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Objective:To compare the dose and image quality of selected photon shield (SPS) technique, organ-based tube current modulation (OBTCM) technique and the combination of these two techniques for reducing the organ dose in head CT examination for infants.Methods:Two anthropomorphic head phantoms (CIRS 1-yr-old and 5-yr-old) were scanned by using Reference mode, Reference + OBTCM mode, SPS mode and SPS + OBTCM mode, respectively. Radiation doses to the lens of the eye, the anterior of the brain, the posterior of the brain, noise level and CNR of orbit and brain in different phantoms were measured and compared by using different scanning modes.Results:Compared with Reference mode, the doses to the lens of the eye in 1-yr-old and 5-yr-old phantom decreased by (21.89 ± 0.01)% and (28.33 ± 0.34)%, respectively. In SPS mode, the reduction in doses to the lens of the eye in 1-yr-old and 5-yr-old phantom were (71.38 ± 1.30)% and (53.72 ± 2.42)%, respectively. In SPS + OBTCM mode, the reduction was (71.12 ± 2.54)% and (55.73 ± 1.90)%, respectively. There was significant difference in the noise level of orbit and brain in different phantoms under various scanning modes ( F=5.67-85.47, P< 0.05). The noise level in OBTCM mode compared with reference mode increased slightly (<1.45 HU) in various phantoms. SPS and SPS + OBTCM mode resulted in a small noise increase (<2.58 HU). There was no significant difference in CNR of different phantoms under various scanning modes ( P>0.05). Conclusions:SPS and SPS + OBTCM mode can significantly reduce the radiation dose of lens and the whole image plane in the head CT scan for infants, with maintaining the image quality.
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Objective To investigate the effect of scan table on size-specific dose estimate ( size-specific dose estimate, SSDE) in children's CT scan. Methods CT imaging data and CTDIvol of 44 children ( 15 heads, 13 chests, 16 abdomen-pelvis) who underwent Siemens SOMATOM Definition AS+ 64 row 128-slice CT scan were retrospectively collected. CTDIvol of each patient was recored, WED ( water equivalent diameter) was calculated by two different methods ( with or without table) , donated as WED-T and WED-NT, then the corresponding SSDEWED ( SSDEWED-T and SSDEWED-NT ) was calculated. And the SSDEWED-NT was used as reference to evaluate the difference between WED and SSDEWED obtained by two different methods. Results Including part of table will lead to the overestimate for WED, with mean differences of 0. 10％, 2. 82％ and 2. 54％ for head, chest and abdomen-pelvis, respectively, while SSDEWED will be underestimated by 0. 06％ ( head ) , 2. 70％ ( chest ) and 1. 59％ ( abdomen-pelvis ) . Conclusions Including par of the patient table has a certain effect on SSDEWED for children, more attention should be paid for the application of SSDEWED.
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Objective@#To investigate the diagnostic value of whole liver CT perfusion imaging in the quantitative evaluation of hemodynamic changes before and after transcatheter arterial chemoembolization (TACE).@*Methods@#Twenty-six patients with hepatocellular carcinoma underwent TACE therapies were recruited. Whole -liver computed tomographic perfusion imaging (CTPI) was performed 2~3 days before TACE and 1 month after TACE. We measured the following perfusion parameters: hepatic arterial perfusion (HAP), portal venous perfusion (PVP), total liver perfusion (TLP), hepatic arterial perfusion index (HAPI), and time-to-peak (TTP).The F-test, t-test and Rank sum test were used for statistical analysis.@*Results@#A total of 34 HCC lesions were detected. According to the deposition of lipiodol after TACE, they were divided into a lipiodol dense group (21) and a lipiodol light group (13). The length of hepatocellular carcinoma lesions after TACE showed a decreasing trend compared with preoperative TACE. The lesions in the lipiodol dense group had smaller lesions than those in the lipiodol light group. The preoperative and postoperative longitudinal diameters were (3.12 ± 0.58) cm vs. (1.93 ± 0.79) cm, (2.98 ± 2.01) cm vs. (2.58 ± 2.00) cm, the differences were statistically significant (t = 15.1, 8.65, P < 0.05). The preoperative HAP and HPI of the lipiodol dense group were the highest, and the peritumoral within 1cm was higher than that of the surrounding liver parenchyma. The PVP, TLP, and TTP were highest in the surrounding of liver parenchyma, and 1 cm higher than the tumor area in the background. The corresponding perfusion parameters were statistically significant (P < 0.05); HAP and HPI were 1 cm higher than the surrounding liver parenchyma. After the operation, PVP, TLP and TTP were lower than the background liver parenchyma, the difference was statistically significant (P < 0.05); HAP and HPI decreased by 1 cm after the operation, and the PVP, TLP, and TTP increased. There was no significant difference after operation in the blood perfusion of background liver parenchyma (P ˃ 0.05). The HAP and HPI decreased, and the PVP and TTP increased in the lipiodol light group after operation (P < 0.05). There was no significant difference between the other two regions (P ˃ 0.05).@*Conclusion@#There was no blood perfusion in the lipiodol deposition area after TACE. The perfusion volume of hepatic artery in the peritumoral 1 cm and lipiodol light group decreased and the portal venous perfusion increased. CTPI can quantitatively evaluate blood perfusion state, which is of great significance for the determination of treatment plans before TACE treatment to assume the postoperative therapeutic effect in liver cancer.
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Objective To investigate the clinical value of iPass in three dimensional contrast enhanced MR angiography (3D-CE-MRA). Methods iPass were performed in 32 cases, including cervical vessel (4 cases), pulmonary vessel (7 cases), abdominal vessel (18 cases), and femoral vessel (3 cases). iPass bolus tracking was run before 3D-CE-MRA. The tracking sequence was operated repeatedly with real time display of image. The peak of bolus arrival time(Tp), identified with signal of target vessel increased 30% over baseline, was automatically loaded in the timing page of 3D-CE-MRA, and the time of scan delay(Td) was computed by the system with Tp. The acquired images were subtracted and reconstructed by MIP. The quality of MIP image was evaluated. Results The iPass bolus tracking sequence and 3D-CE-MRA were completed successfully in 29 cases. The bolus tracking couldn′t detect the bolus arrival time in 3 cases, but they were completed through changing ROI and bolus tracking repeatedly. The average score of 3D-CE-MRA MIP image was 3.81?0.59. Conclusion iPass can provide the exact Tp and automatically control Td of 3D-CE-MRA. iPass is a useful procedure to improve the image quality and provide the specific scanning scheme for 3D-CE-MRA.
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Objective Objective To study the feasibility of direct applying MRI to TPS by measuring the geometric distortion of MRI. Methods Phantom 1 was made by marking radical arrangement of fat pipelines every 15? in foam phantom and Phantom 2 by net arrangement at every 2.7?cm. Coronal and transverse scan parallel with the radial and net fat pipeline in the phantom was performed at sequence of cranial FSE T2WI by Marconi 1.5T superconduct MRI machine. Geometric distortion in 5 different fields of view (FOV) was calculated by measuring the absolute borderline error of direct scan and coronal digital reconstructed radiograph (DRR). Results When FOV was equal or smaller than 11.0?cm?11.0?cm, 22.0?cm?22.0?cm and 27.5?cm?27.5?cm, the geometric distortion was 0.0, 1.1 and 1.4?mm of direct scanning MRI and 1.0,1.4 and 2.0?mm of coronal DRR. Conclusion When the magnetic field of MR is high and the tissue shows uniform density, MRI can be applied on TPS directly.