Ultrasound stimulated acoustic emission for monitoring thermal surgery

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (leaves 88-93).Therapeutic ultrasound describes a non-invasive surgical technique by which high-energy ultrasound is delivered to malignant tissue. This method must be monitored in order to ensure that the correct tissues are treated and that the tissues are treated with the proper dose. Typically, therapeutic ultrasound has relied on MRI techniques to monitor the extent of the thermal surgery. Besides for the great cost and limited availability, MRI monitoring presents limitations for therapeutic equipment design because all other equipment must be compatible with the large magnetic fields created by the MRI system. A new method of monitoring is explored which uses a method coined Ultrasound Stimulated Acoustic Emission, USAE. This relatively new material property measurement method presented by M. Fatemi and J.F. Greenleaf in Science May 1998 relies on the low frequency stimulation of a material by overlapping two slightly differing high frequency ultrasound beams in a pattern which creates a region of low frequency, known as a beat frequency. The resulting low frequency stimulus is highly focused and localized. The low frequency pressure field causes cyclic forces and induces a mechanical displacement in the object being imaged. The low frequency response of the object from the ultrasound stimulus reveals information about the mechanical and ultrasound properties of the object, namely its stiffness and acoustical absorption coefficient. A diagnostic ultrasound system applying the USAE method for imaging biological tissues was designed and constructed for use in this thesis. In a series of experiments presented in this thesis, the USAE method is applied to imaging ex vivo porcine and rabbit tissue. Lesions are created with focused ultrasound and raster scanned in the focal plane by the two intersecting focused ultrasound fields to image the necrosed tissue. This method successfully rendered high-resolution images of the necrosed lesions. In addition, the amplitude of the USAE responses correlate well with temperature measurements in a study of nine samples of porcine fat and nine samples of porcine muscle. Evidence including a broadband response and fluctuating USAE amplitude indicate that the USAE method may also be used to detect cavitation events in tissue. The images and the temperature measurements demonstrate the effectiveness of the USAE method for imaging and monitoring biological tissue in conjunction with thermal therapy.by Jonathan S. Thierman.S.M

Sources of difference frequency sound in a dual-frequency imaging system with implications for monitoring thermal surgery

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2004.Includes bibliographical references (leaves 138-145).(cont.) parametric effect, which can be considered an imaging artifact. Additionally, it may be possible to use the nonlinear interaction of scattered waves to form images that rely on the presence of small scatterers; a technique that may be enhanced with the use of contrast agents containing small scattering micro-bubbles in vivo.This thesis explores the nature of the ultrasound-stimulated vibro-acoustography (USVA) imaging method introduced by Fatemi and Greenleaf in 1998. The USVA method relies upon the generation of a difference frequency signal from the interaction of two pressure fields with a target. A thorough understanding of USVA will be necessary to further advance this dual-frequency method. Prior studies demonstrate a correlation between difference frequency signal response and tissue temperature, and difference frequency signal response and tissue coagulation, suggesting that USVA may be well suited for monitoring focused ultrasound surgery. This thesis explores three possible sources of the difference frequency signal: 1) the parametric effect, 2) linear reflection of the local difference frequency field, and 3) nonlinear interaction of linearly scattered waves. The research compares the relative significance of these three possible sources using mathematical analysis, computer simulations, and experimental results. The results set forth in this thesis suggest that the parametric effect may be the most significant source of difference frequency signal, reaching pressures of 1-10 Pa and significantly overshadowing the other two enumerated effects. The second effect, the linear reflection of the local evanescent difference frequency field, is undetectable experimentally. Finally, the third effect, the nonlinear interaction of linearly scattered waves for a single bubble, contributes to the difference frequency signal only slightly, albeit detectably, reaching levels of .1-1 Pa. These results have a number of implications for future implementations of USVA. In order to utilize USVA as a successful imaging tool, one must take measures to avoid the signal from theby Jonathan S. Thierman.Ph.D

Speciesistic Veganism: An Anthropocentric Argument

The paper proposes an anthropocentric argument for veganism based on a speciesistic premise that most carnists likely affirm: human flourishing should be promoted. I highlight four areas of human suffering promoted by a carnistic diet: (1) health dangers to workers (both physical and psychological), (2) economic dangers to workers, (3) physical dangers to communities around slaughterhouses, and (4) environmental dangers to communities-at-large. Consequently, one could ignore the well-being of non-human animals and nevertheless recognize significant moral failings in the current standard system of meat production

Robotic milking technologies and renegotiating situated ethical relationships on UK dairy farms

Robotic or automatic milking systems (AMS) are novel technologies that take over the labor of dairy farming and reduce the need for human-animal interactions. Because robotic milking involves the replacement of 'conventional' twice-a-day milking managed by people with a system that supposedly allows cows the freedom to be milked automatically whenever they choose, some claim robotic milking has health and welfare benefits for cows, increases productivity, and has lifestyle advantages for dairy farmers. This paper examines how established ethical relations on dairy farms are unsettled by the intervention of a radically different technology such as AMS. The renegotiation of ethical relationships is thus an important dimension of how the actors involved are re-assembled around a new technology. The paper draws on in-depth research on UK dairy farms comparing those using conventional milking technologies with those using AMS. We explore the situated ethical relations that are negotiated in practice, focusing on the contingent and complex nature of human-animal-technology interactions. We show that ethical relations are situated and emergent, and that as the identities, roles, and subjectivities of humans and animals are unsettled through the intervention of a new technology, the ethical relations also shift. © 2013 Springer Science+Business Media Dordrecht

Availability of supplies and motivations for accessing voluntary HIV counseling and testing services in Blantyre, Malawi

<p>Abstract</p> <p>Background</p> <p>HIV counseling and testing is an important intervention in the prevention, control and management of the human immunodeficiency virus (HIV). Counseling and testing can be an entry point for prevention, care and support. Knowledge of the quality of services and motivations for testing by individuals is important for effective understanding of the testing environment.</p> <p>Methods</p> <p>A cross sectional explorative study of clients accessing HIV voluntary counseling and testing (VCT) and counselors was conducted in 6 government health centers in Blantyre City, Malawi. We aimed to assess the availability of critical clinic supplies and identify the motivations of clients seeking counseling and testing services. We also aimed to identify the health professional cadres that were providing VCT in Blantyre city.</p> <p>Results</p> <p>102 VCT clients and 26 VCT counselors were interviewed. Among the VCT clients, 74% were <=29 years, 58.8% were females and only 7% reported no formal education. 42.2% were single, 45.1% married, 8.8% widowed and 3.9% divorced or separated. The primary reasons for seeking HIV counseling and testing were: recent knowledge about HIV (31.4%), current illness (22.5%), self-assessment of own behavior as risky (15.5%), suspecting sexual partner's infidelity (13.7%) and seeking HIV confirmatory test (9.8%) and other reasons (6.9%). Of the 26 VCT counselors, 14 were lay volunteers, 7 health surveillance assistants and 5 nurses. All except one had been trained specifically for HIV counseling and testing. All 6 facilities were conducting rapid HIV testing with same day test results provided to clients. Most of the supplies were considered adequate for testing.</p> <p>Conclusion</p> <p>HIV counseling and testing facilities were available in Blantyre city in all the six public health facilities assessed. The majority of counseling and testing clients were motivated by perceptions of being at risk of HIV infection. In a country with 12% of individuals 15 to 49 years infected, there is need to encourage testing among population groups that may not perceive themselves to be at risk of infection.</p

Burnout and use of HIV services among health care workers in Lusaka District, Zambia: a cross-sectional study

BACKGROUND: Well-documented shortages of health care workers in sub-Saharan Africa are exacerbated by the increased human resource demands of rapidly expanding HIV care and treatment programmes. The successful continuation of existing programmes is threatened by health care worker burnout and HIV-related illness. METHODS: From March to June 2007, we studied occupational burnout and utilization of HIV services among health providers in the Lusaka public health sector. Providers from 13 public clinics were given a 36-item, self-administered questionnaire and invited for focus group discussions and key-informant interviews. RESULTS: Some 483 active clinical staff completed the questionnaire (84% response rate), 50 staff participated in six focus groups, and four individuals gave interviews. Focus group participants described burnout as feeling overworked, stressed and tired. In the survey, 51% reported occupational burnout. Risk factors were having another job (RR 1.4 95% CI 1.2-1.6) and knowing a co-worker who left in the last year (RR 1.6 95% CI 1.3-2.2). Reasons for co-worker attrition included: better pay (40%), feeling overworked or stressed (21%), moving away (16%), death (8%) and illness (5%). When asked about HIV testing, 370 of 456 (81%) reported having tested; 240 (50%) tested in the last year. In contrast, discussion groups perceived low testing rates. Both discussion groups and survey respondents identified confidentiality as the prime reason for not undergoing HIV testing. CONCLUSION: In Lusaka primary care clinics, overwork, illness and death were common reasons for attrition. Programmes to improve access, acceptability and confidentiality of health care services for clinical providers and to reduce workplace stress could substantially affect workforce stability