Determination of radiographic characteristics of tissue compensation filters using a compton scatter technique

Tissue compensation filters (TCF) aid in plain film radiographic examinations by reducing the range of radiographic densities in the film. The composition and shape of the TCF assists in reducing radiographic density ranges that result from large anatomical density differences within the patient. The reduction of large density ranges on a radiographic film allows the clinicians to visualise larger ranges of anatomy. A Compton scatter technique has been used to examine the changes in the x-ray spectra that result from the placement of various TCF materials and thicknesses in the primary x-ray beam. Difficulties in the use of the Compton scatter technique in the examination of TCF under clinical conditions are discussed. Conclusions have been reached that will enable clinicians to optimising the x-ray tube voltage (kVp) so to maximise the effectiveness of each TCF material examined. The term spectral shift has been defined to aid in the evaluation of the TCF's effect on x-ray spectral changes. Maximum spectral shift for each type of TCF material occurs between generator settings of 70 - 80 kVp. TCF spectral shift changes were also examined under typical clinical generator types. Maximum spectral shift occurs when TCF are used with single phase, 100% ripple generators. Dose reduction conclusions from the use of the TCF are also discussed.