Objective To study the effect of iterative algorithm (iDose algorithm) on image quality and radiation dose in paranasal sinus MSCT.Methods A proper cadaveric head based on the average CNR (contrast noise ratio) of paranasal sinus images in 53 patients was applied.The cadaveric head was scanned with different parameters of kV and effective mAs.The images were reconstructed with filtered back projection and iterative algorithm (iDose 1-7) respectively.The subjective and objective evaluations were performed for all the images and the optimal parameter combination was found out.Results The CNR of coronal images was slightly higher than that of axial images (t =-6.86,P ＜0.05).The image CNR of protocol (120 kV,100 mAs/slice and iDose5) was close to that of conventional protocol.The protocol of 100 kV,60 mAs/slice and iDose4 offered the images adaptable for diagnosis of inflammation.The protocol of 100 kV,80 mAs/slice and iDose4 offered the images adaptable for diagnosis of inflammation and fracture,and the radiation dose were reduced by 82％ and 75％,respectively.Conclusions Using the iDose algorithm could help to offer diagnostic images for inflammation and fracture and reduce the radiation dose in the paranasal sinus MSCT.

Objective To investigate the influence of different scout image on the radiation dose of head and chest spiral scanning in CT using automatic tube current modulation(ATCM).Methods CT scanning was performed on the head-neck and chest phantom with ATCM.Five different scout images through the five various positions that include anteroposterior(AP),posteroanterior(PA),lateral,AP,lateral,PA and lateral.The phantom was scanned three times for each position.Then each scout image was scanned by spiral technique once more.ROI in orbital center and C5 upper edge level were selected for Head and neck phantom,ROI in the apical and tracheal bifurcation level were selected for chest phantom.The contrast to noise ratio (CNR) was measured and recorded.The organ dose of eye lens and mammary glands were measured by thermoluminescent dosimeters (TLD) in every scanning(the average of 3 measurements),The cumulative value of scout image and spiral scanning were calculated.The volume CT dose index (CTDIvol) of each scan was recorded,and the cumulative value of CTDIvol was calculated.Results In the five scout images of the head-neck phantom mode,the maximum value of accumulated radiation dose of eye lens and CTDIvol appear on PA scout image(18.354 and 26.43 mGy respectively),while the minimum value appear on the lateral scout image(11.847 and 18.20 mGy respectively).In the chest phantom mode,the maximum value of the accumulated radiation dose of the mammary gland and CTDIvol emerge from the AP scout image (6.873 and 9.42 mGy respectively),while the minimum value of the mammary accumulated radiation dose appear on lateral scout image(4.592 mGy),the minimum value of CTDIvol appear on AP plus lateral scout images(3.94 mGy).The accumulated radiation dose of eye lens and CTDIvol value in PA scout image mode were 54.9％(6.507/11.847) and 45.2％(8.23/18.20) higher than those of the lateral scout image mode.The accumulated radiation dose of mammary gland and CTDIvol value in AP scout image mode were 42.5％ (2.051/4.822) and 136.7％ (5.44/3.98) higher than that of PA plus lateral scout images mode.In the head-neck phantom mode,the CNR value of orbital center and C5 upper edge level were 102.55 to 115.89,161.01 to 204.52 respectively.In the chest phantom mode,the CNR value of the apical and tracheal bifurcation level were 82.74 to 164.00,83.12 to 121.49 respectively.Conclusion The choice of the scout image had significant effect on the radiation dose and the sensitive organ dose in CT.

Objective To investigate the influence of additional filter on image quality and radiation dose in chest digital radiography (DR). Methods The adult chest phantom was exposed under the different additional filter by 0, 1.0 mm Al,1.0 mm Al+0.1 mm Cu,1.0 mm Al+0.2 mm Cu while the kV was 110 kV and the AEC parameter selection were -4,-2, 0, 2, and 4 respectively. Image quality was evaluated by the relative noise and the contrast-to-noise ratio (CNR). The radiation dose was evaluated by the entrance skin dose (ESD) and the effective dose. Linear regression analysis was used to analyze the relationship between the ESD and the effective dose, and the correlation between the image quality and the effective dose was analyzed by Pearson correlation analysis. Results The ESD were (0.023 ± 0.004), (0.034 ± 0.007),(0.045 ± 0.009),(0.056 ± 0.010),(0.067 ± 0.012)mGy and the effective dose were(6.15 ± 0.09)×10-3,(9.02±0.15)×10-3,(11.94±0.16)×10-3,(14.89±0.09)×10-3,(17.80±0.12)×10-3 mSv when the AEC parameter selection were -4,-2, 0, 2, and 4 respectively. The effective dose was linearly positively correlated with the ESD and the regression coefficient were(r=1.000, P<0.01)under different additional filter. The ESD decreased with the additional filter increased under the same AEC, and the maximum could be reduced by 34%. The relative noise was decreased with the effective dose increased and there was a negative correlation between the two and the Pearson correlation coefficient were(r=-0.970,-0.966,-0.971,-0.971;P<0.01)under different additional filter. The CNR was increased with more effective dose and there was a positive correlation between the two and the Pearson correlation coefficient were (r=0.952, 0.947, 0.908, 0.944;P<0.05)under different additional filter. The relative noise decreased with the additional filter increased under the same AEC, and the maximum could be decreased by 13%. The CNR values increased with the additional filter under the same AEC, and the maximum could be increased by 4%. Conclusions The use of additional filter in chest digital radiography can reduce the ESD and improve the quality of the image to some extent, but the effective dose change is not significant.

Purpose:To explore the value of MSCT-3D in stomatology through comparing with COPT.Materials and Methods:Both MSCT 117 patients and COPT 117 patients in stomatology were selected at a particular period,COPT imaging was using computed post-processing,MSCT imaging was processed according to 3D information through work station,then to analyze the imaging results according to metal tooth、damaged tooth and broken tooth,later to compare the photograph 、the technique of computed post-processing、the photograph condition and exposure of MSCT and COPT.Results:Normal COPT patients were 9 cases ( 0.24% ),normal teeth were 3160 (84.4% ),unusual teeth were 551 (15.6%),normal MSCT-3D patients were llcases ( 0.29% ),normal teeth were 3138 (83.8% ),and unusual teeth were 606 (16.2% ).COPT belonged to COPT photograph,the emphasis was 2D,MSCT-3D belonged to spiral photograph,the emphasis was 3D,and MSCT imaging could be processed according to 3D reformation.The 3D effect of MSCT was batter than that of COPT.The radiation dosage was much higher than that of COPT.Conclusions: COPT could get 2D effects: MSCT-3D could improve 3D results on 2D basis,but the radiation dosage of MSCT is much higher than that of COPT in stomatology.

Objective To investigate the radiation dose to the lens of patients in temporal bone CT scanning with different protocols. Methods With the same values of kV and effective mAs, the tranaxial and coronal scans of exsomatize cadaveric head was performed with conventional sequential scan mode,routine multi-slice helical scan and modified multi-slice helical scan, respectively. The values of CT volume dose index (CTDIvol) and dose length product (DLP) at various scanning mode were anylyzed, and effective doses of subject were calculated. Organ doses of the lens were measured with thermoluminescence dosimetry (TLD). Results When sequential scan mode was selected, gross effective dose was 1.21 mSv,while organ doses to lens were 50.96 and 1.73 mGy separately in axial and coronal slice scan,respectively. Effective dose was 0. 803mSv at helical scanning, while dose to lens was 40. 17 mGy. With modified helical scan mode, the effective dose was similar to routine helical scan, but dose to lens was 10.33 mGy which was significant lower than that of routine helical scan (40.17 mGy). Conclusions With the same values of kV and effective mAs, the effective doses and lens dose obtained in sequential axial and coronal scan were 1.51 times and 1.31 times higher than helical scan, respectively. With modified helical scan mode thinner slice images could be used to reformat axial, coronal and sagittal plane images, and lens dose was reduced by 74.3%. The modified helical CT scan mode of temporal bone could be selected in the clinical application.

Objective To study the impact on the radiation dose,organ doses of eye lens and thyroid and image quality with different scanning modes in head and neck CT scan.Methods The simulation phantom of head and neck was scanned by using fixed scanning condition (120 kV and 200 mAs),as well as the combinations of automatic tube current modulation (CARE Dose 4D),automatic tube voltage modulation technique (CARE kV) and partial angle scanning mode (X-CARE) respectively.Six kinds of scanning modes were adopted,including 120 kV +200 mAs,120 kV + 200 mAs + X-CARE,CARE Dose 4D + 120 kV,CARE Dose 4D + 120 kV + X-CARE,CARE Dose 4D + CARE kV,CARE Dose 4D + CARE kV + X-CARE.Two thermolumineseece dosimeters (TLDs) were exposed at the skin surface positions of eye lens and thyroid,and the values measured with two TLDs were averaged.The CT dose index volume (CTDIvol) and dose length product (DLP) for every scan were recorded,and the contrast to noise ratio (CNR) in eye lens section and thyroid section were measured.Results The crgan doses of lens and thyroid were 19.8 and 26 mGy at 120 kV and 200 mAs,as well as 13.3 and 22.2 mGv at X-CARE mode.Compared with the manual selection of 120 kV,the combination of CARE kV and CARE Dose 4D made the values of CTDIvol drop from 13.1 to 10.1 mGy,the doses of eye lens and thyroid from 16.6 and 20.8 mGy to 23.7 and 19.9 mGy respectively,while the image quality reducedsignificantly.Compared with CARE Dose 4D + 120 kV,the organ doses of eye lens and thyroid were reduced from 20.8 and 23.7 mGy to 9.6 and 15.1 mGy for with additional X-CARE,while CTDIvol dropped from 13.1 to 9.3 mGy.When the combination of CARE Dose 4D + CARE kV + X-CARE was used,CTDIvol and organ doses were reduced to a minimum,when the CNRs of head and neck were also minimized.Conclusions The scanning mode CARE Dose 4D + 120 kV + X-CARE for head and CARE Dose 4D + CARE kV for neck can effectively reduce the radiation dose while keeping good image quality.When requirements for image quality are not high,CARE Dose 4D + CARE kV + X-CARE mode can be selected to reduce the radiation dose significantly.

Objective To investigate the influence of tube voltage on image quality and radiation dosage to subjects in chest digital radiography (DR).Methods An adult chest phantom was exposed in the range of 80-130 kV with the interval of 10 kV and the automatic exposure control (AEC) setting was selected from-4 to 4.The entrance skin dose (ESD) of the phantom was measured,and the relative noise,contrast-to-noise ratio (CNR) and the effective dose of each exposure was calculated.Results The ESD was (0.062 9 ±0.027 4) mGy,and the effective dose was (0.012 7 ±0.004 5) mSv.The effective dose increased linearly with the ESD,and there was a positive correlation (r =0.912,P ＜ 0.01).When the tube voltage was held constant,the relative noise decreased as the effective dose increased (r =-0.967,-0.969,-0.968,-0.969,-0.968,-0.970,P ＜ 0.01).The CNR increased with the effective dose increasing under the same tube voltage(r =0.987,0.987,0.986,0.987,0.988,0.989,P ＜0.01).The ESD and effective dose decreased as the kV values increased under the same AEC,and the degree of decrease could be up to 50％ and 20％.The relative noise decreased as the kV values increased under the same AEC,and the degree of decrease could be up to 23％.The CNR values increased up to 8％.Conclusions The use of higher kVp in chest digital radiography can reduce the radiation dose to some extent

Objective To strengthen the scientific management of automatic processor and promote QC, based on analyzing QC management chart for automatic processor by statistical method, evaluating and interpreting the data and trend of the chart. Methods Speed, contrast, minimum density of step wedge of film strip were measured everyday and recorded on the QC chart. Mean ( ), standard deviation ( s ) and range(R) were calculated. The data and the working trend were evaluated and interpreted for management decisions. Results Using relative frequency distribution curve constructed by measured data, we can judge whether it is a symmetric bell shaped curve or not. If not, it indicates a few extremes overstepping control limits possibly are pulling the curve to the left or right. If it is a normal distribution, standard deviation( s ) is observed. When ?2s lies in upper and lower control limits of relative performance indexes, it indicates the processor works in stable status in this period. Conclusion Guided by statistical method, QC work becomes more scientific and quantified. We can deepen understanding and application of the trend chart, and improve the quality management to a new step.

Objective:To explore the effects of scout scanning parameters (projection angle and tube potential) on image quality and radiation dose in chest CT and to provide guidance for the selection of scanning parameters in clinical practice.Methods:Different parameter combinations were selected to acquire the scout view of the anthropomorphic adult chest phantom. Fifteen scout views were obtained under parameter combinations of the projection angle (0/90/180 degrees), tube potential (70/80/100/120/140 kV) and tube current (25 mA). And then, chest spiral scans were performed according to the scout views. The other parameters were Assist kV, smart mA (maximum range), 80 mm detector width, 0.992∶1 pitch, 0.5 s rotation time, 330 mm scanning length, 5 mm thickness, NI (noise index) 10. The radiation dose modulation index (ASiR-V) was 30%, and the iterative level was 50%. Volume CT dose index (CTDI vol) and tube current at 4 body levels (pulmonary apex, trachea bifurcation, mammary level and diaphragmatic dome) were recorded. The thermoluminescent dosimeters (TLDs) were used to measure the organ dose of the breast glandular. Regions of interest (ROIs)were selected at the trachea bifurcation and diaphragmatic dome to calculate the contrast noise ratio (CNR). Results:The tube potential of the spiral scanning was automatically selected as 80 kV when the projection angle was 0 degree. The changing of the tube potential for the scout had little influence on the tube current at the four body levels, and the variation range was 0-2% (5/230). The tube potential in the spiral scanning was automatically selected as 100 kV when the projection angles were 90 and 180 degrees. The changing of the tube potential for the scout had a great influence on the tube current at the slice of trachea bifurcation and the variation range was from 14%(29/210)to 44%(93/210). According to the angle projection, there were statistical differences in CTDI vol( P< 0.017), organ dose of the breast glandular, and CNR at the slices of trachea bifurcation and at diaphragmatic dome ( F=13.027, 24.727, 10.630, P< 0.05). According to the tube potential in the scout scanning, there were no significant differences in CTDI vol, organ dose of the breast glandular and CNR at both levels ( P> 0.05). Conclusions:In chest CT, the influence of the projection angle in scout scanning on the image quality and radiation dose was more significant than that of the tube potential.

Objective To explore the effects on image quality and dose reduction to the lens when using bismuth shielding in head and neck MSCT.Methods The standard phantom and the cadaveric head with none,1,2 and 3 layers of bismuth shielding were scanned with protocols of brain,temporal bone and paranasal sinuses using a 16-MDCT scanner.The organ dose to the lens in each scanning was measured with thermoluminescence dosimeters(TLD).The above scanning with sinus protocol was repeated with a sponge with thickness of 5,10,15 and 20 mm placed between the shielding and phantom/head.The CT attenuation of phantom with the distance of 2,4,6 and 8 cm to shielding were measured.The image quality was subjectively evaluated by 2 physicians.Results The organ doses of the lens with protocols of brain,temporal bone and sinuses were 24.31,27.60 and 20.01 mGy,respectively.The doses were decreased significantly when using bismuth shielding.With the increase of the shield gap,the degree of dose reduction was reduced,but the increasing degree of CT attenuation significantly reduced.Using 2-layer and 3-layer bismuth shield in brain and temporal bone CT scan,the radiation doses were reduced by 47.1％ and 59.1％,respectively while maintaining the diagnostic image quality.Using 1-layer shield without gap and 2-layer shield with 1.5 cm gap in sinus CT,the radiation doses were reduced by 31.5％ and 34.5％,respectively.Conclusions Reasonable usage of bismuth shielding can effectively reduce the radiation dose to the lens of eye in head and neck MSCT.