An automated liver segmentation in liver iron concentration map using fuzzy c-means clustering combined with anatomical landmark data

Background

To estimate median liver iron concentration (LIC) calculated from magnetic resonance imaging, excluded vessels of the liver parenchyma region were defined manually. Previous works proposed the automated method for excluding vessels from the liver region. However, only user-defined liver region remained a manual process. Therefore, this work aimed to develop an automated liver region segmentation technique to automate the whole process of median LIC calculation.

Methods

553 MR examinations from 471 thalassemia major patients were used in this study. LIC maps (in mg/g dry weight) were calculated and used as the input of segmentation procedures. Anatomical landmark data were detected and used to restrict ROI. After that, the liver region was segmented using fuzzy c-means clustering and reduced segmentation errors by morphological processes. According to the clinical application, erosion with a suitable size of the structuring element was applied to reduce the segmented liver region to avoid uncertainty around the edge of the liver. The segmentation results were evaluated by comparing with manual segmentation performed by a board-certified radiologist.

Results

The proposed method was able to produce a good grade output in approximately 81% of all data. Approximately 11% of all data required an easy modification step. The rest of the output, approximately 8%, was an unsuccessful grade and required manual intervention by a user. For the evaluation matrices, percent dice similarity coefficient (%DSC) was in the range 86–92, percent Jaccard index (%JC) was 78–86, and Hausdorff distance (H) was 14–28 mm, respectively. In this study, percent false positive (%FP) and percent false negative (%FN) were applied to evaluate under- and over-segmentation that other evaluation matrices could not handle. The average of operation times could be reduced from 10 s per case using traditional method, to 1.5 s per case using our proposed method.

Conclusion

The experimental results showed that the proposed method provided an effective automated liver segmentation technique, which can be applied clinically for automated median LIC calculation in thalassemia major patients.

Evaluation of the degenerative pattern of PCL in osteoarthritis patients using UTE-T2 mapping

Background

The posterior cruciate ligament (PCL) is one of the essential stabilizers of the knee joint and it was demonstrated that its degenerative change related to the knee osteoarthritis (OA). We aimed to evaluate signal of the PCL in OA patients in comparison with healthy young and elderly volunteers using the ultra-short echo timeenhanced (UTE)-T2∗ mapping, and to validate these findings with histology.

Methods

Thirty asymptomatic volunteers, 13 young people (younger group) and 17 elderly people (elder group), and 27 patients who had undergone total knee arthroplasty (OA group) were enrolled in this study. UTE-T2∗ maps of PCL were obtained from all participants. The PCL was divided into proximal, middle, and distal parts and the UTET2∗ values obtained from each part were compared among the groups. In OA group, the sacrificed PCLs were evaluated histologically in each part corresponding to the part of UTE-T2∗ maps and compared.

Results

The UTE-T2∗ values in OA group were significantly higher than those in other groups except in distal part. In elder group, the UTE-T2∗ values were significantly higher than those in younger group only in the proximal part. Moreover, in OA group, the UTE-T2∗ values in proximal and middle parts were significantly higher than those in distal part. There was a moderate correlation between the UTE-T2∗ values and histological scores.

Conclusions

The specific signal intensity pattern of the PCL in patients with OA was demonstrated using UTE-T2∗ mapping, and these findings were related to histological degenerated status of the PCL.

Giant "heart appearance-like sign" on MRI in bilateral ponto-medullary junction infraction: case report

Background

Bilateral medial medullary infarction (MMI) is uncommon and bilateral medial pons infarction (MPI) is even rarer. “Heart appearance” on magnetic resonance imaging (MRI) is a characteristic presentation of bilateral medial medullary infarction (MMI).

Case presentation

We present 67-year-old Chinese diabetic and hypertensive female patient affected with “heart appearance-like” infarction in bilateral ponto-medullary junction on MRI. Abnormal signal was observed in the bilateral ponto-medullary junction on T1, T2, fluid-attenuated inversion recovery and apparent diffusion coefficient (ADC). The whole brain digital subtraction angiography (DSA) showed the basilar artery and vertebral artery remained intact. Therefore, we speculated that the bilateral ponto-medullary junction infarction might be caused by the deep perforating branch of the basilar artery.

Conclusions

As far as we know, the “heart appearance-like” infraction in bilateral ponto-medullary junction was not reported. Our case also suggests that bilateral ischemic infraction involvement of the medulla and pon is possible even in the context of an intact basilar artery.

The morphology of proximal tibiofibular joint (PTFJ) predicts incident radiographic osteoarthritis: data from Osteoarthritis Initiative

OBJECTIVE

To determine whether the morphology of proximal tibiofibular joint (PTFJ) is associated with increased risk of incident radiographic osteoarthritis (iROA) over 4 years in the OA Initiative (OAI) study.

METHODS

A nested matched case-control study design was used to select participants from OAI study. Case knees were defined as those with iROA. Control knees were matched one-to-one by sex, age and radiographic status with case knees. T2-weighted MR images were assessed at P0 (the visit when incident ROA was found on radiograph), P1 (1 year prior to P0) and at OAI baseline. The contacting area of PTFJ (S) and its projection areas onto the horizontal (load-bearing area, Sτ), sagittal (lateral stress-bolstering area, Sφ) and coronal plane (posterior stress-bolstering area, Sυ) were assessed, respectively.

RESULTS

354 case knees and 354 matched control knees were included, with a mean age of 60 and a mean body mass index (BMI) of 28 kg/m². Baseline PTFJ morphological parameters (S, Sτ and Sυ) were significantly associated with iROA over 4 years, and these associations remained unchanged after adjustment for BMI, number of knee bending activities, self-reported knee injury and surgery. S, Sτ and Sυ were also significantly associated with iROA at P1 and P0. In subgroup analysed, S, Sτ and Sυ were associated with risks of incident joint space narrowing in the medial, but not the lateral tibiofemoral compartment.

CONCLUSION

Greater contacting area, load-bearing area and posterior stress-bolstering area of PTFJ were associated with increased risks of iROA, largely in the medial tibiofemoral compartment.

Data on MRI brain lesion segmentation using K-means and Gaussian Mixture Model-Expectation Maximization

The data in this article provide details about MRI lesion segmentation using K-means and Gaussian Mixture Model-Expectation Maximization (GMM-EM) algorithms. Both K-means and GMM-EM algorithms can segment lesion area from the rest of brain MRI automatically. The performance metrics (accuracy, sensitivity, specificity, false positive rate, misclassification rate) were estimated for the algorithms and there was no significant difference between K-means and GMM-EM. In addition, lesion size does not affect the accuracy and sensitivity for either method.

MRI and Bone Scintigraphy for Breast Cancer Bone Metastase: A Meta-analysis

Objective

The aim of this study was to compare the diagnostic value of magnetic resonance image (MRI) and bone scintigraphy (BS) in the diagnosis of breast cancer bone metastases.

Methods

Searching in the databases including PubMed, Embase about the comparative study of MRI and bone scintigraphy in the diagnosis of breast cancer bone metastases during 2000~2018. After we screened further, the extracted effective data were calculated by Meta-Disc 1.4 software.

Results

We obtained 4 articles. The pooled estimates for sensitivity of MRI, BS were 0.99 (95% CI, [0.95, 1.00]) and 0.93 (95% CI, [0.88, 0.97]) respectively; For specificity were 0.99 (95% CI, [0.95, 1.00]) and 0.86 (95% CI, [0.79, 0.92]) respectively. The AUC of SROC curve for MRI and BS were 0.9948 and 0.9675 respectively.

Conclusion

MRI remains to be a satisfactory method for the diagnosis of breast cancer bone metastases and should first be considered for patients.

Reversible splenial lesion syndrome in children: Retrospective study and summary of case series

OBJECTIVE

To describe clinical features of reversible splenial lesion syndrome (RESLES) in children.

METHODS

Retrospectively analyzed clinical features of RESLES in children and compared differences between severe and non-severe group, classified by clinical global impression-scale; summarized clinical features of children with mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) from case series.

RESULTS

16 episodes of RESLES occurring in 15 Chinese children were analyzed, with 13 episodes having MERS and 3 episodes with epilepsy. 10 episodes were associated with various pathogens including rotavirus (n=5), adenovirus (n=1), influenza A (n=1), mycoplasma (n=2), and jejunum campylobacter (n=1). The common neurological symptoms included seizure, behavioral changes, altered consciousness and motor deterioration. The lesions of splenium of corpus callosum (SCC), extra-SCC (n=2) or extra-CC (n=1) showed T2-weight and FLAIR hyper-intensity, with the corresponding reduced diffusion. All had complete resolution of radiological changes except 1 episode with small residual. 8 episodes had EEG abnormalities, while elevated white blood count, increased hs-CRP, and hyponatremia were commonly revealed. 7 episodes were given steroid plus therapy, while 3 episodes were treated with antiepileptic drugs. Compared with non-severe group, the number of patients with altered consciousness, EEG abnormalities, motor deterioration, or extra-SCC lesions in severe group was significantly increased. The patients in severe group tended to need longer hospital stay interval. No case caused neurological sequelae, except 1 patient in severe group with recurrent episode and extra-CC lesions having intellectual disability (ID). Five pediatric MERS case series were summarized, including 67 episodes (40 male and 27 female; age ranging 10 m∼13y) from 65 patients, with 33 episodes in Japan, 27 in China, and 7 in Caucasian Australian children, and all patients have a good prognosis except 1 patient with ID (current study).

CONCLUSION

Although RESLES in children tend to be a good outcome, the prognosis of patient in severe group, especially with extra-CC lesions, might have neurological sequelae.

Automatic cardiac T2* relaxation time estimation from magnetic resonance images using region growing method with automatically initialized seed points

BACKGROUND AND OBJECTIVE

Heart failure due to iron-overload cardiomyopathy is one of the main causes of mortality. The cardiomyopathy is reversible if intensive iron chelation treatment is done in time, but the diagnosis is often delayed because the cardiac iron deposition is unpredictable and the symptoms are lately detected. There are many ways to assess iron-overload. However, the widely used and approved method is by using MRI which is performed by calculating the T2* (T2-star). In order to compute the T2* value, the region of interest (ROI) is manually selected by an expert which may require considerable time and skills. The aim of this work is hence to develop the cardiac T2* measurement by using region growing algorithm for automatically segmenting the ROI in cardiac MR images. Mathematical morphologies are also used to reduce some errors.

METHODS

Thirty MR images with free-breathing and respiratory-trigger technique were used in this work. The segmentation algorithm yields good results when compared with the manual segmentation performed by two experts.

RESULTS

The averages of positive predictive value, the sensitivity, the Hausdorff distance, and the Dice similarity coefficient are 0.76, 0.84, 7.78 pixels, and 0.80 when compared with the two experts' opinions. The T2* values were carried out based on the automatically segmented ROI's. The mean difference of T2* values between the proposed technique and the experts' opinion is about 1.40ms.

CONCLUSIONS

The results demonstrate the accuracy of the proposed method in T2* value estimation. Some previous methods were implemented for comparisons. The results show that the proposed method yields better segmentation and T2* value estimation performances.

Simulation verification of SNR and parallel imaging improvements by ICE-decoupled loop array in MRI

Transmit/receive L/C loop arrays with the induced current elimination (ICE) or magnetic wall decoupling method has shown high signal-to-noise (SNR) and excellent parallel imaging ability for MR imaging at ultrahigh fields, e.g., 7 T. In this study, we aim to numerically analyze the performance of an eight-channel ICE-decoupled loop array at 7 T. Three dimensional (3-D) electromagnetic (EM) and radiofrequency (RF) circuit co-simulation approach was employed. The values of all capacitors were obtained by optimizing the S-parameters of all coil elements. The EM simulation accurately modeled the coil structure, the phantom and the excitation. All coil elements were well matched to 50 ohm and the isolation between any two coil elements was better -15 dB. The simulated S parameters were exactly similar with the experimental results, indicating the simulation results were reliable. Compared with the conventional capacitively decoupled array, the ICE-decoupled array had higher sensitivity at the peripheral areas of the image subjects due to the shielding effect of the decoupling loops. The increased receive sensitivity resulted in an improvement of signal intensity and SNR for the ICE-decoupled array.

Characteristics of Brains in Autism Spectrum Disorder: Structure, Function and Connectivity across the Lifespan

Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder characterized by impaired social communication and restricted and repetitive behaviors (RRBs). Over the past decade, neuroimaging studies have provided considerable insights underlying neurobiological mechanisms of ASD. In this review, we introduce recent findings from brain imaging studies to characterize the brains of ASD across the human lifespan. Results of structural Magnetic Resonance Imaging (MRI) studies dealing with total brain volume, regional brain structure and cortical area are summarized. Using task-based functional MRI (fMRI), many studies have shown dysfunctional activation in critical areas of social communication and RRBs. We also describe several data to show abnormal connectivity in the ASD brains. Finally, we suggest the possible strategies to study ASD brains in the future.

Loading-induced changes on topographical distributions of the zonal properties of osteoarthritic tibial cartilage--A study by magnetic resonance imaging at microscopic resolution

The topographical distributions of the zonal properties of articular cartilage over the medial tibia from an experimental osteoarthritis (OA) model were evaluated as a function of external loading by microscopic Magnetic Resonance Imaging (µMRI). T2 relaxation times and cartilage thicknesses were measured at 17.6 µm resolution from 118 specimens, which came from thirteen dogs (six 8-week and seven 12-week after surgery), with and without mechanical loading. In addition, bulk mechanical modulus was measured topographically from each tibia surface. The total thickness decreased significantly under the external loading, in which the relative thickness of the superficial zone (SZ) and the transitional zone (TZ) increased whereas the radial zones (RZs) decreased. In the bulk data, T2(55°) decreased significantly (p<0.001) at all OA-time-points, but T2(0°) decreased without significance (p>0.05) at 8-week. Complex relationships were found in the zonal tissue properties as a function of external loading with the progress of OA. T2 in the superficial zone changed more profoundly than the same properties in the radial zone as a function of external loading at all OA time-points. This study confirms that OA affects the load-induced changes in the molecular distribution and structure of cartilage, which are both depth-dependent and topographically distributed. Such detailed knowledge of mechanobiological changes in specific tibial cartilage zones and locations with OA progress could improve the early detection of the subtle softening of cartilage that accompanies pre-clinical stages of OA.

A monopole/loop dual-tuned RF coil for ultrahigh field MRI

Proton and heteronuclear MRI/MRS using dual-tuned (DT) coils could provide both anatomical and metabolic images without repositioning the subject. However, it is technologically challenging to attain sufficiently electromagnetic (EM) decoupling between the heteronuclear channel and proton channel, and keep the imaging areas and profiles of two nuclear channels highly matched. In this study, a hybrid monopole/loop technique was proposed for DT coil design and this technique was validated by implementing and testing a DT (1)H/(23)Na coil for MR imaging at 7T. The RF fields of the monopole ((1)H channel) and regular L/C loop ((23)Na channel) were orthogonal and intrinsically EM decoupled. Bench measurement results demonstrated the isolation between the two nuclear channels was better than -28 dB at both nuclear frequencies. Compared with the conventional DT coil using trap circuits, the monopole/loop DT coil had higher MR sensitivity for sodium imaging. The experimental results indicated that the monopole/loop technique might be a simple and efficient design for multinuclear imaging at ultrahigh fields. Additionally, the proposed DT coils based on the monopole/loop technique can be used as building blocks in designing multichannel DT coil arrays.

Parallel imaging performance investigation of an 8-channel common-mode differential-mode (CMDM) planar array for 7T MRI

An 8-channel planar phased array was proposed based on the common-mode differential-mode (CMDM) structure for ultrahigh field MRI. The parallel imaging performance of the 8-channel CMDM planar array was numerically investigated based on electromagnetic simulations and Cartesian sensitivity encoding (SENSE) reconstruction. The signal-to-noise ratio (SNR) of multichannel images combined using root-sum-of-squares (rSoS) and covariance weighted root-sum-of-squares (Cov-rSoS) at various reduction factors were compared between 8-channel CMDM array and 4-channel CM and DM array. The results of the study indicated the 8-channel CMDM array excelled the 4-channel CM and DM in SNR. The g-factor maps and artifact power were calculated to evaluate parallel imaging performance of the proposed 8-channel CMDM array. The artifact power of 8-channel CMDM array was reduced dramatically compared with the 4-channel CM and DM arrays demonstrating the parallel imaging feasibility of the CMDM array.