ABSTRACT
Through the analysis of PAC module faults in two GE Signa HDxt 1.5 T MRI cases, the fault performance was analyzed. According to the working principle of PAC module, the fault was analyzed and processed, and then the suspicious fault parts were located and repaired to make the equipment run normally. Finally, the operating principles of PAC module in terms of power supply, signal transmission and data transmission were summarized to facilitate the subsequent quickly and find out fault points for maintenance accurately.
ABSTRACT
Proton magnetic resonance spectroscopy (MRS) of the human brain has proven to be a useful technique in several neurological and psychiatric disorders and benefits from higher scanners as signal intensity and spectral resolution are proportional to the magnetic strength. OBJECTIVE: To investigate the effects of the magnetic on the measurement of brain metabolites in a typical routine clinical setting. METHODS: Single voxel spectra were acquired from the posterior cingulate cortex in 26 healthy subjects. Each subject was scanned consecutively at 1.5T and 3.0T in a randomly distributed order. RESULTS: SNR and peak width improvements were observed at higher s. However, SNR improvement was lower than the theoretical two-fold improvement. Other than the values obtained for creatine (Cre) and myo-Inositol (mI), which were both higher at 3.0T, all metabolite concentrations obtained were roughly the same at both strengths. All the metabolite concentrations were estimated with a Cramer Rao lower bounds (CRLB) lower than 15% of the calculated concentrations. CONCLUSIONS: Even though the present study supports the expected benefits of higher strength for MRS, there are several factors that can lead to different quantitative results when comparing 1.5T to 3.0T MRS. Future comparative studies are necessary to refine the metabolite thresholds for early detection and quantification of distinct neurological and psychiatric disorders using 3.0T MRS.
Espectroscopia de prótons por ressonância magnética (MRS) tem se mostrado uma técnica bastante útil em diversas doenças neurológicas e psiquiátricas. A utilização de sistemas de mais alto campo magnético favorece essa técnica uma vez que a intensidade do sinal e a resolução espectral são proporcionais à intensidade do campo. OBJETIVO: Avaliar o efeito do campo magnético sobre a medida dos níveis dos metabólitos cerebrais em uma típica rotina clínica. MÉTODOS: Os dados foram obtidos em 26 indivíduos saudáveis nos sistemas de 1.5T e 3.0T. As aquisições foram feitas sequencialmente e a ordem foi distribuida randomicamente.RESULTADOS: Foram observadas melhoras na relação sinal-ruído (SNR) e na largura de linha dos picos nos dados obtidos em campo maior. No entanto, a melhoria na SNR foi menor que o esperado teoricamente que seria o dobro da obtida em 1.5T. Exceto pelos valores obtidos para creatina e mio-inositol, que foram maiores em 3.0T, todas as concentrações de metabólitos obtidas foram aproximadamente a mesmo em ambos os campos. Todas as concentrações de metabólitos foram estimadas com Cramer Rao lower bounds (CRLB) inferior a 15% das concentrações calculadas. CONCLUSÕES: Apesar de o presente estudo dar suporte aos benefícios gerados pelo aumento do campo para a técnica de MRS, existem fatores que podem levar a diferentes resultados quantitativos quando se compara espectroscopia em 1.5T e 3.0T. Estudos comparativos serão necessários para refinar os limiares dos níveis de metabólitos para melhorar a acurácia da detecção de doenças neurológicas utilizando espectroscopia em 3.0T.
Subject(s)
Humans , Magnetic Resonance Spectroscopy , CerebrumABSTRACT
OBJECTIVE: To validate the optimal cardiac phase and appropriate acquisition window for three-dimensional (3D) whole-heart coronary magnetic resonance angiography (MRA) with a steady-state free precession (SSFP) sequence, and to compare image quality between SSFP and Gd-enhanced fast low-angle shot (FLASH) MR techniques at 1.5 Tesla (T). MATERIALS AND METHODS: Thirty healthy volunteers (M:F = 25:5; mean age, 35 years; range, 24-54 years) underwent a coronary MRA at 1.5T. 3D whole-heart coronary MRA with an SSFP was performed at three different times: 1) at end-systole with a narrow (120-msec) acquisition window (ESN), 2) mid-diastole with narrow acquisition (MDN); and 3) mid-diastole with wide (170-msec) acquisition (MDW). All volunteers underwent a contrast enhanced coronary MRA after undergoing an unenhanced 3D true fast imaging with steady-state precession (FISP) MRA three times. A contrast enhanced coronary MRA with FLASH was performed during MDN. Visibility of the coronary artery and image quality were evaluated for 11 segments, as suggested by the American Heart Association. Image quality was scored by a five-point scale (1 = not visible to 5 = excellent). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated at the proximal coronary arteries. RESULTS: The SSFP sequence rendered higher visibility coronary segments, higher image quality, as well as higher SNR and CNR than the Gd-enhanced FLASH technique at 1.5T (p < 0.05). The visibility of coronary segments, image quality, SNR and CNR in the ESN, MDN and MDW with SSFP sequence did not differ significantly. CONCLUSION: An SSFP sequence provides an excellent method for the 3D whole-heart coronary MRA at 1.5T. Contrast enhanced coronary MRA using the FLASH sequence does not help improve the visibility of coronary segments, image quality, SNR or CNR on the 3D whole-heart coronary MRA.
Subject(s)
Adult , Female , Humans , Male , Middle Aged , Young Adult , Contrast Media , Coronary Vessels/anatomy & histology , Gadolinium , Image Processing, Computer-Assisted , Imaging, Three-Dimensional , Magnetic Resonance Angiography/methods , Organometallic Compounds , Reference ValuesABSTRACT
In the study we assessed the distortion of 7.0 T magnetic resonance (MR) images in reference to 1.5 T MR images in the radiosurgery of metastatic brain tumors. Radiosurgery with Gamma Knife Perfexion(R) was performed for the treatment of a 54-yr-old female patient with multiple brain metastases by the co-registered images of the 7.0 T and 1.5 T magnetic resonance images (MRI). There was no significant discrepancy in the positions of anterior and posterior commissures as well as the locations of four metastatic brain tumors in the co-registered images between 7.0 T and 1.5 T MRI with better visualization of the anatomical details in 7.0 T MR images. This study demonstrates for the first time that 7.0 T MR images can be safely utilized in Perfexion(R) Gamma Knife radiosurgery for the treatment of metastatic brain tumors. Furthermore 7.0 T MR images provide better visualization of brain tumors without image distortion in comparison to 1.5 T MR images.