Atherosclerosis and Abdominal Aortic Aneurysms (AAAs) are two of the most common vascular diseases. Current clinical criteria in monitoring and risk assessment of these diseases exhibit profound weaknesses. Since both diseases are associated with mechanical changes in the arterial wall, Pulse Wave Imaging (PWI), a technique developed by our group to assess and quantify the mechanical properties of the aortic wall in vivo, may provide valuable diagnostic information. However, using PWI to acquire a single regional Pulse Wave Velocity (PWV) value of the entire imaged section of the diseased artery would not provide sufficiently localized information on the pathology. Hence, the implementation of piecewise Pulse Wave Imaging (pPWI) aims at addressing the issue of focal vascular disease. The feasibility of this novel technique is tested on murine normal, aneurysmal and atherosclerotic arteries in order to assess its effectiveness in monitoring each disease. Sub-regional PWVs were then estimated within 2-4 mm segments along the length of the arterial wall and estimates of the local stiffness of each segment referred to as local PWI Modulus (EPWI) values were calculated using the Moens-Korteweg equation. Stiffness maps were constructed for each case and provided localized spatial information on sub-regional PWV and EPWI measurements. Overall stiffness was found to increase in the atherosclerotic cases. The mean sub-regional PWV was found to be 2.57±0.18 m/s for the normal aortas (n = 7) with a corresponding mean EPWI of 43.82±5.86 kPa. A significant increase (p ≤ 0.001) in the group means of the sub-regional PWVs was found between the normal aortas and the aortas of mice on high-fat diet for 20 (3.30±0.36 m/s) and 30 weeks (3.56±0.29 m/s). The mean of the sub-regional PWVs (1.57±0.78 m/s) and EPWI values (19.23±15.47 kPa) decreased significantly in the aneurysmal aortas (p ≤ 0.05). Furthermore, the mean coefficient of determination (r2) of the normal aortas was significantly higher (p ≤ 0.05) than those of the aneurysmal and atherosclerotic cases. These results demonstrated that pPWI may be able to provide useful biomarkers for monitoring focal vascular diseases.

Purpose:To assess whether the stability of murine aortic aneurysms is associated with the homogeneity of pulse wave propagation within the saccular wall. Materials and Methods:All animal procedures were approved by the institutional Animal Care and Use Committee. Apolipoprotein E and tissue inhibitor of metalloproteinases-1 knockout mice (n = 26) were infused with angiotensin II by using subcutaneously implanted osmotic pumps, with an additional control mouse used for histologic examination (n = 1). Pulse wave imaging (PWI) was performed just before infusion and 15 days after infusion by using 40-MHz ultrasonography at 8000 frames per second (with electrocardiographic gating). Aneurysm appearance on B-mode images was monitored every 2-3 days for 30 days. On the basis of B-mode images obtained after 30 days, aneurysms were deemed to have been unstable if they had ruptured; otherwise, they were deemed stable. Statistical significance was assessed by using two-tailed t tests. Results:In normal aortas, the pulse waves propagated at relatively constant velocities (mean 6 standard deviation, 2.8 m/sec 6 0.9). Fifteen days after infusion, all mice had developed aneurysms, with significant (P , .001/12) changes in maximum anterior-posterior diameter (increase of 54.9% 6 2.5) and pulse wave velocity (PWV) (decrease of 1.3 m/ sec 6 0.8). While there was no significant difference in these parameters (P = .45 for diameter and P = .55 for PWV) between stable aneurysms (n = 12) and unstable aneurysms (n = 14), the standard deviation of the highresolution PWV was significantly higher (P , .001/12) in unstable aneurysms (5.7 m/sec 6 1.6) than in stable ones (3.2 m/sec 6 0.9). Conclusion:High-resolution PWI was used to measure the local homogeneity of pulse wave propagation within the saccular wall, which is lower in unstable aneurysms than in stable ones. Hence, if proven to add additional information beyond size and appearance in human studies, PWI could potentially be used to assess the stability of aneurysms by providing information that is complementary to the anatomic data obtained with conventional B-mode imaging.q RSNA, 2016

The Abdominal Aortic Aneurysm (AAA) is a silent and often deadly vascular disease caused by the localized weakening of the arterial wall. Previous work has shown that local changes in wall stiffness can be detected with Pulse Wave Imaging (PWI), which is a noninvasive technique for tracking the propagation of pulse waves along the aorta at high spatial and temporal resolutions. This study aims at assessing the capability of PWI to monitor and stage AAA progression in a murine model of the disease. ApoE/TIMP-1 knockout mice (N = 18) were given angiotensin II for 30 days via subcutaneously implanted osmotic pumps. The suprarenal sections of the abdominal aortas were imaged every 2-3 days after implantation using a 30 MHz Visualsonics Vevo 770 with 115 μm lateral resolution. Pulse wave propagation was monitored at an effective frame rate of 8 kHz by using retrospective electrocardiogram (ECG) gating and by performing 1-D cross-correlation on the radio-frequency (RF) signals to obtain the displacements induced by the waves. In normal aortas, the pulse waves propagated at constant velocities (2.8±0. 9 m/s, r2 = 0.89±0.11), indicating that the composition of these vessels was relatively homogeneous. In the mice that developed AAAs (N = 10), the wave speeds in the aneurysm sac were 45% lower (1.6±0.6 m/s) and were more variable (r2 = 0.66±0.23). Moreover, the wave-induced wall displacements were at least 80% lower within the sacs compared to the surrounding vessel. Finally, in mice that developed fissures (N = 5) or ruptures (N = 3) at the sites of their AAA, higher displacements directed out of the lumen and with no discernible wave pattern (r2 < 0.20) were observed throughout the cardiac cycle. These findings show that PWI can be used to distinguish normal murine aortas from aneurysmal, fissured, and ruptured ones. Hence, PWI could potentially be used to monitor and stage human aneurysms by providing information complementary to standard B-modes.

Imaging arterial mechanical properties may improve vascular disease diagnosis. Pulse wave velocity (PWV) is a marker of arterial stiffness linked to cardiovascular mortality. Pulse wave imaging (PWI) is a technique for imaging the pulse wave propagation at high spatial and temporal resolution. In this study, we introduce adaptive PWI, a technique for the automated partition of heterogeneous arteries into individual segments characterized by most homogeneous pulse wave propagation, allowing for more robust PWV estimation. This technique was validated in a silicone phantom with a soft-stiff interface. The mean detection error of the interface was 4.67±0.73 mm and 3.64±0.14 mm in the stiff-to-soft and soft-to-stiff pulse wave transmission direction, respectively. This technique was tested in monitoring the progression of atherosclerosis in mouse aortas in vivo (n = 11). PWV was found to already increase at the early stage of 10 weeks of highfat diet (3.17±0.67m/sec compared to baseline 2.55±0.47m/sec, p < 0.05) and further increase after 20 weeks of high-fat diet (3.76±1.20m/sec). The number of detected segments of the imaged aortas monotonically increased with the duration of high-fat diet indicating an increase in arterial wall property inhomogeneity. The performance of adaptive PWI was also tested in aneurysmal mouse aortas in vivo. Aneurysmal boundaries were detected with a mean error of 0.68±0.44mm. Finally, initial feasibility was shown in the carotid arteries of healthy and atherosclerotic human subjects in vivo (n = 3 each). Consequently, adaptive PWI was successful in detecting stiffness inhomogeneity at its early onset and monitoring atherosclerosis progression in vivo.

IntroductionThe Americans with Disabilities Act (ADA) mandates that U.S. institutions of higher education provide "reasonable accommodations" to students with disabilities to ensure equal educational opportunities. However, despite the key role of physics as a gateway to Science, Technology, Engineering and Mathematics (STEM) studies, only limited resources exist for teaching physics to students who are blind or visually impaired. Here we share lessons from our experience creating an accessible physics curriculum for a blind physics major. The authors include the student himself, a blind physics B.S. who graduated from a different institution, a PhD chemist and consultant on STEM accessibility who is himself blind, and several sighted educators and course assistants who worked regularly with the students. This article focuses on issues for which instructors are responsible: how to make class meetings, curricular materials, tutorials and demonstrations accessible (as opposed to accommodations determined at an administrative level, 2 such as additional time on tests). An online appendix provides additional resources and specifics to guide actual implementation of these ideas, including a guide to further reading.Once an institution learns that a blind student will enroll in a physics course, the course instructor and the institutional disabilities coordinator should meet to discuss course logistics well before the semester begins (ideally, over a month or two in advance to allow sufficient lead time). They should begin the process of creating an effective instructional and support team, ensuring key assistive technologies are in place, making all class meetings accessible, and preparing accessible course materials [1].The most fundamental decision is whether to use individualized instruction, in which the student and instructor meet in separate one-on-one tutorials, or mainstreaming, in which the student attends regular class meetings with other students. We primarily used mainstreaming, supplemented with one-on-one instruction. Instructors should work with the student in question to determine which approach is most suitable given their students' individual needs and the available institutional resources. Assembling the instructional teamA blind student who participates in mainstreamed class meetings should have access to one or more persons who act as an in-class assistant and a tutor outside of class. The in-class assistant ensures all class materials are accessible to the student in real-time while also playing the traditional role of a course tutor when appropriate. For example, they might clarify mathematical notation in a complex equation, describe figures drawn on a chalkboard, or explain visual 3 elements in an interactive demonstration. The tutor provides accessibility help as well as playing the traditional role of a course tutor when appropriate. Neither of these roles can be filled by students currently taking the course, since both positions require advanced familiarity with the course material. We had...