방사선 투시검사에서 Screen Capture 영상의 유용성

Abstract

The image gets through 'spot radiography' in the conventional radio fluoroscopy which has evolved into a digital radio fluoroscopy with an additional function 'screen capture'. This study aims to test clinical diagnostic utilities of screen capture by contrasting screen capture and spot radiography in the quality of their images and x-ray exposures used for the images. Comparison between screen capture and spot radiography was performed both in quality of images and exposure conditions of x-ray used for making images. The quality of images was tested in terms of image parameters, 'contrast' and spatial 'resolution' using images on phantoms. The phantom images were obtained using Radiological fluoroscopy system (Winscope, Toshiba, Japan) for both the contrast phantom (Al_stepwedge, department of radiology, Jeju National University Hospital, Korea) and the resolution phantom (Nuclear associates-Carie, place-N.Y 07-523, SUPERTECHⓡ, USA). The phantoms were located in the water cell and for consideration of the 3 typical classes of patient in size, the height of water was set to the 3 different levels, ie, 12cm for 'skinny', 18cm for 'normal', and 24cm for 'fat'. The image contrast (CR = 1.5~3.5) remained almost the same regardless of the water height, but was different with the water height in screen capture. The contrast in screen capture phantom images varied ranges of 2~4.5 in the water height of 12cm, 2~3.5 in 18cm and 1.5~2 in 24cm. So, it has a broad range in 12cm more than spot radiography, and is similar in 18cm, but decreased suddenly in 24cm. Resolution was 2.0 lp/mm in 12cm 1.8 lp/mm in 18cm and 24cm on spot radiography while it appears 1.8 lp/mm in 12cm, 1.6 lp/mm in 18 and 24cm in screen capture. This indicates that the resolution in general decreases with the height of water and is slightly higher (by about 10%) in spot radiography than screen capture. The x-ray energy used for contrast phantom images was 261 J, 392 J, 1,726 J for the water height 12, 18 and 24cm, respectively on spot radiography and was 7.2 J, 13 J, 17 J on screen capture. The x-ray energy used for resolution phantom images was 12.3 J, 321 J, 511 J for the water height 12, 18 and 24cm, respectively on spot radiography and was 79 J, 13 J, 17 J on screen capture. The phantom studies show that the contrast was similar between screen capture and spot radiography for skinny and normal class. Resolution measured decreased with the size of patients and was found to be higher 10% in spot radiography than screen capture over all three classes. But the x-ray energy required for images in screen capture was not more than 4 % than spot radiography. The results indicate screen capture uses a small dose of x-ray without deteriorating in quality of images, in particular, for skinny or normal body size. It is expected that the function of screen capture in digital radio fluoroscopy, minimizing the quantity of x-ray exposure but keeping similar quality of images as pot radiography, will be of use for clinical diagnosis in particular pediatric radiography.