of the clarity of the lesion outer margin.

Results

Seventeen infiltrative HCCs showed lobulated margin, while focal CFs showed either straight (n = 3) or irregular margins (n = 5) (P = .001). All infiltrative HCCs had intact or bulging contours, and all focal CFs showed capsular retraction (P = .001). Fourteen infiltrative HCCs and two focal CFs showed arterial enhancement (P = .035). The ADC of infiltrative HCCs was significantly lower than that of CFs (P = .001). Satellite nodules were noted in 10 infiltrative HCCs. In terms of outer margin clarity, infiltrative HCCs showed a more distinct margin on HBP than on T2-WI (P = .005), while these two sequences were not significantly different in focal CFs (P = 1.000).

Conclusion

HBP improved the imaging characteristics of infiltrative HCC, allowing it to be distinguished from focal CF. Infiltrative HCC showed lower ADC values than focal CF. Lobular configuration, contour bulging, enhancement pattern, associated satellite nodules and portal vein thrombosis were still found to be highly suggestive MR findings for infiltrative HCC.     

Diffusion-weighted imaging (DWI) of the spleen in patients with liver cirrhosis and portal hypertension

Objective

The purpose of this study was to assess the influence of liver cirrhosis and portal hypertension on diffusion coefficients of the spleen.

Material and Methods

We retrospectively evaluated 50 patients with liver cirrhosis and 50 patients without any history of liver disease who underwent magnetic resonance imaging of the upper abdomen, including echo planar diffusion-weighted imaging using b values of 50, 300 and 600 mm²/s. Spleen apparent diffusion coefficient (ADC), liver ADC, muscle ADC and normalized spleen ADC (defined as the ratio of spleen ADC to muscle ADC) were compared between cirrhotic patients and patients in the control group and correlated with Child–Pugh stages. Reproducibility was assessed by measuring interclass correlation coefficient (n = 11). Additionally, in eight patients, ADC measurements were performed 1 day before and 3 days after transjugular intrahepatic portosystemic shunt (TIPSS) implantation.

Results

Compared with control subjects, patients with cirrhosis and portal hypertension had significantly higher spleen ADCs (P = .0001). There was a statistically significant correlation between Child–Pugh grade and spleen ADC (Pearson correlation coefficient, observer 1 r = 0.6, P = .0001; observer 2 r = 0.5, P = .0001). After TIPSS implantation, we observed a reduction in spleen ADC values. Spleen ADC measurements showed a high reproducibility (interclass correlation coefficient 0.75, P = .001).

Conclusion

Our data suggest that different stages of liver cirrhosis and portal hypertension correlate with ADC values of the spleen. Furthermore, ADC values of the spleen decrease after TIPSS implantation. Further studies are required to understand the potential clinical values of these observations.     

Assessment of hepatocellular carcinoma using apparent diffusion coefficient and diffusion kurtosis indices: preliminary experience in fresh liver explants

Objectives

The objective was to perform ex vivo evaluation of non-Gaussian diffusion kurtosis imaging (DKI) for assessment of hepatocellular carcinoma (HCC), including presence of treatment-related necrosis, using fresh liver explants.

Methods

Twelve liver explants underwent 1.5-T magnetic resonance imaging using a DKI sequence with maximal b-value of 2000 s/mm². A standard monoexponential fit was used to calculate apparent diffusion coefficient (ADC), and a non-Gaussian kurtosis fit was used to calculate K, a measure of excess kurtosis of diffusion, and D, a corrected diffusion coefficient accounting for this non-Gaussian behavior. The mean value of these parameters was measured for 16 HCCs based upon histologic findings. For each metric, HCC-to-liver contrast was calculated, and coefficient of variation (CV) was computed for voxels within the lesion as an indicator of heterogeneity. A single hepatopathologist determined HCC necrosis and cellularity.

Results

The 16 HCCs demonstrated intermediate-to-substantial excess diffusional kurtosis, and mean corrected diffusion coefficient D was 23% greater than mean ADC (P=.002). HCC-to-liver contrast and CV of HCC were greater for K than ADC or D, although these differences were significant only for CV of HCCs (P≤.046). ADC, D and K all showed significant differences between non-, partially and completely necrotic HCCs (P≤.004). Among seven nonnecrotic HCCs, cellularity showed a strong inverse correlation with ADC (r=−0.80), a weaker inverse correlation with D (− 0.24) and a direct correlation with K (r= 0.48).

Conclusions

We observed non-Gaussian diffusion behavior for HCCs ex vivo; this DKI model may have added value in HCC characterization in comparison with a standard monoexponential model of diffusion-weighted imaging.     

Gadoxetic acid-enhanced MRI compared with CT during angiography in the diagnosis of hepatocellular carcinoma

Purpose

To assess the value of gadoxetic acid-enhanced magnetic resonance imaging (MRI) for the pre-therapeutic detection of hepatocellular carcinoma (HCC) using receiver operating characteristic (ROC) analysis with the combination of computed tomography (CT) arterial portography and CT hepatic arteriography (CTAP/CTHA).

Materials and Methods

A total of 54 consecutive patients with 87 nodular HCCs were retrospectively analyzed. All HCC nodules were confirmed pathologically. Three blinded readers independently reviewed 432 hepatic segments, including 78 segments with 87 HCCs. Each reader read two sets of images: Set 1, CTAP/CTHA; Set 2, gadoxetic acid-enhanced MRI including a gradient dual-echo sequence and diffusion-weighted imaging (DWI). The ROC method was used to analyze the results. The sensitivity, specificity, positive predictive value, negative predictive value and sensitivity according to tumor size were evaluated.

Results

For each reader, the area under the curve was significantly higher for Set 2 than for Set 1. The mean area under the curve was also significantly greater for Set 2 than for Set 1 (area under the curve, 0.98 vs. 0.93; P = .0009). The sensitivity was significantly higher for Set 2 than for Set 1 for all three readers (P = .012, .013 and .039, respectively). The difference in the specificity, positive predictive values and negative predictive values of the two modalities for each reader was not significant (P > .05).

Conclusion

Gadoxetic acid-enhanced MRI including a gradient dual-echo sequence and DWI is recommended for the pre-therapeutic evaluation of patients with HCC.     

Multiple sclerosis: Benefits of q-space imaging in evaluation of normal-appearing and periplaque white matter

Introduction

Diffusion tensor imaging (DTI) reveals white matter pathology in patients with multiple sclerosis (MS). A recent non-Gaussian diffusion imaging technique, q-space imaging (QSI), may provide several advantages over conventional MRI techniques in regard to in vivo evaluation of the disease process in patients with MS. The purpose of this study is to investigate the use of root mean square displacement (RMSD) derived from QSI data to characterize plaques, periplaque white matter (PWM), and normal-appearing white matter (NAWM) in patients with MS.

Methods

We generated apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps by using conventional DTI data from 21 MS patients; we generated RMSD maps by using QSI data from these patients. We used the Steel–Dwass test to compare the diffusion metrics of regions of interest in plaques, PWM, and NAWM.

Results

ADC differed (P < 0.05) between plaques and PWM and between plaques and NAWM. FA differed (P < 0.05) between plaques and NAWM. RMSD differed (P < 0.05) between plaques and PWM, plaques and NAWM, and PWM and NAWM.

Conclusion

RMSD values from QSI may reflect microstructural changes and white-matter damage in patients with MS with higher sensitivity than do conventional ADC and FA values.     

Hippocampal volume is related to cognitive decline and fornicial diffusion measures in multiple sclerosis

Purpose

To assess for associations between hippocampal atrophy and measures of cognitive function, hippocampal magnetization transfer ratio (MTR), and diffusion measures of the fornix, the largest efferent white matter tract from the hippocampus, in patients with multiple sclerosis (MS) and controls.

Materials and Methods

A total of 53 patients with MS and 20 age- and sex-matched healthy controls participated in cognitive testing and scanning including high spatial-resolution diffusion imaging and a T1-MPRAGE scan. Hippocampal volume and fornicial thickness measures were calculated and compared to mean values of fornicial transverse diffusivity, mean diffusivity, longitudinal diffusivity, fractional anisotropy, mean hippocampal MTR, and scores on measures of episodic memory, processing speed, and working memory tasks.

Results

In patients with MS, hippocampal volume was significantly related to fornicial diffusion measures (P < 7 × 10^− 4) and to measures of verbal (P = 0.030) and visual spatial (P = 0.004) episodic memory and a measure of information processing speed (P < 0.037).

Discussion

These results highlight the role of the hippocampus in cognitive dysfunction in patients with MS and suggest that measures of hippocampal atrophy could be used to capture aspects of disease progression.     

Magnetic resonance imaging dynamic contrast enhancement (DCE) characteristics of healed myocardial infarction differ from viable myocardium

Purpose

To determine whether healed myocardial infarction alters dynamic contrast-enhancement (DCE) curve shapes as well as late gadolinium-enhancement (LGE).

Materials and methods

Twenty patients with chronic myocardial infarction underwent MR imaging at 1.5 T with blood and myocardial T1 measurements before and after contrast administration for forty minutes. Viable and infarcted myocardial partition coefficients were calculated using multipoint slope methods for ten different DCE sampling intervals and windows. Partition coefficients and coefficients of determination were compared with paired statistical tests to assess the linearity of DCE curve shapes over the 40 min time period.

Results

Calculated partition coefficients did not vary significantly between methods (p = 0.325) for viable myocardium but did differ for infarcted myocardium (p < 0.001), indicating a difference in infarcted DCE. There was a significant difference between viable and infarcted myocardial partition coefficients estimates for all methods with the exception of methods that included measurements during the first 10 min after contrast agent administration.

Conclusion

Myocardial partition coefficients calculated from a slope calculation vary in healed myocardial infarction based on the selection of samples due to non-linear DCE curve shapes. Partition coefficient calculations are insensitive to data sampling effects in viable myocardium due to linear DCE curve shapes.