[en] Objective: To investigate the technique and application of nasolacrimal duct imaging using MR hydrography. Methods: Eight healthy volunteers(16 lacrimal ducts) and 17 patients affected by primary epiphora(32 lacrimal ducts) underwent MRI with three-dimensional fast recovery fast spin echo (3D-FRFSE) MR daeryocystography (MRD) sequence after sterile saline solution had been instilled into the conjunctival sac. For all patients affected by primary epiphora, FRFSE T₂-weighted oblique coronal and axial images were obtained after MRD. All patients (32 lacrimal ducts) underwent lacrimal endoscopy, which served as a standard of reference for confirming MR findings. Results: Eight cases of 16 normal lacrimal passages were showed by MR hydrography with administering topical sterile saline solution, which demonstrated the lacrimal sac well and whole course of the nasolacrimal duct. Endoscopic findings confirmed nasolacrimal duct obstruction secondary to chronic non-specific inflammation: the color of the mucosa of the nasolaerimal ducts was grey-red, and the obstructive sinuses were filled with nonelastic grey-white membrane. The accuracy of 3D-FRFSE MRD sequence in diagnosing obstructive level was 78% (25/32). The lacrimal ducts above the obstructive level showed watery hypo-intensity on 3D-FRFSE MRD, and the lacrimal ducts below the obstructive level could not be showed. Abnormal findings were presented in all cases of obstructive nasolacrimal ducts with Axi-FRFSET₂WI and Cor-FRFSET₂WI sequences: long T₂ fluid signals were seen in the lumens of the lacrimal sac and (or) nasolacrimal duct above the obstructive level, equal or slightly long T₂ soft-tissue signals were seen in the lumens of the nasolacrimal duct below the obstructive level, and the mucosa of the ducts thickened. Conclusion: MR imaging performed after the topical administration of sterile saline solution can reveal normal nasolaerimal duct and is feasible in evaluating obstructive nasolacrimal ducts. (authors)

[en] Objective: To compare the efficiency of enhanced T₂^* weighted angiography (ESWAN) sequence with that of a conventional T₂^* -weighted gradient-recalled-echo (GRE T₂^* WI) sequence for the detection of hemorrhagic shearing lesions in patients with diffuse axonal injury (DAI). And combined with MRI parameters, to further discuss the principles and virtues of ESWAN sequence. Methods: Seventeen patients with DAI were enrolled in this study. The raw data acquired from ESWAN scan were postprocessed by using the mean square root of multi-echoes. Then, the postprocessed images were compared with the conventional GRE T₂^* weighted images. The global and regional (superficial, deep and posterior fossa) lesion numbers determined by both sequences were compared by using Wilcoxon signed ranks test (two- tailed). Differences were considered to be significant at P≤0.05. Results: Hemorrhagic lesions were more obvious on ESWAN images than those on conventional GRE T₂^* weighted images. The median and range value of the detected lesion numbers on ESWAN images were 27 and (1-239) in whole brain, 13 and (1- 89) in cerebral superficial region, 5 and (0-111) in cerebral deep region and 1 and (0-39) in posterior fossa region, respectively; whereas, on GRE T₂^* weighted images, they were 7 and (1-34) in whole brain, 5 and (1-27) in cerebral superficial region, 2 and (0-25) in cerebral deep region and O and (0-4) in posterior fossa region, respectively. There were significant statistical differences between the two sequences in revealing the lesions in all the four regions (Z=-3.519, -3.182, -3.185, -2.677, P< 0.05). Conclusion: In ESWAN sequence, multi-echo acquisition ensured sufficient magnetic susceptibility for detecting small hemorrhagic lesions. So, ESWAN is more sensitive to small hemorrhage, which revealed more hemorrhagic lesions than conventional GRE T₂”* WI and presented more valuable information for the diagnosis of DAI. (authors)

[en] Objective: To explore the diagnostic value of MRI in the early atherosclerosis. Materials and Methods: Atherosclerosis was induced in 20 New Zealand White male rabbits with high cholesterol diet. Rabbits underwent serial MRI at 9 and 18 weeks after high cholesterol diet. Axial T₁ and fat-suppressed PDWI spin echo images of the abdominal aorta were obtained above and below the right renal arteries. The signal intensity and morphologic features of plaque in the various phases after high cholesterol diet in MRI were analyzed and compared with those of histopathology. Results: Plaque could be observed in all animals on MRI at 9 weeks after high cholesterol diet, and mild enhancement of the plaque could be noted on enhanced imaging. Imaging effect was the best at T₁ sequence. Plaque size increased gradually at 18 weeks. Plaque and vessel wall were all enrichment. In histopathology, foam cells, collagen and matrix fiber component can be seen in the various phases. Conclusion: The conventional MRI technique can be used to assess the formation and development of the early atherosclerosis dynamically and histologically. (authors)

[en] Objective: To discuss the values of imaging technique of diffusion tensor imaging (DTI) used in normal volunteers and brain tumor patients, and to assess the changing regularity of several evaluating metrics of DTI. Methods: Ten volunteers and nineteen brain tumor patients underwent routine and DTI scan and then the parametric maps were reconstructed. In ten volunteers, the values of FA, Iso, VrA, and ExAt of the main white matter bundles and nerve nucleus were measured; In nineteen patients, the data gathered from damaged white matter and contralateral intact areas were analyzed statistically, including paired T test, correlation analysis, and analysis of variance. Results: In normal brain DTI maps, the values of each metrics distributed regularly according to tissues structure; In brain tumor patients, the destroys of surrounding tissues and other various changes caused by tumors, mass effect, and edema could be clearly demonstrated. For each metric, the difference between lesion group and intact group was significant (P<0.001), and there was good correlation between FA values and VrA values in lesions (r=0.922, P<0.001). The changing magnitude of VrA in lesions compared with others metrics had significant meanings (P<0.001), so VrA could be the most sensitive metric. Conclusion: DTI can clearly depict the characteristic of normal brain, demonstrate and assess quantitatively the conditions caused by tumors, and instruct pre-operation plan and post-operation assessment, so the technique has great clinic values. (author)

[en] Objective: To research the value of ECG-or PG-gating single segmented multi-phase fast gradient-recalled echo sequence (gated FMPGR) application in intracranial aneurysms. Methods: All patients were examined with gated FMPGR. The images obtained with gated FMPGR were displayed by paging demonstration and compared with MOTSA or 3D PC MRA. The signal intensity (SI) wave of the aneurysms, hematomas and the normal cerebral tissue were analysed with statistics. Results: Underwent the gated FMPGR sequence, the blood flow were manifested and the SI changes obviously compared with the normal cerebral tissue in all 43 intracranial aneurysms (t=17.21, P<0.01), 31 patients with aneurysms displayed the relation between the neck of aneurysms and its parent artery to aneurysm. Nevertheless the blood flow were unseen and the curves were steady in the 12 cerebral hematomas and 1 cavernous hemangioma. The SI variance of hematomas is similar to the normal cerebral tissue (t=1.79, P=0.16). Conclusion: The gated FMPGR sequence can differentiate blood flow from static tissue significantly, so is a valuable complementation of routine MRA

[en] Objective: To investigate normal anatomy and MR findings of fetal main organs. Methods: Forty-seven fetus underwented fast MR imaging, SSFSE sequence was used, the normal anatomy and MR findings of fetal main organs was observed in different gestational age. The organs included: brain, lungs, heart, liver, spleen, gastrointestinal tract, urinary collecting systems, bladder, bones, spine, and subcutaneous fat. Results: Results of MR in 47 fetus showed that the main organs had developed by 20-week-old fetus, about 20 weeks gestation, cerebral cortical surface was smooth, no cortical gyri and sulci, then cortical gyri and sulci developed slowly. The lungs, trachea, bronchus, gastrointestinal tract, renal collecting system and bladder showed high signal intensity; the heart, great vessels, liver, spleen, bones and muscles appeared hypointense; the kidneys appeared isointense, the spine had developed and subcutaneous fat was seen in 20-week-old fetus, the subcutaneous fat increased with fetus maturating. Conclusion: Normal anatomy and MR findings of fetal main organs were clearly showed by fast MR imaging, and they are different from the newborns. (authors)

[en] Objective To observe the rates of repeated computed tomographic scans (CTs) in a cohort of patients with coronavirus disease-2019 (COVID-19) and to assess the validity of repeat CTs. Methods: Each CT was recorded, and the validity of the repeated CTs was assessed. Results: The 394 patients underwent a total of 1493 CTs. Of the 394 patients, 260 received at least one non-value-added CT. Both the total number of CTs (median, 4; inter-quartile range (IQR), 3-5) and non-value-added CTs (median, 1; IQR, 0-1) per patient were strongly related to the disease duration (R2 = 0.566 for total CTs, R2 = 0.432 for non-value-added CTs, p < 0.001). The proportion of non-value-added CTs was potentially higher after 3 weeks from symptom onset (>35%). Conclusions: There was a high rate of repeat CTs for the COVID-19 patients, and the proportion of non-value-added CTs increased with disease duration. Follow-up CT should be avoided without clinical decline. Advances in Knowledge: As COVID-19 is impacting health care systems across the globe, we believe in our findings that serial chest CT imaging has limited clinical utility in basically stable COVID-19 patients, will help relieve some of this burden. (authors)

[en] Objective: To assess clinical application value of susceptibility weighted imaging (SWI) in cerebrovascular diseases. Method: Twenty-three patients with cerebrovascular disease were investigated, including 7 cases of cavernoma, 4 of venous hemangioma, 3 of small AVM, 1 of Sturge-Weber Syndrome, 2 of cerebral venous sinus thrombosis and 6 of chronic cerebral infarction. All patients underwent standard Mill and SWI, and most of them also underwent enhanced T₁WI and MRA. The corrected phase (CP) values were obtained at the lesions and control areas. Results: The average CP values of the lesions and the control areas were -0.112±0.032 and -0.013±0.004, respectively (t=2.167, P<0.05). In 7 cases of cavernoma, range of the lesions in SWI was larger than in T₂WI. The cavemoma could be differentiated from the hemorrhage within lesions. Moreover, multiple microcavernomas were detected on SWI. In 4 cases of venous hemangioma, SWI detected spider-like lesions with more hair-thin pulp veins adjacent to the dilated draining vein than contrast MRI. In 3 cases of small AVM, SWI was more advantageous than MRA in clearly detecting the small feeding artery. In 1 case of Sturge-Weber Syndrome, SWI demonstrated large areas of calcification and the abnormal vessels on the cerebral surface and the deep part of the cerebrum at the same time. In 2 cases of cerebral venous sinus thrombosis, the deep draining veins and superficial venous rete were generally dilated and winding, and the hemorrhagic lesions could be detected earlier than conventional MR images in one case. In 6 eases of cerebral infarction, old hemorrhage was clearly displayed within the lesions. Conclusion: SWI has more predominant advantages than conventional MRI and MRA in detecting the low-flow cerebral vascular malformations, identifying microbleeds and cerebral infarction accompanying hemorrhage, and the dilation of cerebral deep or superficial veins in patients with cerebral venous sinus thrombosis. Moreover, SWI can show the phase contrast between the lesions and the control areas. (authors)

[en] Objective: To evaluate the accuracy of MR sialography in demonstrating the main salivary duct systems by using a series of pulse sequences and stimulation of salivation by vitamin C. Methods: MR sialography was prospectively performed with STIR, heavily T₂ weighted FSE, and SS FSE sequences in 17 patients suspected with salivary duct abnormalities and 13 volunteers, respectively, and MR sialography was further performed in 16 patients after vitamin C stimulation. The results of the above three sequences were compared with each other. Results: The main salivary gland duct was depicted in all cases by any of the mentioned sequence. The STIR images were significantly superior to SS FSE and heavily T₂ weighted FSE images for demonstrating the salivary duct system, followed by heavily T₂ weighted FSE images. On STIR images, first- and second- order intraglandular branches were clearly depicted in all cases, and the thinnest branches were about 0.8 mm. On heavily T₂ weighted FSE images, the first-order and the second-order intraglandular branches were delineated in 25 of 30 and 18 of 30 cases, respectively. But on SS FSE images, only 20 to 30 first-order and 10 of 30 second-order intraglandular branches could be detected. MR sialography with vitamin C stimulation revealed the good visualization of the salivary duct system, and the ducts became wider than before. In 7 cases with acute sialadenitis, the main duct became slightly wider and the distal ducts were dilated; In 7 cases with benign tumor, the ducts were displaced but remained continuous; The duct in one patients with submandibular gland cancer showed destruction and discontinuity. The ducts of one patient with Sjogren syndrome and one with sialidosis displayed normal. Conclusion: MR sialography with evoked salivation is noninvasive and allows delineation of both normal and abnormal parotid and submandibular gland duct systems, and the images are especially better on STIR sequence

[en] Objective: To investigate the metabolic alterations in the brain of neonates with HIE and correlate those alterations with clinical grading and prognosis of HIE. Methods: Fourty-six cases of full-term neonates diagnosed as HIE clinically were performed MRI and ¹H-MRS, 9 healthy neonates without the evidence of asphyxia were studied as controls. ¹H-MRS techniques included single voxel proton MRS and two dimensional multi-voxel chemical shift spectroscopy imaging, point resolved spectroscopy sequence was used for ¹H-MRS. Metabolic changes in the spectroscopy were analyzed in neonates with HIE, and study the relationship between MRS findings and prognosis. Results: (1) The typical ¹H-MRS manifestations of full- term neonates suffering from HIE were as follows: the peaks of Lac were elevated, GLx-α were elevated and NAA were decreased. (2) GLx-α/Cr ratio in control, mild, moderate and severe HIE group was 0.16, 0.21, 0.64, and 1.31, respectively. Lac/Cr ratio in control, mild, moderate and severe HIE group was 0.12, 0.14, 0.19, and 0.26, respectively. There was a significant difference in the ratio of GLx-α and Lac/Cr between HIE group and control group (t=5.01, P<0.01; t=2.78, P<0.05), and there was a significant difference in the ratio of GLx-α and Lac/Cr between different HIE groups(F=63.29, P<0.05; F=11.74; P<0.05). Spearman rank correlation test confirmed that the ratio of GLx-α/Cr and Lac/Cr had significant positive correlation with clinical grading of HIE (r=0.76 and 0.59, P<0.01). The ratio of NAA/Cr was much lower in severe group than those in mild-moderate group. (3) Spearman rank correlation test confirmed that the ratio of GLx-α/Cr and Lac/Cr had significant negative correlation with prognosis of HIE, especially GLx-α/Cr ratio was much more correlative (r=-0.83, P<0.01), so it could be used as an effective predicter to evaluate outcome of HIE. Conclusion: ¹H-MRS is a useful tool for monitoring the brain metabolic changes noninvasively, evaluating the severity and prognosis of HIE. The higher ratio of GLx-α/Cr in basal ganglia and thalamus predicts a poor outcome in neonates with HIE. (authors)