2l世纪医学影像学的发展（The development of medical imaging in the 2l century）.doc

2l世纪医学影像学的发展（The development of medical imaging in the 2l century） The development of medical imaging in the 2l century Pang Shizhen Medical image features Different medical imaging methods can reveal different imaging features of patients, and these features are described as follows: Characteristics, influencing factors, sources Transmittance is due to block density X - ray Dark electron density Y ray Emissivity; proton density; visible light Reflective atomic number ultraviolet Conductivity infrared ray Magnetic drug delivery position magnetic field Current electric field Molecular release ultrasound Applied voltage These characteristics include patient transmittance, opacity, emissivity, reflectance, conductivity, magnetism, molecular release constants, and their changes over time. Descriptions of these features can reveal potential features of the patient. For example, projective radiography and X - ray computed tomography (CT) are also affected by certain intrinsic characteristics of the patient tissue, such as average atom number, physical density, and electron density. Nuclear imaging techniques, including emission computed tomography (ECT), positive emission tomography (PET) and single photon emission computed tomography (SPECT), can reveal temporal and spatial distribution of drugs in vivo. Accordingly, the digital signals can be converted into the characteristics of glucose metabolism, blood volume and blood flow, tissue occupancy, receptor binding and oxygen utilization. Ultrasound images can describe the boundary characteristics between different acoustic impedance tissues. Acoustic impedance = (tissue density) * (the speed at which sound waves pass through the tissue). Magnetic resonance imaging (MRl) of molecular release features converts the density, mobility, and chemical association of hydrogen with other elements into a digital signal. The characteristics of these images reflected by medical images vary in time and space with the change of the stru