Most of the clinical image data were contained in digital imaging and communications in medicine (DICOM) format. In 1982, the American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA) formed a committee to develop DICOM standards for the interconnection of digital imaging devices [9]. The DICOM files contain information regarding the imaging scanners such as manufacturer name, scanner model name, modality type, and acquisition parameters in the DICOM TAG field. The quality control team checks the imaging parameters and, if not consistent with site notification, then contacts the Clinical Research Coordinator (CRC), technologist and site principal investigator, to notify them of imaging failure and ask for a repeat scan as soon as possible. Table 15.1 shows an example of DICOM TAG for checking the imaging parameters. For some parameters such as repetition time, echo time, field strength, and others, checks in rounded values are permitted. Especially, when the machine manufacturer or model is changed, the reproducibility of the imaging analysis is extremely degraded, and so the quality control team must check the machine change.

Numerous artifacts in MR images that are not present in the original imaged object may be caused by improper technical operation of the imaging, while at other times they may be a consequence of natural processes or properties of the human body. Subject motion during the scan generates artifacts by inducing phase errors in the MRI signal. These artifacts can be classified into two types, blurring and ghosting artifacts. Blurring artifacts are produced by random movements, mainly in the phase-encode direction. Periodic motion associated with the movement of the lower jaw, eye, and the nasal cavity creates ghosting artifacts. Flow artifacts are caused by blood flow or fluids in the body. Fourier transform from a finite sampled signal causes truncation or gibbs artifacts as parallel lines adjacent to high-contrast borderline. Magnetic susceptibility within the internal magnetization of a tissue also causes artifacts due to interactions with an external magnetic field. Two different magnetic susceptibilities between air and tissues and/or metal and tissues cause local distortions in the magnetic field. Especially metal objects in the subject cause large distortions and significant susceptibility artifacts which result in a loss of signal in the image (metal artifacts). In normal MRI scanning, warp-around (aliasing) artifact occurs when FOV is smaller than an imaging object. The quality control team checks each MR image, and if any image does not have good quality, the quality control team recommends re-scanning. However, if the image quality will not be improved if the scan imaging is repeated, the protocol deviation must be logged or the image data have to be excluded. Checking items will be mentioned below.