Interventional Radiology - Radiologist Education

Interventional radiology (IR), also known as vascular and interventional radiology (VIR) or surgical radiology, is a sub-specialty of radiology providing minimally invasive image-guided diagnosis and treatment of diseases in every organ system. Although the range of procedures performed by interventional radiologists is broad, the unifying concept behind these therapies is the use of the most modern, least invasive technique available in order to minimize risk to the patient and improve health outcomes.

As the inventors of angioplasty and the catheter-delivered stent, interventional radiologists pioneered modern minimally invasive medicine. Using X-rays, CT, ultrasound, MRI, and other imaging modalities, interventional radiologists obtain images which are then used to direct interventional instruments throughout the body. These procedures are usually performed using needles and narrow tubes called catheters, rather than by making large incisions into the body as in traditional surgery.

Many conditions that once required open surgery can now be treated non-surgically by interventional radiologists. By minimizing the physical trauma to the patient, non-surgical interventions can reduce infection rates and recovery time, as well as shorten hospital stays.

Training

Traditional

As in most medical specialties, training varies depending on varying rules and regulations from country to country. In the United States, interventional radiologists are physicians whose education and training traditionally includes completing a college degree, four years of medical school, a year of training in general medicine and/or surgery (internship), a four-year diagnostic radiology residency program, and then a one or two year fellowship in vascular & interventional radiology.

With the evolving need to train more clinically oriented interventionists, two alternative pathways to achieve certification in IR have been established through the leadership of the Society of Interventional Radiology (SIR): The DIRECT and Clinical pathways. For both pathways, the SIR states that the trainee must become proficient in management of inpatient and outpatient pre-procedure, post-procedure, and follow-up clinical care for all disease processes pertinent to the practice of VIR.

DIRECT

The DIRECT (Diagnostic and Interventional Radiology Enhanced Clinical Training) pathway allows for up to two years of clinical training prior entering the program. Therefore, residents may enter the new pathway from medical school or after two or more years of clinical training in other specialties such as internal medicine or vascular surgery. The core diagnostic training is 27 months in duration, with 21 total months of VIR training for a total of 48 months (four year) duration. The advantage of the DIRECT pathway is that upon successful completion of the program and 12 months of clinical practice, a clinician can achieve both a Diagnostic Radiology board certification and a subspecialty vascular IR certificate. The American Board of Radiology offers a complete list of programs that offer this pathway at: http://theabr.org/ic/ic_other/ic_direct.html.

Clinical

An integrated Clinical Pathway has been created to provide breadth and depth of clinical experience for trainees who desire a primary career focusing on VIR rather than diagnostic radiology. The 6-year program allows for 29 months of Diagnostic Radiology training, 19 months of clinical training (including a medicine or surgery intern year) and research, and 21 months of VIR fellowship training. The Clinical Pathway is offered by institutions such as UVA, Northwestern and Brigham and Women's Hospital. The Clinical Pathway allows for certification in VIR and for board certification in diagnostic radiology.

Dual Certificate

A newer Dual Certificate program has been approved for implementation, establishing a six-year curriculum similar to the Clinical Pathway, that provides training for Board Certification in both Diagnostic and Interventional Radiology.

Pediatric

A handful of programs currently offer interventional radiology fellowships that focus on training in the treatment of children.

Imaging Modalities

Common interventional imaging modalities include fluoroscopy, computed tomography (CT), ultrasound (US), and magnetic resonance imaging (MRI) as well as traditional (plain) radiography:

• Fluoroscopy and computed tomography use ionizing radiation. However, both methods have the advantages of being fast and geometrically accurate.
• Ultrasound is frequently used to guide needles during vascular access and drainage procedures. Ultrasound offers real-time feedback and is inexpensive. Ultrasound suffers from limited penetration and difficulty visualizing needles, catheters and guidewires.
• Magnetic resonance imaging provides superior tissue contrast, at the cost of being expensive and requiring specialized instruments that will not interact with the magnetic fields present in the imaging volume.

Disorders

Vascular

The field of endovascular surgery arose from interventional radiology techniques to treat disease that is endovascular (inside blood vessels) and has become an alternative to vascular surgery for some conditions such as abdominal aortic aneurysm and peripheral artery disease. Basic techniques involve the introduction of a catheter percutaneously into a large blood vessel by Seldinger technique. Typically the blood vessel chosen is the femoral artery or a vein found near the groin. Access to the femoral artery for example, is required for coronary, carotid, and cerebral angiographic procedures. The catheter is injected with a radio-opaque contrast dye that can be seen on fluoroscopy (live X-ray). As the contrast courses through the blood vessels, characteristic images are seen by experienced viewers and can assist in the diagnosis and treatment of diseases such as atherosclerosis, vascular trauma, or aneurysms.

Endovascular surgery is performed by radiologists, neurologists, neurosurgeons, cardiologists, cardiothoracic surgeons, and vascular surgeons.

Varicose veins

Pooling of blood in the veins from weak valves resulting in enlarged, swollen vessels causing pain and cosmetic complaints. Interventional endovenous laser treatment or sclerotherapy may be used to heat the vein from the inside, sealing it closed. Other healthy veins carry blood from the leg to reestablish normal flow.

Peripheral artery disease (PAD)

Most commonly a result of atherosclerosis, occlusion of normal blood flow in the upper and lower extremities may result in pain, skin ulcers, or gangrene. Stenting, angioplasty, and mechanical atherectomy are available interventional treatments. For example, carotid stenting is used for treatment of carotid artery stenosis

Deep vein thrombosis (DVT)

The formation of a thrombus, or blood clot, in the deep leg veins which may lead to swelling, discoloration, and pain. DVTs can result post-thrombotic syndrome and pulmonary embolism. Post-thrombotic syndrome is irreversible damage from a long-standing DVT in the affected leg veins and valves, leading to chronic pain, swelling, and severe skin ulcers. Pulmonary embolism is a life-threatening condition which occurs when a deep vein thrombus (DVT) breaks off and travels to the lungs, resulting in difficulty breathing. Catheter-directed thrombolysis, balloon angioplasty, or stenting may be performed in the affected vein to dissolve the clot and restore normal blood flow.

Pulmonary embolism

A potentially life-threatening occlusion of the arteries supplying the lungs with blood clots, manifesting in shortness of breath, fatigue, palpitations, and fainting. Catheter-directed thrombolysis may be performed for this condition, where a catheter is inserted into the leg, threaded up to the lung, and then used to infuse "clot-busting" drugs into the occlusion.

IVC filter placement

Patients who have a history of, or are at risk for, pulmonary embolism may receive temporary or permanent inferior vena cava (IVC) filters to prevent the migration of blood clots to the lungs, and consequently prevent recurrence of pulmonary embolism.

Abdominal aortic aneurysms (AAA)

A weakening and dilatation of the abdominal aorta wall that can result in abdominal or back pain, and potentially life-threatening bleeding if it ruptures. Interventional treatment of this condition via non-surgical means is endovascular aneurysm repair, using angiography and stenting to occlude the AAA and prevent its continued growth.

Thoracic aortic aneurysms (TAA) and Aortic dissection

Aneurysms, or dilatations, of the thoracic (chest cavity) aorta may be caused by atherosclerosis, syphilis, trauma, or multiple other conditions. Aortic dissections are tears in the thoracic aorta resulting from trauma or weakening of the aortic vessel walls from conditions such as hypertension, atherosclerosis, and congenital conditions such as Marfan syndrome. Interventional treatments for TAAs and aortic dissections utilize stent grafts, sometimes in combination with surgery, to prevent blood flow from enlarging the diseased area or rupturing the aorta.

Acute limb ischemia

The sudden disruption of blood flow to an arm or a leg due to arterial occlusion by a blood clot or other debris, potentially treated with catheter-directed thrombolysis or mechanical thrombectomy.

Acute mesenteric ischemia

A medical emergency resulting from interruption of the blood supply to the abdominal organs due to blockage of the mesenteric arteries or veins by thrombus, embolus, or aortic dissection. Treatment varies by etiology of the ischemia, but may include thrombolysis, stenting, or angioplasty.

Aneurysms of visceral arteries

Dilatation of visceral arteries supplying organs such as the spleen, liver, or gastrointestinal tract can result in pain and life-threatening bleeding. Stenting, embolization, liquid occlusion, and thrombin injection are the available interventional therapies for these disorders.

Arteriovenous malformations (AVMs)

Aberrations in normal vascular anatomy treatable by embolization which may cause pain, bleeding, heart problems, or cosmetic concerns.

Oncologic

Various interventional therapies exist to treat cancer. Tumor type, size, extent of disease, operator experience, and involvement of anatomical structures all factor into deciding which therapy is most appropriate. Some therapies, such as transarterial chemoembolization, block the blood supply to tumors. Other techniques--radiofrequency ablation (RFA), microwave ablation, cryoablation, Irreversible electroporation(IRE), and high-intensity focused ultrasound (HIFU)â€"directly damage the cancerous tissue. All of these treatments are delivered locally, minimizing damage to nearby tissue and avoiding the systemic side-effects of chemotherapy. Depending on cancer type, extent of disease, and patient characteristics, these therapies may be useful as adjuncts to surgical or medical therapies.

Liver cancer

In addition to liver resection and liver transplantation, cryoablation, radiofrequency ablation, microwave ablation, Irreversible electroporation, percutaneous ethanol injection, chemoembolization, and radioembolization each have roles in adjunct or definitive therapy for certain types of liver tumors, depending on cancer type and patient selection/stratification.

Lung cancer

In addition to surgery (lobectomy), minimally invasive treatment options, including high-dose radiation therapies and percutaneous thermal (radiofrequency ablation, microwave ablation, and cryoablation) have emerged as safe and effective therapies.

Kidney Cancer

Cryoablation, radiofrequency ablation, microwave ablation, and Irreversible electroporation have emerged as treatment options alongside surgical nephrectomy and radiation therapy. For certain types of tumors, embolization has also been described.

Bone Cancer

Interventional radiologists play a role in the management of primary and secondary bone tumors with the aid of image-guided techniques, vertebroplasty, ethanol injection, radiofrequency ablation, laser photocoagulation, cryoablation, radiofrequency ionization (coblation), and HIFU. Thermal ablative therapies are also useful in the treatment of metastatic disease to the bones, and can offer patients pain relief and tumor control. Additionally, bland embolization has been used to minimize blood loss in patients undergoing surgical resection of bone tumors.

Breast Cancer

Interventional Radiologists utilize various minimally invasive ablative therapy techniques for the treatment of breast cancer, including: radiofrequency ablation, cryotherapy, interstitial laser therapy, high-intensity focused ultrasonography, and focused microwave thermotherapy.

Minimally invasive thermal ablation and embolization has also been used to treat liver and bone metastases from breast cancer.

Prostate Cancer

The appropriate management of prostate cancer is controversial. Common practice involves treating the whole gland in order to fully eliminate the typically multifocal disease. However, this form of treatment (i.e. radical prostatectomy and radiotherapy) is associated with significant negative outcomes including urinary incontinence and impotence. Interventional oncology offers alternative, tissue-preserving focal therapies that might minimize adverse treatment outcomes since they are less invasive and minimally traumatic. These therapies include cryoablation, HIFU, laser-based phototherapy, brachytherapy, radiofrequency ablation, Irreversible electroporation,and photodynamic therapy. Current studies are investigating the efficacy of these therapies for the management of prostate cancer. Patients with recurrent cancer might particularly benefit from these therapies since they apply highly sensitive imaging to guide specifically targeted treatment.

Pancreatic cancer

Of the minority of patients with resectable disease, surgery remains the only potentially curative option. Radiotherapy and chemotherapy are mainstays in the treatment and palliation of pancreatic cancer. Irreversible electroporation, may present as a potential treatment option for patients with local andenocarcinoma. Martin et al evaluated overall survival in 54 patients with local pancreatic adenocarcinoma; they compared their IRE-treated cohort to matched stage III patients treated with standard therapy. They found a statistically significant increase in local progression-free survival, distant progression-free survival, and overall survival, amongst the patients treated with IRE.

Neurologic

Stroke

A neurological condition occurring when the brain is starved of oxygen and nutrients resulting from the blockage of blood vessels supplying it (ischemic stroke) or from bleeding (hemorrhagic stroke). Symptoms include language, motor, sensory, and vision deficits. Interventional neuroradiologists play a critical role in determining the type of stroke (ischemic or hemorrhagic) using non-contrast computed tomography (CT) imaging or magnetic resonance imaging (MRI), and then treating the stroke using minimally invasive treatment, if possible. Strokes caused by blood clots can be treated by intra-arterial thrombolysis or by mechanical thrombectomy. Strokes caused by bleeding resulting from ruptured aneurysms may be treated by embolization, most commonly using tiny metal coils.

AV malformation

The formation of a "tangle" of disorganized blood vessels, or "arteriovenous malformations", within the brain. Sometimes causing symptoms, other times resulting in brain clots or bleeds, these anomalous structures may be treatable using minimally invasive embolization therapy.

Carotid artery stenosis

A narrowing of the carotid artery supplying the brain which can lead to stroke and disability. Carotid artery stenting (CAS) is an alternative to surgical carotid endarterectomy (CEA) which may be performed in patients who have symptomatic carotid atherosclerotic disease but who are poor candidates for open surgery.

Multiple Sclerosis

Angioplasty of the cervical veins has been suggested as an interventional treatment of chronic cerebrospinal venous insufficiency (CCSVI) that, hypothetically, contributes to the pathogenesis of multiple sclerosis. This hypothesis is highly controversial and treatment of CCSVI by methods of interventional radiology is encouraged only in context of research.

Spine

Spinal fractures

Vertebroplasty and kyphoplasty, the percutaneous injection of biocompatible cement into fractured vertebrae, are two available treatments for vertebral fractures.

Hepatobiliary

Portal hypertension

A condition in which the normal flow of blood through the liver is slowed or blocked by scarring (cirrhosis) or other damage (e.g. hepatitis). Patients with the condition are at risk of internal bleeding or other life-threatening complications. Transjugular intrahepatic portosystemic shunt (TIPS) formation is a minimally invasive treatment to alleviate this impaired blood flow.

Bile Duct Obstruction

Patients with liver cancer, bile duct cancer, cholecystitis, cholangitis, or other hepatobiliary pathology may experience obstruction of bile ducts. Interventional radiologists commonly perform procedures such as percutaneous transhepatic cholangiography (PTHC or PTC) to image these obstructions, and may treat these conditions using percutaneous transhepatic biliary drainage (PTBD), wherein catheters or stents are placed through the skin and into the bile ducts to drain the bile for prolonged periods of time or until surgery.

Women’s Health

Uterine fibroids

Uterine fibroids are non-cancerous growths of the muscular portion of the uterus which may cause pain and heavy bleeding. Interventional radiologists are able to perform non-surgical, minimally invasive treatments of uterine fibroids, called uterine fibroid embolization (UFE), or uterine artery embolization (UAE), using real-time imaging. In this procedure, the interventional radiologist accesses the uterine arteries via a catheter in the femoral or radial artery. The physician guides the catheter into the uterine arteries that supply blood to the fibroid and then releases tiny particles or coils through the catheter to occlude the blood supply of the tumor, causing it to shrink and die.

Fibroid embolization may require a hospital stay of one night, but is often done safely as an outpatient procedure. A procedure without complications can take as little as 30 minutes and the patient can stand up and walk out of the OR unaided. On average, 85-90 percent of women who have had the procedure experience significant or total relief of heavy bleeding, pain and/or bulk-related symptoms. Recurrence of fibroids treated by UFE is very rare.

Pelvic congestion syndrome

A condition caused by pooling of blood in the pelvic veins, possibly resulting in pelvic pain and lower extremity varicose veins. Interventional vein embolization is possible in some cases, eliminating the need for surgical removal of the ovaries and/or uterus.

Infertility

One cause of female infertility is the blockage or narrowing of the fallopian tubes through which eggs pass from the ovary to the uterus. This cause of infertility may be diagnosed using selective salpingography and treated by opening the narrowing using a minimally invasive device such as a balloon.

Kidney

Renal artery stenosis

A narrowing of the arterial supply of the kidneys which may result in high blood pressure (hypertension) or renal insufficiency. Diagnosis of these conditions is made by measuring the diameter of stenosis, the blood pressure across the area of stenosis, renal vein renin sampling, and captopril challenge testing. Stenosis may be treated by balloon angioplasty or stenting.

Renal failure/Dialysis catheter placement

Patients in renal failure may require the placement of a hemodialysis catheter prior to initiating hemodialysis for renal failure.

Dialysis fistula/Arterio-venous graft clot

Dialysis fistulae and grafts may become occluded by blood clots, requiring an interventional “declot” procedure in which mechanical or chemical thrombolysis is performed to eliminate the clot.

Dialysis fistula/Arterio-venous graft failure

Dialysis fistulae and grafts may fail to “mature”, resulting in the need to image the fistula and potentially relieve any blockages using angioplasty.

Nephrostomy tube placement

In conditions where a blockage exists between the kidney and the urethra, such as with kidney stones, a tube may be placed into the kidney under imaging guidance to allow the drainage of urine and to prevent kidney damage.

Renal Sympathetic Denervation

An ablation catheter can be used to denervate the renal arteries in resistant hypertension, often reducing the blood pressure.

Other

Gastric varices

A condition in which blood flow through the vessels around the stomach is slowed or stopped, potentially resulting in bleeding. Interventional treatments include embolization and balloon-retrograde transverse obliteration (BRTO).

Varicoceles and male infertility

A dilatation in the veins of the scrotum which can result in pain, swelling, and infertility. It is potentially treated interventionally using embolization and sclerotherapy.

Central venous access

Vascular access and management of specialized kinds of vascular access devices (VADs). Vascular access devices include nontunneled catheters such as PICC lines, tunneled catheters such as Hickman lines, and fully implanted devices or subcutaneous ports. Access sites include arm/leg veins PICC lines as well as jugular, subclavian and femoral veins and in some cases the inferior vena cava is directly accessed by translumbar and transhepatic routes.

Percutaneous drains

Drainage of fluid from various body compartments using catheters and drains placed through the skin (e.g., abscess drains to remove pus, pleural drains).

Gastrostomy tube placement

In instances where patients are unable to take food by mouth, a feeding tube may be placed through the skin and into the stomach using imaging guidance.

Biopsies

Samples of tissue may be required to identify the cause of certain diseases. Using imaging guidance, interventional radiologists may minimally invasively reach underlying tissue using a small needle to pierce the skin and retrieve tissue samples from the target organ.

Pediatric interventions

Minimally invasive procedures commonly performed in children include obtaining central venous access, gastrostomy tube placement, diagnostic angiography, biopsies, and percutaneous drainage.

Procedures

Common IR procedures are:

• Angiography:

Imaging the blood vessels to look for abnormalities with the use of various contrast media, including iodinated contrast, gadolinium based agents, and CO2 gas.

• Balloon angioplasty/stent:

Opening of narrow or blocked blood vessels using a balloon; may include placement of metallic stents as well (both self-expanding and balloon expandable).

• Cholecystostomy:

Placement of a tube into the gallbladder to remove infected bile in patients with cholecystitis, an inflammation of the gallbladder, who are too frail or too sick to undergo surgery.

• Drain insertions:

Placement of tubes into different parts of the body to drain fluids (e.g., abscess drains to remove pus, pleural drains). A common problem is that these tubes get clogged and have to be replaced or removed before all the material is drained.

• Endovascular aneurysm repair
• Embolization:

Blocking abnormal blood (artery) vessels (e.g., for the purpose of stopping bleeding) or organs (to stop the extra function e.g. embolization of the spleen for hypersplenism) including uterine artery embolization for percutaneous treatment of uterine fibroids. Various embolic agents are used, including alcohol, glue, metallic coils, poly-viny alcohol particles, Embospheres, encapsulated chemo-microsphere, and gelfoam.

Chemoembolization:

Delivering cancer treatment directly to a tumour through its blood supply, then using clot-inducing substances to block the artery, ensuring that the delivered chemotherapy is not "washed out" by continued blood flow.

Radioembolization:

Embolization of tumors with radioactive microspheres of glass or plastic, to kill tumors while minimizing exposure to healthy cells.

• Thrombolysis:

Treatment aimed at dissolving blood clots (e.g., pulmonary emboli, leg vein thrombi, thrombosed hemodialysis accesses) with both pharmaceutical (TPA) and mechanical means.

• Biopsy:

Taking of a tissue sample from the area of interest for pathological examination from a percutaneous or transjugular approach.

• Radiofrequency ablation (RF/RFA):

Localized destruction of tissue (e.g., tumours) by heating.

• Cryoablation:

Localized destruction of tissue by freezing.

• Microwave ablation:

Localized destruction of tissue by heating.

• Central venous catheter placement:

Vascular access and management of specialized kinds of intravenous devices (IVs) (e.g. PIC lines, Hickman lines, subcutaneous ports including translumbar and transhepatic venous lines).

• IVC filters:

Metallic filters placed in the inferior vena cavae to prevent propagation of deep venous thrombus, both temporary and permanent.

• Vertebroplasty:

Percutaneous injection of biocompatible bone cement inside fractured vertebrae.

• Nephrostomy placement:

Placing a catheter directly into the kidney to drain urine in situations where normal flow of urine is obstructed. NUS catheters are nephroureteral stents which are placed through the ureter and into the bladder.

• Radiologically inserted gastrostomy or RIG:

Placement of a feeding tube percutaneously into the stomach and/or jejunum.

• Dialysis access and related interventions:

Placement of tunneled hemodialysis catheters, peritoneal dialysis catheters, and revision/thrombolysis of poorly functioning surgically placed AV fistulas and grafts.

• TIPS:

Placement of a Transjugular Intrahepatic Porto-systemic Shunt (TIPS) for management of select patients with critical end-stage liver disease and portal hypertension.

• Biliary intervention:

Placement of catheters in the biliary system to bypass biliary obstructions and decompress the biliary system. Also placement of permanent indwelling biliary stents.

• Endovenous laser treatment of varicose veins:

Placement of thin laser fiber in varicose veins for non-surgical treatment of venous insufficiency.

Tools

The general basic tools of IR are needles, sheaths, catheters, and wires, however a large subset of highly specialized tools within, and outside of, these basic categories exist. Specialized devices exist to destroy tumors (ablation probes), treat diseased blood vessels (stents and atherectomy devices), stop bleeds (embolics and coils), stop blood clot migration (IVC filters, distal embolization protection devices), etc.

Wires vary in length, material, and shape. These varying properties allow for different functions.

Catheters can be loosely divided into five types:

• Diagnostic angiographic catheters
• Micro catheters
• Drainage catheters
• Balloon catheters
• Central venous catheters