Carrie N. Hoff

A statistical human rib cage geometry model accounting for variations by age, sex, stature and body mass index

In this study, we developed a statistical rib cage geometry model accounting for variations by age, sex, stature and body mass index (BMI). Thorax CT scans were obtained from 89 subjects approximately evenly distributed among 8 age groups and both sexes. Threshold-based CT image segmentation was performed to extract the rib geometries, and a total of 464 landmarks on the left side of each subject׳s ribcage were collected to describe the size and shape of the rib cage as well as the cross-sectional geometry of each rib. Principal component analysis and multivariate regression analysis were conducted to predict rib cage geometry as a function of age, sex, stature, and BMI, all of which showed strong effects on rib cage geometry. Except for BMI, all parameters also showed significant effects on rib cross-sectional area using a linear mixed model. This statistical rib cage geometry model can serve as a geometric basis for developing a parametric human thorax finite element model for quantifying effects from different human attributes on thoracic injury risks.

Effects of BMI on the Risk and Frequency of AIS 3+ Injuries in Motor-Vehicle Crashes

Objective: Determine the effects of BMI on the risk of serious‐to‐fatal injury (Abbreviated Injury Scale ≥ 3 or AIS 3+) to different body regions for adults in frontal, nearside, farside, and rollover crashes.

A parametric ribcage geometry model accounting for variations among the adult population

The objective of this study is to develop a parametric ribcage model that can account for morphological variations among the adult population. Ribcage geometries, including 12 pair of ribs, sternum, and thoracic spine, were collected from CT scans of 101 adult subjects through image segmentation, landmark identification (1016 for each subject), symmetry adjustment, and template mesh mapping (26,180 elements for each subject). Generalized procrustes analysis (GPA), principal component analysis (PCA), and regression analysis were used to develop a parametric ribcage model, which can predict nodal locations of the template mesh according to age, sex, height, and body mass index (BMI). Two regression models, a quadratic model for estimating the ribcage size and a linear model for estimating the ribcage shape, were developed. The results showed that the ribcage size was dominated by the height (p=0.000) and age-sex-interaction (p=0.007) and the ribcage shape was significantly affected by the age (p=0.0005), sex (p=0.0002), height (p=0.0064) and BMI (p=0.0000). Along with proper assignment of cortical bone thickness, material properties and failure properties, this parametric ribcage model can directly serve as the mesh of finite element ribcage models for quantifying effects of human characteristics on thoracic injury risks.

A Statistical Skull Geometry Model for Children 0-3 Years Old

Head injury is the leading cause of fatality and long-term disability for children. Pediatric heads change rapidly in both size and shape during growth, especially for children under 3 years old (YO). To accurately assess the head injury risks for children, it is necessary to understand the geometry of the pediatric head and how morphologic features influence injury causation within the 0–3 YO population. In this study, head CT scans from fifty-six 0–3 YO children were used to develop a statistical model of pediatric skull geometry. Geometric features important for injury prediction, including skull size and shape, skull thickness and suture width, along with their variations among the sample population, were quantified through a series of image and statistical analyses. The size and shape of the pediatric skull change significantly with age and head circumference. The skull thickness and suture width vary with age, head circumference and location, which will have important effects on skull stiffness and injury prediction. The statistical geometry model developed in this study can provide a geometrical basis for future development of child anthropomorphic test devices and pediatric head finite element models.

Erratum: Development, validation, and application of a parametric pediatric head finite element model for impact simulations (Annals of Biomedical Engineering (2011) 39:12 (2984-2997) DOI:10.1007/s10439-011-0409-z)

In this study, a statistical model of cranium geometry for 0to 3-month-old children was developed by analyzing 11 CT scans using a combination of principal component analysis and multivariate regression analysis. Radial basis function was used to morph the geometry of a baseline child head finite element (FE) model into models with geometries representing a newborn, a 1.5-month-old, and a 3-month-old infant head. These three FE models were used in a parametric study of near-vertex impact conditions to quantify the sensitivity of different material parameters. Finally, model validation was conducted against peak head accelerations in cadaver tests under different impact conditions, and optimization techniques were used to determine the material properties. The results showed that the statistical model of cranium geometry produced realistic cranium size and shape, suture size, and skull/suture thickness, for 0to 3-month-old children. The three pediatric head models generated by morphing had mesh quality comparable to the baseline model. The elastic modulus of skull had a greater effect on most head impact response measurements than other parameters. Head geometry was a significant factor affecting the maximal principal stress of the skull (p = 0.002) and maximal principal strain of the suture (p = 0.021) after controlling for the skull material. Compared with the newborn head, the 3-month-old head model produced 6.5% higher peak head acceleration, 64.8% higher maximal principal stress, and 66.3% higher strain in the suture. However, in the skull, the 3-month-old model produced 25.7% lower maximal principal stress and 11.5% lower strain than the newborn head. Material properties of the brain had little effects on head acceleration and strain/stress within the skull and suture. Elastic moduli of the skull, suture, dura, and scalp determined using optimization techniques were within reported literature ranges and produced impact response that closely matched those measured in previous cadaver tests. The method developed in this study made it possible to investigate the age effects from geometry changes on pediatric head impact responses. The parametric study demonstrated that it is important to consider the material properties and geometric variations together when estimating pediatric head responses and predicting head injury risks. Keywords—Pediatric head injury, Parametric finite element model, Principal component analysis, Mesh morphing, Radial basis function, Parametric study, Optimization.

Pancreatic manifestations of von Hippel-Lindau disease-effect of imaging on clinical management.

Objective: To assess the impact of imaging on pancreatic lesion management in von Hippel-Lindau disease (VHL). Methods: We reviewed sequential computed tomography (CT) and magnetic resonance examinations (1997-2008) of 33 patients with VHL who had at least 1 pancreatic lesion. Results: One hundred sixty-seven imaging studies demonstrated innumerable simple pancreatic cysts and 58 complex pancreatic masses: 24 were complex cystic and 34 were solid (30 small [≤2 cm] and 4 large [>2 cm]). Aggregate annual growth was significant in complex cystic and solid masses (mean, 0.39 cm2/y [P = 0.006] and 0.14 cm2/y [P = 0.045]). Solid mass growth differed by size (small: 0.06 cm2/y [range, −0.09 to 0.31 cm2/y]; large: 1.28 cm2/y [range, 0-1.98 cm2/y]). Thirteen masses were excised. No patient developed metastases. Arterial-phase CT improved (P = 0.0003) solid mass detection, but 28% of studies still underreported the total number. Conclusions: Most pancreatic masses in VHL do not require annual surveillance. Arterial-phase CT improves mass detection, but many masses remain prospectively missed.

Inter-radiologist agreement for CT scoring of pediatric splenic injuries and effect on an established clinical practice guideline

BackgroundThe American Pediatric Surgical Association (APSA) advocates for the use of a clinical practice guideline to direct management of hemodynamically stable pediatric spleen injuries. The clinical practice guideline is based on the CT score of the spleen injury according to the American Association for the Surgery of Trauma (AAST) CT scoring system.ObjectiveTo determine the potential effect of radiologist agreement for CT scoring of pediatric spleen injuries on an established APSA clinical practice guideline.Materials and methodsWe retrospectively analyzed blunt splenic injuries occurring in children from January 2007 to January 2012 at a single level 1 trauma center (n = 90). Abdominal CT exams performed at clinical presentation were reviewed by four radiologists who documented the following: (1) splenic injury grade (AAST system), (2) arterial extravasation and (3) pseudoaneurysm. Inter-rater agreement for AAST injury grade was assessed using the multi-rater Fleiss kappa and Kendall coefficient of concordance. Inter-rater agreement was assessed using weighted (AAST injury grade) or prevalence-adjusted bias-adjusted (binary measures) kappa statistics; 95% confidence intervals were calculated. We evaluated the hypothetical effect of radiologist disagreement on an established APSA clinical practice guideline.ResultsInter-rater agreement was good for absolute AAST injury grade (kappa: 0.64 [0.59–0.69]) and excellent for relative AAST injury grade (Kendall w: 0.90). All radiologists agreed on the AAST grade in 52% of cases. Based on an established clinical practice guideline, radiologist disagreement could have changed the decision for intensive care management in 11% (10/90) of children, changed the length of hospital stay in 44% (40/90), and changed the time to return to normal activity in 44% (40/90).ConclusionRadiologist agreement when assigning splenic AAST injury grades is less than perfect, and disagreements have the potential to change management in a substantial number of pediatric patients.

Clearing the Posttraumatic Adult Cervical Spine

More than 13 million patients with trauma at risk for cervical spine (c-spine) injury are treated in emergency departments in the United States and Canada each year.1 C-spine injuries are present in approximately 2% to 10% of trauma cases, with more than 10,000 new patients per year.2 Given the potential for disastrous consequences in delayed or missed diagnosis, clearance of the c-spine in a trauma patient is of paramount importance. Clearance of the c-spine is defined as the determination of the absence of c-spine injury and is an important task that must be performed accurately and expeditiously. Today, with the advent of and dramatic improvement in cross-sectional imaging, the diagnostic radiologist has become an important member of the management team of patients with c-spine and multitrauma injuries.

Post-traumatic penile pseudoaneurysm causing high-flow priapism

A 7-year-old boy presented to the ED with an 8-day history of continuous, painless priapism which began following a straddle-type injury to the groin during a bicycle accident. On physical exam, the patient’s phallus was fully erect and straight. Mild swelling was noted at the penoscrotal junction but no perineal ecchymosis or swelling was present. The testicles were unremarkable, without tenderness or visible signs of injury such as swelling or bruising. The patient denied hematuria or any difficulty with urination. Ultrasonography of the penis was performed which demonstrated the presence of color Doppler flow in the cavernosal arteries. A small, contained outpouching of color Doppler flow along the left cavernosal artery demonstrated arterial flow on spectral analysis, consistent with a pseudoaneurysm (Figs. 1 and 2). Based on the history of perineal straddle injury and the duplex ultrasonography findings, the diagnosis of high-flow priapism was made. It was elected to treat the patient conservatively with close observation alone. Over the course of a month, the priapism subsided with full resolution of penile tumescence. Follow-up color duplex ultrasonography was normal, demonstrating resolution of the cavernosal pseudoaneurysm. Discussion