嚥下造影検査における患者被曝線量の低減と画像の計測精度向上に関する研究

抄録

Purposes: To reduce patient dose without deterioration of image quality and to improve measurement accuracy in radiographic swallowing studies.
Materials and methods: In our hospital, swallowing studies are carried out using cine film with simultaneous digital image (CFSD) mode using a digital subtraction angiography system. The resultant image must be processed by an image intensifier because the detector has an inherent distortion problem.
(1) Exposure parameters were determined based on data obtained by CFSD mode imaging. The patient dose was measured using Rando-phantom and thermoluminescent dosimeter.
(2) A cine film image obtained by CFSD mode was compared with digital cine (DC) mode under routine exposure conditions for sharpness, incident patient dose and image contrast.
(3) As a phantom, lead circular grains of 1mm diameter were placed at the intersections of a 40mm grid. After radiographing this phantom, the distances for 32 positions was measured. The image distortion correction software was developed from commercially available software.
Results: (1) The total absorbed dose in CFSD mode was 2 to 6 times higher than that of videofluorography for each examined region.
(2) Though the sharpness of the DC image was slightly inferior to the cine film image, patient dose could be reduced to 45% by additional filter and exposure parameters.
(3) The mean length in the images without correction was 94.1±3.7 (87.0∼102.8) pixels, and 99.0±1.5 (94.5∼102.5) pixels in the corrected images. The effect of the correction was satisfactory.
Conclusion: This DC system may replace the cine film system because the patient dose can be decreased while maintaining the image quality. Additionally, the use of cine film costs more and the system occupies more physical space. In summary, patient dose reduction and improved measurement precision with lower cost suggest that shifting from a cine film system to the DC system would be advantageous.