Proton Density-weighted Images Research Articles

Improved calculation of the equilibrium magnetization of arterial blood in arterial spin labeling.

To propose and assess an improved method for calculating the equilibrium magnetization of arterial blood ( M0a), used for calibration of perfusion estimates in arterial spin labeling. Whereas standard M0a calculation is based on dividing a proton density-weighted image by an average brain-blood partition coefficient, the proposed method exploits partial-volume data to adjust this ratio. The nominator is redefined as the magnetization of perfused tissue, and the denominator is redefined as a weighted sum of tissue-specific partition coefficients. Perfusion data were acquired with a pseudo-continuous arterial spin labeling sequence, and partial-volume data were acquired using a rapid saturation recovery sequence with the same readout module. Results from 7 healthy volunteers were analyzed and compared with the conventional method. The proposed method produced improved M0a homogeneity throughout the brain in all subjects. The mean gray matter perfusion was significantly higher with the proposed method compared with the conventional method: 61.2 versus 56.3 mL/100 g/minute (+8.7%). Although to a lesser degree, the corresponding white matter values were also significantly different: 20.8 versus 22.0 mL/100 g/minute (-5.4%). The spatial and quantitative differences between the 2 methods were similar in all subjects. Compared with the conventional approach, the proposed method produced more homogenous M0a maps, corresponding to a more accurate calibration. The proposed method also yielded significantly different perfusion values across the whole brain, and performed consistently in all subjects. The new M0a method improves quantitative perfusion estimation with arterial spin labeling, and can therefore be of considerable value in perfusion imaging applications.

Early detection of osteoarthritis in rabbits using MRI with a double-contrast agent

BackgroundArticular cartilage degeneration has been evaluated by magnetic resonance imaging (MRI). However, this method has several problems, including its time-consuming nature and the requirement of a high magnetic field or specialized hardware. The purpose of this study was to sequentially assess early degenerative changes in rabbit knee articular cartilage using MRI with a new double-contrast agent.MethodsWe induced osteoarthritis (OA) in the right knee of rabbits by anterior cruciate ligament transection and partial medial meniscectomy. Proton density-weighted images and T2-calculated images were obtained before and after contrast agent injection into the knee. The signal intensity ratio (SIR) values on the proton density-weighted images were calculated by dividing the signal intensity of the articular cartilage by that of joint fluid. Six rabbits were examined using MRI at 2 (designated 2-w OA) and 4 weeks (4-w OA) after the operation. Histological examination was performed 4 weeks after the operation. One rabbit was histologically examined 2 weeks after the operation. The control consisted of six rabbits that were not subjected to the operation. The SIR values, T2 values and the thicknesses of the cartilage of the 2-w OA, 4-w OA and the control before and after contrast agent injection were analyzed. The Mankin score and OARSI (Osteoarthritis Research Society International) score were used for the histological evaluation.ResultsSignificant differences in the SIR and T2 values of the medial and lateral condyles of the femur were found between the control and the 4-w OA only after contrast agent injection. No significant differences were found in the SIR and T2 values before contrast agent injection between the control, the 2-w OA and 4-w OA. The thickness of the articular cartilage revealed no significant differences. In the histological assessment, the Mankin score and OARSI score sequentially increased from the control to the 4-w OA.ConclusionWe evaluated the SIR and T2 values of the knees in a rabbit OA model and a control model using a new double-contrast agent. MRI with this agent enabled OA detection earlier than using conventional MRI.

Usefulness of Sweep Imaging With Fourier Transform for Evaluation of Cortical Bone in Diabetic Rats.

Diabetes decreases bone strength, possibly because of cortical bone changes. Sweep imaging with Fourier transform (SWIFT) has been reported to be useful for cortical bone evaluation. To evaluate cortical bone changes in diabetic rats using SWIFT, assess the usefulness of this technique through comparisons with microcomputed tomography (μCT) and conventional MRI, and clarify the mechanism underlying cortical bone changes using histomorphometry STUDY TYPE: Animal cohort. 8-week-old male Wistar/ST rats (N = 36) were divided into diabetes (induced by streptozotocin injection) and control groups. 7.04T MRI, SWIFT. Six animals from each group were sacrificed at 2, 4, and 8 weeks after injection. Tibial bones were extracted and evaluated using μCT and MRI. The cortical bone mineral density (BMD) was measured using μCT. Proton density-weighted imaging (PDWI) and SWIFT were also performed. The signal-to-noise ratio (SNR) was calculated for each acquisition. The bone formation rate was evaluated using histomorphometry. Findings at each timepoint were compared using Mann-Whitney U-tests. Cortical BMD was significantly lower in the diabetes group than in the control group only at 8 weeks (P < 0.05). At all timepoints, PDWI-SNR showed no significant differences between groups (P = 0.59, 0.70, and 0.82 at 2, 4, and 8 weeks, respectively). SWIFT-SNR was significantly lower in the diabetes group than in the control group (P < 0.05 at 2 and 4 weeks and P < 0.01 at 8 weeks), and the bone formation rate was significantly lower in the diabetes group than in the control group (P < 0.01 for all). SWIFT can detect cortical bone changes even before a decline in the cortical BMD in a diabetic model. 1 Technical Efficacy: Stage 3 J. MAGN. RESON. IMAGING 2018;48:389-397.

Proton density-weighted laryngeal magnetic resonance imaging in systemically dehydrated rats.

Dehydrated vocal folds are inefficient sound generators. Although systemic dehydration of the body is believed to induce vocal fold dehydration, this causative relationship has not been demonstrated in vivo. Here we investigate the feasibility of using in vivo proton density (PD)-weighted magnetic resonance imaging (MRI) to demonstrate hydration changes in vocal fold tissue following systemic dehydration in rats. Animal study. Sprague-Dawley rats (n = 10) were imaged at baseline and following a 10% reduction in body weight secondary to withholding water. In vivo, high-field (7 T), PD-weighted MRI was used to successfully resolve vocal fold and salivary gland tissue structures. Normalized signal intensities within the vocal fold decreased postdehydration by an average of 11.38% ± 3.95% (mean ± standard error of the mean [SEM], P = .0098) as compared to predehydration levels. The salivary glands experienced a similar decrease in normalized signal intensity by an average of 10.74% ± 4.14% (mean ± SEM, P = .0195) following dehydration. The correlation coefficient (percent change from dehydration) between vocal folds and salivary glands was 0.7145 (P = .0202). Ten percent systemic dehydration induced vocal fold dehydration as assessed by PD-weighted MRI. Changes in the hydration state of vocal fold tissue were highly correlated with that of the salivary glands in dehydrated rats in vivo. These preliminary findings demonstrate the feasibility of using PD-weighted MRI to quantify hydration states of the vocal folds and lay the foundation for further studies that explore more routine and realistic magnitudes of systemic dehydration and rehydration. NA. Laryngoscope, 128:E222-E227, 2018.

Does Prevalence of Small Size Acetabular Bone Marrow Edema or Cystic Lesion on 3 Tesla MRI Correlate With Poor Clinical Outcomes After Hip Arthroscopy? An Analysis of 2 to 6 Year Follow-Up

There were no significant differences between subchondral change (SC, bone marrow edema or cyst) group and non-SC group regarding postoperative clinical outcomes. Significantly higher conversion rate to total hip replacement (THR) was seen in patients with large (>= 15.3 mm) SC of the acetabulum measured preoperatively with 3T-MRI. Conversely, patients with small SC had no conversion to THR. Presence of acetabular subchondral changes (SC) such as bone marrow edema (BME) or cystic lesion (CL) has been reported to correlate with poor prognosis after hip arthroscopy. To determine if acetabular SC (BME or CL) size, measured on 3-Tesla MRI (3T-MRI) correlates with poor clinical outcomes and higher failure rates in patients undergoing hip arthroscopy for the treatment of intraarticular pathologies. Patients older than 30 years old who underwent primary hip arthroscopic surgery for intraarticular pathology by an experienced hip surgeon between 2010 and 2012 were enrolled in this study. Patients younger than 30 year-old, with a history of avascular necrosis of the hip or the other pathologies, with follow-up of less than 2 years were excluded. Images from a single 3T-MRI were examined using a defined protocol. The prevalence of SC was evaluated using proton density-weighted MR image with chemical fat saturation by two blinded reviewers. Clinical outcomes were collected, including conversion to total hip replacement (THR), patient recorded outcomes (MHHS, WOMAC, HOS-ADL, HOS-Sports) and patient satisfaction. Statistical analysis was performed using Mann-Whitney U-test or Fisher’s exact test, p < 0.05 was defined as significant. The cut-off value was calculated using receiver operating characteristic (ROC) curve analysis. One hundred and forty-two patients were included. Patients had a mean follow-up of 3.4 years (range, 2.0 to 5.9). Fifty patients (35%) had BME or CL in the preoperative 3T-MRI (SC group). SC was found more frequently in male subjects than female (SC group v non-SC group, percent male, 70% v 47%, p < 0,01). The median age of SC group was significantly higher than that of non-SC group (45 years v 42 years, p < 0.05). There were no significant differences between SC and non-SC group regarding rate of conversion to THR (8% v 3%, p = 0.198) postoperative MHHS, WOMAC, HOS-ADL, HOS-Sports or patient satisfaction (p > 0.05). Regarding the characteristics of SC, we found 23 patients with BME and 27 patients with CL. Postoperative outcomes (WOMAC, HOS-ADL, HOS-Sports) of patients with BME was significantly worse comparing to those with CL (p < 0.05) The ROC curve analysis identified 15.3 mm of SC size as the cut-off value. A greater SC than the cut-off value was found in 17 patients from which four (24%) were converted to THR (p < 0.01) while patients with SC measuring less than 15.3 mm had no conversion to THR. There were no significant differences between SC group and non-SC group regarding postoperative clinical outcomes. Significantly higher conversion rate to THR was seen in patients with large (>= 15.3 mm) SC of the acetabulum measured preoperatively with 3T-MRI. Conversely, patients with small SC had no conversion to THR. These findings suggest the possible indication of hip arthroscopy for patients with small size acetabular SC especially cyst.

MR imaging of flexor tendon and pulley system of the fingers: normal anatomy and injury

Objective: To explore the magnetic resonance imaging (MRI) features of the anatomy and injuries of flexor tendon and pulley system of the fingers. Methods: Clinical and imaging data of 20 healthy volunteers without injuries and 36 patients from Beijing Jishuitan Hospital with flexor tendon and pulley system injuries in the fingers between March 2013 and March 2016 were retrospectively analyzed. All subjects underwent magnetic resonance imaging (MRI) examination. The MRI findings of patients were compared with healthy volunteers. In addition, imaging findings of patients were compared with the surgical results and confirmed by double-blinded method. Results: Twenty volunteers without flexor tendon and pulley system injures showed homogeneous hypointensity on both T1-weighted and Proton Density-weighted images with fat saturation (PD-FS). There were 36 patients with finger injures, including 21 cases of flexor tendon injury, 10 cases of pulley system injury, 5 cases of compound injury, which demonstrated unclear signal, discontinuity on T1-weighted images and heterogeneously increased signal intensity of the involved structures on PD-FS images. Edema was detected in the soft tissues surrounding the injured sites. Conclusions: MRI is an accurate method for evaluation of the anatomy and pathologic conditions of flexor tendon and pulley system of the fingers and a useful tool for diagnosis and treatment of flexor tendon and pulley system injuries.

Uncommon presentation of a rare tumour - incidental finding in an asymptomatic patient: case report and comprehensive review of the literature on intrapericardial solitary fibrous tumours

BackgroundA solitary fibrous tumour is a rare, mainly benign spindle cell mesenchymal tumour most commonly originating from the pleura. An intrapericardial location of a solitary fibrous tumour is extremely unusual. We present a case of an asymptomatic patient with a slow-growing massive benign cardiac solitary fibrous tumour.Case presentationA 37-year-old asymptomatic female patient was referred to our hospital with an enlarged cardiac silhouette found on her screening chest X-ray. The echocardiographic examination revealed pericardial effusion and an inhomogeneous mobile mass located in the pericardial sac around the left ventricle. Cardiac magnetic resonance (MRI) examination showed an intrapericardial, semilunar-shaped mass attached to the pulmonary trunk with an intermediate signal intensity on proton density-weighted images and high signal intensity on T2-weighted spectral fat saturation inversion recovery images. First-pass perfusion and early and late gadolinium-enhanced images showed a vascularized mass with septated, patchy, inhomogeneous late enhancement. Coronary computed tomography angiography revealed no invasion of the coronaries. Based on the retrospectively analysed screening chest X-rays, the mass had started to form at least 7 years earlier. Complete resection of the tumour with partial resection of the pulmonary trunk was performed. Histological evaluation of the septated, cystic mass revealed tumour cells forming an irregular patternless pattern; immunohistochemically, the cells tested positive for vimentin, CD34, CD99 and STAT6 but negative for keratin (AE1-AE3), CD31 and S100. Thus, the diagnosis of an intrapericardial solitary fibrous tumour was established. There has been no recurrence for 3 years based on the regular MRI follow-up.ConclusionIntrapericardial SFTs, showing slow growth dynamics, can present with massive extent even in completely asymptomatic patients. MRI is exceedingly useful for characterizing intrapericardial masses, allowing precise surgical planning, and is reliable for long-term follow up.

Bone morphological factors influencing cartilage degeneration in the knee

Objectives: Morphological features of the distal femur and proximal tibia associated with cartilage degeneration are unknown. This study aimed to elucidate local anatomical parameters of the knee which correlate with articular cartilage degeneration using MRI T1ρ mapping.Methods: This study involved 200 subjects with knee pain (mean age, 48.7 years; range, 14–80 years) with no severe osteoarthritic changes on plain X-ray. T1ρ values were measured in the regions of interest on the surface layer of the cartilage on mid-coronal images of the femorotibial joint. Assessment of medial and lateral posterior tibial slope (MTS, LTS) and medial and lateral femoral condylar offset ratio (MFCOR, LFCOR) was performed using sagittal proton density-weighted imaging. Morphological assessment of posterior root and horn of menisci was also performed according to a modified Whole Organ Magnetic Resonance Imaging Score (WORMS) of the knee.Results: Multiple regression analysis revealed that a decrease in MTS was associated with increased T1ρ values in the medial tibia, independent of age, osteoarthritic changes on plain X-ray, femur-tibia angle (FTA), and posterior medial meniscal lesions.Conclusions: Shallow MTS correlates with cartilage degeneration in symptomatic patients. This parameter could help in understanding the etiology of osteoarthritis in the early stage. Future kinematic studies will be needed to confirm our findings.

The diagnostic accuracy of magnetic resonance imaging for anterior cruciate ligament injury in comparison to arthroscopy: a meta-analysis

We performed this meta-analysis to examine the diagnostic accuracy of MRI for the diagnosis of anterior cruciate ligament (ACL) injury in comparison to arthroscopy. We also compared the diagnostic accuracy of MRI with magnetic field intensities (MFI) greater than or equal to 1.5T with those below 1.5T, in addition to different MRI sequences. Studies relevant to the diagnosis of ACL injury by MRI and arthroscopy were analyzed. Computer and manual retrieval were carried out on studies published between January 1, 2006 and May 31, 2016. Twenty-one papers were included. Neither threshold nor non-threshold effects were present (p = 0.40, p = 0.06). The pooled sensitivity (SE), specificity (SP), positive likelihood ratio (LR+), negative likelihood ratio (LR−) and diagnostic odds ratio (DOR) with 95% confidence interval (CI) were 87% (84–90%), 90% (88–92%), 6.78 (4.87–9.44), 0.16 (0.13–0.20) and 44.70 (32.34–61.79), respectively. The area under the curve (AUC) was 0.93. The risk of publication bias was negligible (p = 0.75). In conclusion, examination by MRI is able to provide appreciable diagnostic performance. However, the principle, which states that the higher the MFI, the better the diagnostic accuracy, could not be verified. Additionally, conventional sequences (CSs) associated with proton density-weighted imaging (PDWI) are only slightly better than CSs alone, but not statistically different.

Quantification of Artifacts in MR Images Caused by Commonly Used Dental Materials

Background: Although new approaches for application of magnetic resonance imaging (MRI) in dentistry have been promising, the presence of dental materials in the oral cavity represents a major obstacle to generating quality MRI data. The resulting artifacts can adversely affect diagnostic accuracy of oral and maxillofacial conditions. Objectives: This study aimed to detect and assess artifacts caused by metallic and non-metallic dental materials in MR images. Materials and Methods: Nineteen commonly used dental materials were used in an in vitro assay. An empty cube-shaped phantom with internal dimensions of 15 × 15 × 15 cm3 was fabricated of polyester and filled with paraffin or distilled water to create optimal contrast for T1-weighted (T1W; for anatomical structures), T2-weighted (T2W, for pathological conditions) and proton density-weighted (PDW) MR images. Dental material samples were manufactured and placed at the center of the mold using polyester tubes. All samples were then subjected to MRI using two-dimensional (2D) and three-dimensional (3D) T1W, T2W and PDW imaging sequences. The data were subjected to one-way analysis of variance (ANOVA) followed by mean comparison using the Tukey’s test. Results: Comparison of mean artifact size in 2D and 3D images showed that ceramic caused the smallest (189.48 mm3) and orthodontic metal brackets caused the largest (4307.5 mm3) artifact areas. Assessment of the amount of artifacts created in different imaging sequences revealed minimal artifact in inversion recovery sequence and maximum artifact in gradient echo sequence of the amount of artifacts at different weighing times in 2D and 3D images showed minimal artifacts in PDW and maximum artifacts in T2W. Conclusion: Bracket, titanium implants, and the nickel-chromium (Ni-Cr) materials are the three most susceptible materials to external B0 magnetic field; thus creating huge metal-induced artifacts. The Siemens default two dimensional turbo spin echo (2D-TSE), 2D-BLADE, three dimensional volumetric interpolated breath-hold examination (3D-VIBE) and three dimensional sampling perfection with application optimized contrasts using different flip angle evolution (3D-SPACE) are the most appropriate pulse sequences for the 2D-T1W, 2D-T2W, 3D-T1W, and 3D-T2W evaluations of the bracket/titanium /Ni-Cr materials, respectively. The rest of the materials’ magnetic susceptibility effects are negligible, and artifacts are small.

High-resolution 3T Magnetic Resonance Imaging of the Triangular Fibrocartilage Complex in Chinese Wrists: Correlation with Cross-sectional Anatomy.

Background:The injury of the triangular fibrocartilage complex (TFCC) is a common cause of ulnar-sided wrist pain. The aim of this study was to investigate if the high-resolution 3T magnetic resonance imaging (MRI) could demonstrate the detailed complex anatomy of TFCC in Chinese.Methods:Fourteen Chinese cadaveric wrists (from four men and three women; age range at death from 30 to 60 years; mean age at 46 years) and forty healthy Chinese wrists (from 20 healthy volunteers, male/female: 10/10; age range from 21 to 53 years with a mean age of 32 years) in Beijing Jishuitan Hospital from March 2014 to March 2016 were included in this study. All cadavers and volunteers had magnetic resonance (MR) examination of the wrist with coronal T1-weighted and proton density-weighted imaging with fat suppression in three planes, respectively. MR arthrography (MRAr) was performed on one of the cadaveric wrists. Subsequently, all 14 cadaveric wrists were sliced into 2 mm thick slab with band saw (six in coronal plane, four in sagittal plane, and four in axial plane). The MRI features of normal TFCC were analyzed in these specimens and forty healthy wrists.Results:Triangular fibrocartilage, the ulnar collateral ligament, and the meniscal homolog could be best observed on images in coronal plane. The palmar and dorsal radioulnar ligaments were best evaluated in transverse plane. The ulnotriquetral and ulnolunate ligaments were best visualized in sagittal plane. The latter two structures and the volar and dorsal capsules were better demonstrated on MRAr.Conclusion:High-resolution 3T MRI is capable to show the detailed complex anatomy of the TFCC and can provide valuable information for the clinical diagnosis in Chinese.

Noninvasive detection of matrix metalloproteinase-9 in atherosclerotic lesions using technetium-99m-labeled single-photon emission computed tomography in vivo

Previous studies have suggested that matrix metalloproteinase (MMP) inhibitor uptake may offer a precise estimation of MMP activity in atherosclerotic lesions. In this study, we explored the feasibility of noninvasive detection of MMP-9 activity using technetium-99m-labeled matrix metalloproteinase-9 antibody (Tc-McAb) in vivo. ApoE-deficient (ApoE) atherosclerosis mice models (n=10) were induced through a high-cholesterol diet following ligation of their left common carotid artery. After 4 weeks, the models were verified through proton density-weighted and T2-weighted images obtained by MRI. C57BL/6 sham mice (n=8) were used as controls. In addition, normal mice (n=20) were used to characterize blood clearance. After radiolabeled McAb administration, single-photon emission computed tomography (SPECT) was performed. Subsequently, left common carotid arteries were harvested for ex-vivo autoradiograph imaging. Then, morphology and activity assays of MMP-9 were histologically and immunohistochemically examined. MRI showed higher signal intensities in the left common carotid arteries with irregular stenoses in the lumen of blood vessels in atherosclerosis mice models in vivo. Atherosclerotic lesions on left common carotid artery specimens were also clearly visualized using SPECT 2 h after Tc-McAb administration in vivo. Note that the radiochemistry purity of the Tc-McAb used was 85-95%. Biodistribution studies have shown that the clearance of Tc-McAb from blood was rapid. In addition, atherosclerotic lesions were clearly visualized on radioautography film shadows ex vivo. MMP-9 activities within the atherosclerotic lesions were noninvasively detected using Tc-labeled SPECT in vivo.

Depressive disorder may be associated with raphe nuclei lesions in patients with brainstem infarction

BackgroundDepression is a common symptom after stroke, but its neural substrates remain unclear. The ascending serotonergic system originates from the raphe nuclei in the brainstem. We hypothesized that depressive disorder due to brainstem infarction is associated with damage to the raphe nuclei. MethodsWe prospectively enrolled 19 patients who had the first-ever acute isolated brainstem infarction in an observational cross-sectional study. All patients were evaluated by using the Montgomery Åsberg Depression Rating Scale (MADRS), the clinician-rated version of Apathy Evaluation Scale (AES-C) and Mini-Mental State Examination (MMSE). Depressive disorder was diagnosed according to DSM-5 and MADRS score of 12 or greater. Diffusion tensor imaging and proton density-weighted images were used to identify damage in the raphe nuclei. Accordingly, patients were classified into either the raphe-nuclei–damaged or intact group. Prevalence of depressive disorder and the MADRS, AES-C, and MMSE scores were compared between the two groups. ResultsDepressive disorder was more frequent in the damaged group (n=6) than in the intact group (n=13) (83% vs. 15%; P=0.01). MADRS scores were higher in the damaged group than in the intact group (mean±1 SD, 17.5±7.9 vs. 7.0±4.4; P=0.002), whereas the AES-C and MMSE scores did not differ between groups. LimitationsWe did not assess the damage to the ascending projection fibers from the raphe nuclei. ConclusionsOur results suggest that damage to the raphe nuclei underlies depressive disorder due to brainstem infarction, possibly via serotonergic denervation.

Numerical and Visual Evaluation of Compressed Sensing MRI Using 3D Cartesian Sampling

We performed numerical and visual evaluation of compressed sensing MRI (CS-MRI) using 3D Cartesian sampling by numerical simulation. Three brain anatomical ROIs (white matter, gray matter, cerebrospinal fluid) of a T1-weighted image (T1WI), a T2-weighted image (T2WI) and a proton density-weighted image (PDWI) were used for numerical evaluation. Sampling ratio of the Cartesian grid was 30%. Reconstruction was performed by the projection onto convex sets (POCS) method with soft thresholding, subject to data fidelity constraints. In the absence of noise, RMSE of 3D-T1WI was 1.50, ant that of the 2D-T1WI of the transverse plane was in the range of 1.06 to 1.54; anatomical ROIs was in the range of 0.75 to 2.80; those of T2WI were 3.20, 2.77 to 3.06, and 1.81 to 4.51; those of PDWI were 1.69, 1.33 to 1.49, and 1.08 to 1.86. Visual evaluation was performed by three radiologists on the basis of three categories: artifact, anatomical structure, and tissue contrast. Average score of the visual evaluation indicated that anatomical structure and tissue contrast of CS images were equal to those of the original image, although a few artifacts were visible. If noise level was assumed to be 20 dB or less, anatomical structure and tissue contrast were not significantly degraded compared to noise-free CS images.

Numerical and Visual Evaluations of Compressed Sensing MRI Using 2D Radial Sampling

Two-dimensional radial MRI using compressed sensing (2D radial CS) enables incoherence sampling in k space unlike conventional Cartesian MRI, however 2D radial CS has not been sufficiently investigated. Numerical and visual evaluations of 2D radial CS were performed in this paper. Three brain anatomical ROIs (white matter, gray matter, cerebrospinal fluid) of a T1-weigthted image (T1WI), a T2-weighted image (T2WI) and a proton density-weighted image (PDWI) were used for the numerical evaluation. The Brainweb MRI Data Base was used for test images. Projection of 80 spokes with linear sampling of 256 pixels was used. Reconstruction was performed by minimizing the L1 norm of a transformed image using wavelet transform and spatial finite-differences (total variation), subject to data fidelity constraint. In the absence of noise, the root mean square error (RMSE) of T1WI was in the range of 3.75 to 5.05; that of the anatomical region of interests (ROIs) was in the range of 1.54 to 10.24; those of T2WI were 8.75 to 11.65 and 4.31 to 6.99; and those of PDWI were 3.44 to 4.46 and 1.34 to 3.09. Visual evaluation was performed by three radiologists on the basis of three categories: artifact, anatomical structure, and tissue contrast. Average percent scores of the visual evaluation were 96% for T1WI, 74-81% for T2WI, and 81-89% for PDWI.

RETRACTED ARTICLE: Hermite-based texture feature extraction for classification of humeral head in proton density-weighted MR images

The objective of this research is to develop a computer-based diagnosis system which is capable of recognizing normal and edematous humeral head images by using texture features derived from Hermite transform. The performance of Hermite-based texture features in classification of humeral bone was compared with curvelet, contourlet and gray level co-occurrence matrix-based texture feature descriptors. To measure the performance of the extracted features, we deployed MLP (multilayer perceptron), SVM (support vector machine) and KNN (K-nearest neighbors) methods and demonstrated their power in differentiating the normal and abnormal regions. The proposed approach was tested on our own dataset which consists of 79 normal and 91 edematous humeral heads in PD (proton density)-weighted MR (magnetic resonance) images. The highest classification accuracy of Hermite-based method was 98.23% by MLP. In most cases, Hermite-based texture features surpassed the results of other proposed methods under all of the three classifiers. Our results suggest that the proposed system is a promising tool for classification of edematous and normal bone from PD-weighted MR images. This study is unique in the literature of using PD-weighted MR images and Hermite transform to classify bone edema .

Lumen segmentation in magnetic resonance images of the carotid artery

Investigation of the carotid artery plays an important role in the diagnosis of cerebrovascular events. Segmentation of the lumen and vessel wall in Magnetic Resonance (MR) images is the first step towards evaluating any possible cardiovascular diseases like atherosclerosis. However, the automatic segmentation of the lumen is still a challenge due to the low quality of the images and the presence of other elements such as stenosis and malformations that compromise the accuracy of the results. In this article, a method to identify the location of the lumen without user interaction is presented. The proposed method uses the modified mean roundness to calculate the circularity index of the regions identified by the K-means algorithm and return the one with the maximum value, i.e. the potential lumen region. Then, an active contour is employed to refine the boundary of this region. The method achieved an average Dice coefficient of 0.78±0.14 and 0.61±0.21 in 181 3D-T1-weighted and 181 proton density-weighted MR images, respectively. The results show that this method is promising for the correct identification and location of the lumen even in images corrupted by noise.

Can MRI Distinguish between a Partial Anterior Cruciate Ligament (ACL) Tear and a Normal ACL?

Objective: The purpose of this study was to determine whether Magnetic resonance imaging (MRI) can distinguish between a partial anterior cruciate ligament (ACL) tear and a normal ACL. Materials and Methods: MR images of 20 patients with an arthroscopically confirmed partial ACL tear were retrospectively interpreted by the author, comparing with normal ACLs. Results and Discussion: All knees with a partial ACL tear had a continuous band of low signal, of which 15 had no increased signal intensity on proton density-weighted images. MRI could not distinguish between a partial ACL tear and a normal ACL. Orthopedic surgeons had better consider an ACL tear when a patient has traumatic hemarthrosis or anxiety provoked by the sensation of the knee ‘going out’ or ‘giving way’ during the pivot shift test, even if the ACL has a continuous band of low signal on the oblique sagittal view on MRI.

Magnetic Resonance Venous Volume Measurements in Peripheral Artery Disease (from ELIMIT)

The relation between the arterial and venous systems in patients with impaired lower extremity blood flow remains poorly described. The objective of this secondary analysis of the Effectiveness of Intensive Lipid Modification Medication in Preventing the Progression on Peripheral Artery Disease Trial was to determine the association between femoral vein (FV) volumes and measurements of peripheral artery disease. FV wall, lumen, and total volumes were quantified with fast spin-echo proton density-weighted magnetic resonance imaging scans in 79 patients with peripheral artery disease over 2 years. Reproducibility was excellent for FV total vessel (intraclass correlation coefficient 0.924, confidence interval 0.910 to 0.935) and lumen volumes (intraclass correlation coefficient 0.893, confidence interval 0.873 to 0.910). Baseline superficial femoral artery volumes were directly associatedwith FV wall (r= 0.46, p <0.0001), lumen (r= 0.42, p=0.0001),and totalvolumes (r=0.46, p <0.0001). The 2-year change in maximum walking time was inversely associated with the 24-month change in FV total volume (r=-0.45, p= 0.03). Inconclusion, FV volumes can be measured reliably with fast spin-echo proton density-weighted magnetic resonance imaging, and baseline superficial femoral artery plaque burden is positively associated with FV volumes, whereas the 2-year change in FV volumes and leg function show an inverse relation.

Impact of attenuation correction on clinical [(18)F]FDG brain PET in combined PET/MRI.

BackgroundIn PET/MRI, linear photon attenuation coefficients for attenuation correction (AC) cannot be directly derived, and cortical bone is, so far, usually not considered. This results in an underestimation of the average PET signal in PET/MRI. Recently introduced MR-AC methods predicting bone information from anatomic MRI or proton density-weighted zero-time imaging may solve this problem in the future. However, there is an ongoing debate if the current error is acceptable for clinical use and/or research.MethodsWe examined this feature for [18F] fluorodeoxyglucose (FDG) brain PET in 13 patients with clinical signs of dementia or movement disorders who subsequently underwent PET/CT and PET/MRI on the same day. Multiple MR-AC approaches including a CT-derived AC were applied.ResultsThe resulting PET data was compared to the CT-derived standard regarding the quantification error and its clinical impact. On a quantitative level, −11.9 to +2 % deviations from the CT-AC standard were found. These deviations, however, did not translate into a systematic diagnostic error. This, as overall patterns of hypometabolism (which are decisive for clinical diagnostics), remained largely unchanged.ConclusionsDespite a quantitative error by the omission of bone in MR-AC, clinical quality of brain [18F]FDG is not relevantly affected. Thus, brain [18F]FDG PET can already, even now with suboptimal MR-AC, be utilized for clinical routine purposes, even though the MR-AC warrants improvement.