OBJECTIVETo compare five materials commonly used in dentistry, including three types of metals and two types of ceramics, by using different sequences of three magnetic resonance imaging (MRI) field strengths (0.35, 1.5, and 3.0 T).

METHODSThree types of metals and two types of ceramics that were fabricated into the same size and thickness as an incisor crown were placed in a plastic tank filled with saline. The crowns were scanned using an magnetic resonance (MR) machine at 0.35, 1.5, and 3.0 T field strengths. The TlWI and T2WI images were obtained. The differences of various materials in different artifacts of field MR scans were determined.

RESULTSThe zirconia crown presented no significant artifacts when scanned under the three types of MRI field strengths. The artifacts of casting ceramic were minimal. All dental precious metal alloys, nickel-chromium alloy dental porcelain, and cobalt-chromium ceramic alloy showed varying degrees of artifacts under the three MRI field strengths.

CONCLUSIONZirconia and casting ceramics present almost no or faint artifacts. By contrast, precious metal alloys, nickel-chromium alloy dental porcelain and cobalt-chromium ceramic alloy display MRI artifacts. The artifact area increase with increasing magnetic field.

Artifacts ; Ceramics ; Chromium Alloys ; Crowns ; Dental Alloys ; Dental Materials ; Dental Porcelain ; Magnetic Fields ; Magnetic Resonance Imaging ; Zirconium

The 2017 Annual Meeting of the American Society of Clinical Oncology (ASCO) was held on June 2-6,2017 in Chicago,United States.And the academic event showed the frontier researches in the field of oncology.Survival prediction in patients treated by FOLFIRI regimen and bevacizumab for metastatic colorectal cancer using radiomics approach was made in Abstract 3601.Authors aim to summarize the application and development of radiomics in digestive system tumors.

Objective To evaluate the CT findings and diagnostic value of splenic lymphoma.Methods 15 cases of splenic lymphoma proved by clinical or pathohistological evidence and examined with plain and enhanced CT scans were retrospectively analyzed with literature reviewed.Results Of 15 cases of splenic lymphoma,The CT findings of splenic lymphoma included:5 cases of Solitary pattern displayed as a uniform density,solitary lesion in the liver with mildle uniform enhancement or peripheral enhancement;8 cases of multiple nodular patterndemonstrated multiple,round-like or lobular lesions with uniform density(in most lesions) with clear margin,and with mildle uniformenhancement or peripheral enhancement after contrast medium administration;2 cases of diffuse pattern showed diffuse enlargement of thespleen with hypodensity or miliary low-density foci.Of 15 cases of hepatic lymphoma,the lesion extended out of spleen in 9 cases.Conclusion The CT findings of splenic lymphoma are of certain characteristics,the presence of abdominal lymphoma is also helpful tosuggest the diagnosis.

Objective　To assess the CT manifestations and diagnostic value in the pancreatic tuberculosis(PTB)with review of the literatures. Methods　All cases of PTB proved by surgery or biopsy were examined with plain and enhanced CT scans. Results　The CT findings in one case with multiple-nodular type of PTB were diffuse enlargement of the pancreas with multiple, nodular, and low-density lesions; The nodular lesions had peripheral enhancement. 7 cases of local type of PTB encroached on pancreatic head. 4 cases showed local soft tissue masses with multiple flecked calcifications in 2 cases and mild enhancement in one case; Cystic masses was found in 2 cases, with mural calcification in 1 case and multiloculated cystic mass in 1 case, respectively; Massive pancreatic head calcification was demonstrated in one case. In these 8 cases of PTB, the lesion extended out of pancreas in 4 cases, including abdominal tuberculous lymph nodes, tuberculous peritonitis, and hepatosplenic tuberculosis. Conclusion　CT findings of PTB were various but had some characteristics. Pancreatic masses with multiple flecked calcification or mild enhancement could suggest the diagnosis. Abdominal tuberculosis accompanied with the pancreatic lesion, especially tuberculous lymph nodes, was highly suggestive of the diagnosis of PTB.

To summarize the imaging characteristic of parotid lymphoepithelial carcinoma (LEC) by retrospective analyses of computed tomography (CT) and magnetic resonance imaging (MRI) findings for 6 cases of parotid LEC confirmed by operation and pathology and review the relevant literatures.All lesions were located in unilateral parotid.There were single (n =5) and multi-module fusion (n =1).All were located in superficial lobe of parotid gland.And deep lobe (3/6) was involved.An infiltration of casting shape was found along superficial parotid (4/6).There was an irregular margin with small spines,uniform density and signal and above moderate enhancement.An infiltration of casting shape along superficial lobe,uniform density and signal and rich blood supply suggest a diagnosis of LEC.

Objective To study the application of multidector spiral CT(MSCT) in the diagnosis of pulmonary embolism(PE).Methods The clinical and MSCTPA data of 15 cases with suspected PE were analyzed retrospectively.Results Of 15 cases,14 cases(93.3%)were diagnosed as PE.849 branches(82%) of pulmonary arteries were showed in 1035 branches.PE was detected in 130 branches(15.3%) of 849 branches of pulmonary arteries.438 branches(73%) were showed in 600 branches of subsegmental pulmonary arteries,PE was showed in 43 branches(9.8%)of 438 branches.Direct signs of PE included central filling defect in 3 cases;eccentric filling defect(n=9);embolism attached to the wall of host artery(n=2) and total occlusion of the pulmonary arteries(n=3).Indirect signs includedmosaic sign in 1 case;subpleural infarction(n=3);pulmonary hypertension(n=5);Westermark sign(n=8) and pleural effusion(n=6).Conclusion MSCTPA is a fast,effective,security and non-invasive diagnostic method for PE,it may replace the pulmonaryangiography and will be the first choice for diagnosis of PE.

Objective To assess CT, MR manifestations and diagnostic value in hepatic tuberculosis. Methods CT findings in 12 cases and MR findings in 4 cases with hepatic tuberculosis proved by surgery or biopsy were retrospectively analyzed. Results (1) CT findings: one case of serohepatic type of hepatic tuberculosis was multiple nodular lesions in the subcapsule of liver. Parenchymal type were in 10 cases, including multiple,miliary, micronodular and low density lesions with miliary calcifications in 2 cases, singular, low density mass with multiple flecked calcifications in 3 cases, multiple cystic lesions in 1 case, multiple micronodular and low density lesions fusing into multiloculated cystic mass or “cluster” sign in 3 cases, and singular, macronodular and low density lesion with multiple miliary calcifications in 1 case. One case of tuberculous cholangitis showed marked dilated intrahepatic duct with multiple flecked calcifications in the porta hepatis. (2) MR findings in 4 cases were hypointense on both T 1WI and T 2WI in one case, hypointense on T 1WI and hyperintense on T 2WI in 3 cases. Enhanced MR in 3 cases showed slightly peripheral enhancement or with multilocular enhancement. Conclusions Various types of hepatic tuberculosis had their different imaging findings. The typical CT and MR findings could suggest the diagnosis.

Objective To assess the imaging and clinical manifestations of gastrointestinal mucosa associated lymphoid tissue(MALT)lymphoma with review of literatures. Methods Six cases of gastrointestinal MALT lymphoma (4 in stomach and 2 in intestine) proved by surgery and biopsy were examined with gastrointestinal barium meal examination (GI), CT or MRI scans. Results Gastrointestinal MALT lymphoma was an indolent disease that patients had a slow natural course, a high response rate to treatment and a long survival. Most cases of gastrointestinal MALT lymphoma had associated with Helicobacter pylori. GI showed thickened folds, multiple mucosal nodularity or polypoid filling defects, multiple point ulcers, and enlarged areae gastricae. CT and MRI revealed diffuse gastrointestinal wall thickening, polypoid lesion, and abdominal lymphadenopathy.Two or more findings and multiplicity of lesions might be the most important imaging features. Conclusions Based on the typical imaging findings combined with clinical characteristics, gastrointestinal MALT lymphoma could be suggested.

Objective To evaluate chest CT features of microscopic polyangiitis(MPA).Methods Clinical data and chest CT images of 66 patients diagnosed as MAP had been collected.Depending on clinical manifestations.the 66 cases were divided into the active group and the stable group.The data of two groups were analyzed by x2 test.Results Forty-three of 66(65.2%)CT images were abnormal including 32 of them in active group and 11 in stable group. In these patients,CT images showed ground glass opacities(53.5%),lung consolidations(23.2%),scattered patchy opacities(44.2%),ground glass opacities and/or lung consolidations(76.7%),reticular opacities(65.1%),honeycomb(14.0%),pleural effusions(48.8%),emphysema(18.6%),and mediastinal adenopathies(58.1%).Lung consolidations,ground glass opacities,scattered patchy opacities,mediastinal adenopathies,and pleural effusion in the active group are more common than that in the stable group(X2=4.479,4.083,4.053,9.697,9.345 respectively,P<0.05).Conclusion Chest CT features of in patients with MPA have difference between active and stable periods.The chest CT scan is a useful tool to diagnose MAP in different periods and guide the treatment.

Objective To analyze CT features of xanthogranulomatous cholecystitis(XGC)so that to improve the accuracy of diagnosis.Methods The data of CT,clinic and operation in 11 cases with XGC proved pathologically were analysed.The following CT features were analyzed:the cholecystic wall thickness,intramural hypoattenuated nodules,inner wall,mucosal line,patterns of enhancement of thickened wall,involved liver tissue and the presence of stones.The changes around the gallbladder were also noticed.Results The gallbladder wall was thickened and intramural hypoattenuated nodules were seen in all patients.The inner wall of gallbladder was smooth in 9 patients,the mucosal line was observed in 6 cases,the size of gallbladder was enlarged in 3 while 4 gallbladders were smaller than normal.Stones were found in 4 gallbladders.There were hepatic involvement in 6,pericholecystic infiltration in 3 and dilatation of biliary tract in 6 cases.Conclusion CT features of thickened gallbladder wall with intramural hypoattenuated nodules(sandwich sign)and continuous mucosal line were characteristic of XGC.