Balloon dilatation of the stenosed internal jugular vein (photo from an X-ray angiograph monitor). While pressure in the balloon is relatively low, stenosis prevents the balloon from inflating in the middle. Further increase in pressure will dilate the narrowing and restore the full blood flow.
Interventional radiology (abbreviated IR or VIR for Vascular and Interventional Radiology, also referred to as Surgical Radiology) is a medical sub-specialty of radiology which utilizes minimally-invasive image-guided procedures to diagnose and treat diseases in nearly every organ system. The concept behind interventional radiology is to diagnose and treat patients using the least invasive techniques currently 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 surgery can now be treated non-surgically by interventional radiologists. By minimizing the physical trauma to the patient, peripheral interventions can reduce infection rates and recovery time, as well as shorten hospital stays.
Interventional radiologists are minimally invasive specialists. The landscape of medicine is constantly changing, and for the past 30 years, interventional radiologists have been responsible for much of the medical innovation and development of the minimally invasive procedures that are commonplace today. Interventional radiologists pioneered modern medicine with the invention of angioplasty and the catheter-delivered stent, which were first used to treat peripheral arterial disease. By using a catheter to open the blocked artery, the procedure allowed an 82-year-old woman, who refused amputation surgery, to keep her gangrene-ravaged left foot. To her surgeon’s disbelief, her pain ceased, she started walking, and three "irreversibly" gangrenous toes spontaneously sloughed. She left the hospital on her feet—both of them. The growth of interventional radiology was fueled by ties between interventionalists such as Charles Dotter and innovative device manufacturers like Bill Cook. Interventional radiologist Charles Dotter, MD, known as the "Father of Interventional Radiology" for pioneering this technique, was nominated for the Nobel Prize in Physiology or Medicine in 1978.
Alexander Margulis coined the term "interventional" for these new, minimally invasive techniques. He emphasized that to continue to be on the forefront of innovation, interventional radiologists must possess special training, technical skill, clinical knowledge, ability to care for patients, and closely collaborate with surgeons and internal medicine subspecialists.
Development of stents began slowly. In 1969, Dotter conceived the idea of expandable stents with an intra-arterial coil spring. The first stents developed by Dotter and Andrew Craig were made of nitinol. Gianturco introduced his self-expandable Z stent. Hans Wallsten introduced a self-expandable mesh stent, Ernst Strecker a knitted tantalum stent and Julio Palmaz his balloon expandable stent, which was later perfected and introduced to clinical practice. Angioplasty and stenting revolutionized medicine and led the way for the more widely known applications of coronary artery angioplasty and stenting that revolutionized the practice of cardiology.
Treatment of GI bleeding has a storied tradition. After introduction of selective vasoconstrictive infusions by Baum, Josef Rösch introduced selective arterial embolization for treatment of uncontrollable bleeding in the early 70s. Anders Lundequist treated variceal bleeding with the technique of transhepatic variceal embolization in the mid 70s. Interventions in the biliary tract were developed by several pioneers. Interventional Radiologist Joachim Burrhenne invented and perfected the technique of percutaneous removal of retained billiary stones. Plinio Rossi and Hall Coons enriched biliary interventions with their work using biliary stents. The innovative interventionalists Kurt Amplatz, Willi Castaneda and Dave Hunter pioneered percutaneous uroradiologic interventions. They popularized nephrostomy drainage, percutaneous stone extraction, and urethral stenting.
The field of interventional oncology was pioneered by IR legends. Bob White pioneered embolization techniques for pulmonary AVMs. Sid Wallace was one of the first to treat bone and kidney tumors by embolization and treatment of disseminated liver metastases.
Today many conditions that once required surgery can be treated nonsurgically by interventional radiologists. Through a small nick in the skin, they use tiny catheters and miniature instruments so small they can be run through a person’s network of arteries to treat at the site of illness internally, saving the patient from open invasive surgery. While no treatment is risk free, the risks of interventional procedures are far lower than the risks of open surgery, and are a major advance in medicine for patients.
Milestones Pioneered by Interventional Radiologists 
• 1964 Angioplasty
• 1966 Embolization therapy to treat tumors and spinal cord vascular malformations by blocking the blood flow
• 1967 The Judkins technique of coronary angiography, the technique still most widely used around the world today
• 1967 Closure of the patent ductus arteriosis, a heart defect in newborns of a vascular opening between the pulmonary artery and the aorta
• 1967 Selective vasoconstriction infusions for hemorrhage, now commonly used for bleeding ulcers, GI bleeding and arterial bleeding
• 1969 The catheter-delivered stenting technique and prototype stent
• 1960-74 Tools for interventions such as heparinized guidewires, contrast injector, disposable catheter needles and see-through film changer
• 1970s Percutaneous removal of common bile duct stones
• 1970s Occlusive coils
• 1972 Selective arterial embolization for GI bleeding, which was adapted to treat massive bleeding in other arteries in the body and to block blood supply to tumors
• 1973 Embolization for pelvic trauma
• 1974 Selective arterial thrombolysis for arterial occlusions, now used to treat blood clots, stroke, DVT, etc.
• 1974 Transhepatic embolization for variceal bleeding
• 1977-78 Embolization technique for pulmonary arteriovenous malformations and varicoceles
• 1977-83 Bland- and chemo-embolization for treatment of hepatocellular cancer and disseminated liver metastases
• 1980 Cryoablation to freeze liver tumors
• 1980 Development of special tools and devices for biliary manipulation
• 1980s Biliary stents to allow bile to flow from the liver saving patients from biliary bypass surgery
• 1981 Embolization technique for spleen trauma
• 1982 TIPS (transjugular intrahepatic portosystemic shunt) to improve blood flow in damaged livers from conditions such as cirrhosis and hepatitis C
• 1982 Dilators for interventional urology, percutaneous removal of kidney stones
• 1983 The balloon-expandable stent (peripheral) used today
• 1985 Self-expanding stents
• 1990 Percutaneous extraction of gallbladder stones
• 1990 Radiofrequency ablation (RFA) technique for liver tumors
• 1990s Treatment of bone and kidney tumors by embolization
• 1990s RFA for soft tissue tumors, i.e., bone, breast, kidney, lung and liver cancer
• 1991 Abdominal aortic stent grafts
• 1994 The balloon-expandable coronary stent used today
• 1997 Intra-arterial delivery of tumor-killing viruses and gene therapy vectors to the liver
• 1999 Percutaneous delivery of pancreatic islet cells to the liver for transplantation to treat diabetes
• 1999 Developed the endovenous laser ablation procedure to treat varicose veins and venous disease 
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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.
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.
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.
A newer Dual Certificate program has just been approved for implementation which is a six year curriculum, similar to the Clinical Pathway, that provides training for Board Certification in both Diagnostic and Interventional Radiology.
Imaging Modalities 
• Fluoroscopy and computed tomography use ionizing radiation that may be potentially harmful to the patient and the interventional radiologist. 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.
- 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.
- 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.
- 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.
- 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.
- Anuerysms, 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.
- Aneurysms of visceral arteries
- Aberrations in normal vascular anatomy treatable by embolization which may cause pain, bleeding, heart problems, or cosmetic concerns.
Various interventional therapies exist to treat cancers. 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)-- 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.
- Hepatocellular carcinoma, the most common form of liver cancer, begins in liver cells known as hepatocytes. Other cancers that affect the liver are known as metastatic liver disease and include colon cancer and neuroendocrine tumors. Curative treatment is liver resection or liver transplant; however, cryoablation, radiofrequency ablation, percutaneous ethanol injection, chemoembolization, and radioembolization are options for patients that are poor candidates for resection or transplantation.
- Lung cancer is the second most commonly diagnosed cancer and the leading cause of cancer death in the United States. Additionally, the lung is a frequent site for metastatic disease, with common primary malignancies including those of the breast, colon, prostate, kidney and bladder, as well as sarcoma. Surgery (lobectomy) remains the reference for treating early stage lung cancer; however, most patients are not surgical candidates at the time of diagnosis. For these patients, minimally invasive treatment options, including high-dose radiation therapies and percutaneous thermal ablation therapies such as radiofrequency ablation, microwave ablation, and cryoablation have emerged as safe and effective treatment alternatives.
- 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.
- 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.
- 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.
- 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 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 makes a tiny nick in the skin in the groin and inserts a catheter into the femoral artery. The physician guides the catheter into the uterine arteries that supply blood to the fibroid and then releases tiny particles through the catheter to occlude the blood supply of the tumor, causing it to shrink and die.
- Fibroid embolization typically requires a hospital stay of one night. 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- A condition in which blood flow through the vessels around the stomach is slowed or stopped, potentially resulting in bleeding. Interventional treatments include embolzation and balloon-retrograde transverse obliteration (BRTO).
- 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).
- 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.
- 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.
Common IR procedures are:
- Imaging the blood vessels to look for abnormalities with the use of various contrast media, including iodinated contrast, gadolinium based agents, and CO2 gas.
- Opening of narrow or blocked blood vessels using a balloon; may include placement of metallic stents as well (both self-expanding and balloon expandable).
- 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.
- Placement of tubes into different parts of the body to drain fluids (e.g., abscess drains to remove pus, pleural drains).
- 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.
- 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.
- Embolization of tumors with radioactive microspheres of glass or plastic, to kill tumors while minimizing exposure to healthy cells.
- Treatment aimed at dissolving blood clots (e.g., pulmonary emboli, leg vein thrombi, thrombosed hemodialysis accesses) with both pharmaceutical (TPA) and mechanical means.
- 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.
- Localized destruction of tissue by freezing.
- Metallic filters placed in the inferior vena cavae to prevent propagation of deep venous thrombus, both temporary and permanent.
- 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.
- 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.
- Placement of a Transjugular Intrahepatic Porto-systemic Shunt (TIPS) for management of select patients with critical end-stage liver disease and portal hypertension.
- 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.
There are a number of catheters used in interventional radiology that can be loosely divided into five types:
- Diagnostic angiographic catheters
- Micro catheters
- Drainage catheters
- Balloon catheters
- Central venous catheters
See also 
- Cardiac catheterization
- Interventional neuroradiology
- MRI Robot: MRI Stealth Robot Technology
- URobotics: New technologies for image-guided intervention
- Radiation protection
- Society of Interventional Radiology -- Global Statement Defining Interventional radiology. http://www.sirweb.org/news/newsPDF/IR_Global_Statement.pdf
- SIR - Fellow Residents and Students - APDIR
- The Society for Pediatric Radiology
- "Imaging studies challenge Zamboni theory of MS". Canadian Medical Association. Retrieved 14 April 2011.
- "FDA Safety Communication: Chronic Cerebrospinal Venous Insufficiency Treatment in Multiple Sclerosis Patients". Food and Drug Administration. May 2012.
- "Percutaneous venoplasty for chronic cerebrospinal venous insufficiency for multiple sclerosis". National Institute for Health and Clinical Excellence. March 2012.
- Nonsurgical Treatment for Spinal Fractures From Osteoporosis - SIR
- Male Infertility and Varicocele Treatment - SIR
- Central Lines, Ports and Feeding Tubes - SIR
- Image-Guided Needle Biopsy - SIR
- Pediatric Interventional Radiology - SIR
Helpful Resources 
• Historic Highlights of Interventional Radiology, by Josef Rösch of Dotter Interventional Radiology.
• Abrams’ Angiography: Vascular and Interventional Radiology. Herbert L. Abrams (Editor), Stanley Baum (Editor) and Michael J. Pentecost (Editor) Little Brown and Co., 2005. ISBN 0781740894
• Advanced Radiographic and Angiographic Procedures: With an Introduction to Specialized Imaging. Patrick A. Apfel, Marianne Rita Tortorici. F A Davis Co., 2010. ISBN 0803612559
• Handbook of Interventional Radiologic Procedures Krishna Kandarpa (Editor) and John E. Aruny (Editor). Lippincott Williams and Wilkins Publishers, 2010. ISBN 0781768160
• The Birth, Early Years, and Future of Interventional Radiology by Josef Rösch, Frederick S. Keller, and John A. Kaufman. (2003) J. Vasc. Interv. Radiol.14: 841-853.
• The Catheter Introducers by Leslie A. Geddes and LaNelle E. Geddes of Cook Group Incorporated, Mobium Press, Chicago. 1993. ISBN 0916371131
• The Ship in the Balloon: The Story of Boston Scientific and the Development of Less-Invasive Medicine by Jeffrey L. Rodengen. Write Stuff Enterprises, Inc., Fr Lauderdale. 2001. ISBN 0945903502
- Society of Interventional Radiology
- Cardiovascular and Interventional Radiological Society of Europe
- Society of Pediatric Interventional Radiology
- The Endovascular Forum
- Interventional radiology procedures