Optical diffusion breast imaging improves the diagnostic accuracy of conventional ultrasound in distinguishing between malignant and benign breast lesions, according to a new study published in the September issue of the American Journal of Roentgenology.
Researchers from Asan Medical Center in South Korea evaluated the diagnostic accuracy of optical diffusion breast imaging in patients who underwent conventional ultrasound followed by surgery or biopsy. They found that using optical diffusion improved ultrasound's specificity, positive predictive value, and accuracy.
Breast ultrasound is a commonly used diagnostic tool for further evaluation of abnormal mammographic findings, but its specificity leaves a bit to be desired, according to lead author Dr. Jin Hee Moon and colleagues.
"The partially overlapping appearance of benign and malignant lesions on breast ultrasound can make it difficult for radiologists to make a confident diagnosis," the authors wrote (AJR, September 2011, Vol. 197:3, pp. 1-8).
Optical diffusion imaging uses diffused light in the near-infrared spectrum. Because it calculates the total hemoglobin and oxygen saturation levels of tumors as markers of tumor angiogenesis or hypoxia, it can provide supplemental information to conventional ultrasound results that helps clinicians determine the status of a tumor.
Moon and colleagues performed optical diffusion breast imaging after conventional ultrasound on 193 women with 217 lesions, using a handheld probe that consisted of both an ultrasound transducer and a near-infrared source-detector light guided by optical fibers. The ultrasound transducer was used to find the targeted lesion, and then the probe's mode was shifted to optical diffusion imaging. On the outside of the probe, the optical system included two light sources and nine light emission fibers, while the receiving side of the probe featured 10 photomultiplier tubes that detect scattered light from tissue.
All patients also underwent ultrasound-guided core needle biopsy or surgery. One of a team of six radiologists reviewed the conventional ultrasound features of each lesion, assessed its BI-RADS category, and reviewed optical diffusion imaging results.
Of the 217 lesions, 108 were malignant and 109 were benign. Malignant lesions included the following:
- 86 invasive ductal carcinomas
- 15 ductal carcinomas in situ
- 1 invasive lobular cancer
- 2 mucinous cancers
- 2 tubular cancers
- 1 metaplastic cancer
- 1 microinvasive ductal carcinoma
Using conventional ultrasound results, the study's interpreting radiologists categorized 30 lesions as BI-RADS 3 (probably benign), 79 as BI-RADS 4A (indeterminate), 25 as BI-RADS 4B (intermediate suspicion of malignancy), 11 as BI-RADS 4C (moderate concern for malignancy), and 72 as BI-RADS 5 (highly likely to be malignant).
Moon's team found that using optical diffusion breast imaging contributed to ultrasound's performance, particularly in its specificity and accuracy.
Comparison of optical diffusion imaging with breast ultrasound
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| PPV = positive predictive value; NPV = negative predictive value |
When the researchers compared the total hemoglobin concentration level and oxygen saturation level of benign and malignant lesions, they found that the mean hemoglobin value was 0.144 mmol/L in benign lesions and 0.262 mmol/L in malignant lesions, a statistically significant difference (p < 0.0001). The mean oxygen saturation value was 0.971 mmol/L in benign lesions and 0.975 mmol/L in malignant lesions, which was not statistically significant (p = 0.953).
"These results show that the total hemoglobin concentration level is a more useful measure than oxygen saturation level for the differentiation of benign from malignant disease," Moon and colleagues wrote.
Compared with mammography or MRI, ultrasound has proved to be the best match for optical diffusion imaging, due to the modality's good resolution and high performance-cost ratio, according to the authors.
"Our results show that optical diffusion imaging may be helpful to radiologists for differentiating a lesion detected on conventional ultrasound," they wrote.
