Development of microcomputer-based mental acuity tests for repeated-measures studies

The purpose of this report is to detail the development of the Automated Performance Test System (APTS), a computer battery of mental acuity tests that can be used to assess human performance in the presence of toxic elements and environmental stressors. There were four objectives in the development of APTS. First, the technical requirements for developing APTS followed the tenets of the classical theory of mental tests which requires that tests meet set criteria like stability and reliability (the lack of which constitutes insensitivity). To be employed in the study of the exotic conditions of protracted space flight, a battery with multiple parallel forms is required. The second criteria was for the battery to have factorial multidimensionality and the third was for the battery to be sensitive to factors known to compromise performance. A fourth objective was for the tests to converge on the abilities entailed in mission specialist tasks. A series of studies is reported in which candidate APTS tests were subjected to an examination of their psychometric properties for repeated-measures testing. From this work, tests were selected that possessed the requisite metric properties of stability, reliability, and factor richness. In addition, studies are reported which demonstrate the predictive validity of the tests to holistic measures of intelligence

Analysis of refill curve shape in ultrasound contrast agent studies

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135021/1/mp9534.pd

Imaging of joints with laser‐based photoacoustic tomography: An animal study

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134964/1/mp4166.pd

Discrimination of sonographically detected breast masses using frequency shift color Doppler imaging in combination with age and gray scale criteria.

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135358/1/jum2001204343.pd

Histotripsy Homogenization of the Prostate: Thresholds for Cavitation Damage of Periprostatic Structures

Background and Purpose: Histotripsy is a noninvasive, pulsed ultrasound technology that produces mechanically homogenized tissue within targeted volumes. Previous work has demonstrated prostatic tissue debulking in a canine model. The aim was to establish safety thresholds by evaluating histologic changes of urinary sphincter, neurovascular bundle (NVB), and rectum after targeted histotripsy treatment of these critical structures. Materials and Methods: Rectum, urinary sphincter, and NVB in five anesthetized canines were targeted for histotripsy treatment (50 total points). Locations received 1k, 10k, or 100k acoustic pulses (4 microsecond, 1-MHz) at a repetition frequency of 500-Hz. Canine subjects were euthanized immediately (2), survived 3 days (1), or 2 weeks (3) after treatment. Prostates, periprostatic tissue, and rectum were harvested and processed for histology. Results: The sphincter was structurally intact with minimal muscle fiber disruption even after 100k pulses (n=10). Undamaged nerves, arteries, and veins of the NVB were seen despite mechanical homogenization of surrounding loose connective tissue (n=19). The rectum, however, exhibited dose-dependent damage (n=20). 1k pulses yielded mild submucosal hemorrhage. 10k pulses resulted in moderate collagen disruption and focal mucosal homogenization. 100k pulses produced damage to the mucosa and muscularis propria with extensive hemorrhage and collagen disruption. One canine treated with 100k pulses needed early euthanasia (day 3) because of complications from a urine leak. Conclusions: Histotripsy histologic tissue effect varied based on targeted structure with substantial structural preservation of NVB and sphincter. Rectal subclinical damage was apparent after 1k pulses and increased in extent and severity with escalating doses. Future work will include assessment of functional outcomes and refinement of these initial safety thresholds.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90446/1/end-2E2010-2E0648.pd

Microfluidic model of bubble lodging in microvessel bifurcations

The lodging mechanisms and dynamics of cardiovascular gas bubbles are investigated in microfluidic model bifurcations made of poly(dimethylsiloxane). This work is motivated by gas embolotherapy for the potential treatment of cancer by tumor infarction. The results show that the critical driving pressure below which a bubble will lodge in a bifurcation is significantly less than the driving pressure required to dislodge it. From the results the authors estimate that gas bubbles from embolotherapy can lodge in vessels 20 μm20μm or smaller in diameter, and conclude that bubbles may potentially be used to reduce blood flow to tumor microcirculation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87802/2/244103_1.pd

Measurement of Volumetric Flow

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135278/1/jum200625101305.pd

Histotripsy of Rabbit Renal Tissue in Vivo: Temporal Histologic Trends

Background and Purpose: Histotripsy is defined as noninvasive, nonthermal, mechanical (cavitational) tissue ablation. We previously demonstrated the predictable acute tissue effects of histotripsy in rabbit kidney and other tissues. We sought to characterize the appearance and natural history of renal tissue after histotripsy. Materials and Methods: Following Institutional Animal Care Committee approval, the left kidneys of 29 rabbits were treated with 60,000 750-kHz, 15-cycle bursts of ultrasound energy from an 18-element phased-array transducer at a 1-kHz pulse-repetition frequency. The treated kidneys were harvested at 0, 1, 2, 7, 21, or 60 days; fixed in Formalin; then prepared for microscopic analysis with hematoxylin and eosin and trichrome stains. Results: For kidneys harvested acutely (day 0), a contiguous area of finely disrupted tissue was observed containing no recognizable cells or cellular components. Along the boundary of architectural disruption, a border several tubules wide contained cells that were not visibly disrupted but appeared damaged (pyknotic nuclei). At subsequent time intervals, an inflammatory response developed in association with a steadily decreasing area of cellular and architectural disruption. By day 60, only a small fibrous scar persisted adjacent to a wedge of tubular dilation and fibrosis underlying a surface-contour defect. Conclusions: Histotripsy produces mechanical fractionation of cellular and architectural structures. The resultant acellular material appears to be readily reabsorbed within 60 days in the rabbit. This may prove to be a significant advantage for imaging assessment of residual tumor after ablation of renal malignancy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63123/1/end.2007.9915.pd

Spreading of a density front in the K\"untz-Lavall\'ee model of porous media

We analyze spreading of a density front in the K\"untz-Lavall\'ee model of porous media. In contrast to previous studies, where unusual properties of the front were attributed to anomalous diffusion, we find that the front evolution is controlled by normal diffusion and hydrodynamic flow, the latter being responsible for apparent enhancement of the front propagation speed. Our finding suggests that results of several recent experiments on porous media, where anomalous diffusion was reported based on the density front propagation analysis, should be reconsidered to verify the role of a fluid flow