Saturation-prolongated and inhomogeneity-mitigated chemical exchange saturation transfer imaging with parallel transmission.

Chemical exchange saturation transfer (CEST) imaging benefits from a longer saturation duration and a higher saturation duty cycle. Dielectric shading effects occur when the radiofrequency (RF) wavelength approaches the object size. Here, we proposed a simultaneous parallel transmission-based CEST (pTx-CEST) sequence to prolongate the saturation duration at a 100% duty cycle and improve the RF saturation homogeneity in CEST imaging. The simultaneous pTx-CEST sequence was implemented by switching the CEST saturation module from the non-pTx to pTx mode, using the pTx functionality with both transmit channels being driven simultaneously (instead of time-interleaved). The optimization of amplitude ratio and phase difference settings between RF channels for best B1 homogeneity was performed in phantoms of two different sizes mimicking the human brain and abdomen. The optimal amplitude and phase settings generating the best B1 homogeneity in the phantoms were used in pTx-CEST scans of the human study. The comparison of the maximum achievable saturation duration between the non-pTx-CEST and pTx-CEST sequences was performed in a protein phantom, healthy volunteers, and a metastatic brain tumor patient. The optimal amplitude ratio and phase difference setting between transmit channels manifested circular and elliptical polarization in the head-sized and abdomen-sized phantoms. In the brain, the maximum saturation durations achieved at a 100% duty cycle using the simultaneous pTx-CEST sequence were prolonged to 2240, 3220, and 4200 ms compared with 980 ms using the non-pTx-CEST sequence at repetition times of 3, 4, and 5 s, respectively. The longer saturation duration helped improve the image contrast between the tumor and the normal tissue in the patient. The optimized elliptical polarization mode saturation pulses yielded improved uniformity of CEST signals acquired from the human abdomen. The proposed simultaneous pTx-CEST sequence enabled essentially arbitrarily long saturation duration at a 100% duty cycle and helped reduce the dielectric shading effects with the optimized RF setting.

Spatial Pattern and Fairness Measurement of Educational Resources in Primary and Middle Schools: A Case Study of Chengdu-Chongqing Economic Circle.

China's education has developed rapidly in recent years, but the issue of educational equality still exists. Currently, there are few studies on educational resources, and their spatial pattern and fairness remain unclear. Thus, this study selected the point of interest data and spatial analysis methods to depict the spatial pattern of educational resources (containing the number of teachers, students, facilities, etc.). Then, we evaluated the equity of educational resources (including the number of schools and school teachers) in terms of geographic and population distribution by combining statistical yearbook data with two indices (the index of dissimilarity and agglomeration degree) to promote healthy urban development. The results show the following. (1) Educational resources have a multicenter spatial structure of "dual cores and multiple sub-centers". The Moran index reflects a weak positive spatial correlation between educational resources. (2) The index of dissimilarity is between 0.02 and 0.21, which shows that the allocation of resources is relatively balanced. Regarding internal units, obvious differences exist in the agglomeration degree and equilibrium of educational resources.

Multiple-phase spiral CT findings of pancreatic vasoactive intestinal peptide-secreting tumor: A case report.

The present study reports a case of pancreatic vasoactive intestinal peptide-secreting tumor (VIPoma), of 2.2 cm in diameter, arising from the region of the uncus of the pancreas with liver metastases in a 50-year-old patient, which demonstrated unusual multiple-phase spiral computed tomography (MPSCT) results. The pancreatic lesion was isodense compared with the pancreatic parenchyma. During the hepatic artery phase and portal venous phase, the mass was hypodense compared with the enhanced pancreas, with the mean CT attenuation (HU) values being 56 HU and 66 HU, respectively. During the hepatic parenchymal phase, the mass became hyperdense with the mean CT attenuation values being 74 HU. The process of contrast-enhanced MPSCT demonstrated progressive strengthening. Pancreaticoduodenectomy and wedge resection of a number of the liver metastases was performed. There are only a limited number of studies reporting CT findings of pancreatic VIPoma and no MPSCT findings have been described previously.

Eosinophilic gastroenteritis associated with eosinophilic cystitis: Computed tomography and magnetic resonance imaging findings.

Eosinophilic gastroenteritis (EG) is a rare, distinct clinical entity, and EG associated with eosinophilic cystitis (EC) is extremely rare and has not been well documented. Here, we report two cases of EG and coexistent EC along with findings from computed tomography (CT) and magnetic resonance imaging (MRI). An 18-year-old male with a history of hematuria, urgency and occasional urodynia for two weeks and a 34-year-old male with a history of abdominal distention for one week were admitted to our hospital. Abdominal contrast-enhanced CT in both patients revealed wall thickening in different parts of the gastrointestinal tract with inhomogeneous reinforcement, coexistent with local or diffuse bladder wall thickening with progressive enhancement, and also showed that the bladder mucosal lining was nondestructive. Pelvic MRI showed that the local or diffuse thickened bladder wall was iso-intense on T1-weighted images, hypo-intense on T2-weighted images, and slightly restricted on diffusion weighted imaging (DWI) in one case. After therapy, the thickened wall of the gastrointestinal tract and urinary bladder had improved markedly in the two cases. To the best of our knowledge, this is the first report on the radiological imaging of EG and coexistent EC by both CT and MRI and the first with DWI findings.

Pelvic solitary plasmacytoma: computed tomography and magnetic resonance imaging findings with histopathologic correlation.

OBJECTIVE: To describe the imaging features of pelvic solitary plasmacytoma and to correlate them with the pathologic grade. MATERIALS AND METHODS: A retrospective study was performed on the imaging features of 10 patients with a histological diagnosis of pelvic solitary plasmacytoma. The imaging studies were assessed for bone expansion, cortical destruction, signal intensity/density of soft tissue mass and enhancement manifestations, which were then correlated to the pathologic grade. RESULTS: The imaging features of pelvic solitary plasmacytoma revealed 3 different types: multilocular type (n = 5), unilocular type (n = 2) and complete osteolytic destruction type (n = 3) on computed tomography and MRI. Pathologically, the tumors were classified into low, intermediate and high grades. Features such as multilocular change, perilesional osteosclerosis, slight expansion, local bone cortex disruptions and masses inside bone destruction, often suggest a low-grade solitary plasmacytoma; complete osteolytic destruction, huge soft tissue mass, and osseous defects imply a higher pathologic grade. CONCLUSION: Pelvic solitary plasmacytoma has various imaging manifestations, while a slight expansile osteolytic feature with multilocular change or homogeneous enhancement highly suggests its diagnosis. The distinctive imaging features of pelvic solitary plasmacytoma are well correlated to the pathologic grade.

Desmoplastic small round cell tumor: A case report of a rare differential diagnosis of solid tumors of the pleura.

Desmoplastic small round cell tumor (DSRCT) presents as a rare separate clinical pathological entity, and pleural DSRCT is very rare. Following review of the English literatures it was revealed that, to date, <15 cases of primary DSRCT of the pleura have been reported worldwide. Among these, there are few computed tomography (CT) findings of pleural DSRCT which have previously been described in detail. The present study reports a pathologically proven case of pleural DSRCT, with varying contrast CT findings in a 72-year-old female, which appeared as a large (12.0×10.0×6.5 cm), smooth, oval mass in the left lower thorax with slight-moderate uniform enhancement on contrast-enhanced CT. To the best of our knowledge, the present report is the first to describe the large solid-tumor pattern and the patient is the eldest reported case of pleural DSRCT.

Computed tomography findings of a solitary extramedullary plasmacytoma of the spleen: A case report and literature review.

Solitary extramedullary plasmacytoma (EMP) of the spleen is a rare condition. The present study describes the case of a 23-year-old female with an extremely rare solitary EMP of the spleen. Upon examination, the tumor demonstrated unusual and notable multiple-phase spiral computed tomography (CT) findings. The lesion was a solitary, well-defined mass, with areas of variable splenic necrosis and cystic degeneration. Contrast-enhanced CT revealed progressive enhancement of the lesion in the cystic wall, internal septa and solid portion, a finding that has not previously been described. The patient underwent a splenectomy and recovered without complications. No evidence of tumor recurrence has occurred during the past two years of follow-up. To the best of our knowledge, this is the first study to examine the CT findings of a solitary EMP of the spleen. The study aimed to investigate the imaging features of solitary EMP, in particular the multiple-phase spiral CT findings, and raise awareness of the disease to reduce misdiagnoses.