Normative values of thymus in healthy children; stiffness by shear wave elastography

Application of real-time shear wave elastography technology in healthy pediatric hip joints

BACKGROUND

Recently, pediatric hip joint diseases have received increasing attention, however, most researches focus on conventional ultrasound. The aim of our study is to explore the application of real-time shear wave elastography (SWE) technology in different tissue structures of healthy pediatric hip joints to distinguish between the normal and pathological states, and provide a normal reference range for shear wave Young's moduli for clinical practices and subsequent scientific researches.

METHODS

According to the selection criteria, 189 healthy full-term infants with 378 hip joints were enrolled, including 102 males and 87 females aged 2-90 days. They were divided into three groups based on age: 0-30 days (61 patients), 31-60 days (63 patients), and 61-90 days (65 patients). All the subjects underwent routine ultrasound examination to perform Graf typing, and then subjected to the SWE. The Young's moduli of the femoral head, acetabular lip, acetabular cartilage apex, gluteus medius, gluteus minimus, and iliacus were recorded. The differences in various parts among the three groups, between the left and right sides, and between males and females were compared. The 95% medical reference value range for each part was obtained and consistency test was conducted.

RESULTS

There was no statistically significant difference in various parts between the left and right hip joints (P > 0.05) or between males and females (P > 0.05). There were significant differences in the femoral head, acetabular lip, and acetabular cartilage apex among the three groups (P < 0.05). The Young's moduli of the femoral head, acetabular lip, and acetabular cartilage apex were positively correlated with age (r1 = 0.56, P < 0.05; r2 = 0.51, P < 0.05; r3 = 0.58, P < 0.05). The Young's moduli of the gluteus medius, gluteus minimus, and iliacus were not correlated with age (P > 0.05). The intra- and inter-observer evaluation results both had a high correlation, and the 95% Confidence Interval (95% CI) of both were relatively concentrated.

CONCLUSION

Real-time SWE technology can be used to obtain the Young's moduli of healthy pediatric hip joints and surrounding tissues, and distinguish between healthy and pathological states. This can provide a normal reference range for shear wave Young's moduli for clinical practices and subsequent scientific researches.

Enigmatic thymus: Variations in anatomical localisation of thymic tissue as an easily misdiagnosed congenital anomaly in surgical practice

We point out the issue of differential diagnosis regarding the finding of ectopically localised thymic tissue (a thymic cyst) in the neck. Thymic tissue can be found anywhere along its developmental tract of descent, from the angle of the mandible to the upper mediastinum. Disruption of the thymic descent can result in ectopically/abnormally localised islets of accessory thymic tissue, which may undergo cystic changes, as described in a case report by Sun et al. This anatomical variation of the thymus may be clinically misinterpreted as a neoplasm or other congenital anomalies as a branchial cyst, lymphatic malformation or cystic hygroma. The present editorial focuses on the challenge of establishing a diagnosis of ectopically localised tissue of thymus often presented as a lateral cervical mass, especially in the case of cystic variation/degeneration of this thymic tissue. We summarise hypotheses on the origin of such congenital cervical thymic cysts from the point of view of evolutionary history and embryology. We also discuss lesser-known facts about the anatomy, histopathology and developmental biology of the thymus as one of the most enigmatic organs in the human body.

Imaging of thymic epithelial tumors-a clinical practice review

This review article comprehensively examines the diagnostic approach to thymic epithelial tumors (TETs) and other mediastinal masses, focusing on imaging modalities and differential diagnosis. Beginning with a discussion on traditional and contemporary classification systems for mediastinal tumors, including the Japanese Association for Research on the Thymus (JART) and International Thymic Interest Group (ITMIG) classifications, it highlights the shift towards computed tomography (CT)-based categorizations. Emphasis is placed on the importance of distinguishing between solid and cystic lesions in the anterior mediastinum, with detailed insights into imaging characteristics and histological features of various TET subtypes such as thymomas, thymic carcinomas, and thymic neuroendocrine tumors (NETs). The review also elucidates common differential diagnoses, including lymphomas and germ cell tumors, providing guidance on key imaging findings and considerations for accurate diagnosis. Furthermore, it underscores the significance of patient background and blood tests in differential diagnosis, discussing age-related prevalence patterns and tumor marker assessment. After addressing the diagnostic challenges posed by thymic cysts offering insights into their radiological features, management considerations, and potential complications, this review extends to other rare mediastinal lesions highlighting the need for a comprehensive evaluation for accurate identification and management of these tumors. Finally, as illustrative examples, we present six cases highlighting various aspects of anterior mediastinal tumors, including TET. These cases provide valuable insights into the diagnostic challenges, imaging characteristics, and management considerations encountered in clinical practice. The cases presented herein do not all illustrate typical images, courses, and diagnoses. However, they each contain significant implications. Thus, we present them with the belief that they will aid in understanding the intricate nuances of image diagnosis in actual clinical practice.

A Case for Material Stiffness as a Design Parameter in Encapsulated Islet Transplantation

Diabetes is a disease that plagues over 463 million people globally. Approximately 40 million of these patients have type 1 diabetes mellitus (T1DM), and the global incidence is increasing by up to 5% per year. T1DM is where the body's immune system attacks the pancreas, specifically the pancreatic beta cells, with antibodies to prevent insulin production. Although current treatments such as exogenous insulin injections have been successful, exorbitant insulin costs and meticulous administration present the need for alternative long-term solutions to glucose dysregulation caused by diabetes. Encapsulated islet transplantation (EIT) is a tissue-engineered solution to diabetes. Donor islets are encapsulated in a semipermeable hydrogel, allowing the diffusion of oxygen, glucose, and insulin but preventing leukocyte infiltration and antibody access to the transplanted cells. Although successful in small animal models, EIT is still far from commercial use owing to necessary long-term systemic immunosuppressants and consistent immune rejection. Most published research has focused on tailoring the characteristics of the capsule material to promote clinical viability. However, most studies have been limited in scope to biochemical changes. Current mechanobiology studies on the effect of substrate stiffness on the function of leukocytes, especially macrophages-primary foreign body response (FBR) orchestrators, show promise in tailoring a favorable response to tissue-engineered therapies such as EIT. In this review, we explore strategies to improve the clinical viability of EIT. A brief overview of the immune system, the FBR, and current biochemical approaches will be elucidated throughout this exploration. Furthermore, an argument for using substrate stiffness as a capsule design parameter to increase EIT efficacy and clinical viability will be posed.

Cine MR feature tracking analysis for diagnosing thymic epithelial tumors: a feasibility study

BACKGROUND

To assess the feasibility of the cine MR feature tracking technique for the evaluation of cardiovascular-induced morphological deformation in the diagnosis of thymic epithelial tumors (TETs).

METHODS

Our study population consisted of 43 patients with pathologically proven TETs including 10 low-grade thymomas, 23 high-grade thymomas, and 10 thymic carcinomas. Cine MR images were acquired using a balanced steady-state free precession sequence with short periods of breath-hold in the axial and oblique planes in the slice with the largest lesion cross-sectional area. The tumor margin was manually delineated in the diastolic phase and was automatically tracked for all other cardiac phases. The change rates of the long-to-short diameter ratio (∆LSR) and tumor area (∆area) associated with pulsation were compared between the three pathological groups using the Kruskal-Wallis H test and the Mann-Whitney U test. A receiver-operating characteristic (ROC) curve analysis was performed to assess the ability of each parameter to differentiate thymic carcinomas from thymomas.

RESULTS

∆LSR and ∆area were significantly different among the three groups in the axial plane (p = 0.028 and 0.006, respectively) and in the oblique plane (p = 0.034 and 0.043, respectively). ∆LSR and ∆area values were significantly lower in thymic carcinomas than in thymomas in the axial plane (for both, p = 0.012) and in the oblique plane (p = 0.015 and 0.011, respectively). The area under the ROC curves for ∆LSR and ∆area for the diagnosis of thymic carcinoma ranged from 0.755 to 0.764.

CONCLUSIONS

Evaluation of morphological deformation using cine-MR feature tracking analysis can help diagnose histopathological subtypes of TETs and identify thymic carcinomas preoperatively.

Can Shear Wave Elastography Help Differentiate Acute Tonsillitis from Normal Tonsils in Pediatric Patients: A Prospective Preliminary Study

Shear wave elastography (SWE) is a non-invasive imaging technique used to quantify the elasticity/stiffness of any tissue. There are normative SWE studies on tonsils in healthy children in the literature. The purpose of this study is to analyze the palatine tonsils in children with acute tonsillitis using ultrasound and SWE. In this prospective study, pediatric patients aged 4-18 years diagnosed with acute tonsillitis and healthy children were included. Those with antibiotic use, chronic tonsillitis, adenoid hypertrophy, and having chronic disease, immunodeficiency, and autoimmune disease, or any rheumatological disease were excluded. The volume and elasticity of palatine tonsil were measured via ultrasound and SWE. The study included 81 (46 female, 35 male) acute tonsillitis patients, and 63 (38 female, 25 male) healthy children between the ages of 4 and 18. Elasticity (kPa) values of tonsils were found significantly higher in the tonsillitis group (SWE-R: 25.39 ± 4.64, SWE-L: 25.01 ± 4.17) compared to the normal group (SWE-R: 9.71 ± 2.37, SWE-L: 9.39 ± 2.19) (p < 0.001). In the tonsillitis group, a significant positive correlation was found between tonsil volume and elasticity (r: 0.774, p: 0.002). In conclusion, in pediatric patients with acute tonsillitis, higher kPa values were obtained with SWE in the palatine tonsils.

Development of bilayered porous silk scaffolds for thymus bioengineering

The thymus coordinates the development and selection of T cells. It is structured into two main compartments: the cortex and the medulla. The replication of such complex 3D environment has been challenged by bioengineering approaches. Nevertheless, the effect of the scaffold microstructure on thymic epithelial cell (TEC) cultures has not been deeply investigated. Here, we developed bilayered porous silk fibroin scaffolds and tested their effect on TEC co-cultures. The small and large pore scaffolds presented a mean pore size of 84.33 ± 21.51 μm and 194.90 ± 61.38 μm, respectively. The highly porous bilayered scaffolds presented a high water absorption and water content (> 94 %), together with mechanical properties in the range of the native tissue. TEC (i.e., medullary (mTEC) and cortical (cTEC) cell lines) proliferation is increased in scaffolds with larger pores. The co-culture of both TEC lines in the bilayered porous silk scaffolds presents enhanced cell proliferation and metabolic activity when compared with mTEC in single culture. Also, when the co-culture occurred with cTEC in the small pores layer and mTEC in the large pores layer, a 9.2- and 18.9-fold increase in Foxn1 and Icam1 gene expression in cTEC is evident. These results suggest that scaffold microstructure and the co-culture influence TEC's behaviour. Bilayered silk scaffolds with adjusted microstructure are a valid alternative for TEC culture, having possible applications in advanced thymus bioengineering strategies.

Recapitulation of Thymic Function by Tissue Engineering Strategies

The thymus is responsible for the development and selection of T lymphocytes, which in turn also participate in the maturation of thymic epithelial cells. These events occur through the close interactions between hematopoietic stem cells and developing thymocytes with the thymic stromal cells within an intricate 3D network. The complex thymic microenvironment and function, and the current therapies to induce thymic regeneration or to overcome the lack of a functional thymus are herein reviewed. The recapitulation of the thymic function using tissue engineering strategies has been explored as a way to control the body's tolerance to external grafts and to generate ex vivo T cells for transplantation. In this review, the main advances in the thymus tissue engineering field are disclosed, including both scaffold- and cell-based strategies. In light of the current gaps and limitations of the developed systems, the design of novel biomaterials for this purpose with unique features is also discussed.

The Role of Superb Microvascular Imaging and Shear Wave Elastography in Differentiation of Thyroid Nodules from Intrathyroidal Ectopic Thymus in Children

BACKGROUND

Ectopic thymus could be located intrathyroidal, therefore fine ultrasound details are useful for this differentiation.

AIM

To investigate differences in stiffness and vascularity properties among thyroid nodules and intrathyroidal ectopic thymus (IET) by obtaining quantitative data in children.

PATIENTS AND METHODS

Twenty-seven thyroid nodules and 20 IET in children were evaluated in terms of vascularity index (VI) via superb microvascular imaging (SMI) and stiffness by shear wave elastography (SWE). Differences in the volume, VI, and SWE parameters of the lesions were assessed by using the Mann-Whitney U test. Association of the age, lesion volume, SWE, and VI parameters was investigated by using Spearman's correlation analysis. The optimal cut-off values for stiffness and vascularity in the differentiation of nodules from IET were calculated with ROC analysis.

RESULTS

The median (range) age of the participants with thyroid nodules and IET were 15.6 (10-18) years and 8.8 (3-14) years, respectively. The medians (range) VI of the IET and thyroid nodules were 4.7 (0.2-16) % and 23.8 (7.5-40)%, respectively. The median SWE values were 7.6 (4.4-9.5) kPa and 15.58 (8.5-23.4) kPa for IET and nodules, respectively. There have been highly significant differences among medians of volume, SWE, and VI values of the lesions. Significant positive correlations were found between VI and SWE parameters (p=0.001, r=0.64), and volume with VI (p=0.018, r=0.34) and SWE (p:0.001, r= 0.5). The diagnostic accuracies were 93%, 91% with the cut-off values as 9.2 kPa, 13% for the SWE and SMI, respectively. IETs were found to be less vascular and less stiff than thyroid nodules.

CONCLUSIONS

IETs could be easily and confidently differentiated from nodules using SWE and SMI quantifications. This discrimination prompts the reduction of unnecessary interventional procedures.

Application of Shear Wave Sonoelastography in the Differential Diagnosis of Extra- and Intra-Thyroidal Ectopic Thymic Tissue

The ultrasound (US) pattern of intrathyroidal ectopic thymus (IET) can resemble papillary thyroid carcinoma (PTC) while the extrathyroidal ectopic thymus (EET) can mimic pathological lymph nodes. Recently, the usefulness of strain elastography (SE) was demonstrated in the differential diagnosis, however this method has several limitations. The aim of the current study was to assess the usefulness of shear wave elastography (SWE) in this field. The US, SE, and SWE were performed in 31 children with 53 ectopic thymuses (ETs) and quantitative values of SWE parameters were calculated, so as to generate potential normative values of ET elasticity and of the shear wave ratio (SWR). The mean SWR_IET was 0.89 ± 0.21 and the mean shear wave stiffness (SWS) was 7.47 ± 1.93 kPa. The mean SWR_EET was 0.84 ± 0.15 and the mean SWS_EET was 11.28 ± 2.58 kPa. The results have proven that the stiffness of ETs is lower or equal to the thyroid’s. SWE was demonstrated to be a useful diagnostic method for ET evaluation. Therefore, the application of SWE in ET diagnosis allows more accurate evaluation of ET-like lesions and, in many cases, allows one to avoid invasive procedures, simultaneously providing a precise monitoring method based on combined US and SWE evaluation.

Normative values of pancreas stiffness by shear wave elastography in healthy children and adolescents

PURPOSE

To define normal pancreas elasticity and velocity values with shear wave elastography (SWE) in healthy children and assess associations with gender, age, and body mass index (BMI).

METHODS

This prospective study included a total of 100 cases (male: 50; female: 50), aged 3-17 years. Preschool, school, and adolescent periods of 3-6 years (n = 27), 7-12 years (n = 30), and 13-17 years (n = 43), respectively, were created in addition to two groups representing prepubertal and postpubertal periods of 3-10 years (n = 50) and 11-18 years (n = 50), respectively. Demographic data regarding the gender, age, height, body weight, and BMI were recorded. Pancreatic head, corpus, and tail SWE measurements were performed with a convex transducer (3.5-5 MHz). Correlations and comparisons were made for stiffness values between groups. Statistical analyses used Mann-Whitney U, Kruskal-Wallis, and Spearman's correlation tests.

RESULTS

Medians (25-75th percentage) of age and BMI were 7 (4.25-10) years and 15 (13-17) years and 17.47 (14.94-19.23) kg/m² and 21.22 (17.41-24) kg/m² in the two age groups, respectively. The median (interquartile range) elasticity and velocity values for the head, corpus, and tail sections of the pancreas were measured as 9.35 (2.9) kPa and 1.76 (0.26) m/s; 9.3 (2.5) kPa and 1.74 (0.21) m/s; and 8.75 (2) kPa and 1.69 (0.15) m/s, respectively. No significant differences were identified for stiffness values between gender and pancreatic section. Pancreatic stiffness values were significantly different among two (p = 0.001) and three (p = 0.028) age groups, and presented mild positive correlations with age (r: 0.23, p: 0.002), height (r: 0.18, p: 0.01), body weight (r: 0.38, p: 0.003), and BMI (r: 0.37, p: 0.045).

CONCLUSION

Normal elasticity and velocity values were defined for the pancreas with SWE in children. Pancreatic stiffness does not significantly change among pancreas parts, but it increases with the transition from childhood to adolescence.