Authors: Kinga Karlinger, Erika Márton
12. Diagnostic Breast Imaging Author: Zsuzsanna Dömötöri Author: Zsuzsanna Dömötöri
Semmelweis University Department of Radiology and Oncotherapy, Budapest The purpose of this chapter:
The goal of this chapter is to provide an introduction to the 4th year medical students at the University of General Medicine on up-to-date breast imaging methods and their basic principles. It is also important to mention the role of breast screening examinations and to outline what diagnostic gain are to be expected from the different examination methods and what sequence of protocols are to be used. A fundamental knowledge is necessary for future doctors to be able to understand mammography reports and to have a familiarity with the codes and abbreviations they would encounter during their practice.
12.1. Introduction
Today, mammography is one of the fastest evolving areas of diagnostic radiology. Many new technical applications have evolved in the recent decades that have improved image
production and processing, as well as diagnostic tissue sampling. These advancements have modified the diagnostic algorithms in breast imaging. The reasons for the recent advancement have been partially influenced by the technical developments of new methods, and also by the pressing need for better imaging. All of this is accordance with the fact that the number of breast cancer patients is on the rise worldwide, including Hungary.
The cause of breast cancer is still unknown; consequently its primary prevention has not yet been made possible. However, it is a proven fact that early detection and the start of adequate therapy can significantly decrease the rate of mortality due to breast cancer. Improved
imaging has helped the detection of small, neoplastic lesions at their early, clinically non-symptomatic phase.
Today, in breast imaging we differentiate screening mammography from clinical mammography.
1./Screening mammography: Regularly repeated examination of asymptomatic and complaint free women within the prevalent age-group within determined and controlled circumstances.
It does not provide a definitive diagnosis.
The purpose of screening is to significantly decrease the mortality of breast carcinoma related deaths with increasing the diagnosis of small (under 14 mm size), asymptomatic aggressive tumors. Since 2002 Hungary has established a nation-wide breast screening program. Women between the ages 40-65 are screened methodically, the service is free of charge and repeated biannually.
2./Clinical mammography: is the examination of women with complaints and clinical symptoms, independent from their age. The examination provides a definitive diagnosis.
143 12.2. Breast Imaging Modalities
12.2.1. The general role of diagnostic imaging
o screening
o identification of pathologic lesions
o determination of lesion dignity
o biopsy guidance
o staging
o preoperative localization of non-palpable lesions
o specimen mammography
o therapeutic planning
o remainder marking of a lesion
o breast implant examination
o control examination
12.2.2. Diagnostic Imaging Methods
• Mammography: traditional (analogue), digital technique, and tomosynthesis
• Breast Ultrasonography
• MRI examination (Breast MRI)
• CT examination: with the current technical circumstances its role in breast imaging is very limited.
• Nuclear medicine examinations: breast scintigraphy, sentinel lymph node tagging, SPECT, PET/CT examinations
• Interventions:
o Diagnostic: pneumocystography, ductography, biopsy, localizing methods
o Therapeutic: percutaneous tumor ablation, radiofrequency ablation (RFA)
12.2.2.1. Mammography
It is a fundamental diagnostic method in both diagnostic and clinical mammography, during which plain pictures are taken.
Advantages:
Disadvantages:
12.2.2.1.1. Types of Mammography:
1. Traditional (Analogue) mammography: image production, appearance and storage all occur at the same place, the X-ray film. Technical requirements are low voltage (25-32Kv, = soft beam technique, high beam intensity, mAsec), special anode, double focus X-ray tube.
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2. Digital mammography: (pictures 1,2,3) phosphorous plate or direct digital methods. For breast imaging the latter is the method of choice. Phases of image production separate. The image is produced on the detectors, but appears on the high resolution monitor and can be stored as a digital data set at various storage mediums (e.g.: CD, hard disk drives).
Picture 1. Picture 2. Picture 3.
Advantages:
o significantly decreases radiation
o higher contrast and sharpness
o stable image quality
o depicts microcalcifications better than the analogue techniques
o no need for picture development, dark room
o eco friendly
o larger capacity
o image postprocessing possibilities (magnification, image inversion, contrast effects)
o teleradiology, telereporting
o supervisory function
o easier patient follow up, unnecessary exam or biopsy repetitions can be avoided
o simplified archiving
o CAD computer aided diagnostics
The spatial resolution of the digital technique is not higher than that of the analogue one!
3. Tomosynthesis: is a supplementary examination method. It is still not a part of the daily routine, but this technique is becoming more popular and widely available. With this method lesions can be highlighted from their surrounding environment.
Mammography exposition: all breast images have to be acquired at least in two directions!
Standard images: cranio-caudal (CC) and half-oblique medio-lateral (MLO) Additional images: lateral (medio-lateral, latero-medial) magnified images etc.
12.2.2.2. Breast Ultrasonography
The second most commonly used diagnostic method. For women above 35 years of age it is a complimentary examination, while for women under 35 years – except for cases of suspected
145 malignancy – it is a stand alone or first choice examination. In breasts of greater volume, mammography is necessary as well.
US is used as primary examination during pregnancy and lactation, as well as in patients with acute phase inflammatory processes.
Technical requirements: a high resolution linear head of 7.5 MHz, with a maximum length of 4-5 cm. A second supplementary head of 12-18 MHz is also recommended. The examination needs to be archived.
Diagnostic indications:
Therapeutic indications:
- cyst puncture
- abscess drainage
Doppler examinations: can only be used as auxiliary exams. It depicts higher vascularization in malignant tissues.
12.2.2.3. Magnetic Resonance Imaging of the Breast (Breast MRI)
Requirements: At least 1.5T MRI machine, breast coils, iv. contrast agent. (For interventional procedures MR compatible biopsy equipment, marking wires are required). Background:
malignant neoplasms show increased blood supply due to neo-angiogenesis.
The most important indications of MRM:
Dynamic Breast MRI:
Benign and malignant lesions in most cases show different contrast enhancement dynamics and morphology. However, its differentiation ability of benign from malignant is limited.
Disadvantages of breast MRI:
12.2.2.4. Nuclear medicine examinations
1. Breast scintigraphy: has lost its significance in the recent years. Malignant tissues in the breast show enhanced Tc99 MIBI radiopharmacon uptake, due to increased cell activity, that can be registered by gamma cameras.