Korean J Radiol.  2013 Jun;14(3):525-531. 10.3348/kjr.2013.14.3.525.

Digital Tomosynthesis of the Chest: Comparison of Patient Exposure Dose and Image Quality between Standard Default Setting and Low Dose Setting

• Hwang HS
• Chung MJ
• Lee KS

• KMID: 1705470
• DOI: http://doi.org/10.3348/kjr.2013.14.3.525

Abstract

OBJECTIVE
To determine the optimum low dose (LD) digital tomosynthesis (DT) setting, and to compared the image quality of the LD DT with that of the standard default (SD) DT.
MATERIALS AND METHODS
Nine DT settings, by changing tube voltage, copper filter, and dose ratio, were performed for determining the LD setting. Among combinations of DT setting, a condition providing the lowest radiation dose was determined. Eighty artificial nodules less than 1 cm in diameter (subcentimeter nodules: 40, micronodules less than 4 mm: 40) were attached to a Styrofoam and a diaphragm of the phantom. Among these, 38 nodules were located at the periphery of the lung (thin area) and 42 nodules were located at the paravertebral or sub-diaphragmatic area (thick area). Four observers counted the number of nodules detected in the thick and thin areas. The detection sensitivity in SD and LD settings were calculated separately. Data were analyzed statistically.
RESULTS
The lowest LD setting was a combination of 100 kVp, 0.3 mm additional copper filter, and a 1 : 5 dose ratio. The effective dose for the LD and SD settings were 62 microSv and 140 microSv, separately. A 56.7% dose reduction was achieved in the LD setting compared with the SD setting. Detection sensitivities were not different between the SD and the LD settings except between observers 1 and 2 for the detection of micronodules in the thick area.
CONCLUSION
LD DT can be effective in nodule detection bigger than 4 mm without a significant decrease in image quality compared with SD DT.

Keyword

Digital radiography; Tomographic imaging; Radiation dose

MeSH Terms

Diagnosis, Computer-Assisted/*methods
Humans
Lung Neoplasms/radiography
*Phantoms, Imaging
*Radiation Dosage
Radiographic Image Enhancement/*methods
Sensitivity and Specificity
Solitary Pulmonary Nodule/radiography

Figure

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  Fig. 1 Anthropomorphic chest phantom for evaluation of image quality. Three sets of Styrofoam embedded with artificial nodules were inserted into empty chest phantom.

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  Fig. 2 Organ doses for SD DT and LD DT settings. Doses for lung and bone marrow were decreased substantially more in LD setting than in SD setting. SD = standard default, DT = digital tomosynthesis, LD = low dose

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  Fig. 3 Images at standard dose (SD) and at low dose (LD) digital tomosynthesis. A. Magnified SD setting image. B. Magnified LD setting image. SD and LD images show clearly subcentimeter nodule (arrowhead) in paravertebral area. However, micronodule (arrow) in paravertebral area is less clearly showed in LD image (B) than on SD image (A).

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