Comparison of Large-Core Vacuum-Assisted Breast Biopsy and

2.1 Introduction

The past 30 years have seen dramatic changes in the diagnosis and management of breast prob-lems. Much of this change has been driven by the quest for early diagnosis and by the wide-spread use of imaging in the diagnosis of symp-tomatic breast disease and for breast cancer screening. The traditional approach of surgical biopsy for diagnosis has now been replaced by needle biopsy techniques that provide both accurate and reliable diagnosis. The aims are to prevent unnecessary surgery for benign proc-esses and to provide detailed information on borderline and malignant processes that allow for prospective fully informed treatment plan-ning (Teh et al. 1998). To achieve these aims, specialized techniques for needle biopsy of the breast have been developed that facilitate the removal of sufficient amounts of tissue required to ensure accurate diagnoses.

In the 1980s, the predominant technique for needle sampling of the breast was fine-needle aspiration for cytology (FNAC). The results achieved with FNAC were encouraging but the required reliability and acceptable sensitivity and specificity proved to be only achievable in

expert centers. Even then, false-negative results for sampling in situ disease represented by microcalcifications and for certain types of invasive breast cancer were disappointing. For this reason, in the 1990s there was a trend away from the use of FNAC to needle core biopsy techniques. Core biopsy provides histological material for morphological as well as cellular assessment and the skills required for interpreta-tion are much more widely available. The sensi-tivity for the more elusive disease, such as lobular invasive carcinoma, is also significantly better. In addition, when sampling microcalcifi-cations, core samples can be imaged to prove retrieval of representative tissue. Overall, com-pared to cytology, core biopsy histology pro-vides significantly better sensitivity and positive predictive values for both benign and malignant disease and has a reduced rate of false-negative results. Automated core biopsy is now accepted as the preferred technique for breast tissue sampling (Bassett et al. 1997; Teh et al. 1998; Litherland 2001; Parker et al. 1996; Schueller et al. 2008).

Using core biopsy, the vast majority of breast abnormalities can be accurately diagnosed and most breast lesions are amenable to ultrasound-guided biopsy (Philpotts et al. 2003). However, particularly for screen-detected impalpable lesions, there remain around 5–10% of abnor-malities where core biopsy either does not pro-vide sufficient material for accurate diagnosis or does not target the lesion accurately (Parker and Burbank 1996). For these abnormalities, either more tissue or more accurate targeting is

Comparison of Large-Core Vacuum-Assisted Breast Biopsy and Excision Systems

Robin Wilson and Sanjay Kavia

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Robin Wilson ()King’s College HospitalDenmark Hill, London SE5 9RS UKe-mail: [email protected]

Renzo Brun del Re (Ed.), Minimally Invasive Breast Biopsies, Recent Results in Cancer Research 173, 23DOI: 10.1007/978-3-540-31611-4_2, © Springer-Verlag Berlin Heidelberg 2009

24 R. Wilson and S. Kavia

2necessary to achieve the tissue needed for reli-able histopathological assessment (Kettritz et al. 2003). With these two factors in mind, in the early 1990s techniques were developed to pro-vide both directional sampling capability and retrieval of larger volumes of tissue (Parker et al. 1994; Burbank 1993). These have been further developed and refined over the past 15 years and are now in routine use for both diag-nosis and therapeutic excision.

Two different approaches for large-core biopsy have been developed: multiple contigu-ous large-bore cores retrieved with the assistance of suction (vacuum-assisted mammotomy; VAM) and single very-large-bore core (SLCB). Both methods can be used under X-ray (stereotactic guidance) and ultrasound, but currently only VAM is recommended for magnetic resonance (MR)-guided biopsy. With these techniques, it is now possible to retrieve sufficient tissue using image-guided biopsy such that 98–99% accuracy of nonsurgical diagnosis can be achieved. In fact, so much tissue can be removed that these tech-niques are now being used for total excision of certain breast abnormalities. Compared to core biopsy, VAM and very-large-core biopsy reduce by half understaging of pathology (atypical hyperplasia and DCIS), on average from 20 to 10%. This means that repeat biopsy and further surgery for diagnosis and treatment are required half as often (Liberman et al. 2000). Vacuum-assisted biopsy is the technique of first choice for MR-guided breast biopsy (Liberman et al. 2005; Kuhl 2007).

2.2 Large-Core Biopsy Systems: Overview

Currently one single large-core radiofrequency biopsy system and four vacuum-assisted multi-ple-core biopsy systems are in routine use for breast diagnosis and excision. All of the VAM systems are suitable for use under ultrasound,

stereotactic (upright and prone table), and MR imaging guidance; the single intact biopsy sys-tem is described as being suitable for ultrasound and X-ray stereotactic-guided biopsy. All the systems are suitable for use in the out-patient setting with local anesthesia.

2.2.1 Single Large-Core Biopsy System

The Intact Breast Lesion Excision System (BLES; Intact Medical Corporation Inc.) is a breast excision system that combines the use of vacuum and radiofrequency (RF) cutting to remove the targeted lesion as a single specimen (Intact Medical Corporation 2008). The probe (or wand) (Fig. 2.1) is available in four sizes, designed to retrieve specimens that are 10, 12, 15, and 20 mm in diameter (Fig. 2.2). The Intact BLES probe is positioned under imaging guidance (ultrasound or X-ray stereotaxis) through a 6- to 8-mm skin incision and advanced to the periphery of the area to be excised. A cutting RF wire is activated and advanced to cut and ensnare the target lesion by means of four insulated struts that first expand and then contract to surround the lesion (Fig. 2.3). The single large sample is then withdrawn intact through the same tract. Vacuum is used to minimize the extent of the RF effect on the sample excised and into the surrounding breast tissue and to extract any bleeding that may occur during the procedure. The Intact BLES system is said to have the advantage over VAM of retaining the full histological architecture and potentially clear margins around the area of interest and with little RF artifact on histology (Sie et al. 2006). It has also been reported to be associated with reduced understaging compared to VAM (Sie et al. 2006; Killebrew and Oneson 2006). However, the RF function does limit its use for lesions close to the skin or the chest wall and for lesions in small breasts.

2 Comparison of Large-Core Vacuum-Assisted Breast Biopsy and Excision Systems 25

Fig. 2.1 The Intact disposable wand (probe) and driver

Fig. 2.2 Intact whole-tissue samples showing the size of samples achieved with the 10-, 12-, 15-, and 20-mm wands

Fig. 2.3 Diagram of how the Intact system operates


22.2.2 Vacuum-Assisted Mammotomy Systems

There are four systems in routine use based on the principle of single or multiple cores using 14 to 7 French gauge needles or probes. Although the principles of operation are similar for all of these VAM systems, there are significant differ-ences in their design, method of operation, and attributes. Table 2.1 shows a comparison of the various attributes of these systems. All of these systems are directional, allowing sampling around a full 360-degree arc either by manual rotation of the driver or manual or automated

rotation of the needle within the driver. The EnCor system has fully automated and program-mable directional functions. Each system is described here in greater detail.

2.2.2.1 Mammotome System

Mammotome (Breast Care, Ethicon Endo- Surgery), the first VAM system to be developed and originally marketed under the Biopsys name, has been available since 1995, and has been upgraded several times since. It is a well-proven

Table 2.1 Comparison of VAM systems

Attribute Mammotome Vacora Atec EnCor

Drivers required Separate for US, X-ray, and MRI

Same for all Same for all Separate for MRI

Command unit Same for all Self-contained Various options Same for allVacuum adjustment No No Requires different

unitsYes

Manual vacuum control

+++ No + (With lavage) +++

Needle gauge 11 and 8 14 and 10 12 and 9 10 and 7Multiple core retrieval Yes No Yes YesCutting method Rotating Rotating Rotating ScissorNeedle sharpness ++ + ++ +++Core sample size ++ ++ ++ +++Volume of tissue per minute

++ + +++ +++

Open or closed tissue collection

Open Open Closed Closed

Smaller chamber size Choice

No No Requires different probe

Selectable with the same probes

Speed of tissue retrieval

++ + +++ +++

Needle rotation Manual only Manual only Manual only Manual or automated

Lavage No No Full Sample chamberProgrammable functions

++ No No +++

Biopsy site marker system

Yes No Yes Yes

Local anesthetic function

++ No ++ +++

Probe offset Yes Yes No Yes


device with more than 3 million biopsy procedures performed worldwide and more than 200 papers reporting various aspects of its use published in the medical literature.

This system uses three different drivers for stereotactic, ultrasound, and MR-guided biopsy (Fig. 2.4a, b). All three drivers use the same unique double-lumen probe, one lumen used for providing the suction (at 23–25 mmHg) that draws the sample into the biopsy chamber and the other through which the internal rotating cutting trocar moves to cut the sample and for retrieval of the specimen (Fig. 2.5). All three drivers are controlled by the same command module (Fig. 2.6) that can be programmed to individual preference for automated or semi-automated function with variable pause periods between each sample, application of suction sequences, and “clear” mode for “dry tap” events (Fig. 2.7). The control module can be operated via a foot switch or a handheld control-ler for sterotactic and MR-guided biopsy and via buttons on the driver itself for MR- and ultra-sound-guided procedures (Fig. 2.4). The com-mand module provides the suction via plastic tubing for all three uses and provides real-time pictorial feedback of all the functions, including the position of the cutting trocar and where in the system suction is being applied. Suction can be applied manually at any time during a biopsy

procedure to extract any bleeding or hematoma. Additional local anesthetic can be delivered through a port in the vacuum tubing during a biopsy. The needle bore and the biopsy can also have lavage applied if blockage occurs by injec-tion of saline through the same vacuum tubing port.

For stereotactic biopsy, the drive for the rotation and retraction of the cutting trocar is via torsion cables driven from the command unit, while for MR- and ultrasound-guided procedures, the drive for the cutter is incor-porated into the handheld device, allowing for more flexible use (Fig. 2.5). The stereo-tactic driver incorporates a spring-loaded system that allows the needle to be fired for-ward 20 mm into the breast while it is held in the stereotactic holder (Fig. 2.8). In all appli-cations, the mammotome is an open biopsy system and each core sample must be retrieved

a b

Fig. 2.4 Mammotome biopsy probes (a) ultrasound EX system and (b) stereotactic ST system

Fig. 2.5 Close-up view of the Mammotome probe tip showing the double lumen system with fenes-trations used to suck in the samples for cutting by the rotating inner trocar. A scalpel-type blade is embedded in the tip to ease insertion of the probe


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from the sample collection chamber after each biopsy (Fig. 2.9). The probes are dispos-able and are available in two sizes (11 and 8 G) for ultrasound, stereotactic, and MR use and are available with or without a cutting

scalpel embedded into the probe tip (Fig. 2.5). The 11-G probe provides approximately 100 mg and the 7-G probe approximately 175 mg of tissue per core sample. Special part-ceramic probes, guides, and introducers are

Fig. 2.6 The Encor (left), Atec (middle), and Mammotome (right) control modules

Fig. 2.7 The Mammotome control module monitor showing the operating functions


available to facilitate MR-guided biopsy using standard lateral grid MR biopsy coils. Various types of ultrasound and X-ray-visible biopsy site markers are available for use with the Mammotome probes, which are inserted through the probe directly into the biopsy cavity.

2.2.2.2 Vacora

The Vacora system (C.R. Bard Inc.) was the sec-ond device to become available for VAM (origi-nally marketed as the BIP VacuFlash). It is

a b

Fig. 2.8 The Mammotome ST system a showing the set-up for use with a lateral arm and b for biopsy of the inferior part of the breast using an upright dig-

ital stereotactic system (GE Medical Systems) with the patient in the lateral decubitus position

Fig. 2.9 The Mammotome ST system in use for biopsy of the upper breast in the craniocaudal position using an upright stereotactic system (GE Medical Systems) showing manual retrieval of a core sample


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unique in that it is a self-contained system incor-porating the driver for the rotating cutting trocar and the suction unit within the handheld unit (Fig. 2.10a, b). The disposable probes are single-lumen and contain a rotating cutting trocar. The probes are available in 14- and 10-G sizes, pro-viding approximately 50 and 150 mg of tissue per core sample, respectively (Fig. 2.11). The needle is directional but needs to be rotated manually in the holder to achieve different biopsy directions for stereotactic biopsy; for ultrasound- and MR-guided biopsy, the com-plete holder can be rotated for multidirectional sampling (Fig. 2.12). The Vacora is a single-sample system and the probe must be with-drawn from the breast to retrieve each core sample. For this reason a plastic guiding canula is best inserted into the breast first to facilitate repeated insertion of the probe to the same site in the breast. This single-sample function means that it is not suitable for therapeutic excision of anything other than small lesions (10 mm or less). The suction is only applied while the core is being taken and again when each core is

extracted. It is not possible to apply manual suction, and this limits its use when bleeding occurs at the biopsy site. Additional local anesthetic injection and biopsy site marking must be delivered through the guiding plastic

ba

c

Fig. 2.10 The Bard Vacora vacuum biopsy system: a the handheld device showing insertion of the nee-dle and the self-contained vacuum system into the

driver, b the system ready for use, and c a close-up view of the operating panel

Fig. 2.11 Comparative core sample sizes achieved with 14-, 10-, and 7-G vacuum core needles


canula. The system incorporates a spring-loaded firing mechanism that allows the needle to be fired forward into the breast. The system is simple to use because its functions are all preset and are activated using the control panel on the side of the device; changes to its operation cannot be programmed by the user.

2.2.2.3 ATEC (Automatic Tissue Extraction and Collection)

The Automatic Tissue Extraction and Collection (ATEC) system (Suros Inc.) is similar in its function to the Mammotome ST system in that it is driven by cables from the command unit and uses an internal rotating cutter. However, it is a single-bore system and the whole driver unit is disposable (Fig. 2.13). There are three different command modules available that deliver differing suction levels depending or required usage (MR only, ultrasound and stereotactic only, and all three). The disposable handpieces are available in two needle sizes in several lengths and sampling chamber sizes. Twelve-gauge needles are avail-

able in 9- and 12-cm lengths, both with 20-mm sampling chambers. The larger 9-G needles are available in 9-, 12-, and 14-cm lengths with the two shorter lengths available with either 20- or 12-mm sampling chambers (Fig. 2.14). The sampling processes are preset and not programmable by the user. All handpieces include a closed sample collection system (Fig. 2.14).

There are two operation modes that are used for all methods of image guidance (Fig. 2.15). In the lavage mode the sample chamber is open and saline is continuously instilled through the system into the biopsy area and through the sampling filter (Fig. 2.15). The ATEC is the only system that uses lavage of the biopsy area. Manual suction can also be applied (Fig. 2.15). In the biopsy mode, the sample chamber is closed in the resting position until the foot pedal is used to trigger multiple rapid retrievals of samples (averaging 150–175 mg per core). The ATEC is the fastest-acting VAM system, although it does not deliver more tissue per time unit than the EnCor system (see below). Directional sampling is achieved by rotating the handpiece manually (Fig. 2.16). The needle of

Fig. 2.12 The Bard Vacora system in use for MRI-guided breast biopsy. The black line on the back of the device indicates the direction of sampling


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the Suros ATEC system is not offset and this means that there may be restrictions on its use under stereotactic and MR guidance for lesions close to the chest wall and in breasts with a small compression thickness.

2.2.2.4 EnCor

The EnCor system (Senorx Corporation), like the Vacora and ATEC, is a single-bore VAM system. However, it differs from the other VAM systems in many ways. The inner cutting trocar, rather than rotating to cut the sample, uses a scissor oscillating action that is said to be more effective

for dense tissue and more prolonged use. The driver contains the mechanisms for driving the cutting device and for rotating the needle (Fig. 2.17). The driver has an electrical cable and plas-tic vacuum tubing that connects it to the com-mand module. The same command module is used for ultrasound-, X-ray stereotactic-, and MR-guided biopsy (Fig. 2.6). The functions are fully programmable by the user, including auto-mated rotation of the biopsy sampling chamber, which can be set for single, three (180°), six (270°), and eight (360°) rotations in any direction (Fig. 2.18). The automated function of the probe rotation is particularly useful for stereotactic and MR-guided biopsy, as the sample selection direc-tion and extent of rotation can be preset. The driver unit is lightweight and handheld for ultra-sound-guided procedures (Fig. 2.19). The same driver is attached to a holder for either prone table or upright stereotactic use (Fig. 2.20). The stereotactic probe holder has a spring-loaded mechanism that allows the driver and probe to be fired forward 20 mm into the breast.

The needle probes are available in 10- and 7-G sizes. Both have the patented tri-concave tip design that renders the probe extremely sharp so that it passes through all but the most dense breast tissue with ease (Fig. 2.21). The 7-G probe provides the largest samples of all the VAM systems at 300 mg per core sample. The sample

ba

Fig. 2.13 The Suros ATEC biopsy device a showing the component parts with the disposable driver and detached closed sampling chamber and b close-up of the closed sampling chamber in place

Fig. 2.14 The Suros ATEC needles showing the 9- and 14-cm lengths


chamber length (10 or 20 mm) for the two needle sizes can be set at the control module and avoids the need to select a different needle if a short core length is required. The strength of the vac-uum applied can also be doubled when particu-

larly dense tissue is encountered. The module also has a preset anesthetic function that allows for delivery of local anesthetic 360° around the biopsy site either before or during the biopsy procedure. The same system is used to deploy

Fig. 2.15 The Suros ATEC control system

Fig. 2.16 The Suros ATEC system in use for ultrasound-guided biopsy


2a b

c

Fig. 2.17 The EnCor biopsy system: a the driver unit and disposable needle, b close-up of the closed sample retrieval component, in place and c detached

Fig. 2.18 The Senorx EnCor control display


gel and clip markers at the biopsy site (Fig. 2.22). The closed sample collection system retrieves the samples in an easily removable basket that

can also be used for sample radiography. There is an optional lavage system that uses saline to cleanse the tissue samples in the collection chamber as they are retrieved. Like the Mammotome and ATEC systems, the EnCor device can be used with MRI-specific introducers and trocars (Fig. 2.23a, b)

2.3 Indications and Limitations

There are a number of diagnostic and therapeu-tic situations where VAM or SLCB should be considered as the primary technique. These include:

Fig. 2.19 The Suros EnCor system set up and ready for handheld use

Fig. 2.20 The Suros EnCor system in place for ster-eotactic-guided biopsy using a prone table

Fig. 2.21 Close-up of the Tri-concave EnCor needle tip


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Diagnostic biopsy:

– Equivocal or failed core biopsy– Small lesion (sub 5 mm)– Architectural distortion– Clustered microcalcifications– Diffuse nonspecific abnormality– Complex cyst– Intraductal lesion– Abscess drainage

Therapeutic excision:

– Fibroadenoma and other biopsy-proven benign lesions

– Papillary and mucocele-like lesions

– Radial scar/complex sclerosing lesion– Sentinel lymph node

2.3.1 Limitations

The various differences in the attributes of the large-core systems mean that some are not suited for all of the possible indications. The Vacora system has the most limitations because it is a single-core device that needs to be removed from the breast to retrieve each sample and cannot be used to aspirate the biopsy area.

a

b

Fig. 2.23 The EnCor system: a MRI trocar and can-ula guides and b in use for MRI-guided biopsy

Fig. 2.22 The Encor a anesthetic control display and b method of injection of anesthetic through the probe system to the biopsy site

a

b


2.3.2 Diagnostic Biopsy

When conventional automated core biopsy has either failed to target the lesion or there is a bor-derline pathological result, VAM or SLCB will usually provide the material required to either avoid unnecessary surgery for benign lesions or facilitate single-stage therapeutic surgery for malignant disease. In certain circumstances where there is a high chance of failed sampling with core biopsy, such as small clusters of suspi-cious microcalcifications and very small mass lesions, it is usually better to use VAM or SLCB as the primary sampling technique without attempting core biopsy first (Fig. 2.24a–c).

The same is true for circumstances where from the outset it is recognized that larger vol-umes of tissue will be required for diagnosis, such as suspicion of radial scar and diffuse non-

specific changes on imaging. All of the systems described here are potentially suitable for these indications, as previously described. The Intact system is not suitable for superficial lesions and the Vacora system is not ideal if more than 10–15 cores are likely to be necessary.

Similarly, the Intact and Vacora systems are not ideal for sampling complex cysts, particularly those that appear to contain a mass component. These are best biopsied by VAM devices where the probe remains in position in the breast throughout the procedure and manual vacuum can be applied. The same is true for removal of an intraductal lesion when manual vacuum is an important factor, as is the ability to move the sam-pling chamber around the area without removing the probe from the breast (Fig. 2.25a, b).

VAM systems are most widely used for stereotactic biopsy of microcalcifications iden-tified on mammography, and all of those

ba

c

Fig. 2.24 Stereotactic procedure radiograph showing a an EnCor probe in place for biopsy of calcifica-tions, b core specimens in the sample retrieval tray, and c radiography showing calcifications success-fully sampled


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described here are suitable for this purpose. All of the upright and prone biopsy mammography systems can accommodate the VAM and Intact systems described here (Georgian-Smith et al. 2002). VAM is particularly suited for this situation, as the vacuum assistance means that sampling is directional and can be used to retrieve tissue at a distance from the actual site of the needle. For core biopsy, the needle must pass through the lesion for successful sampling, but with VAM the probe only needs to be placed close to the target area. The vacuum effect is used to pull the tissue into the sampling chamber. This is particularly useful for lesions close to the chest wall, and behind the nipple and where the cluster is more scattered. In many units now, all stereotactic biopsy procedures are carried out using VAM systems because the retrieval results are significantly better than core biopsy, and

particularly because equivocal pathology results and understaging of disease are much less fre-quent, making repeat procedures and the need for surgical biopsy much less common. Some clinicians prefer to map the samples retrieved in order to document where each sample has come from in the breast. It is not clear what the benefit of doing this is because it does not affect the subsequent management of the result and imag-ing provides the information needed if the first sets of samples do not contain sufficient mate-rial. If sample mapping is required the Vacora and Mammotome systems need to be used. For sampling lesions close to the chest wall or when using the lateral approach in women with small breasts, access to the breast requires a probe with the needle offset to avoid snagging on the biopsy table or the chest wall. The ATEC system does not have an offset needle.

Aspiration of breast abscess is preferred to surgical drainage and is usually achieved by manual suction applied through a standard nee-dle. However, VAM systems with continuous suction capability provide the means of dealing with larger and more organized breast abscesses when surgery would otherwise be required. The Vacora is not suitable for this use.

2.3.3 Therapeutic Excision

VAM and SLCB provide an alternative to surgery for the removal of known benign lesions such as fibroadenomas and focal fibrous lesions (Tennant et al. 2008). Large-core techniques are also being increasingly used instead of surgery to widely sample borderline lesions such as radial scars and papillary lesions shown on previous core biopsy to have no evidence of epithelial atypia (Rosen et al. 2002; Carder et al. 2008). The Vacora system is only suitable for removing small lesions less than 10 mm in diameter for the reasons outlined above. Similarly, the Intact system is limited by the size of its retrieval system, which has a maxi-

a

b

Fig. 2.25 Ultrasound images showing a an intraduct lesion and b an intracystic lesion, which are ideal for VAM excision


mum diameter of 20 mm. The Mammotome (7 G), ATEC (9 G), and EnCor (7 G) are all ideal for excision of large lesions. The Mammotome sys-tem takes longer to complete the task simply because each sample has to be retrieved from the sample chamber while with the other two the samples are automatically collected by their closed sampling systems. Many clinicians restrict the size of lesion they are willing to attempt to remove with VAM to around 20–30 mm. Both the EnCor and ATEC systems will retrieve more than 1 g of tissue per minute and can be readily used to excise lesions up to 50–60 mm in diameter.

There are also some reports of these tech-niques being used to sample sentinel nodes prior to surgery or primary chemotherapy treatment. However, this indication must be considered experimental at present. Similarly, SLCB and VAM should not be used for excision of known malignant lesions or borderline lesions associ-ated with a significant risk of breast cancer except in exceptional circumstances (Eby et al. 2008; Lee et al. 2008). In some patients who are not medically fit for conventional treatment (surgery and chemotherapy), SLCB and VAM can be considered. To ensure a reasonable exci-sion margin, the Intact system should be con-fined to lesions no more than 10–25 mm in diameter if a clear excision margin is to be achieved. The VAM system can be used for larger lesions but it must be recognized that the excision margins will be suspect, even if sample mapping is used.

As with all breast biopsies, ultrasound guid-ance is the preferred guidance method whenever possible. All of the systems described here can be used for ultrasound-guided biopsy. The Vacora system is usually used with a trocar. For stereotactic biopsy, this is satisfactory because the breast is fixed by compression. For ultra-sound, the trocar guide system can be less effec-tive, particularly in the large breast; since the breast is not fixed, it can be difficult to reintro-duce the needle to the same site for successive biopsies. The other VAM systems remain in the

breast throughout the biopsy procedure and are therefore easier to use in this situation. All of the systems are light enough to be easily handheld for ultrasound-guided use. The sharpness of the tri-concave tip of the Encor system means that it is more easily advanced through the breast to the target than the other systems and is more easily sited in the ideal position for ultrasound-guided VAM immediately behind the lesion (Fig. 2.21). This is particularly apparent in the dense and fibrous breast.

2.3.4 Image-Guided Biopsy Technique

Anyone familiar with the technique for image-guided fine-needle aspiration and conventional core biopsy will be able to adapt easily to the technique required for large-core biopsy because the basic principles are the same.

Particular attention must be paid to adminis-tration of sufficient local anesthetic for these large-bore procedures. Significantly larger doses are usually required than for conventional core biopsy, particularly for excision proce-dures and procedures done under ultrasound guidance. The larger size and vacuum assist-ance both mean that vessel damage is more likely with these techniques. The use of local aesthetic combined with adrenaline is preferred because this reduces the chances of hematoma and increases the time that the anesthesia is effective. Plain local anesthetic may be pre-ferred for the skin and subcutaneous tissues in older patients and those with compromised skin. For stereotactic X-ray-guided procedures, care should be taken not to inject large volumes of anesthetic since this can significantly displace the target area. The biopsy-targeting process is the same as for core biopsy with the aim of passing the probe directly through the area to be sampled and then biopsy around 360°. However, unlike core biopsy, successful sampling can be achieved if the lesion is not transfixed


2using the vacuum and directional capabilities of the VAM systems.

For ultrasound-guided sampling, the anes-thetic must be infiltrated to surround the lesion being targeted and can be used to dissect the tis-sue down to the lesion and to assist in separating the target from the deep and superficial tissues. Deep tissue anesthesia is particularly important, as for ultrasound-guided sampling the VAM probe is best positioned behind the lesion. Some also advocate the use of longer-acting local anesthetic in the deeper tissues around the target lesion to reduce postprocedure anesthesia.

All but the Vacora system allow for further injection of local anesthetic through the biopsy probe into the target area (Fig. 2.22b). This can be done as a matter of routine before the biopsy is commenced, particularly for stereotactic pro-cedures when the probe has been placed and dis-placement of the lesion is then less likely to occur. The EnCor device has a specific program for delivering local anesthetic around the area to be biopsied.

MR-guided biopsy can be achieved with all of the VAM systems described (Figs. 2.12 and 2.23b). All of the manufacturers provide MR biopsy packs that contain the necessary materi-als to carry out the procedure using most of the currently available MR biopsy coil systems (Fig. 2.23a). VAM is recommended for all MR-guided biopsies; these lesions are only vis-ible on MR and therefore the method most likely to successfully retrieve tissue from the targeted area should be used (Lee et al. 2008).

2.4 Conclusions

There are a number of well-designed devices available for vacuum biopsy and excision biopsy. These devices enable the radiologist to deliver a high level of diagnostic accuracy and

provide the means for minimally invasive ther-apeutic lesion excision of benign and border-line lesions. Accuracy approaching 99% can be achieved, thus avoiding the need for diagnostic surgical open biopsy in the vast majority of cases and providing tissue samples in quanti-ties sufficient to allow for detailed treatment planning. The choice of vacuum biopsy system will depend on workload, the image guidance methods that are used, and whether lesion exci-sion is required.

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Comparison of Large-Core Vacuum-Assisted Breast Biopsy and