Fundamental Study of Improvement of Contrast Using Histogram Transformation for Low Density DSA Images

Digital subtraction angiography (DSA) is a method for increasing a contrast of blood vessels by injecting a contrast medium into the blood vessels. Iodine contrast media are widely used for the DSA study, but might cause a sever side effect for the patients having iodine contraindication disease. In the previous report, we introduced gadolinium contrast medium into the DSA study. Although the contrast of the images with gadolinium contrast medium was slightly decreased compared to that with iodine contrast medium, the image quality was well acceptable for diagnostic procedures without causing any side effect. However, there is a limitation for dosage in the gadolinium contrast medium due to the long biological half-life. Lower concentration of the contrast media decreases the image contrast. In this report, we proposed a novel image processing algorithm to improve the image quality of DSA adjusting to low concentration of contrast media. The image processing algorithm consisted of smoothing, thresholding, and histogram transformation, and signal-to-noise ratio (SNR) was further improved utilizing median filtering process: In conclusion, our novel method using low concentration of gadolinium contrast medium in the DSA study showed enough image quality and may be useful for diagnosis process.