Korean J Radiol.  2012 Dec;13(6):776-783. 10.3348/kjr.2012.13.6.776.

Which Phantom Is Better for Assessing the Image Quality in Full-Field Digital Mammography?: American College of Radiology Accreditation Phantom versus Digital Mammography Accreditation Phantom

• Song SE
• Seo BK
• Yie A
• Ku BK
• Kim HY
• Cho KR
• Chung HH
• Lee SH
• Hwang KW

• KMID: 1397509
• DOI: http://doi.org/10.3348/kjr.2012.13.6.776

Abstract

OBJECTIVE
To compare between the American College of Radiology (ACR) accreditation phantom and digital mammography accreditation phantom in assessing the image quality in full-field digital mammography (FFDM).
MATERIALS AND METHODS
In each week throughout the 42-week study, we obtained phantom images using both the ACR accreditation phantom and the digital mammography accreditation phantom, and a total of 42 pairs of images were included in this study. We assessed the signal-to-noise ratio (SNR) in each phantom image. A radiologist drew a square-shaped region of interest on the phantom and then the mean value of the SNR and the standard deviation were automatically provided on a monitor. SNR was calculated by an equation, measured mean value of SNR-constant coefficient of FFDM/standard deviation. Two breast radiologists scored visible objects (fibers, specks, and masses) with soft-copy images and calculated the visible rate (number of visible objects/total number of objects). We compared SNR and the visible rate of objects between the two phantoms and calculated the k-coefficient for interobserver agreement.
RESULTS
The SNR of the ACR accreditation phantom ranged from 42.0 to 52.9 (Mean, 47.3 +/- 2.79) and that of Digital Phantom ranged from 24.8 to 54.0 (Mean, 44.1 +/- 9.93) (p = 0.028). The visible rates of all three types of objects were much higher in the ACR accreditation phantom than those in the digital mammography accreditation phantom (p < 0.05). Interobserver agreement for visible rates of objects on phantom images was fair to moderate agreement (k-coefficients: 0.34-0.57).
CONCLUSION
The ACR accreditation phantom is superior to the digital mammography accreditation phantom in terms of SNR and visibility of phantom objects. Thus, ACR accreditation phantom appears to be satisfactory for assessing the image quality in FFDM.

Keyword

Breast; Mammography; Comparative study; Phantoms; Imaging

MeSH Terms

Accreditation
*Breast
Female
Humans
*Mammography
*Phantoms, Imaging
*Radiographic Image Enhancement
Signal-To-Noise Ratio
Societies, Medical

Figure

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  Fig. 1 Two mammography accreditation phantoms. Left is ACR Phantom (Nuclear Associates model 18-220) and right is Digital Phantom (CIRS Model 015DM). Digital Phantom has extended top edge allows ease of positioning on recumbent biopsy units. A. ACR Phantom. B. Digital Phanom. ACR = American College of Radiology

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  Fig. 2 Calculation of signal to noise ratio (SNR). Radiologist drew square-shaped region of interest (arrow) in background of phantom and then recorded mean value of SNR and standard deviation. SNR values were calculated based on following equation:

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  Fig. 3 SNR and visible rates on ACR and Digital Phantom images of week 23. A. On ACR Phantom, SNR is 45.23 and overall visible rate is 0.93 (15/16). Visible rates of fibers, specks, and masses are 1.00 (6/6), 0.80 (4/5), and 1.00 (5/5). B. On Digital Phantom, SNR is 32.47 and overall visible rate is 0.58 (7/12). Visible rates of fibers, specks, and masses are 0.50 (2/4), 0.50 (2/4), and 0.75 (3/4). Therefore, ACR Phantom is superior to Digital Phantom in terms of both SNR and visibility of phantom objects. SNR = signal to noise ratio, ACR = American College of Radiology

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