•The aim of mammography is to obtain an optimum image along with maximum breast tissue visualization.
• There should be minimum discomfort to the patient
• There are a number of factors that affect the clinical image quality of a mammogram.
• These are positioning of the breast, compression, optimum exposure, sharpness, noise, and contrast.
• The quality of mammograms has improved remarkably after the introduction of digital mammography system. Also, strict quality assurance monitoring is being followed at present.
•With advancements in hardware and software, factors affecting image quality such as exposure, sharpness, noise, and contrast are being taken care of. The two factors that still affect the image quality are positioning and compression, both still being monitored by the operator.
•Compression are operator dependent. They can be avoided. Image quality can be improved by training and knowledge
•Breast positioning is a key factor affecting a mammogram.
•Careful attention during patient positioning can eliminate most mammographic artifacts and increase the performance of mammography. Optimal positioning maximizes the amount of breast tissue seen on image.
•It has to be kept in mind that while positioning the patient, one has to position the whole of the body and not just the breast of the patient. Body habitus of each patient is different. It has to be assessed and adjustments made for maximum tissue visualization.
•Proper and adequate turning of the head of the patient for Craniocaudal (CC) view and raising the arm for Mediolateral oblique (MLO) view is very important. Care also has to be taken to prevent injury to the shoulder and the arm.
•Another important factor that affects image quality of mammogram is compression. Adequate compression separates overlapping structures. It improves the quality and details of a questionable pathology.
•Failures in optimal positioning and appropriate compression are operator dependent. They can be avoided. Image quality can be improved by training and knowledge.
Optimal mammographic image quality can be achieved by:
1.Correct positioning technique.
3.Correct processing technique.
•Correct positioning technique is mandatory for an appropriate mammographic image.
•This includes appropriate compression to properly spread the breast tissue to avoid any fallacies because of skin fold and movement of breast tissue during exposure.
•Overlying tissues and structures such as shoulder should not come in the x-ray beam.
•There should be symmetrical images of both breasts.
•Pre and post processing artifacts should be avoided and it is also important to accurately mark each and every film with proper patient information.
•The standard film screen mammographic examinations consist basically of two views.
- Craniocaudal Projection (CCView)
- Mediolateral Oblique Projection (MLO View)
1. CRANIOCAUDAL VIEW (CC)
•The cassette is placed under the breast at the level of inframammary fold, and the breast is pulled until the inframammary fold is taut.
•Compression is then applied and x-ray beam is directed vertically from above.
•The posterior medial aspect of breast should be included in craniocaudal view as this area is most likely to be excluded in mediolateral projection.
•This view must show the medial part of the breast and should include lateral part of the breast as much as possible.
(a) nipple should be in profile
An ideal CC view with retromammary space and pectoralis muscle (arrows). Visualization of pectoralis muscle on CC view implies that no breast tissue along the chest wall has been excluded
(b) nipple should point straight and should not be pointing lateral or medial
Position of the nipple
(A) in profile,
(B) pointing medially, and
(C) pointing laterally.
(c) PNL must be within 1 cm of the same measurement of the MLO view. If it is not within 1 cm, some tissue has been excluded in the CC view.
The nipple should be seen in profile including the central part of the retroglandular fat tissue.
Mediolateral oblique Projection (MLO View)
•The MLO view is the best view to image all of the breast tissue and the pectoral muscle.
•The lateral view of the breast has been modified to take advantage of the orientation of the breast tissue in relation to the underlying chest wall and muscle structure.
•The C-arm of the mammographic unit is rotated to 45 degree angle for most women, so that the cassette is parallel to the pectoral muscle.
•The film holder is kept high in the axillary fossa and the patients arm is abducted at elbow by 80 degree.
•The x-ray beam enters the breast from medial side, i.e. from superomedial to inferolateral quadrant, at an angle of 45 degrees, so that compression is applied to the pectoralis major muscle perpendicular to its long axis.
•An MLO view should demonstrate axilla, axillary tail, and inframammary fold with all the breast tissue . •On an ideal MLO view
- breast should be pulled out with nipple in profile
- the pectoralis muscle margin should be well visualized
- the lower edge of pectoralis muscle should be at the level of pectoralis–nipple line (PNL) or below
- PND must be within 1 cm of the same measurement of the MLO view. When MLO image of both breasts are viewed as mirror images, pectoralis muscle should meet in the midline and form a “V”.
An ideal MLO view
(i) nipple in profile,
(ii) pectoralis muscle margin well visualized,
(iii) edge of pectoralis muscle below the level of PNL, and
(iv) inframammary angle (arrow).
pectoralis muscle forming “V,” when viewed as mirror images.
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