Quality Assurance Guidelines for Breast Imaging – Breast Imaging Society, India

1.1 Mammography equipment

Mammography units can be of three types - Digital radiography (DR), Computed radiography (CR), and Traditional film-based mammography. Quality assurance tests are mandatory for all types of mammography units, and mandatory test reports are to be submitted to the Radiological Safety Division of AERB, India, as per the regulations.

The acquisition technique of mammographic images must be monitored with specific attention to radiation dose and technical adequacy of films. The radiation dose must be minimized based on the As Low As Reasonably Achievable (ALARA) principle.^[1] Most mammography units have an automatic exposure control (AEC) system, which helps minimize radiation for the given breast thickness and composition. Exposure time must be as low as possible to reduce dose, avoid motion artifacts, and minimize discomfort to the lady being imaged. Optimal compression must be applied.^[2]

The regulatory inspection program of AERB includes three types of inspections. There are planned and announced inspections, special regulatory inspections, which are reactive and announced, and surprise regulatory inspections, which are reactive/proactive and unannounced.^[3]

At the time of installation, submission of a survey report detailing the radiation survey levels measured around the installation is mandatory.^[4] The radiation survey report contains details of the maximum radiation level at various locations, such as the lead glass wall, operator position, entrance door, patient waiting area, front and side walls, and the entrance corridor. The radiation survey report also contains details of the QA tools used, such as kVp and dose meter, survey meter, and imaging phantom.

Typical AERB tests and measurements include performance test verification of safety system/components, radiation protection survey, area monitoring, clinical/product dosimetry, and contamination checks.^[3] Personal dosimeters must be given to all radiation workers, including trainees. Any unusual occurrence/incident must be documented, and measures must be taken to avoid recurrence.^[3]

Periodic QA test reports must be submitted to AERB at least once every two years and after any repairs with radiation safety implications.^[5] Parameters tested for periodic radiation safety performance test reports include accuracy of operating potential, accuracy of timer, linearity of tube current, reproducibility of output, radiation leakage level at 5 cm from the external surface of X-ray tube housing, total filtration and performance of imaging phantom.^[5] Image quality is assessed by using a mammography phantom. The manufacturer provides the optimum value for the tests, and the measurements acquired are compared against the provided optimum value and AERB standards.

Digital detectors must be calibrated periodically as per the manufacturer’s recommendations for DR Mammography. The CR cassettes must be cleaned and evaluated for artifacts as per the manufacturer’s instructions for CR Mammography. In the presence of artifacts that compromise image quality (for example, artifacts that mimic microcalcifications), the CR cassettes must be discarded. Traditional film-based mammography cassettes must be similarly monitored, and darkroom techniques must follow the manufacturer’s instructions.

1.2 Mammography image acquisition

Technically adequate Mediolateral oblique (MLO) and Craniocaudal (CC) views are the two standard views of mammography advised for each breast, both for screening and diagnostic mammograms. Additional CC and MLO views with implant displaced optimally are recommended for breasts with implants within. The minimum requirements for the MLO view include visualization of the pectoralis upto the level of the nipple, convex anterior border of the pectoral muscle, nipple in profile, and inframammary fold, which should be demonstrated and open. The minimum requirements for the CC view include visualization of the nipple in profile and retroglandular fat. The length of the posterior nipple line on CC should be within 1 cm of the length of the posterior nipple line on MLO view. Skin folds are to be avoided in both views.

Additional views (such as spot compression, lateral, laterally extended and medially extended CC) could also be acquired to demonstrate abnormalities better. In the case of palpable masses, special attention must be paid to confirm visualization of the palpable lesion on the mammograms. Repeat films may sometimes be required, but these must be minimized. Clinical needs and the ALARA principle should justify additional views and repeat images. Departmental policy on repeat exposures and other images must be followed. The technologist assesses the acquired images for adequacy of position and artifacts. The degree of autonomy of the mammographer and radiologist’s active supervision in these decisions depends on the mammographer’s work experience and expertise and should be decided by the supervising radiologist.

CC and MLO markers must be placed as per international practice in the lateral aspect of the CC view and the superior aspect of the MLO view. A skin lesion or mole that may mimic a mass on the mammograms should be marked on the skin with a tiny radiopaque marker, which should be smaller than the skin lesion. The mammographer should identify these at the outset, and mammograms should ideally be acquired after the marker is optimally positioned rather than repeating mammograms. This will avoid increased radiation dose to the patient. Palpable masses also should ideally be marked with a radiopaque marker. This helps identify the palpable mass on the mammograms, which is extremely helpful in cases with multiple focal lesions in the breast.

A review of all mammograms by the radiologist immediately after acquiring images is encouraged to decide the need for additional diagnostic views. However, if the local protocol allows, screening mammograms can be obtained in the absence of the radiologist. In this case, the lady must be recalled for further views.

1.3 Mammography personnel

1.4 Radiation dose & safety

In both full-field digital and screen-film mammography, the average glandular dose delivered by a single craniocaudal view of a 4.2 cm thick, compressed breast consisting of 50% glandular and 50% adipose tissue must not exceed 3.0 mGy (0.3 rad), although it is generally much lower.^[9] The digital mammography systems automatically calculate the dose, making dose assessment easy. The mammographer and radiologist must endeavor to achieve this by following the ALARA principle. All tests, for example, check mammograms after the machine is serviced, and must be on a mammography phantom, not a patient.

The requisition form must justify mammography; if any doubt exists, the referring doctor should be contacted before radiating the patient. Every patient must be questioned about a recent mammography examination. If mammography has been performed within the last year, mammography should be performed only if clinically justified and after discussion with the radiologist. If good-quality mammograms have been acquired at one hospital, they must not be repeated at the hospital where a second opinion is being given. If a repeat is required, only those views that were suboptimal in the first instance should be repeated. At six month follow up mammography for a BI-RADS 3 lesion, unilateral mammography of the side of concern must be performed rather than bilateral mammography.

To avoid radiation incidents, the mammographer must confirm the patient’s name and unique hospital identification number before performing mammography. After obtaining the MLO and CC views, further views should be acquired only if it is expected to add additional information or clarify doubts arising from the basic images.

Routinely wearing a lead shield or apron is not recommended as most of the dose to the organs results from scattering in the breast tissue and entering the trunk through the breast, and this minimizes the benefit of wearing a lead apron.^[10]

1.5 Stereotactic biopsy

The stereotactic breast biopsy team should be adequately trained regarding the equipment, procedures, and possible complications. The technologist should be well versed in mammography and preferably undergo three months of observation or supervised training for stereotactic biopsy at a specialized breast unit. Dedicated training by the application specialist of the manufacturer and performance of stereotactic procedure under the supervision of the application specialist before independently performing the biopsy is also acceptable.

The breast radiologist performing the procedure should be trained in stereotactic procedures at a specialized breast unit before performing stereotactic procedures independently. A minimum of 150 supervised image-guided breast procedures (ultrasound and mammography-guided procedures included) must be completed over 1 year to train adequately. A minimum of 60 image-guided breast procedures (both ultrasound and mammography-guided procedures included) per year are recommended to maintain interventional breast imaging skills. The radiologist performing image-guided breast procedures must be well-versed in mammography and breast ultrasound interpretation, as this knowledge is essential for Radiology – Pathology correlation.

A stereotactic biopsy may be performed with a dedicated prone table setup, or with an add-on stereotactic device on the mammography machine and patient sitting on an adjustable chair. All equipment must be calibrated as per the manufacturer’s guidelines. Quality control tests for the mammographic unit used to perform stereotactic biopsy are as per the manufacturer’s instructions and AERB regulations.

At the time of installation of the stereotactic unit, an initial comprehensive performance test is to be performed by the engineers.^[16] Mechanical stability of the free-standing unit, smooth motion of the moving parts, stability of the image receptor holder assembly, adequate support for the needle holders & needle guides, and adequate radiation shielding for the operator/technologist have to be checked and documented at the time of the installation of the unit.^[16] This must be repeated each time the mammography machine is serviced or repaired due to any equipment breakdown. Annual quality check by a medical physicist to assess mechanical components of the equipment, collimation, focal spot performance, accuracy of kVp, half-value layer assessment, AEC performance, radiation dose assessment, and image quality evaluation is advised.^[16]

Prior to the procedure checks must be performed by the mammographer as per manufacturer’s instructions to check the accuracy of stereotaxis. On the accuracy test, each of the indicated needle tip coordinates (x, y and z axes) should be within 1 mm of the actual preset needle tip location. The difference between the preset and computer-determined locations should be less than 1 mm in each direction.^[17] If a localization phantom is used, the localization accuracy test should result in the needle tip within 1 mm of the targeted phantom location in each direction.^[17]

The operator should obtain written informed consent before the procedure after explaining the steps of the procedure and the possible complications such as hemorrhage, infection, retargeting, and repeat procedure. Instructions about post-procedure care should be duly explained to the patient by the radiologist conducting the procedure. History of allergy to drugs must be checked and documented.

Optimal precautions, such as using sterile gloves for performing the biopsy, are mandatory. The needle length, gauge, and throw should be confirmed before opening the sterile packaging of the core or vacuum-assisted breast biopsy (VABB) device. The VABB equipment must be calibrated before the start of the procedure. The concentration and expiry date of the local anesthetic must be checked while preparing the procedure tray.

During the procedure, images that demonstrate the important steps must be saved. The images should have the patient’s name, UHID number, date, indication of right or left breast, name of hospital, and other details as per local protocol. A pre-procedure scout image documenting the lesion that is being targeted (typically microcalcifications), pre-procedure stereotactic pair images, pre-fire, and one set of post-fire stereotactic pair images would be a good set of images to save for future records. A radiograph of the samples acquired must be saved for microcalcifications to document adequate sampling. As the risk of insufficient sampling is greater if no calcifications are seen on the sample radiograph,^[18] further sampling, sometimes after retargeting, should be attempted. A post-procedure scout image (demonstrating partial or complete removal of lesions) is also advised, especially if the lesion biopsied is not calcified and hence, radiography of samples cannot be used to confirm adequate sampling. If a marker clip is deployed (for example, following the complete removal of the targeted lesion), an image demonstrating optimal marker clip placement should also be saved. After the procedure is completed, formal CC and lateral mammograms of the ipsilateral breast are performed to confirm the position of the marker clip.

Special attention must be paid to the disposal of all the sharps used during the procedure per hospital protocol. The biopsy room must have a sharps bin for discarding the needles used during the procedure.

The report should contain details about the lesion targeted, direction of compression, approach, type of biopsy equipment (fully automated core biopsy or vacuum-assisted biopsy), gauge of the needle, number of core specimens obtained, time of obtaining specimen and fixing in formalin, findings of radiograph of samples if any and post-procedure clip position if a marker clip has been positioned. Complications of the procedure, if any, should also be documented in the report. For example, if the post-biopsy mammograms demonstrate displacement of marker clip from the biopsy site, that must be documented.

Explicit mention of the clinical history, pertinent imaging findings, likely imaging diagnosis, name of the procedure (core or VABB), side (right/left breast), and anatomic location depicted by o’clock position, and distance from nipple should be mentioned on the pathology requisition form. Patient name, identification number, examination date, facility name, side (right/left breast), and procedure name should be mentioned on the container where the sample is placed. After the histopathology report is ready, the radiologist should correlate the radiological features with the pathology findings and add an addendum regarding radiology-pathology concordance. If discordance is found, repeat biopsy, follow-up scan, or investigation of the breast with a different modality, such as MR, should be advised as appropriate. Discussion with the referring clinician is of utmost importance in case of discordance.

Other mammography-guided procedures, such as hook wire localization and marker clip placement, should be similarly consented to, documented, and reported. This applies to tomosynthesis-guided procedures as well.

1.6 Digital breast tomosynthesis

Digital Breast Tomosynthesis (DBT) is an active area of research and development with evolving clinical roles. DBT is a quasi-3D imaging technique in which the X-ray tube rotates along an arc around the breast and acquires several low-dose images. The relative positions of structures at different depths in the breast change on the image at different angles. A 3D data set is reconstructed from these projection images and viewed as thin slices. The number of DBT installations in India is on the rise. As India embraces the clinical implementation of this technological advancement, attention to QA parameters is paramount. Due to the wide variation in hardware and processing algorithms used by different manufacturers, adherence to the manufacturer’s QC tests becomes even more important with DBT systems. QA guidelines that may be suitable in the Indian context have been recommended in this document. Several international guidelines have been referenced for this purpose.

1.7 The reporting station

Luminance of the viewing light box should be a minimum of 3,000 candelas per square meter (cd/m²) for screen-film mammography and the display of digital images printed on films.^[28] Ideally, viewing boxes of appropriate size are required to allow comparison with previous mammograms. All tubes may need simultaneous replacement to ensure they are of the same color and intensity, maintaining uniformity.

Ambient lighting must be conducive to reporting. Room lighting should be indirect, and care should be taken to ensure that no illumination from room lighting falls directly on the reporting monitor. The ambient lighting must not exceed 20 lux and should be assessed as part of Mammography QA.^[19] The visual inspection of ambient lighting should be done daily by a designated QA technologist.

Two 5-megapixel monitors are advised to display images at the radiologist’s reporting workstation. The monitors must be checked annually by the medical physicist or a biomedical engineer, per local protocol. One 3-megapixel monitor should be available for technologists close to the image acquisition area. This can include the acquisition station itself.^[18]

At the radiologist’s workstation, multiple layouts of image display can be arranged, and a hanging protocol for image display can be set up per the radiologist’s preference. It is advisable to print the right and left MLO images side-by-side with the posterior part of the images facing each other to optimize the detection of asymmetries. CC images should be displayed similarly to printed images. Comparison of current studies with prior examinations is strongly recommended. To facilitate meaningful comparison, the printed images should have the magnification factor documented on them so that comparison of the size of abnormalities is possible even at other centers if required. Mammographic displays should allow fast and easy navigation between previous and current studies and between 2D and DBT images.^[28] Therefore, storage requirement estimates should consider the need to store and access current and prior images. Prior examinations may be imported from portable media. Digital mammogram image compression can provide more efficient transmission and storage. Wherever picture archiving and communications system (PACS) is used, it must be ensured that the quality of patient images is maintained in the PACS system and 5-megapixel mammography display systems are used for reporting. A lossless compression must be used during image storage or transfer. Thereby, by definition, there is no impact on the image; thus, optimum image quality is ensured for interpretation.^[19]

Routine cleaning of monitors and viewing boxes with cleaning agents as per manufacturer’s choice is advised. Cleaning the monitor to keep it dust-free is recommended at least once a week.

Images should be printed using films and printers compatible with the mammography machine as the manufacturer recommends and per the local hospital regulations.

DR and CR facilities should maintain mammography images and reports in the patient’s permanent medical record for a period not less than five years.^[29] Traditional film-based mammography units may save reports only for the same duration as the printed images are given to the clients.

1.8 Audits

An audit of mammography acquisition is advised once a year for each mammographer. This should include an audit of retakes due to suboptimal positioning or other factors. A good example is categorizing mammography positions as perfect/good/moderate/poor (PGMI) and auditing to see if each mammographer achieves 50% or greater P or G ratings in a PGMI evaluation of 50 randomly selected image sets.^[30]

An audit of radiation dose per mammogram should also be performed at least once a year in the unit.

An audit of breast radiologists’ performance should be conducted annually. This should include a review of appropriate clinical indications, accuracy of reports, and correlation with pathology reports to check the adequacy of sampling in cases of stereotactic procedures.

An audit of stereotactic procedures should be performed in the unit annually. The total number of stereotactic biopsies performed, the total number of cancers detected, benign lesions detected, inconclusive results requiring repeat biopsy, and complications should be analyzed.^[31]

In units with DBT, additional dedicated DBT medical audits are advised, particularly in screening settings, to distinguish between the two modalities concerning performance. Examinations should be systematically reviewed and evaluated as part of the overall quality improvement program at the facility. Monitoring should include evaluating the accuracy of interpretation and the appropriateness of the examinations. Complications and adverse events or activities that may have the potential for sentinel events must be monitored, analyzed, reported, and periodically reviewed to identify opportunities to improve patient care.

Records of all audits and training activities must be maintained in the department. The lead radiologist oversees planning the audits as well as applying the findings of the audits to enhance patient care.

1.9 Teamwork & multidisciplinary meetings

For QA measures to be effective, all team members must understand their roles and participate actively in the program. Radiologists, radiographers, breast care nurses, medical physicists, information technologists, and healthcare managers must work together for a good QA program to make a difference for our patients.

Each mammography unit should develop policies and procedures for quality control and assurance, infection control, and patient safety. These should be documented and kept in the breast imaging and intervention department. These should be readily available to all team members. Audits to check compliance with local policies should be encouraged.

Regular multidisciplinary meetings (MDM) should be held so that clinical features, imaging findings, and results of biopsies can all be well correlated and appropriate decisions on the next best step for the patient can be taken on a case-to-case basis. Participation in the MDMs must be mandatory for all doctors and breast care nurses. Representation from consultant-level team members of all specialties must be required at any given meeting.

1.10 Nuclear medicine

Centers with PET CT and sentinel lymph node biopsy facilities must follow AERB rules for nuclear medicine facilities. Radioisotopes handled, handling facilities, imaging equipment, availability of operating personnel and their monitoring, measuring instruments/protection level equipment (such as radiation survey meter, contamination monitor, dose calibrator, dosimeters), availability of documents (such as minutes of local safety committee meetings, patient information data), are all checked during the AERB regulatory inspection, the frequency of which depends on the nuclear medicine equipment available on site.^[3]

2.1 Equipment and technical settings

A high-resolution probe (such as 12 – 5 MHz, 18 – 6MHz) with a center frequency of at least 10 MHz is required to perform breast ultrasound.^[8,18] However, a convex probe may sometimes be used depending on the breast size and the lesion’s depth.

The patient is examined in a supine or oblique position. The medial portion of the breast is imaged in a supine position with the arm placed above the head. The side being examined is lifted (the lady turns to the opposite side – semi-lateral decubitus position), and the arm is placed above the head to ensure that the breast is flattened over the chest wall while scanning the lateral aspect of the breast. Applying a coupling agent such as gel on the skin is mandatory for ultrasound studies. A focal thick layer of gel on the skin at the site of a superficial lesion helps bring the superficial lesion into the focal zone and improves visualization of the abnormality.^[8] A similar technique can be used to visualize structures in the nipple-areolar complex. Scanning obliquely also helps visualize lesions in the nipple-areolar complex region. Gentle pressure while scanning allows better visualization of structures in the breast.

Optimization of grayscale settings is the first step towards obtaining good-quality representative and diagnostic images.^[18] The focal zone should be set at the level of the lesion being assessed. Gain should be set such that subcutaneous fat appears medium gray.^[8] Depth is considered optimal when most of the screen is occupied by breast tissue and the chest wall is seen at the posterior margin of the screen.^[18] Tissue harmonics, spatial compound imaging, color, and power Doppler should be used when required. The color box should be placed over the region of interest, and only gentle pressure must be applied while scanning to get the best results in color flow imaging.

Equipment performance monitoring should follow the manufacturer’s instructions and local departmental protocol.

Both strain elastography, and shear wave elastography are useful as adjunct to grayscale ultrasound. Elastography findings aid diagnosis but should not be used in isolation to evaluate a lesion. Using a linear probe, it is assessed in the same standard patient positions as those for grayscale ultrasound. While performing elastography, it is essential to ensure that the lesions of interest and the surrounding normal breast parenchyma are included within the elastography box, thus enabling the comparison of elasticity parameters. Different vendors and machine settings offer variable color coding methods (varying from hard to soft). Therefore, this has to be annotated in the image to avoid confusion.

2.2 Training requirements of doctor performing breast ultrasound

Radiologists who supervise, perform, and interpret breast ultrasound examinations should hold a degree in Radiology recognized by the National Medical Commission of India. A breast fellowship course or training under an experienced breast radiologist is strongly recommended before performing breast ultrasound and ultrasound-guided interventional procedures independently. The radiologist should have a thorough knowledge of the indications for ultrasound examinations and should direct each examination per the indication. For example, in a patient with nipple discharge, intraductal lesions should be vigilantly looked for. The radiologist should also be able to correlate an abnormality seen on ultrasound with findings seen on mammograms and breast MRI, considering clinical findings, if any.

The radiologist is expected to perform at least 1,500 breast ultrasound examinations under supervision over 1 to 2-year period, depending on the caseload of the institute, to complete adequate training. A minimum of 500 breast ultrasound studies per year is recommended to maintain their skill.

2.3 Reporting and documentation

Ideally, the request form for breast ultrasound should provide relevant history, clinical examination findings with a diagrammatic representation of any lump if palpable, and a provisional diagnosis. A standard requisition form approved by the hospital/radiology department is encouraged.

If available, ultrasonography has to be correlated with other breast imaging studies, such as mammograms or MRIs. Comparison with previous breast imaging should be performed. The findings of correlation with other imaging modalities and comparison to prior images must be documented in the report. Correlation with physical examination directed to the area of concern should be made.

Breast ultrasound includes an assessment of the axilla. The ipsilateral supraclavicular fossa, infraclavicular fossa (level 3 axillary lymph nodes), and internal mammary lymph nodes should also be checked for newly diagnosed breast cancer to quantify locoregional lymph node disease.^[35,36] Lesion characterization with documentation of sonographic characteristics of the lesion, such as size, shape, margin, orientation, echo pattern, posterior acoustic features, and surrounding tissue should be performed. Color flow and Doppler findings, if applicable, should also be reported. Each lesion should be identified and described. If there are multiple lesions with similar characteristics, they can be described collectively. Lesion description should be followed by the most likely diagnosis and the likely nature of the lesion, such as benignity or the possibility of malignancy. Of the established reporting systems, the most widely used system in our country is the Breast Imaging Reporting and Data System (BI-RADS) of the American College of Radiologists (ACR), and usage of such established reporting systems helps uniformity of lexicon in ultrasound reporting.^[8] If elastography is performed, findings should be documented. In strain elastography, size ratio and strain ratio values should be documented. In shear wave elastography, elasticity value should be documented in kilopascals (kPa) or meters/second (m/s).^[37]

Images showing relevant findings should be recorded and saved to be reviewed later.^[38] Image of a lesion should have documentation of its anatomic location (breast/axilla/chest wall), side (left/right), orientation of the transducer (radial/antiradial/transverse/longitudinal), quadrant and o’clock position, distance from the nipple in centimeters. Recording the depth from the skin is very useful if two lesions with similar appearance are at the same o’clock position in the breast. Abnormality should be recorded in two perpendicular projections. Two sets of images with and without calipers are preferable, especially for tiny abnormalities, as the cursor may obscure the lesion.^[8] Measurements of masses should be taken in three dimensions. Color Doppler images assessing the vascularity of the lesion should also be recorded separately.

Ultrasound images should have details of the hospital’s name, UHID, the date of examination, the patient’s first and last name, and date of birth. A radiologist’s identification number or initials should also be preferably recorded.

The minimum number of recorded, saved, and printed images should be as per the departmental protocols. A negative whole breast ultrasound should be documented with representative images of all quadrants, retroareolar region, and axilla. Important findings of targeted ultrasound of an area, such as assessing a mammographic asymmetry, should also be documented.

2.4 Ultrasound-guided breast biopsy (and other procedures)

Radiologists who perform breast interventions should hold a degree in Radiology recognized by the National Medical Commission of India. The radiologist should perform ultrasound-guided interventional procedures under supervision until they can perform interventions independently. They must be trained regarding equipment, procedures, and potential complications, preferably at a specialized center performing breast imaging and interventions. A minimum of 150 supervised image-guided breast procedures (ultrasound and mammography-guided procedures included) should be performed over 1 year to train adequately. A minimum of 60 image-guided breast procedures per year (ultrasound and mammography-guided procedures included) are recommended to maintain interventional breast imaging skills. The radiologist performing image-guided breast procedures must be well-versed in mammography and breast ultrasound interpretation, as this knowledge is essential for Radiology – Pathology correlation. The personnel assisting the radiologist should also be adequately trained and aware of the steps of the procedure and possible complications of the procedure.

Written informed consent must be obtained before the procedure. Explanation of the steps of the procedure and possible complications in lay terms for better understanding of the patient and their family members is mandatory before obtaining consent. History of allergy to drugs must be checked and documented.

Optimal precautions, such as using sterile gloves and drapes for the procedure are mandatory. The needle length, gauge, and throw should be confirmed before opening the sterile packaging of the core biopsy device. The concentration and expiry date of the local anesthetic must be checked while preparing the procedure tray.

Ultrasound-guided breast interventional procedures such as core biopsies, vacuum-assisted biopsies, cyst aspirations, hook wire localizations, marker clip insertions, and fine needle aspiration cytology (FNAC) should be recorded with images and a formal report.^[39] Documentation of the lesion biopsied, number of core specimens obtained, time of obtaining specimen and fixing in formalin, should be made. Complications, if any, at the time of performing the procedure should be documented in the procedure report.

A thorough ultrasound examination of the area of concern should be performed before the intervention to confirm that the correct lesion is being targeted and to decide the intervention approach.^[40] Patient name, identification number, examination date, facility name, right or left breast designation, anatomic location depicted by clock position, and distance from nipple should be mentioned on the clinical images. Before the procedure, two orthogonal images of the lesion to be biopsied should be obtained for clinical record keeping. Pre-fire and post-fire images with the needle on the long axis should be obtained. A post-fire image in the orthogonal plane is also to be obtained to confirm the presence of the needle within the lesion.^[39,41,42] If a core biopsy of calcifications is performed under ultrasound guidance, specimen radiography must be performed to confirm sampling of calcifications.^[43]

For hook wire localizations and marker clip insertions, post-procedure mammograms must be performed to confirm the optimum position of the wire and marker clip on both craniocaudal and lateral views.

Following the procedure, sharps must be disposed of in separately assigned sharps bins as per institutional protocol. Instructions about post-procedure care should be duly explained to the patient by the radiologist conducting the procedure.

The pathology requisition form should mention the clinical history, pertinent imaging findings, and likely imaging diagnosis. Patient name, identification number, examination date, facility name, and right or left breast designation should be mentioned on the container where the sample is sent to the pathology department.^[41]

There should be a process for obtaining the pathology department’s cytology/histopathology report. It is considered good practice to add an addendum report stating whether the cytology/histopathology report is concordant or discordant with the imaging findings and communicate the final report to the patient and referring physician.^[41]

Annual audit of the total number of ultrasound biopsies performed (FNAC and core biopsy), the total number of cancers detected, benign lesions detected, inconclusive results requiring repeat biopsy, and complications (hematoma, infection, pneumothorax) post-biopsy is encouraged.^[41]

3.1 Equipment specifications

It is widely acknowledged that a magnetic strength of at least 1.5 Tesla is required to acquire good-resolution images. The minimum requirement is an 8-channel dedicated diagnostic breast coil to perform a quality breast MRI.^[45] Simultaneous bilateral breast imaging is advised as this allows better detection of abnormal, asymmetric morphology and enhancement.

It is essential to acquire images of high spatial and temporal resolution so that the abnormality can be morphologically differentiated from normal breast tissue and assessed optimally by the kinetics of the lesion after contrast injection. A slice thickness of 3mm or less is required, and in-plane pixel resolution should be 1 mm or less as this reduces volume-averaging effects to the minimum.^[46] To achieve a pixel size of not more than 1 x 1 mm, a matrix of at least 300 x 300 in a 300 mm field of view (FOV) is required.^[47] To detect lesions ≥ 5 mm in size, voxel size should be less than 2.5 mm in any direction.^[47]

The contrast in a 0.1 mmol/kg body weight dose should be administered as a bolus using a power injector followed by at least 10 ml of saline flush. It may be omitted if the study is performed solely to check implant integrity. As peak enhancement in breast cancer usually occurs within the first 2 minutes of contrast injection, the post-contrast sequences should be able to acquire data from the entire breast quickly, preferably 1 – 2 minutes per volume acquisition. Washout of contrast from malignant masses may be as early as 2 – 3 minutes post-contrast. Hence, a dynamic sequence must aid the measurement of contrast uptake at least at three-time points, i.e., a precontrast, 1-2 minutes, and a delayed volume acquisition of breast is necessary.^[47] The number of acquisitions can be more, depending on the local protocol. Apart from visual assessment, time-intensity curves must be calculated in regions of interest (ROI) for quantitative analysis of lesion kinetics. ROI should be 3 - 4 pixels maximum to reduce volume averaging.

Subtraction techniques are used for the assessment of enhancement of breast abnormalities. However, these are prone to misregistration artifacts due to patient motion between image acquisitions. Misregistration may result in nonvisualization of the lesion. Hence, it is crucial to incorporate fat suppression (FS) in the sequences acquired after contrast injection, which reduces fat signal and helps better visualization of the lesion. Protocols incorporating both fat suppression and subtraction can be used. Assessing the lesions on post-contrast subtraction images and the FS sequence images is important. Motion correction algorithms are advised to reduce motion artifacts in subtraction sequences.^[46]

3.2 Timing & technique

Studies have shown significant lower background parenchymal enhancement (BPE) in menstrual cycle days 7-20 than in days 21-6.^[48] It is also advised that a dynamic breast MRI should be performed during the first half of the menstrual cycle (days 3-14) so that interpretative difficulties related to gadolinium uptake due to normal hormonal fluctuations during the menstrual cycle can be minimized.^[49] Breast MRI should be performed as per the departmental protocol. One suggestion is that breast MRI is performed between days 7–14 of the menstrual cycle.^[18]

A dedicated bilateral breast coil must be used. The patient is positioned prone with the breasts hanging in the coil loops. Supporting the breast helps reduce motion artifacts, but breast compression should be avoided.^[47]

Several sequences help the characterization of breast abnormalities. T2 weighted sequence (2D/3D), with or without fat saturation, is beneficial for analyzing cysts, edema, and fluid. T1 weighted sequence without fat suppression to assess the morphology of the lesion, fat signal intensity within the lesion, architectural distortion, and clips after biopsy/surgery is recommended. STIR silicone selective axial/sagittal sequence with water saturation demonstrates hyperintense silicone and helps assess implant integrity. Also, a suppressed sequence on which water is hyperintense is useful for implant evaluation. Dynamic contrast T1 Gradient echo (GRE) sequence is essential to assess tumor kinetics. Pre-contrast T1 FS sequences followed by at least two post-contrast T1 FS sequences with subtraction images are advised.^[47] A suggested protocol of each acquisition period of not >60 seconds (preferably not >45 seconds) for a total acquisition time of five minutes gives a good number of time points to draw the time-intensity curves.^[45]

Diffusion-weighted imaging (DWI) is a promising MR technique that gives insight into the functional aspect of the lesion. This may be used depending on the equipment capability and experience of the radiologist. It helps to differentiate between benign and malignant lesions based on the diffusivity of water molecules. Malignant lesions show less diffusivity due to increased cellularity and desmoplastic reaction than benign lesions. Thus, these are hyperintense on higher b values and have low values on ADC (Apparent Diffusion Coefficient) images. The high b-value images should always be seen in correlation with the ADC maps. A minimum of two sets of images are acquired with different b values; the recommended b values are 0 and 800.^[50] The higher b value applied can vary from b800-1000 according to magnet strength.^[45] The ADC value is obtained by drawing an ROI on the lesion on the ADC map (or the b = 800 s/mm² image when the workstation allows propagation of the ROI to the ADC map). The ROI should fall completely within the lesion, contain at least 3 voxels, and avoid the lesion’s artifacts and necrotic or hemorrhagic parts.^[50] DWI is performed before contrast administration to reduce artifacts.

Spectroscopy may be used depending on the equipment capability and experience of the radiologist. Choline is the metabolite detected and measured in single-voxel spectroscopy and is used to differentiate between benign and malignant lesions. It is also used to predict response to neoadjuvant chemotherapy in malignant lesions.^[51]

3.3 Quality assurance of the equipment

Quality assurance assessments should be performed per the manufacturer’s instructions and hospital protocol. Evaluation of the quality of the images for spatial resolution, fat suppression, and testing of the breast coil should be performed by qualified medical physicists at regular intervals. The MRI breast examination should also be systematically examined and evaluated for quality control and improvement. Any adverse reactions or complications during the procedure should be reported and analyzed as a part of the quality control program in the hospital. For reporting standards and image output, in-house and external periodic auditing should be done.

3.4 MRI guided biopsy

Suspicious findings seen only on MRI with no correlating abnormality on second look breast ultrasound must be biopsied under MRI guidance. A vacuum-assisted breast biopsy (VABB) device should be used. The breast should be immobilized between the grid plates. Too much compression should be avoided to prevent nonvisualization of the lesion. A marker clip placement is mandatory following a biopsy. The marker position must be confirmed on post-procedural mammography in two orthogonal planes.^[52]

The operator should obtain written informed consent before the procedure after explaining the steps and the possible complications, such as hemorrhage, infection, and procedure cancellation due to the nonvisualization of the lesion. Instructions about post-procedure care should be duly explained to the patient by the radiologist conducting the procedure. History of allergy to drugs must be checked and documented.

Optimal precautions, such as using sterile gloves for performing the biopsy, are mandatory. The needle length, gauge, and throw should be confirmed before opening the sterile packaging of the VABB device. The VABB equipment must be calibrated before the start of the procedure. The concentration and expiry date of the local anesthetic must be checked while preparing the procedure tray. Special care must be taken to use MR-compatible equipment for the procedure.

Images that demonstrate important steps of the procedure must be saved during the procedure. The images should have the patient’s name, UHID, date, an indication of right or left breast, name of the hospital, and other details per the local protocol. Special attention must be paid to the disposal of all the sharps used during the procedure as per the hospital protocol.

The report should contain details about the lesion targeted, the type of biopsy equipment, gauge of the needle, the number of core specimens obtained, the time of obtaining the specimen and fixing in formalin, and the post-procedure clip position. Complications of the procedure, if any, should also be documented in the report. For example, if the post-biopsy mammograms demonstrate displacement of marker clip from the biopsy site, this must be documented.

Clear mention of the clinical history, pertinent imaging findings, likely imaging diagnosis, name of the procedure (VABB), side (right/left breast), the anatomic location depicted by the o’clock position, and distance from the nipple should be mentioned on the pathology requisition form. Patient name, identification number, examination date, facility name, side (right/left breast), and procedure name should be mentioned on the container where the sample is placed.

The cancellation rate for MR-guided biopsy due to the inability to visualize the targeted breast lesion at the time of biopsy after intravenous contrast injection ranges from 8% to 13%.^[53] Nonvisualization of the target is an absolute contraindication to MRI-guided breast biopsy. Before canceling the procedure, it should be verified that the patient received a successful bolus of contrast and that excessive breast compression does not impede blood inflow. As there is a 0%–10% malignancy rate for lesions not visualized at the time of attempted biopsy, a follow-up diagnostic MRI should be obtained within six months to ensure the lesion is absent.^[53,54]

The radiologist performing MR-guided breast biopsies must be well-versed in breast MRI, mammography, and breast ultrasound interpretation, as this knowledge is essential for correlating MRI findings with mammography and ultrasound findings. This knowledge is critical for performing second-look ultrasound for MRI-only lesions. After the histopathology report is ready, the radiologist should correlate the radiological features with the pathology findings and add an addendum regarding radiology-pathology concordance. If discordance is found, appropriate advice must be given. Discussion with the referring clinician is of utmost importance in case of discordance.

3.5 Qualifications and responsibilities of the radiologist

The radiologist should hold a degree in Radiology recognized by the National Medical Commission of India. Interpreting radiologists should have broad knowledge of imaging and diagnosis of breast disease and, thereby, should be able to correlate MRI findings with Mammography and Breast Ultrasound. The slightly different positions in which a lesion may be demonstrated on a prone MRI, supine ultrasound, and an erect mammogram are best appreciated with a good knowledge of all three breast modalities. Additional training in breast MRI under supervision should be obtained before the radiologist reports breast MRI independently. Reporting a minimum of 150 MRI breast cases under supervision over 1 to 2 years, depending on the caseload of the institute is recommended before independent reporting.^[18] Taking up a breast fellowship course or training under an experienced Breast Radiologist is strongly recommended before performing breast MRI and MRI-guided interventional procedures independently. Subsequently, the radiologist is expected to report at least 50 breast MRI studies in a year to maintain reporting skills. Breast MRI should ideally be practiced in a facility having a capacity for mammography, ultrasound, and breast interventions, including MRI-guided biopsy. If very few studies are performed in a center or are not performed for lack of technology, such as a dedicated breast coil, the radiologist is encouraged to visit a center that performs a higher volume of breast MRI and stay in touch with the MR images and reporting. The radiologist must regularly attend educational courses to stay updated about MR technology and reporting techniques. If the center does not offer MRI-guided biopsy, a referral center with the facility should be accessible to the patient. The results of biopsies initiated on MRI findings require radiology-pathology correlation that should be tracked by the radiologist recommending the biopsy and the radiologist performing the biopsy at the referral center.

The Radiologist should review and validate clinical indications for the examination, set MRI protocol, use an adequate dose of contrast, ensure an emergency physician is available when contrast is given, interpret the breast MRI, including a review of pertinent prior breast imaging studies, and provide a report with recommendations. Established reporting systems such as the BI-RADS of the American College of Radiologists are encouraged for uniformity and standardization of reports.^[8] The salient features to be covered in the report have been enumerated in Appendix 4.9 of this document. All printed films and softcopies of the MRI images must be correctly labeled with the name, UHID number, date, side, and other details as per local protocol. Selected MR images that are printed are to be decided by the radiologist and should include time-intensity curves of significant lesions.

3.6 Qualifications and responsibilities of the technologist

The technologist must have a 2 or 3-year diploma or degree such as Diploma in Radiography, Diagnostic (DRD) recognized by the state/central government and have specific training in MRI as part of this training program. The technologist is expected to perform 20 breast MRI scans under supervision before performing a breast MRI independently. The supervised scans may be performed in a different center that has been performing breast MRI or can be in the technologist’s center under the supervision of a senior MRI technologist in the department or the application specialist of the MR manufacturer if breast MRI service is being newly set up in the hospital. The technologist should be able to manage the overall safety of the patient, staff, and equipment during the procedure. The contraindications for any routine MRI also apply to breast MRI, and it is the technologist’s responsibility to check for any contraindication based on the MRI questionnaire filled out by the patient. They should be able to produce high-quality images and adjust protocols as required. Technologists are encouraged to attend periodic educational courses for continuing upgradation of technical knowledge.