Motion-based microwave tomographic measurement device for three-dimensional coverage in a magnetic resonance system.

PURPOSE: We have developed a fully 3D data acquisition system for microwave breast imaging which can operate simultaneously inside a magnetic resonance imaging (MRI). MRI is used regularly for breast imaging to distinguish tumors from normal tissue. It generally has poor specificity unless used with a gadolinium contrast agent. Microwave imaging could fill this need because of the good endogenous tumor:normal tissue property contrast, especially in light of safety concerns for gadolinium. The antenna array consists of 16 monopole antennas positioned in a horizontal circle surrounding the breast which can then be moved vertically for 3D coverage of the breast. The tank system materials were chosen to minimize artifacts in the MR image within the specific shared imaging zone. The support rods are stainless steel, albeit positioned sufficiently far from the imaging target to have little effect. The mechanical motion parts are all 3D printed plastic. Unlike many conventional antennas, the monopoles consist of just the center conductor and insulator of the coaxial cable, making it one of the least possible metallic structures. METHODS: Data were acquired both inside and outside of the MR bore to confirm that the MR bore did not have adverse effects on the microwave imaging process. The imaging tank was filled with a mixture of glycerin and water to both provide a reasonable property match to the phantom and to highly attenuate the fields which also acted to suppress multi-path signals. Microwave images were reconstructed using our Gauss-Newton scheme combined with a log transformation for a more linear convergence. MR images were also acquired to assess the effects of the microwave tank structures on the imaging. RESULTS: The microwave measurement data were acquired in log magnitude and phase format at 200 MHz increments from 700-1900 MHz. Each antenna acted sequentially as a transmitter while the complement of 15 acted as a receiver. The single frequency images were reconstructed using a Gauss-Newton iterative technique with a standard log transformation to linearize the process. The data showed that the signal strengths were between 7-10 dB lower for the case when the array was inside the MRI versus when not. Notwithstanding, the image quality was still high because of the significant signal to noise ratio. The reconstructed images in both situations demonstrated good 3D object recovery of the vertically size and shaped varying object. The MR images were not adversely affected by the presence of antennas or feed structures. CONCLUSIONS: We have demonstrated that our technique can recover high-quality images of a 3D varying object within an MRI system. Compatibility issues have been addressed for both the microwave and MRI systems. The reduced SNR for the case operating in the MRI did not adversely affect the images. To the best of our knowledge, this is the first example of a microwave imaging system operating in an MRI with full 3D volumetric capability.

Community-Based HIV Testing for Urban Youth in Western Kenya.

Youth aged 15-24 years comprise 48% of new HIV infections and 15% of persons living with HIV in Kisumu County, Kenya. We assessed factors associated with HIV infection among youth participating in the Community Health Initiative (CHI) implemented in an urban informal settlement in 2018. Predictors of HIV infection were assessed by multivariable logistic regression. CHI engaged 4,441 youth through community health campaigns and home-based HIV testing. HIV prevalence was 3.5% overall and 7.1% among young women aged 20-24. There were 24 youth newly identified as HIV-positive out of 157 total HIV-positive youth. HIV-positive status was positively associated with being female (aOR = 2.46; 95% CI 1.57, 3.84) and aged 20-24 (aOR = 2.40; 95% CI 1.52, 3.79), and inversely associated with secondary school education or higher (aOR = 0.27; 95% CI 0.16, 0.44). Our findings highlight the need for HIV prevention programs specially tailored for youth to further reduce new HIV infections in this priority population.

Community-based HIV testing services in an urban setting in western Kenya: a programme implementation study.

BACKGROUND: Some countries are struggling to reach the UNAIDS target of 90% of all individuals with HIV knowing their HIV status, especially among men and youth. To identify individuals who are unaware of their HIV-positive status and achieve testing saturation, we implemented a hybrid HIV testing approach in an urban informal settlement in western Kenya. In this study, we aimed to describe the uptake of HIV testing and linkage to care and treatment during this programme. METHODS: The Community Health Initiative involved community mapping, household census, multidisease community health campaigns, and home-based tracking in the informal settlement of Obunga in Kisumu, Kenya. 52 multidisease community health campaigns were held throughout the programme coverage area, at which HIV testing by certified testing service counsellors was one of the health services available. Individuals aged 15 years or older who were not previously identified as HIV-positive, children younger than 15 years who reported being sexually active or for whom testing was requested by a parent or guardian, and individuals who tested HIV-negative within the past 3 months but who reported a recent risk were all eligible for testing. Health and counselling services were tailored for men and youth to encourage their participation. Individuals identified during the census who did not attend a community health campaign were tracked using global positioning system data and offered home-based HIV testing services. We calculated the previously unidentified fraction, defined as the number of individuals who were newly identified as HIV-positive as a proportion of all individuals previously identified and newly identified as HIV-positive. FINDINGS: Between Jan 11 and Aug 29, 2018, the Community Health Initiative programme reached 23 584 individuals, of whom 11 526 (48·9%) were men and boys and 5635 (23·9%) were aged 15-24 years. Of 12 769 individuals who were eligible for HIV testing, 12 407 (97·2%) accepted testing, including 3917 (31·6%) first-time testers. 101 individuals were newly identified as HIV-positive out of 1248 total individuals who were HIV-positive, representing an 8·1% previously unidentified fraction. The previously unidentified fraction was highest among men (9·8%) and among people aged 15-24 years (15·3%). INTERPRETATION: Community-based hybrid HIV testing was successfully implemented in an urban setting. Innovative approaches that make HIV testing more accessible and acceptable, particularly to men and young people, are crucial for achieving testing and treatment saturation. Focusing on identifying individuals who are unaware of their HIV-positive status in combination with monitoring the previously unidentified fraction has the potential to achieve the UNAIDS Fast Track commitment to end AIDS by 2030. FUNDING: US President's Emergency Plan for AIDS Relief through the US Centers for Disease Control and Prevention.