Measurement of X-ray image intensifier sharpness in the X-ray department

• Published in: Physics in medicine & biology 1988-01, Vol.33 (1), p.93-104
• Main Authors: Heron, J C Le, Poletti, J L
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Evaluation Studies as Topic; Hospital Departments; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; New Zealand; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Radiographic Image Enhancement - instrumentation; Radiology Department, Hospital; X-Ray Intensifying Screens
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/0031-9155/33/1/009

A method is presented for determining the modulation transfer function (MTF) of an image intensifier as it is found in the x-ray department. The image of an edge input into the image intensifier tube is photographed at the television camera port with a high quality camera and the photographic image scanned with a microdensitometer. Densitometric conversion enables the determination of the edge spread function and further calculation produces the line spread function and the MTF. A correction is made for the camera/lens/film/developer response function. Results from the use of the technique on over 25 x-ray image intensifiers in New Zealand hospital x-ray departments are presented and discussed. Most of the image intensifiers had been in use for more than 7 years. The low-frequency drop values were similar to reported values with an average value of 22%, but modulation values at 1 cycle/mm (the average value was 29%) were generally lower than values previously reported, indicating that the sharpness performance in the clinical environment is inferior to claims for new or state-of-the-art intensifiers.