X-rays were discovered by Sir W.C. Roentgen in 1895, but since that time imaging of breast did not get its due importance primarily due to the poor quality of the images, until 1930 when Dr Warren stressed the importance of imaging in picking up breast cancers. Earlier to imaging they were palpated and correlating it with pathology. He used the same fluoroscopic equipment which was used for other body parts to pick up tumors. The evolution of the breast imaging since that time to now has been quite interesting.
In mid-1930s, techniques like thrototrast injections and carbon dioxide insufflations were used which of course were discontinued due to inflammatory reactions. Direct exposures technique was the only technique of imaging breast and continued for approximately three decades when these gave way to Xeromammography in 1970, which is a sort of Xerox of the breast tissue on paper. The technique was accepted well, as it gave good edge enhancements but the radiation dose was very high. So in the early 1970s, the landmark technological advancement came in form of Screen film mammography which had screens to improve the resolution and collimators to focus the radiation, hence give better resolution with less radiation dose. Thereafter, with the advent of better breast compression techniques and the introduction of multiple views of the breast, Screen film mammography became an efficient screening method of the times which completely replaced direct exposure radiography and Xeromammography. Within a decade, with other advancements like spot compression and magnification views, characterization of masses and calcifications also became possible. Standardized reading and reporting formats were developed which gave uniformity in reporting across the globe by providing standardized lexicon and recommendations on management. Within no time, multiple randomized controlled trials proved a significant decrease in the mortality of the patient by the use of screening mammography and it became a global screening tool for early detection of breast cancers.
At the turn of the century, Mammography imaging experienced landmark advancement in the face of Digital Mammography. In this technique, the transmitted radiation is collected on an image detector instead of a film and is displayed on the monitor. These techniques reduced remarkably the film processing time and, in a way, total time for reporting. Other advantages in converting to digital mammography also included lower radiation dose, no film wastage and faster intervention procedures. Cross-correlation among different modalities could be facilitated on the same workstation. Integration with the electronic medical record, PACS and the radiology information system could be done which saved a lot of time as need of physical transfer of the film was obliviated. Large detector size led to imaging the bigger size of the breast in a single view and hence was termed Full field Digital Mammography.
Looking ahead now Digital Breast Tomosynthesis (DBT) is a new technology which has revolutionized the Breast imaging techniques. It acquires multiple low dose mammographic projections through the breast. It has been shown to reduce false-positive findings in masses, asymmetries, and architectural distortion as they were more readily characterized on the tomosynthesis images leading to the reduction in non-cancer recall rates and preventing unnecessary additional diagnostic testing in these women. Hence, DBT has been called “a better mammogram” and just may become the standard for mammographic screening in times to come.
With the above-said advances, the detection of the mass within the breast became better but the classification of the mass into benign or malignant with tissue diagnosis needed advances in intervention techniques as well. In the earlier times, free hand localization of the palpable mass used to be done and which was then confirmed on the mammography equipment and the patient was shifted to OR. But for smaller and non-palpable lesions compression plate is fitted with grid localizers which aid in localizing the non-palpable mass lesions with good accuracy. Hook wires are put through the mass and the patient is the shifted to OR for further management. For localization of very small lesions or just the areas of architectural distortions/ micro calcifications, stereotactic breast biopsy systems are available which by the principle of stereotactic are able to localize the lesion with a fairly good degree of accuracy.
As with the times, now we want to detect smaller and smaller lesions and be completely sure of the disease status of the patient before shifting the patient to the OR, so conventional intervention techniques which were Fine Needle Aspiration and Biopsy gave way to Core biopsies and Vacuum-assisted core biopsies. These new techniques remarkably reduce the chances of getting an insufficient sample for tissue diagnosis.
Besides X-ray mammography, there are remarkable advancements in other breast imaging modalities as well. Introduction of elastography in ultrasound and MR mammography can indicate the tissue characterization based on the tissue strain. MR spectroscopy is a means of noninvasively probing the chemistry of tissues. A promising application of MR spectroscopy is in the early assessment of treatment response by using single-voxel proton spectroscopy and knowing the chlorine levels in the tumor which are an indicator of response to chemotherapy. Diffusion-weighted imaging is a noninvasive means of knowing breast tissue microstructure on the basis of random motion (Brownian motion) of water molecules. Because tumors have increased cellularity, they will exhibit “restricted” or reduced diffusion of water molecules. So these new techniques remarkably aid in the lesion detection, characterization and assessment of treatment response.
So after going through this remarkable journey of breast imaging technological advances which happened within last four decades, it is imperative to say that breast imaging has come of way and that too in a much paced up manner, which makes both the radiologists and their patients very happy and satisfied.