Quantitative analysis of the regional motion of the left hemi-diaphragm (LHD) and right hemi-diaphragm (RHD) can provide information regarding the distribution and severity of abnormalities in individual patients with conditions that affect respiration such as thoracic insufficiency syndrome (TIS). Such motion can be captured effectively from dynamic magnetic resonance imaging (dMRI) which does not involve ionizing radiation and can be obtained under free-breathing conditions. The analysis of motion can be performed on the diaphragm using 4D images constructed from dMRI, which in turn requires diaphragm segmentation in the 4D images. In this paper, we present our methodology for segmentation of the left and right diaphragms, which has been implemented in three steps: recognition of diaphragm, delineation of diaphragm, and splitting of diaphragm along the mid-sagittal plane into LHD and RHD. The challenges involved in dMRI images are low resolution, motion blur, suboptimal contrast resolution, inconsistent meaning of gray-level intensities for the same object across multiple scans, and low signal-to-noise ratio. Utilizing 200 and 100 3D images for training and testing, respectively, an average location error of one and a half voxels is achieved for the recognition step. For the delineation step, an average mean-HD of one and a half pixels is achieved. The mid-sagittal plane is identified within a quarter of a voxel. These results are promising, showing that our system can cope with the aforesaid challenges.
In pediatric patients with respiratory abnormalities, it is important to understand the alterations in regional dynamics of the lungs and other thoracoabdominal components, which in turn requires a quantitative understanding of what is considered as normal in healthy children. Currently, such a normative database of regional respiratory structure and function in healthy children does not exist. The purpose of this study is to introduce a large open-source normative database from our ongoing Virtual Growing Child (VGC) project, which includes measurements of volumes, architecture, and regional dynamics in healthy children (six to 20 years) derived via dynamic Magnetic Resonance Imaging (dMRI) images. The database provides four categories of regional respiratory measurement parameters including morphological, architectural, dynamic, and developmental. The database has 3,820 3D segmentations (around 100,000 2D slices with segmentations), which to our knowledge is the largest dMRI dataset of healthy children. The database is unique and provides dMRI images, object segmentations, and quantitative regional respiratory measurement parameters for healthy children. The database can serve as a reference standard to quantify regional respiratory abnormalities on dMRI in young patients with various respiratory conditions and facilitate treatment planning and response assessment. The database can be useful to advance future AI-based research on MRI-based object segmentation and analysis.
Thoracic Insufficiency Syndrome (TIS) is a rare condition that results in restricted lung growth and impaired respiratory function. Investigation of the impact of scoliotic spinal curve on regional respiratory function in individuals with TIS is important to elucidate the underlying mechanisms behind restricted respiratory function and to optimize effective treatment approaches. However, there are currently no suitable parameters for quantifying pulmonary respiratory function that demonstrate a strong correlation with scoliotic spinal curve. A new study of the relationship between scoliotic spinal curve and diaphragm motion is proposed in this work to uncover how spinal scoliosis impacts respiration, providing new insights into the specific mechanisms for respiratory dysfunction. The diaphragm was delineated at End Inspiration (EI) and End Expiration (EE) time points in reconstructed 4D images via dynamic MRI and was divided into left and right hemi-diaphragms. To facilitate the regional description of motion, we partitioned each hemi-diaphragm into 13 distinct regions and computed the velocity and curvature for each of these regions. An analysis was conducted on 26 cases with Main Thoracic Curves (MTC), including 15 cases with right-sided MTC (MTC-R) and 11 cases with left-sided MTC (MTC-L). T-testing comparing the MTC-R group with the MTC-L group revealed the impact of spinal curve sidedness on the motion of the left hemi-diaphragm. The velocity cloud maps exhibited a restriction of left diaphragmatic motion due to leftward spinal curve. Furthermore, correlation analysis demonstrated a significant influence of major curve angles (TCA and LCA) on hemi-diaphragm velocities in specific regions. Such findings improve our understanding of the pathophysiological mechanisms that lead to abnormal respiratory function in TIS.
Purpose: This study investigates Thoracic Insufficiency Syndrome (TIS) in pediatric patients, a condition impacting respiratory function due to spinal and thoracic deformities. The research focuses on the use of the Vertical Expandable Prosthetic Titanium Rib (VEPTR) surgery to address deformities hindering normal development and to promote lung growth. A unique non-invasive approach utilizing free-breathing dynamic magnetic resonance imaging (dMRI) is employed to analyze the 3D motion and shape of each hemi-diaphragm (HD) surface. Method: In this study of 49 TIS patients who underwent VEPTR surgery, free-breathing dMRI was used before and after surgery. After 4D image construction of diaphragm, we manually delineated the HDs on sagittal slice images at endexpiration and end-inspiration time points. We then constructed the 3D surface of the HDs, automatically selected 25 points on each HD surface, and estimated velocities and both sagittal curvature and coronal curvature at each point. Then, we identified 13 homologous regions for each HD surface and categorized subjects based on changes in Cobb angle to compare HD velocities and curvatures before and after surgery. Results: The study group consisted of 27 males and 22 females with mean age of 3.51 ± 3.49 years before surgery and 5.9 ± 3.63 years after surgery. Right HD regions exhibited statistically significantly higher velocities compared to homologous regions in the left HD, and posterior regions showed higher velocity than other regions in both HDs. The most statistically significant differences in diaphragm shape were observed in the lateral regions, with particular emphasis on the coronal curvatures. Conclusion: Through analysis of pre- and post-surgical data, we observed significant improvement in diaphragm motion following VEPTR surgery, despite minimal changes in diaphragm shape.
It is important to understand the dynamic thoracoabdominal architecture and its change after surgery since thoracic insufficiency syndrome (TIS) patients often suffer from spinal deformation, leading to alterations in regional respiratory structure and function. Free-breathing based quantitative dynamic MRI (QdMRI) provides a practical solution to evaluate the regional dynamics of the thorax quantitatively for TIS patients. Our current aim is to investigate if QdMRI can also be utilized to measure architecture for TIS patients before and after surgery. 49 paired TIS patients (before and after surgery, with 98 dynamic MRI), and another 150 healthy children comprise our study cohort. 248 dynamic MRI images were first acquired and then 248 4D images were constructed. 3D volume images at end expiration (EE) and end inspiration (EI) were used in the analysis, leading to a total of 496 3D volume images in this study. Left and right lungs, left and right hemi-diaphragms, left and right kidneys, and liver were then segmented automatically via deep learning prior to architectural analysis. Architectural parameters (3D distances and angles from the centroids of multiple objects) at EE and EI of TIS patients and healthy children were computed and compared via t-testing. The distance between the right lung and right hemi-diaphragm is found to be significantly larger at EI than that at EE for TIS patients and healthy children, and after surgery becomes closer to that of healthy children.
The lack of standardizable objective diagnostic measurement techniques is a major hurdle in the assessment and treatment of pediatric patients with thoracic insufficiency syndrome (TIS). The aim of this paper is to explore quantitative dynamic MRI (QdMRI) volumetric parameters derived from thoracic dMRI in pediatric patients with TIS and the relationships between dMRI parameters and clinical measurements. 25 TIS patients treated with vertical expandable prosthetic titanium rib (VEPTR) surgery are included in this retrospective study. Left and right lungs at endinspiration and end-expiration are segmented from constructed 4D dMRI images. Lung volumes and excursion (or tidal) volumes of the left/right chest wall and hemi-diaphragms are computed. Commonly used clinical parameters include thoracic and lumbar Cobb angles and respiratory measurements from pulmonary function testing (PFT). 200 3D lungs in total (left & right, pre-operative & post-operative, end-inspiration & end-expiration) are segmented for analysis. Our analysis indicates that change of resting breathing rate (RR) following surgery is negatively correlated with that of QdMRI parameters. Chest wall tidal volumes and hemi-diaphragm tidal volumes increase significantly following surgery. Clinical parameter RR reduced after surgical treatment with P values around 0.06 but no significant differences were found on other clinical parameters. The significant increase in post-operative tidal volumes suggests a treatment-related improvement in lung capacity. The reduction of RR following surgery shows that breathing function is improved. The QdMRI parameters may offer an objective marker set for studying TIS, which is currently lacking.
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