AJR: Cone-Beam CT is beneficial adjunct to mammo

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Cone-beam breast CT can be used to image the entire breast with sufficient spatial and contrast resolution for the detection of masses and calcifications at a radiation dose within the range of conventional mammography, found a study published in the August issue of the American Journal of Roentgenology.

Avice M. O'Connell, MD, of the department of imaging sciences at the University of Rochester Medical Center in Rochester, N.Y., and colleagues conducted the pilot study to evaluate the radiation dose, breast coverage and image quality of cone-beam breast CT compared with a conventional mammographic exam.

The researchers recruited 23 women, each 40 years of age or older,  presenting with a final BI-RADS assessment category one or two lesions on conventional mammograms within the previous six months at a hospital imaging center from July 2006 through August 2008. Each patient was imaged with a flat-panel detector-based cone-beam CT system and the cone-beam breast CT image data sets and the corresponding mammograms were reviewed by three qualified mammographers.

O’Connell and colleagues independently reviewed the mammograms and cone-beam breast CT images side by side in order to make comparisons of radiation dose, breast tissue coverage and image quality, including detectability of masses and calcifications. Image quality analysis was focused on the concordance of cone-beam breast CT with conventional mammography for mammographic findings. In addition, each patient involved in the study responded to a questionnaire on multiple parameters, including comfort of the cone-beam breast CT exam compared with mammography.

The researchers determined that for radiation dose, the average glandular radiation dose ranged from 2.2 mGy to 15 mGy for a conventional mammographic exam compared with 4 mGy to 12.8 mGy for cone-beam breast CT.   

However, for heterogeneously dense and extremely dense breasts, the difference between the mean dose of conventional mammography and that of cone-beam breast CT was not statistically significant, the authors said.

For cone-beam breast CT, they found that breast tissue coverage was statistically significantly better when compared to mammography in the lateral, medial and posterior aspects. Conversely, O'Connell and colleagues found that mammography had statistically significantly better coverage than cone-beam breast CT in the axilla and axillary tail.

The overall interobserver agreement on type of findings was 77.2 percent, size of findings, 84.8 percent and location of findings was 78.3 percent, offered the researchers, who noted that most calcifications and all masses detected with mammography were also detected with cone-beam breast CT, with an interobserver agreement on cone-beam breast CT of 83.7 percent in the detectability of imaging findings.

Noting that the method is intended for use as an adjunctive diagnostic tool after conventional mammography, O’Connell and colleagues concluded: “Cone-beam breast CT has unique advantages for breast imaging and is comparable to conventional mammography in terms of dose, coverage, and detectability of image findings.”