The gradient field, one of the core magnetic fields in magnetic resonance imaging (MRI) systems, is generated by gradient coils and plays a critical role in spatial encoding and the generation of echo signals. The uniformity or linearity of the gradient field directly impacts the quality and distortion level of MRI images. However, traditional point measurement methods lack accuracy in assessing the linearity of gradient fields, making it difficult to provide effective parameters for image distortion correction. This paper introduced a spherical measurement-based method that involved measuring the magnetic field distribution on a sphere, followed by detailed magnetic field calculations and linearity analysis. This study, applied to assess the nonlinearity of asymmetric head gradient coils, demonstrated more comprehensive and precise results compared to point measurement methods. This advancement not only strengthens the scientific basis for the design of gradient coils but also provides more reliable parameters and methods for the accurate correction of MRI image distortions.
Magnetic Resonance Imaging/instrumentation* ; Humans ; Image Processing, Computer-Assisted/methods* ; Nonlinear Dynamics ; Magnetic Fields ; Algorithms ; Phantoms, Imaging

The gradient coils of MRI equipment can induce vibrations in implantable medical devices, causing periodic vibrations of implantable medical devices with respect to the surrounding tissue. This not only results in instrument failure but also causes discomfort to the patient. Therefore, studying the vibration characteristics of implantable devices under different scanning sequences and the orientation of the device relative to the magnetic field is crucial for comprehending vibration performance. This study observed the vibration spectra of a full cranial bone-implanted neurostimulator by using laser vibrometry under typical rapid imaging sequences and explored the impact of different magnetic field orientations on vibration. The results demonstrated that the rapid echo sequences induced diverse and rich vibration components, whereas the planar echo sequences caused relatively simple vibrations. Additionally, the strongest vibrations normally occurred in the maximum conductive surface parallel to the phase-coded direction. It revealed the factors influencing the vibrations of skull fixation active implantable devices and provided guidance for enhancing device safety and protecting patient well-being during MR examinations.
Vibration ; Magnetic Resonance Imaging ; Deep Brain Stimulation/instrumentation* ; Magnetic Fields ; Humans

OBJECTIVE: To study the safety and efficacy of magnetic resonance imaging (MRI)-compatible incubator in cranial MRI examination for neonates. METHODS: A total of 120 neonates who were hospitalized in three hospitals and needed to undergo MRI examination were randomly divided into a control group and an experimental group, with 60 neonates in each group. The neonates in the experimental group were transferred with MRI-compatible incubator and underwent cranial MRI examination inside the MRI-compatible incubator, and those in the control group were transferred using a conventional neonatal transfer incubator and then underwent MRI examination outside the incubator. The two groups were compared in terms of the primary efficacy index (total examination time), secondary efficacy indices (times of examination, MRI completion rate on the first day of use), and safety indices (incidence rate of adverse events and vital signs). RESULTS: There were no significant differences in total examination time, times of examination, and MRI completion rate on the first day of use between the two groups ( CONCLUSIONS The use of MRI-compatible incubator does not significantly shorten the examination time of cranial MRI, but it does provide a relatively stable environment for examination with acceptable safety. There is a need for further studies with a larger population.
Humans ; Incubators, Infant ; Infant, Newborn ; Magnetic Resonance Imaging/instrumentation* ; Prospective Studies ; Skull/diagnostic imaging*

In order to evaluate the quality of different brands of magnetic resonance imaging system, optimize the quality of equipment repair and maintenance, and ensure the quality and safety of the equipment in clinical use. Meanwhile build the reliability evaluation model of magnetic resonance imaging equipment based on the large failure data collected by magnetic resonance repair system. In this paper, using the fault data of a certain brand of magnetic resonance in the past two years, applying the statistical judgment criterion, selecting the appropriate statistical distribution model, and finally fitting the equipment reliability evaluation model based on the non-homogeneous Poisson process, and then obtaining the magnetic resonance imaging equipment. Reliability evaluation indicators such as cumulative fault strength function, magnetic resonance imaging equipment fault density function, and mean time between failures. According to the calculated reliability index, on the one hand, it can evaluate the system reliability quality of a certain brand of magnetic resonance imaging equipment, and then evaluate the quality of different brands of magnetic resonance imaging equipment, on the other hand, it can help hospital equipment managers to carry out operational optimization, maintenance strategy development and safety management of magnetic resonance imaging equipment.
Equipment and Supplies, Hospital/standards* ; Magnetic Resonance Imaging/instrumentation* ; Reproducibility of Results

PET/MR is a high-end medical imaging equipment with integrating PET and MR equipment into the highly sophisticated one and has rich clinical and molecular diagnosis functions, can obtain comprehensive information about the human body structure, function and metabolism, is of great value for the diagnosis and treatment of disease improvement. In this paper, through the analysis of existing production risk points on one of the primary stages of the whole product life cycle, combining with the medical device good manufacture practice, some suggestions have been put forward exploratively to field inspection for PET/MR manufacturers. It has certain significance for regulators of medical devices to clear the production risk point and improve verification efficiency during field inspection.
Equipment Design ; Humans ; Magnetic Resonance Imaging ; instrumentation ; Positron-Emission Tomography ; instrumentation

MRI simulation images quality of head and neck coil scanning is better than that of radiotherapy surface coil, but currently the head and neck coil is not compatible with radiotherapy positioning devices. In this paper, a new fixation device is developed based on computer reverse engineering technology, which can be used in combination with head and neck coil. This article focuses on discussing the feasibility of the new device in radiotherapy. The obtained ACR phantom and Cat phantom 504 images were used to analyze MR and CT images quality assurance indicators. The dose attenuation of 6 MV photons was measured using the ionization chamber. The results showed each index met the clinical application requirements of intracranial tumor radiotherapy, thereby it can be used in intracranial tumor radiotherapy.
Feasibility Studies ; Head and Neck Neoplasms ; diagnostic imaging ; Humans ; Magnetic Resonance Imaging ; instrumentation ; Phantoms, Imaging ; Radiotherapy Planning, Computer-Assisted

ObjectiveTo explore the practicability and safety of the F4.8 visual miniature nephroscope in the diagnosis and treatment of hematospermia.

METHODSThis study included 12 cases of refractory hematospermia accompanied by perineal or lower abdominal pain and discomfort. All the patients failed to respond to two months of systemic anti-inflammatory medication and local physiotherapy. Seminal vesicle tumor and tuberculosis were excluded preoperatively by rectal seminal vesicle ultrasonography, MRI or CT. Under epidural anesthesia, microscopic examination was performed with the F4.8 miniature nephroscope through the urethra and ejaculatory duct orifice into the seminal vesicle cavity, the blood clots washed out with normal saline, the seminal vesicle stones extracted by holmium laser lithotripsy and with the reticular basket, the seminal vesicle polyps removed by holmium laser ablation and vaporization, and the seminal vesicle cavity rinsed with diluted iodophor after operation.

RESULTSOf the 10 patients subjected to bilateral seminal vesiculoscopy, 3 with unilateral and 2 with bilateral seminal vesicle stones were treated by holmium laser lithotripsy, saline flushing and reticular-basket removal, 2 with seminal vesicle polyps by holmium laser ablation and vaporization, and the other 3 with blood clots in the seminal vesicle cavity by saline flushing for complete clearance. The 2 patients subjected to unilateral seminal vesiculoscopy both received flushing of the seminal vesicle cavity for clearance of the blood clots. The operations lasted 10－55 (25 ± 6) minutes. There were no such intra- or post-operative complications as rectal injury, peripheral organ injury, and external urethral sphincter injury. The urethral catheter was removed at 24 hours, anti-infection medication withdrawn at 72 hours, and regular sex achieved at 2 weeks postoperatively. The patients were followed up for 6－20 (7 ± 2.3) months, during which hematospermia and related symptoms disappeared in 10 cases at 3 months and recurrence was observed in the other 2 at 4 months after surgery but improved after antibiotic medication.

CONCLUSIONSThe F4.8 visual miniature nephroscope can be applied to the examination of the seminal vesicle cavity and treatment of seminal vesicle stones and polyps, with the advantages of minimal invasiveness, safety and reliability.

Calculi ; diagnostic imaging ; surgery ; Ejaculatory Ducts ; Endoscopes ; Endoscopy ; instrumentation ; Genital Neoplasms, Male ; Hemospermia ; diagnosis ; therapy ; Holmium ; Humans ; Lasers, Solid-State ; Lithotripsy ; Magnetic Resonance Imaging ; Male ; Natural Orifice Endoscopic Surgery ; instrumentation ; Neoplasm Recurrence, Local ; Postoperative Complications ; Reproducibility of Results ; Seminal Vesicles ; diagnostic imaging ; Urethra

This study based on the technology evolution theory, S-curve and bibliometrics, verified product evolution was accompanied by the evolution and transition of a number of sub technologies. It judged MRI was in the stage of underdevelopment and a new round of technology was being developed. It was found that the value of MRI equipment in scientific research or clinical application in foreign countries was higher than that in China by comparing the literatures at home and abroad. And there was a gap between China and the world scientific center in the independent R&D capability. The study verified the applicability of the technical evolution theory and the evaluation empirical laws in the medical devices evaluation, and explored the operability of the assessment tools. This paper not only provided a reference for equipment configuration, but also showed the gaps of key technologies in home and abroad and provided a reference for upgrading China's independent innovation and industrial technology.
China ; Industry ; Magnetic Resonance Imaging ; instrumentation ; Technology ; trends

OBJECTIVES: An animal experiment clarified that insertion of an orthodontic apparatus activated the trigeminal neurons of the medulla oblongata. Orthodontic tooth movement is known to be associated with the sympathetic nervous system and controlled by the nucleus of the hypothalamus. However, the transmission of both has not been demonstrated in humans. The purpose of this study were to examine the activated cerebral areas using brain functional magnetic resonance imaging (MRI), when orthodontic tooth separators were inserted, and to confirm the possibility of the transmission route from the medulla oblongata to the hypothalamus. METHODS: Two types of alternative orthodontic tooth separators (brass contact gauge and floss) were inserted into the right upper premolars of 10 healthy volunteers. Brain functional T2*-weighted images and anatomical T1-weighted images were taken. RESULTS: The blood oxygenation level dependent (BOLD) signals following insertion of a brass contact gauge and floss significantly increased in the somatosensory association cortex and hypothalamic area. CONCLUSION Our findings suggest the possibility of a transmission route from the medulla oblongata to the hypothalamus.
Brain Mapping ; methods ; Healthy Volunteers ; Humans ; Hypothalamus ; diagnostic imaging ; Magnetic Resonance Imaging ; methods ; Medulla Oblongata ; diagnostic imaging ; Tooth Movement Techniques ; instrumentation

Rectal cancer is one of the common cancers which poses a threat to the health of mankind. In recent years. Multi-modality treatment strategies for locally advanced rectal cancer improve the treatment efficiency. Accurate prediction of the treatment response after the neoadjuvant chemoradiotherapy (CRT) can guide more suitable treatment strategy. MERCURY study proved the prognostic value of post-CRT standard morphologic MRI(T2-weighted) assessment of tumor regression grade(TRG), and MRI assessment of circumferential resection margin can guide the definitive surgery. Compared with standard morphologic MRI (T2-weighted), functional MRI, including diffusion weighted imaging (DWI) and dynamic contrast enhanced (DCE) MRI, has shown more promising results for the prediction of therapeutic response in rectal cancer. The addition of diffusion-weighted images to T2-weighted images improves the accuracy of restaging examinations for determination of complete pathologic responders. DCE can reflect the tumor micro-vascular environment, and the change of perfusion in response to treatment. These images have the potential to improve the accuracy of therapeutic response in rectal cancer.
Chemoradiotherapy ; statistics & numerical data ; Contrast Media ; Diffusion Magnetic Resonance Imaging ; statistics & numerical data ; Humans ; Magnetic Resonance Imaging ; methods ; statistics & numerical data ; Margins of Excision ; Neoadjuvant Therapy ; statistics & numerical data ; Neoplasm Staging ; instrumentation ; methods ; statistics & numerical data ; Prognosis ; Rectal Neoplasms ; blood supply ; diagnostic imaging ; pathology