Recent Advances

in Mammography

DR.SUHAS B

RESIDENT (MD RADIO-DIAGNOSIS)

Brief History

Concept of using x-ray to visualize breast tissue was first putforth by Dr.Albert Salomon, a

German surgeon in 1913

In 1950’s Jacob Gershon began to advocate widespread use of x-rays for screening

purpose.

In December 2005 RSNA brings digital mammography to USA

Introduction

Mammography is the gold standard for detecting breast lesions.

However, modern mammography has only existed since about 1970, when the first

dedicated mammography imaging systems became widely available.

There has been tremendous advancement in the technology so that today’s examination

differs markedly even from those of the early 1980s.

Modern x-ray mammography uses dedicated systems (that is, a machine used only for breast x-rays) to produce x-rays that are high in quality but low in radiation dose.

Modern mammography systems are tightly monitored by the Mammography Quality

Standard Act (MQSA)

Equipment

Automatic Exposure Control

Magnification View

Magnifies the image by 1.5x to 2.0x

Increased effective resolution

Small focal spot size used (lower mA and

longer exposure times)

Dose increased

Reduction of scatter

Full Field Digital Mammography Although film screen mammography were effective, according to various studies up to

20-30% of malignancies were missed by the regular film screen mammography.

One of the drawbacks of SFM is its contrast resolution. The breast is a difficult organ to image as it consists of tissues of contrasting densities; glandular tissue interspersed with fat.

It has been found that women with dense breasts have a four to six times higher risk of breast cancer compared to women with little or no glandular tissue. This is postulated to be due to the masking of existing lesions by the overlying breast tissue.

Therefore the sensitivity of mammography in detecting carcinoma in dense breasts is limited; a 62.9% reduction in sensitivity in dense breasts as compared to 87.0% in breasts with fatty involution

Hence digital mammography was introduced to achieve better imaging of breasts.

Full Field Digital Mammography

Types of Digitalization

Full Field Digital Mammography (contd.)

It works like a DR system wherein the x-rays are directly converted into photons directly or through a scintillator (indirectly) and an electronic signal detector converts this light/photons into digitized form (binary system) to be read through an external device (CCD or Flat-panel)

When comparing DM to SFM, it was found that the overall diagnostic accuracy of both technologies in detecting breast cancer detection was similar

FFDM has a better signal to noise ratio than FSM.

Preferably uses W/Rh combination.

Near instantaneous image acquisition helps in cost cutting and time management.

Above – Infiltrating ductal cell carcinoma well appreciated in MLO with thickening of superficial skin

Left – A rounded well defined calcified nodule in subcutaneous fat (CC view)

Left - Nodule at right outer quadrant on right CC view (black arrow). (b) Magnification of the nodule shows a rim of lucent halo suggestive of a benign nodule

Full Field Digital Mammography (contd.) DM is able to capture areas of contrasting densities and display these regions without

compromising the contrast resolution very much.

SFM boasts a high spatial resolution of approximately 16 linepairs per mm which enables detection of fine structures such as microcalcification.

The spatial resolution of DM, however, is limited by pixel size. Despite this limitation, it has been found that the detection of microcalcifications on DM is equal to, if not better than, that of SFM.

This is due to the increased contrast resolution of DM which enhances its ability to visualisesmall high-contrast structures such as microcalcification

There is a 45% reduction in the time taken to perform examinations and process images using DM when compared to SFM.

Above image shows very minute calcifications in an inverted digital

image which are otherwise definitely missed and not even seen in SFM

Advantages

Higher contrast resolution

Ability to manipulate to improve image quality and visibility

Reduced false positives and increased PPV

Fewer repeat exams for poor exposure. Hence high repeatability index.

Faster patient throughput

Eliminates processing issues

Simplifies storage and retrieval of images

Avails possibilities for remote assessing of the images

Significantly better image acquisition than SFM in women under 50 years, in pre and peri-menopausal women and in denser breasts.

Able to do stereotactic biopsy

Availability of CAD

Disadvantages

Expensive (>300,000$ per QALY gained)

Less accurate in patients with fatty breasts

Stereotactic or Mammography guided

biopsy of suspicious mass

using an automated vacuum

powered device.

Contrast Enhanced Digital Mammography

CEDM is a recent development of digital mammography using the intra-venous injection of

an iodinated contrast agent in conjunction with a mammography examination.

Contrast-enhanced mammography is based on the principle that rapidly growing tumors

require increased blood supply to support growth.

The contrast agent preferentially accumulates in such areas, and contrast-enhanced mammography offers a method of imaging contrast distribution in breast tissue.

This technique can increase mammographic lesion conspicuity

Contrast Enhanced Digital MammographyTwo techniques have been developed to perform CEDM examinations –

1. Temporal Subtraction :

Technique with acquisition of high-energy images before and after contrast medium injection.

The temporal subtraction technique offers the possibility to analyze the kinetic curve of enhancement of breast lesions.

A finite number of sequential images are obtained at a high energy, above the K-edge of Iodine, and with an intravenous non-ionic Iodine contrast agent.

The main disadvantages of this technique are that only a single breast can be imaged, patients have to maintain a particular position (usually MLO) for a prolonged period

Motion artifacts are more as breast is under compression when contrast arrives in the blood stream

Contrast Enhanced Digital Mammography

2. Dual Energy CEDM

This is a technique based on dual-energy acquisitions, where two images are acquired using

distinct low-energy (standard mammography kV and filtration) and high-energy (higher kV with

strong filtration) X-ray spectra.

The differences between X-ray attenuation of iodine and breast tissues at these two energy levels

are exploited to suppress the background breast tissue.

Dual-energy CEDM depicts areas in the breast associated with increased vascularity

2 min after the start of contrast injection that images are acquired.

Absence of compression during contrast injection also ensures non-occlusion of small tumor

feeders and, hence, adequate uptake by even small lesions.

The procedure takes approximately 10 min and could be followed by either a stereotactic or an

USG-guided biopsy in the same sitting.

The dual energy technique do not provide information about the kinetic of tumor enhancement

but allows the acquisition of multiples views of the same breast or bilateral examination and is less

sensitive to patient motion than temporal CEDM

Post contrast images show an enhancing

lesion proved to be malignant on biopsyPost-contrast images show an enhancing lesion infero-medial quadrant - DCC

Breast Tomosynthesis

Also known as 3D mammography.

Its an extension of digital mammography

Breast tomosynthesis is a new tool that is based on the acquisition of three-dimensional

digital image data, could help solve the problem of interpreting mammographic

features produced by tissue overlap.

In breast tomosynthesis, a moving x-ray source and a digital detector are used.

Breast Tomosynthesis (contd.)

The x-ray tube in a breast tomosynthesis system moves along an arc during exposure.

An arc like linear motion is suitable for imaging of breast tissue because most normal

anatomic structures in the breast are oriented from the chest wall to the nipple.

A wider angular range allows a thinner reconstructed section thickness of the in-focus

plane because objects in the different planes are less blurred on images acquired at a

smaller angle.

Normal lactiferous ducts are more prominently depicted on

the breast tomosynthesis image (arrows in a) than on the

digital mammogram (b).

Normal glandular tissues are more clearly depicted on the

breast tomosynthesis image (arrows in a) than on the digital

mammogram (b).

Comparison of screening mammography with breast tomosynthesis in a 57-

year-old woman. (a) Digital mammogram shows a mass (arrows) in the lower

outer part of the left breast. The mass is not clearly visible because of

surrounding dense tissue. (b) Breast tomosynthesis image provides clearer

depiction of the mass (arrows), which is well circumscribed.

Micropapillarytype ductal carcinoma in situ in a 65-year-old woman. (a) Digital mammogram shows the primary mass (arrows). (b) Breast tomosynthesis image more clearly depicts the border of the mass (black arrows) and adjacent ductal extension (white arrow).

Advantages

Since it is an extension of digital tomography, it has the same advantages as that of

FFDM.

Better depiction of the smallest calcifications

The total radiation exposure to the patient from a two-view tomosynthesis acquisition is

similar to or less than that from conventional mammography.

Better delineation of the lesion border results in a more definitive interpretation.

Breast tomosynthesis requires less compression than does 2D mammography.

Disadvantages

Special training of technologists is needed for positioning

Motion artifacts are more likely to occur because of the slightly longer exposure time

Large calcifications cause significant artifacts.

Reconstructed images lengthens interpretation time for radiologists

Computerized Tomography Laser Mammography

Is an optical tomographic technique for breast imaging.

This medical imaging technique uses laser energy in the near infrared region of the spectrum, to detect angiogenesis in the breast tissue

It is optical molecular imaging for hemoglobin both oxygenated and deoxygenated.

The technology uses laser in the same way computed tomography uses X-Rays, these beams travel through tissue and suffer attenuation.

A laser detector measures the intensity drop and the data is collected as the laser detector moves across the breast creating a tomography image.

CTLM is able to recognize malignant tumour from benign lesion

CTLM images show hemoglobin distribution in a tissue and can detect areas of Angiogenesis surrounding malignant tumors, that stimulate this angiogenesis to obtain nutrients for growth.

Computerized Tomography Laser Mammography

Scintimammography Scintimammography, also known as nuclear medicine breast imaging, is an examination that may be

used to investigate a breast abnormality that has been discovered on mammography.

Scintimammography is also known as Breast Specific Gamma Imaging (BSGI) or Molecular Breast Imaging (MBI).

Done in those who had abnormal mammograms, or for those who have dense breast tissue, post-operative scar tissue or breast implants.

Patient receives an injection of a small amount of a radioactive substance called technetium 99 sestamibi, which is taken up by cancer cells, and a gamma camera is used to take pictures of the breasts.

Also called a Miraluma test (when with sestamibi)[3] and sestamibi breast imaging.

The procedure is less accurate in evaluating abnormalities smaller than one centimeter.

Patient is exposed to slightly more radiation than mammography but has higher sensitivity and PPV than conventional mammography.

Pre-therapy (early image A, delayed image B) and post-therapy (early image C, delayed image D) 99mTC-sestamibi studies of a patient who showed no response to chemotherapy at pathologic examination. Pretherapy studies show evidence of high 99mTC-sestamibi washout rate, predicting high MDR expression. Image C confirms negative response to chemotherapy; image D shows evident decrease in tracer uptake.

Scintimammgraphy. Breast carcinoma in right and left side (black arrows) and

lymphonodal metastase (red arrow).

Optical Mammography Diffuse optical imaging is a set of non-invasive imaging modalities that use near-infrared light, which can

be an alternative, if not replacement, to those existing modalities.

Such 3D maps of hemodynamic parameters serve as indicators of malignant tumors, as it is known that tumor position is strongly correlated with total hemoglobin concentration via angiogenesis.

Optical mammography uses near infrared light to scan breast tissue, then applies an algorithm to interpret the image and information. The technique can measure differences in water and fats.

The tool creates real-time images of metabolic changes, allowing the differentiation between oxygen-rich and oxygen-poor tissue and varying levels of hemoglobin through differences in light absorption.

Optical mammography is comparatively more comfortable with much less breast compression compared to conventional mammography.

There is a high acceptance of the technology from patients, mostly because of the lack of breast compression and the lack of ionizing radiation and it has very high repeatability index.

Optical Mammography

Computer Aided Detection

Introduction

Mammography has a low positive predictive value of 35% in detection of malignancies.

But, due to the high number of mammograms to be read, the accuracy rate tends to decrease

Double reading of mammograms has been proven to increase the accuracy, but at high cost

CAD can assist the medical staff to achieve high efficiency and effectiveness

Hence computer aided detection or CAD was developed to assist the radiologists, thereby reducing the false positive rate.

It is a two level reporting system.

Helps to reduce interpretative or subjective errors.

Computer Aided Detection (contd.)

Functions

CAD is designed to detect , classify the clustered micro calcification and nodules.

Image segmentation : detection , extraction of clustered micro calcified nodules

from back ground breast tissue.

Extracted micro calcification nodules are categorized as benign or malignant (image

classification)

Computer Aided Detection (contd.)

Basic Components of the System

Mammogram Normalization

Mammogram Registration

Mammogram Subtraction

Feature Extraction

- Morphological Closing

- Morphological Opening

- Size Test

- Border Test

ROC/FROC Analysis

Computer Aided Detection (contd.)

Proposed Method

The proposed method will assist the physician by providing a second opinion on

reading the mammogram, by pointing out area(s) that are different between the

right and left breasts

If the two readings are similar, no more work is to be done

If they are different, the radiologist will take a second look to make the final

diagnosis

Computer Aided Detection (contd.)

Data Used

The dataset used is the Mammographic Image Analysis Society (MIAS) MINIMIAS database

containing Medio-Lateral Oblique (MLO) views for each breast for 161 patients for a total of

322 images. Each image is 1024 pixels X 1024 pixels.

Normalization

The images were corrected/normalized to avoid differences in brightness between the

right and left mammograms.

Computer Aided Detection (contd.)

Retrospective studies have shown the ability of CAD to mark cancers with a high degree

of accuracy, especially when microcalcifications are present.

One study estimated that as many as 25% of cancers could have been detected an

average of 14 months sooner using CAD. In another retrospective review, the sensitivity of

CAD was 75% for masses and 99% for microcalcifications.

Positron Emission Mammography Positron emission mammography (PEM) has been approved by the US Food and Drug

Administration and introduced into clinical use as a diagnostic adjunct to mammography and breast ultrasonography.

PEM has higher resolution and a more localized field of view than positron emission tomography–computed tomography and can be performed on patients to stage a newly diagnosed malignancy.

PEM uses a pair of dedicated gamma radiation detectors placed above and below the breast and mild breast compression to detect coincident gamma rays after administration of fluorine-18 fluorodeoxyglucose (18F-FDG)

The principle behind this technology is that cancer cells demonstrate increased utilization of glucose. Through use of isotope fluorine-18 attached to the delivery compound deoxyglucose to produce the radiopharmaceutical 18F-FDG, this utilization of glucose can be visualized.

Positron Emission Mammography

When is PEM advised?

It is done after mammography or USG in following cases:

Presence of mass lesions which are conspicuous

Dense breasts where mammography and USG couldn’t delineate the lesion properly

In breasts with diffuse calcifications

In deformed breasts (post-op/post-RT)

In lesions which couldn’t be classified according to BIRADS

When MRI of breasts are contra-indicated

Positron Emission Mammography

Advantages

Better delineation of lesion

High positive predictive value for malignancies

Reduced workload

Helpful for pre-op assessment

Has good pathological correlation

Effective in follow up or in planning for RT

Disadvantages

Higher radiation exposure

Not recommended for screening purposes

Low repeatability index

Automated Breast Ultrasound Also known as Automated 3D US Breast Volume Scanning (ABVS)

Cross-correlation between multiplanar reconstructions

Optimizes assessment and correlation with mammography and MRI

Disconnection of image acquisition and assessment: suitable for double reading, screening and CAD

Facilitates preoperative surgical planning: Lesion distance to nipple and skin; Indication and lesion position.

Doubles cancer detection from 3.6 to 7.2 per 1,000 compared with mammography alone in dense breasts and triples detected invasive cancers < 10 mm

US detects early-stage cancers in women with mammography-negative dense breasts

Can be combined with MRI or mammography to reproduce fusion images.

Drawbacks and Limitations of ABUS

Depth & focus are fixed

Lymph node stations not reliably evaluable

Doppler and elastography not possible

Imaging artefacts

- Suboptimal contact (skin folds)

- Transducer movement (breathing)

- Skip artefact (superficially located tumors)

Breast MRI Also known as MR Mammography/MRM.

It is a valuable tool to diagnose additional cancer in the same breast in up to one third of patients and is recommended as a supplemental screening tool to mammography in women considered to be at high risk for developing breast cancer.

MRI is more sensitive an accurate than mammography and ultrasound in detection of invasive lobular cancer, which occurs at a higher rate in women with a history of hormone replacement therapy.

Dedicated bilateral breast surface coil (simultaneous examination of both breasts)

Preoperative MRI more accurate in assessing tumor extent and multi-focality (incl. DCIS)

MRI lowest FN rate in detecting ILC, highest accuracy in measuring the size

MRM could detect extensive intraductal component (EIC): sensitivity 71%, specificity 85%, accuracy 76%

Fischer Scoring

Indications

Malignancy (detection, prognosis, treatment monitoring)

Axillary lymphadenopathy

Screening of high-risk women

Distinguishing of scar and recurrence

Implant complications

Biopsy of the malignant/benign lesion can be done at the same sitting.

Further evaluating hard-to-assess abnormalities seen on mammography

Evaluating lumpectomy sites in the years following breast cancer treatment

Evaluating breast implants

Pitfalls

MRI typically costs more and takes more time to perform than other imaging modalities.

MRI persistently underestimate minimal residual disease

Electrical Impedance Scanning (EIS) T-scan (also called electrical impedance scanning or EIS) was approved by the U.S. Food and Drug

Administration (FDA) to be used as an adjunct tool to mammography in helping to detect breast cancer.

The T-scan measures low level bioelectric currents to produce real-time images of the electrical impedance properties of the breast. The resulting impedance images of the breast tissue can be used to help determine if the region of interest is normal tissue or a cancerous tumor.

The T-scan works by creating an image "map" of the breast using a small electrical current.

One-volt of continuous electricity (approximately the same as holding a flashlight battery by its ends) is transmitted into the body, either through an electrode patch attached to the arm or a hand-held cylinder.

The electric current travels through the breast where it is then measured at skin level by a probe placed on the breast.

T-scan impedance imaging of the breast does not use radiation such as x-rays or radionuclides, does not require compression of the breast, and does not require an injection or biopsy sampling of the breast tissue via needle or surgical incision.

Conclusion

Mammography still remains the basic breast imaging examination

Digital mammography provides better visualization in dense breast

DBT is an exciting prospect which will definitely improve the diagnosis

MR Mammography is recommended in women with Lifetime risk of higher than 20%

Tremendous advances are taking place in this field.

We are heading towards non-radiating mammography which supplements and

compliments to regular mammography

Technological advances in breast imaging, such as DBT, ultrasound and mri have

gained extensive acceptance, and have shown significant potential benefits in breast

cancer detection enhancing the diagnostic accuracy.

Various attempts will be made in future to have mammography completely free of radiation without compromising the information and image quality.

Refernces :

Diekmann F., Bick U: "Tomosynthesis and contrast-enhanced digital mammography:

recent advances in digital mammography"; European Radiology; v.17:3086-3092

Brem, R. et al : "Detection of Occult Foci of Breast Cancer Using Breast-Speci#c Gamma

Imaging in Women with One Mammographic or Clinically Suspicious Breast Lesion"; Acad Radiol; 17:735-743

Dean, J. : "Using Automated Breast Ultrasound to Reduce or Eliminate Interval Cancers" in

www.diagnosticimaging.com

Gennaro G. et al : "Digital breast tomosynthesis versus digital mammography: a clinical performance study"; European Radiology; v.20:1545-1553.

Weigert et al : "Results of a Multicenter Patient Registry to Determine the Clinical Impact

of Breast-Specific Gamma Imaging, a Molecular Breast Imaging Technique"; AJR:198.

Potente, G. et al : "Practical application of contrast-enhanced magnetic resonance

mammography [CE-MRM] by an algorithm combining morphological and

enhancement patterns"; Computerized Medical Imaging and Graphics 33; 83-90.