| Background and purposeOsteosarcoma is a primary malignant tumour of the skeleton characterised by the direct formation of immature bone or osteoid tissue by the tumour cells. It is most frequent malignant tumour occurred in childhood and adolescence, and it is the most common primary malignant tumour besides multiple myeloma. The most common site occurs around the knee. There are no typical clinical symptoms at the early stage, and it is extremely confused with trauma and growing pain. Ostosarcoma shows high proliferation. What is more, it grows invasively at local site and pulmonary metastases easily occur at early stage. With the development and improvement of tumor treatment, the cure rate of osteosarcoma has been enhanced from10%to60%-70%. Hence, early detection, early diagnosis and early treatment of are considered to be vitally important. As the osteosarcoma of different materials in, take different tumor location, pathology results obtained may be essentially different. Imaging examination of osteosarcoma has its clinical value in the early diagnosis, preoperative staging, and observation treatment result. With the demands of imaging in clinical studies, the new MRI imaging technology and MRI molecular imaging are continuously introduced to musculoskeletal system disease research. This study is to analyze osteosarcoma diffusion weighted imaging (DWI), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and magnetic resonance spectroscopy(MRS) to explore the clinical diagnosis and differential diagnosis of that.Materials and methods41patients with Osteosarcoma were recruited from December2008to Decemeber2011in the First Affilicated Hospital of Zhengzhou University. Any diagnosis methods, which may affect the results of imaging detections, including pathology detection, radiology detection, concurrent Chemoradiotherapy, et al, were not performed for all cases before MRI examination, and then the examinations of surgical resection or biopsy pathology were done to make a definite diagnosis on osteosarcoma within one week. All of patients had a series of routine examination, including MRI plain scan, MR-DCE and MR-DWI,29males and12females were involved, with the mean age18.90±10.8years (range7to72years). MRS was performed for18cases, with average age14.77±4.8years (range7to24years).Magnetic resonance instrument of the Siemens Magnetom Trio Tim3.0T MRI was used to do examinations. Firstly, do MRI plain scan, followed by five different sets of sensitive diffusion coefficient (b value:unit s/mm) DWI sequences, the DCE-MRI, conventional enhanced scan and finally MRS. DWI sequences were taken with b0,400,800,1000and1500respectively, obtaining the corresponding apparent diffusion coefficient (apparent diffusion coefficient, the ADC) map; then regions of interest were selected to measure the ADC values (103mm/s), with a comparison with both the adjacent normal muscle and bone marrow, which was regarded as a reference. The contrast agent Magnevist (Gd-DTPA) was used to the dynamic enhancement,with a dose0.2mmol/kg, injecting at a speed of2.5ml/s; before injection collecting one phase image as the original chips, then started injecting while scanning and collecting images of18phases in all. Using the Mean Curve software of workstation, the Time-signal intensity curve (TIC) of the lesion parenchyma, adjacent muscles and the same level of arteries, measurement of indicators such as TIC type, Slope and Rrim-center would be obtained. The most obvious enhancement and the most homogeneous signal lesions of the parenchyma on the conventional enhanced scan image were chosen as the volume of interest,1H-MRS was performed by using point-resolved spectroscopy sequence。 analyzed by Spectroscopy Software, with the measurement indicators of Cho,Lip,Cho/Cr and Lip/Cr.The statistical software of SPSS17.0was used for data analysis, all statistical results in inter-quartile range P25～P75.The analysis of the ADC values and Cho/Cr values of high and low-grade osteosarcoma was performed by the test of two independent samples rank sum; moreover, rank sum test of a number of independent samples was used to compare the enhance parameters of three different curve types; it is significantly different if P value of all the data was smaller than0.05.ResultsWhen b values of DWI sequences were400,800,1000and1500s/mm2, though the ADC values of highly malignant osteosarcoma parenchyma were lower than that of the low-grade one, the ADC values of osteosarcoma parenchyma was far greater than that normal bone marrow; There was a negative correlation on ADC value between osteosarcoma and the normal bone marrow, that is, the ADC values decreased with b values increasing. When b value were400,800,1000s/mm2, there were significantly statistical difference on ADC values between the high group and low-grade malignant osteosarcoma group, but while b=1500s/mm2, no statistically significant difference was found between both groups; The ROC curve area under different b values were0.754,0.737,0.659and0.605, the95%confidence interval for mean were (0.679,0.829),(0.629,0.844),(0.541,0.778),(0.483,0.727); for different b values corresponding ADC values were1.003x103mm2/s (b=400s/mm2),1.101×10-3mm2/s (b=800s/mm2),1.155×10-3mm2/s(b=1000s/mm2) and0.948×10-3mm2/s (b=1500s/mm2), and the sensitivity and specificity diagnosis of diagnosis were75.6%and60.2%respectively;65.9%and65.9%;61.0%and63.4%;61.0%and51.2%.(2) For dynamic contrast-enhanced TIC type,11cases were low-grade osteosarcoma of41cases of patients with osteosarcoma, accounting for26.8%, showing that type Ⅰ and type Ⅱ and type Ⅲ curves, respectively2,5and4cases; therefore, The other30cases were highly malignant osteosarcoma, accounting for73.2%, with only visible type Ⅰ and type Ⅱ curves, respectively20and10cases. For the TIC distribution It is showed that there is no statistical significance between high and low grade osteosarcoma groups.(3) It was statistically significant in dynamic enhancement parameters according to the degree of malignancy of osteosarcoma, with low grade osteosarcoma the95%confidence interval for mean of Slope is (10.74,21.40)%/s, Rrim-center is (0.287,0.428), and highly malignan osteosarcoma tumor the95%confidence interval for mean of slope (28.950,60.425)%/s, Rrim-the center is (0.574,0.836). Distribution types were classified in accordance with the TIC type of osteosarcoma, with type I curve P25～P75of Slope is (30.925,78.200)%/s, Rrim-center (0.571,0.858), type II curve P25～P75of Slope is (6.55,11.685)%/s, Rrim-center (0.377,0.654), and III curve P25～P75of Slope is (6.55,11.685), Rrim-center is (0.173,0.380), moreover, it was showed that statistically significant difference was discovered in types Slope and Rrim-center during the three curve; Furthermore, by pair-wise comparison during the three curves, there was a statistically significant difference in dynamic enhancement parameters.(4) The P25-P75of Cho/Cr values of high and low grade malignant osteosarcoma were (2.703,4.883)、(1.045,2.695)(Z:-2.445, P:0.014),and P value was smaller than0.05, indicating Cho/Cr ratio between high and low-grade malignant osteosarcoma were significant statistical difference. As a diagnostic indicator of Cho/Cr, the best diagnostic cut-off of which was2.3, the area under the ROC curve was0.718, the95%confidence interval for mean is (0.549,0.886), with a sensitivity of72.2%and specificity66.7%.Conclusions(1)DWI was helpful in distinguishing high grade osteosarcoma and low grade osteosarcoma. Therefore, b=400s/mm2was recommended to be the proper b value for the differential diagnosis of osteosarcoma.(2) Type I curve can refer to high grade osteosarcoma; type III curve can point out low grade osteosarcoma. (3)1H-MRS could indicate the grading of malignant osteosarcoma; Cho/Cr=2.3could be used to decide high grade malignant osteosrcoma and low grade osteosarcoma. |
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