THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm

Reprint of: Extracellular matrix as a biological scaffold material: Structure and function.

https://www.lfb.lv/files/ESVS-AAA-guidelines.pdf

Management of abdominal aortic aneurysms clinical practice guidelines of the European society for vascular surgery.

"Graefe's Archive" is a distinguished international journal that presents original clinical reports and clinically relevant experimental studies. Founded in 1854 by Albrecht von Graefe to serve as a source of useful clinical information and a stimulus for discussion, the journal has published articles by leading ophthalmologists and vision research scientists for more than a century. With peer review by an international Editorial Board and prompt English-language publication, "Graefe's Archive" provides rapid dissemination of clinical and clinically related experimental information.

Graefe's archive for clinical and experimental ophthalmology

The effects of aneurysm on the biaxial mechanical behavior of human abdominal aorta

Rupture of abdominal aortic aneurysm (AAA) represents a significant clinical event, having a mortality rate of 90% and being currently ranked as the 13th leading cause of death in the US. The ability to reliably evaluate the susceptibility of a particular AAA to rupture on a case-specific basis could vastly improve the clinical management of these patients. Because AAA rupture represents a mechanical failure of the degenerated aortic wall, biomechanical considerations are important to understand this process and to improve our predictions of its occurrence. Presented here is an overview of research to date related to the biomechanics of AAA rupture. This includes a summary of results related to ex vivo and in vivo mechanical testing, noninvasive AAA wall stress estimations, and potential mechanisms of AAA wall weakening. We conclude with a demonstration of a biomechanics-based approach to predicting AAA rupture on a patient-specific basis, which may ultimately prove to be superior to the widely and currently used maximum diameter criterion.

Biomechanical Determinants of Abdominal Aortic Aneurysm Rupture

https://www.jvascsurg.org/article/S0741-5214(05)01921-X/pdf

Biomechanical properties of ruptured versus electively repaired abdominal aortic aneurysm wall tissue.

The spatial distributions of both wall stress and wall strength are required to accurately evaluate the rupture potential for an individual abdominal aortic aneurysm (AAA). The purpose of this study was to develop a statistical model to non-invasively estimate the distribution of AAA wall strength. Seven parameters–namely age, gender, family history of AAA, smoking status, AAA size, local diameter, and local intraluminal thrombus (ILT) thickness–were either directly measured or recorded from the patients hospital chart. Wall strength values corresponding to these predictor variables were calculated from the tensile testing of surgically procured AAA wall specimens. Backwards–stepwise regression techniques were used to identify and eliminate insignificant predictors for wall strength. Linear mixed-effects modeling was used to derive a final statistical model for AAA wall strength, from which 95% confidence intervals on the model parameters were formed. The final statistical model for AAA wall strength consisted of the following variables: sex, family history, ILT thickness, and normalized transverse diameter. Demonstrative application of the model revealed a unique, complex wall strength distribution, with strength values ranging from 56 N/cm2 to 133 N/cm2. A four-parameter statistical model for the noninvasive estimation of patient-specific AAA wall strength distribution has been successfully developed. The currently developed model represents a first attempt towards the noninvasive assessment of AAA wall strength. Coupling this model with our stress analysis technique may provide a more accurate means to estimate patient-specific rupture potential of AAA.

Towards a noninvasive method for determination of patient-specific wall strength distribution in abdominal aortic aneurysms.

Abdominal aortic aneurysms (AAAs) can typically remain stable until the strength of the aortic wall is unable to withstand the forces acting on it as a result of the luminal blood pressure, resulting in AAA rupture. The clinical treatment of AAA patients presents a dilemma for the surgeon: surgery should only be recommended when the risk of rupture of the AAA outweighs the risks associated with the interventional procedure. Since AAA rupture occurs when the stress acting on the wall exceeds its strength, the assessment of AAA rupture should include estimates of both wall stress and wall strength distributions. The present work details a method for noninvasively assessing the rupture potential of AAAs using patient-specific estimations the rupture potential index (RPI) of the AAA, calculated as the ratio of locally acting wall stress to strength. The RPI was calculated for thirteen AAAs, which were broken up into ruptured (n = 8 and nonruptured (n = 5) groups. Differences in peak wall stress, minimum strength and maximum RPI were compared across groups. There were no statistical differences in the maximum transverse diameters (6.8 +/- 0.3 cm vs. 6.1 +/- 0.5 cm, p = 0.26) or peak wall stress (46.0 +/- 4.3 vs. 49.9 +/- 4.0 N/cm(2), p = 0.62) between groups. There was a significant decrease in minimum wall strength for ruptured AAA (81.2 +/- 3.9 and 108.3 +/- 10.2 N/cm(2), p = 0.045). While the differences in RPI values (ruptured = 0.48 +/- 0.05 vs. nonruptured = 0.36 +/- 0.03, respectively; p = 0.10) did not reach statistical significance, the p-value for the peak RPI comparison was lower than that for both the maximum diameter (p = 0.26) and peak wall stress (p = 0.62) comparisons. This result suggests that the peak RPI may be better able to identify those AAAs at high risk of rupture than maximum diameter or peak wall stress alone. The clinical relevance of this method for rupture assessment has yet to be validated, however, its success could aid clinicians in decision making and AAA patient management.

Jonathan P. Vande Geest

Papers

The effects of aneurysm on the biaxial mechanical behavior of human abdominal aorta

Biomechanical Determinants of Abdominal Aortic Aneurysm Rupture

Biomechanical properties of ruptured versus electively repaired abdominal aortic aneurysm wall tissue.

Towards a noninvasive method for determination of patient-specific wall strength distribution in abdominal aortic aneurysms.

A biomechanics-based rupture potential index for abdominal aortic aneurysm risk assessment: demonstrative application.