Image Segmentation of Ziehl-Neelsen Sputum Slide Images for Tubercle Bacilli Detection

Tuberculosis (TB) remains one of the leading causes of death in developing countries and its recent resurgences in both developed and developing countries warrants global attention. Globally, there were an estimated of 9.27 million incident cases of TB in 2007. This is an increase from 9.24 million cases in 2006, 8.3 million cases in 2000 and 6.6 million cases in 1990. Most of the estimated numbers of cases in 2007 were in Asia (55%) and Africa (31%), with small proportions of cases in the Eastern Mediterranean Region (6%), the European Region (5%) and the Region of the Americas (3%). The five countries that rank first to fifth in terms of total numbers of cases in 2007 are India (2.0 million), China (1.3 million), Indonesia (0.53 million), Nigeria (0.46 million) and South Africa (0.46 million). Of the 9.27 million incident TB cases in 2007, an estimated 1.37 million (15%) were HIV-positive; 79% of these HIV-positive cases were in the African Region and 11% were in the South-East Asia Region (WHO, 2009). Ziehl-Neelsen stain method is one of the common techniques that are being used to diagnose the TB infection. Smear microscopy with Ziehl-Neelsen technique has been the main means of diagnosing TB patients in developing countries. This is because the method is simple, rapid, reproducible, low cost and effective in detecting infectious disease such as TB (Luna, 2004). TB diagnosis is usually being done manually by microbiologist through microscopic examination of sputum specimen of TB patients for pulmonary TB diseases. However, there are some problems that have been reported with manual screening process, such as time consuming and labor-intensive, especially for screening of the negative slides. (Veropoulus et al., 1998). When reporting the results of the microscopic examination, the microbiologist should provide the clinician with an estimation of the number of acid-fast bacilli detected. If the smear microscopy is clearly positive, very little observation time is needed to confirm the result. The slide is classified as TB positive if at least one tubercle bacilli is found in 300 microscopic fields. The case will then be classified into one of four severity category if the smear on the slide is found to be positive, according to the number of tubercle bacilli found in the slide. For a well-trained microbiologist, it takes 15 to 20 minutes to read and confirm one negative slide, with an average of 25 slides can be read per day. In addition, for some developing countries, there is also a lack of well-trained microbiologist,