1. Field of the Invention
The present invention relates to an endoscope system capable of extracting blood vessels, such as superficial blood vessels and medium-deep blood vessels, in a subject, a processor device of an endoscope system, and an image processing method.
2. Description of the Related Art
In recent medical treatment, diagnosis or the like using an endoscope apparatus has been widely performed. As observation of the inside of a subject using an endoscope apparatus, not only normal observation using white light of broadband light as illumination light but also blood vessel enhancement observation, in which blood vessels in a subject are highlighted using narrowband light having a narrowband wavelength, has been performed.
In this blood vessel enhancement observation, determination regarding whether or not cancer is present from the shape of a blood vessel is performed. Types of blood vessels mainly include superficial blood vessels distributed on a living tissue surface and medium-deep blood vessels located below the superficial blood vessels. Depending on the purpose of diagnosis, diagnosis may be performed focusing on certain blood vessels. In this case, if blood vessels that are not the focus of observation are added in an endoscope image, there may be an interruption to diagnosis. For this reason, differentiating superficial blood vessels or medium-deep blood vessels from the image and displaying an image, which is obtained by extracting only blood vessels to be observed, on a monitor has been demanded.
Regarding the method of determining the depth of a blood vessel, JP2011-135983A discloses a method of performing determination of a superficial blood vessel when the hue of a narrowband image generated based on narrowband light in a specified wavelength region (415 nm, 540 nm) is 5 to 35 and performing determination as a medium-deep blood vessel when the hue is 170 to 200.