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Comparison of treatment plans for a?high-field MRI-linac and a?conventional linac for esophageal cancer; Vergleich der Behandlungspl?ne von einem Hochfeld-MRT-Linac und einem konventionellen Linac beim ?sophaguskarzinom;
摘要： Purpose To compare radiotherapy treatments plans in esophageal cancer calculated for a high-?eld magnetic resonance imaging (MRI)-linac with plans for a conventional linac. Materials and methods Ten patients with esophageal squamous cell carcinomas were re-planned retrospectively using the research version of Monaco (V 5.19.03, Elekta AB, Stockholm, Sweden). Intensity modulated radiotherapy (IMRT) plans with a nine-?eld step-and-shoot technique and two-arc volumetric modulated arc therapy (VMAT) plans were created for the Elekta MRI-linac and a conventional linac, respectively. The prescribed dose was 60 Gy to the primary tumor (PTV60) and 50 Gy to elective volumes (PTV50). Plans were optimized for optimal coverage of the 60 Gy volume and compared using dose–volume histogram parameters. Results All calculated treatment plans met prede?ned criteria for target volume coverage and organs at risk dose both for MRI-linac and conventional linac. Plans for the MRI-linac had a lower number of segments and monitor units. No signi?cant differences between both plans were seen in terms of V20Gy of the lungs and V40Gy of the heart with slightly higher mean doses to the heart (14.0 Gy vs. 12.5 Gy) and lungs (12.8 Gy vs. 12.2 Gy). Conclusion Applying conventional target volume and margin concepts as well as dose-fractionation prescription re- veals clinically acceptable dose distributions using hybrid MRI-linac in its current con?guration compared to standard IMRT/VMAT. This represents an important prerequisite for future studies to investigate the clinical bene?t of MRI-guided radiotherapy exploiting the conceptional advantages such as reduced margins, plan adaptation and biological individual- ization and hypofractionation.
关键词： Intensity-modulated radiotherapy,Volumetric modulated arc therapy,Organs at risk,Squamous cell carcinomas,Magnetic resonance imaging
更新于2025-09-10 09:29:36
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[Ocular Trauma] Anatomy and Examination in Ocular Trauma || Imaging Examination
摘要： Technology advances at a great pace. Particularly in medicine and, one may venture to say, even more so in the field of ophthalmology. Yet, regarding ocular trauma, the physician stands between multiple crossroads when deciding which imaging examination method to choose from. He must find balance between cost-benefit, medicolegal purposes, immediate or intermediate availability, and prioritizing strategy-modifying information, more often than not relying on century-old techniques, mixed with state-of-the-art technologies, and always based on solid clinical evaluation to make the best decision in a reasonably short time. This chapter will attempt to introduce the imaging examination techniques of X-ray, computed tomography scan, magnetic resonance imaging, B-ultrasound, biomicroscopy, optical coherence tomography, and specular microscopy now available for the assessment in ocular trauma, their working mechanisms, scopes, as well as their strong and weak points.
关键词： Computed tomography scan,Ocular trauma,Magnetic resonance imaging,B-ultrasound,Optical coherence tomography,Specular microscopy,Examination,X-ray,Biomicroscopy,UBM
更新于2025-09-10 09:29:36
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Posterior Eye Shape Measurement With Retinal OCT Compared to MRI
摘要： PURPOSE. Posterior eye shape assessment by magnetic resonance imaging (MRI) is used to study myopia. We tested the hypothesis that optical coherence tomography (OCT), as an alternative, could measure posterior eye shape similarly to MRI. METHODS. Macular spectral-domain OCT and brain MRI images previously acquired as part of the Singapore Epidemiology of Eye Diseases study were analyzed. The right eye in the MRI and OCT images was automatically segmented. Optical coherence tomography segmentations were corrected for optical and display distortions requiring biometry data. The segmentations were ?tted to spheres and ellipsoids to obtain the posterior eye radius of curvature (Rc) and asphericity (Qxz). The differences in Rc and Qxz measured by MRI and OCT were tested using paired t-tests. Categorical assignments of prolateness or oblateness using Qxz were compared. RESULTS. Fifty-two subjects (67.8 6 5.6 years old) with spherical equivalent refraction from t0.50 to (cid:2)5.38 were included. The mean paired difference between MRI and original OCT posterior eye Rc was 24.03 6 46.49 mm (P ? 0.0005). For corrected OCT images, the difference in Rc decreased to (cid:2)0.23 6 2.47 mm (P ? 0.51). The difference between MRI and OCT asphericity, Qxz, was (cid:2)0.052 6 0.343 (P ? 0.28). However, categorical agreement was only moderate (j ? 0.50). CONCLUSIONS. Distortion-corrected OCT measurements of Rc and Qxz were not statistically signi?cantly different from MRI, although the moderate categorical agreement suggests that individual differences remained. This study provides evidence that with distortion correction, noninvasive of?ce-based OCT could potentially be used instead of MRI for the study of posterior eye shape.
关键词： asphericity,optical coherence tomography,magnetic resonance imaging,myopia
更新于2025-09-10 09:29:36
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PACS-Based Multimedia Imaging Informatics (Basic Principles and Applications) || Digital Medical Imaging
摘要： The chapter discusses the fundamentals of digital medical imaging, including two-dimensional (2-D) and three-dimensional (3-D) imaging techniques, image compression, and the integration of imaging informatics with patient imaging workflows. It covers various imaging modalities such as computed radiography (CR), digital mammography, nuclear medicine imaging, ultrasound imaging, and magnetic resonance imaging (MRI), highlighting their principles, applications, and the challenges in archiving and transmitting large datasets.
关键词： digital medical imaging,computed radiography,ultrasound imaging,digital mammography,PACS,2-D imaging,image compression,3-D imaging,nuclear medicine imaging,magnetic resonance imaging
更新于2025-09-10 09:29:36
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Disturbed interhemispheric functional connectivity in visual pathway in individuals with unilateral retinal detachment: A resting state fMRI study
摘要： Previous neuroimaging studies demonstrated that retinal detachment (RD) subjects were associated with abnormal spontaneous brain activities; however, whether the altered interhemispheric functional connectivity (FC) occurred in RD patients remains unknown. The current study tried to explore the alternations of interhemispheric FC of the whole brain in unilateral RD patients using the voxel-mirrored homotopic connectivity (VMHC) method and their connections to clinical features. Methods: We recruited 30 patients with RD (16 males and 14 females) and 30 healthy controls (HCs) (16 males and 14 females) whose age and sex were closely matched. All subjects underwent the rs-fMRI scans. The VMHC method was applied to directly assess the hemispheres’ functional interaction. The VMHC in these brain areas, which could be used as biomarkers to differentiate RD from HC, was identified by the receiver operating characteristic (ROC) curve analyses. The relations between these patients’ clinical features and their mean VMHC signal values in multiple brain regions were calculated by Pearson correlation analysis. Results: RD patients had significantly lower VMHC values than HCs in the bilateral occipital lobe (Brodmann areas, BA 18), bilateral superior temporal gyrus (BA 39), and bilateral cuneus (BA 19). Moreover, the mean VMHC signal values of the bilateral cuneus were in positive correlation with the duration of the RD (r = 0.446, P = 0.013). Conclusion: Our results provided an evidence of disturbed interhemispheric FC in the visual area occurred in RD patients, which might provide some useful information to understand the neural mechanism of RD patients with acute vision loss. Furthermore, the VMHC values might indicate the progress of the RD.
关键词： Retinal detachment,Functional magnetic resonance imaging,Static condition,Voxel-mirrored homotopic connectivity
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Tunability methods for magnetic resonance imaging applications of metasurfaces
摘要： In this work, we propose and discuss methods of tuning eigenmode resonance frequencies of wire metasurfaces. Fine tuning of metasurface properties is essential for maximizing its coupling with transmitting and receiving radiofrequency (RF) coils of a magnetic resonance imaging (MRI) system. We have studied numerically and experimentally two designs of metasurfaces with different tunability mechanisms. The first design is a hybrid structure based on periodic wires with extremities penetrating high-permittivity dielectric volumes, where tunability achieved by changing properties of the dielectric parts. The second metasurface is formed by an array of capacitively loaded telescopic wires that permit to adjust the eigenmode resonance frequencies by mechanical expansion of the wires. Both metasurfaces demonstrated the spectacular capability to locally enhance the magnetic field of an external RF coil being precisely tuned to the Larmor frequency of a clinical MRI scanner.
关键词： metasurfaces,RF coils,tunability,eigenmode resonance frequencies,magnetic resonance imaging
更新于2025-09-09 09:28:46
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Single-Breath-Hold Whole-heart Unenhanced Coronary MRA Using Multi-shot Gradient Echo EPI at 3T: Comparison with Free-breathing Turbo-field-echo Coronary MRA on Healthy Volunteers
摘要： We investigated the feasibility of single breath hold unenhanced coronary MRA using multi-shot gradient echo planar imaging (MSG-EPI) on a 3T-scanner. Methods: Fourteen volunteers underwent single breath hold coronary MRA with a MSG-EPI and free-breathing turbo field echo (TFE) coronary MRA at 3T. The acquisition time, signal to noise ratio (SNR), and the contrast of the sequences were compared with the paired t-test. Readers evaluated the image contrast, noise, sharpness, artifacts, and the overall image quality. Results: The acquisition time was 88.1% shorter for MSG-EPI than TFE (24.7 ± 2.5 vs 206.4 ± 23.1 sec, P < 0.01). The SNR was significantly higher on MSG-EPI than TFE scans (P < 0.01). There was no significant difference in the contrast on MSG-EPI and TFE scans (1.8 ± 0.3 vs 1.9 ± 0.3, P = 0.24). There was no significant difference in image contrast, image sharpness, and overall image quality between two scan techniques. The score of image noise and artifact were significantly higher on MSG-EPI than TFE scans (P < 0.05). Conclusion: The single breath hold MSG-EPI sequence is a promising technique for shortening the scan time and for preserving the image quality of unenhanced whole heart coronary MRA on a 3T scanner.
关键词： men,coronary angiography,respiration,magnetic resonance imaging
更新于2025-09-09 09:28:46
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[SpringerBriefs in Applied Sciences and Technology] Internet of Things and Personalized Healthcare Systems || Role of Imaging Modality in Premature Detection of Bosom Irregularity
摘要： Since last 60 years, bosom (breast) tumor is the major cause of death amid females worldwide. Earliest possible detection will raise the endurance rate of patients. Premature detection of bosom tumor is big challenge in medical science. Medical studies proven that imaging modalities like mammography, thermography, ultrasound, and magnetic resonance imaging (MRI) play a vigorous role to detect breast irregularity earliest. This paper enhances the knowledge on two imaging practices, one is mammography and another is thermography. It aids to identify the limitations in existing technologies and helps to plan the new methodology.
关键词： Bosom tumor,Ultrasound,MRI—magnetic resonance imaging,Mammography,Thermography
更新于2025-09-09 09:28:46
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Production of Hyperpolarized 129Xe Using Spin Exchange Optical Pumping
摘要： We present a constructed setup for polarizing 129Xe noble gas. Hyperpolarized 129Xe has been obtained via spin exchange with an optically pumped rubidium vapor. Optical pumping is based on polarizing the valence electron of rubidium by the resonant absorption of a circularly polarized laser light. The magnetic ?eld of 30 G was used for obtaining 129Xe polarization. The apparatus for detecting polarization is a nuclear magnetic resonance spectrometer. The highest 129Xe polarization of 54% has been obtained using 60 W circularly polarized laser light with wavelength of 794.7 nm. The measured longitudinal relaxation time of the hyperpolarized 129Xe was 72.3 minutes.
关键词： Nuclear magnetic resonance,Polarized 129Xe,Spin exchange,Polarization,Optical pumping,Rubidium
更新于2025-09-09 09:28:46
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Imaging of Peripheral Vascular Malformations: Imaging Modalities Mini Review
摘要： Currently the major aim inperipheral vascular malformation (PVM) diagnosis, crucial for subsequent management and treatment, is to identify its hemodynamic characteristics. Other significant features that should be specified by a radiologist is the exact location of the anomaly, its size and morphology. Until recently the diagnostic methods available for comprehensive evaluation of malformations have been rather limited. Moreover, they were often associated with the necessity of exposing the patient to X-ray radiation and with invasive procedures, asfor example in angiography. The development of imaging techniques used in the diagnosis of vascular abnormalities in recent years, especially magnetic resonance imaging (MRI), has largely contributed to improved diagnostic value of the tests. In this article we review the currently available imaging modalities with particular consideration of magnetic resonance imaging and its capability to distinguish between high-flow and low-flow malformations.
关键词： Imaging,Low-flow and high-flow malformations,Magnetic resonance,Vascular malformation
更新于2025-09-09 09:28:46