The Use of Ultrasound in Biopsies and Procedures

M. Robert DeJong, Jr, RDMS, RDCS, RVT

     *Radiology Technical Manager, Ultrasound, The Russell H. Morgan Department of Radiology and Radiological Sciences, The Johns Hopkins Medical Institutions, Baltimore, Maryland.
     Address correspondence to: M. Robert DeJong, Jr, RDMS, RDCS, RVT, Radiology Technical Manager, Ultrasound, The Russell H. Morgan Department of Radiology and Radiological Sciences, The Johns Hopkins Medical Institutions, Halsted Building, Room B-176A, 600 N. Wolfe Street, Baltimore, MD 21287. E-mail: rdejong@jhmi.edu.

Disclosure Statement: Mr DeJong reports receiving honoraria from eRADIMAGING.com.

ABSTRACT

With their technical and communication skills, the sonographer can be a valuable member of the biopsy team. The sonographer can assist the sonologist in a variety of ways, including being responsible for the set-up of the transducer, communicating with the patient, and adjusting imaging controls. The sonographer can also look for any postprocedural complications, such as hematomas. Being involved with procedures offers new challenges to the seasoned sonographer, in addition to make the sonographer feel part of a specialized team.

Introduction
Ultrasound has been used to assist in interventional procedures since its early days using specially designed A-mode and B-mode transducers. Ultrasound-guided interventional techniques are continuing to improve with new developments in transducer and equipment technology and are being used to perform a variety of procedures on organs and masses located in the neck, chest, abdomen, retroperitoneum, and pelvis. Additionally, ultrasound can be used to drain fluid and abscess collections. Other imaging modalities that can be used to guide biopsies and procedures include computed tomography (CT) and fluoroscopy.¹ All imaging modalities have their strengths and weaknesses in performing procedures. In recent years, there has been a movement to perform more procedures under ultrasound guidance rather then using CT guidance.² Retroperitoneal masses, pleural-based masses, deep masses in the liver, and musculoskeletal masses that were once typically biopsied under CT guidance or in open surgical biopsies are now being successfully performed using ultrasound guidance.

Ultrasound is currently used in many ways. It is used to biopsy masses, organs for parenchymal disease, or transplant rejection and drain fluid collections, such as cysts, ascites, or pleural fluid. Ultrasound can also be useful to obtain samples of abscesses to determine the type of organism on patients that are not responding to antibiotic therapy; assist in placement of drainage tubes, catheters, and lines in arteries and veins; and to mark spots for biopsies or fluid taps to be performed without direct sonographic guidance.

One of the main advantages of using ultrasound for guidance is the ability to have continuous real-time visualization of the biopsy needle, which allows adjustment of the needle as needed. Also, as the biopsy specimen is being obtained, the needle tip can be monitored in real time to ensure that it stays inside the mass. This is especially important in small masses in which the needle may slip out of the mass resulting in normal tissue being biopsied. Ultrasound also has the advantage of allowing different approaches and patient positions to be considered. This can allow the use of steep angles from a subcostal approach decreasing the risk of a pneumothorax, which can occur when performing a biopsy using an intercostal approach. With ultrasound the patient can be placed in a comfortable position and not made to lie supine or prone. For example, the patient's head may be slightly elevated or they may be able to move slightly between biopsy samples to relieve back or joint pain. Another benefit is the ability for the team to comfort and reassure the patient as the radiologist, sonographer, and nurse are all constantly in the room with the patient during the procedure. Even the most anxious patient can be coached to cooperate when the team is by their side and not constantly in and out of the room. Other advantages include the lack of radiation, portability, and shorter procedure times. The disadvantages of using ultrasound for guidance include the inexperience of the ultrasound personnel, especially the radiologist; overlying bowel gas that cannot be displaced; and having to use fixed angles when using needle guides.

Ultrasound is a unique imaging modality in many ways. As a sonographer, there is an opportunity to be involved in ultrasound-guided procedures. In the early days of sonography, it was used to locate cysts, ascites, pleural fluid, or other fluid collections and assist in the drainage of the fluid. Aspiration would occur using specially designed A-mode or B-mode transducers that had a hole in the middle of the transducer to insert the needle. By watching the A-mode trace, the needle could be visualized by observing the tall spike appearing between the spikes that represented the walls of the cyst or fluid collection. Ultrasound was used to mark the fluid collection on the patient's skin and give the depth to the fluid. The physician would perform the procedure blindly, including amniocentesis procedures. If the fluid could not be obtained, the sterile field was broken, as the patient was rescanned and remarked. When real-time technology was developed, the needle tip could be followed while using free-hand techniques. This helped reduce the number of needle reinsertions because the cause of the fluid blockage could be determined. For example, a loop of bowel may have floated into the needle path while draining ascites causing the fluid to stop draining or the uterine wall may have contracted during the amniocentesis, pushing the fluid deeper. By finally being able to see the needle tip, the physician was able to safely advance or adjust the needle into the fluid. Physicians could also biopsy solid masses now with more confidence.³ With the development of needle guides that attached to the transducer, the needle could be directed to the mass or fluid through a predetermined pathway that was displayed on the screen. This allowed the ability to biopsy deep masses, such as retroperitoneal lymph nodes.

Sonographer involvement is not universal and, in some departments, sonographers are excluded from being involved in any aspect of the procedure. It is not uncommon for the radiologist to become a sonographer as they hold the transducer for other physicians, such as obstetricians, nephrologists, and even other radiologists. Those that support sonographer involvement wonder why a radiologist would use their valuable time to assist other physicians, as the radiologist could continue to dictate reports and check studies.

Using Ultrasound
Recently, there has been a growing movement among radiologists who have discovered the advantages of using ultrasound over CT. Their hope is to educate their colleagues of the benefits of ultrasound-guided procedures over CT guidance. Reimbursement issues have been a driving force behind the move to do more procedures under ultrasound rather then CT. The time it takes to perform a procedure under ultrasound or CT guidance is approximately the same length of time, from 45 to 60 minutes. A routine ultrasound averages 30 to 45 minutes, thus the time is approximately the same or a little longer to perform an ultrasound-guided procedure. However, with modern 64-slice CT scanners, a typical CT scan averages 5 to 10 minutes. Therefore, in the same amount of time it takes to perform a biopsy with CT, an additional 6 to 8 patients could have been scanned. The revenue generated by ultrasound when used as the guiding modality is more than that generated by a routine ultrasound study, whereas the revenue generated with routine CT scans in the amount of time it takes to perform the CT-guided procedure is much greater.⁴

Biopsies
There are 2 methods to remove cells from a mass or organ. Fine-needle aspiration (FNA) is used to obtain cells from the mass. FNAs are performed using a 20- to 27-gauge needle, preferably with a cutting tip, such as a Franseen needle. These types of needles have the least risk associated with their use, allowing multiple sample collections as needed. The specimen is obtained by using a capillary action technique. This involves a fine up-and-down motion of the needle, which obtains the needed cells through a scraping or cutting action. An FNA technique reduces the trauma to the cells and decreases the amount of background blood in the specimen. If the sample is scant and there are not many cells, suction techniques can be used. Suction technique involves using a syringe and tubing attached to the needle. As the needle is being moved up and down, suction is applied to draw up the cells into the needle and syringe. Because of their thin size, the needle can go through bowel, other organs, and near vascular structures, with minimal, if any, complications. FNA in conjunction with onsite cytopathology can ensure that the procedure is diagnostic and help minimize the number of samples needed to make the diagnosis.⁵

A core biopsy utilizes an automated, spring-loaded device, termed a biopsy gun (Figure 1), to provide a core of tissue, as opposed to just cells, for analysis. Core biopsy needles are larger in diameter and range in size from 12 to 20 gauge. A core biopsy provides tissue for histologic analysis and can also be used in conjunction with FNA techniques, if a definitive diagnosis could not be determined from just the FNA or if the cytopathologist requires more tissue for a more accurate diagnosis. Cores biopsies are also used to diagnosis diffuse parenchymal disease of the liver, kidney, and in transplanted organs, in addition to on breast and prostate biopsies.

Figure 1. Biopsy Gun

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

A common indication to perform a biopsy is to confirm malignancy in a mass. The mass may be the primary tumor in a patient with an undiagnosed malignancy or a metastatic mass in a patient with a known primary malignancy. Other indications include the need to differentiate between a metastatic mass and a second primary, determine the primary of metastases in a patient with multiple primaries, differentiate recurrent tumor from postoperative or therapy scarring, differentiate malignancy from inflammatory or infectious disease, and characterize a benign mass. Another common reason is to obtain a sample of the parenchyma in an organ to determine the severity of a disease process. Some examples of patients that would benefit from this procedure include patients with hepatitis, human immunodeficiency virus, renal failure, and rejection in a transplanted organ.

Drain or Obtain Samples of Fluid
Ultrasound is routinely used to guide needle placement to drain or obtain samples from fluid collections. Because of its excellent ability to distinguish fluid collections from solid masses and evaluate complex fluid collections, ultrasound is the ideal choice to guide such procedures as paracentesis or ascites tap, thoracentesis or pleural effusion tap, abscess collection, and amniocentesis. This is especially true with very small collections, complicated or loculated collections. If just a small sample of fluid is needed a 22- or 20-gauge needle is used. If the fluid is viscous, an 18- or 16-gauge needle may be required. If the goal is to drain as much fluid as possible, a special needle, called a centesis needle, is used. After the needle is properly placed, it is removed leaving a catheter with side holes to safely drain the fluid (Figure 2). For large volume drainage, 1-liter vacuum bottles are used to remove the fluid. Ultrasound can be used periodically to check the amount of fluid remaining, or help reposition the catheter to free it from bowel that may be sucked against the wall of the catheter. Usually, the sonographer can offer additional guidance by scanning outside the sterile field periodically to evaluate the amount of fluid remaining and the position of the catheter. Small fluid pockets or multilocular collection samples are best obtained using a needle guide. Abscess or fluid collections may be located in or around the liver, peri-pancreatic, peri-nephric, intra-abdominal, or in the pelvis. Ultrasound can be used to provide guidance to drain the gallbladder in patients who have cholecystitis, especially acalculus cholecystitis, or in patients who are too sick for whom surgery would be contraindicated. For pelvic collections, depending on their location, an endovaginal approach should be considered in women, and endorectal approaches in both men and women. Catheters may be left in place to drain the collection. Patients may have follow-up imaging studies to monitor that the cavity is getting smaller and to check that the catheter is still in the correct position. These follow-up examinations are usually performed under fluoroscopy in a procedure called a sinogram, although ultrasound or CT may also be used.

Figure 2. Catheter with Side Holes to Safely Drain the Fluid

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

Placement of Catheters
Ultrasound is also being used to guide physicians and radiologists with the placement of shunts, lines, and catheters in such procedures as transjugular intrahepatic porto-systemic shunt placement, and in nephrostomy tube placement in obstructed kidneys. Ultrasound can also guide fetal procedures, such as chorionic villi sampling and periumbilical blood sample. Recently, ultrasound has been used to help with the placement or guidance of lines and catheters in such vessels as the subclavian vein, subclavian artery, femoral vein, and even to start an intravenous line and peripheral-inserted central catheter line.

Contraindications
Contraindications for ultrasound-guided procedures are few. This can be attributed to its minimally invasive nature. Complications may include an uncorrectable bleeding disorder of the patient, the lack of a safe needle path, and an uncooperative patient. Patient cooperation is needed so that the mass may be biopsied safely. If the patient cannot hold still, is jumpy, or cannot control their breathing, the risk of a complication increases significantly, not to mention the added danger to the sonographer or radiologist of an accidental needle stick.

Laboratory tests are typically not requested before a procedure with the exception of bleeding times. Usually, an abnormal laboratory test will be part of the work-up before a biopsy is requested. Some examples of abnormal laboratory values include an elevated AFP (alpha-feto protein) with a liver lesion, an elevated prostate-specific antigen to evaluate for prostate cancer, changes in thyroglobulin levels in patients with a history of thyroid cancer, and increased white blood cells to determine if a lesion is an abscess or hematuria with a renal mass.

Bleeding times should be checked prior to most biopsies or procedures. These tests measure the time it takes the blood to form a clot. This is especially true in patients who are on "blood thinners," such as warfarin sodium, heparin, or aspirin therapy. Because vitamin K is essential in the blood clotting process, patients with liver disease are also at risk for prolonged bleeding or the formation of hematomas. To eliminate patient rescheduling or cancellation, test results should be obtained as close to the date of the procedure as possible, although results may be acceptable up to 3 to 4 weeks before the scheduled procedure. These simple blood tests can be performed the morning of the procedure, as results can usually be obtained in 2 to 3 hours.

There are at least a dozen factors that are needed for a patient to form a blood clot to stop bleeding. Through a complex series of reactions called the coagulation cascade, a clot is formed by the body. There are 3 pathways in the blood clotting process: intrinsic, extrinsic, and common. In order to evaluate all 3 pathways, both prothrombin time (PT) and partial thromboplastin time (PTT) are evaluated. PTT can be used to evaluate the effects of heparin, aspirin, and anticoagulants on the blood clotting process. PTT evaluates factors found in the intrinsic and common pathways. PTT values may vary depending on the method and activators used, with normal values typically between 60 to 70 seconds. PT is used to evaluate factors found in the extrinsic pathway, which may be effected by patients on warfarin sodium. Normal values are typically between 10 to 13 seconds. Because of the variability of PT results between laboratories, a method of standardization was developed called international normalized ratio (INR). The INR was created in 1983 by the World Health Organization to account for the various thromboplastin reagents used to determine PT, which caused fluctuations in normal values. The INR is a calculation that adjusts for the variations in PT processing and values, thus test results from different laboratories can be compared. The INR is expressed as a number. Values of less than 1.4 are needed to ensure a safe procedure. The INR/PT is not used on patients with liver disease or on heparin. It is evaluated on patients taking anticoagulants, especially warfarin sodium. Some departments may not require a hemostatic evaluation for low-risk biopsies or procedures, such as fluid aspirations, and superficial biopsies, such as of the thyroid or prostate gland. Anticoagulants should be discontinued prior to the biopsy to reduce the risk of post procedural bleeding. It is recommended that heparin be stopped 4 to 6 hours prior to a biopsy, 3 to 4 days for warfarin sodium, and 5 to 7 days for aspirin. A patient with a coagulopathy problem may need to have a platelet transfusion prior to and during the biopsy.

Specialties of a Sonographer
As stated earlier in this article, sonographer involvement varies in duties from department to department. Although the obvious benefit appears to be the freeing of the radiologists time, there are actually more important reasons to have the sonographer involved. However, before these benefits are discussed, let's review the requirements and skills a sonographer should have to be a member of the biopsy team.

In today's sonography environment, sonographers are becoming more and more specialized. Part of this is due to the complexity of today's examinations. Some sonographers have developed their skills and decided to work almost exclusively in one aspect of ultrasound, such as obstetrical, echocardiography, abdominal, or vascular. A sonographer who wants to assist in biopsies may need to develop and fine tune some different skills. Besides excellent scanning abilities, they will also need good communication skills and the ability to handle biopsy failures and complications. Not every biopsy is successful and the sonographer must psychologically accept this fact and not assume guilt if the procedure did not go as planned or that the patient developed a complication. Not every sonographer is suited to assist with procedures, usually because they have a hard time dealing with the complication aspect of biopsies. Those sonographers that prefer not to be involved in procedures or biopsies should have that request considered by their radiologists and chief sonographers/managers to help reduce the employee's stress levels.

Role of the Sonographer in Procedures
A sonographer that wants to be involved in procedures needs to have the drive or interest in gaining experience. This is a different type of scanning, as the routine, protocol scan has already been performed or the patient has had another imaging study, such as a magnetic resonance image (MRI) or CT. In procedures, usually all that is required is a focused scan of the area of interest to determine if the lesion can be seen with ultrasound and if a safe needle path can be determined. Another requirement is patience, as there can be a lot of waiting or down time, something most sonographers are not accustomed to having. The patient must be consented, vital signs taken, and sometimes the patient is premedicated before the procedure. The sonographer must wait until it is their turn to scan and they typically do not have enough time to scan another patient while they are waiting. They can assist their fellow sonographers in other ways, such as helping out with paperwork. Once the patient is ready to be scanned, the sonographer will be busy with scanning and prepping the transducer and assisting in cleaning up the patient, transducer, and room. Sonographers that are involved with biopsies typically do not perform the average daily number of examinations per sonographer, as their examinations are typically longer in duration.

Another trait that needs to be developed is perseverance, as the sonographer must go that extra mile to find the lesions or masses. It is important to have any CT or MRI studies in the room to assist in finding the mass in question. As some liver masses may be very subtle on ultrasound, it is helpful to use the CT or MRI image to find landmarks to locate these masses. Using these landmarks, it is sometimes possible to biopsy the area of concern without seeing the actual mass.

Not every biopsy is best performed with the patient in a supine position. Sometimes the best or safest approach may be to have the patient in an oblique, decubitus, or even in a prone position. It is often necessary to try different patient positions in determining the best and safest approach. Things that need to be considered include organs that will be traversed by the needle and the location of any arteries and veins. For example, when a biopsy is performed on a mass in the head of the pancreas, the needle may pass through the liver and stomach to reach the mass, but the portal vein, splenic vein, or splenic artery should not be in the needle path.

The sonographer must be a true team player and be willing to "change hats" as needed. They will need to be a part time "nurse" to assist in opening trays and sterile supplies, helping the radiologist draw up the local anesthetic, and finally to help clean the betadine and blood off of the patient after the procedure. The sonographer may be the best person for putting the band-aid or dressing on as sometimes there is no bleeding and it may be difficult for the nurse to see where the needle entered the skin. It also allows the opportunity for the sonographer to have closure with the patient. At other times during the procedure the sonographer will need to be a coach and work with the patient to get them through the procedure. This can be as simple as helping them in holding their breath to encouraging them through their fears and any pain or discomfort that they may be feeling. The sonographer can also literally lend a hand to the patient, by allowing an anxious patient to hold or squeeze their hand, or they can give a reassuring pat to their arm. These personal touches can help alleviate the anxiety of the patient. The sonographer can show them that they really care about the person and do not think of the patient as just the 1 o'clock liver biopsy. Remember, most patients are there to determine if they have cancer or metastatic disease.

Besides excellent technical skills, the sonographer will need excellent communication skills. During the planning stage, the sonographer should explain the need for why the patient needs to suspend respiration and work with them on breathing techniques. As not every biopsy will require the patient to take in a deep breath, it is important for the sonographer to explain how they want the patient to hold their breath, as it might be on inspiration, expiration, or somewhere in between. The sonographer can then practice with the patient on breathing for the procedure. Sometimes it is advantageous to show the patient the mass and how to control their breathing; this technique will allow the mass to fall on the needle guide path. This will also allow the sonographer to evaluate how long the patient can hold their breath. This information can then be passed onto the radiologist, especially if the patient cannot hold their breath very long. The sonographer will have to be able to discuss clearly with the radiologist the various options of the needle path to help determine the safest and best approach. Because they performed the scan, they will discuss with the radiologist blood vessels in the area, in addition to other organs that are in the path of the needle. Most importantly, sonographers must not be afraid to communicate to the physician during the procedure when the needle is deviating toward a vessel or other organ, to alert them if the needle pass is too deep, and remind them that the patient needs to breathe. This is best done professionally and calmly, not to upset the patient or the radiologist.

Because the physician is typically involved with the specimen and talking about the quality of the pass to the cytopathologist, if they are present, and the nurse may be busy documenting the procedure, patient's vital signs, and pain levels, the sonographer is the most available person of the team to talk to the patient. They can determine how well the patient is tolerating the procedure, explain what the next step might be, and either answer their questions or get the radiologist's attention. Because typically multiple biopsy samples are required to obtain an adequate specimen, the sonographer can explain to the patient that this is normal, as many patients think that additional biopsies are needed to get more and more cancer cells. Often times, the sonographer can become the center of communication for the patient.

Importantly, a sonographer can be a second set of hands as needed. They can adjust imaging controls, freeze and unfreeze the image, and document the needle tip. Another need for a second set of hands is keeping the transducer in place while the patient is anesthetized. The patient receives a local subcutaneous numbing followed by deeper numbing of the needle track to the top of the lesion or the capsule of the organ. After numbing the area, the sonographer keeps the transducer on the anesthetized spot. This can be very important for sensitive regions of the body, such as the liver capsule, to ensure that the needle does pass through the anesthetized area and not through another area causing the patient unneeded pain. The sonographer could also inform the patient that they should not feel any sharp pain but that they will feel the pressure of the needle and not to be alarmed by this sensation or to move. A good analogy is the sensation of having a tooth filled but not feeling the pain. When using biopsy guides, the sonographer can hold the transducer, freeing the physician's hands. This can be especially helpful when aspiration techniques are used. The sonographer can use the transducer to press bowel out of the way, allowing the mass to be seen. This increased pressure on the patient's skin needs to be maintained during the procedure, thus necessitating another set of hands. This technique can also be used to minimize the distance between the skin and the mass on deep lesions (Figures 3 and 4).

Figure 3. Minimizing the Distance Between the Skin and the Mass on Deep Lesions

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

Figure 4. Minimizing the Distance Between the Skin and the Mass on Deep Lesions

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

Ultrasound-Guided Biopsies
There are currently 2 ways to perform ultrasound-guided biopsies. One method is called the free-hand technique and is performed without the use of a needle guide attached to the transducer. The person that performs the biopsy may or may not hold the transducer. The transducer is placed in a sterile cover if scanning will be inside the sterile field. Scanning may also be performed outside the sterile area, in which a case cover is not required but is recommended, as betadine may drip on the transducer staining it or blood may contaminate the transducer requiring it to be soaked for 24 hours. Care must be taken to align the needle with the transducer and the sound beam. A variation of this technique allows the sonographer to scan outside the sterile field while the physician performs the biopsy. Again, in order to see the needle tip, the transducer must be aligned to the needle path. If the needle becomes lost on the image, the transducer should be repositioned in alignment with the needle to see the needle tip. The free-hand technique allows more flexibility in choosing the needle path; however, it is more technically challenging, especially on deep lesions (Figure 5).

Figure 5. Free-Hand Technique

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

The second method involves using a needle guide that is attached to the transducer (Figure 6). The predicted needle path is displayed on the screen and the mass is lined up along the path (Figure 7). Some needle guides offer a choice of different angles, usually a steep angle and a shallower angle, to access the mass. This gives some flexibility around vessels or other structures. Benefits of using a needle guide include that it has a faster learning curve, allows faster placement of the needle, and keeps the needle going through the anesthetized area when multiple biopsy samples are required (Figure 8). The use of needle guides has been shown to be invaluable when taking a biopsy of deep or small masses. Needle guides are not perfect and deviation from the needle path can occur. Bending of the needle may occur as it passes through dense tissue, such as a muscle or the stomach walls. The radiologist bending the needle as they are inserting it can cause the needle not to travel in a straight line. This will cause the needle to deviate from its intended path.

Figure 6. Needle Guide Attached to the Transducer

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

Figure 7. Predicted Needle Path on the Screen

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

Figure 8. Needle Guide

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

Complications from an ultrasound-guided biopsy are usually minor and may include postprocedural pain or discomfort, vasovagal reactions, and hematomas. Serious complications, although rare, include severe internal bleeding, hemorrhage, pneumothorax, pancreatitis, biliary leakage, peritonitis, infection, and possibly death. Seeding of the needle track by malignant cells is very rare, with an estimated occurrence of less than 0.01%.⁶

The technical improvements in grey scale imaging have enhanced our abilities to see more subtle masses and lesions. New technologies, such as harmonic and compound imaging, have allowed visualization of masses not seen previously with ultrasound. A major benefit that the sonographer can bring to the biopsy team is their understanding of these new technologies and how and when to use them. The sonographer can evaluate the patient with these technologies to optimize the pathology. The following examples demonstrate where harmonic imaging or compound imaging improved visualization of the mass or lesion.

Using their Doppler skills, the sonographer can locate vessels that may potentially traverse the needle path or be in close proximity to the mass. They can help guide the needle safely to deep retroperitoneal masses that may be near major vessels, such as the inferior vena cava or aorta. Also, by using color or power Doppler, the sonographer can locate vessels in a mass, as this may represent areas of viable tumor tissue. This can be very beneficial in masses that have necrotic areas and specimens obtained so far that have not been yielding diagnostic cells.

Finally, the sonographer can be a time saver to a busy radiologist. The sonographer can assist with probe preparation, in addition to cleaning up. They can be scanning the next patient while the physician attends to the next patient or checks and dictates other studies. With a sonographer involved, a second radiologist may not be required, thus allowing patient flow to continue in the department.

The needle tip should appear as an echogenic dot on the ultrasound image. Visualizing the needle tip depends on several factors, including the type of needle, as specially designed needles with echogenic tips are better seen by ultrasound than normal needles; the gauge of the needle, as larger gauge needles cause brighter reflections; the transducer frequency; the placement of the focal zone, which should be at or just below the level of the mass; and the echogenicity of the mass, as hypoechoic masses allow easier visualization of the needle than more echogenic masses. The needle should be inserted quickly and steadily and the tip followed as it advances toward the mass. The needle may deviate out of the projected path and away from the ultrasound beam causing the inability to see the needle tip. Again, this deviation of the needle can be caused by the physician bending or tilting the needle as it is being advanced or by the tissue and muscle planes it is traversing.

Methods to finding the needle tip include moving the needle or stylet up and down in a bobbing motion, angling the transducer in a superior and inferior motion, using harmonics or compound imaging, and as a last resort removing the needle and starting again, closely watching the displacement of the tissue as the needle advances.

Deviation of the needle from the projected path can be an issue. The tissue between the skin and the mass are usually the cause of this problem. If it is a constant problem, the sonographer can over correct (ie, move the transducer more lateral or medial, thus the path that the needle is following will intersect the mass). It is important that the sonographer verifies that the correct size of needle guide was used; if the guide is too big, there is some play within the needle guide that can cause this problem. If the problem persists, sometimes using a 20-gauge needle as opposed to a 22-gauge needle may correct the situation because the larger needle size is stiffer. In extreme cases, another pathway may need to be determined.

Another problem is when the mass is small and is pushed out of the way by the needle. This can be a problem with small nodes. Again, the sonographer needs to know how to counter these situations. Applying firm pressure with the transducer against the mass or trying to get the needle to approach the center of the mass, so that it doesn't push the mass left or right, can stabilize the mass allowing the needle to enter the mass. Sometimes, another approach may be needed requiring breaking down the sterile field and starting again. When these situations arise, the sonographer should be thinking of possible solutions to suggest.

The sonographer should be in charge of the transducer and setting it up for the biopsy. This includes obtaining the appropriate kit for the transducer being used, getting the correct needle guide, and properly attaching it to the transducer, inserting the correct needle gauge into the needle guide, and applying the protective sheath or transducer cover to the transducer using proper sterile techniques. Some transducers place the guide directly on the transducer and the sterile sheath covers both (Figure 9), whereas others place the needle guide over the sterile sheath. The sonographer should also be responsible for cleanup of the transducer after the procedure or biopsy is finished. This requires removing the needle guide and the sterile sheath, wiping the gel off the transducer, and taking the transducer and the needle guide to be soaked in a sterilizing or cleansing solution. Having the sonographer responsible for cleaning up can greatly decrease the chance of a needle guide being accidentally thrown away. And, at an average cost of $1500, this can become costly, in addition to cause delays while a new guide is ordered and shipped.

Figure 9. Guide Directly on the Transducer and Sterile Bag Covering Both

Image courtesy of M. Robert DeJong, Jr, RDMS, RDCS, RVT.

The National Patient Safety Standards mandate that a "time-out" be performed before beginning any procedure. A member of the biopsy team should ask the patient to recite their full name. The patient's ID or patient number is confirmed and the type and location of the procedure. This is documented at the bottom of the consent form. The words "time-out" may also be typed on the screen and an image documented to be part of the ultrasound examination. This is helpful, as there will be a preprocedural image, the "time-out" image, which documents date and time, and then the needle tip documentation images.

Liver biopsies are one of the most commonly performed biopsies, either for specific areas or for diffuse parenchymal abnormalities. Liver masses are amenable to ultrasound-guided biopsy in the majority of patients. These masses include metastatic masses, suspected hepato-cellular carcinoma (HCC), especially in patients with elevated AFP, or atypical benign lesions, such as adenomas, focal nodular hyperplasia, and hemangiomas. A hypoechoic area in a cirrhotic liver should be biopsied, as the patient is at increased risk for HCC, although the area may be a regenerating liver nodule. The inability to biopsy a liver mass can be caused by the failure to visualize the mass or when a safe approach to the mass cannot be determined. Masses at the dome of the liver are easier to biopsy with ultrasound than CT, although a steep angle approach is often required. Core biopsies are obtained on patients with hepatitis, cirrhosis, or increased liver function tests to determine the extent of damage to the liver. The left lobe of the liver is biopsied using a subcostal approach. This is easier to perform and more comfortable for the patient than the traditional blind approach through the ribs of the right lobe, as intercostal spaces are very sensitive. Specific complications of liver biopsies include the possibility of a pneumothorax, bile leak, and hematomas.⁷

Most pancreatic biopsies are performed to confirm the diagnosis of adenocarcinoma, unresectable adenocarcinoma, or confirm pancreatitis in patients with unusual imaging studies. The needle has to traverse the stomach or colon, but complications are rare. Color Doppler is useful to map out vessels, especially if there is encasement of the mesenteric vessels by the mass. Good specimens on patients with drainage tubes can usually be obtained near the biliary drainage tube. Pancreatic biopsies can be very challenging as gas can move into the field obstructing visualization of the mass, even after the biopsy has started. Other challenges include finding a safe path around the various vessels, deflection or bending of the needle as it goes through the stomach, and patient breathing, which can cause the pancreas to move with respirations. Specific complications of pancreatic biopsies include pancreatitis.

Most solid renal tumors are surgically resected without obtaining a biopsy. However, a biopsy of a renal mass may be requested to differentiate an incidental renal cell carcinoma from a renal metastasis in a patient with a known primary cancer or if the patient has a prior history of renal cell carcinoma. Atypical cysts, especially those with thick septations, need to be biopsied to differentiate between a cystic renal cell carcinoma and a benign, atypical, renal cyst. Core biopsies of the kidney are needed in patients to determine the cause of renal failure or proteinuria. These are usually performed on the lower pole of the left kidney with the patient in a prone position. Because the disease process is a bilateral process, it does not matter which kidney is biopsied. After the biopsy, color Doppler is used to determine if there is any sign of a hematoma or active bleed. If an active bleed is seen, the sonographer can apply pressure over the bleed and apply pressure until the bleed stops. This pressure is held for 10 to 20 minutes. If this does not stop the bleeding, then the patient may need to be sent to interventional radiology, as the patient may become hypotensive or even bleed to death.⁸

Most retroperitoneal masses, including para-aortic and paracaval lymph nodes, are amenable to ultrasound guidance. These can be very technically challenging, especially with small masses and in larger patients; therefore, the use of a needle guide is essential. Usually an anterior approach is preferred and, by applying a firm and steady pressure with the curved linear array transducer, overlying bowel loops and intra-abdominal fat can be displaced. This technique also reduces the depth at which the needle needs to be placed. Vascular structures are identified with color Doppler. Real-time monitoring of the needle tip ensures that the needle excursions during the biopsy stay within the node. In patients with suspected lymphoma, tissue needs to be obtained not only to diagnose lymphoma but also to determine the subtype because this is critical for treatment. Usually part of the sample is sent for flow cytometric studies. Specific complications include retroperitoneal hematomas.⁶

Ultrasound guidance has been shown to be a safe alternative to CT for pleural-based, parenchymal or mediastinal masses that abut the chest wall. This technique is associated with a high success rate and lower complications than CT and is particularly valuable for small peripheral masses in close proximity to a rib and diaphragmatic masses where slight respiratory excursion can affect the position of the mass. The transducer is placed parallel to the intercostal space and the needle is advanced in a single breath hold, minimizing trauma to the pleura. The tip is monitored to ensure it does not slip out of the mass and into normal aerated lung. Intraparenchymal tumors are generally not amenable to ultrasound guidance because the ultrasound beam cannot penetrate through air. Lung lesions can be very challenging by ultrasound and it is always helpful to have the CT films present for guidance. These lesions are usually small and mobile with respiration. Creative positioning may be needed to get between ribs and around the scapula. The patient may need to be placed in an oblique, decubitus or prone position. A pillow or sponges may be placed under the patient to spread the ribs apart. The patient's arm may also need to be adjusted to get the scapula out of the way in apical lesions. A small foot print phased array transducer is helpful to get between the ribs and allow the sonographer to angle through the rib space. Specific complications include pneumothorax.⁹

Thyroid biopsies can be helpful in determining malignant masses from goiters or adenomas. Also, new masses may be assessed for reoccurrence in patients with known thyroid cancers. Biopsies should be taken in various portions of the mass to confirm colloid or abnormal cells and should be obtained in areas where small calcifications are noted, as there is a higher percentage of positive cells in these areas. Specific complications include neck pain and hematomas.⁶

Biopsies of neck masses can easily be performed with ultrasound guidance. In a patient with a history of thyroid cancer, it is important to differentiate between malignant and infectious nodes. Round, homogenous nodes are usually suspicious for cancer as opposed to more oval nodes with echogenic centers from a fatty hilum. Other causes of neck masses include lymphoma and submandibular gland tumors.

Conclusions
Ultrasound is unique as a guidance modality because it combines excellent imaging with real-time visualization. It is a true team with the radiologist, sonographer, nurse, and cytopathologist all working together for the good of the patient. The future is especially exciting as companies work on fusing ultrasound and CT or MRI images on the ultrasound unit. This will allow the sonographer and radiologist to see the CT or MRI of the patient with the active ultrasound image superimposed over the CT or MRI image or side by side on 2 monitors. As the sonographer scans, the CT or MRI image will change accordingly. New biopsy transducers are available with the biopsy guide through the middle of the transducer, allowing the needle to go straight as opposed to at an angle. The use of 3D and real-time 3D, called 4D imaging, are being explored. This allows the exact location of the needle in the mass to be determined. It can be difficult on the 2D ultrasound to determine if the needle is in the middle of the mass or along the periphery. Devices are available that attach to the needle and allow electronic tracking of the needle for accurate following and placement of the needle.

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