Interventional Radiology: The Basics
What is Interventional Radiology?
Interventional Radiology (IR) is one of the most technologically advanced and fastest growing specialties of modern medicine. As a subspecialty of radiology, IR utilizes image-guidance via ultrasound, x-ray, CT, MRI, and fluoroscopy to perform advanced minimally-invasive procedures in an operating room type setting. Many procedures that once required surgery can be performed by an Interventional Radiologist without general anesthesia or incisions, thus enabling patients to go home the very same day. As the inventors of angioplasty and the catheter-delivered stent used in the heart and other blood vessels, interventional radiologists pioneered modern minimally-invasive medicine and continue to use their advanced technology to treat an increasing number of disease processes including cancer, uterine fibroids, deep vein thrombosis and varicose veins, aneurysms, and many other conditions.
Who is an Interventional Radiologist?
An Interventional Radiologist (IR) is a physician who is Board Certified in Radiology and has pursued further fellowship training to perform minimally-invasive image-guided procedures. After 4 years of college, an IR completes 4 years of medical school followed by 5 years of residency training and then 1 year of fellowship training for a total of 10 years of training after college. This specialized training is certified by the American Board of Medical Specialties.
Who are the other members of the IR team?
During your procedure, the Interventional Radiologist will be assisted by a radiology technologist and a nurse. The technologists assist the IR during the procedure, just as a surgical technician assists a surgeon. A registered nurse will also be present to monitor your vital signs and provide medications for sedation and pain control.
In addition, the IR team may include a Physician Assistant and/or Nurse Practitioner who will guide you step by step through your procedure and let you know what to expect after the procedure. The PA or NP may serve as a contact person regarding ongoing follow-up and plan of care during your entire cancer treatment program.
What types of cancer can benefit from IR?
For years, the mainstay of cancer treatment has involved chemotherapy, surgery, and/or radiation. With the advanced technology provided by IR, cancers that once required surgical removal or traditional chemotherapy can be treated percutaneously through a small puncture in the skin the size of an IV needle.
Almost all oncology patients will cross paths with an Interventional Radiologist at some point during their treatment regimen. Depending on the type of cancer, an Interventional Radiologist may become one of your primary physicians or serve as a consultant to your oncologist or surgeon.
How is IR used in cancer treatment?
Interventional Radiology boasts a wide range of procedures from placement of tunneled catheters and ports for chemotherapy to extremely advanced procedures including transarterial chemoembolization (TACE), radioembolization, radiofrequency and cryoablation.
Transarterial Chemoembolization (TACE):
TACE is used to treat liver tumors, both primary hepatocellular carcinoma and secondary, or metastatic liver lesions. The procedure involves placement of a small catheter into the blood vessel of the groin, which is then threaded through the blood vessels into the liver using video fluoroscopy (real-time x-ray). Contrast dye is injected through the catheter to define the anatomy and location of the tumor. Once the blood vessels are mapped properly, a mixture of concentrated chemotherapy is injected through the catheter and directly into the blood vessels that feed the tumor. To help concentrate the chemotherapy, microspheres (or basically grains of sand) are injected into the same vessels that feed the tumor to block any further blood flow to tumor. This serves to not only trap the chemotherapy mixture in the tumor but also to deprive the tumor of oxygen and nutrients it needs to grow, thus hopefully both treating and killing the tumor. Afterwards, a patient will have to lay flat for 4-6 hours and is typically admitted overnight to the hospital for monitoring for about 24-36 hours.
Radioembolization (SIRspheres or THERAspheres):
Transarterial radioembolization is used to treat liver tumors, both primary hepatocellular carcinoma and secondary, or metastatic liver lesions. The procedure is very similar to TACE except that "radioactive beads" are injected through the catheter and directly into the blood vessels that feed the tumor instead of chemotherapy. To help prevent reflux of the radioactive beads to any other areas of the body bland microspheres, or basically grains of sand, are then injected after the radioactive beads to block any further blood flow to the vessels that feed the tumor, thus hopefully both treating and killing the tumor. Radioembolization differs from TACE not only by the actual agent that is being injected (radiation vs. chemotherapy) but also by the fact that radioembolization requires a separate planning procedure prior to the actual treatment. This is done to determine the dose of beads that will be needed and to ensure that the radiation will be safe. This planning procedure is very similar to the treatment procedure and involves a very minute amount of radiotracer injected through a catheter followed by imaging performed in the Nuclear Medicine department. Unlike TACE which requires an overnight hospital stay, a patient having either the mapping study or the actual radioembolization is typically monitored for about 2-4 hours for the mapping and 4-6 hours for the actual embolization and then discharged to home the same day.
These procedures can be further divided into cryoablation "cold" and microwave or radiofrequency ablations "hot." There is also alcohol ablation therapy. These procedures are done percutaneously, or through the skin, with the support of either ultrasound or CT scan imaging. The imaging is used to target the tumor and a probe (long needle-type instrument) is then inserted into the tumor and the ablation. With the cryoablation, ice crystals form inside the tumor which causes death of the tumor cells as it defrosts. With both microwave and radiofrequency ablation, the heat that is generated kills the tumor. Finally, in an alcohol ablation the alcohol acts as a toxin and kills the tumor cells. Some of the most common tumors that are ablated include small renal cell carcinomas, small liver tumors (both primary and metastatic), metastatic bone lesions that are causing pain, isolated lymph nodes that causing symptoms such as pain or swelling, and small peripheral lung lesions.
Central Venous Access Devices:
Port-a-catheters, Hickman catheters, Pheresis catheters and peripherally inserted central catheters (PICC) lines are some of the most commonly placed "central lines" by IR. These devices are placed using ultrasound and fluoroscopic guidance to gain access to the vasculature, or blood vessels. Once they are placed they can be used for drawing labs, delivering chemotherapy and biotherapy, collecting stem cells or simply infusing intravenous fluids and blood products. Depending on the device, they can also be used during imaging, such as CT scan and MRI. Another common reason for having these devices placed is to preserve peripheral veins, or after a point when the patient has received multiple rounds of treatment through peripheral IVs and the feasibility of placing further IVs becomes increasingly challenging.
Nutrition Supplementation Tubes:
IR can place feeding tubes, Gastrostomy tubes which drop into the stomach, Jejunostomy tubes which drop below the stomach sphincters, and/or G-J combination tubes. These tubes can be used for supplemental nutrition in patients with swallowing difficulty after head and neck surgery, or due to mucositis and esophagitis from radiation, or simply in oncology patients that have difficulty maintaining their nutrition during therapy. These tubes can also be used palliatively to help with decompression or removal of pressure due to blockage of the stomach.
IVC Filter Placement and Removal:
An inferior vena naval filter (IVC filter) is a small device that functions like a catcher's mitt to capture blood clots but allow normal liquid blood to pass. Generally, patients who develop blood clots are placed on blood thinning medications called anticoagulants to prevent new clots from forming and existing clots from worsening. In some cases, patients may not be able to tolerate these medications due to the risk of bleeding or other contraindication and thus an IVC filter must be placed. The filter is placed through a vein in the groin or the neck and is used to capture any clot that may attempt to travel from the lower extremities to the lung and/or heart that can be fatal. Because cancer makes an individual more likely to develop blood clots, these filters are routinely used in cancer care. Placement and removal of an IVC filter is a same day procedure that does not require an overnight hospitalization.
DVT Thrombolysis and Thrombolectomy:
Deep vein thrombosis (DVT) is the development of a blood clot in a deep vein, predominantly in the legs. Symptoms include swelling, pain, warmth, redness, and engorged superficial veins. Pulmonary embolism, a potentially life-threatening complication, is caused by the detachment (embolization) of a DVT that travels to the lungs. Together, DVT and pulmonary embolism constitute a single disease process known as venous thromboembolism. Post-thrombotic syndrome is a long-term and potentially debilitating complication of DVT that leads to chronic lower extremity swelling, venous stasis ulcers, lymphedema, and painful varicose veins. Cancer patients are at a much higher risk of developing DVT and subsequent post-thrombotic syndrome if not managed properly.
DVT thrombolysis is a procedure performed in a hospital's Interventional Radiology suite and is designed to rapidly break up the clot, restore blood flow within the vein, and potentially preserve valve function to minimize the risk of post-thrombotic syndrome. The interventional radiologist inserts a catheter into the popliteal (located behind the knee) or other leg vein and threads it into the vein containing the clot using imaging guidance. The catheter tip is placed into the clot and a "clot busting" drug is infused directly to the thrombus (clot). The fresher the clot, the faster it dissolves - one to two days. Any narrowing in the vein that might lead to future clot formation can be identified by venography (an imaging study of the veins), and treated by the interventional radiologist with a balloon angioplasty or stent placement.
Tunneled Intra-Peritoneal Drains (IP drains) and Denver Shunt:
In patients with metastatic disease (spread from the original site) one of the symptoms that patients can develop is fluid retention, or ascites, in their abdomen. There are many different causes of this fluid, but it is often very challenging to treat with medicine alone. These patients often initially proceed with drainage of the fluid collection via a paracentesis, placing a needle into the pocket of fluid and then using an external catheter to remove the fluid. If this procedure is able to improve the symptoms, but the fluid again accumulates there are two procedures that can be used to help drain the fluid without repeated trips to the hospital, either a tunneled intra-peritoneal (IP) drain or a Denver Shunt. Both of these procedures require an office consultation prior to placement of the device to discuss the procedure and fill out needed paperwork for supplies needed for care of the drain.
An IP drain is a tube that is tunneled under the skin using ultrasound guidance with one end sitting in the fluid pocket and the other end on the outside of the body. The tube can be opened (drained) as needed by the patient, family member or a home visiting nurse. This procedure can be done with local numbing medicine only or with sedation. It is an outpatient procedure.
The Denver shunt is a tunneled catheter that is placed using a combination of ultrasound and fluoroscopy guidance under the skin, but the tube then tunnels from the pocket of fluid in the abdomen under the skin of the chest toward the neck. The catheter enters the vasculature near the clavicle (collar bone) and then is directed toward the super vena cava (large blood vessel in the chest). This procedure is always performed with sedation and the patient has no external drain. The catheter itself has a "pump chamber" or "bubble" along the tube that the patient or family member then pumps to help remove the fluid from the abdominal pocket and re-circulate it through the blood stream. This is an excellent option for those patients that would benefit from the extra fluid, or have been losing weight and muscle mass with repeated paracenteses. This procedure is always performed with an overnight hospital stay to monitor for pain and bleeding, as it is initially slightly more extensive of a procedure compared the IP drain, but once it is placed, there is less "maintenance" of the catheter as it has no external components.
Tunneled Pleural Catheters:
Pleural catheters, commonly referred to by their brand name, PleurX, are similar to a tunneled IP drain. However, instead of draining fluid from the abdomen, these catheters are used to drain fluid from the lung, commonly referred to as pleural effusions. These catheters are placed using either ultrasound or CT-guidance into the pocket of fluid and then tunneled through the skin to an exterior location to allow for intermittent drainage by the patient, family member or visiting nurse. After this procedure is completed, often a chest x-ray is obtained to check proper alignment and ensure that the remaining lung fields remain open and functional.
Interventional Pain Management Procedures:
Often with progressive abdominal cancers, such as ovarian or pancreatic cancers, as they grow they can cause compression (pushing) or irritation to some of the nerves in the abdomen. When this occurs it can lead to severe pain, such that even large doses of opioids, such as Dilaudid or Fentanyl, simply cannot control the pain adequately without leading to unwanted side effects of sedation and constipation. If this occurs, an Interventional radiologist or anesthesiology trained pain specialist may be able to "block" this pain signal with ablation of the nerve. Using fluoroscopy guidance the nerve is targeted and a long needle is inserted into the nerve where either alcohol is injected, or cryoablation (freezing) is performed to ablate the nerve.
IR can play many roles in the treatment of cancer or the management of certain side effects of cancer and it's treatment. Talk to your oncology team about how an interventional radiologist may play a role in your care team.
Geschwind, J. F. H., & Soulen, M. C. (2016). Interventional Oncology: Principles and Practice of Image-Guided Cancer Therapy. Cambridge University Press.