Essential Breast Cancer Screening Techniques and their Complements

It is with great distress that each year a large number of females suffer and die from breast cancer. Medicine practitioners and researchers have been striving to save lives from breast cancer, and how they manage to do this includes two major parts—diagnosis and treatment. What comes first on the stage of diagnosis is the detection of tumor. Thus, the development of breast imaging techniques is at the highest priority for diagnosing breast cancer, and individuals’ focus is on earlier detection of cancer.

There are three essential breast imaging techniques in the field—X-ray mammogram, ultrasound, and MRI, each of which plays a crucial role in different stages of cancer. While these essential tools dominate the industry of breast imaging, none of them is perfect. Each imaging technique has its limitations: X-ray mammogram has high false rates when applied onto dense breast tissue, and its ionizing nature concerns many patients; ultrasound is incapable of detecting small calcifications; MRI can have low image quality when field intensity is increased, and its long screening time discomforts many patients. Therefore, researchers are seeking to develop complementary imaging technique which compensate for the limitations of the essential techniques. Some promising examples are digital X-ray mammogram, digital infrared thermal imaging (DITI), and diffuse optical tomography (DOT).

Breast cancer is listed as the second leading cause of cancer death among women according to an article presented by FordMartin et al. (2014). Before the actual treatment on breast cancer, the most significant step is diagnosis—the earlier the diagnosis is, the better: earlier detection of the tumor is likely to represent a cancer in an earlier stage and therefore both physicians and patients would have more time to work on treatment. As such, in order to detect tumors, the diagnosis of breast cancer has to utilize breast imaging techniques—some well-known ones are X-ray mammography, functional magnetic resonance imaging (MRI). Each imaging technique plays its own role corresponding to the stage of tumor, and therefore for many cases a complete diagnosis would involve more than one imaging technique. The following essay will briefly discuss the breast cancer and then move to imaging techniques and modalities; there is going to be comparison between different imaging modalities; at the end, potential suggestions to the future development of imaging techniques will be provided.

As one of the most severe threats to women, breast cancer has been causing a large number of death every year. In 2013, the American Cancer Society estimated that about 39,620 American women would die of breast cancer (FordMartin et al. 2014). Breast cancer puts high risk on women, and thus earlier diagnosis of tumor is significant. Nevertheless, it is fortunate that, since around 1989, death rates from breast cancer have been decreasing, which is considered to be the result of increasingly earlier detection through screening. According to Kosus et al. (2010), breast cancer has 5 stages, and the 10-year survival rate for these 5 stages, from the first to the fourth, ranges from 95% to 7 %. Therefore, earlier detection is a priority in the diagnosis of breast cancer.

The article by FordMartin et al. (2014) shows that X-ray mammogram screening detects more than 90% of breast cancers. In short, a mammogram is a noninvasive x-ray that produces a two-dimensional breast image. An X-ray mammogram is very helpful in detecting small breast cancers, which can be difficult to identify in a physical examination. However, there is still 10% to 13% of breast cancer that is not detected by mammogram—mammogram images, for instance, do not work well when the scanned breast has dense tissue. This issue necessitates the use of other techniques by radiologists. If anything irregular, such as a mass, abnormal skin, or enlarged lymph nodes, is found on the breast image after a mammogram screening, additional imaging examinations can be done. These may include another X-ray mammogram, magnetic resonance imaging (MRI), or an ultrasound imaging of the breast. Ultrasound breast imaging helps determine if the mass is a solid lump and, if it is, a biopsy must be performed for a definitive diagnosis. Altogether, for the detection of breast cancer, major well-established imaging techniques include X-ray mammogram, MRI, and ultrasound, and there are also novel techniques currently under development.

While the X-ray mammogram is a well-established imaging technique for diagnosing breast cancer, it has its limitations. Therefore, researchers are actively seeking enhancements, variations, or even replacements of it or other imaging modalities. According to the article presented by Kosus et al. (2010), despite the fact that standard mammogram functions well in detecting tumors and defining breast cancer, it has a false-negative rate ranging from 4% to 34%. Moreover, for patients with dense breast tissue, X-ray mammography is less sensitive. The screening mammogram also has a high false-positive rate: on average, 75% of suspicious tissue irregularity, detected by mammogram, turns out to be benign when subjected to breast biopsies. Other shortcomings of X-ray mammogram include the uncomfortable experience of having the breast compressed during a screening, as well as the risk of inducing breast cancer due to exposure to radiation.

Given these drawbacks, it's necessary to develop new imaging modalities and techniques to complement and improve X-ray mammography. In the article presented by Kosus et al. (2010), three techniques are proposed: digital mammography, breast ultrasonography, and digital infrared thermal imaging. Digital mammography enhances standard X-ray mammography and has been increasingly used for breast screening. Among patients with dense breast tissue, traditional mammograms struggle with cancer detection due to similar X-ray absorption by normal dense breast tissue and carcinoma. In contrast, digital breast mammography is more effective as it selectively optimizes the contrast in areas of dense tissue. This imaging modality proves beneficial for women genetically predisposed to breast cancer. Additionally, as computer and programming use increases, digital mammography becomes extremely useful for image quality, data storage, and data transfer. However, digital breast mammography comes with high initial expenses. The article also mentions breast ultrasonography.

As it is difficult to distinguish between cysts and solid lesions based on mammography alone, ultrasound enters the equation at this point. Breast ultrasound is a powerful approach to distinguishing breast masses, and it is also relatively less costly. Moreover, in ultrasound screening, there is no exposure to ionizing radiation, which is a significant point for patients who are pregnant or young. However, one limitation of ultrasound is that small calcifications are challenging to see with ultrasound screening only. Therefore, a combination of mammography and breast ultrasonography is a standard breast imaging method for detection and evaluation of breast cancer. Lastly, digital infrared thermal imaging (DITI) serves as an additional tool in the diagnosis of breast cancer. This technique is unique because it provides physical information that other imaging methods, such as X-ray and ultrasound, cannot measure easily. To summarize, DITI combines measurements of body surface temperature and subtle physical changes that carcinomas may cause. DITI overcomes constraints provided by dense breast tissues and does not involve causing painful compression of the breast, which could improve patients’ experience during breast screening.

Magnetic resonance imaging (MRI), an essential tool for breast imaging, plays various roles, such as determining the stage, monitoring adjuvant chemotherapy, and evaluating breast implants, in a clinical environment. MRI has many advantages. For instance, it has an exceptional sensitivity in diagnosing breast cancer and could also avoid unnecessary biopsies—which cause patients discomfort—when a suspicious mass is detected by mammogram or ultrasound. In an article by Leithner, D., et al. (2018), three well-established imaging modalities of MRI are introduced: dynamic contrast-enhanced MRI (DCE-MRI), ultra-high field MRI, and abbreviated MRI. Above all, DCE-MRI currently possesses the highest imaging sensitivity among all imaging modalities, facilitating the identification of benign and malignant (cancer) lesions. DCE-MRI is also considered the cornerstone of most MRI protocols. Furthermore, when breast cancer is detected, DCE-MRI can be used to simultaneously assess the disease extent, satellite lesions, etc.

DCE-MRI seems to work better than mammography and ultrasound in evaluating malignant lesions such as invasive lobular cancer and ductal carcinoma. However, it remains controversial whether DCE-MRI improves overall survival or disease-free rates. When the magnetic field is increased, ultra-high field MRI can be realized, thus lending it the generic name "ultra-high field MRI". This technique significantly increases the intensity of signals relative to noise and can be used to improve the spatial resolution of images. However, ultra-high field MRI has limitations, including increased specific absorption rates and greater transmit field inhomogeneity (Leithner, D., et al. 2018), which can impair the quality of images. It is also essential to consider the efficiency of MRI when actual screening takes place. According to an article by Mango et al. (2015), because a standard MRI is costly and takes longer than X-ray mammography, researchers are looking to shorten the examination time to reduce costs.

In summary, standard X-ray mammography has its limitations in dense breast tissues and in the variability of mammogram interpretation, necessitating other complementary and enhancing techniques. Digital breast mammography is an enhanced version of standard mammography, while ultrasound serves as a complement; digital infrared thermal imaging acts as an addition to X-ray mammography. Ultrasound has an excellent ability to define breast mass and is relatively low cost. However, a drawback of ultrasound is its inability to detect calcifications. Finally, MRI offers advantages in imaging sensitivity and the evaluation of malignant lesions, but it also has limitations such as patient discomfort and lengthy screening time. Indeed, every imaging technique has its limitations, thus requiring other techniques for complement and enhancement.

Imaging modalities involve multiple techniques which complement or enhance each other and are more effective as a whole. With essential tools such as X-ray mammograms, ultrasounds, and MRIs being well established, future development should focus on supporting techniques that can compensate for their limitations. An excellent example can be found in an article by Zimmerman et al. (2017). The imaging modality discussed in this article is composed of X-ray mammograms and diffuse optical tomography (DOT). The X-ray image serves as a structural guide to assist with image reconstruction; on the other hand, DOT provides higher resolution, facilitating the differentiation of breast mass. Furthermore, DOT employs a non-invasive near-infrared laser, addressing some patients' concerns about tissue ionization.

References

1. FordMartin, Paula, and Tish Davidson. 'Breast Cancer.' The Gale Encyclopedia of Alternative Medicine, edited by Laurie J. Fundukian, 4th ed., vol. 1, Gale, 2014, pp. 347-354. Health & Wellness Resource Center, http://link.galegroup.com/apps/doc/CX3189900134/HWRC?u=mlin_b_northest&sid=HWRC&xid=fd4af691. Accessed 24 Oct. 2018.
2. Kosus, Nermin, et al. 'Comparison of standard mammography with digital mammography and digital infrared thermal imaging for breast cancer screening / Meme kanseri taramasinda standart mamografi ve dijital mamografi ve dijital infrared termal goruntulemenin karsilastirilmasi.' Journal of the Turkish-German Gynecological Association, vol. 11, no. 3, 2010, p. 152+. Health Reference Center Academic, http://link.galegroup.com/apps/doc/A305455348/HRCA?u=mlin_b_northest&sid=HRCA&xid=8aa6cd2c. Accessed 24 Oct. 2018.
3. Leithner, D., et al. 'Clinical role of breast MRI now and going forward.' Clinical Radiology, vol. 73, no. 8, 2018, p. 700. Health Reference Center Academic, http://link.galegroup.com/apps/doc/A544585676/HRCA?u=mlin_b_northest&sid=HRCA&xid=d1d99503. Accessed 24 Oct. 2018.
4. Mango Vl, Morris EA, David Dershaw D, et al. “Abbreviated protocol for breast MRI: are multiple sequences needed for cancer detection?” European Journal of Radiology, vol. 84, 2015, p. 65-70. ScienceDirect https://www.sciencedirect.com/science/article/pii/S0720048X14004690 Accessed 25 Oct. 2018
5. Zimmerman et al. “Multimodal breast cancer imaging using coregistered dynamic diffuse optical tomography and digital breast tomosynthesis.’’ Journal of Biomedical Optics, vol.22, no. 4, April 2017, https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-22/issue-4/046008/Multimodal-breast-cancer-imaging-using-coregistered-dynamic-diffuse-optical tomography/10.1117/1.JBO.22.4.046008.full. Accessed 01 Nov. 2018  

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