Application of cone beam computed tomography in the diagnosis of root fractures / 口腔疾病防治

@#Cone beam computed tomography (CBCT) has been widely used in various fields of dentistry. The diagnosis of root fractures, especially vertical root fractures (VRFs) with CBCT images, has been a research hotspot since then. Research on this area mainly includes the following five aspects: ① the diagnostic efficiency of CBCT images for root fractures; ② the influence of scanning parameters on the diagnostic accuracy of CBCT images in root fractures, such as scanning field of view, spatial resolution, tube current and tube voltage; ③ whether the application of image postprocessing techniques, especially metal artifact reduction (MAR), can improve the diagnostic accuracy of root fractures after root canal treatment and/or there is a post core in the root canal; ④ establishment and validation of clinical diagnosis model for vertical root fracture; and ⑤ application of artificial intelligence technology and contrast agent in root canals for the diagnosis of CBCT image in root fractures. Compared with periapical radiographs, CBCT images can improve the diagnostic accuracy of root fractures in nonendodontic treated teeth; however, for teeth that have undergone endodontic treatment, the diagnosis of VRF must be combined with clinical signs. Vertical bone resorption in the buccolingual (palatal) direction is a characteristic indicator of VRF. The width of the VRF is an important factor affecting the diagnostic accuracy, but the voxel size used in CBCT scanning is not a necessary factor affecting its diagnostic accuracy; the fracture direction does not affect the diagnostic accuracy of the VRF. Image postprocessing techniques, especially MAR, cannot improve the diagnostic accuracy of VRF and may also reduce the diagnostic efficiency, so they are not recommended for clinical application.

A study of the effect of scanning center on the performance of organ dose modulation in head CT / 中华放射医学与防护杂志

Objective:To investigate the effect of different scanning centers on eye lens dose, image quality, and the dose reduction rate when using the organ dose modulation (ODM) technique in head CT.Methods:The porus acusticus externus of the head phantom was considered the scanning isocenter. The ODM was initiated and the spiral scans were performed at the scanning centers with the height of porus acusticus externus and its upper and lower 2, 4, and 6 cm, respectively. The scanning range was from the top of the head to the base of the head. Three thermoluminescent dosimeters (TLD) were placed on the surface of two eyes at each scan and the average measurement value was regarded as the radiation dose to the eye lens. The volume CT dose index (CTDI vol) and dose length product (DLP) were recorded. The scans were repeated with no ODM and the dose reduction rates at each scanning center were calculated. The regions of interest (ROI) in each group of images with ODM were drawn and the noise (SD), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were evaluated. Results:Compared with the isocenter, the maximum change rates of CTDI vol and DLP in each scanning center were 2.46% and 2.43%, respectively. The eye lens dose increased as the scanning centre moving upwars (i.e. the bed dropping) by 39.02% at the position of 6 cm above the isocenter and decreased by 35.91% at the position of 6 cm below the isocenter. With the seven groups of scanning centers, the reduction rates of CTDI vol and DLP caused by ODM were 7.95%-8.61%, 7.91%-8.61% respectively, and the difference in the reduction rate of each dose value was not statistically significant( P>0.05). The reduction rate for eye lens dose ranged from 18.09% to 26.14%, with the highest reduction rate at the position of 4 cm above the isocentre and the second rate at the isocentre (24.73%). The difference in the rate of reduction at each scanning center was statistically significant( t=0.13, P<0.05). As the scanning center moved up, the SD of the eye region decreased and the SNR increased, and the highest CNR at the isocentre was 239.79. The SD and SNR of the brain parenchyma region were 6.85-7.96 and 3.08-4.19 respectively, and the highest CNR at the isocentre was 244.79. Conclusions:When ODM technique is used in head CT, the scan centre has a significant effect on the eye lens dose and image quality. Meanwhile, the reduction rate of the eye lens dose caused by ODM is also affected. Therefore, porus acusticus externus is recommended as the scanning center in head CT.

Evaluation of selected photon shield and organ-based tube current modulation for organ dose reduction and image quality in head CT for infants: a phantom study / 中华放射医学与防护杂志

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.

Determining the Feasibility of Dose Reduction Strategies on Radiation Dose: An Experimental Phantom Study

@#Introduction: Radiation exposure during the CT examination has always been a concern due to its associated cancer risk. The guidelines suggest the optimization of radiation dose reduction. Therefore, this study aims to determine the feasibility of dose reduction strategies on radiation dose reduction using a phantom. Methods: Head and body phantoms of 16 cm and 32 cm, respectively, were used to calculate the radiation dose and measure the quantitative image quality. The phantoms were positioned and scanned with the standard protocol and low dose protocol. For dose reduction strategies, scan length was reduced in head phantom, and tube voltage and tube current were manipulated individually and by combining both and tested in both head and body phantoms. Also, the influence of rotation time was investigated in body phantom. Quantitative image quality was determined by drawing a region of interest on the obtained image. Results: Reducing scan length showed 41% reduction of radiation dose and reducing tube current, and tube voltage showed up to 75% reduction of radiation dose in head phantom and 70% reduction of radiation dose in body phantom compared to the standard protocol. The reduction of the rotation time, however, reduced the scan time and the radiation dose but the maximum mAs or tube current allowed was limited. Quantitative image quality was reduced when using a lower dose protocol. Conclusion: The dose reduction strategies showed a reduced dose, but the quantitative image quality score was reduced when scanned with low dose protocol. Further manipulation can be performed to maintain image quality.

Feasibility of low-dose radiation CT scanning for liver 3D modeling printing / 医学研究生学报

Objective In the wide clinical practice of liver 3D printing, its related high-dose CT radiation has been somehow neglected and resulted in unnecessary radiation injury to the patients. This study was to explore the feasibility of liver 3D modeling printing with the low-dose radiation CT scanning technique.　Methods　This retrospective study included 40 patients undergoing liver 3D modeling printing from January 2016 to June 2018, who were equally randomized into a low-dose radiation group (100 kVp, by automated tube current modulation [ATCM] and adaptive statistical iterative reconstruction [ASIR]) and a normal-dose radiation group (120 kVp, 250 mA by filter back projection [FBP]), both with contrast agent Iohexol at 300 mgI/m1. We obtained the values of three-phase enhanced CT scanning of the abdominal aorta, portal vein and liver parenchyma, background noise (BN), volume CT dose index (CTDI), dose length product (DLP), contrast noise ratio (CNR) and effective radiation dose (ED). We input the CT DICOM data into the 3D printer for liver modeling printing and subjectively assessed the results. Results There were statistically significant differences between the low-dose and normal-dose radiation groups in the CTDI, DLP and ED (P 0.05). The ED was decreased about 35.8% in the low-dose group as compared with that in the normal-dose group ([2.58 ± 0.79] vs [4.02 ± 0.26] mSv, P 0.05). Conclusion Low-dose radiation CT scanning technology can meet the clinical requirement of liver 3D modeling printing and significantly reduce the patient’s exposure to CT radiation.

Is It Better to Enter a Volume CT Dose Index Value before or after Scan Range Adjustment for Radiation Dose Optimization of Pediatric Cardiothoracic CT with Tube Current Modulation?

OBJECTIVE: To determine whether the body size-adapted volume computed tomography (CT) dose index (CTD(vol)) in pediatric cardiothoracic CT with tube current modulation is better to be entered before or after scan range adjustment for radiation dose optimization. MATERIALS AND METHODS: In 83 patients, cardiothoracic CT with tube current modulation was performed with the body size-adapted CTDIvol entered after (group 1, n = 42) or before (group 2, n = 41) scan range adjustment. Patient-related, radiation dose, and image quality parameters were compared and correlated between the two groups. RESULTS: The CTDIvol after the CT scan in group 1 was significantly higher than that in group 2 (1.7 ± 0.1 mGy vs. 1.4 ± 0.3 mGy; p 0.05). In both groups, all patient-related parameters, except body density, showed positive correlations (r = 0.49–0.94; p 0.05) in group 2. CONCLUSION: In pediatric cardiothoracic CT with tube current modulation, the CTDIvol entered before scan range adjustment provides a significant dose reduction (18%) with comparable image quality compared with that entered after scan range adjustment.

Feasibility of low radiation dose and iodine contrast medium in 70 kVp abdominal CTA in low body mass index patients / 中国医学影像技术

Objective To explore the feasibility of reducing radiation dose and iodine contrast medium in 70 kVp abdominal CTA imaging in low-body mass index (BMI;≤22 kg/m2) patients.Methods The 48 patients with suspected abdominal vascular diseases and low BMI (≤22 kg/m2) underwent abdominal CTA.All patients were divided into two groups according to tube voltage and contrast intake randomly.The parameters of group A (n=27) were contrast intake 300 mgI/kg,70 kVp,the conditions of group B (n=21) were contrast intake 500 mgI/kg,120 kVp,and the other conditions were the same in both groups.The image quality of right renal arterial images was evaluated by two observers simultaneously (5-scale).The consistency and difference between the two observers were analyzed.The CT values of abdominal aorta,celiac trunk,superior mesenteric artery,common hepatic artery,pancreatic artery and erector spinae,SD values of erector spinae on the level of right renal hilus were measured respectively in both groups.The CT values of abdominal aorta and its main branches,the CNR of abdominal aorta,the volume CT dose index (CTDIvol),dose-length product (DLP) and overall iodine intake in each group were compared.Results The scoring of right renal arterial images in both groups were 5.00 (1.00),the results showed a good consistency (Kappa=0.932,0.911).The CT values of abdominal aorta,superior mesenteric artery,common hepatic artery and pancreatic artery in group A were all more than those of in group B (all P＜0.05).The CNR of group A was higher than that of group B (P＜0.05).The CTDIvoland DLP in group A decreased by 73.36％ and 74.41％ compared with group B.The overall iodine intakes in group A and group B were (46.33±6.43)ml and (84.31±10.71)rnl,respectively.The overall iodine intake of group A decreased by 45.05％ compared with group B.Conclusion For patients with low BMI (≤22 kg/m2),a 70 kVp tube current abdominal CTA scanning can significantly increase the contrast of images of abdominal artery and its branches.Meanwhile,the radiation dose and overall iodine intake can obviously decrease.

Comparison of standardized uptake values measured on 18F-NaF PET/CT scans using three different tube current intensities / Comparação dos valores de captação medidos nos estudos de 18F-NaF PET/CT utilizando três intensidades diferentes de corrente do tubo de tomografia computadorizada

Objective: To analyze standardized uptake values (SUVs) using three different tube current intensities for attenuation correction on 18FNaF PET/CT scans. Materials and Methods: A total of 254 18F-NaF PET/CT studies were analyzed using 10, 20 and 30 mAs. The SUVs were calculated in volumes of interest (VOIs) drawn on three skeletal regions, namely, right proximal humeral diaphysis (RH), right proximal femoral diaphysis (RF), and first lumbar vertebra (LV1) in a total of 712 VOIs. The analyses covered 675 regions classified as normal (236 RH, 232 RF, and 207 LV1). Results: Mean SUV for each skeletal region was 3.8, 5.4 and 14.4 for RH, RF, and LV1, respectively. As the studies were grouped according to mAs value, the mean SUV values were 3.8, 3.9 and 3.7 for 10, 20 and 30 mAs, respectively, in the RH region; 5.4, 5.5 and 5.4 for 10, 20 and 30 mAs, respectively, in the RF region; 13.8, 14.9 and 14.5 for 10, 20 and 30 mAs, respectively, in the LV1 region. Conclusion: The three tube current values yielded similar results for SUV calculation. .

Objetivo: Analisar os valores de captação (SUVs) utilizando três diferentes intensidades de mAs para realização de correção de atenuação na 18F-NaF PET/CT. Materiais e Métodos: Um total de 254 exames de 18F-NaF PET/CT foi estudado utilizando 10, 20 e 30 mAs. Os SUVs foram calculados utilizando volumes de interesse (VOIs) desenhados em três regiões do esqueleto: diáfise proximal do úmero direito (UD), diáfise proximal do fêmur direito (FD) e primeira vértebra lombar (VB1), totalizando 712 VOIs. Desse total, 675 regiões classificadas como normal foram analisadas (236, 232 e 207 na UD, FD e VB1, respectivamente). Resultados: A média dos SUVs para cada região óssea foi 3,8, 5,4 e 14,4 para UD, FD e VB1, respectivamente. Quando os exames foram agrupados pelo valor da corrente mAs, a média de valores de captação foi 3,8, 3,9 e 3,7 para 10, 20 e 30 mAs, respectivamente, na UD; 5,4, 5,5 e 5,4 para 10, 20 e 30 mAs, respectivamente, na FD; e 13,8, 14,9 e 14,5 para 10, 20 e 30 mAs, respectivamente, na VB1. Conclusão: As três correntes analizadas apresentaram resultados similares para o cálculo de SUV. .

Preliminary study of peripheral artery CT angiography with auto-tube current of different tube voltage and noise index / 实用放射学杂志

Objective To evaluate the effect of different tube voltage and noise index (NI)on image quality and radiation dose during peripheral artery CTA with automatic tube current modulation(ATCM)technique.Methods Seventy-two patients were ran-domly divided into three groups with different scanning tube voltage and noise index as follows:group A with 100 kV and NI of 1 5, group B with 80 kV and NI of 1 5,group C with 100 kV and NI of 20.Image quality,segmental vascular enhancement,signal-to-noise ratio (SNR),contrast-to-noise (CNR)and effective dose (ED)were independently evaluated in 3 groups.The methods of sta-tistics analysis were ANOVA,and P 0.05).Conclusion Using ATCM low-kV with high NI scanning can reduce radiation dose without interference on image quality for peripheral artery CTA.

Effect of Tube Current on the Pseudo-enhancement of Renal Cyst / 中国医学影像学杂志

PurposeTo evaluate the effect of tube current on the pseudo-enhancement of renal cyst by simulating the phantom model of simple renal cyst.Materials and Methods 10% glucose and iodine solution with a certain concentration was used to simulate the renal parenchymal background concentration in plain scan, moderate enhancement and maximum enhancement respectively. The diameters of the cysts were 6 mm, 10 mm and 15 mm, respectively, and the cysts were divided into three groups according to different tube current: 119 mAs (group A), 178 mAs (group B) and 297 mAs (group C) while the tube voltage were all 120 kV. Whether pseudo-enhancement exists in cyst under different conditions was determined using an increase of CT value of 10 HU as the critical value. Results In group A, there was pseudo enhancement at the 240 HU background, and it was most significant with the diameter of 6 mm, which was 21 HU. In group B, pseudo-enhancement occurred in cysts with diameter of both 10 mm and 6 mm under the background of 180 HU and 240 HU, moreover, the biggest difference was 20.4 HU and it occurred in cyst with diameter of 6 mm under the background of 240 HU. In group C, pseudo-enhancement only occurred in cyst with diameter of 6 mm under the condition of 125 HU and 240 HU background concentration. Background concentration (F=17.587, P<0.01) and cyst diameter (F=4.214,P<0.05) had greater impact on cyst pseudo-enhancement, the higher the background concentration and smaller the diameter, more significantly the pseudo-enhancement would occur. With the increase of the tube current, the CT volume dose index increased, and the pseudo enhancement value was smaller, but there was no obvious regularity of pseudo-enhancement occurrence rate in cysts with different background concentration and diameter in each group.Conclusion The increase of tube current cannot completely eliminate cyst pseudo-enhancement. High background concentration and small diameter cyst are important factors in pseudo-enhancement. However, increasing the tube current can reduce the probability of occurrence of pseudo-enhancement to some extent. For those with heavier body weight, it might be necessary to increase the tube current to improve image quality and reduce the occurrence of renal cyst pseudo-enhancement.

Combined Use of Automatic Tube Voltage Selection and Current Modulation with Iterative Reconstruction for CT Evaluation of Small Hypervascular Hepatocellular Carcinomas: Effect on Lesion Conspicuity and Image Quality

OBJECTIVE: To assess the lesion conspicuity and image quality in CT evaluation of small (< or = 3 cm) hepatocellular carcinomas (HCCs) using automatic tube voltage selection (ATVS) and automatic tube current modulation (ATCM) with or without iterative reconstruction. MATERIALS AND METHODS: One hundred and five patients with 123 HCC lesions were included. Fifty-seven patients were scanned using both ATVS and ATCM and images were reconstructed using either filtered back-projection (FBP) (group A1) or sinogram-affirmed iterative reconstruction (SAFIRE) (group A2). Forty-eight patients were imaged using only ATCM, with a fixed tube potential of 120 kVp and FBP reconstruction (group B). Quantitative parameters (image noise in Hounsfield unit and contrast-to-noise ratio of the aorta, the liver, and the hepatic tumors) and qualitative visual parameters (image noise, overall image quality, and lesion conspicuity as graded on a 5-point scale) were compared among the groups. RESULTS: Group A2 scanned with the automatically chosen 80 kVp and 100 kVp tube voltages ranked the best in lesion conspicuity and subjective and objective image quality (p values ranging from < 0.001 to 0.004) among the three groups, except for overall image quality between group A2 and group B (p = 0.022). Group A1 showed higher image noise (p = 0.005) but similar lesion conspicuity and overall image quality as compared with group B. The radiation dose in group A was 19% lower than that in group B (p = 0.022). CONCLUSION: CT scanning with combined use of ATVS and ATCM and image reconstruction with SAFIRE algorithm provides higher lesion conspicuity and better image quality for evaluating small hepatic HCCs with radiation dose reduction.

The application of low dose CT with automatic tube current modulation in the diagnosis of pneumoconiosis / 中国医师进修杂志

Objective To explore the feasibility and application value of low dose CT with automatic tube current modulation (ATCM) in the diagnosis of pneumoconiosis.Methods Forty-five patients with pneumoconiosis confirmed by the occupational agency underwent standard dose CT scanning with a fixed tube current of 150 mA and low dose CT scanning with ATCM (50-200 mA) with noise index (NI) of 14.The CT dose index volume (CTDIvol) and dose length product (DLP) under the different scanning condition were recorded.The image quality,specific image manifestations of pneumoconiosis (shadow size,shadow concentration,pneumoconiosis stages) were reviewed in double-blind methods by two radiologists,and the statistical analysis was performed.Results CT characteristics of pneumoconiosis could be detected efficiently with low dose CT scanning with ATCM.There were no significant differences in showing the shadow size,shadow concentration,pneumoconiosis stages and the image quality between the two groups (P＞0.05).The CTDIvol and DLP of standard dose CT scanning were 13.53 mGy and (337.13 ± 13.53) mGy/cm respectively,and CTDIvol and DLP of low dose CT scanning with ATCM were (7.39 ± 0.45) mGy and (188.78 ± 1.80) mGy/cm,there were statistical differences (P ＜ 0.05).Conclusions Low dose CT scanning with ATCM can reflect the characteristics of pneumoconiosis,and it also can significantly reduce the radiation dose with diagnostic acceptability of the image quality.So low dose CT scanning with ATCM can replace the standard dose CT scan in diagnosing and screening of the pneumoconiosis.

Influence of tube voltage on CT attenuation, radiation dose,and image quality:phantom study / 中华放射学杂志

Objective To assess the influence of tube current and tube voltage on the CT attenuation,radiation dose,and image quality.Methods A total of 113 saline solutions with decreasing dilution of contrast medium (370 mg I/ml) was produced.MDCT scan was performed with 15 series of different settings of tube current and tube voltage.CT attenuations with 15 series of different settings were all measured,and influence of tube current and tube voltage on CT attenuations was analyzed.CT dose index (CTDIvol) was recorded.The CT attenuations with different tube voltage and current were compared with one-way ANOVA and Kruskal-Wallis rank sum test.The correlation of CT attenuation with different tube voltage and the influence of tube voltage and current on radiation dose and image quality were tested by correlation analysis.Results Tube current (250,200,150,100,and 50 mA) had no significant effect on CT attenuation (F =0.001,0.008,0.075,P ＞ 0.05),while tube voltage (120,100,and 80 kV) had significant effect (H =17.906,17.906,13.527,20.124,23.563,P ＜ 0.05).The correlation between CT attenuation and tube voltage was determined with equation:CT attenuatio N100 kV =1.561 × CT attenuatio N120kv + 4.0818,CT attenuatio N80kV =1.2131 × CT attenuatio N120kv + 0.9283.The influence of tube voltage on radiation dose and image quality was also analyzed,and equations were also obtained:N120 kV =-5.9771Ln(D120 kV) + 25.412,N100 kV =--10.544Ln (D100 kV) + 36.262,N80 kV =-25.326Ln(D80kv) +62.816.According to the results of relationship among CT attenuation,radiation dose,and image quality,lower tube voltage with higher tube current can reduce the radiation dose.Conclusions Lower tube voltage can reduce the radiation dose.However,CT attenuation was influenced,and correction should be done with the equations.

Correlation between the tube current and image noise in low-dose chest CT scean / 中华放射医学与防护杂志

Objective To analyze the distribution of image noise in low-dose chest CT scan and optimize the relative scanning parameters.Methods The CT images of the Chinese anthropomorphic chest phantom( CDP-1 C) were simulated into six groups of low-dose images with different noise indexs by using an image noise addition tool.The difference between the preset noise index and analog noise value was compared.The CT images of 20 volunteers were also simulated into nine groups of low dose scans with the tube currents of 10,30,50,80,100,120,150,180 and 240 mA.The noise values of images were recorded and analyzed.Results There was no statistical difference between the analog noise value and the noise index.The image noise of low-dose chest scan was increased with the decrease of tube current.The noise was increased quickly when the current was decreased from 50 to 30 mA ( F =24.09 - 40.79,P ＜ 0.05),but the noise increased slowly when the current decreased from 240 to 80 mA.There was no statistical difference between the noise of 80 mA group and that of 120 mA(P ＞ 0.05).Conclusions The noise addition tool can be used to evaluate the image noise of low-dose chest CT scan.Adoption of 80 mA in chest CT scan would result in low radiation dose without adding image noise.

Reduction in thyroid dose from neck CT angiography with 64-slice spiral CT with automatic tube current modulation technique / 中华放射医学与防护杂志

Objective To assess the effectiveness of Z-axis automatic tube current modulation ( ATCM) technique with respect to dose reduction and image noise in the thyroid regional tissues during neck computed tomography angiography (CTA). Methods A total of 140 patients underwent neck CTA with 64-slice spiral CT, and were randomized into fixed-tube current group and ATCM group. Objective noise, CTDIw, DLP and mA of each group were recorded. Results The image qualities of all the patients were diagnostically acceptable, though the objective noise of neck in the ATCM group was higher than that in the group of fixed-tube current (P＜ 0.05 ). The radiation doses in the ATCM group [ CTDIw (35.99±1.31 ) mGy, DLP (11 121.39 ±5.51) mGy·cm] were significantly inferior to those in the group of fixed tube current [ CTDIw (43.22±1.42) mGy, DLP (1514.45±5.56) mGy·cm]. Conclusions Compared with fixedtube current technique, ATCM technique could significantly reduce the radiation dose in neck CT with diagnostic acceptability of the image quality.

Method for Automatic Tube Current Selection for Obtaining a Consistent Image Quality and Dose Optimization in a Cardiac Multidetector CT

OBJECTIVE: To evaluate a quantitative method for individually adjusting the tube current to obtain images with consistent noise in electrocardiogram (ECG)-gated CT cardiac scans. MATERIALS AND METHODS: The image noise from timing bolus and cardiac CT scans of 80 patients (Group A) who underwent a 64-row multidetector (MD) CT cardiac examination with patient-independent scan parameters were analyzed. A formula was established using the noise correlation between the timing bolus and cardiac scans. This formula was used to predict the required tube current to obtain the desired cardiac CT image noise based on the timing bolus noise measurement. Subsequently, 80 additional cardiac patients (Group B) were scanned with individually adjusted tube currents using an established formula to evaluate its ability to obtain accurate and consistent image noise across the patient population. Image quality was evaluated using score scale of 1 to 5 with a score of 3 or higher being clinically acceptable. RESULTS: Using the formula, we obtained an average CT image noise of 28.55 Hounsfield unit (HU), with a standard deviation of only 1.7 HU, as opposed to a target value of 28 HU. Image quality scores were 4.03 and 4.27 for images in Groups A and B, respectively, and there was no statistical difference between the image quality scores between the two groups. However, the average CT dose index (CTDIvol) was 30% lower for Group B. CONCLUSION: Adjusting the tube current based on timing bolus scans may provide a consistent image quality and dose optimization for cardiac patients of various body mass index values.

Dose Measurements using Phantoms for Tube Voltage, Tube Current, Slice Thickness in MDCT / 의학물리

The purpose of this study was to measure and evaluate radiation dose for MDCT parameters. Patient dose for various combination of MDCT parameters were experimentally measured, using MDCT (GE light speed plus 4 slice, USA), model 2026C electrometer (RADICAL 2026C, USA), standard Polymethylmethacrylate (PMMA) head and body CT dosimetry phantoms. In clinical situations, for a typical abdominal scan performed with MDCT at 120 kVp, 180 mAs, 20 mm collimation, and a pitch of 0.75, CTDIw, CTDIvol were measured as 20.2 mGy, 26.9 mGy, respectively. When scan length is assumed as 271.3 mm, DLP and measured effective dose of the abdominal would be calculated as 729.1 mGy cm, 10.9 mSv, respectively.

Quality-control testing,evaluation and application of X-ray machine's major parameters / 医疗卫生装备

This paper introduces the testing methods with respect to the major parameters (X-ray tube voltage & current,exposure time,exposure volume)of X-ray machine as well as the testing results evaluation and application. It is proved that quality control of x-ray machine is an important content and technical means as to guarantee quality for radiology department of hospital.

Discussion on Automated Dose Management / 医疗卫生装备

The method and developing progress on CT automated dose management are introduced. Modern method on CT automated dose management compromises real-time angular dose modulation and Z axis tube current modulation. Provided the automated dose management are correctly applied,the image quality can be optimized at minimum dose.

Application of Automatic Tube Current Modulation Techniques in the Abdomen Multi-slice CT Scanning / 医疗卫生装备

0.05),an effective mA seconds in the experimental group(296.74?19.15)mAs,than in the control group 350 mAs was reduced about 15.4%(P