Purpose: Motion artifacts in magnetic resonance (MR) images mostly undergo subjective evaluation, which is poorly reproducible, time consuming, and costly. Recently, full-reference image quality assessment (FR–IQA) metrics, such as structural similarity (SSIM), have been used, but they require a reference image and hence cannot be used to evaluate clinical images. We developed a convolutional neural network (CNN) model to quantify motion artifacts without using reference images.
Approach: The brain MR images were obtained from an open dataset. The motion-corrupted images were generated retrospectively, and the peak signal-to-noise ratio, cross-correlation coefficient, and SSIM were calculated. The CNN was trained using these images and their FR–IQA metrics to predict the FR–IQA metrics without reference images. Receiver operating characteristic (ROC) curves were created for binary classification, with artifact scores < 4 indicating the need for rescanning. ROC curve analysis was performed on the binary classification of the real motion images.
Results: The predicted FR–IQA metric having the highest correlation with the subjective evaluation was SSIM, which was able to classify images requiring rescanning with a sensitivity of 89.5%, specificity of 78.2%, and area under the ROC curve (AUC) of 0.930. The real motion artifacts were classified with the AUC of 0.928.
Conclusions: Our CNN model predicts FR–IQA metrics with high accuracy, which enables quantitative assessment of motion artifacts in MR images without reference images. It enables classification of images requiring rescanning with a high AUC, which can improve the workflow of MR imaging examinations.
We developed a novel system for imaging and qualitatively analyzing the surface vessels using near-infrared (NIR) radiation using tuned aperture computed tomography (TACT®). The system consisted of a NIR-sensitive CCD camera surrounded by sixty light emitting diodes (with wavelengths alternating between 700 or 810 nm). This system produced thin NIR tomograms, under 0.5 mm in slice thickness. The venous oxygenation index reflecting oxygen saturation levels calculated from NIR tomograms was more sensitive than that from the NIR images. This novel system makes it possible to noninvasively obtain NIR tomograms and accurately analyze changes in oxygen
We developed a novel system for imaging and qualitative analysis of surface vessels using near infrared (NIR) radiation with tuned aperture computed tomography (TACT®), even if the NIR cannot transmit through thick regions. NIR-sensitive CCD camera was surrounded by sixty light emitting diodes (alternating wavelengths of 700 nm and 810 nm), and could only detect the NIR from the subcutaneous tissue. We obtained multiple near infrared projections of surface vessels at each wavelength in accordance with the optical aperture theory within one second. Then, we created tomograms using the TACT program, and determined the venous oxygenation index (VOI), which reflected the oxygen saturation level, calculated from the image signals at each wavelength. This system produced thinner NIR tomograms under 0.5 mm. The change in VOI after load test calculated from NIR tomograms was more sensitive than that from NIR images without tomography. Our novel system makes it possible to non-invasively obtain NIR tomograms and accurately analyze changes in oxygen saturation.
The In-Zn oxide films with a laminated multilayer structure of each layer of In2O3 and ZnO were grown on glass substrates or polycarbonate disk substrates by pulsed laser deposition using a split target consisted of In2O3 and ZnO. For the disk sample with 60-layers, which was approximately 30 nm thick, fabricated at the trace ratio (the ratio of time required to irradiate each part of the split target) of In2O3:ZnO = 1:1, the CNR of approximately 60 dB was obtained for 3T signal (f = 58.5 MHz, λ = 406 nm, NA = 0.65).
The large transmittance change induced Zn-Ga-In oxide films grown by the sputtering method was investigated in the wavelength near 400 nm. The ability to record on the Zn-Ga-In oxide films, using THG of YAG laser ((lambda) equals 355 nm, 3 ns) was confirmed.
A great variety of reversible phase change optical recording materials have been extensively investigated. These alloy films are mainly composed of the IV-VI group (GeTe) and V group (Sb) in the periodic table. For achieving fast crystallization and stable cyclic operation, the excess Sb component of pseudo ternary alloy of GeTe-Sb2Te3-Sb has been investigated. At the melt-quenched process from the crystalline to the amorphous phase, the problem is to know if the laser pulse is essentially heating the sample which simply melts or if the electron-hole pairs created by the laser generate a new fluidlike state. The research on the electron-phonon interaction has shown that if a certain fraction of the valence-band electrons are excited into the conduction band, then the frequency of TA phonon, responsible for the stability of the crystal, goes to zero and crystal should become fluid. On the other hand, thin film surface becomes unstable before the bulk and the process of melting consists in the unstable surface at the film thickness of 10 - 50 nm. The inclusion of surface effects that self-consistently accounts for anharmonicity reduces the temperature at which an instability occurs. Both effects of electron-phonon instability and surface instability reduced the melting temperature of the phase change optical memory materials cooperatively. Therefore, the phase change optical disk is stable for the cyclic operation of 106 - 107.
In stoichiometric GeTe-Sb2Te3 films, reversible phase change optical recording materials, Sb addition is used widely to improve the data retention time and the repetition cycles, but its mechanism is not clear. To clarify the effect of excess Sb, the effects of Te and Ge addition were also investigated in the compositions from the stoichiometry Ge2Sb2Te5 toward the vertices in the Ge-Te-Sb triangle. By DSC measurements, it was found that a retention ability for amorphous (`write') states related to the increase of repetition cycles is larger in the Sb addition than in the Te and Ge addition. By XRD measurements, it was understood that an optimum ratio of (Sb,Te)(beta) /GeTe(111), about 0.5 was necessary to static repetition cycles approximately 106 in the laser annealed film of 1000 angstroms thick.
In stoichiometric GeTe-Sb2Te3 films, reversible phase change optical recording materials, Sb addition is used widely in order to improve the crystallization speed, the data retention time, and the stability of cyclic operation, but its mechanism is not clear. V-VI compounds (GeTe, SnTe) are well known as compounds in which the ferroelectric structural phase transition occurs. The dielectric constant (epsilon) 0 changes largely due to a change in the short-range order of weakly bound nearest neighbors in the crystal to more strongly bound nearest neighbors in the amorphous phase. Therefore, it is necessary to discuss the effect of Sb addition in the stoichiometric GeTe-Sb2Te3 composition upon the dynamic properties of crystallization and the dielectric constant change (Delta) (epsilon) 0 based on the ferroelectric phase transition.
Crystallization velocities and activation energies in the initial crystalli- zation process, obtained from measurements transmissivity(reflectivity), are de- scribed for amorphous In-Sb-Te films 400-600 A thick, which are set up in a chamber with a window guiding of the light through a long-distance focused lens. The crystallization velocity was obtained to about 100 Ajs for Inx(Sb0.4Teo.6)1-. x=0.2--0.3) films. The activation energy was determined by Kissinger's plot to be 1.5--2.0 eV. The frequency factor was calculated by the Johnson-Mehl-Avrami equation; logi 0 v 0=20-30 (Hz). Static repetition cycles of about 3 X 104 were recognized in the film composition of x = 0.2 for the sample structure without upper protection layer.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.