 Introduction/Background Pulmonary tuberculosis (TB) predominantly results from the transmission of aerosolized mycobacterium TB to susceptible hosts [1]. In the vast majority of cases, this results in subclinical disease with the immune system isolating the organism. In this setting, a person has latent TB and does not pose a risk to the community at large. The development of active infection within 1 year following exposure is termed primary TB and is classically described as a lobar pneumonia and/or mediastinal and hilar adenopathy. This pattern is most often seen in children and severely immunocompromised individuals. If active infection develops later than 1 year after initial exposure, it is considered to be reactivation TB, often presenting with apical posterior upper-lobe or superior- segment lower-lobe fibrocavitary disease and endobronchial spread through the airways. With modern molecular techniques it has been shown that radiographic patterns of primary and reactivation TB overlap, and thus the preferred terminology for TB infection is active TB [2]. The important public health issue is that both primary and reactivation TB present a risk of exposing the general population to TB infection. A high level of suspicion should be maintained in immunocompromised hosts, particularly those with AIDS, as imaging manifestations may not fit a classic primary or reactivation pattern; instead, these patients may present with mediastinal lymphadenopathy alone or a deceptively normal chest radiograph. Overview of Imaging Modalities Chest radiograph The chest radiograph is usually the first study performed in patients suspected of having TB. Although frontal and lateral radiographs are often performed in this setting, it has been shown that the lateral radiograph does not improve the detection of findings related to TB [3].
Imaging of Possible Tuberculosis.  Introduction/Background Pulmonary tuberculosis (TB) predominantly results from the transmission of aerosolized mycobacterium TB to susceptible hosts [1]. In the vast majority of cases, this results in subclinical disease with the immune system isolating the organism. In this setting, a person has latent TB and does not pose a risk to the community at large. The development of active infection within 1 year following exposure is termed primary TB and is classically described as a lobar pneumonia and/or mediastinal and hilar adenopathy. This pattern is most often seen in children and severely immunocompromised individuals. If active infection develops later than 1 year after initial exposure, it is considered to be reactivation TB, often presenting with apical posterior upper-lobe or superior- segment lower-lobe fibrocavitary disease and endobronchial spread through the airways. With modern molecular techniques it has been shown that radiographic patterns of primary and reactivation TB overlap, and thus the preferred terminology for TB infection is active TB [2]. The important public health issue is that both primary and reactivation TB present a risk of exposing the general population to TB infection. A high level of suspicion should be maintained in immunocompromised hosts, particularly those with AIDS, as imaging manifestations may not fit a classic primary or reactivation pattern; instead, these patients may present with mediastinal lymphadenopathy alone or a deceptively normal chest radiograph. Overview of Imaging Modalities Chest radiograph The chest radiograph is usually the first study performed in patients suspected of having TB. Although frontal and lateral radiographs are often performed in this setting, it has been shown that the lateral radiograph does not improve the detection of findings related to TB [3].