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 of FordMartin et al. (2014) also shows that X-ray mammogram screening outputs the detection of more than 90% of breast cancers. In short, a mammogram is a noninvasive x-ray which produces a two-dimensional breast image. X-ray mammogram is very helpful in detecting small breast cancers which could be difficult to be identified in a physical examination. However, there is still 10% to 13% of breast cancer that is not detected by mammogram—for instance, mammogram images are not so promising when scanned breast has dense tissue, which drives radiologists to use other techniques. After a mammogram screening, if anything irregular, such as a mass, abnormal skin, or enlarged lymph nodes, is found on the breast image, then additional imaging examinations could be done, which includes another X-ray mammogram, magnetic resonance imaging, or an ultrasound imaging of the breast. An ultrasound breast imaging helps determine if the mass is a solid lump, and if it is, a biopsy is to be done for final definitive diagnosis. All in all, for the detection of breast cancer, major well-established imaging techniques include X-ray mammogram, MRI, and ultrasound, and there are also novel techniques in the process of development.
While X-ray mammogram is a well-established imaging technique for diagnosing breast cancer, it has its limitations and therefore researchers are actively seeking enhancement, variations or even replacement 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. Also, screening mammogram has a high false-positive rate: on average, 75% of suspicious tissue irregularity, detected by mammogram, turns out to be benign from breast biopsies. There are other shortcomings of X-ray mammogram such as uncomfortable experience when breast being compressed during a screening and even inducement of breast cancer since when breast is exposed to radiation it is possible to get ionized.
Provided with these drawbacks, it is necessary to develop new imaging modalities and techniques which could complement and improve X-ray mammography. In the article presented by Kosus et al. (2010), there are three techniques proposed: digital mammography, breast ultrasonography, and digital infrared thermal imaging. First of all, digital mammography enhances standard X-ray mammography on some of its limitations and thus has been increasingly used for breast screening. Among patients with dense breast tissue, the detection of cancer is difficult through standard mammogram since the normal dense breast tissue surrounding the carcinoma would have similar X-ray absorption. Correspondingly, digital breast mammography works better since it is able to selectively optimize the contrast in the area of dense tissue. This imaging modality has advantage in women who genetically predisposed in breast cancer. Moreover, as the application of computer and programming increases, it is extremely helpful to use digital mammography for image quality, data storing, and data transfer. A constraint on digital breast mammogram is its high initial expense. Secondly, the article mentions breast ultrasonography.
As it is difficult to distinguish between cysts and solid lesions based on mammography alone, ultrasound comes to the stage at this point. Breast ultrasound is an powerful approach to distinguish breast masses and it is also relatively less pricy. Moreover, in ultrasound screening, there is no exposure to ionizing radiation, which is a significant point for patients with pregnance and the youth. However, one limitation of ultrasound is that, with ultrasound screening only, small calcifications cannot be seen easily. Therefore, a combination of mammography and breast ultrasonography works as a standard breast imaging method for detection and evaluation of breast cancer. At last, digital infrared thermal imaging (DITI) serves as an addition to the diagnosis of breast cancer. This technique is unique since it provides physical information that could not be easily measured by other imaging methods such as X-ray, ultrasound, and so on. In short, DITI is a combination of measurements of body surface temperature and subtle changes in physical conditions—these changes might be caused by carcinomas. DITI overcomes constraints provided by dense breast tissues. Moreover, it does not involve painful compression of breast, which could improve patients’ experience in breast screening.
As an essential tool for breast imaging, magnetic resonance imaging (MRI) plays multiple roles, such as determining the stage, monitoring of adjuvant chemo-therapy, and evaluating breast implants, in clinical environment. MRI has many advantages. For example, it has excellent sensitivity in breast cancer diagnosis and could also avoid unnecessary biopsies—which is a pain for all patients—when suspicious mass is found by mammogram or ultrasound. In the article presented 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. First of all, currently DCE-MRI has the highest imaging sensitivity among all imaging modalities and helps identify benign and malignant (cancer) lesions. DCE-MRI is also considered to be the foundation of most MRI protocol. Moreover, when breast cancer is detected, DCE-MRI can also be used to simultaneously assess disease extent, satellite lesions, and so on.
Furthermore, DCE-MRI seems working better than mammography and ultrasound on the evaluation of malignant lesions such as invasive lobular cancer and ductal carcinoma. However, it is still controversial whether DCE-MRI improves overall survival or disease-free rate or not. When magnetic field is increased, ultra-high field MRI can be realized, and therefore it has a generic name “ultra-high field MRI”. This technique significantly increases the intensity of signals relative to noises, which could be used to improve spatial resolution of images. However, ultra-high field MRI has limitations such as increased specific absorptions rate and greater transmit field inhomogeneity (Leithner, D., et al. 2018) which can impair the quality of images. It is also helpful to think about the efficiency of MRI when the actual screening is taking place. According to the article presented by Mango et al. (2015), because standard MRI requires high cost and takes a longer time for examination than X-ray mammography, in order to routinely use MRI, researchers seek to shorten the examination time and therefore lower the cost.
To summarize, standard X-ray mammography has its limitations in dense breast tissues as well as variability in interpretation of mammogram, and thus it needs other techniques for complement and enhancement: digital breast mammography is an enhanced version of standard mammography; ultrasound works as a complement to it; digital infrared thermal imaging serves as an addition to X-ray mammography. Ultrasound has outstanding ability to define breast mass and relatively low cost. Nonetheless, one drawback of ultrasound is its incapability of detecting calcifications. At last, MRI has advantages on imaging sensitivity and evaluation of malignant lesions, but it also has limitations such as patients’ discomfort and long screening time. In fact, every imaging has its limitations and therefore needs other techniques to complement and enhance.
An imaging modality involves multiple imaging techniques which complement or enhance one another and work better as a whole. Since the essential tools, such as X-ray mammogram, ultrasound, and MRI, are well established, future development should focus on supporting techniques which could compensate for the limitations of the essential ones. An excellent example can be found in an article presented by Zimmerman et al. (2017). The imaging modality discussed in this article is composed of X-ray mammogram and diffuse optical tomography (DOT). X-ray image works as a structural guide to help build the image reconstruction; on the other hand, DOT provides higher resolution, which assists on differentiating breast mass. Moreover, DOT uses non-invasive near-infrared laser, which addresses some patients’ concerns about tissue ionization.
- 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.
- 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.
- 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.
- 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
- 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