## 1 Introduction  
Infectious diseases are major threats to global health, and TB is the world's top infectious killer and also the major cause of death among people with HIV/AIDS. It is caused by the Mycobacterium tuberculosis bacterium that attacks the lungs. TB spreads when a person, with active TB, coughs, sneezes, or otherwise expels the bacteria. In its 2019 TB report, the WHO estimated that 10 million people were ill with TB (5.7 million males, 3.2 million females, and 1.1 million children) in 2018. Even though it is preventable and curable, it claimed 1.5 million deaths in 2018 [1] and kills over 4000 people each day. TBoccurs all over the world, whereas over 95% of cases and deaths are in middle- and low-income countries. The WHO reported that geographically high TB burden countries are in the Southeast Asian region, with 44% of new cases, followed by the African region, with 24% of new cases, and the Western Pacific with 18%, in 2018. People with HIV have a 15-22% higher risk of contracting tuberculosis than those without HIV. Undernourished people are also at high risk because their immune systems are impaired. Thus, developing countries, with widespread poverty and undernutrition, are the most TB-prevalent regions. A rising number of multi-drug-resistant bacteria has exacerbated the TB burden. Thus, TB remains a key factor in public health and a health security threat [1]. Despite increases in notifications, there are still many undiagnosed cases because people with TB are not being checked. Early diagnosis and prompt treatment are crucial to reducing TB-related deaths and curtailing their onward transmission, allowing us to end TB epidemics. With rapid molecular analysis and bacteria culture methods, TB detection is now very accurate [2]. However, their limited availability and expense restrict widespread use in under-resourced countries with a high TB burden. Because they are not expensive and easily accessed, chest X-rays are mandatory for every evaluation of TB and become a critical screening, diagnostic, and triaging tool for TB and other lung diseases, including lung cancer, pneumonia, etc. A chest X-ray covers all thorax anatomical structures and is a high-yield test at a low cost from a single source. Common manifestations of TB, in X-ray images, are infiltrations, cavitations, consolidations, pleural effusion and thickening, opacities, military pattern, and nodules. Some typical TB lesions are shown in Figure 1. More examples of TB manifestations can be found in [PERSON] et al. 's primer [3]. Diagnosis of TB in X-rays is still limited in under-resourced countries where sufficient trained experts to interpret every radiograph are not available. Moreover, TB manifestations are complex and diverse, so manual detection is difficult, even for radiologists. Further, TB lesions that overlap with other disease lesions can imitate many other lung diseases. These discrepancies cause significant observer variation in TB detection. Fortunately, with the advent of digital X-rays and advanced computer vision techniques, computer-aided diagnosis has become an alternative to the expert reading of radiographs. It is hoped that an inexpensive and accurate TB detection algorithm can make the widespread screening  
Figure 1: Samples of TB manifestations in X-ray images: (**a**) large infiltrate in RUL with cavitation and infiltrate in RML, (**b**) large right pleural effusion, (**c**) extensive infiltrates bilaterally with a large cavity in RUL and a moderate pleural effusion on the left, (**d**) TB scars, (**e**) cavitary disease RUL with possible small lobulated pneumothorax adjacent, with multiple coarse nodules in RLL as well as lesser amounts in LLL, and (**f**) cavitary infiltrate near left him consistent with TB in superior segment LLL. Key: RUL—right upper lung, RML—right middle lung, RLL—right lower lung, and LLL—left lower lung. of TB a reality in large populations with limited medical resources and alleviate human observer errors.