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Accepted Manuscripts

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research-article  
reem Yassine, Mohammad Karim Elham, Samir Mustapha and Ramsey Hamade
ASME J of Medical Diagnostics   doi: 10.1115/1.4038448
Where heterogeneous material considerations may yield more accurate estimates of long bones' modal characteristics, homogeneous description yields faster approximate solutions. Here, modal frequencies of (bovine) long tibia bones are numerically estimated using the finite element method (ANSYS) starting from anatomically accurate CT scans. Whole long bones are segmented into cortical and cancellous constituents based on Hounsfield (HU) values. Accurate 3-dimensional models are consequently developed. Bones' cortical and cancellous constituents are first treated as heterogeneous material. Relative to stiffness-density relations, stiffness values are assigned for each element yielding a stiffness-graded structure. Calculated modal frequencies are compared to those measured from dynamic experiments. Analysis was repeated where bone properties are homogenized by averaging the stiffness properties of bone constituents. Compared with experimental values of one control long bone, the heterogeneous material assumption returned good estimates of the frequency values in the cranial-caudal (CC) plane with of +0.85% for mode 1 and +10.66% for mode 2. For homogeneous material assumption, underestimates were returned with error values of -13.25% and -0.13 % differences for mode 2. In the medial-lateral (ML) plane, heterogeneous material assumption returned good frequency estimates with -8.89% for mode 1 and +1.01% for mode 2. Homogeneous material assumption underestimated the frequency values with error of -20.52% for mode 1 and -7.50% for mode 2. Homogeneous simplifications yielded faster and more memory-efficient FEM runs with heterogeneous modal analysis requiring 1.5 more running time and twice the utilized memory.
TOPICS: Bone, Stiffness, Errors, Finite element methods, Density, Computerized tomography, Three-dimensional models, Modal analysis
research-article  
Jennifer Wagner, Bruce F. Landeck II and Kendall Hunter
ASME J of Medical Diagnostics   doi: 10.1115/1.4038408
Background: Changes in left ventricular (LV) shape are observed in patients with pulmonary hypertension (PH). Quantification of ventricular shape could serve as a tool to non-invasively monitor pediatric patients with PH. Decomposing the shape of a ventricle into a series of components and magnitudes will facilitate differentiation of healthy and PH subjects. Methods: Parasternal short axis echo images acquired from 53 pediatric subjects with PH and 53 age and sex-matched normal control subjects underwent speckle tracking using Velocity Vector Imaging (Siemens) to produce a series of x,y coordinates tracing the LV endocardium in each frame. Coordinates were converted to polar format after which the Fourier transform was used to derive shape component magnitudes in each frame. Magnitudes of the first 11 components were normalized to heart size (magnitude/LV length as measured on apical view) and analyzed across a single cardiac cycle. Logistic regression was used to test predictive power of the method. Results: Fourier decomposition produced a series of shape components from short axis echo views of the LV (Figure 1). All 11 components analyzed were significantly different between groups (Figure 2). The accuracy index of the receiver operator curve was 0.85. Conclusion: Quantification of LV shape can differentiate normal pediatric subjects from those with PH. Shape analysis is a promising method to precisely describe shape changes observed in PH. Differences between groups speak to intraventricular coupling that occurs in right ventricular overload. Further analysis investigating the correlation of shape to clinical parameters is underway.
TOPICS: Pediatrics, Shapes, Echoes, Fourier transforms, Imaging, Cardiac cycle
Review Article  
Alison Vogell, Hannah Burley, Matthew Ware, Valena J Wright, Irene Georgakoudi and Thomas Schnelldorfer
ASME J of Medical Diagnostics   doi: 10.1115/1.4038360
Objective: Novel imaging technologies continued to be introduced into the operative setting. In particular, novel image-enhanced laparoscopic techniques are being explored for use in gynecologic operations. This systematic review describes these technologies in four relevant areas of gynecologic surgery. Methods: The PubMed database was searched for human, English-language studies, and the reference lists of retrieved articles were reviewed. An analysis of pooled data from 34 studies that met inclusion criteria was performed. Results: The results suggest that image-enhanced technology may be useful in several common gynecologic procedures. Auto- and drug-enhanced fluorescence laparoscopy allow for increased detection of non-pigmented endometriotic lesions. Using these technologies for peritoneal staging of ovarian malignancy is of uncertain benefit. Drug-enhanced fluorescence laparoscopy for sentinel lymph node detection in patients with uterine or cervical malignancy is feasible, showing a high rate of sentinel lymph node detection, but a low sensitivity of identifying metastases. Finally, their use in intra-operative visualization of the ureter is promising. Conclusion: The majority of available data was from feasibility studies with limited sample sizes. Nevertheless, the results described in this systematic review support the expectation that these upcoming image-enhanced laparoscopy techniques will play a more important role in the future care of gynecologic patients.
TOPICS: Surgery, Imaging, Fluorescence, Drugs, Cancer, Databases, Visualization

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