Limitations of a single X-ray picture for locating and interpreting shadows in the chest had been studied earlier. In order to reduce these limitations, it was suggested that two pictures of each person be taken where the second picture was to be taken after a vertical displacement of X-ray tube, up or down by about 4 to 5cms. The advantages of taking two pictures simultaneously as compared to a single picture have not been studied so far. Two mobile X-ray units each with an odelca camera were alternated for the single and double picture examinations. A total of about 2,000 persons were X-rayed and were read independently by 3 readers. A spot sample of sputum was collected 3-4 days later from persons with abnormal X-ray shadows and was examined by direct smear microscopy.

Comparison of the readings of the two sets of pictures did not show a better agreement between different (inter- individual) readers or between two different readings of the same reader (intra-individual) when the two picture technique was used. The X-ray cases detected by double picture only by any one reader were not confirmed, more often than those detected by single picture only. The X-ray pictures of the bacillary cases were also not interpreted more often as active tuberculosis by the two picture technique. It was concluded that the double picture technique does not offer any advantage over the single picture technique.

This paper discusses briefly the scope for handling the roll film cassettes, its maintenance and repair, under the National Tuberculosis Programme (NTP). The District Tuberculosis Centre (DTC) use the roll film cassettes (RFC) which are hand operated. There are three models: RFC-1, RFC-2 and RFC-3. The roll film cassette is meant to accommodate 70mm and 3mts length of oneside coated film which is meant to take 40 exposures. One can take 45-50 exposures by using the leader and trailer portion of the film. Two types of films are used:one is acetate base and the other polyester base. RFC-1 is an old model and is not used now. RFC-3 is an improvised version of RFC-2 where the film is pressed more firmly so that blurred images do not form. It also has a microswitch to notify the operator about the presence or absence of film in the cassette. RFC is divided into three parts 1) film magazine 2) cassette frame and 3) housing. RFC is a costly equipment and should be maintained with care: free from dust, dirt, chemicals etc,. After prolonged use, (ie) 8-10 years, parts can wear out. At that time, it would be useful to contact NTI regarding servicing, replacement of wornout parts and repairs.

Since many moving parts are accommodated in a small space, removal, replacement and servicing of the RFC is a highly skilled work. It requires special talent, a mechanical eye and a knack to use tools.