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Objective:To explore the effects of tube voltage on the image quality and radiation dose of paranasal sinus CT on a 16 cm wide-detector CT.Methods:The sinus area of head specimen was scanned with sequential scanning mode and tube voltages of 70, 80, 100, 120 and 140 kV, respectively. The parameters were set as follows: NI=9, automatic tube current modulation, Smart mA with the maximum range at the corresponding tube voltage, 120 mm detector width. The images were reconstructed with bone and soft tissue algorithms separately.The slice thickness was 0.625 mm for all reconstructed images. The axial, coronal and sagittal images were reformatted as 2 mm thickness with clinical baseline. The CT value and standard deviation (SD) were measured in the region of interest(ROI) of central axial image and the contrast-to-noise ratio (CNR) was calculated. The volume CT dose index(CTDI vol) and dose length product (DLP) were recorded, and the figure of merit (FOM) of images was computed. The images obtained in the study were subjectively evaluated by two experienced radiologists and one technician using a five-point scoring system. Results:The subjective evaluation of images obtained in the study met the diagnostic requirements. With the reconstruction of bone algorithm, the CNR at the tube voltages of 100 and 80 kV were 66.98 and 64.75, respectively, which was significantly higher than those at the tube voltages of 70, 120 and 140 kV (51.61, 61.56 and 57.76, respectively). The maximum and minimum CTDI vol were 34.11 mGy at 140 kV and 17.45 mGy at 70 kV. The FOM value was 152.26 at 100 kV. With the reconstruction of soft tissue algorithm, the maximum CNR was 195.62 at 80 kV, which was markedly greater than those at 70, 100, 120 kV and 140 kV (139.46, 154.49, 148.06 and 155.58 respectively). The maximum FOM value was 1273.56 at 80 kV, which was significantly higher than those at the tube voltages of 70, 100, 120 kV and 140 kV (1114.56, 809.98, 735.63 and 709.62, respectively). Conclusions:For the sinus CT of head specimen, the scan protocols with 100 kV combined with bone reconstruction algorithm and 80 kV combined with soft tissue reconstruction algorithm can provide relatively lower radiation dose and good image quality.
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Objective:To investigate the effect of organ dose modulation (ODM) technique on reducing the breast radiation dose in chest CT scanning.Methods:In the phantom test, the PBU-2 adult chest module was used. The clinical chest scan protocol was used and three sets of scans performed on the chest module： (1) ODM off group, ODM was not used; (2) ODM part group, ODM was applied only in the breast region； (3) ODM all group, ODM was applied in the whole scan scope. Other scan parameters were same for the three groups, with smart mA applied. The volume CT dose index (CTDI vol) was recorded for all three groups. A long rod ionization chamber was placed in a fixed position in front of the right breast area to measure the breast skin dose (D). The contrast noise ratio (CNR) and the figure of merit (FOM) were measured respectively. In clinical research, 72 female patients who underwent chest CT scanning in Beijing Tongren Hospital Capital Medical University from August to November 2018 were retrospectively recruited. According to the application of ODM, the patients were divided into ODM off group (without ODM, 36 cases) and ODM part group (ODM applied in the breast region, 36 cases). The CTDI vol and the dose length product (DLP) were recorded. CNR, noise of images were measured and calculated, respectively. The image quality was evaluated by subjective evaluation scores. The one way ANOVA analysis was used in comparing the difference of CNR among the 3 groups in module test. As for clinical cases, the independent samples t test was used to compare the difference in CTDI vol, DLP, CNR and the noise between two groups; and the rank-sum test was used for comparison in image quality subjective evaluation. Results:In module test, the radiation dose was highest in ODM off group, and lowest in ODM all group. The CTDI vol were (6.90±0.02), (6.26±0.02) and (5.99±0.02) mGy, and the D values were (9.17±1.01), (8.01±0.92) and (7.58±0.87) mGy for ODM off group, ODM part group and ODM all group respectively. The CNR values of images with soft tissue algorithm reconstruction were highest in ODM off group and lowest in ODM all group, while no statistically significant difference was displayed ( P>0.05). The CNR values of the images with lung algorithm reconstruction showed the same trend, with statistically significant difference among the three groups ( F=154.732, P=0.006). The FOM of the lung and soft tissue algorithm images was maximized when the ODM was partially applied. As for clinical cases, compared with ODM off group, the dose of ODM part group showed significantly decreased, with CTDI vol decreased by 16.12% ( t=2.604, P=0.011), and the DLP decreased by 16.85% ( t=3.293, P=0.002). No significant difference was found in CNR, noise and subjective score by two doctors between two groups ( P>0.05). Conclusion:The application of ODM in chest CT imaging can reduce the radiation dose of breast with simultaneously maintaining the image quality.
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Objective:To explore the effect of pre- and post-adaptive statistical iterative reconstruction-Veo (ASiR-V) on image quality and radiation dose in paranasal sinus CT, and to find the best combinations.Methods:One head specimen was scanned with the routine spiral CT scanning parameters [noise index (NI)=8] and different levels of pre-ASiR-V (0—100%, with an interval of 10%). The images were reconstructed with different post-ASiR-V (0—100%, with an interval of 10%) for the bone algorithm and standard algorithm. All of 242 thin-layer images of paranasal sinuses were obtained. The region of interest (ROI) was selected to measure the CT value to calculate the contrast to noise ratio (CNR) and figure of merit (FOM). The volume CT dose index (CTDI vol) and Smart mA were recorded. The linear regression was conducted to analyze the relationship between CTDI vol, SmartmA, CNR and FOM. And with the same pose-ASiR-V level, the CNR of images which reconstructed by bone and soft algorithms were compared with pair-wise t test. The image quality was subjectively evaluated by three independent experienced radiologists using a 4-point scale (4 was the best). Results:As the pre-ASiR-V levels (0—100%) increased, Smart mA and CTDI vol were reduced with a linear negative correlation ( r=-0.981, -0.976, both P<0.001). The Smart mA decreased by 72.05% and CTDI vol by 71.22%. Keeping the same pre-ASiR-V level,the CNR increased with the increase of post-ASiR-V level (for the bone algorithm images: R2=0.976, 0.992, 0.982, 0.982, 0.975, 0.975, 0.979, 0.996, 0.952, 0.978, 0.965;for the standard algorithm images: R2=0.944, 0.990, 0.988, 0.993, 0.996, 0.987, 0.984, 0.996, 0.996, 0.990, 0.965).Under the same level of post-ASiR-V, the CNR and FOM fluctuated with the pre-ASiR-V level (for the bone algorithm images: R2=0.335, 0.341, 0.344, 0.364, 0.385, 0.405, 0.418, 0.429, 0.455, 0.474, 0.516; for the standard algorithm images: R2=0.223, 0.278, 0.327, 0.285, 0.309, 0.329, 0.325, 0.346, 0.360, 0.390, 0.380). All subjective image quality could meet the diagnostic requirements (the score≥3). Conclusion:At NI=8, for the bone algorithm, the best combination is 80% pre-ASiR-V and 100% post-ASiR-V; for the standard algorithm, the best iteration combination is 100% and 100%. The appropriate choice of pre- and post-ASiR-V levels in paranasal sinus CT scan can effectively reduce the radiation dose under the premise of maintaining the image quality that meets the diagnostic needs.
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Objective@#To explore the effect of pre- and post-adaptive statistical iterative reconstruction-Veo (ASiR-V) on image quality and radiation dose in paranasal sinus CT, and to find the best combinations.@*Methods@#One head specimen was scanned with the routine spiral CT scanning parameters [noise index (NI)=8] and different levels of pre-ASiR-V (0—100%, with an interval of 10%). The images were reconstructed with different post-ASiR-V (0—100%, with an interval of 10%) for the bone algorithm and standard algorithm. All of 242 thin-layer images of paranasal sinuses were obtained. The region of interest (ROI) was selected to measure the CT value to calculate the contrast to noise ratio (CNR) and figure of merit (FOM). The volume CT dose index (CTDIvol) and Smart mA were recorded. The linear regression was conducted to analyze the relationship between CTDIvol, SmartmA, CNR and FOM. And with the same pose-ASiR-V level, the CNR of images which reconstructed by bone and soft algorithms were compared with pair-wise t test. The image quality was subjectively evaluated by three independent experienced radiologists using a 4-point scale (4 was the best).@*Results@#As the pre-ASiR-V levels (0—100%) increased, Smart mA and CTDIvol were reduced with a linear negative correlation (r=-0.981, -0.976, both P<0.001). The Smart mA decreased by 72.05% and CTDIvol by 71.22%. Keeping the same pre-ASiR-V level,the CNR increased with the increase of post-ASiR-V level (for the bone algorithm images:R2=0.976, 0.992, 0.982, 0.982, 0.975, 0.975, 0.979, 0.996, 0.952, 0.978, 0.965;for the standard algorithm images: R2=0.944, 0.990, 0.988, 0.993, 0.996, 0.987, 0.984, 0.996, 0.996, 0.990, 0.965).Under the same level of post-ASiR-V, the CNR and FOM fluctuated with the pre-ASiR-V level (for the bone algorithm images:R2=0.335, 0.341, 0.344, 0.364, 0.385, 0.405, 0.418, 0.429, 0.455, 0.474, 0.516; for the standard algorithm images: R2=0.223, 0.278, 0.327, 0.285, 0.309, 0.329, 0.325, 0.346, 0.360, 0.390, 0.380). All subjective image quality could meet the diagnostic requirements (the score≥3).@*Conclusion@#At NI=8, for the bone algorithm, the best combination is 80% pre-ASiR-V and 100% post-ASiR-V; for the standard algorithm, the best iteration combination is 100% and 100%. The appropriate choice of pre- and post-ASiR-V levels in paranasal sinus CT scan can effectively reduce the radiation dose under the premise of maintaining the image quality that meets the diagnostic needs.
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Objective To investigate the effects of different tube voltages on the dose of superficial radiation-sensitive organs and image quality when using organ dose modulation( ODM) in chest CT. Methods Based on clinical chest CT protocol with the sameother parameters, chest phantom was scanned using 140, 120, 100, and 80 kv ( 100 kV was the recommended by the CT system) without ODM ( ODM off ) or with ODM from the starting layer to the breast area ( ODM part ) . A long rod ionization chamber was placed iat a fixed position in front of the right breast area. The scans were repeated for 7 times with each group of scanning parameters and dose values were measured for each scanning, the CTDIvol and breast skin dose measurements( D) were recorded. Coronal images of 5 mm thickness for the lung and soft tissue algorithms were reformatted. The images were divided into 8 parts along the z axis direction, the contrast noise ratios( CNR) for every region were measured. For CTDIvol , D, CNR for different ODM and tube voltage scanning modes, two factor non-repeat test ANOVA was performed. LSD method was used for comparison among groups. Results The CTDIvol was lowest at 80 kV, and the breast skin dose measurement was lowest at 100 kV, CTDIvol decreased in turn from140 to 80 kV ( F=105. 5795, P<0. 05) . The breast skin dose measurement decreased in turn from140 to 100 kV, but increased instead at 80 kV. The difference was statistically significant(F=27. 736, P<0. 05). Compared with ODM off , the CTDIvol and D for ODM part both declined and the differences were statistically significant ( F=39. 732, 81. 961, P<0. 05). The CNRs of the lung and soft tissue images decreased at every tube voltage(F=12. 809, 11. 261, P<0. 05 ) . The CNRs decreased from140 to 100 kV, but there was no statistical difference( P>0. 05) , and the difference was significant at 80 kV( P<0. 05) . Compared with ODM off, the CNRs of lung and soft tissue algorithm images with ODM part decreased, withnot statistically significant differences ( P>0. 05 ) . Conclusions In clinical practice, with the tube voltage not less than the recommended(100 kV), the optimal reduction of breast radiation dose can be achieved by reducing kV and using ODM on the premise of resonable image quality.
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Objective To explore the effects of detector width and pitch on radiation dose and image quality when using organ dose modulation (ODM) technology in a wide?area detector CT scanning. Methods Based on the clinical chest scan protocol,3 sets of scans of the chest phantom were performed using any combination of two detector width (40 mm and 80 mm) and pitch (0.500,1.000 and 1.375) with the same parameters:1 Do not use ODM technology (ODM off),2 open ODM (ODM part) 240 mm from scan start layer to breast area,3 open ODM (ODM all) in full 320 mm scan range. A long rod ionization chamber was placed in the fixed position in front of the right breast area. The scanning parameters of each group were measured 7 times, and the volume computed tomography dose index (CTDIvol) and breast skin dose measurement values D were recorded and the mean was calculated and recorded as Dav. The coronal 5 mm thick images of lung and soft tissue algorithms were reformed. It was divided into three parts in the Z?axis direction, and the contrast?to?noise ratio (CNR) and figure of merit (FOM) were measured separately. Independent sample t test was used for CTDI and breast skin doses D and CNR at both detector widths. ANOVA was used for dose and CNR of three sets of pitch (0.500, 1.000, and 1.375) and the three ODM techniques. Result The FOM factor was the largest when using an 80 mm detector with a pitch of 0.992 and partially turning on the ODM. The radiation dose of the three ODM groups decreased in turn, and the effect of ODM on CTDIvol (P=0.019) and breast skin dose (P=0.002) was statistically significant. The width of the detector increased and the dose was increased. The width of the detector was statistically significant for CTDIvol (t=-2.723, P=0.015). There was no statistically significant effect on the breast skin dose (t=-0.908, P=0.377). The effects of the pitch were not statistically significant for CTDIvol (P=0.254) and breast dose (P=0.146). The CNR of the three ODM groups decreased in turn, and the effect of ODM on the soft tissue image CNR was not statistically significant (P=0.146). The CNR of lung algorithm image (P=0.030) had significant effects. The multiple comparisons:only ODM all was significantly different from ODM off (P=0.009). With the increase of detector width,the values of CNR increased,the values of CNR (t=-4.128,P=0.001) of lung images were significantly affected. The effects on the soft tissue images were not statistically significant (P=0.187). There was no statistically significant difference in the effect of pitch on the CNR (P=0.660) of the lung images. The effects of the pitch on the values of CNR of soft tissue images (F=11.756,P=0.001) were statistically significant. By multiple comparisons, the difference of CNR between 0.500 (P=0.000) and 1.375 (P=0.013) was statistically significant compared with that when the pitch was 1.000. There was no significant difference among the three ODM modes (P>0.05) on the values of CNR of upper and middle parts of lung and soft tissue arithmetic images. The differences of CNR between ODM all and the other two groups were statistically significant (P<0.05) on the bottom part of images. Conclusion The changes of detector width and pitch will affect the organs dose modulation technique, and then affect the radiation dose and image quality. When using 80 mm detector with the pitch of 0.992 and partially turning on ODM in chest CT scan,achieving the optimized benefits of quality and dose.
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A sub-microsecond pulse generation applied for electroporation effects of tumor cell is presented in this paper. The principle of the generator is that the expected pulse waveform is intercepted from the RC discharge curve by controlling the on-off states of two IGBT modules with a synchronous controller. Experimental tests indicate that the generator can produce adjustable pulse waveform parameters with 0.5-3.5kV amplitude, 300-800 ns pulse duration, 1-400Hz repetition frequency rate, and it is suitable for the study of the electroporation effect experiments.
