| PART 1Comparative study of the thoracic structures imaging between dual energy subtraction and conventional digital radiographyObjective: To research the value of dual energy subtraction (DES) in displaying thoracic structures. Methods: 100 consecutive cases of DES and conventional digital radiography (CDR) were analyzed by 3 radiologists in three aspects including lung markings, airway, thoracic bones. Pearson Chi—square analysis was made by SPSS 11.5 software. Results: DES excelled CDR in manifesting lung markings in the inner and central sections of lung field, trachea, right main bronchus, opening of right upper lobar bronchus, middle bronchus, opening of left upper lobar bronchus, ribs in lung field (P<0.05). CDR surpassed DES in displaying lung markings in the outer section of lung field, lung markings behind heart and diaphragm, left main bronchus, left lower lobar bronchus, ribs behind heart and diaphragm, thoracic spine, clavicles, scapulas (P<0.05). DES displaying performance of lung markings in the outer sections of lower lung field in male surpassed that in female (P<0.05) . There was no significant difference between DES and CDR in manifesting ribs in axilla (P>0.05). Conclusion: Thoracic soft tissue and bones could be observed seperately by DES. DES was complementary to CDR in manifesting thoracic structures. PART 2Analysis of motion artifact in thoracic dual energy subtraction and discussion of countermeasureObjective: The objective of this study was to analyze the motion artifact (MA) of dual energy subtraction (DES) . The countermeasure of MA was also discussed. Methods: The MA of 211 consecutive DES cases were analyzed by 3 radiologists on MA manifestation, MA position,MA extent,MA origin and image satisfaction. Results: MA was manifested as black or white stripes on the borders of structure in direction of movement. The normal structures and lesions were distorted by MA.But the borders of structures were often depicted more clearly by slight MA.The positions in which MA was most easy to be found included the inner sections of bilateral middle and lower lung fields, the central sections of bilateral lower lung fields, the central section of left middle lung field, the borders of heart, the borders of diaphragm, the borders of osseous thorax. Severe MA was most likely to be found on left lower border of heart. MA caused by heart beating was observed in all cases. Respiration movement and chest shift respectively bring MA in 91% and 6.2% cases. Image satisfaction of excellent lever, good lever,middle lever and bad lever were 8. 1%, 44. 5%, 27.5%,19.9% respectively. Image satisfaction of middle lever and better account for 80. 1% cases. Conclusion: MA was an important factor affecting DES image quality. The dominating origins of MA were heart beating and respiration movement. Reducing MA would benefit improving image quality. PART 3Experimental study of dual energy subtraction and conventional digital radiography in detecting signals.Objective To compare the performance of dual energy subtraction (DES) with that of conventional digital radiography (CDR) in detecting experimental signals. The influence of signal noise ratio decreasing on DES detecting signal was analyzed. Materials and Methods 200 plastic balls which were 4 mm in diameter were taken as signals and were placed on a 10 cm thick plastic board. The signals were examined by DES and CDR and were estimated by 3 radiologists with 5-value-differentiation method. ROC curve analysis was made by ROCKIT software. Results ROC curve analysis indicated that there was no significant difference (P=0. 4851>0.05, two-tailed) between the area under the ROC curves(Az) of the two methods (Az=0.9931 for CDR , Az=0. 9879 for DES). Conclusion Though signal intensity might somewhat decrease and image noise might increase after digital subtraction calculating in DES, there was no significant difference between DES and CDR in detecting signals. The influence of signal noise ratio decreasing was limited.PART 4Experimental study of dual energy subtraction and conventional digital radiography in detecting simulated pulmonary nodulesObjective: To compare the performance of dual energy subtraction (DES) with that of conventional digital radiography (CDR) in detecting simulated pulmonary nodules (SPNs) . Materials and Methods: 200 plastic balls which were 4 mm in diameter were taken as SPNs and were placed on the right upper thorax of a healthy volunteer. The SPNs were examined by DES and CDR and were estimated by 3 radiologists with 5-value-differentiation method. ROC curve analysis was made by ROCKIT software. The sensitivity, specificity , predictive value of positive test , predictive value of negative test, accuracy of detecting SPNs were also calculated and were analyzed by Pearson Chi-square Test. Results: The difference was significant (P=0.0002<0.05 , two-tailed) between the area under the ROC curves(Az) of CDR and DES (Az=0. 7276 for CDR , Az=0.8561 for DES). The sensitivity, predictive value of negative test, accuracy of detecting SPNs were 69. 3%, 73. 9%, 77. 9% respectively in DES those were 52. 8%, 63.9%,70.0% respectively in CDR, DES excelled CDR with significant difference (P<0.05) . The specificity , predictive value of positive test of detecting SPNs were 86.4%,83.6% respectively in DES , those were 83. 1%,75.6% respectively in CDR. DES was close to CDR (P >0. 05) .Conclusion: DES surpasses CDR in detecting SPNs without superposition of ribs. There is a good outlook for the application of DES in small pulmonary nodules screening.PART 5Comparative Study of Detecting Pulmonary Nodules Between Dual Energy Subtraction and Conventional Digital RadiographyObjective : To compare the detectability of dual energy subtraction (DES) with that of conventional digital radiography (CDR) in detecting pulmonary nodules(PNs). Materials and Methods: 104 PNs of 50 patients which were demonstrated by CT were examined by DES and CDR. The detectability of DES and CDR were estimated by 3 radiologists. McNemar Test was made by SPSS 11.5 software. Results: For the total PNs, the detectability of DES was 67.3% (70/104) and that of CDR was 52.9% (55/104), there was significant difference between the two methods (X~2 = 9.33 , P= 0.00K0.05) . For the PNs which maximal diameter were 1 cm or less, the detectability of DES and CDR were 47.4% (27/57) and 22.8% (13/57) respectively, there was significant difference between the two methods , (X~2 =8. 45, P=0.003<0.05). For the PNs which maximal diameter were larger than 1 cm , the detectability of DES and CDR were 91.5% (43/47) and 89.4% (42/47) respectively, there was no significant difference between the two methods(X~2 =1.00 ,P=1.00>0.05) . Conclusion: Without superposition of ribs,the performance of DES was superior to that of CDR in detecting PNs, especially in small PNs.PART 6Comparative Study of Diagnosing Pulmonary Diseases Between Dual Energy Subtraction and Conventional Digital RadiographyObjective: To research the value of dual energy subtraction (DES) in diagnosing pulmonary diseases. Materials and Methods : 82 patients were examinated by DES and conventional digital radiography (CDR) . With CT control, the displaying performance of DES was compared with that of CDR by 3 radiologists on diagnosing pulmonary diseases and signs. Pearson Chi—square analysis was made by SPSS 11. 5 software. Results: To the total 122 pulmonary diseases of 82 patients, the better displaying performance (BDP) was 82. 8% in DES and that was 17.2% in CDR, there was significant difference between the two methods (X~2 =104. 918, P=0.000<0.05). DES surpassed CDR in diagnosing nudule and tumor (P<0.05), inflammationary exudation and consolidation (P<0.05) and tuberculosis (P<0.05). DES surpassed GDR in manifesting notched signs of nudule and tumor (P<0.05); whereas, DES was close to CDR in displaying spiculate signs of nudule and tumor (P>0.05). The BDP of DES was 90% (18/20) in detecting calcified lesions of tuberculosis. According to statistic analysis, the BDP of DES in diagnosing tuberculosis surpassed that in diagnosing inflammationary exudation and consolidation (P<0.05); the BDP of DES in diagnosing tuberculosis surpassed that in diagnosing nudule and tumor (P< 0.05) ;whereas, the BDP of DES in diagnosing inflammationary exudation and consolidation was close to that in diagnosing nudule and tumor (P>0.05). Conclusion: DES was a valuable method in diagnosing pulmonary diseases. DES was complementary to CDR.PART 7Comparative Study of Diagnosing Rib Fracture Between Dual Energy Subtraction and Conventional Digital RadiographyObjective: To research the value of dual energy subtraction (DES) in diagnosing rib fracture( RF) . Materials and Methods: 121 RFs of 40 patients were examinated by DES and conventional digital radiography (CDR) . The displaying performance of DES was compared with that of CDR by 3 radiologists on manifesting RFs in different stage, signs of fracture and complications. Pearson Chi —square analysis was made by SPSS 11. 5 software. Results: To the total RFs, the better displaying performance was 81.0% in DES and that was 17.4% in CDR, there was significant difference between the two methods (X~2 =98.027, P=0.000<0.05) . DES surpassed CDR in manifesting healing RFs and healed RFs. There was significant difference between the two methods (P=0.000<0.05) . There was no significant difference between the two methods in manifesting acute RFs (P=0.151>0.05) . The performance of DES was superior to that of CDR in displaying signs of rib deformity and callus, significant difference was found between the two methods (P=0.000 <0.05) . There was no significant difference between the two methods in manifesting signs of fracture line (P=0. 431>0.05). DES excelled CDR in manifesting 15/17 (88.2%) complications. Conclusion: DES was a valuable method in diagnosing RFs. DES was complementary to CDR.
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