A number of digital imaging techniques in medicine require the combination of multiple images. Using these techniques, it is essential that the images be adequately aligned and registered prior to addition, subtraction, or any other combination of the images. This paper describes an alignment routine developed to register an image of a fixed object containing a global offset error, rotation error, and magnification error relative to a second image. The described routine uses sparsely sampled regional correlation in a novel way to reduce computation time and avoid the use of markers and human interaction. The result is a fast, robust, and automatic alignment algorithm, with accuracy better than about 0.2 pixel in a test with clinical computed radiography images.
The current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has created a significant threat to global health. While respiratory aerosols or droplets are considered as the main route of human-to-human transmission, secretions expelled by infected individuals can also contaminate surfaces and objects, potentially creating the risk of fomite-based transmission. Consequently, frequently touched objects such as paper currency and coins have been suspected as potential transmission vehicle. To assess the risk of SARS-CoV-2 transmission by banknotes and coins, we examined the stability of SARS-CoV-2 and bovine coronavirus (BCoV), as surrogate with lower biosafety restrictions, on these different means of payment and developed a touch transfer method to examine transfer efficiency from contaminated surfaces to fingertips. Although we observed prolonged virus stability, our results indicate that transmission of SARS-CoV-2 via contaminated coins and banknotes is unlikely and requires high viral loads and a timely order of specific events.
We have reported on a single-exposure dual-energy system based on computed radiography (CR) technology. In a clinical study conducted over a two year period, the dual-energy system proved to be highly successful in improving the detection (p=0.0005) and characterization (p=0.005) of pulmonary nodules when compared to conventional screen-film radiography. The basic components of our dual-energy detector system include source filtration with gadolinium to produce a bi-modal x-ray spectrum and a cassette containing four CR imaging plates. The front and back plates record the low-energy and high-energy images, respectively, and the middle two plates serve as an intermediate filter. Since our initial report, a number of improvements have been made to make the system more practical. An automatic registration algorithm based on image features has been developed to align the front and back image plates. There have been two improvements in scatter correction: a simple correction is now made to account for scatter within the multiplate detector; and a correction algorithm is applied to account for scatter variations between patients. An improved basis material decomposition (BMD) algorithm has been developed to facilitate automatic operation of the algorithm. Finally, two new noise suppression techniques are under investigation: one adjusts the noise filtering parameters depending on the strength of edge signals in the detected image in order to greatly reduce quantum mottle while minimizing the introduction of artifacts; a second routine uses knowledge of the region of valid low-energy and highenergy image data to suppress noise with minimal introduction of artifacts. This paper is a synthesis of recent work aimed at improving the performance of dual-energy CR conducted at three institutions:
BackgroundThe COVID 19 pandemic has triggered concerns and assumptions globally about transmission of the SARS-CoV-2 virus via cash transactions.ObjectivesAssess the risk of contracting COVID-19 through exposure to SARS-CoV-2 via cash acting as a fomite in payment transactions.MethodsA quantitative microbial risk assessment was conducted for a worst-case scenario assuming an infectious person at the onset of symptoms, when virion concentrations in coughed droplets are at their highest. This person then contaminates a banknote by coughing on it and immediately hands it over to another person, who might then be infected by transferring the virions with a finger from the contaminated banknote to a facial mucous membrane. The scenario considered transfer efficiency of virions on the banknote to fingertips when droplets were still wet and after having dried up and subsequently being touched by finger printing or rubbing the object.ResultsAccounting for the likelihood of the worst-case scenario to occur by considering 1) a local prevalence of 100 COVID-19 cases/100,000 persons, 2) a maximum of about 1/5th of infected persons transmit high virus loads and 3) the numbers of cash transactions/person/day, the risk of contracting COVID-19 via person-to-person cash transactions was estimated to be much lower than once per 39,000 days (107 years) for a single person. In the general populace, there will be a maximum of 2.6 expected cases/100,000 persons/day. The risk for a cashier at an average point of sale was estimated to be much less than once per 430 working days (21 months).DiscussionThe worst-case scenario is a rare event, therefore, for a single person, the risk of contracting COVID-19 via person-to-person cash transactions is very low. At a point of sale, the risk to the cashier proportionally increases but it is still low.
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