Breast Imaging for Breast Disease Diagnosis

Kerala Cancer Crusade, Cancer Literacy Mission and IRIA Preventive Radiology National Program conducted a Webinar Series on “Cancer Crusade and Cancer Literacy Mission” in association with IRIA Kerala, Swasthi Foundation and Community Oncology, Regional Cancer Centre, Journo Med. The fifth-day webinar discussed “Breast Imaging for Breast Disease Diagnosis”. The event was held on 18th October 2022.

National Breast Cancer Awareness Month was celebrated in October month. It was initiated in the year 1985 as a campaign by the American Academy of Family Physicians, AstraZeneca Healthcare Foundation, Cancer care and other organizations. Also, “Male Breast Cancer Awareness Week” was celebrated in the third week of October. An annual campaign was conducted globally to educate people regarding Breast Cancer. Cancer is the most prevalent disease and October month being a month to raise awareness, promote education, screen and to early detect the risk of cancer among cancer patients. Positive promotions were boosted to educate and support the campaign. Conversations regarding cancer help in spreading the word and explain the importance of Breast Imaging during Breast Disease Diagnosis. 

 Dr Umesh Krishnamurthy, a President-Elect of the Indian Radiological and Imaging Association (IRIA), and Radiology Professor at Ramaiah Medical College, Bengaluru conveyed the message given by Dr Pushparaj Patel that “IRIA is always for an Academic Association, involved in various academic activities.” The radiology colleges deliver lectures or webinars throughout the year which bring out the recent advancements in the field of Radiology and radiological information has been spread among the members. Dr Umesh participated in various webinars on Elastography, Oncology and the current topic is ” Breast Imaging Updates for Breast Disease Diagnosis”. It is very crucial because the Indian population are very hesitant at the initial stages and now people turn cautious, and they approach checkups related to Breast Imaging and other Breast related issues. Dr Rijo Mathew, President of IRIA, Kerala also revealed his point that Radiologists play a crucial role in guiding them regarding the diagnosis of Breast Cancer and other types of prevalent Cancers. There is much demand for Radiologists shortly. 

Professor Kwan Hoong NG, an Emeritus Professor in Medical Physics from the Department of Biomedical Imaging, University of Malaysia, Chair – ASIASAFE, AOSR, provided an update on Breast Imaging for the Diagnosis of Breast Disorders. He revealed the Globoscan cancer incidence which occurred in 2020. In the pink sector,  breast cancer, in particular, is about 11.7% related to other forms of cancer and in terms of mortality rate again the pink sector indicates about 7% of the overall mortality rate, almost 10 billion deaths from cancer were recorded in 2020. The global picture revealed the age-standardized per 100,000 people. The highest mortality rate was those in Western European Countries such as Belgium, Netherlands, France, Italy, Australia and New Zealand compared to the Asian countries. For example: In Malaysia, the mortality rate is 34.1 and in India, it is 25.8 to Globoscan 2020.

Early Detection of Breast Cancer and its Importance

Early detection of Breast Cancers and other cancers remains crucial and has significance in healthcare. In the beginning, cancer remains non-palpable and is even invisible for any form of imaging. There is a very high probability of a cure as it becomes denser. There is a large number of cells which are visible for Imaging, and it begins to spread from non-invasive localized to invasive, spread to other parts of the body. There lies the importance of early detection, and a better cure can be provided if detected at a very early stage. 

Breast Composition

The breast comprises fibro glandular tissues, duct lobules and connective tissues. The fibrous and the glandular tissues are together with the adipose tissue, the defective part of it.

A dense breast has a higher proportion of fibro glandular tissue. It has a higher risk of developing breast cancer.

Ideal Breast Imaging Modalities for the Detection and Diagnosis of Breast Cancer

•         Non-invasive Technique Recommended
•         Close to 100% Accurate Diagnosis
•         Predict the outcome of therapy
•         No or Minimum Radiation
•         Minimum Discomfort

Breast Imaging Modalities

•         Mammography
•         Ultrasound
•         Magnetic Resonance Imaging (MRI)
•          Single Photon Emitted Computed Tomography (SPECT)/ Positron Emitted Tomography (PET) Scan
•         Breast Computerized Tomography (CT) Scan
  
  Mammography

Most women above aged 50 years and even younger would have experienced the mammography examination. In this technique, the x-ray passes through the breast and forms the image based on its attenuation to the various components of the breast. Mammography has been proven in many randomized trials to reduce the mortality rate by 30% in women aged 50-60 years and up to 18% in women aged 40-50 years.

The method of choice in the current practice of diagnosing breast cancer in symptomatic women is considered the ” Standard in Imaging.”

However, mammography is imperfect as the sensitivity in mammography is pretty low i.e., 48% in dense breasts (compared to 98% in the fatty breasts) because in dense breasts the cancer lesions tend to be hidden among the fibro granular parts of the breast and this is called the “Masking Risk.” So, for women with dense breasts, mammography is not very easy and is recommended. That’s the reason, one needs to approach other modalities such as Ultrasound or MRI scans.

It is interesting to know about “Precision Compression”, which was followed in the early era of Mammography. There is no availability of a dedicated Mammographic Machine at that time. 

Evolution of Compression

Compression is important to form a high-quality image contrast. However, it discomforts women. There is a requirement for skilful radiologists, technologies and better machinery designed which is much more tolerable. A mammogram of fatty, scattered, heterogeneously dense and extremely dense breasts can be showcased as an example and as already discussed it is very difficult to locate the breast lesions hidden in the denser part.

Innovations in Digital Mammography

•         Digital Breast Tomosynthesis
•         Contrast-Enhanced Digital Mammography
•         Dual-energy contrast-enhanced Digital Subtraction Mammography

Digital Breast Tomosynthesis

In Digital Breast Tomosynthesis, the breast can be observed in three-dimensional form, but one can observe an image of two-dimensional tissues being superimposed over one another and then the lesion could be hidden. To overcome this disadvantage of mammography, tomosynthesis has been introduced to minimize the effects of structure overlap within the breast, and breast visualization can be done much better. 

 Digital Breast Tomosynthesis, an advanced form of mammography, aka 3D mammography. It uses a low-dose x-ray system and computer reconstructions to create 3D images of the breast. It helps in the early detection and diagnosis of breast disease.

 Breast Tomosynthesis System

 In the Breast Tomosynthesis System, the tube moves in a 15-degree arc.

• 15 low-dose images are acquired, 1 image per degree of motion
• Four-second sweep per view

Images are reconstructed into 1 mm slices through the breast

Imaging modes available:

• 2D Imaging only
• 3D Tomosynthesis Imaging (diagnostic only)
• Combined Exam Imaging: 2D+3D Tomosynthesis Imaging under the same compression, where 2D can be full-field digital mammography (combo mode) or C-view 2D generated from 3D (tomo HD mode).

Contrast-enhanced Digital Mammography

 It is a quick breast imaging technique which combines 3D tomosynthesis digital mammography with an intravenous contrast agent (iodine-based). It shows new or unusual blood flow patterns that develop when cancers grow.

Through this technique, a subtraction image derived from 130-sec contrast-enhanced digital image shows the homogeneous enhancement of the lesion.

Dual-energy contrast-enhanced Digital Subtraction Mammography

It consists of high-energy or low-energy Digital Mammography after the administration of the iodinated contrast agent technique.

In this technique, a dual-energy DSM image shows cancer as an enhancing mass with defined speculations.

Radiation Dose and Risk

The risk of carcinogenesis from the radiation dose to the breast is of major concern thus monitoring of the dose is crucial and is required annually by the MQSA (Mammography Quality Standard Act of 1992).

The MQSA limits the average glandular dose (AGD) or means glandular dose (quantity used to describe the absorbed dose of radiation to the breast in mammography) to 3mGy per view for a compressed breast thickness of 4.2 cm and a breast composition of 50% glandular and 50% adipose tissue (using the MQSA accredited mammography phantom).

If the mean glandular dose for this phantom exceeds 3mGy, mammo cannot be performed.

The average glandular dose for this phantom is typically 1.5 to 2.2 mGy per view if the equipment is properly calibrated.

Benefits and Risks

• If the Average Glandular Dose (AGD) is equal to 3mGy, the increased breast cancer risk is 6 per million when examined in women.
• Screening in 1 million women is expected to identify 3000 cases of breast cancer.
• The breast cancer mortality rate is about 50%.
• Screening would reduce the mortality rate by about 40% which means 600 lives being saved due to screening.
  
  Ultrasound Scan 

This breast imaging modality is based on the principle of sound waves speed and their echoes from various tissues i.e., either normal or abnormal to make computerized pictures inside the breast. 

 Benefits of Ultrasound

• For women with dense breast tissue, which is often problematic with conventional x-ray mammography usage.  So, in such cases, es Ultrasound scans are much preferred. 
• Adjunct to diagnostic mammography for biopsy guidance, palpable mass evaluation, benign and malignant nodules, and serial evaluation of benign masses.

Ultrasound is widely available, portable and relatively inexpensive but entirely depends upon the operator’s skills. 

Ultrasound Elastography

• Pathological changes occur to affect the stiffness of the tissue.
• Ultrasound Elastography measures the mechanical properties of tissue by observing the response of tissue to acoustic energy or external force.
• Tissue stiffness is estimated by young’s modulus.
• Ultrasound Elastography is broadly divided into Shear Wave Imaging and Strain Imaging.
  Strain Imaging includes the Quasi-static method which includes tissue displacement in the same direction of stress applied, there is no absolute value, and this technique is not very popular.
  Shear Wave Imaging is divided into three types-

-Mechanical impulse by external vibrator

1.       Transient Elastography (Fibro scan)
   -Acoustic Radiation Force Impulse (ARFI)

2.       Point Shear Wave Elastography
3.       Shear Wave Speed Imaging

Acoustic Radiation Force Impulse Imaging (ARFI)

Acoustic Radiation Force Impulse Imaging (ARFI) uses ultrasound to create a qualitative 2D map of tissue stiffness. A ‘push’ inside the tissue is created by using the acoustic radiation force from a focused ultrasound beam.

The amount the tissue along the axis of the beam is pushed down is reflective of tissue stiffness; softer tissue is more easily pushed than stiffer tissue.

Stiffer the tissue = Hard tissue= Sign of Malignancy

1.     Magnetic Resonance Imaging (MRI)

• This technique is quite complex and time-consuming, and it doesn’t use ionizing radiation. Breast MRI uses radio waves and magnetic fields to make detailed pictures of f breast (inner view).
• MRI is useful in assessing the extent of disease within the breast, particularly in women with dense breasts. MRI may be a more sensitive screening tool in women with an elevated breast cancer risk.
• Intravenous Gadolinium (contrast media) is administrated to assess the permeability of blood vessels supplying the tumour.
• Neo angiogenesis in breast cancer causes leaky vessels, hence rapid tumour enhancement.
• Nowadays, MRI breast protocol is multiparametric.
• Many imaging sequences such as T1, T2, dynamic contrast-enhanced (DCE), diffusion-weight imaging (DWI) and apparent diffusion coefficient (ADC)
• The breast lesion detected will be analyzed for their morphology, T1 and T2 characteristics and kinetics analysis derived from diffusion weight imaging (DCE).
• Standard MRI breast protocol.

2.     SPECT/PET Radionuclicide Scintigraphy

Radionuclide imaging or Scintigraphy uses radiolabeled tracers to detect the metabolic activity of breast tumours and this is a functional imaging part of it. A Single-Photon Emission Computerized Tomography (SPECT) Scan is a type of nuclear imaging test, which means it uses radioactive substances and a special camera to capture the 3D images.

• It detects single photons emitted by radionuclide tracers (Tc-99m).
• SPECT Scan determines the origin and direction of emitted gamma rays.

A Positron Emission Tomography (PET) Scan uses an injection of short-lived radioactive sugar (18FDG- fluorodeoxyglucose) into the body to detect metabolically active lesions.

Breast CT Scan

Breast CT Scans can detect unsuspected very small breast cancers that were unable to be identified by conventional mammography techniques.

• No compression
• Fast (currently 7 sec)
• 3D information
• Comparable dose with mammography

Breast Cancer Risk Factors

• Personal and Family History
• Genetic Predisposition
• Family history
• Breast density
• Reproductive factors
• Lifestyle changes
• Environmental changes 

Women with dense breasts have a 4-to-6-fold increased risk of developing breast cancer. Only age, BRCA1 and BRCA2 mutation increase the risk. It has been a problem to extract this information from a 2D mammogram. It doesn’t represent the dense volume of the fibro glandular component of the breast. The volumetric breast includes the whole-body volume over the breast. There is various software available that measure breast volume accurately and even the volumetric breast density can be measured by using a digital mammogram which enables the comparison of the data obtained from various studies. 

The search for various ideal breast imaging modalities from extreme mammograms to ultrasound elastography, SPET/PET scans, MRI scans, and Breast CT scans is available to provide a better view of breast imaging. Well, the researchers are still in search of ideal modalities with low radiation which provide accurate results and offer a correct diagnosis. 

Conclusion

With the advancement in the oncology field, the cure for breast cancer became very easy. However, there is still ongoing research on the various breast imaging modalities that offer a clear picture of the breast and the densely spread cancerous lesions over the breast. Compared to earlier times, preventive radiology and imaging techniques have raised their boom in the field of Modern Medicine. Even the early detection and screening of breast cancer issues can eradicate cancer to a major extent. However, the aim of the Kerala Cancer Crusade and the Literacy Mission is also the same i.e., to reduce the risk of cancer to a major extent.