Imaging Technology

 

Cancer Imaging Technology

Published 2021

@BreastCancerHub, All Rights Reserved

Women can start getting a breast self-examination as early as 17/18 years of age. Starting at the age of 20, women can then start getting a clinical breast examination every one to three years and then every year once they hit 40 [1]. Women have the choice of getting an annual mammogram after they hit 40 but it’s recommended that all women who are at risk should get an annual mammogram after they hit 45 [2]. However, mammograms can possibly miss about half of cancers in women with dense breasts. This is where supplemental tests come into play. Supplemental tests such as 3D mammograms, tomosynthesis, breast ultrasound, breast MRI, and molecular breast imaging are all forms of tests used to aid women with dense breasts in early detection of breast cancer.

Self-Breast Exam, Clinical Breast Exam and Mammography (3D for dense breasts) are the most popularly used screening technologies in developed countries. In the U.S nearly 70% of women are screened using mammography [3]. On the other hand, it is hard to determine these numbers for developing countries, however, due to lack of data, inaccessibility to healthcare facilities in addition to taboo and ignorance existing in the urban and rural populace [4]. 

Emerging Technologies

Breast Cancer diagnostic technologies are currently advancing. As new technologies emerge, many start to question the ability of the new technologies. Although it is true that diagnostic tests may be accompanied with harm, it is still more important than ever to conduct breast screening. This not only prevents future complications, but also allows doctors to detect cancer at an early stage if possible. 

  1. An MRI uses a powerful magnetic field and radio waves to produce sophisticated visuals of the organs and tissues inside the body. An MRI can be used for breast cancer screening in women and men. However, MRIs can not distinguish cancerous tumors and non cancerous tumors..  

  2. A CT scan gets comprehensive images of the body for diagnostic purposes. It can assist doctors in locating cancer and depict things such as a tumor’s shape and size. This is the most efficient technology. However, in rare scenarios CT scans utilize ionizing radiation which may damage DNA and could minimally increase the risk of getting cancer.

  3. X-rays are efficient in finding bone problems and are typically quick and harmless. They make shadow-like visuals of bones and certain organs and tissues. Tumors typically are depicted as lighter gray than the proximal tissue. 

  4. A PET scan is a diagnostic imaging test that illustrates how your tissues and organs are functioning. A radioactive drug is used to highlight this activity. Due to a high level of chemical activity, cancer shows up as bright spots on PET scans. The disadvantages include causing complications to pregnant patients and a more expensive technology to use than others.

  5. An ultrasound assists doctors in finding tumors in specific parts of the body that don’t show up properly on x-rays. It is a fast procedure and is typically done as an outpatient. However, there are more false positives with an ultrasound.

Breast Cancer Technology Comparison 

The following are breast screening technologies that are used as an addition to mammograms or during special scenarios. These screening technologies may help strengthen the previous diagnosis and further confirm the location/size/type of the tumor. 

Mammograms: 

  • Screen-Film Mammography takes x-ray images of breasts, and focuses on a particular abnormality observed. Compared to Screen-Film Mammography, Computer Aided Detection is mainly proven to ease the process of breast screening by producing digital images. It is said that CAD improves the performance of radiologists in a cost-effective manner. However, studies are still being conducted to determine whether CAD detects breast cancer with higher accuracy [5].

Sonography: 

  • Sonography, also known as ultrasound, reflects high-frequency sound waves based on tissue properties. It is often used as a supplementary diagnostic to Mammograms to confirm, and further strengthen the screening accuracy. When a suspicious area is found during mammograms, sonography can be used to determine whether it's a solid tumor or a fluid-filled cyst [5].

Electronic Palpation: 

  • A technique in which pressure is applied to breast tissue to detect lumps and other abnormalities. Electronic Palpation is an electronic alternative to Manual Clinical Breast Exam. This technology ensures to provide an alternative to those who may find manual breast compression uncomfortable. It is a promising technology that will allow women to feel comfortable getting breast exams [5].

Elastography: 

  • Elastography identifies abnormalities in breast tissue through mechanical vibrations and imaging modalities. It is especially useful to detect hard tumors, and elasticity of breast tissue that is often missed during Mammogram screenings. Tumors that are too deep within breast tissue to be palpated using Electronic or Manual Palpation are also detected through Elastography [5].

Thermorhythmometry: 

  • Thermorhythmometry is a form of detection technology that places probes on the breast for 24 hours to measure skin-temperature. This is a great alternative to identify tumors that may be missed due to screening tests that examine the breast for a short period of time [5].

Electrical Impedance Scanning: 

  • EIS is a form of screening technology used alongside Mammograms. It detects the electrical impedance that is often lower in cancerous cells through a probe that sends a small amount of electrical current to the breast. This technology is best used to lower the number of Biopsies by determining if the mass is cancerous. However, this device is not used as a screening technology and instead as an adjunct to other screenings and as an alternative to biopsies [5].

Sensitivity and Specificity:

Sensitivity measures how often a test correctly gives a true positive. If a test is highly sensitive, it will be able to correctly identify who all are positive, and it will not give a lot of false negatives. To calculate sensitivity, the formula is (true positive)/(true positive + false negative). 

Specificity is the measure of how often a test is able to correctly identify how many individuals are true negatives, and has less false positives. The formula to calculate specificity is (true negative)/(true negative + false positive) [6]. One thing to note is that in terms of screening, it is important to have a very high percentage for specificity. Having even a specificity of 95% is low, because in terms of the number of people who take a test, 5% of false positives or false negatives is quite large [7]. 

There are other values that are used to measure the accuracy of a test, including positive predictive value (PPV) and negative predictive value (NPV). PPV is the patients with a positive test who actually have the disease, which is calculated by (true positive)/ (true positive + false positive). Similarly, is the percentage of patients with a negative test that are actually negative for the disease [8].

Mammograms: 

The most well known screening test for breast cancer is a mammogram, which is an x-ray done for breasts. Many studies show that sensitivity for mammograms is around 70% to 90%. However, studies showed that as density increased, the sensitivity would decrease, which shows that screening mammograms are better for women who do not have dense breasts.7 Another problem with 2D mammograms is that the percentage of false positives is quite high, due to misleading results from calcifications and other such things, which indicate that 2D mammograms have a relatively low specificity rate. In developed countries like the US, another type of screeching test, known as 3D mammograms, or breast tomosynthesis, are available. Studies show that 3D mammograms are able to improve breast cancer detection rates by about 40%, and are better able to find smaller cancers, giving the patients better prognosis [9]. This improved accuracy is why some hospitals, such as Novant Health, have started using 3D mammograms as the standard test, rather than 2D mammograms [10].

Ultrasounds: 

For individuals who have dense breast tissue, the standard practice of screening is often an ultrasound. While different studies all slightly differ in ultrasound specificity and sensitivity scores, many give similar results, which is that for the most part, ultrasounds have higher sensitivity than mammograms.11 In fact, many studies show that ultrasounds and 3D mammograms have much better accuracy, sensitivity, and specificity compared to 2D mammograms.12 However, explicitly for older patients, mammograms have higher specificity, which means they detect less false positives. Ultrasounds are a great alternative for mammograms, especially for patients who have dense breasts [11].

PET/CT/MRI: 

Some other screening devices include PET scans, CT scans, and MRI scans. PET scans, which decently predict the risk of recurrence in breast cancer patients [13], are often not used for breast cancer because of their restricted ability to detect small tumors. CT scans, on the other hand, are not commonly used to evaluate the breasts, but they are used to check the spread of cancer [14]. However, the PET/CT together have very high sensitivity and specificity [15], much higher than that of 2D mammograms [16]. Studies also specify that PET scans that are breast-specific are much more accurate as compared to full body PET scans, because PET scans often have less resolution and supine positioning [17]. MRI scans are another type of screening test used for breast cancer. MRI has sensitivity ranges for breast cancer between 81% and 100%, and they have high specificity. MRI is better for screening more aggressive types of breast cancer, and also has higher sensitivity than mammogram for any type of cancer [18].   However, MRIs have a lot of things that interfere with imaging such as pacemakers and obesity. For these issues, PET scan is a good alternative [17]. 

Limitations of Mammograms:

   Although mammograms are one of the best breast cancer screening tests available right now, they have their limits. Oftentimes, they aren’t 100% accurate in showing if a person has breast cancer. 

A false negative result occurs when a mammogram looks normal even though there is cancer present. Overall, screening mammograms do not find about 1 in 5 breast cancers [19]. Possible causes for false negative results include poor positioning/technique, perception error, incorrect interpretation of a suspect finding, subtle features of malignancy, and slow growth of a lesion [20]. Additionally, mammograms can miss approximately half of cancers in women with dense breasts [21].

A false positive result occurs when a mammogram looks abnormal and detects cancer, even though there is no cancer present. False positive mammograms often require additional testing such as diagnostic mammograms, ultrasound, and breast biopsy to make sure the cancer is really there. False positive results occur most often in women who are younger, have dense breasts, have had breast biopsies, have family with breast cancer, or are taking estrogen. About half of the women who get annual mammograms over a 10 year period will have a false-positive finding at some point. The odds of false-positive findings are highest for the first mammogram. Women who have past mammograms available for comparison reduce their odds of a false-positive finding by about 50% [19].

Oftentimes, false-positive findings can cause anxiety. This can lead to additional testing to ensure the cancer isn’t there. This can cause stress and depression for the person and their loved ones. False positive and False negative findings can cost a lot of money and even physical discomfort. Additionally, because mammograms are x-ray tests, they expose the breasts to radiation. Although the amount of radiation from each mammogram is low, it can still add up over time [19].

References:

  1. Gaither, K. (2019, December 4). Breast exam at physician's office. WebMD. https://www.webmd.com/breast-cancer/doctors-breast-exam#:~:text=You%20should%20have%20a%20clinical,family%20history%20of%20breast%20cancer.

  2. Won, B. (2018, December 21). Some women should BEGIN mammograms in their 30s, study says - cancer care, health Topics, women's health. Hackensack Meridian Health. https://www.hackensackmeridianhealth.org/HealthU/2018/12/21/some-women-should-begin-mammograms-in-30s/#:~:text=A%20mammogram%20is%20the%20go,annually%20beginning%20at%20age%2045.

  3. da Costa Vieira, R. A., Biller, G., Uemura, G., Ruiz, C. A., & Curado, M. P. (2017). Breast cancer screening in developing countries. Clinics (Sao Paulo, Brazil), 72(4), 244–253. https://doi.org/10.6061/clinics/2017(04)09.

  4. Das, L. (n.d.). Breast cancer hub. Breast Cancer Hub. https://www.breastcancerhub.org/.

  5. Joy, Janet E. “Breast Cancer Technology Overview.” Saving Women's Lives: Strategies for Improving Breast Cancer Detection and Diagnosis., U.S. National Library of Medicine, 1 Jan. 1970, www.ncbi.nlm.nih.gov/books/NBK22310/. 

  6. Parikh, R., Mathai, A., Parikh, S., Chandra Sekhar, G., & Thomas, R. (2008). Understanding and using sensitivity, specificity and predictive values. Indian journal of ophthalmology, 56(1), 45–50. https://doi.org/10.4103/0301-4738.37595

  7. Breast Cancer Screening (PDQ®)–Health Professional Version. (2021a, June 17). National Cancer Institute. https://www.cancer.gov/types/breast/hp/breast-screening-pdq#_83_toc

  8. von Euler-Chelpin, M., Lillholm, M., Vejborg, I., Nielsen, M., & Lynge, E. (2019, October 17). Sensitivity of screening mammography by density And TEXTURE: A cohort study from a Population-based screening program in Denmark. Breast Cancer Research. https://breast-cancer-research.biomedcentral.com/articles/10.1186/s13058-019-1203-3#citeas.

  9. DePolo, J. (2019, June 26). 3D mammography more likely to find small invasive breast cancers, especially in women younger than 50. Breastcancer.org. https://www.breastcancer.org/research-news/3d-mammos-more-likely-to-find-small-invasive-bc.

  10. UVA Health System. (2021). 3D Mammograms. Novant Health UVA. https://www.novanthealthuva.org/services/womens-services/breast-care/3d-mammography.aspx.

  11. Tan, K. P., Mohamad Azlan, Z., Rumaisa, M. P., Siti Aisyah Murni, M. R., Radhika, S., Nurismah, M. I., Norlia, A., & Zulfiqar, M. A. (2014). The comparative accuracy of ultrasound and mammography in the detection of breast cancer. The Medical journal of Malaysia, 69(2), 79–85.

  12. Azzam, H., Kamal, R. M., Hanafy, M. M., Youssef, A., & Hashem, L. M. B. (2020, August 5). Comparative study between contrast-enhanced mammography, tomosynthesis, and breast ultrasound as complementary techniques to mammography in dense breast parenchyma. Egyptian Journal of Radiology and Nuclear Medicine. https://ejrnm.springeropen.com/articles/10.1186/s43055-020-00268-1#citeas.

  13. Weaver, C. H. (2021, June). The role of pet scans in the diagnosis and treatment of cancer. CancerConnect. https://news.cancerconnect.com/treatment-care/the-role-of-pet-scans-in-the-diagnosis-and-treatment-of-cancer.

  14. Providence. (2021, March 8). PET, CT scans, and thermagraphy for breast Cancer imaging: Saint john's Cancer Institute. Saint John's Cancer Institute. https://www.saintjohnscancer.org/breast/breast-health/breast-evaluation/other-tests/#:~:text=PET%20scans%20are%20not%20used,ability%20to%20detect%20small%20tumors.

  15. Shawky, M., Ali, Z. A. E., Hashem, D. H., & Houseni, M. (2020, July 9). Role of POSITRON-EMISSION Tomography/computed Tomography (PET/CT) in breast cancer. Egyptian Journal of Radiology and Nuclear Medicine. https://ejrnm.springeropen.com/articles/10.1186/s43055-020-00244-9.  

  16. Piva, R., Ticconi, F., Ceriani, V., Scalorbi, F., Fiz, F., Capitanio, S., Bauckneht, M., Cittadini, G., Sambuceti, G., & Morbelli, S. (2017). Comparative diagnostic accuracy of 18F-FDG PET/CT for breast cancer recurrence. Breast cancer (Dove Medical Press), 9, 461–471. https://doi.org/10.2147/BCTT.S111098

  17. Narayanan, D., & Berg, W. A. (2018). Use of Breast-Specific PET Scanners and Comparison with MR Imaging. Magnetic resonance imaging clinics of North America, 26(2), 265–272. https://doi.org/10.1016/j.mric.2017.12.006

  18. Mann, R. M., Kuhl, C. K., & Moy, L. (2019, January 18). Contrast‐enhanced mri for breast cancer screening. Wiley Online Library. https://onlinelibrary.wiley.com/doi/10.1002/jmri.26654.

  19. Limitations of mammograms: How often are mammograms wrong? American Cancer Society. (n.d.). https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/mammograms/limitations-of-mammograms.html.

  20. Newton, E. V. (2019, November 10). What is the prevalence of false-positive and false-negative mammography results in breast cancer screening? Latest Medical News, Clinical Trials, Guidelines - Today on Medscape. https://www.medscape.com/answers/1945498-167946/what-is-the-prevalence-of-false-positive-and-false-negative-mammography-results-in-breast-cancer-screening.

  21. Roy, L. D. (2021, July 1). Breast cancer - screening. Breast Cancer Hub. https://www.breastcancerhub.org/educational-cards/breastcancer-screening.



 
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