1. Field of the Invention
The present invention relates to a medical image processing apparatus and a medical image diagnosis apparatus, and specifically relates to a technology of displaying by synthesizing a morphological image and a functional image of an object.
2. Description of the Related Art
In recent years, the propagation of medical image diagnosis apparatuses for acquiring images representing the morphology or the function of an object has been promoted. Medical image diagnosis apparatuses include the X-ray diagnosis apparatus, X-ray CT (Computed Tomography) apparatus, MRI (Magnetic Resonance Imaging) apparatus, ultrasound diagnosis apparatus, and nuclear medical diagnosis apparatus.
Ischemic heart disease is one of diseases in which the effectiveness of a medical image diagnosis apparatus is demonstrated. Ischemic heart disease is a disease in which constriction is caused in a coronary artery due to the effects of arteriosclerosis, thrombus, etc., resulting in a lack of oxygen supply or nutrients supply to the cardiac muscle.
A method of measuring the constriction rate of blood vessels by referring to images (morphological images) representing the morphology of the heart of an object has been widely used for the conventional diagnosis or treatment of ischemic heart disease. However, it is known that the correlation between blood vessels having developed arteriosclerosis or the like (culprit coronary artery) and the constriction rate is, in general, not particularly high. Therefore, it is not easy to diagnose or treat with high accuracy by referring to only the constriction rate.
Further, it is also possible to think of making a diagnosis by referring to images representing the function of the heart of an object (functional images). However, it is not possible to accurately specify the position of a culprit coronary artery from only functional images. Therefore, diagnosis and treatment with accuracy is difficult.
In view of such a situation, a technology of displaying by synthesizing a morphological image and a functional image has been developed. Such an image acquired by synthesizing a plurality of images (may be morphological images only or functional images only) is referred to as a fusion image or the like.
Technologies that make it possible to display a fusion image have been disclosed in Japanese Unexamined Patent Application Publication JP-A 10-127623 and Japanese Unexamined Patent Application Publication JP-A 2003-153877. The technology described in JP-A 10-127623 is to display by creating a fusion image obtained by synthesizing a tomographic image acquired by an X-ray CT apparatus and a bloodstream distribution image acquired by an ultrasound diagnosis apparatus. The technology described in JP-A 2003-153877 is to display by creating a fusion image obtained by synthesizing a morphological image acquired by an MRI apparatus and a bloodstream distribution image acquired by an ultrasound diagnosis apparatus.
However, in the conventional techniques mentioned above, it is difficult to diagnose or treat with favorable accuracy for the following reasons.
First, in the case of referring to only morphological images or only functional images, there is a problem of the accuracy of the diagnosis as mentioned above. In particular, in the case of referring to morphological images, there is a risk of overlooking constricted sites in the images.
Furthermore, as another method, it is known to obtain the difference between a normal morphological image and a morphological image (contrast enhanced image) taken by administering a contrast agent to extract an image of a blood vessel and display (referred to as, e.g., digital subtraction angiography). However, this method is generally regarded as improper to examinations of a heart, which has an intricate blood vessel system.
Moreover, in the case of referring to a fusion image stated in JP-A 10-127623 and in JP-A 2003-153877, only bloodstream distribution images can be acquired as functional images, so it is difficult to accurately specify the position of a culprit coronary artery, and thus, it is difficult to diagnose or treat with accuracy.
In addition, in conventional techniques, it is necessary to perform an examination for specifying the position of a culprit coronary artery and a treatment based on the result thereof. However, it is necessary to execute a catheter examination in both the processes, and there is a problem of significant stress being imposed on an object. Furthermore, there is also a problem in that the object is subjected to radiation poisoning in both the processes. Moreover, there is also a problem of having a long interval between the examination and the treatment (e.g., approx. two weeks).