Development and performance of SIAT bPET: a high-resolution and high-sensitivity MR-compatible brain PET scanner using dual-ended readout detectors.

PURPOSE: Positron emission tomography/magnetic resonance imaging (PET/MRI) is a powerful tool for brain imaging, but the spatial resolution of the PET scanners currently used for brain imaging can be further improved to enhance the quantitative accuracy of brain PET imaging. The purpose of this study is to develop an MR-compatible brain PET scanner that can simultaneously achieve a uniform high spatial resolution and high sensitivity by using dual-ended readout depth encoding detectors. METHODS: The MR-compatible brain PET scanner, named SIAT bPET, consists of 224 dual-ended readout detectors. Each detector contains a 26 × 26 lutetium yttrium oxyorthosilicate (LYSO) crystal array of 1.4 × 1.4 × 20 mm3 crystal size read out by two 10 × 10 silicon photomultiplier (SiPM) arrays from both ends. The scanner has a detector ring diameter of 376.8 mm and an axial field of view (FOV) of 329 mm. The performance of the scanner including spatial resolution, sensitivity, count rate, scatter fraction, and image quality was measured. Imaging studies of phantoms and the brain of a volunteer were performed. The mutual interferences of the PET insert and the uMR790 3 T MRI scanner were measured, and simultaneous PET/MRI imaging of the brain of a volunteer was performed. RESULTS: A spatial resolution of better than 1.5 mm with an average of 1.2 mm within the whole FOV was obtained. A sensitivity of 11.0% was achieved at the center FOV for an energy window of 350-750 keV. Except for the dedicated RF coil, which caused a ~ 30% reduction of the sensitivity of the PET scanner, the MRI sequences running had a negligible effect on the performance of the PET scanner. The reduction of the SNR and homogeneity of the MRI images was less than 2% as the PET scanner was inserted to the MRI scanner and powered-on. High quality PET and MRI images of a human brain were obtained from simultaneous PET/MRI scans. CONCLUSION: The SIAT bPET scanner achieved a spatial resolution and sensitivity better than all MR-compatible brain PET scanners developed up to date. It can be used either as a standalone brain PET scanner or a PET insert placed inside a commercial whole-body MRI scanner to perform simultaneous PET/MRI imaging.

A Randomized Controlled Trial to Increase HIV Testing Demand Among Female Sex Workers in Kenya Through Announcing the Availability of HIV Self-testing Via Text Message.

We assessed whether informing female sex workers about the availability of HIV self-testing at clinics in Kenya using text messages would increase HIV testing rates. We selected a sample of 2196 female sex workers registered in an electronic health record system who were irregular HIV testers and randomized them to be sent a text message announcing the availability of (1) HIV self-test kits sent three times (intervention), (2) general HIV testing sent three times (enhanced standard of care [SOC]), or (3) general HIV testing sent one time (traditional SOC). Participants in the intervention arm were significantly more likely to test for HIV during 2-month follow-up compared to those in the enhanced SOC (OR 1.9, p = 0.001). There was no difference in HIV testing between those in the enhanced SOC and the traditional SOC arms. Announcing the availability of HIV self-testing via text message increased HIV testing among this high-risk group.

Announcing the availability of oral HIV self-test kits via text message to increase HIV testing among hard-to-reach truckers in Kenya: a randomized controlled trial.

BACKGROUND: Truckers in sub-Saharan Africa are at higher risk of contracting HIV than the general population. HIV self-testing may be a way to increase testing rates in this high-risk population. The objective of this randomized controlled trial was to assess whether informing truckers who do not test for HIV regularly about the availability of HIV self-testing kits at roadside wellness centers in Kenya using text messages would increase HIV testing rates compared to the current program in which they are sent text messages about the availability of HIV testing in general. METHODS: A sample of 2262 male truckers registered in the North Star Alliance electronic health record system who, based on these records, were not testing for HIV regularly were randomized to one of three study groups in which they were sent text messages about the availability of (1) oral HIV self-test kits at all 8 North Star Alliance Kenya clinics that was sent three times (intervention), (2) HIV testing in general (not self-testing) at all North Star Alliance clinics sent three times (enhanced standard of care [SOC]), or (3) HIV testing in general (not self-testing) at all North Star Alliance clinics sent one time (SOC). We looked at HIV testing over a 2-month study period following the first text. RESULTS: Truckers in the intervention group were significantly more likely to test for HIV compared to those in the enhanced SOC (OR = 2.7, p = 0.009). There was no difference in HIV testing between those in the enhanced SOC and the SOC groups. Of those in the intervention group who tested, 64.5% chose the self-test and 35.5% chose the standard provider-administered blood-based HIV test. Although the intervention more than doubled HIV testing rates, because HIV testing rates were so low in this population (by design as we selected irregular testers), even in the intervention group more than 96% of participants did not test. CONCLUSIONS: Announcing the availability of HIV self-testing via text message increased HIV testing rates among truckers who were not regularly accessing HIV testing. However, self-testing is only a partial solution to increasing testing rates in this hard to reach population. TRIAL REGISTRATION: This trial was registered prior to enrollment at the Registry for International Impact Evaluations (RIDIE STUDY ID: 582a2462ae2ab): http://ridie.3ieimpact.org/index.php?r=search/detailView&id=492 . It was also registered after completion at ClinicalTrials.gov ( ClinicalTrials.gov Identifier: NCT03662165): https://clinicaltrials.gov/ct2/show/NCT03662165?term=NCT03662165&type=Intr&cond=HIV&rank=1 .

Effect of depth of interaction resolution on the spatial resolution of SIAT aPET.

Objective.Spatial resolution is a crucial parameter for a positron emission tomography (PET) scanner. The spatial resolution of a high-resolution small animal PET scanner is significantly influenced by the effect of depth of interaction (DOI) uncertainty. The aim of this work is to investigate the impact of DOI resolution on the spatial resolution of a small animal PET scanner called SIAT aPET and determine the required DOI resolution to achieve nearly uniform spatial resolution within the field of view (FOV).Approach. The SIAT aPET detectors utilize 1.0 × 1.0 × 20 mm3crystals, with an average DOI resolution of ∼2 mm. A default number of 16 DOI bins are used during data acquisition. First, a Na-22 point source was scanned in the center of the axial FOV with different radial offsets. Then, a Derenzo phantom was scanned at radial offsets of 0 and 15 mm in the center axial FOV. The measured DOI information was rebinned to 1, 2, 4 and 8 DOI bins to mimic different DOI resolutions of the detectors during image reconstruction.Main results. Significant artifacts were observed in images obtained from both the point source and Derenzo phantom when using only one DOI bin. When accurate measurement of DOI is not achieved, degradation in spatial resolution is more pronounced in the radial direction compared to tangential and axial directions for large radial offsets. The radial spatial resolutions at a 30 mm radial offset are 5.05, 2.62, 1.24, 0.86 and 0.78 mm when using 1, 2, 4, 8, or 16 DOI bins, respectively. The axial spatial resolution improved from ∼1.3 to 0.7 mm as the number of DOI bins increased from 1 to 16 at radial offsets from 0 to 25 mm. Two DOI bins are required to obtain images without significant artifacts. The required DOI resolution is about three times the crystal width of SIAT aPET to achieve a uniform submillimeter spatial resolution within the central 60 mm FOV and resolve the 1 mm rods of the Derenzo phantom at both positions.

Evaluating effect modification by HIV testing history to understand the mechanisms behind the impact of announcing HIV self-testing availability in a clinic system in Kenya.

Background: In sub-Saharan Africa, truckers and female sex workers (FSWs) have high HIV risk and face challenges accessing HIV testing. Adding HIV self-testing (HIVST) to standard of care (SOC) programs increases testing rates. However, the underlying mechanisms are not fully understood. HIVST may decrease barriers (inconvenient clinic hours, confidentiality concerns) and thus we would expect a greater impact among those not accessing SOC testing (barriers prevented previous testing). As a new biomedical technology, HIVST may also be a cue to action (the novelty of a new product motivates people to try it), in which case we might expect the impact to be similar by testing history. Methods: We used data from two randomized controlled trials evaluating the announcement of HIVST availability via text-message to male truckers (n = 2,260) and FSWs (n = 2,196) in Kenya. Log binomial regression was used to estimate the risk ratio (RR) for testing ≤ 2 months post-announcement in the intervention vs. SOC overall and by having tested in the previous 12-months (12m-tested); and we assessed interaction between the intervention and 12m-tested. We also estimated risk differences (RD) per 100 and tested additive interaction using linear binomial regression. Results: We found no evidence that 12m-tested modified the HIVST impact. Among truckers, those in the intervention were 3.1 times more likely to test than the SOC (p < 0.001). Although testing was slightly higher among those not 12m-tested (RR = 3.5, p = 0.001 vs. RR = 2.7, p = 0.020), the interaction was not significant (p = 0.683). Among FSWs, results were similar (unstratified RR = 2.6, p < 0.001; 12m-tested: RR = 2.7, p < 0.001; not 12m-tested: RR = 2.5, p < 0.001; interaction p = 0.795). We also did not find significant interaction on the additive scale (truckers: unstratified RD = 2.8, p < 0.001; 12m-tested RD = 3.8, p = 0.037; not 12m-tested RD = 2.5, p = 0.003; interaction p = 0.496. FSWs: unstratified RD = 9.7, p < 0.001; 12m-tested RD = 10.7, p < 0.001, not 12m-tested RD = 9.1, p < 0.001; interaction p = 0.615). Conclusion: The impact of HIVST was not significantly modified by 12m-tested among truckers and FSWs on the multiplicative or additive scales. Announcing the availability of HIVST likely served primarily as a cue to action and testing clinics might maximize the HIVST benefits by holding periodic HIVST events to maintain the cue to action impact rather than making HIVST continually available.

Costing analysis of an SMS-based intervention to promote HIV self-testing amongst truckers and sex workers in Kenya.

OBJECTIVE: HIV testing rates in many sub-Saharan African countries have remained suboptimal, and there is an urgent need to explore strategic yet cost-effective approaches to increase the uptake of HIV testing, especially among high-risk populations. METHODS: A costing analysis was conducted for a randomized controlled trial (RCT) with male truckers and female sex workers (FSWs) registered in the electronic health record system (EHRS) of the North Star Alliance, which offers healthcare services at major transit hubs in Southern and East Africa. The RCT selected a sample of truckers and FSWs who were irregular HIV testers, according to the EHRS, and evaluated the effect of SMSs promoting the availability of HIV self-testing (HIVST) kits in Kenyan clinics (intervention program) versus a general SMS reminding clients to test for HIV (enhanced and standard program) on HIV testing rates. In this paper, we calculated costs from a provider perspective using a mixed-methods approach to identify, measure, and value the resources utilized within the intervention and standard programs. The results of the analysis reflect the cost per client tested. RESULTS: The cost of offering HIVST was calculated to be double that of routine facility-based testing (USD 10.13 versus USD 5.01 per client tested), primarily due to the high price of the self-test kit. In the two study arms that only offered provider-administered HIV testing in the clinic, only 1% of truckers and 6% of FSWs tested during the study period, while in the intervention arm, which also offered HST, approximately 4% of truckers and 11% of FSWs tested. These lower than expected outcomes resulted in relatively high cost per client estimates for all three study arms. Within the intervention arm, 65% of truckers and 72% of FSWs who tested chose the HIVST option. However, within the intervention arm, the cost per additional client tested was lower for FSWs than for truckers, at USD 0.15 per additional client tested versus USD 0.58 per additional client tested, driven primarily by the higher response rates. CONCLUSION: Whilst the availability of HIVST increased HIV testing among both truckers and FSWs, the cost of providing HIVST is higher than that of a routine health facility-based test, driven primarily by the price of the HIV self-test kit. Future research needs to identify strategies which increase demand for HIVST, and determine whether these strategies and the subsequent increased demand for HIVST are cost-effective in relation to the conventional facility based testing currently available.