A novel motion compensation algorithm for acoustic radiation force elastography.

A novel method of physiological motion compensation for use with radiation force elasticity imaging has been developed. The method utilizes a priori information from finite element method models of the response of soft tissue to impulsive radiation force to isolate physiological motion artifacts from radiation force-induced displacement fields. The new algorithmis evaluated in a series of clinically realistic imaging scenarios, and its performance is compared to that achieved with previously described motion compensation algorithms. Though not without limitations, the new model-based motion compensation algorithm performs favorably in many circumstances and may be a logical choice for use with in vivo abdominal imaging.

In vivo visualization of abdominal malignancies with acoustic radiation force elastography.

The utility of acoustic radiation force impulse (ARFI) imaging for real-time visualization of abdominal malignancies was investigated. Nine patients presenting with suspicious masses in the liver (n = 7) or kidney (n = 2) underwent combined sonography/ARFI imaging. Images were acquired of a total of 12 tumors in the nine patients. In all cases, boundary definition in ARFI images was improved or equivalent to boundary definition in B-mode images. Displacement contrast in ARFI images was superior to echo contrast in B-mode images for each tumor. The mean contrast for suspected hepatocellular carcinomas (HCCs) in B-mode images was 2.9 dB (range: 1.5-4.2) versus 7.5 dB (range: 3.1-11.9) in ARFI images, with all HCCs appearing more compliant than regional cirrhotic liver parenchyma. The mean contrast for metastases in B-mode images was 3.1 dB (range: 1.2-5.2) versus 9.3 dB (range: 5.7-13.9) in ARFI images, with all masses appearing less compliant than regional non-cirrhotic liver parenchyma. ARFI image contrast (10.4 dB) was superior to B-mode contrast (0.9 dB) for a renal mass. To our knowledge, we present the first in vivo images of abdominal malignancies in humans acquired with the ARFI method or any other technique of imaging tissue elasticity.

Liver ablation guidance with acoustic radiation force impulse imaging: challenges and opportunities.

Previous studies have established the feasibility of monitoring radiofrequency (RF) ablation procedures with acoustic radiation force impulse (ARFI) imaging. However, questions remained regarding the utility of the technique in clinically realistic scenarios and at scanning depths associated with abdominal imaging in adults. We address several of these issues and detail recent progress towards the clinical relevance of the ARFI technique. Results from in vitro bovine tissues and an in vivo ovine model are presented. Additional experiments were conducted with a tissue-mimicking phantom and parallel receive tracking techniques in order to further support the clinical feasibility of the method. Thermal lesions created during RF ablation are visualized with high contrast in both in vitro and in vivo hepatic tissues, and radial lesion growth can be monitored throughout the duration of the procedure. ARFI imaging is implemented on a diagnostic ultrasonic scanner, and thus may be a convenient option to guide RF ablation procedures, particularly when electrode insertion is also performed with sonographic guidance.

Frequency of nonparenteral occupational exposures to blood and body fluids before and after universal precautions training.

PURPOSE: During annual periods before and after Universal Precautions training, we compared the frequency of health care workers' self-reported cutaneous exposures to blood and various body substances from any patient and from patients presumed infected with human immunodeficiency virus type 1 (HIV-1). SUBJECTS AND METHODS: Self-reported cutaneous exposures to blood, sputum, urine, feces, and other body substances were evaluated separately in 559 workers during the first survey and 269 workers during the second. RESULTS: Mean annual blood exposures decreased from 35.8 to 18.1, and mean annual exposures to all substances decreased from 77.8 to 40.0 (p less than 0.001 for both determinations). Two matched analyses of a subset of 200 participants who completed both surveys had similar results. Reported exposures to blood, presumably infectious blood, sputum, presumably infectious sputum, and urine were significantly decreased. Participants were tested for antibodies to HIV-1; no participant reporting cutaneous exposures acquired HIV-1 infection. The upper bound for the 95% confidence interval for the risk of HIV-1 infection associated with a single cutaneous exposure was 0.04% for blood presumed to contain HIV-1 and 0.02% for any body substance presumed to contain HIV-1. CONCLUSIONS: These data suggest that Universal Precautions training significantly decreased but did not eliminate cutaneous exposures to blood and body substances. The results further suggest that the risk for HIV-1 infection associated with cutaneous exposures is substantially lower than the risk associated with parenteral exposures.

Risk for occupational transmission of human immunodeficiency virus type 1 (HIV-1) associated with clinical exposures. A prospective evaluation.

OBJECTIVES: To summarize the results of a 6-year, ongoing, prospective study of the risk for human immunodeficiency virus type 1 (HIV-1) transmission among health care workers, and to estimate the magnitude of the risk for HIV-1 infection associated with different types of occupational exposures. DESIGN: Prospective cohort study; the median follow-up for employees sustaining parenteral exposures was 30.2 months (range, 6 to 69 months). SUBJECTS: Health care workers at the Clinical Center, National Institutes of Health, including those reporting parenteral and nonparenteral occupational exposures to HIV-1. MEASUREMENTS AND MAIN RESULTS: One thousand three hundred and forty-four clinical health care workers reported 179 percutaneous and 346 mucous membrane exposures to fluids from HIV-1-infected patients during a 6-year period. Responding to a supplementary questionnaire, 559 of these workers reported 2712 cutaneous exposures to blood from HIV-1-infected patients and more than 10,000 cutaneous exposures to blood from all patients during a 12-month period. Occupational transmission of HIV-1 occurred in a single worker after a parenteral exposure to blood from an HIV-1-infected patient. No infections occurred after either mucous membrane or cutaneous exposures to blood from HIV-1-infected patients. Use of newer diagnostic technologies (for example, antigen detection, gene amplification) has not resulted in the identification of occupationally transmitted seronegative infections. CONCLUSIONS: Combining our results with those of other prospective studies, the risk for HIV-1 transmission associated with a percutaneous exposure to blood from an HIV-1-infected patient is approximately 0.3% per exposure (95% CI, 0.13% to 0.70%); the risks associated with occupational mucous membrane and cutaneous exposures are likely to be substantially smaller. These data support the use of barrier precautions and suggest a need for strategies that change health care providers' attitudes and behaviors.

Risky business: using necessarily imprecise casualty counts to estimate occupational risks for HIV-1 infection.

Although the genesis of healthcare worker anxiety regarding occupational risks of HIV-1 infection is clear, the reasons for continued insistence on a meticulous "casualty count" become less clear with time. One could, in fact, argue that the precise number of such infections has become virtually meaningless, because the routes of occupational/nosocomial transmission of HIV-1 and the magnitude of risk for infection following an adverse exposure in the healthcare setting have been well-characterized. Nevertheless, with the substantial limitations of these data clearly in mind, we have summarized the numbers of healthcare workers reported to have HIV-1 infection in each of the above categories in Table 2. The likelihood that an individual case represents true occupational infection decreases as one moves down the table. Having waded through the depths of this literature, we have reached the conclusion that, of the available data, the magnitude of risk for occupational HIV-1 infection remains the single most useful and instructive statistic available. Longitudinal cohort studies of HCWs involved in the day-to-day care of HIV-1-infected patients and in the handling and processing of specimens from such patients provide the best available evidence regarding the magnitude of risk for transmission of this virus in the healthcare setting. Fourteen prospective studies are currently in progress, with approximately 2,000 HCWs enrolled (Table 4). Six HCWs enrolled in these studies have developed serologic evidence of HIV-1 infection following percutaneous exposures, yielding an infection rate per participant of 0.32% and an infection rate per exposure of 0.31%.(ABSTRACT TRUNCATED AT 250 WORDS)