Impact of iodine concentration and scan parameters on image quality, contrast enhancement and radiation dose in thoracic CT

Abstract Background We investigated the impact of varying contrast medium (CM) densities and x-ray tube potentials on contrast enhancement (CE), image quality and radiation dose in thoracic computed tomography (CT) using two different scanning techniques. Methods Seven plastic tubes containing seven different CM densities ranging from of 0 to 600 HU were positioned inside a commercial chest phantom with padding, representing three different patient sizes. Helical scans of the phantom in single-source mode were obtained with varying tube potentials from 70 to 140 kVp. A constant volume CT dose index (CTDIvol) depending on phantom size and automatic dose modulation was tested. CE (HU) and image quality (contrast-to-noise ratio, CNR) were measured for all combinations of CM density and tube potential. A reference threshold of CE and kVp was defined as ≥ 200 HU and 120 kVp. Results For the medium-sized phantom, with a specific CE of 100–600 HU, the diagnostic CE (200 HU) at 70 kVp was ~ 90% higher than at 120 kVp, for both scan techniques (p < 0.001). Changes in CM density/specific HU together with lower kVp resulted in significantly higher CE and CNR (p < 0.001). When changing only the kVp, no statistically significant differences were observed in CE or CNR (p ≥ 0.094), using both dose modulation and constant CTDIvol. Conclusions For thoracic CT, diagnostic CE (≥ 200 HU) and maintained CNR were achieved by using lower CM density in combination with lower tube potential (< 120 kVp), independently of phantom size.

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Effect of Lowering Tube Potential and Increase Iodine Concentration of Contrast Medium on Radiation Dose and Image Quality in Computed Tomography Pulmonary Angiography Procedure: A Phantom Study

Tanzania Journal of Science ◽

10.4314/tjs.v47i3.29 ◽

2021 ◽

Vol 47 (3) ◽

pp. 1211-1224

Author(s):

Justin E Ngaile ◽

Peter K Msaki ◽

Evarist M Kahuluda ◽

Furaha M Chuma ◽

Jerome M Mwimanzi ◽

...

Keyword(s):

Computed Tomography ◽

Image Quality ◽

Radiation Dose ◽

Contrast Medium ◽

Iodine Concentration ◽

Pulmonary Angiography ◽

Computed Tomography Pulmonary Angiography ◽

Iodinated Contrast ◽

Tube Potential ◽

Tube Current

The aim of the study was to examine the effect of lowering tube potential and increase iodine concentration on image quality and radiation dose in computed tomography pulmonary angiography procedure. The pulmonary arteries were simulated by three syringes. The syringes were filled with 1:10 diluted solutions of 300 mg, 350 mg and 370 mg of iodine per millilitre concentration in three water-filled phantoms simulating thin, intermediate and thick patients. The phantoms were scanned at 80 kVp, 110 kVp and 130 kVp and 0.6 second rotation time using a 16 slice computed tomography (CT) scanner. The tube current was either fixed at 80, 100, 200, 250 and 300 mA or automatically adjusted with quality reference tube current-time product (mAsQR). In comparison with 130 kVp, images acquired at 80 kVp and 110 kVp, respectively, showed 76.2% to 99% and 19% to 26% enhancement in CT attenuation of iodinated contrast material. A volume CT dose index (CTDIvol) reduction by 35.3% was attained in small phantom with the use of 80 kVp, while in the medium phantom, a CTDIvol reduction by 29.9% was attained with the use of 110 kVp instead of 130 kVp. In light of the above, lowering tube potential and increase iodinated CM could substantially reduce the dose to small-sized adults and children. Keywords: Angiography; Computed tomography; Low tube potential; Iodinated contrast medium; Radiation dose

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The impact of pediatric-specific dose modulation curves on radiation dose and image quality in head computed tomography

Pediatric Radiology ◽

10.1007/s00247-015-3398-5 ◽

2015 ◽

Vol 45 (12) ◽

pp. 1814-1822 ◽

Cited By ~ 5

Author(s):

Joana Santos ◽

Shane Foley ◽

Graciano Paulo ◽

Mark F. McEntee ◽

Louise Rainford

Keyword(s):

Computed Tomography ◽

Image Quality ◽

Radiation Dose ◽

Dose Modulation ◽

The Impact ◽

Head Computed Tomography

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Using 100- instead of 120-kVp computed tomography to diagnose pulmonary embolism almost halves the radiation dose with preserved diagnostic quality

Acta Radiologica ◽

10.3109/02841850903505222 ◽

2010 ◽

Vol 51 (3) ◽

pp. 260-270 ◽

Cited By ~ 24

Author(s):

Peter Björkdahl ◽

Ulf Nyman

Keyword(s):

Computed Tomography ◽

Pulmonary Embolism ◽

Image Quality ◽

Radiation Dose ◽

Effective Dose ◽

Ct Number ◽

Subjective Image Quality ◽

Diagnostic Quality ◽

X Ray ◽

Tube Potential

Background: Concern has been raised regarding the mounting collective radiation doses from computed tomography (CT), increasing the risk of radiation-induced cancers in exposed populations. Purpose: To compare radiation dose and image quality in a chest phantom and in patients for the diagnosis of pulmonary embolism (PE) at 100 and 120 peak kilovoltage (kVp) using 16-multichannel detector computed tomography (MDCT). Material and Methods: A 20-ml syringe containing 12 mg I/ml was scanned in a chest phantom at 100/120 kVp and 25 milliampere seconds (mAs). Consecutive patients underwent 100 kVp ( n = 50) and 120 kVp ( n = 50) 16-MDCT using a “quality reference” effective mAs of 100, 300 mg I/kg, and a 12-s injection duration. Attenuation (CT number), image noise (1 standard deviation), and contrast-to-noise ratio (CNR; fresh clot = 70 HU) of the contrast medium syringe and pulmonary arteries were evaluated on 3-mm-thick slices. Subjective image quality was assessed. Computed tomography dose index (CTDIvol) and dose–length product (DLP) were presented by the CT software, and effective dose was estimated. Results: Mean values in the chest phantom and patients changed as follows when X-ray tube potential decreased from 120 to 100 kVp: attenuation +23% and +40%, noise +38% and +48%, CNR −6% and 0%, and CTDIvol −38% and −40%, respectively. Mean DLP and effective dose in the patients decreased by 42% and 45%, respectively. Subjective image quality was excellent or adequate in 49/48 patients at 100/120 kVp. No patient with a negative CT had any thromboembolism diagnosed during 3-month follow-up. Conclusion: By reducing X-ray tube potential from 120 to 100 kVp, while keeping all other scanning parameters unchanged, the radiation dose to the patient may be almost halved without deterioration of diagnostic quality, which may be of particular benefit in young individuals.

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