Can diffusion-weighted imaging be used as a reliable sequence in the detection of malignant pulmonary nodules and masses?

Recent developments in diffusion-weighted magnetic resonance imaging (DWI) make it possible to image malignant tumors to provide tissue contrast based on difference with the diffusion of water molecules among tissues, which can be measured by the apparent diffusion coefficient (ADC) value. We aimed to assess the diagnostic accuracy of DWI for benign/malignant discrimination of pulmonary nodules/masses with a meta-analysis. The MEDLINE, EMBASE, Cancerlit and Cochrane Library database, from January 2001 to August 2011, were searched for studies evaluating the diagnostic accuracy of DWI for benign/malignant discrimination of pulmonary nodules. We determined sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LRP and LRN), and constructed summary receiver operating characteristic SROC) curves. Across 10 studies (545 patients), there was no evidence of publication bias (P= .22, bias=−19.19). DWI had a pooled sensitivity of 0.84 (95% CI, 0.76–0.90) and a pooled specificity of 0.84 (95% CI, 0.64–0.94). Overall, LRP was 5.3 (95% CI, 2.1–13.0) and LRN was 0.19 (95% CI, 0.12–0.30). In patients with high pretest probabilities, DWI enabled confirmation of malignant pulmonary lesion; in patients with low pretest probabilities, DWI enabled exclusion of malignant pulmonary lesion. Worst-case-scenario (pretest probability, 50%) posttest probabilities were 84% and 16% for positive and negative DWI results, respectively. Diffusion-weighted magnetic resonance imaging can be used to differentiate malignant from benign pulmonary lesions. High-quality prospective studies regarding DWI in the evaluation of pulmonary nodules are still needed to be conducted.     

Short- and midterm repeatability of magnetic resonance elastography in healthy volunteers at 3.0 T

The purpose of this study was to evaluate the short- and midterm repeatability of liver stiffness measurements with magnetic resonance elastography (MRE) in healthy subjects at 3.0 T. Twenty-two healthy volunteers were enrolled in this prospective study. The stiffness measurements were obtained from three slices with three repeated acquisitions for each slice (session 1) by two independent raters. After a mean period of 7 ± 2 days (session 2) and 195 ± 15 days (session 3), each subject was scanned again using the same protocol and MR system. The liver stiffness differences were calculated between sessions or raters. The intraclass correlation coefficient (ICC) was calculated to assess interrater agreement and intersession agreement. The stiffness differences over the short- and midterm intervals was (− 0.004 ± 0.086) kPa for sessions 1–2, lower than (− 0.055 ± 0.150) kPa for sessions 1–3 and (− 0.051 ± 0.173) kPa for sessions 2–3. The liver stiffness was more repeatable for the short-term interval with the mean overall ICC of 0.96 (sessions 1–2) (95% confidence interval [CI]: 0.90–0.98) compared with 0.91 (sessions 1–3) (95% CI: 0.78–0.96) and 0.87 (sessions 2–3) (95% CI: 0.69–0.95) for the midterm intervals. The overall ICC of interrater agreement was excellent at 0.987 (95% CI: 0.983 to 0.990). These results confirm that MRE is a reproducible technique for liver stiffness quantification over short- and midterm intervals up to 6 months in a healthy population at 3.0 T.     

MRI detection of brown adipose tissue with low fat content in newborns with hypothermia

Purpose

To report the observation of brown adipose tissue (BAT) with low fat content in neonates with hypoxic–ischemic encephalopathy (HIE) after they have undergone hypothermia therapy.

Materials and Methods

The local ethics committee approved the imaging study. Ten HIE neonates (3 males, 7 females, age range: 2–3 days) were studied on a 3-T MRI system using a low-flip-angle (3°) six-echo proton-density-weighted chemical-shift-encoded water-fat pulse sequence. Fat-signal fraction (FF) measurements of supraclavicular and interscapular (nape) BAT and adjacent subcutaneous white adipose tissues (WAT) were compared to those from five non-HIE neonates, two recruited for the present investigation and three from a previous study.

Results

In HIE neonates, the FF range for the supraclavicular, interscapular, and subcutaneous regions was 10.3%–29.9%, 28.0%–57.9%, and 62.6%–88.0%, respectively. In non-HIE neonates, the values were 23.7%–42.2% (p = 0.01), 45.4%–59.5% (p = 0.06), and 67.8%–86.3% (p = 0.38), respectively. On an individual basis, supraclavicular BAT FF was consistently the lowest, interscapular BAT values were higher, and subcutaneous WAT values were the highest (p < 0.01).

Conclusion

We speculate that hypothermia therapy in HIE neonates likely promotes BAT-mediated non-shivering thermogenesis, which subsequently leads to a depletion of the tissue's intracellular fat stores. We believe that this is consequently reflected in lower FF values, particularly in the supraclavicular BAT depot, in contrast to non-HIE neonates.     

MR evaluation of breast lesions obtained by diffusion-weighted imaging with background body signal suppression (DWIBS) and correlations with histological findings

Objectives

Diffusion imaging represents a new imaging tool for the diagnosis of breast cancer. This study aims to investigate the role of diffusion-weighted MRI with background body signal suppression (DWIBS) for evaluating breast lesions.

Methods

90 patients were prospectively evaluated by MRI with STIR, TSE-T2, contrast enhanced THRIVE-T1 and DWIBS sequences. DWIBS were analyzed searching for the presence of breast lesions and calculating the ADC value. ADC values of ≤ 1.44 × 10^- 3 mm²/s were considered suspicious for malignancy. This analysis was then compared with the histological findings. Sensitivity, specificity, diagnostic accuracy (DA), positive predictive value (PPV) and negative (NPV) were calculated.

Results

In 53/90 (59%) patients, DWIBS indicated the presence of breast lesions, 16 (30%) with ADC values of  > 1.44 and 37 (70%) with ADC ≤ 1.44. The comparison with histology showed 25 malignant and 28 benign lesions. DWIBS sequences obtained sensitivity, specificity, DA, PPV and NPV values of 100, 82, 87, 68 and 100%, respectively.

Conclusion

DWIBS can be proposed in the MRI breast protocol representing an accurate diagnostic complement.     

Diffraction gratings of isotropic negative-phase velocity materials

Diffraction of electromagnetic plane waves by the gratings made by periodically corrugating the exposed planar boundaries of homogeneous, isotropic, linear dielectric-magnetic half-spaces is examined. The phase velocity vector in the diffracting material can be either co-parallel or anti-parallel to the time-averaged Poynting vector, thereby allowing for the material to be classified as of either the positive- or the negative-phase velocity (PPV or NPV) type. Three methods used for analyzing dielectric gratings — the Rayleigh-hypothesis method, a perturbative approach, and the C formalism — are extended here to encompass NPV gratings by a careful consideration of field representation inside the refracting half-space. Corrugations of both symmetric as well as asymmetric shapes are studied, as also the diversity of grating response to the linear polarization states of the incident plane wave. The replacement of PPV grating by its NPV analog affects only nonspecular diffraction efficiencies when the corrugations are shallow, and the effect on specular diffraction efficiencies intensifies as the corrugations deepen. Whether the type of the refracting material is NPV or PPV is shown to affect surface wave propagation as well as resonant excitation of surface waves.     

Diffusion-weighted MR imaging for assessing synovitis of wrist and hand in patients with rheumatoid arthritis: A feasibility study

The purpose of this study was to investigate the feasibility of diffusion-weighted imaging (DWI) in detecting synovitis of wrist and hand in patients with rheumatoid arthritis (RA) and evaluate its sensitivity, specificity and accuracy as compared to T₂-weighted imaging (T2WI) with short tau inversion recovery (STIR) with the reference standard contrast-enhanced magnetic resonance imaging (CE-MRI). Twenty-five patients with RA underwent MR examinations including DWI, T2WI with STIR and CE-MRI. MR images were reviewed for the presence and location of synovitis of wrist and hand. The sensitivity, specificity and accuracy of DWI and T2WI with STIR were calculated respectively and then compared. All patients included in this study completed MR examinations and yielded diagnostic image quality of DWI. For individual joint, there was good to excellent inter-observer agreement (k = 0.62–0.83) using DWI images, T2WI with STIR images and CE-MR images, respectively. There was a significance between DWI and T2WI with STIR in analyzing proximal interphalangeal joints II–V, respectively (P < 0.05). The k-values for the detection of synovitis indicated excellent overall inter-observer agreements using DWI images (k = 0.86), T2WI with STIR images (k = 0.85) and CE-MR images (k = 0.91), respectively. Overall, DWI demonstrated a sensitivity, specificity and accuracy of 75.6%, 89.3% and 84.6%, respectively, for detection of synovitis, while 43.0%, 95.7% and 77.6% for T2WI with STIR, respectively. DWI showed positive lesions much better and more than T2WI with STIR. Our results indicate that DWI presents a novel non-invasive approach to contrast-free imaging of synovitis. It may play a role as an addition to standard protocols.     

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.     

Whole-body diffusion-weighted imaging vs. FDG-PET for the detection of non-small-cell lung cancer. How do they measure up?

Objective

To compare the diagnostic efficacy of whole-body diffusion-weighted imaging (WB-DWI) and [18F] fluoro-2-D-glucose PET/CT(FDG-PET/CT)for assessment of non–small cell lung cancer (NSCLC) patients.

Materials and Methods

A group of 56 patients (21 female, 35 male; 35–76 years) with NSCLC proved by pathologic examination or follow-up imaging findings was set as reference standards, and all patients underwent both WB-DWI at 1.5T (MAGNETOM Avanto) and PET/CT (Biograph 16). For WB-DWI, a free breathing diffusion-weighted single-shot spin-echo epi-sequence in five-stations (head-neck, thorax, abdomen, pelvis-thigh) was used. Each station-series contained 30 contiguous axial slices. Imaging parameters: FOV 360×360 mm, matrix size 128×80. B-values: 0 and 1000 s/mm² applied along x, y and z, 5 averages, acquisition time: 2.23 min/series, total: 11.55 min. The efficacy of WB-DWI and PET/CT were determined in a blinded reading by two radiologists and two nuclear medicine physicians using pathology and size change during follow up exams as the reference standard.

Results

Primary tumors (n=56 patients) were correctly detected in 56 (100%) patients by both PET/CT and WB-DWI. Ninety-six lymph nodes metastases were determined with pathologic and follow-up examinations. Sensitivity, specificity, accuracy, positive predictive value (PPV), negative predictive value (NPV) being for lymph node metastases: 91%, 90%, 90%, 96%, 80% with WB-DWI and 98%, 97%, 97%, 99%, 93% with PET-CT, other metastases: 90%, 95%, 92%, 97%, 83% with WB-DWI and 98%, 100%, 98%, 100%, 95% with PET-CT). Differences in the accuracy of lymph node metastasis detection between PET/CT and WB-DWI (P=.031) were significant. The differences were not statistically significant for detection of other metastases.

Conclusions

WB-DWI is a feasible clinical technique for the assessment of NSCLC, lymph nodes and metastastic spread with high sensitivity and accuracy, but it was limited in the evaluation of neck lymph node metastases and small metastastic lung nodules.     

In vivo comparison of three ultrasound vector velocity techniques to MR phase contrast angiography

The objective of this paper is to validate angle independent vector velocity methods for blood velocity estimation. Conventional Doppler ultrasound (US) only estimates the blood velocity along the US beam direction where the estimate is angle corrected assuming laminar flow parallel to vessel boundaries. This results in incorrect blood velocity estimates, when angle of insonation approaches 90° or when blood flow is non-laminar. Three angle independent vector velocity methods are evaluated in this paper: directional beamforming (DB), synthetic aperture flow imaging (STA) and transverse oscillation (TO). The performances of the three methods were investigated by measuring the stroke volume in the right common carotid artery of 11 healthy volunteers with magnetic resonance phase contrast angiography (MRA) as reference. The correlation with confidence intervals (CI) between the three vector velocity methods and MRA were: DB vs. MRA: R = 0.84 (p < 0.01, 95% CI: 0.49–0.96); STA vs. MRA: R = 0.71 (p < 0.05, 95% CI: 0.19–0.92) and TO vs. MRA: R = 0.91 (p < 0.01, 95% CI: 0.69–0.98). No significant differences were observed for any of the three comparisons (DB vs. MRA: p = 0.65; STA vs. MRA: p = 0.24; TO vs. MRA: p = 0.36). Bland–Altman plots were additionally constructed, and mean differences with limits of agreements (LoA) for the three comparisons were: DB vs. MRA = 0.17 ml (95% CI: −0.61–0.95) with LoA = −2.11–2.44 ml; STA vs. MRA = −0.55 ml (95% CI: −1.54–0.43) with LoA = −3.42–2.32 ml; TO vs. MRA = 0.24 ml (95% CI: −0.32–0.81) with LoA = −1.41–1.90 ml. According to the results, reliable volume flow estimates can be obtained with all three methods. The three US vector velocity techniques can yield quantitative insight into flow dynamics and visualize complex flow patterns, which potentially can give the clinician a novel tool for cardiovascular disease assessment.     

High resolution diffusion weighted magnetic resonance imaging of the pancreas using reduced field of view single-shot echo-planar imaging at 3 T

Diffusion weighted magnetic resonance imaging (DWI) has been mostly acquired using single-shot echo-planar imaging (ss EPI) to minimize motion induced artifacts. The spatial resolution, however, is inherently limited in ss EPI especially for abdominal imaging, even with the advances in parallel imaging. A novel method of reduced Field of View ss EPI (rFOV ss EPI) has achieved high resolution DWI in human carotid artery, spinal cord with reduced blurring and higher spatial resolution than conventional ss EPI, but it has not been used to pancreas imaging. In the work, comparisons between the full FOV ss-DW EPI and rFOV ss-DW EPI in image qualities and ADC values of pancreatic tumors and normal pancreatic tissues were performed to demonstrate the feasibility of pancreatic high resolution rFOV DWI. There were no significant differences in the mean ADC values between full FOV DWI and rFOV DWI for the 17 subjects using b = 600 s/mm² (P = 0.962). However, subjective scores of image quality was significantly higher at rFOV ss DWI (P = 0.008 and 0.000 for b-value = 0 s/mm² and 600 s/mm² respectively). The spatial resolution of DWI for pancreas was increased by a factor of over 2.0 (from almost 3.0 mm/pixel to 1.25 mm/pixel) using rFOV ss EPI technique. Reduced FOV ss EPI can provide good DW images and is promising to benefit applications for pancreatic diseases.     

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.     

Effect of gadolinium injection on diffusion-weighted imaging with background body signal suppression (DWIBS) imaging of breast lesions

Objectives

Diffusion-weighted imaging with background body signal suppression (DWIBS) provides both qualitative and quantitative imaging of breast lesions and are usually performed before contrast material injection (CMI). This study aims to assess whether the administration of gadolinium significantly affects DWIBS imaging.

Methods

200 patients were prospectively evaluated by MRI with STIR, TSE-T2, pre-CMI DWIBS, contrast enhanced THRIVE-T1 and post-CMI DWIBS sequences. Pre and post-CMI DWIBS were analyzed searching for the presence of breast lesions and calculating the ADC value. ADC values of ≤ 1.44 × 10^- 3 mm²/s were considered suspicious for malignancy. This analysis was then compared with the histological findings. Sensitivity, specificity, diagnostic accuracy (DA), positive predictive value (PPV) and negative (NPV) were calculated for both sequences and represented by ROC analysis. Pre and post-CMI ADC values were compared by using the paired t test.

Results

In 150/200 (59%) patients, pre and post-CMI DWIBS indicated the presence of breast lesions, 53 (35%) with ADC values of > 1.44 × 10^- 3 mm²/s and 97 (65%) with ADC ≤ 1.44 × 10^- 3 mm²/s. Pre-CMI and post-DWIBS sequences obtained the same sensitivity, specificity, DA, PPV and NPV values of 97%, 83%, 89%, 79% and 98%. The mean ADC value of benign lesions was 1.831 ± 0.18 × 10^- 3 mm²/s before and 1.828 ± 0.18 × 10^- 3 mm²/s after CMI. The mean ADC value of the malignant lesions was 1.146 ± 0.16 × 10^- 3 mm²/s before and 1.144 ± 0.16 × 10^- 3 mm²/s after CMI. No significant difference was found between pre and post CMI ADC values (p > 0.05).

Conclusion

DWIBS imaging is not influenced by CMI. Breast MR protocol could be modified by placing DWIBS after dynamic contrast enhanced sequences in order to maximize patient cooperation.     

Ultrasound-assisted extraction of resveratrol from functional foods: Cookies and jams

Rapid extraction techniques with ultrasonic systems have been established to extract resveratrol from two functional foods, namely cookies and jams. The ultrasound-assisted extraction (UAE) was optimized using a full factorial design with three variables: solvent composition (10–70% and 30–90% methanol in water for cookies and jams, respectively), solvent-to-solid ratio (10:1–40:1), and ultrasonic probe diameter (2 and 7 mm). The extraction kinetics (5–30 min) were studied to confirm the full recovery of resveratrol from the functional foods. The resveratrol was quantified by Ultrahigh Performance Liquid Chromatography with a Fluorescense Detector (UPLC-FD).     

Microwave absorption properties of 50% SrFe12O19–50% TiO2 nanocomposites with porosity

SrFe₁₂O₁₉–TiO₂ nanocomposites are usually used for absorbing microwaves in military and civil applications. In this work, microwave absorption properties of porous SrFe₁₂O₁₉ nanocomposites with 50% weight ratio of TiO₂ have been investigated. 50% TiO₂–50% SrFe₁₂O₁₉ nanocomposites were prepared by a controlled hydrolysis of titanium tetraisopropoxide in which SrFe₁₂O₁₉ nanoparticles were synthesized by a sol–gel auto combustion route. The morphology, crystalline structure and crystallite size of SrFe₁₂O₁₉–TiO₂ nanocomposites were characterized by field emission scanning electron microscopy and X-ray powder diffraction. The magnetic measurements were carried out with a vibrating sample magnetometer. The microwave absorption was measured by a Vector Network Analyzer. The microwave absorption results indicated that the reflection losses for specimens with 52%–56% porosity and thicknesses of 1.8, 2.1 and 2.6 mm were not very low but minimum reflection loss for a specimen with 4.2 mm thickness reached upto −33 dB.     

Intra-prosthetic breast MR virtual navigation: A preliminary study for a new evaluation of silicone breast implants

ObjectivesTo assess the contribute of intra-prosthetic MRI virtual navigation for evaluating breast implants and detecting implant ruptures.MethodsForty-five breast implants were evaluated by MR examination. Only patients with a clinical indication were assessed. A 1.5-T device equipped with a 4-channel breast coil was used by performing axial TSE-T2, axial silicone-only, axial silicone suppression and sagittal STIR images. The obtained dicom files were also analyzed by using virtual navigation software. Two blinded radiologists evaluated all MR and virtual images. Eight patients for a total of 13 implants underwent surgical replacement. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated for both imaging strategies.ResultsIntra-capsular rupture was diagnosed in 13 out of 45 (29%) implants by using MRI. Basing on virtual navigation, 9 (20%) cases of intra-capsular rupture were diagnosed. Sensitivity, specificity, accuracy, PPV and NPV values of 100%, 86%, 89%, 62% and 100%, respectively, were found for MRI. Virtual navigation increased the previous values up to 100%, 97%, 98%, 89% and 100%.ConclusionIntra-prosthetic breast MR virtual navigation can represent an additional promising tool for the evaluation of breast implants being able to reduce false positives and to provide a more accurate detection of intra-capsular implant rupture signs.     

Interchain interactions effects on emission efficiency of poly(p-phenylene vinylene) films

In attempts to obtain poly(p-phenylene vinylene) (PPV) molecules without intermacromolecular aggregation two strategies were employed: the addition of a strong electrolyte, lithium chloride, to the solution of the precursor, or/and the preparation of solid solutions from co-dissolved precursor and poly(vinyl alcohol) (PVA). The effects on the thermal conversion process of PPV were studied. Complete isolation of the PPV chains was not attained, but a significant degree of chain separation was achieved, as demonstrated by spectroscopic data. The main observations were that strong intermacromolecular forces operate during the PPV elimination step, resulting in simultaneous aggregation with the formation of the final chains. The relative emission efficiency increases up to 115% for PPV and PPV:PVA films when 0.7% and 1.4% of LiCl, respectively, are added and lower conversion temperature (100 °C) procedure is employed. In the case of total annealing procedure (230 °C) the emission efficiency increases 65% for PPV:PVA film with 0.7% of LiCl. For PPV:LiCl films, this parameter decreases substantially (∼11%) when the salt concentration increases above 10%.     

Is gadoxetic acid-enhanced MRI limited in tumor characterization for patients with chronic liver disease?

Purpose

There are pros and cons to the use of gadoxetic acid in hepatocellular carcinoma (HCC) workup due to the potential for high false positive diagnosis. This study was conducted to investigate the preoperative diagnostic performance of gadoxetic acid-enhanced MRI protocol including diffusion-weighted imaging (DWI) with emphasis on tumor characterization developed in high risk HCC patients.

Materials and methods

We included 144 patients (102 men, 42 women; age range 33–74 years) with chronic viral hepatitis or cirrhosis and 183 focal hepatic tumors (size range, 0.4–11.0 cm; mean, 3.2 cm), including 148 HCCs, 13 cholangiocarcinomas, 12 hemangiomas, three hepatocellular adenomas, two focal nodular hyperplasias, and five other tumors. All patients underwent gadoxetic acid-enhanced MRI protocol with DWI. MRIs were independently interpreted by three observers for the detection and characterization of hepatic tumors.

Results

Sensitivities for detecting all 183 liver tumors were 98.4%, 97.8%, and 96.2% for each observer, respectively, with a 97.5% for pooled data. Among 183 hepatic tumors, 91.3% (n = 167), 87.4% (n = 160), and 86.9% (n = 159) were correctly characterized according to their reference standard by each observer, respectively. In 13 cholangiocarcinomas, one to three were misinterpreted as HCC, and the remaining tumors were correctly characterized by each observer. The accuracies (Az) of MRI for HCC diagnosis were 0.952 for observer 1, 0.906 for observer 2, and 0.910 for observer 3, with 0.922 for pooled data. There was good inter-observer agreement.

Conclusion

The gadoxetic acid-enhanced MRI including DWI showed a reasonable performance for tumor characterization with high sensitivity for tumor detection in patients with chronic liver disease, despite concerns of high false positive diagnosis of hypervascular tumors.     

Diagnostic value of breast MRI for predicting metastatic axillary lymph nodes in breast cancer patients: diffusion-weighted MRI and conventional MRI

Purposes

To evaluate the diagnostic value of diffusion-weighted MRI (DWI) and combination of conventional MRI and DWI to predict metastatic axillary lymph nodes in breast cancer.

Materials and methods

Two hundred fifty-two breast cancer patients with 253 axillae were included. The morphological parameters on axial T2-weighted images without fat saturation and apparent diffusion coefficient (ADC) values were retrospectively analyzed. An independent t-test/chi-square test and receiver operating characteristics (ROC) curve analysis were used.

Results

On conventional MRI, short and long axis length, maximal cortical thickness, relative T2 value, loss of fatty hilum (p < 0.001 for each), and eccentric cortical thickening (p < 0.003) were statistically significantly different between the metastatic and nonmetastatic groups. The short axis to long axis ratio was not a statistically significant parameter. The ADC value was significantly different between the 2 groups, with an AUC that was higher than that of conventional MR parameters (AUC, 0.815; threshold, ≤ 0.986 × 10–3 mm²/sec; sensitivity, 75.8%; specificity, 83.9%). Using the adopted thresholds for each parameter, a total number of findings suggesting malignancy of 4 or higher was determined as the threshold, with high specificity (90.1%).

Conclusion

Using conventional MRI and DWI, we can evaluate the axilla in breast cancer with high specificity.     

Neuroprotective effect of agmatine in rats with transient cerebral ischemia using MR imaging and histopathologic evaluation

Purpose

This study aimed to further investigate the effects of agmatine on brain edema in the rats with middle cerebral artery occlusion (MCAO) injury using magnetic resonance imaging (MRI) monitoring and biochemical and histopathologic evaluation.

Materials and methods

Following surgical induction of MCAO for 90 min, agmatine was injected 5 min after beginning of reperfusion and again once daily for the next 3 post-operative days. The events during ischemia and reperfusion were investigated by T2-weighted images (T2WI), serial diffusion-weighted images (DWI), calculated apparent diffusion coefficient (ADC) maps and contrast-enhanced T1-weighted images (CE-T1WI) during 3 h–72 h in a 1.5 T Siemens MAGNETON Avanto Scanner. Lesion volumes were analyzed in a blinded and randomized manner. Triphenyltetrazolium chloride (TTC), Nissl, and Evans Blue stainings were performed at the corresponding sections.

Results

Increased lesion volumes derived from T2WI, DWI, ADC, CE-T1WI, and TTC all were noted at 3 h and peaked at 24 h–48 h after MCAO injury. TTC-derived infarct volumes were not significantly different from the T2WI, DWI-, and CE-T1WI-derived lesion volumes at the last imaging time (72 h) point except for significantly smaller ADC lesions in the MCAO model (P < 0.05). Volumetric calculation based on TTC-derived infarct also correlated significantly stronger to volumetric calculation based on last imaging time point derived on T2WI, DWI or CE-T1WI than ADC (P < 0.05). At the last imaging time point, a significant increase in Evans Blue extravasation and a significant decrease in Nissl-positive cells numbers were noted in the vehicle-treated MCAO injured animals. The lesion volumes derived from T2WI, DWI, CE-T1WI, and Evans blue extravasation as well as the reduced numbers of Nissl-positive cells were all significantly attenuated in the agmatine-treated rats compared with the control ischemia rats (P < 0.05).

Conclusion

Our results suggest that agmatine has neuroprotective effects against brain edema on a reperfusion model after transient cerebral ischemia.     

A row–column addressed micromachined ultrasonic transducer array for surface scanning applications

Row–column addressed arrays for ultrasonic non-destructive testing (NDT) applications are analyzed and demonstrated in this paper. Simulation and experimental results of a row–column addressed 32 by 32 capacitive micromachined ultrasonic transducer (CMUT) array are presented. The CMUT array, which was designed for medical imaging applications, has a center frequency of 5.3 MHz. The CMUT array was used to perform C-scans on test objects with holes that have diameters of 1.0 mm and 0.5 mm. The array transducer has an aperture size of 4.8 mm by 4.8 mm, and it was used to scan an area of 4.0 mm by 4.0 mm. Compared to an N by N fully addressed 2-D array, a row–column addressed array of the same number of elements requires fewer (N instead of N²) pairs of interconnection and supporting electronic components such as pulsers and amplifiers. Even though the resulting field of view is limit by the aperture size, row–column addressed arrays and the row–column addressing scheme can be an alternative option of 2-D arrays for NDT applications.