Use Of Automatic Tube Current Modulation Research Articles

Automatic Tube Current Modulation and Tube Voltage Selection in Pediatric Computed Tomography

The aim of this study was to investigate the effects of a modern automatic tube current modulation (ATCM) and automatic tube voltage selection (ATVS) system on radiation dose and image quality in pediatric head, and torso computed tomography (CT) examinations for various clinical indications. Four physical anthropomorphic phantoms that represent the average individual as neonate, 1-year-old, 5-year-old, and 10-year-old child were used. Standard head, thorax, and abdomen/pelvis acquisitions were performed with (1) fixed tube current, (2) ATCM, and (3) ATVS. Acquisitions were performed at various radiation dose levels to generate images at different levels of quality. Reference volume CT dose index (CTDIvol), reference image noise, and reference contrast-to-noise ratios were determined. The potential dose reductions with ATCM and ATVS were assessed. The percent reduction of CTDIvol with ATCM ranged from 8% to 24% for head, 16% to 39% for thorax, and 25% to 41% for abdomen/pelvis. The percent reduction of CTDIvol with ATVS varied on the clinical indication. In CT angiography, ATVS resulted to the highest dose reduction, which was up to 70% for head, 77% for thorax, and 34% for abdomen/pelvis. In noncontrast examinations, ATVS increased dose by up to 21% for head, whereas reduced dose by up to 34% for thorax and 48% for abdomen/pelvis. In pediatric CT, the use of ATCM significantly reduces radiation dose and maintains image noise. The additional use of ATVS reduces further the radiation dose for thorax and abdomen/pelvis, and maintains contrast-to-noise ratio for the specified clinical diagnostic task.

Signal-to-noise ratio and dose to the lens of the eye for computed tomography examination of the brain using an automatic tube current modulation system.

The study aimed to evaluate the image quality in terms of signal-to-noise ratio (SNR) and dose to the lens of the eye and the other nearby organs from the CT brain scan using an automatic tube current modulation (ATCM) system with or without CT gantry tilt is needed. An anthropomorphic phantom was scanned with different settings including use of different ATCM, fixed tube current time product (mAs) settings and degree angles of gantry tilt. Gafchromic film XR-QA2 was used to measure absorbed dose of the organs. Relative doses and SNR for the various scan settings were compared with the reference setting of the fixed 330 mAs. Average absorbed dose for the lens of the eyes varied from 8.7 to 21.7mGy. The use of the ATCM system with the gantry tilt resulted in up to 60% decrease in the dose to the lens of the eye. SNR significantly decreased while tilting the gantry using the fixed mAs techniques, compared to that of the reference setting. However, there were no statistical significant differences for SNRs between the reference setting and all ATCM settings. Compared to the reference setting of the fixed effective mAs, using the ATCM system and appropriate tilting, the gantry resulted in a substantial decrease in the dose to the lens of the eye while preserving signal-to-noise ratio. CT brain examination should be carefully controlled to optimize dose for lens of the eye and image quality of the examination.

Potential for radiation dose savings in abdominal and chest CT using automatic tube voltage selection in combination with automatic tube current modulation.

The purpose of this study was to evaluate the simultaneous use of automatic tube current modulation (ATCM) and automatic tube voltage selection (ATVS) for abdominal and chest CT examinations regarding radiation dose reduction and image quality. We enrolled 617 patients who all underwent contrast-enhanced chest or abdominal CT and divided them into two groups. In group A, 317 patients who underwent CT with only ATCM and a fixed body mass index-adjusted tube voltage (120 kV or 100 kV) were enrolled. In group B, both ATCM and ATVS were used. Image attenuation and noise were measured in different anatomic regions. The mean contrast-to-noise ratio and the signal-to-noise ratio of abdomen and chest CT was higher in group B compared with group A (p < 0.0001). In total, the effective radiation doses for abdomen and chest CT examinations were significantly reduced in group B by 18% compared with group A (p < 0.0001). When only examining those who benefited from the ATVS tool, a dose reduction of 35% for chest CT and 42% for abdomen CT could be achieved (p < 0.0001 for each). The simultaneous use of ATVS and ATCM enables significant radiation dose reduction in abdominal and thoracic contrast-enhanced CT examinations compared with the use of ATCM alone.

Impact of automatic tube current modulation on CT dose and image quality from a view of nationwide survey

Impact of automatic tube current modulation on CT dose and image quality from a view of nationwide survey

Attenuation-based Automatic Tube Voltage Selection and Tube Current Modulation for Dose Reduction at Contrast-enhanced Liver CT

To retrospectively determine whether the combined use of automatic tube voltage selection (ATVS) and automatic tube current modulation (ATCM) can effectively reduce radiation dose at contrast material-enhanced liver computed tomography (CT) while maintaining acceptable image quality compared with the use of ATCM alone. This study was approved by an institutional review board, and informed consent was waived. Three hundred fourteen consecutive patients suspected of having liver disease were divided into three groups. In two groups, both ATVS and ATCM were used (group A1, n=97; group A2, n=101) but with different contrast gain settings; in one group, only ATCM with a fixed tube potential of 120 kV (group B, n=116) was used. Weighted volume CT dose index and dose-length product, contrast-to-noise ratios (CNRs), and mean image noise were assessed. Qualitative analysis was performed by two board-certified radiologists and one radiology resident. Statistical analysis was performed by using the one-way analysis of variance test, two-tailed paired t test, Kruskal-Wallis test, and noninferiority test. In groups A1 and A2, a significant dose reduction was obtained compared with that in group B (P<.0001). The mean dose reduction was 20% in group A1 and 31% in group A2. Furthermore, CNRs were significantly higher in groups A1 and A2 than in group B (P<.0001). Despite the higher image noise in groups A1 and A2, the overall image quality was acceptable. Compared with the use of ATCM alone, the combined use of ATVS and ATCM allowed reduction of radiation exposure while maintaining good image quality at contrast-enhanced liver CT.

Use of automatic tube current modulation with a standardized noise index in young children undergoing chest computed tomography scans with 64-slice multidetector computed tomography

The automatic tube current modulation (ATCM) technique is available on multidetector computed tomography (MDCT) scanners, and its dose reduction benefits in clinical applications have been documented primarily in adult patients. To evaluate the use of ATCM to reduce radiation dose while maintaining consistent image quality for young children undergoing 64-slice MDCT chest scans. Chest scans (120 kV, small-scan field of view, 5-mm image slice thickness) were performed for 50 consecutive young children (0.2-3 years) using 64-slice volume computed tomography (VCT) with ATCM method and a noise index (NI) of either 8 or 9, depending on the patient's age. The scanner automatically selected the actual tube current based on NI values and patient attenuation as determined by scout scans for the study group. Image quality and volume-weighted CT dose index (CTDI(vol)) values (measured with small-scan field of view and 16-cm diameter CTDI phantom) were compared with images from a control group of 50 children acquired earlier using a standard protocol with fixed tube current. Two experienced pediatric radiologists assessed image quality, including resolution, noise, and artifacts, on a five-point scale. Scores greater than or equal to 3 were considered to be clinically acceptable. The mean image quality score and CTDI(vol) for the study and control groups were 3.46 and 2.34+/-0.71 mGy, and 4.65 and 6.68+/-0.62 mGy, respectively. While there was a statistically significant decrease in image quality in the study group, all studies had acceptable image quality, and CTDI(vol) with ATCM was about 65% lower than that with fixed tube current. The average image noise for the control group was 4.78+/-0.58, versus 7.53+/-0.42 and 8.28+/-0.40 for children under and above 1 year of age, respectively, in the study group. Despite a higher average noise level, the study group with ATCM demonstrated a lower standard deviation of image noise. The z-axis ATCM method produces consistent image quality for young children undergoing 64-slice MDCT chest scans. With noise levels of NI=8 and 9 at 5-mm image slice thickness, one may obtain clinically acceptable images with significantly reduced radiation dose.