Muscles of mastication model-based MR image segmentation

The study aimed to determine the muscle pattern of medial pterygoid, lateral pterygoid, and masseter (length, cross-section, and angulation) in adult non-orthodontic patients and its effect on craniofacial structures. The study was conducted from January 14, 2019 to January 14, 2020. Ethical clearance of this study was obtained from the ethical committee Ethical Clearance was obtained from Faculty of Dental Sciences, IMS, BHU, Institutional Ethical Committee with Ref no. Dean/2019/EC/1824 dated 23.04.2019 of the university. The sample size was estimated using the G-power statistical program. Power analysis indicated a minimum sample size of 27. Inclusion and exclusion criteria were set. Consent was taken from participants. Seventy-seven subjects who were willing to participate and have given written consent were enrolled for the study. Participants were sent for lateral cephalometry (Dolphin Cephalometric software) Dolphin Imaging and management solution, for 6 angular and 11 linear measurements. Nineteen subjects did not turn up for the scan. Twenty-eight participants underwent MRI (magnetic resonance imaging) to evaluate muscle patterns (masseter, medial, and lateral pterygoid). The intra-class correlation coefficient (ICC), Kolmogorov-Smirnov (KS) test, descriptive statistics, and multiple regression analysis were computed. The P value was set as ≤0.001(highly statistically significant) and ≤0.05 (significant relation). There was a highly statistically significant (p ≤ 0.001) association between masseter length to upper facial height (N-Ans) and ramal length (Cd-Go). Length of medial pterygoid was significantly related (p ≤ 0.05) with SNB and length of body of mandible (Pog-Go). The cross-section of this muscle showed significant relation with upper facial height (N-Ans) and ramal length (Cd-Go). The correlation of the length of lateral pterygoid with upper facial height (N-Ans) and maxillary length (A-Ptm) was highly significant. The muscle pattern has a significant correlation with maxillofacial morphology. The masseter muscle is the longest and thickest (cross-section) and is angulated vertically than the other two muscles (medial pterygoid and lateral pterygoid). Of the three muscles, the medial pterygoid influences more common craniofacial parameters suggestive of its symbiotic activity. Lateral pterygoid affects the maxillary length and facial height.

Objective: To assess the sequelae of unilateral chewing on muscles of mastication via comparing the approximatemuscular volume (AMV) of the masseter (MM), medial pterygoid (MPM), temporalis (TM), superior and inferior lateral pterygoid muscles (SLPM/ILPM) bilaterally using MRI. Materials and methods: Twenty patients (16 females and 4 males) were selected from outpatient dental clinics of Kaser Al Aini Hospitals, Cairo University, complaining from being unilaterally edentulous for one year or more. Also six fully dentate individuals (2 males and 4 females) were selected as control group. Magnetic Resonance Imaging (MRI) of the masticatory muscles was performed followed by measuring the approximate muscle volume (AMV) for each muscle bilaterally using the planimetry method. Results: Showed increase in the approximate muscular volume (AMV) of the dentate side in both right side and left side edentulous patients. Conclusion: Our study shows the effect of long term unilateral chewing on decreasing the AMV in the nonfunctioning side, suggesting that measuring the approximate masticatory muscle volume using MRI could be helpful in detection of long-term functional disability of each muscle in comparison to adjacent muscles.

A 56-year-old woman presented with a 1-year history of unexplained left facial swelling and pain associated with a self-palpated, firm, and fixed mass. Noncontrast and contrast-enhanced computed tomography (CT) of the mastoid revealed a slightly hyperdense mass measuring approximately 3.7 cm × 6.4 cm × 3.4 cm in the left cranial base–infratemporal fossa, with heterogeneous internal density and irregular, lobulated morphology. The mass encircled the left temporomandibular joint during growth and showed indistinct borders with the masseter, medial pterygoid, and lateral pterygoid muscles. Expansile bone destruction involved the left mandible, condyle, zygomatic arch, sphenoid bone, temporal bone, and medial and lateral pterygoid plates, suggesting invasiveness; delayed heterogeneous enhancement was seen postcontrast. Noncontrast and contrast-enhanced magnetic resonance imaging (MRI) demonstrated a patchy low-signal intensity lesion in the left cranial base–temporal fossa. Low signal intensity was observed on T1-weighted imaging, T2-weighted imaging, T2-fluid-attenuated inversion recovery, and diffusion-weighted imaging sequences, with no postcontrast enhancement. The patient underwent left cranial base–maxillofacial mass resection under general anesthesia. Postoperative pathology confirmed giant cell reparative granuloma. Giant cell reparative granuloma is a rare benign bone lesion with local invasiveness, most commonly affecting the jawbones. In this case, CT showed soft tissue mass formation with expansile bone destruction, whereas MRI demonstrated uniformly low signal intensity across all sequences. These findings reflect the fibrous matrix and hemosiderin deposition characteristic of the lesion and provide important radiological clues. Recognition of these imaging features aids differentiation from malignant lesions; however, definitive diagnosis requires histopathological examination (Figure 1). Imaging findings of the patient. (a) Noncontrast CT reveals a slightly hyperdense mass in the left skull base–infratemporal fossa with indistinct margins from adjacent muscles (arrow). (b, c) Contrast-enhanced CT demonstrates delayed and heterogeneous enhancement of the lesion, with dual-phase CT values of approximately 99 HU and 123 HU, respectively (arrow). (d) Coronal images demonstrate the main lesion encircling the left temporomandibular joint (arrow). (e) Bone window images reveal multiple areas of expansile bone destruction (arrow). (f–i) Noncontrast MRI sequences show low signal intensity on T1-weighted imaging, T2-weighted imaging, T2-fluid-attenuated inversion recovery, and diffusion-weighted imaging (arrow). (j) Contrast-enhanced MRI shows no enhancement of the lesion (arrow). (k, l) Pathological findings (hematoxylin–eosin staining, × 100) confirm giant cell reparative granuloma. CT, computed tomography; MRI, magnetic resonance imaging. Pinshan Zhang: conceptualization, writing – original draft, writing – review and editing. The author has nothing to report. The author has nothing to report. The author has nothing to report. The patient provided written informed consent at the time of entering this study. The author declares no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.

ObjectivesThe aim of this study was to evaluate the relationship between masticatory muscle thickness and mandibular morphology in young Korean adults with normal occlusion and mandibular prognathism.Patients and MethodsMultidetector computed tomography (MDCT) was used to measure the masticatory muscle thickness on the right side in 100 Korean young adults (50 normal occlusion group, 50 mandibular prognathism group). Cephalometric analysis was done to measure mandibular morphology. Pearson correlation analysis was done to investigate the relationship between the masticatory muscle thickness and mandibular morphometry.ResultsThe four masticatory muscles showed positive correlation with intergonial width in all subjects. All muscles, except temporalis, positively correlated with height of the ramus and mandibular length. Positive correlation was also observed in all muscles, except medial pterygoid, with thickness of the ramus. In the normal occlusion group, all four masticatory muscles showed positive correlation with intergonial width and ramus thickness. Positive correlation was also observed in all muscles (except lateral pterygoid) with mandibular length. Masseter and lateral pterygoid positively correlated with height of the ramus. In the mandibular prognathism group, all masticatory muscles, except lateral pterygoid, showed positive correlation with intergonial width. The masseter muscle showed negative correlation with ANB.ConclusionThe results suggest a positive correlation of the thickness of masticatory muscles with both horizontal and vertical dimensions of the mandible. However, thickness of the masseter was found to decrease in patients with increasing severity of mandibular prognathism.

Cardiac Magnetic Resonance (CMR) imaging is widely used in the clinic to assess the patient-specific cardiac structure and function. However, the manual analysis of the CMR data is tedious and subjective. In this work, we developed a fully automatic segmentation system for the left ventricle (LV) myocardium from MR cine images. The system consists of three major components. Firstly, a conventional convolutional neural network (CNN) was trained to detect the global region of interest (ROI) of LV. Secondly, a novel multi-scope CNN was proposed to segment the LV myocardium from the reduced ROI, taking advantage of the image context in different scopes, such that both the local accuracy and global consistency can be implicitly learned by the CNN. Finally the results were pruned with simple morphological filtering preserving the largest component. With a relatively small training set of 200 MR cine images, the method achieved an average segmentation accuracy of 0.71 as expressed by the Dice overlap index. The proposed method can be applied to automatically segment the LV from MR images with the reasonable accuracy, or as a proper initialization for local shape methods to achieve further refined results.

The aim of this study was to verify if patients with arthrogenous temporomandibular disorders (TMD) with different Magnetic Resonance Imaging (MRI) diagnoses had some objective differences in the surface electromyography (sEMG) characteristics of their masticatory muscles. Twenty-four TMD patients were categorized according to the RDC/TMD [1]; MRI classified patients with disk displacement (DD, mean age 22 years, SD 5; M/F: 3/6), and osteoarthrosis and/or disk displacement (OA, mean age 37 years, SD 10; M/F: 4/11). sEMG of the right and left masseter and anterior temporalis muscles was performed according to a standardized protocol, recording teeth clenching on either cotton rolls or occlusal surfaces [2]. EMG data were compared to those collected in control subjects of similar age and sex, and EMG z-scores were computed. The comparison of EMG z-scores and MRI scores between the 2 patient groups using the Mann-Whitney test was statistically significant (P < 0.05): the patients with OA had larger scores than the patients with only DD. The linear correlation analysis run between the EMG and the MRI scores found significant correlations in both patient groups. The EMG characteristics allowed to well differentiate patients with MRI diagnosis of DD or OA. The objective recording of the masticatory muscle function and dysfunction through sEMG can be a first simple and low cost diagnostic approach to TMD patients.

Purpose:The aim of this study was to explore the use of Magnetic Resonance Imaging (MRI)‐derived features as indicators of Radiotherapy (RT)‐induced normal tissue morbidity. We also investigate the relationship between these features and RT dose in four critical structures.Methods:We demonstrate our approach for four patients treated with RT for base of tongue cancer in 2005–2007. For each patient, two MRI scans (T1‐weighted pre (T1pre) and post (T1post) gadolinium contrast‐enhancement) were acquired within the first six months after RT. The assessed morbidity endpoint observed in 2/4 patients was Grade 2+ CTCAEv.3 trismus. Four ipsilateral masticatory‐related structures (masseter, lateral and medial pterygoid, and the temporal muscles) were delineated on both T1pre and T1post and these scans were co‐registered to the treatment planning CT using a deformable demons algorithm. For each structure, the maximum and mean RT dose, and six MRI‐derived features (the second order texture features entropy and homogeneity, and the first order mean, median, kurtosis, and skewness) were extracted and compared structure‐wise between patients with and without trismus. All MRI‐derived features were calculated as the difference between T1pre and T1post, ΔS.Results:For 5/6 features and all structures, ΔS diverged between trismus and non‐trismus patients particularly for the masseter, lateral pterygoid, and temporal muscles using the kurtosis feature (−0.2 vs. 6.4 for lateral pterygoid). Both the maximum and mean RT dose in all four muscles were higher amongst the trismus patients (with the maximum dose being up to 25 Gy higher).Conclusion:Using MRI‐derived features to quantify RT‐induced normal tissue complications is feasible. We showed that several features are different between patients with and without morbidity and that the RT dose in all investigated structures are higher amongst patients with morbidity. MRI‐derived features, therefore, has the potential to improve predictions of normal tissue morbidity.

To prospectively determine clinical value of dynamic contrast material-enhanced magnetic resonance (MR) imaging in the evaluation of disease activity in perianal Crohn disease (CD). Patients provided written informed consent. Study approval was waived by an institutional review board. Thirty-three patients with perianal CD underwent pelvic MR imaging; 17 were male (mean age, 37.4 years +/- 10.8 [standard deviation]; age range, 18-54 years) and 16 were female (mean age, 32.0 years +/- 8.3; age range, 16-43 years). Dynamic contrast-enhanced MR imaging was performed; time-intensity curves (TICs) were obtained. Each pixel was classified as one of six predefined TIC shape types. For each MR imaging examination, a region of interest (ROI) was drawn around the fistula on the single section corresponding to the most extensive and most hyperintense lesion; maximum enhancement (ME), slope of enhancement, and TIC shapes were calculated. Absolute and relative numbers of pixels for each curve type were calculated in a two-dimensional ROI. These results were compared with Perianal Disease Activity Index (PDAI), C-reactive protein (CRP) level, an MR imaging-based severity score, and clinical outcome. A Spearman rank correlation test was used to calculate correlation coefficients between dynamic contrast-enhanced MR imaging parameters and reference parameters. A Mann-Whitney U test was used to calculate differences in dynamic contrast-enhanced MR imaging parameters between predefined groups of patients. Significant correlations were found between the absolute amounts of the TIC shape types and PDAI and between ROI volume and PDAI. The ratio of quickly enhancing versus slowly enhancing pixels correlated with higher MR imaging scores as did the ROI volume. The absolute amounts of pixels displaying TIC types 2, 3, 4, and 5 correlated significantly with MR imaging score. CRP level showed a significant correlation with mean ME. Larger numbers of quickly enhancing pixels were observed in patients who needed medication changes or developed new abscesses during follow-up. Dynamic contrast-enhanced MR imaging can help determine disease activity in perianal CD and might be helpful in selecting a subpopulation of patients who should be monitored more closely for development of more extensive disease.

To compare quantitative values of cerebral blood flow (CBF) derived from dynamic susceptibility contrast (DSC) magnetic resonance (MR) imaging with reference standard positron emission tomography (PET) in patients with confirmed cerebrovascular occlusive disease. Local institutional review board approval and informed consent were obtained for a prospective study of 18 patients (six men, 12 women; age range, 28-71 years; mean age, 45 years ± 10.4 [standard deviation]) with angiographically confirmed Moyamoya (n = 8) or internal carotid artery occlusions (n = 10). DSC MR images and oxygen 15-labeled water (H(2)[(15)O]) PET images were acquired on the same day. DSC images were postprocessed to yield parametric images of CBF (in mL/100 g/min), coregistered, and analyzed using grid-based regions of interest. Mean values of CBF in each region of interest from MR imaging and PET data sets were compared. Correlations for each patient were determined and overall agreement between pooled MR imaging and PET CBF was reported using linear regression analysis and Bland-Altman plots. Strong correlations (r(2) ≥ 0.55) were found between MR imaging and PET CBF values in all patients. Use of the bookend approach was found to underestimate CBF predictably across the patient cohort (mean slope, 0.82; standard deviation, 0.18; slope of aggregated data, 0.75). This allowed for a simple rescaling of MR imaging values producing strong agreement with PET values in the aggregated data (r(2) = 0.66; slope = 1.00; intercept = 0.00). The data show that the bookend MR imaging technique produces similar results for quantitative CBF between DSC MR imaging and H(2)[(15)O] PET. Although MR-derived CBF underestimated PET-derived CBF, the patient-to-patient variability in the slopes of the linear MR and PET relationships was significantly smaller than a competing quantitation technique. As a result, the bookend technique appears to more predictably measure quantitative CBF in a clinical setting.

ObjectiveThis study aimed to investigate the imaging characteristics of temporomandibular joint disorder (TMD) using cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI), and to compare their diagnostic performance.MethodsClinical data from 53 TMD patients and 53 healthy controls were retrospectively reviewed. All participants underwent both CBCT and MRI within a two-week interval. Key measurements included condylar dimensions and joint space assessments. The study evaluated each modality’s ability to detect TMD-related abnormalities in the temporomandibular joint (TMJ) and masticatory muscles, such as joint space narrowing, bone changes, disc displacement, and muscle pathology. Statistical analysis compared diagnostic findings between the imaging techniques.ResultsImage quality was comparable between CBCT and MRI (P > 0.05). Both modalities showed no significant differences in superior and anterior joint spaces between TMD and control groups, but the posterior joint space, condylar width, and anteroposterior diameter were significantly different (P < 0.05). Across all participants, significant differences were observed between CBCT and MRI measurements for superior and anterior joint spaces (P < 0.05). Among TMD patients, 69.81% had pain disorders and 30.19% had joint disorders. Both modalities demonstrated high inter- and intra-observer consistency (P < 0.05). CBCT showed high agreement for most bony abnormalities but only moderate for disc and muscle pathology. MRI had high agreement for most findings but was moderate in detecting bone hyperplasia and sclerosis. MRI detected significantly more soft tissue abnormalities, including disc displacement and joint effusion (P < 0.05), while CBCT was more effective in identifying bone hyperplasia, sclerosis, and condylar deformation (P < 0.05).ConclusionBoth CBCT and MRI are highly valuable tools for differentiating and assessing TMD. CBCT excels in evaluating bone-related changes, whereas MRI is superior for assessing the articular disc and soft tissue abnormalities.

Aims Following stereotactic radiosurgery (SRS), brain metastases can increase in size in up to a third of cases. Conventional magnetic resonance imaging (MRI) has a limited role to distinguish between tumour recurrence and SRS-induced changes, which can impact patient management. Delayed contrast MRI treatment response assessment maps (TRAM) use the principle of contrast clearance seen in other tumours, where high vascularity shows a rapid rise in contrast as well as rapid clearance, whereas areas of damaged or low vascularity show accumulation of contrast. We aimed to assess the ability of delayed contrast MRI and multiparametric MRI techniques of diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI) and MR spectroscopy (MRS) to distinguish between radiation-related effects and tumour tissue, as these techniques assess tissue physiological and metabolic information. Method A retrospective review was performed on 23 patients who had delayed contrast and multiparametric MRI between October 2018 to April 2020. Studies were restricted to cases with brain metastases enlarging post-SRS with uncertainty at the MDT meeting regarding progression or treatment-related change, impacting the patient’s management. MRI was performed at 3T including DWI, PWI, MRS with short and intermediate echo times, and 3D T1 MPRAGE at 3-5, 20-30 and 70-90 minutes after administration of intravenous contrast. Contrast clearance analysis was performed by selecting an enhancing region of interest (ROI), measuring signal intensities at the three different timepoints and taking apparent diffusion coefficient (ADC) and relative cerebral blood volume (rCBV) values from the ROI. Choline/Creatine values were calculated from a single-voxel (10 mm isotropic) encompassing the entire contrast-enhancing lesion. Outcome was established from MRI follow-up at 6 months, with a stable or responding lesion considered treatment-related changes and increase considered progression. Results Across 23 patients, 24 metastases were assessed. Two patients were excluded as appropriate follow-up was not available. Sites of primary tumours included breast (n=8), lung (n=6), melanoma (n=4), neuroendocrine tumour from the lung (n=2) and renal cell carcinoma (n=2). Mean age was 56 years and 50% were female. In this cohort, 59% (n=13) were classified as having radiation-related changes on follow-up. Delayed MRI contrast clearance between the 3-5 and 70-90 minute imaging was significantly higher in cases of progression (23.6% vs. 2.5% decrease, p&amp;lt;0.05), as were the rCBV and Cho/Cr ratio (rCBV 3.1 vs. 1.5 and Cho/Cr ratio 2.3 vs. 1.4, p&amp;lt;0.05). Accuracy, sensitivity and specificity of using TRAM alone (contrast clearance decrease of &amp;gt;0%) for progression was 63%/100%/38%, PWI alone (rCBV cut-off 2.0) yielded results of 77%/75%/79% and for both Cho/Cr ratio alone (cut-off 1.8) and combined with TRAM, it was 90%/88%/92%. Neuroradiologist assessment of all techniques was 95%/100%/92%. Conclusion This study shows the effectiveness of delayed contrast and multiparametric MRI for treatment response assessment in patients with brain metastases treated by SRS in clinical practice. Although a delayed contrast MRI study is a very sensitive tool for detecting tumour progression, it lacks specificity. The accuracy of differentiating between tumour and treatment-related effects increases when delayed contrast MRI is used in combination with other advanced techniques such as MRS. By combining all these techniques, neuroradiologists had the highest accuracy, sensitivity and specificity for detecting progression in post-SRS brain metastases.

The sites of nerve entry and the intramuscular nerve branchings in the masseter, temporalis, medial and lateral pterygoid muscles were studied. A total of 55 muscles were taken from eight infants and only one adult subject. It was found that for each of the four muscles of mastication, the nerves entered at a nearly fixed point. The masseter and medial pterygoid have their origin, the temporalis very near to its insertion, the lateral pterygoid midway between its origin and its insertion. The intramuscular nerve branchings were investigated in the four muscles and, according to their relation to the direction of the muscle fibres, three patterns have been recognized. The results obtained were compared with those of other workers on other muscles.

To assess the accuracy of the shutter-speed approach compared with standard approach dynamic contrast material-enhanced magnetic resonance (MR) imaging pharmacokinetic analysis for breast cancer diagnosis. This study was approved by the institutional review board and was HIPAA compliant. Informed consent was obtained from 89 high-risk women (age range, 28-83 years) who had 92 suspicious lesions with negative findings at mammography (but visible at MR imaging). Each underwent a research dynamic contrast-enhanced MR imaging examination just prior to a clinical MR imaging-guided interventional procedure. Tumor region of interest (ROI) averaged and (for some) pixel-by-pixel dynamic contrast-enhanced time-course data, together with mean arterial input function, were subjected to serial standard and shutter-speed approach analyses to extract pharmacokinetic parameters, including rate constant for passive contrast reagent transfer between plasma and interstitium (K(trans)) and interstitial space volume fraction, or v(e). Pathologic findings were used as reference standards. Diagnostic accuracy was assessed with receiver operating characteristic analyses. The pathologic analyses revealed 20 malignant and 72 benign lesions. Positive predictive value of the institutional clinical breast MR imaging protocol was 22%. At 100% sensitivity, ROI-averaged shutter-speed approach K(trans) had significantly (P = .008) higher diagnostic specificity than standard approach K(trans): 86.1% versus 77.8%. The difference in the ROI-averaged K(trans) parameter value, or ΔK(trans) (≡ K(trans) [shutter-speed approach] - K(trans) [standard approach]), had even higher specificity (88.9%). Combined use of ROI analysis and pixel-by-pixel mapping of ΔK(trans) achieved 98.6% specificity at 100% sensitivity. The use of the shutter-speed dynamic contrast-enhanced MR imaging method has the potential to improve breast cancer diagnostic accuracy and reduce putatively unnecessary biopsy procedures that yield benign pathologic findings. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11102413/-/DC1.

Radiotherapy is a major treatment for head and neck cancer. Currently, computed tomography (CT) is utilized to delineate the target area and make radiotherapy plans. Compared with CT images, magnetic resonance (MR) images have excellent soft tissue contrast, which can distinguish normal surrounding tissues. It is necessary to register MR and CT images since it helps physicists to improve the accuracy of radiotherapy plans. Most of the current registrations require manual intervention to select regions of interest, which increases the workload of doctors and the time of registration to a certain extent. In this paper, an automatic registration method is proposed to delineate the regions of interest. Herein, surface meshes are extracted from the CT and MR images and utilized to perform the surface matching, then the regions of interest are extracted automatically by calculating the overlapped regions between the surface mesh of the surface-aligned MR images and CT images. Furthermore, a multi-level resolution registration mechanism is utilized to improve the registration speed. Surface matching is performed using low-resolution images to obtain transformation parameters as initial parameters for rigid registration followed by deformable registration. The experiments demonstrate that our proposed method performs better in the registration speed and accuracy over the conventional methods of delineating regions of interest manually.

Heart problems are common in newborn babies, affecting approximately 5-10 in 1000 babies. Some are more serious than others, but most babies born with heart problems do not have other health issues. Of those babies who have a serious heart problem, almost 1 in 4 will have heart surgery in their first year. In the UK, pregnant women are offered a scan at around 20weeks to try and spot any heart problems. In most cases there is not a clear reason for the problem, but sometimes other issues, such as genetic conditions, are discovered. In recent years the care given to these babies after they are born has improved their chances of surviving. However, it is recognised that babies born with heart problems have a risk of delays in their learning and development. This may be due to their medical condition, or as a result of surgery and complications after birth. In babies with heart problems, there is a need for more research on ultrasound and magnetic resonance imaging (MRI) to understand how the brain develops and why these babies are more likely to have delays in learning and development. This paper discusses the way ultrasound and MRI are used in assessing the baby's brain. Ultrasound is often used to spot any problems, looking at how the baby's brain develops in pregnancy. Advances in ultrasound technologies have made this easier. MRI is well-established and safe in pregnancy, and if problems in the brain have been seen on ultrasound, MRI may be used to look at these problems in more detail. While it is not always clear what unusual MRI findings can mean for the baby in the long term, increased understanding may mean parents can be given more information about possible outcomes for the baby and may help to improve the counselling they are offered before their baby's birth.