This section of our website is dedicated to students interested in interventional radiology and is overseen by our Medical Student Council.

Under the drop-down menu at the top of the screen labeled "Medical Students" you will find an introduction to the specialty as well as great resources on how to get involved, explore IR, and become a competitive applicant for residency.

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Physician Spotlight: Dr. Fabian M. Laage Gaupp
November 14, 2020

Dr. Fabian M. Laage Gaupp

Please tell us more about yourself and your medical training in Germany?

I spent my childhood from kindergarten to medical school in Munich. In Germany, you go to school for up to 13 years and finish high school to be eligible to go to university. There’s no college system, which means when you are graduating from high school, which is usually when you are 18 or 19 years old, you have to immediately decide whether you want to go to medical school. I finished high school when I was 19 and decided to go to medical school. Admission to medical schools is different from state to state; some states have an admission test; others have an interview process. When I was applying in Bavaria in 2007 it was pretty straightforward and only based on one single number: the two-digit high school diploma grade average. In Germany, students are graded from 1 to 6 with a 1.0 being perfect, and anything past 4.0 is a fail. Given that my score was competitive, and I wanted to stay in my hometown of Munich I only applied there, and my application was successful.  

Do you have any thoughts about your medical school experience in general?  

I think overall my experience was excellent. International medical graduates are sometimes worried that they’re going to come to the US and be at a disadvantage from the knowledge standpoint. I think for many countries that is simply not true. I think that the level of medical education is actually excellent in a lot of countries. However, at the residency training level there is a huge difference between most of the world and the US.

When and how did you decide to continue your medical training in the US?

In Germany, medical school is about 6-7 years long, depending on how much research you do. Halfway through medical school, I decided to do some research in the US, so I went to Yale for about 10 months and worked on a neuroscience research project. At that time, I was in touch with US medical students and residents and started exploring residency in the US. Subsequently, I sought potential clinical electives in the US. I did an elective in head and neck surgery at the Massachusetts Eye and Ear Infirmary in Boston. Meanwhile, I took Step 1 while I was doing my research at Yale in early 2012. I returned to the US during my final year of medical school in 2014 and spent four months in the US doing hands-on electives in general IR and Neuro-IR at Cornell (two months) and Harvard (Brigham and Women’s Hospital and Beth Israel, one month each). 

Can you please tell us more about your clinical rotations in the US?

I came up with a few US universities that offer electives for international students by Google search. I then applied for electives at Cornell, Harvard, and UCSD. I ended up going to Cornell for two months and then Harvard for two months. As this was organized through their elective offices it meant that I had to pay tuition. I was lucky because I was a scholar of the German National Academic Foundation, which supported me with a monthly stipend and covered tuition and some travel expenses for my international electives in the US (over $2000 US a month at Cornell and over $4000 US a month at Harvard). I could not have done these electives without the generous support of the German National Academic Foundation as tuition was just too expensive for my personal budget! To get into these electives, you have to be in your final year of medical school and unfortunately a lot of these programs are not available for someone who already graduated from medical school, even if it was recently. You will also need to show your vaccination records, pass the TOEFL exam and meet other requirements for most universities. The application process can be quite involved at times but there is an overlap in requirements so once you have sent one application the next one becomes easier. 

How did your journey to IR start? 

It was a pure coincidence! I didn’t really know anything about IR in medical school. Part of the research project I was doing at Yale related to Neuroradiology. Because of that, I got interested in Diagnostic Radiology, so I decided to do my electives in Radiology. I started the first month of my radiology elective at Cornell in late 2013, where I happened to be placed in an IR rotation. It took only a day for me to be completely amazed by this field. IR in my opinion was the coolest specialty and presented a perfect mix of Surgery and Radiology. I requested to stay in IR and Neuro-IR for the following month. When I went to Boston after I already requested beforehand to be placed in IR or Neuro-IR. Thankfully they were flexible and allowed me to do Neuro-IR for two months, which was really cool. I spent my entire final year of medical school abroad. I did four months of electives in Japan before I came to the US. Medicine in Japan, surgery in western Samoa, and IR in the US.

Were you interested in surgery before IR? 

Yes, before I knew what IR was, I considered orthopedic surgery and did some research in Neurosurgery back in Germany.  

Why did you decide to continue your training in the US? 

I think training here is exceptional and, in my opinion, the best in the world. The German healthcare system is overall very good, but if you look at the way training works in the hospital it’s not organized. There is no structure. The contracts are open-ended, and you don’t really know when you will graduate until you complete your logbook, which usually means you must be on good terms with your boss and are completely at their mercy. For example, if your boss starts working for a different hospital it could completely mess up your studies and you may even be forced to move with your boss in order not to disrupt your training. Overall, residency training in the US is very well structured. You know you will rotate in all sub-sections of radiology or whatever specialty you train in. Educators in the US place very high value on teaching and attendings take the time to explain and work one on one with trainees. In many other countries, including Germany, there is a lack of dedicated teaching happening on clinical services in the hospital. 

What are the biggest challenges you faced as an IMG?

One of the biggest challenges are the expenses! I was fortunate because I had a scholarship, but for a lot of people, this can be a limiting factor. The second challenge is to excel in the USMLEs. Third, is to get the necessary letters etc. which you only can achieve if you get clinical rotations in the US and of course you need to pay for those, and then you will have to do an excellent job to get the letters. Basically, all these three things hinge mostly on the expenses ultimately. US medical students pay just the same, but I think subjectively there is a difference because in Germany and many other European countries people are not used to paying for education, which is considered a basic right. Therefore, people are not willing to take out money and take a risk and apply for US residency. Only people that are really determined to complete residency training in the US. Finally, there are organizational challenges of course. It requires a lot of correspondence and coordination. There is complex paperwork between your home medical school and US elective programs required to make sure electives, USMLE accreditation etc. work out and are approved. Indeed, it can really be a bureaucratic nightmare, but this is life and probably a good lesson for future challenges!

What about challenges during the application process?  

I was set to graduate from medical school in Germany in November, so I didn’t even know if that was going to give me enough time to get my ECFMG paperwork lined up before the deadline. I applied in September when I was in my last year of medical school and only had my step 1 score ready. I didn’t even take other USMLE exams, which also put me at a disadvantage because a lot of programs filter IMGs based on ECFMG certification. I applied to about 25 radiology and 25 preliminary residency programs but only received a total of eight interviews. Fortunately, all of those were competitive programs where I knew someone or I completed a rotation including Harvard, Yale, Emory, and Cornell for Radiology, and preliminary year interviews at Mayo Clinic (Rochester), Beth Israel in Boston, Cornell, and Yale.  

What is your advice for international medical students and graduates who pursue IR?

Do as many electives as you can in the US so that you have enough contacts and can get excellent letters of recommendation. Also, make sure you take your USMLE exams and get your ECFMG certificate before you apply. You need something to differentiate yourself from other candidates. Let’s say two applicants apply, one is from the US and one is from Germany with similar step scores and they both seem like reasonable people. Why would programs choose a German over an American applicant? With US graduates, there is no language barrier and there is no visa-related risk for the program. The only reason they will consider IMG’s is if the applicant brings something to the table, such as solid research experience. Of course the more research, the better! However, some very well published applicants don’t get into Radiology probably because of low USMLE scores, visa issues, or poor interview performance. 

Doing research in the US is recommended. However, it’s not just about what you’ve published. It is more about connections, and therefore I would say clinical research can be just as valuable as basic science. As an IR applicant, clinical research related to IR is more relevant of course. It would be very difficult for radiologists to figure out the impact and quality of non-radiology journals and articles. Basically, a third author article in JVIR can have far more value than a first-author article published in the highest impact factor journal for orthopedic surgery. Additionally, If you’ve actually done research relevant to faculty who interview with you, you will have something in common to talk about. Just make sure to be well prepared for specific questions. 

Do you recommend applying to DR or IR or both as an IMG?

If you want to go into IR, it’s better to have IR clinical research experience in your profile. Be honest when applying to DR/IR and mention that you are primarily interested in IR, and that doesn’t mean at all that you don’t care about DR. Be mindful that you might change your mind in residency. In summary, apply to both and be open to the people interviewing you about what your goals are. 

What are your research interests?

IR training in Africa! How to bring IR education to resource-limit settings. I think that people really underestimate the potential for IR in low to middle-income countries. There is a misconception that people think IR can only be done in high-income countries. It is simply not true. It has been estimated that more than half of the world’s population doesn’t have proper access to IR! In Africa alone over 1 billion people right now have no access to even basic IR procedures like abscess drainage, biliary drainage, nephrostomy placement and many other life-saving procedures. 

What is your favorite IR procedure, and why? 

Embolization for hemorrhage in the setting of trauma. I still find it fascinating that instead of doing a big open surgery you can go through a pinhole in the groin and save someone’s life by localizing and embolizing their bleed using coils, gelfoam, or other materials. These cases are very satisfying. 

What is your favorite inspirational quote?

If there is a will, there is a way! (I have to say it’s my favorite quote as well) Don’t accept impossible as an answer, try a different approach, and success will follow. 

WHY IR in Bullet points?

1. Minimally invasive with immediate impact

2. Technology-driven

3. Delivers better results for patients 

What do you think about the differences between European IMGs like yourself and others?  

European medical schools, including Germany, are very flexible. This provides great opportunities for research and clinical electives. I was able to go abroad and do research and electives throughout medical school, which may not be possible in all other countries to my knowledge. I think exchange of knowledge and ideas between medical professionals from different continents is extremely important, now more than ever.  

What is the success formula to match into IR residency (bullet point)?

1. Have a plan; don’t try to wing it! Take all USMLE exams on time.

2. Do as many elective clinical IR rotations or observerships in the US as possible. And if you can’t do that at least try to do relevant clinical IR research in the US. 

3. Study hard for the USMLE exams because the score matters and can set you apart from other candidates. 

4. Try to go to IR meetings, meet new people in IR, and build your network.

5. Apply to both IR and DR.

I would urge all IMGs to take the USMLE Step 1 before it becomes a pass/fail exam. I believe this could be a significant disadvantage for IMGs as many program directors don’t know most foreign medical schools very well, and no matter how accomplished you are and how excellent your medical school is, you will not have your step 1 score to set you apart.

If you could do it all over again, would you change anything? 

I don’t think so. It worked out well for me. I was always pretty organized about my applications etc. which probably worked out to my advantage. I wouldn’t really change anything.

Where do you see yourself in five years?

I see myself doing academic interventional radiology and expanding on global IR training programs. I am open-minded, and I can see myself working pretty much anywhere including Asia, the Middle East, or the USA. Currently, there is a complete hiring freeze due to the coronavirus pandemic, so we will see. Hospitals are losing a lot of money from canceling elective procedures. I hope that by next year things will improve.

What do you feel most passionate about?

My contribution to the Global IR training program in Tanzania! I got involved with this when I was a second-year radiology resident. I first went to East Africa with Dr. Frank Minja, who is a neuroradiology attending at Yale. I went with him to check out whether it would be possible to do IR and to start the first IR training program in East Africa. In October 2018, we officially started the training program. Every two weeks an IR team travels from the US to Tanzania and provides training to local IR fellows. This Master of Science in Interventional Radiology program at Muhimbili University of Health and Allied Sciences in Dar es Salaam is, to my knowledge, the first accredited IR training program in sub-Saharan Africa. It’s a two-year fellowship program which Tanzanian radiologists can enter after completing a 3-year diagnostic radiology residency, corresponding to the IR residency system in the US. 

This is fantastic! Can you tell me more about the progress and the future global IR program?

We published our initial paper in JVIR last year. I’m now writing up the second paper summarizing results of the first 16 months of the program. So far, we have performed over 350 IR procedures, anything ranging from biopsies to uterine and splenic artery embolization or embolization of pseudoaneurysms. If it wasn’t for the program, many of those patients would not have received any treatment because there are no surgical alternatives to some of these IR procedures.  For example, in a septic patient with hydronephrosis or in a patient with biliary obstruction in advanced cholangiocarcinoma there is no real surgical alternative. I believe IR will have a great future in low-income countries, and the overall impact of IR in these countries will be very significant, maybe even more so than here. Surgical complication rates tend to be higher in low-income countries, which explains why offering minimally invasive alternatives makes such a big difference there.  

IOC Interviewer: Amir Pirmoazen, MD

IOC/MSC Editors: Edna Wang; Yi Yang, MD, MPH; Andrew Moore, MD

Transcatheter Arterial Embolization as a Treatment for Medial Knee Pain in Patients with Mild to Moderate Osteoarthritis
October 31, 2020

Review by: Robert Wu, 2020


Osteoarthritis of the knee is the most common cause of disability in the lower limb in adults over 50 years old, impacting the lives of more than 30 million Americans alone. In more severe cases, patients may experience persistent pain that disrupts sleep or experience knee instability that lead to further disability from falls. Treatment for advanced stage knee osteoarthritis is generally treated with arthroplasty or knee replacement surgery, while mild to moderate osteoarthritis is treated symptomatically with exercise, pain medications, steroid injections. These treatments are not without side effects, however, as chronic medication use may lead to organ dysfunction, opiate addiction and GI ulcers while steroid injections generally require multiple administrations and have mixed efficacy.  

The pathogenesis of osteoarthritis was previously thought to be due to wear and tear of the joint. We now know that pathogenesis also involves chondrocytes and inflammatory cells in surrounding tissues which degrade and remodel bone.  New research suggests that angiogenesis also occurs in osteoarthritis. Angiogenesis helps to create a proinflammatory environment that enables chondrocytes to break down cartilage.  In addition, research has linked angiogenesis in the synovium and periarticular bone to the growth of new sensory nerves.  When stimulated by chemical or mechanical means, these nerves are thought to contribute to osteoarthritis pain.    

Prior case reports have demonstrated that transcatheter arterial embolization has been successful in treating refractory tendinopathy and adhesive capsulitis based on the mechanism aforementioned. This prospective, single institution, non-randomized clinical study assesses the efficacy and adverse effects of transcatheter arterial embolization on chronic knee pain due osteoarthritis.

Study Population and Treatment Protocol

From June 2012 to December 2013, this study enrolled 14 subjects (8 female and 6 male) with a mean age of 65.2 years (range 49-76 years) and was conducted at Edogawa Hospital at Tokyo, Japan. Patients included had moderate to severe knee pain resistant to 3 months of conservative treatment, while those with severe enough OA to be candidates for total knee arthroplasty, local infection, malignancy, advanced atherosclerosis, rheumatoid arthritis, and prior knee surgery were excluded.  

For the embolization technique, a 3F introducer sheath helped establish ipsilateral femoral access after which a 3F angiographic catheter was introduced into the popliteal artery so that 3 – 5 ml iodinated contrast could opacify the genicular arteries and neovascular vessels. Once the abnormal vessels were located, they were selected for using a 2.4F microcatheter that was inserted through the 3F catheter and embolized with imipenem/cilastatin sodium (IPM/CS) in 11 cases and 75 Embozene microspheres in 3 cases.

Data Collection and Statistics

Dunnett’s post hoc test was used to determine changes in the WOMAC score from prior to the procedure to 1, 4, and 12 months post procedure. The Western Ontario and McMaster University Osteoarthritis Index (WOMAC) questionnaire uses 24 questions on daily activities to produce three subscores for pain, stiffness, and physical function that when totaled is the total WOMAC score. Additionally, pain symptoms and use of other therapies were also evaluated at baseline, 1, 4, and 12 months post procedure.   

Results and Outcomes

Technical success rate was 100%. No adverse events, tissue necrosis, dermal ulcers, ligament rupture, or peripheral paresthesia occurred.  One patient, however, experienced moderate subcutaneous hemorrhage at the puncture site that resolved in one week. The average WOMAC pain score decreased from 12.2 ± 1.9 to 3.3 ± 2.1 1 month post procedure to 1.7 ± 2.2 4 months post procedure (p < 0.001). The mean WOMAC total score decreased from 47.3 ± 5.8 to 11.6 ± 5.4 at 1 month, and to 6.3 ± 6.0 at 4 months (p < 0.001). Continued improvement in WOMAC scores were seen in most patients at final follow up which averaged 12 ± 5 months (range 4-19 months). Changes in pain symptoms as well as use of NSAIDs and HA injections are summarized in Table 1.

Table 1: Progression of pain symptoms and additional pain treatment utilization



1 Month Post Op

4 Month Post Op

12 Month Post Op

Pain during walking





Pain with stairs




Patients receiving NSAIDs





Patients receiving HA injection





The pain from osteoarthritis is currently not well understood as cartilage, the primary site of pathology in OA, lacks pain receptors.  This present study suggests that abnormal neovessels supplying the synovium, periosteum, infrapatellar fat pad, and medial meniscus base play a significant role in the pathogenesis of pain in OA since embolization of the neovessels supplying these structural elements provided pain relief. Two mechanisms for pain relief from neovascular embolization have been proposed because pain symptoms were significantly relieved at two time points: immediately after embolization and then again several weeks or months later. It has been proposed that the immediate pain relief is due to reduced sensory nerve stimulation that occurs with decreasing abnormal blood flow.  On the other hand, later pain improvement was attributed to a reduction in the influx of inflammatory cells into synovial tissues. 

The present study possesses some limitations.  Given the small cohort size and relatively short follow up period, the incidence of complications could not be adequately determined. Sources of potential bias include the lack of blinding patients to treatment, lack of a control group, and ability for patients to continue pain relief therapies used before embolization.  Future research is needed to validate this experiment and to better explore possible complications over a longer followup period.


  1. Power SP, Cairns B, Prabhudesai V, et al. Genicular Artery Embolization for Recurrent Hemarthrosis of the Knee Following Total Knee Arthroplasty: A Single Centre Experience: Canadian Association of Radiologists Journal. Published online March 23, 2020. doi:10.1177/0846537119899550
  2. Bagla S, Piechowiak R, Hartman T, Orlando J, Del Gaizo D, Isaacson A. Genicular Artery Embolization for the Treatment of Knee Pain Secondary to Osteoarthritis. Journal of Vascular and Interventional Radiology. 2020;31(7):1096-1102. doi:10.1016/j.jvir.2019.09.018
  3. Landers S, Hely R, Page R, et al. Genicular Artery Embolization to Improve Pain and Function in Early-Stage Knee Osteoarthritis—24-Month Pilot Study Results. Journal of Vascular and Interventional Radiology. 2020;31(9):1453-1458. doi:10.1016/j.jvir.2020.05.007
  4. Landers S, Hely A, Harrison B, et al. Protocol for a single-centre, parallel-arm, randomised controlled superiority trial evaluating the effects of transcatheter arterial embolisation of abnormal knee neovasculature on pain, function and quality of life in people with knee osteoarthritis. BMJ Open. 2017;7(5):e014266. doi:10.1136/bmjopen-2016-014266
  5. Okuno Y, Korchi AM, Shinjo T, Kato S. Transcatheter Arterial Embolization as a Treatment for Medial Knee Pain in Patients with Mild to Moderate Osteoarthritis. Cardiovasc Intervent Radiol. 2015;38(2):336-343. doi:10.1007/s00270-014-0944-8

The Invention of TIPS: Discovery by Accident
October 30, 2020

By Ravish Patel

What do the slinky, chocolate-chip cookies, fireworks, and the transjugular intrahepatic portosystemic shunt (TIPS) all have in common? They were all discovered by accident! It’s hard to think that a medical procedure with such a long name could have been discovered by accident, but sometimes accidents result in some of the best discoveries, such as TIPS (and of course, chocolate chip cookies!).1

The year was 1968. Dr. Josef Rösch was a visiting radiologist at the University of California, Los Angeles (UCLA), where he was performing procedures on canines. He was performing a procedure called a diagnostic transjugular cholangiography, in which the physician drives a catheter and needle from the hepatic vein (see image, light blue) through the liver and into the bile ducts (see image, green). This allowed him to fill the bile ducts with dye which could be visualized on x-ray to see if there was an obstruction or abnormality of the bile ducts.2

During these procedures, the needle would accidentally sometimes enter the portal vein (see image, dark blue) instead of the bile duct.3 While this isn’t what Dr. Rösch had originally intended, this accident eventually led to the invention of the TIPS procedure. He kept in mind what Charles Dotter, one of his mentors who is widely considered the father of interventional radiology, had told him: to always think about potential interventional treatment during diagnostic procedures. With this in mind, Dr. Rösch realized the treatment potential for a connection between the hepatic and portal veins that bypassed the liver.

Patients with liver disease whose portal veins had a hard time draining into the hepatic veins were ideal candidates for such a procedure. Bypassing the diseased liver allowed these patients to reduce the backup in the portal vein and decreased their risk of bleeding in other places, which was a major source of death for these patients.

The original TIPS design has been revised multiple times to culminate in the TIPS procedure of today. Since then, metal stents have been used to open the tunnel between the two vessels. Today, we have stents covered in a chemical that helps keep the lumen patent since the original ones had difficulty staying open for longer than two weeks. This procedure goes to show that keeping an open eye can birth innovation from accident.


1. Krueger A. 15 Life-Changing Inventions That Were Created By Mistake. Business Insider. https://www.businessinsider.com/these-10-inventions-were-made-by-mistake-2010-11. Published November 16, 2010. Accessed July 28, 2020.

2. Rösch J. Development of transjugular intrahepatic portosystemic shunt. J Vasc Interv Radiol. 2015;26(2):220-222. doi:10.1016/j.jvir.2014.11.011

3. Portal Vein and Hepatic Vein in Liver. Anatomy Note. https://www.anatomynote.com/human-anatomy/blood-supplement/portal-vein-and-hepatic-vein-in-liver/. Published August 11, 2019. Accessed July 28, 2020.

Ultrasound Innovations in IR
October 30, 2020

By Isaac Levine, Ryan Morrison, Shivam Kaushik, and Deepak Iyer


Since the 1920s, when it was first used as a treatment for arthritis and gastric ulcers, ultrasound (US) technology has come a long way1. In 1947, neurologist Dr. Karl Dussik pioneered its use as a diagnostic tool in his attempts to image the cerebral ventricles2. In 1949, Dr. George Ludwig successfully imaged gallstones embedded in soft tissue, and seven years later Dr. Ian Donald used the one-dimensional A-mode to measure the diameter of the fetal head. In 1950s, Brown introduce a “two dimensional compound scanner” which enabled clinicians to visualize tissue density, an advancement widely considered crucial to US’s future medical usefulness.

Commercial use of US was launched in the 1960s with the advent of B mode devices, and in the 1970s gray-scale and real-time scanners were introduced. Doppler technology, commonly used to assess blood circulation and flow, was added to the growing ultrasound toolbox in the 1980s, and since then the technology has continued to advance, with 3D image processing and small handheld units increasingly being used at the bedside2.

The first documented US guidance in interventional radiology appeared in the early 1970s, used for renal and hepatic biopsies and drainage of abscesses. It wasn’t until the later part of that decade, and into the early 1980s with the introduction of real-time imaging that interventional use of US really took off. In 1983, US was successfully used for in-utero hydrocephalus shunting, and soon it had been applied to pericardiocentesis, soft tissue ablation, transhepatic cholangiography, cholecystostomy, gastrostomy, nephrostomy, and arterial and venous catheterization, and much else besides3. Since then, the role of US in interventional procedures has only grown, and it is currently recognized as a key component of the IR armamentarium in a wide range of roles.


The miniaturization of ultrasound system electronic hardware has unlocked the ability to turn a large, heavy hospital-based cart into a transducer plus system that fits entirely in the palm of your hand. These hand-held devices enable true point-of-care ultrasound at a fraction of the cost of a cart-based system. Image quality is sacrificed for portability; however, with continuous improvement, these devices may one day have equivalent image quality to that of a cart-based system. As the cost of these devices drops below thousands of dollars, they may also one day replace the stethoscope as a quick and easy way to examine vital functions of patients.

Therapeutic ultrasound products that use high intensity focused ultrasound (HIFU) to cause tissue destruction via thermal effects and cavitation are now available as alternatives to radiation treatment. Magnetic resonance (MR) guided HIFU has been around for many years and has successfully treated a wide variety of pathologic tissue types. New products are now hitting the market that utilize real-time ultrasound monitoring to track tissue changes in order to only ablate specific tissues of interest.

Artificial intelligence algorithms are starting to make their way into ultrasound imaging. One of the first commercially available products is an echocardiogram algorithm which allows for fast measurement of cardiac parameters such as heart chamber diameters. This can significantly improve the speed which an echocardiogram can be performed and may also improve the accuracy of measured parameters.

Advances in material science have modified the traditional polycrystalline ceramic material such as PZT (lead-zirconate-titanate) to new, highly efficient materials such as PMN-PT (lead magnesium niobite/lead titanate) PZN-PT (lead zirconate niobite/lead titanate). These materials result in a significant increase in penetration, resolution, and sensitivity in imaging performance.

By cutting ultrasound piezoelectric crystal in three different rows of elements, two focal zones are established at different depths. Clinically, this translates to very high-resolution signals at more than one depth meaning the overall ultrasound image will be extremely high-resolution.

The ability to merge real-time ultrasound with a previous MR, CT, or PET scan allows for an even more powerful diagnostic visualization tool. Extremely precise motion tracking of the ultrasound transducer unlocks the ability to fuse the multiple modality images together. Clinicians can visualize the best aspects of all the imaging modalities in one synchronized image.

Novel manufacturing techniques allow for the ultrasound sensor to be attached to an application specific integrated circuit (ASIC) which moves much of the systems’ electronics into the handle of the transducer. Much of the beamforming of the ultrasound wave now happens inside of the handle of the transducer. What this means is that a transducer can now have tens of thousands of individual elements in a 2D array versus the typical 128 elements of a traditional transducer. Clinically, what this enables is high-resolution, real time visualization of the X, Y, and Z planes at the same exact time and also the rendering of a 3D ultrasound image without the use of a motorized transducer.

Ultrasound transducers come in a wide variety of sizes and shapes to best fit the clinical application they are used in. The typical linear or curvilinear transducer has evolved into intravascular, transesophageal, transrectal, and transvaginal transducers for high fidelity imaging of the anatomy of interest. Intravascular Ultrasound (IVUS) features an ultrasound transducer on an intravascular disposable catheter, which is used heavily in Interventional Radiology procedures to monitor stenosis of vessels among other things. Transesophageal echocardiography (TEE) is often used to monitor heart valves, upper aortic dissections and tears, or congenital heart defects by providing a 3D image of the heart. Transrectal and transvaginal probes can provide images of male and female anatomy that are not possible with traditional probes such as high-resolution imaging of the prostate.


Since the 1960s ultrasound imaging systems have been widely distributed and used across the world. By the 2000s there were portable stations and by the 2010s advances in technology allowed for wireless imaging transducers to be paired with portable PC tablets. These developments point to improved workflow to make the healthcare system more efficient for patients and physicians through fewer keystrokes and automatic lesion seg4.

Artificial intelligence integration into ultrasound workstations allow for automation for certain tasks such as having voice recognition and hands free control of instrumentation.

Ultrasound is a noninvasive procedure in terms of radiation dosage so patients typically have no adverse outcomes.  Complications arise due to image quality and user error.

Evidence on trends show an increase in ultrasound usage in lower and middle income countries. Usage of ultrasound across countries has increased by 24% since 2010 from 50 to 62 countries across the globe5. The World Health Organization (WHO) highlights the impact of ultrasound technology along with its importance in healthcare.  There is a goal of establishing 90% of imaging needs in the primary care setting with ultrasound technology along with a WHO manual of usage.


1. Kane D, Grassi W, Sturrock R, Balint PV. A brief history of musculoskeletal ultrasound: ‘From bats and ships to babies and hips’. Rheumatology (Oxford). 2004;43(7):931-933.

2. Thomas A, Banerjee AK. The history of radiology. First edition. ed. Oxford, United Kingdom: Oxford University Press; 2013.

3. McGahan JP. The history of interventional ultrasound. J Ultrasound Med. 2004;23(6):727-741.

4. Fornell D. 5 Key Trends in New Ultrasound Technology. Imaging Technology News. 2019. Published February 7, 2019.

5. Stewart KA, Navarro SM, Kambala S, et al. Trends in Ultrasound Use in Low and Middle Income Countries: A Systematic Review. Int J MCH AIDS. 2020;9(1):103-120.

Innovation of Catheters
October 4, 2020

By Isaac Levine, Shivam Kaushik, and Deepak Iyer


Long before Dr. Seldinger and Dr. Dotter went to work, the first iterations of the catheter began to find their way into clinical care. In fact, the concept of catheters have existed for centuries.

The ancient Greeks would create thin tubes made of materials they could find (gold, silver, brass, etc) to try and treat urinary difficulty and discomfort. They would modify the wire until they were able to make it work. Centuries later in America, Benjamin Franklin began to tinker with the invention to treat his brother’s kidney stone. At this point in time, catheters served a very niche purpose of treating urological conditions. It wasn’t until the 1800s when catheters became sized upon realization that poorly sized catheters can cause abrasions that promote bacterial infections as well as advancements in available technology. In the early 20th century, the indwelling Foley Catheter was invented and has since become a standard form of treatment, subsequently disrupting the biomedical device industry. Since then, the indications for catheters have increased dramatically. In 1923, the first angiography was performed on a human body, and the technology associated with this historic concept has improved dramatically ever since1-3.

Within the past few decades, the catheter has undergone a variety of improvement due to increased research and technological advancements within the industry. In 1964, Dr. Charles Dotter pioneered the field of IR by performing percutaneous angioplasty4. Since then, there have been a variety of iterations of the technology such as soft double-lumen catheters. Further applications of the catheter have also been created allowing for innovative solutions to major medical problems. For example, transjugular intrahepatic portosystemic shunts have been a mainstay for the field of IR to treat portal hypertension since 19674,5. Catheters are now used in the field of IR to treat non-vascular indications such as diseases of the pancreas, kidney, and spinal cord. In this highlight of catheter innovations, we hope to explore some of the current advancements in catheter innovation.


What are commonly used catheter options these days?
  • Selective vs. Non-selective (Flush)
  • End hole vs. Side hole
  • Hydrophilic vs. Non-hydrophilic

In a broad sense, catheters can be divided into two groups — selective catheters and non- selective (flush) catheters. Flush catheters are used for high-flow injections into large vessels. They therefore are designed to have high wall strength, and often have multiple side holes to prevent catheter or vascular damage during power injections due to the end-hole jet effect1.

Commonly-used flush catheters include Angiodynamics’ Omniflush and Pigtail6.To this end, they are designed with increased rotational stiffness in order to transmit any manipulation of the trailing end reliably to the leading end. In addition, selective catheters come in many different shapes to accommodate specific anatomy in an effort to increase selectivity and stability. The angle of a catheter’s primary curve is designed to approximate the takeoff angle of the target vessel to enhance selectivity. Secondary curves may also be employed, to enhance stability. For example, the Angiodynamics Mikaelsson catheter ( ) is designed to maintain position of the catheter while working in an aortic branch vessel, as the posterior bulge opposes the wall of the aorta, maintaining the catheter in the vessel ostium.

Cobra’s (Cordis) shape ( ) has similar uses, although its decreased curve allows for easier advancement over a guidewire6.

Microcatheters, typically 3F or smaller, make up a subset of selective catheters. These are often used when sub-selection of small vessels is critical, such as vascular embolization for hemorrhage or chemo- or radioembolization1.

Catheters can also be broken down into categories based on hydrophilicity. Hydrophilic catheters (e.g. Terumo’s Glidecath), commonly made with Teflon (polytetrafluoroethylene [PTFE]-62) glide smoothly through vessels, an important point in highly tortuous and smaller vessels. However, this very property means that hydrophilic catheters have limited positional stability. In addition, due to the lower rotational stiffness of materials used in their production, these catheters are more difficult to manipulate accurately1.

More specialized catheter designs are also in use today, including dual- and even triple-lumen catheters. One of the more well known of these catheters is the Hickman catheter, a central venous catheter commonly used as an alternative to arteriovenous fistula for the administration of chemotherapy or parenteral nutrition introduced in the 1970s. There have been many innovations since then, including kink resistant catheters and others.

Impact of Catheter Innovation:

From its humble origins in Dr. Seldinger’s work of vascular access to Dr. Dotter’s groundbreaking angioplasty, the catheter has been a cornerstone in interventional radiology. Initial designs were used primarily for angiography but as the field of interventional radiology took, advances were made in the technology used. Dr. Dotter and Bill Cook created the stiff coaxial Teflon catheter which then led to Dr. Judkins using a modified catheter “bullet nose” model which led to pre-shaped catheters. Present day catheters offer a pre-shaped curve to aid in tracking off a vessel1.

Initially clots were treated with drug therapy to activate the process of fibrinolysis but mechanical thrombectomy gave rise to an improved approach. Since 2009 guidelines were released by SIR

for endovascular stroke several studies have shown intra-arterial catheter-directed treatment offers improved outcomes. Microcatheters helped to revolutionize the process of clot removal in stroke patients. The procedure requires placing a microcatheter through the guiding catheter and once the microcatheter is distal to the clot a snare is deployed. Using this procedure a clot can be retrieved leading to regeneration of blood flow to poorly perfused areas. Treatment of ischemic stroke due to thrombus formation can be managed via innovative catheter technology in the field of IR.

Material and composition leads to an interesting review of catheter versatility. With the advancement of research, the field went from Dotter’s Teflon catheter to devices of various shapes and sizes. The wide selection offers interventional radiologists to perform vast procedures ranging from PAD interventions to even managing neurological procedures.

Hydrophilic catheters allow easier glide in the lumen of a vessel and reduced friction thus lowering the risk of injury. Moreover, the coating allows for successful tracking of more tortuous anatomy that is typically seen in the cerebral vasculature7.

Another interesting innovation of key interest is lithotripsy. A catheter partnered with a balloon and electrical emission unit is passed through a calcification. Once delivered across, electrical discharge disrupts a calcified lesion leading to its removal from vessels. Reports in literature show that this technology can be beneficial in treating highly stenotic lesions in patients and lead to improved procedures due to catheter selection1.

Atherectomy catheters are used in CLI (critical limb ischemia) interventions with great success. Removal of atherosclerosis in arterial walls helps to restore blood flow to the lower limb via the use of aspiration, rotational motion, or laser based approaches leading to removal. The usage of these catheter devices offers an alternative to stent implantation due to biomechanical stress1,7.

In conclusion, the advancement of the catheter ushered in interventional radiology’s diversity. The innovative spirit at the core of the field inspired improvements on existing devices and only time can tell what the next steps will be. Interventional radiologists provide a unique perspective to endovascular minimally invasive procedures as we are well trained in imaging, technical skills, and clinical experts in disease management. We all look forward to the next frontier!


1. Taslakian B, Ingber R, Aaltonen E, Horn J, Hickey R. Interventional Radiology Suite: A Primer for Trainees. J Clin Med. 2019;8(9).

2. Abele JE. Society of Interventional Radiology History: John E. Abele’s Perspective. J Vasc Interv Radiol. 2018;29(5):729-730.

3. Steinberger JD. Innovation in Interventional Radiology. Tech Vasc Interv  2017;20(2):83.

4. Tang Z, Jia A, Li L, Li C. [Brief history of interventional radiology]. Zhonghua Yi Shi Za Zhi. 2014;44(3):158-165.

5. Strunk H, Marinova M. Transjugular Intrahepatic Portosystemic Shunt (TIPS): Pathophysiologic Basics, Actual Indications and Results with Review of the Literature. 2018;190(8):701-711.

6. Northcutt BG, Shah AA, Sheu YR, Carmi L. Wires, Catheters, and More: A Primer for Residents and Fellows Entering Interventional Radiology: Resident and Fellow Education Feature. 2015;35(5):1621-1622.

7. Murphy TP, Soares GM. The evolution of interventional radiology. Semin Intervent Radiol. 2005;22(1):6-9.

Weightless Lead
September 25, 2020

Written By: Jacob Poliskey

This is the story of an inventor who built a lead shield that hangs from overhead. It is a story of someone working with limited resources and little help, motivated by necessity, and achieving unconventional success. And it all started in the interventional suite when Dr. Chet Rees developed back pain. 

This Short Story is based on an August 2020 interview between the author and Dr. Chet Rees MD, the inventor of Zero Gravity Lead Shielding1. The Society of Interventional Radiology does not promote this product and has no financial disclosures.  

Dr. Chet Rees, a practicing interventional radiologist, always had ideas for possibly useful medical devices, but spent over two decades without finding the time to develop them. Projects would stall in the early fabrication stage.  He was raising kids, busy at work with a full clinical load and a body of manuscript publications and scientific presentations, and hesitant to spend a lot of personal money on outside projects. This went on for years, leaving little more than a lot of ideas scratched out on paper and a pile of junk at his house.  

Figure 1: Dr. Rees at work in his floating lead shield.

In his case, necessity was the mother of invention. While in his late 40s, he developed severe back pain. He was concerned, as a long career was ahead of him, and the thought of working through debilitating back pain was not appealing. 

“What if this gets worse and I can’t deal with this?” he thought. He contemplated retraining into diagnostic imaging, but wasn’t met with warm and fuzzy feelings in his group; he had been out of reading images for a long time.  

Then he started to think about the lead that hung over his body for hours at a time. 

“Why do we have to wear this lead? It’s heavy but not very protective.” A long time went by, and Dr. Rees thought a lot about it—about all the radiation coming through, hitting his face and his head, and about his back pain. 

So Dr. Rees set out—to invent something new? No. He began to search for a product that solved his needs. But, in his own words, “I got nowhere. There was nothing,” and that was when he figured he needed to make something himself. 

He started brainstorming contraptions. He didn’t want something on the floor getting underfoot. It had to be a shield suspended in front of you that you’d walk into. It had to move freely, up and down, leaning forward where you didn’t notice it too much. His first epiphany happened when he discovered commercial instruments called balancers. These were used to pick up heavy assembly line tools with ease, such as a two-hundred pound power drill. Then he started looking at cranes to move the shield around effortlessly. How you could adapt a crane to go into the suite? 

Looking at these different components, Dr. Rees started building in his garage. A short time later, he had built rails into his ceiling and integrated a boom with suspenders, fasteners, and an apron hanging from a frame. The frame had a face-shield mounted on the apron, and the apron itself was extra thick, covering his eyes and body better than any wrap-around lead skirt ever could.  

With a workable prototype in hand, he did what anybody suffering from back pain would do: bring it directly to work! “I did not begin this with the intention of making money at all. As things progressed, I applied for a provisional patent before the ability to do so would have been lost, but my main goal remained to bring it into the hospital,” where he could put it in the room where he did most of his procedures.  

What happened when he asked to put it into the interventional radiology suite? “Everybody I talked to shot me down. Nobody was candid,” Dr. Rees said, adding that they just didn’t answer him or would stop talking to him about it. 

Eventually he was uncomfortably referred to the hospital’s lawyers. 

“No way can we do this,” said the lawyers. 

“Why not?” countered Dr. Rees. 

“Because we can’t just bring a doctor’s contraption in here.” 

“It’s been done in the past!” 

“Times are changing.” 

“You bring new equipment in here all the time!” 

“Yeah, but that’s from real companies.” 

“I have a company!” — the solo Dr. Rees had LLC status. 

“Yeah…but not really. You’re not the kind of company we’re interested in.” 

Figure 2: An early, rejected prototype.

All this work, and nothing that he or anybody else could use. But this rejection was a pivotal moment and a blessing in disguise. This was when Dr. Rees had the realization, “I can’t use this to prolong my career unless it becomes a marketable, profitable product.”  

Later reflecting on the episode, he said, “The hospital was right to not let me put my own device in there. They knew what they were doing—liability issues and so on. I don’t fault them at all.” 

He set out to make his invention marketable. He showed it around.  He made movies about it. Some people thought it was fantastic. Others thought it was boxy: it looked too industrial to fit in a hospital, much less a sterile procedure room. The last complaint was once you put the apron on, sure, it moved perfectly—up and down and around—but you were stuck. Because the boom was only so long, you couldn’t walk out of the room without breaking sterile scrub. 

Dr. Rees set out to fix these major hurdles, enabling the user to enter and exit the lead shield seamlessly without any change in the sterile field. “Sometimes when you invent something,” Dr. Rees clearly instructs, “you’re not doing one invention, you’re inventing a hundred. Every week you need a new invention to get around a problem.” 

The eureka moment solving this must-have arrived one day: by outfitting a lightweight vest, worn like a shirt under the sterile drape, with a magnet that engaged the floating lead shield, “you can engage it sterile and leave it sterile…So easy on, easy off.” He drew it up and made prototypes.  

Figure 3: Engaging the lead shield with a magnet lets a person enter and exit without any change in the sterile field.

“It worked fabulously.” 

The last key step was making it look pretty. Dr. Rees was skiing one day when he noticed that the new ski lift he was riding had a curved arm holding up the chair. Thinking that the chairlift looked stylish, he copied the design by bending a metal rod himself and carefully hanging his lead shield on it. A new paint job finished the affair.  

A video of the floating lead shield in action was a hit. Finally. 

Two years later, after licensing the device to an industrial partner, it started selling everywhere. In Dr. Rees’ words, “A lot of people are very thankful…People who were in boats like mine [with my back pain] or [who were] very concerned about the radiation…Badge readings have plummeted down to near nothing and they feel safer and more comfortable. People can do more cases and do not have to retire early. It’s very gratifying to hear how it’s affected lives.” 

With the device installed in his own lab, most of Dr. Rees’ back pain resolved itself over the last two to three years. True success.


1. Rees, C. (2020, August 6). Personal interview.

All images used with permission and courtesy of Dr. Chet Rees