Circle of Willis at CT Angiography: Dose Reduction and Image Quality—Reducing Tube Voltage and Increasing Tube Current Settings

Waaijer, Annet; Prokop, Mathias; Velthuis, Birgitta K.; Bakker, Chris J.G.; Kort, G. A. P. de; Leeuwen, Maarten S. van

doi:10.1148/radiol.2423051191

Cited by 145 publications

(93 citation statements)

References 14 publications

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“…In this phantom, the mean CT number of brain parenchyma was approximately 33 HU in all images of the cerebrum level at 120 kV. The mean attenuation for brain parenchyma of the patients is reportedly 35 HU in CTA at 120 kV [17]. The mean CT numbers for the internal carotid artery of 20 patients were 340 ¡ 60.1 HU at 90 kV and 253 ¡ 46.3 HU at 120 kV in CTA [17].…”

Section: Tube Voltage and Effective Masmentioning

confidence: 81%

Radiation dose evaluation in multidetector-row CT imaging for acute stroke with an anthropomorphic phantom

Yamauchi-Kawara

Fujii²,

Aoyama³

et al. 2010

BJR

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ABSTRACT. This study evaluated radiation dose and dose reduction in CT imaging for acute stroke. Radiation doses in three types of CT imaging (i.e. non-contrast-enhanced CT, CT perfusion (CTP) and CT angiography (CTA)) were measured with an in-phantom dosimetry system for 4-, 16-and 64-detector CT scanners in 5 hospitals. To examine the relationship between image quality and radiation dose in CTA, image contrast-to-noise ratio was evaluated. Doses to the brain, lens, salivary glands and local skin obtained with scan protocols in routine use were: 42-71 mGy, 30-88 mGy, 3.9-7.3 mGy and 40-97 mGy in non-contrast-enhanced CT; 41-75 mGy, 9.9-10 mGy, 1.5-2.1 mGy and 107-143 mGy in CTP; and 8.2-55 mGy, 26-69 mGy, 2.0-73 mGy and 32-72 mGy in CTA. For the combination of these CT examinations, on average a patient would receive 236 mGy for the maximum local skin dose and 4.2 mSv for the effective dose evaluated by the International Commission on Radiological Protection (ICRP) 103. Effective doses in CTP in this study were less than those obtained with representative protocols of Western countries. Average effective doses in each CT examination were not more than 1.5 mSv. The use of reduced kV and a narrow scan range would be effective in dose reduction of CTA and CTP, and intermittent scanning would be essential in CTP. Although lens and maximum local skin doses were far less than the thresholds for deterministic effects, since radiation risks would be increased in repeated CT examinations, efforts should be devoted to dose reduction in stroke CT examinations. Most patients with suspected stroke undergo either CT or MRI as the initial diagnostic examination [1,2]. MRI has some advantages over CT in depicting stroke lesions; however, the provision of MR scanners in general hospitals is still low, an examination takes more time and patients with pacemakers cannot undergo MRI examinations. While CT techniques carry the risk of radiation exposure, CT scanners are nearly always available [3] and scans can be done quickly. Schramm et al [4] have reported that CT images obtained by the combination of various CT examinations allow diagnostic assessment of acute stroke with a quality comparable with that of stroke MRI. So CT examination has some advantages for the diagnosis of acute stroke patients who have no time to lose.The diagnostic CT examination for acute stroke generally requires three imaging techniques: non-contrast-enhanced CT of the head; CT perfusion (CTP); and CT angiography (CTA) of intracranial vessels. In these CT examinations the local skin dose in CTP might be considerably high. In a previous study we reported that the maximum skin dose was as high as 712 mGy, 13 times higher than that in non-contrast-enhanced CT of the head [5]. Although the latest multidetector-row CT (MDCT) scanners have a dose reduction function of intermittent scanning or shuttle scanning, detailed patient doses using the function have not been reported.The CTA technique has been developing with great potential owing to high scan speed and ...

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Section: Tube Voltage and Effective Masmentioning

confidence: 81%

Radiation dose evaluation in multidetector-row CT imaging for acute stroke with an anthropomorphic phantom

Yamauchi-Kawara

Fujii²,

Aoyama³

et al. 2010

BJR

View full text Add to dashboard Cite

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“…-cerebral CT angiography [30,31] -pulmonary CT angiography [32][33][34] -aorto-iliac CT angiography [8,35,36] • Lowering of the tube voltage and/or tube current for non-contrast CT [37] • Reduction of the total number of imaging phases (e.g. split-bolus technique) [38,39] • Adjustment of image quality reference values of the automatic tube current modulation for oversized patients [40] • Reduction of the tube voltage and/or tube current for survey CT [41,42] • Positioning of the X-ray tube below the table for the survey CT (e.g.…”

Section: Resultsmentioning

confidence: 99%

An education and training programme for radiological institutes: impact on the reduction of the CT radiation dose

et al. 2011

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Objectives To establish an education and training programme for the reduction of CT radiation doses and to assess this programme's efficacy. Methods Ten radiological institutes were counselled. The optimisation programme included a small group workshop and a lecture on radiation dose reduction strategies. The radiation dose used for five CT protocols (paranasal sinuses, brain, chest, pulmonary angiography and abdomen) was assessed using the dose-length product (DLP) before and after the optimisation programme. The mean DLP values were compared with national diagnostic reference levels (DRLs). Results The average reduction of the DLP after optimisation was 37% for the sinuses (180 vs. 113 mGycm, P< 0.001), 9% for the brain (982 vs. 896 mGycm, P<0.05), 24% for the chest (425 vs. 322 mGycm, P<0.05) and 42% for the pulmonary arteries (352 vs. 203 mGycm, P<0.001). No significant change in DLP was found for abdominal CT. The post-optimisation DLP values of the sinuses, brain, chest, pulmonary arteries and abdomen were 68%, 10%, 20%, 55% and 15% below the DRL, respectively. Conclusions The education and training programme for radiological institutes is effective in achieving a substantial reduction in CT radiation dose.

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“…However, recent research has demonstrated the potential use of dual-energy CT (DECT) and different tube voltage/ tube current protocols for the characterization of tissue components and organ perfusion as well as for dose reduction [5][6][7][8][9][10][11]. In addition there is evidence that suggests the usefulness of DECT for comprehensive imaging of coronary artery disease and the evaluation of myocardial perfusion [12,13].…”

Section: Introductionmentioning

confidence: 99%

Dose levels at coronary CT angiography—a comparison of Dual Energy-, Dual Source- and 16-slice CT

et al. 2010

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Purpose To compare the dose estimates and image quality of Dual Energy CT (DECT), Dual Source CT (DSCT) and 16-slice CT for coronary CT angiography (cCTA). Methods Sixty-eight patients were examined with 16 -slice MDCT (group 1), 68 patients with DSCT (group 2) and 68 patients using DSCT in dual energy mode (DECT group 3). CT dose index volume, dose length product, effective dose, signal-to-noise, and contrast-to-noise ratio were compared. Subjective image quality was rated by two observers, blinded to technique. Results The mean estimated radiation dose of all patients investigated on a 16 -slice MDCT was 12±3.59 mSv, for DSCT in single energy 9.8±4.77 mSv and for DECT 4.54± 1.87 mSv. Dose for CTA was significantly lower in group 3 compared to group 1 and 2. The image noise was significantly lower in Group 2 in comparison to group 1 and group 3. There was no significant difference in diagnostic image quality comparing DECT and DSCT. Conclusion cCTA shows better dose levels at both DECT and DSCT compared to 16-slice CT. Further, DECT delivers significantly less dose than regular DSCT or single source single energy cCTA while maintaining diagnostic image quality.

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Circle of Willis at CT Angiography: Dose Reduction and Image Quality—Reducing Tube Voltage and Increasing Tube Current Settings

Abstract: In head phantoms, lower tube voltage improved SNR at equal radiation doses. For CT angiography of the circle of Willis, this translated into superior image quality at 90 kVp.

Cited by 145 publications

References 14 publications

Radiation dose evaluation in multidetector-row CT imaging for acute stroke with an anthropomorphic phantom

Radiation dose evaluation in multidetector-row CT imaging for acute stroke with an anthropomorphic phantom

An education and training programme for radiological institutes: impact on the reduction of the CT radiation dose

Dose levels at coronary CT angiography—a comparison of Dual Energy-, Dual Source- and 16-slice CT

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