Jack Cerne, M.D.

In 1960, magnetic resonance imaging (MRI) characterized flow velocities of sea water with a precision of 10-8 centimeters per second(1). When applied to human blood, flow-sensitive MRI can detect a variety of flow properties characteristic of pathological change.

Flow-sensitive MRI protocols have recently evolved from “2D phase contrast” to “4D flow.” 2D phase contrast had the capability to characterize through-plane or in-plane flow measurements, secondary to one-way velocity encoding. 4D flow, however, can characterize flow properties within a 3D volumetric region, secondary to three-way velocity encoding. 4D flow images can be interrogated with a posteriori analyses and yield detailed information, such as vorticity(2), wall shear stress (WSS)(3), and turbulent kinetic energy(4).

Through applying 4D flow imaging, interventional radiologists may be able to improve the efficacy of their neurovascular, lymphatic, and hepatic interventions.

Pathology related to the neuro-vasculature often presents in high acuity settings. It would be valuable if aneurysm rupture or progression could be predicted by 4D flow-derived measurements, such as WSS. Several studies have already shown that correlations exist between intra-aneurysmal flow and WSS with aneurysm characteristics.

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Arteriovenous malformations (AVMs) represent another opportunity for pre-intervention imaging. It has been suggested that quantitative 4D flow can identify AVM tributary arteries with the highest flow rates. This may enable more successful targeted-embolization treatment of AVMs, prior to surgical resection(5).

4D flow also has potential application, after neurovascular interventions. Flow-diverter stents are currently used to treat sidewall intracranial aneurysms. Despite low velocities within these stents, a flow change index (proportional velocity reduction ratio) was contrived(6). Indices, such as this imply potential for the clinical implementation of 4D flow MRI in post-procedure monitoring, despite metallic stents and low-flow properties in this setting.

Properties of lymph fluid (few cells, clear fluid) and the lymph system itself (variable presence of fluid within vessels) present challenges for visualization. Although procedures, such as thoracic duct and intrahepatic lymphatic duct embolization have been reported, imaging challenges limit the role of the interventionalist in patients with lymphatic disorders.

Lymphatic vessels lie deep, below superficial lymphatic networks, and actively contract via unknown mechanisms. Because 4D flow can quantify flow patterns in volumetric regions of interest, it may hold value in better understanding the interrelatedness of venous, arterial, and lymphatic flows as they relate to disease. Several animal studies have investigated ways that lymph flow relates to tissue pressures(7,8). Dynamic 4D contrast-enhanced magnetic resonance lymphangiography has been shown to demonstrate the time course of contrast agent flow up the central lymphatic ducts(9) and doppler optical coherence tomography has been shown to depict lymph velocity at high temporal resolution(10). 4D flow may enhance our understanding (and visualization) of the lymphatic system.

Portal blood flow has also been studied with 4D flow MRI. Flow volumes were shown to significantly increase in the superior mesenteric vein and portal vein (PV) after transjugular intrahepatic portosystemic shunt (TIPS) placement. In this same cohort, flow differences were seen in the TIPS to PV flow ratio between the six patients with resolved ascites at two and 12 weeks after TIPS (0.8 and 0.9, respectively) and the one patient with refractory ascites (4.6 and 4.2, respectively)(11). Patency and stenosis evaluation following TIPS placement(12)and following PV stent placement(13) represent additional opportunities for 4D flow analysis of the portal vasculature.

In conclusion, 4D flow MRI provides clinicians with advanced quantifiable measures of blood flow. Although the technology is in its early stages, and more applications are being realized, post- and pre- intervention 4D flow acquisitions appear capable of providing clinicians with valuable insight. Pre-procedural 4D flow MRI may improve understanding (and disease screening) in the vascular and lymphatic systems. Post-procedural monitoring similarly appears to be a useful application of 4D flow MRI, especially in the neuro- and portal- vasculature.

According to Charles Dotter, M.D., “If a plumber can do it to pipes, we can do it to blood vessels”. Rerouting and restoring blood flow is the concept behind much of an interventional radiologist’s work. Delicate blood vessels, however, are not steel pipes. If we can better understand blood flow, we can better treat patients. Instead of simply sea(ing) water move, we can now “sea” blood move. Let’s make the most of this remarkable ability and continue to push interventional radiology forward.

Follow Editorial Board member Jack Cerne, M.D., on Twitter

1. Hahn EL. Detection of sea-water motion by nuclear precession. J Geophys Res 1896-1977. 1960;65(2):776–7.

2. Schäfer M, Humphries S, Stenmark KR, Kheyfets VO, Buckner JK, Hunter KS, et al. 4D-flow cardiac magnetic resonance-derived vorticity is sensitive marker of left ventricular diastolic dysfunction in patients with mild-to-moderate chronic obstructive pulmonary disease. Eur Heart J Cardiovasc Imaging. 2018 Apr 1;19(4):415–24.

3. Szajer J, Ho-Shon K. A comparison of 4D flow MRI-derived wall shear stress with computational fluid dynamics methods for intracranial aneurysms and carotid bifurcations - A review. Magn Reson Imaging. 2018 May;48:62–9.

4. Binter C, Gotschy A, Sündermann SH, Frank M, Tanner FC, Lüscher TF, et al. Turbulent Kinetic Energy Assessed by Multipoint 4-Dimensional Flow Magnetic Resonance Imaging Provides Additional Information Relative to Echocardiography for the Determination of Aortic Stenosis Severity. Circ Cardiovasc Imaging. 2017 Jun;10(6):e005486.

5. Schnell S, Wu C, Ansari SA. 4D MRI flow examinations in cerebral and extracerebral vessels. Ready for clinical routine? Curr Opin Neurol. 2016 Aug;29(4):419–28.

6. Pereira VM, Brina O, Delattre BMA, Ouared R, Bouillot P, Erceg G, et al. Assessment of intra-aneurysmal flow modification after flow diverter stent placement with four-dimensional flow MRI: a feasibility study. J NeuroInterventional Surg. 2015 Dec 1;7(12):913–9.

7. Swartz MA, Kaipainen A, Netti PA, Brekken C, Boucher Y, Grodzinsky AJ, et al. Mechanics of interstitial-lymphatic fluid transport: theoretical foundation and experimental validation. J Biomech. 1999 Dec;32(12):1297–307.

8. Leu AJ, Berk DA, Lymboussaki A, Alitalo K, Jain RK. Absence of functional lymphatics within a murine sarcoma: a molecular and functional evaluation. Cancer Res. 2000 Aug 15;60(16):4324–7.

9. Dori Y, Zviman MM, Itkin M. Dynamic Contrast-enhanced MR Lymphangiography: Feasibility Study in Swine. Radiology. 2014 Nov 1;273(2):410–6.

10. Blatter C, Meijer EFJ, Nam AS, Jones D, Bouma BE, Padera TP, et al. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography. Sci Rep. 2016 Jul 5;6(1):29035.

11. Bannas P, Roldán-Alzate A, Johnson KM, Woods MA, Ozkan O, Motosugi U, et al. Longitudinal Monitoring of Hepatic Blood Flow before and after TIPSby Using 4D-Flow MR Imaging. Radiology. 2016 Nov 1;281(2):574–82.

12. Owen JW, Saad NE, Foster G, Fowler KJ. The Feasibility of Using Volumetric Phase-Contrast MR Imaging (4D Flow) to Assess for Transjugular Intrahepatic Portosystemic Shunt Dysfunction. J Vasc Interv Radiol. 2018 Dec 1;29(12):1717–24.

13. Hyodo R, Takehara Y, Mizuno T, Ichikawa K, Ogura Y, Naganawa S. Portal Vein Stenosis Following Liver Transplantation Hemodynamically Assessed with 4D-flow MRI before and after Portal Vein Stenting. Magn Reson Med Sci. 2020;advpub.

Articles

Better understanding of blood flow means better treatment for patients.

4D Flow Applications to Interventional Radiology

Physicians say there is a simple way to be successful in medicine: be 

. You will be successful if you are available, affable, and able.

But what is success? Career success has two components: intrinsic success and extrinsic success. Intrinsic success is one’s subjective reactions to their work (i.e., job satisfaction). Extrinsic success is an objective measure, easily observable to others, such as a promotion(1–3).

radiologists deliver the best patient care. Common sense and research findings remind us that these three principles aren’t trivial adjectives. They are what every patient wants. They are what every colleague wants. And they are what you want… if you want to be successful.

An available radiologist is prepared to respond in emergent situations.

          Colleagues want? [x] Yes [ ] No

Availability is also related to the “want it” factor, necessary to accomplish career success. If you make it known that you are someone available for additional responsibility, and that you aspire for more from your job and company, you will be on a trajectory towards promotion(4). Promotion (i.e., extrinsic success) is accomplished by “the available” radiologist. Being available to teach, conduct research, and contribute administratively is how a radiologist gets promoted(5).

Purely reading the Barco, and being unavailable, is not a way to accomplish extrinsic success in academic medicine. Unfortunately, blog-post writing may be the definition of over-availability, especially if you are an aspiring academic radiologist. But blogging DOES fit the mold for intrinsic success, and “job satisfaction,” as known by yours truly.

An affable radiologist is collegial and professional in interactions.

Someone who is affable is good-natured and easy to talk to. An affable person is friendly, pleasant, and social. Extrinsic success is more easily accomplished by affable personalities: people like working with affable people; affable people do better in interviews; people want to help affable people. Affability is part of the hidden curriculum of life.

Although it is not formally taught in medical school, students quickly learn the importance of being pleasant during the clinical years of medical school. The promotion scheme is no different in radiology. People may gripe about the devalued sense of meritocracy. But there is merit, too, in treating the people around you right and making your colleagues happy to come in to work each day. Radiology, like everything, is a team-sport.

An able radiologist is accurate in their interpretations.

Able radiologists know their material. They don’t “miss” a finding. They take pride in their ability to produce quality reports; they are conscientious. Conscientiousness is defined as, “the quality of wishing to do one’s work or duty well and thoroughly” (Oxford Languages Dictionary).

Conscientiousness is one of the “big five” traits (among neuroticism, extraversion, openness to experience, and agreeableness). Intrinsic career success (i.e., “job satisfaction”) was significantly correlated with only conscientiousness (r=.40) and general mental ability (r=.30). Regression analyses, however, revealed that only conscientiousness maintained an association with job satisfaction (beta=.34). Extrinsic career success was similarly positively correlated with conscientiousness (r=.41), and maintained significance after regression analysis (beta=.44)(3). Conscientiousness, as a construct, extends to work behavior(6), effective job seeking behavior(7), and retention(8). Conscientious people even live longer(9).

Common sense, correlations, p-values, and regression analyses support the belief that a successful radiologist is an AAA radiologist. The best way for a radiologist to achieve (intrinsic and extrinsic) success is to be available, affable, and able.

An AAA radiologist is a successful radiologist.

          Do you want this to be you? [x] Yes [ ] No

Follow Editorial Board member Jack Cerne, M.D., on Twitter 

1. Predictors for Managers’ Career Mobility, Success, and Satisfaction - Urs E. Gattiker, Laurie Larwood, 1988 [Internet]. [cited 2021 Jun 18]. Available from: https://journals.sagepub.com/doi/10.1177/001872678804100801

2. Judge TA, Cable DM, Boudreau JW, Bretz RD. An Empirical Investigation of the Predictors of Executive Career Success. Pers Psychol. 1995;48(3):485–519.

3. Judge TA, Higgins CA, Thoresen CJ, Barrick MR. The Big Five Personality Traits, General Mental Ability, and Career Success Across the Life Span. Pers Psychol. 1999;52(3):621–52.

4. 10 Traits of Successful People Who Get Promoted [Internet]. The Muse. [cited 2021 Jun 18]. Available from: https://www.themuse.com/advice/10-reasons-some-people-get-ahead-in-their-careers-while-others-dont

5. Chapman T, Carrico C, Vagal AS, Paladin AM. Promotion as a clinician educator in academic radiology departments: guidelines at three major institutions. Acad Radiol. 2012 Jan;19(1):119–24.

6. Hogan J, Ones DS. Conscientiousness and integrity at work. Handb Personal Psychol [Internet]. 1997 [cited 2021 Jun 18]; Available from: https://experts.umn.edu/en/publications/conscientiousness-and-integrity-at-work

7. Wanberg C, Watt J, Rumsey D. Individuals without Jobs: An Empirical Study of Job-Seeking Behavior and Reemployment. J Appl Psychol. 1996 Feb 1;81:76–87.

8. Barrick MR, Mount MK, Strauss JP. Antecedents of involuntary turnover due to a reduction in force. Pers Psychol. 1994;47(3):515–35.

9. Friedman HS, Tucker JS, Schwartz JE, Martin LR, Tomlinson-Keasey C, Wingard DL, et al. Childhood conscientiousness and longevity: health behaviors and cause of death. J Pers Soc Psychol. 1995 Apr;68(4):696–703.

Success in radiology comes with these three characteristics.

AAA Radiology

I arrived at the interventional radiology suite and was greeted by a man with a thick red beard. 

. This patient had metastatic bone lesions to the spine causing him great pain. Radiofrequency ablation was being used as a palliative measure.

I heard a lot about interventional radiology and was very excited. I heard it was a very procedure-oriented field and very innovation-driven. I knew everything about the patient. His history with cancer was humbling. I wrote the various patient details on a piece of paper. I took one last look at my paper, confidently donned gloves, and stepped up to the table. I was excited to get a close-up view and engage for the next 5 hours.

However, the procedure involved a few sticks and a few pokes. It was done in 30 minutes, and the patient was rolled out to the post-procedure bay. In the post-procedure bay, I spent time with the patient. The patient smiled, talked about his puppies, and talked about his wife. He was looking forward to his upcoming Alaskan cruise with his grandchildren.

after having cancer cells melted out of his spine.

My thick red beard is something I am really proud of. I have taken pride in my ability to grow it and groom it. It is the first thing that is on my mind in the morning. 

Do I need to trim it? Do I need to shave it? Do I need to oil it?

 Ever since my cancer was removed, I have been able to cover up the scar with my beard. It is 

Nine years ago, I noticed the mole on my chin begin to change. I scheduled a visit with the dermatologist. The administrative assistant was able to get me in the next day. At the dermatology clinic, the physician looked worried the minute he saw me. He measured my mole, looked at it with a magnifying glass, and performed a biopsy. A week later, I learned I had melanoma. I didn’t know what melanoma was, but I quickly learned that it was a “bad” type of skin cancer. This moment was the beginning of my saga with doctors, medicine, and pain.

I was assigned three doctors in the beginning. I had a blood doctor, a skin doctor, and a surgeon. I was placed on chemotherapy, had monthly full-body skin checks, and had metastases cut out of my liver. I was recently referred to an interventional radiologist by my surgeon because of pain in my back. This was weird to me because I thought radiologists looked at fancy screens all day to “diagnose” rather than “treat.”

I first met the interventional radiologist in the clinic. It wasn’t a busy clinic. And it wasn’t a part of the oncology suite. These differences did not bother me at all. I was in extreme pain. My melanoma had metastasized to my spine. I couldn’t sleep at night, and my medication for pain was not helping. The pain was piercing. It felt like a knife was being stabbed and twisted into my back.

The interventional radiologist told me about the kyphoplasty procedure. Once I heard that this had the chance to help my pain – and did not involve surgery – I did not need to hear anymore. I only cared about a reasonable chance of success and a reasonable risk of complications. The doctor spoke with such confidence and enthusiasm. I was convinced after the first minute.

A week later, I had my kyphoplasty. I remember being wheeled into the procedure bay. When the procedure was finished, I chatted with a nice medical student. He was great.

I have come to understand that perspectives extend deeper than simply calling a beard a 

Interventional radiologists, ultimately, bring their unique 

to medicine. The ability to combine imaging with intervention has resulted in fresh ideas to treat pathology. It is shocking to students and patients alike. Combating diseases through tiny holes in the body is the way of the future, but this future isn’t quite yet realized. Interventional radiology clinics aren’t yet as busy as they can be. Patients still may think that radiologists only deal with the diagnosis perspective of disease. And a medical student may have a rudimentary grasp on a procedure before seeing it because the concept feels like science-fiction.

The formal definition of perspective is, “a particular attitude toward or way of regarding something; a point of view.” (google.com). From my perspective, interventional radiology is a particular attitude or way of regarding illness – a point of approach to treatment.

Apparently, students are beginning to realize that interventional radiology accomplishes amazing tasks in a short amount of time. Patients are beginning to realize that the treatments have high efficacy. And people, such as me, are realizing that perspective is the core beauty of interventional radiology.

A provider’s first-person encounter with the specialty as a patient.

Perspectives on Interventional Radiology

Realizing a need is the first step in the innovation process

, and it is also the most important. It has been said that “a well-characterized need is the DNA of great invention”

. But what is a need? And what does it take to realize a need?

The electronic medical record (EMR), artificial pancreas, and ultraviolet (UV) sterilization reveal the multifaceted nature of healthcare needs and the ability of technology to address these needs. Radiologists are ideally positioned to help teams identify needs given their role in the healthcare system and the influence of technology in their approaches to patient care.

. At the time, reports from the Institute of Medicine stated that one in seven hospitalizations was a result of missing clinical information. Errors related to handwriting and untimely access to patient records also fueled a practice environment conducive to medical errors. There was a need for physicians to communicate effectively and efficiently between each other.

The need to communicate better was realized by the various stakeholders in this process: physicians, pharmacists, and hospital administrators. This big problem led to a big solution: the EMR market size value was $26.8 billion in 2020 and has a $33.41 billion revenue forecast in 2025

According to the Center for Disease Control and Prevention’s 2020 National Diabetes Statistics Report, 1.6 million Americans live with Type 1 diabetes. Of this population, 187,000 are children younger than 20 years

. A 1983 randomized control trial indicated the benefits of intensive glycemic control, citing a reduction in the risk of renal disease by 50 percent, a reduction of retinopathy by 76 percent, and a reduction of neuropathy by 60 percent.

However, these benefits were associated with a three-fold increase in severe hypoglycemia

. Blood glucose monitoring is critical, though difficult. A “need” to maintain euglycemia existed for 1.6 million Americans. Artificial pancreas devices (closed-loop glucose control systems) were subsequently developed and wildly successful. A randomized control trial showed that patients with an artificial pancreas had blood glucose levels between 70 and 180 mg/dL for an additional 2.6 hours, compared to patients treated with a sensor-augmented insulin pump

. There are currently three commercially available hybrid-closed loop insulin delivery devices: Cambridge CamAPS Fx; Medtronic 670G; Tandem/Dexcom Control-IQ

Healthcare-associated infections (HAIs) arise in 1 out of 25 patients

. This amounts to more than 1 million annual HAIs in the United States and a multi-billion dollar impact to the healthcare system

. In 2018, a study showed that UV light can reduce active microbial burden more effectively than manual-chemical disinfection (92 percent-to-97.7 percent reduction vs 52.8 percent-to-90.9 percent reduction)

. Devices to sterilize hospital fomites have since skyrocketed, and many hospitals now utilize UV rays in the cleaning of patient rooms. Pulsed Xenon UV devices and Mercury UV-C are additional technologies being investigated as ways to clean hospital equipment with even higher efficacy

Healthcare is all about the patient. But, we need to remember that the care of the patient happens through the EMR on computer screens, at home through patient self-monitoring, and in the hospital through clean hospital equipment.

Imagine the position of the radiologist: a physician who “sees” hundreds of patients each day, corresponds with dozens of departments, and works with computers. The radiology reading room is a front where innovation opportunities abound. The objective is simple for the radiologist: to be as efficient and as accurate as possible. Despite these simple objectives, the specific “need” for innovation in radiology is hard to assess for someone not in the field. I am not a radiologist, but I imagine the answers to these questions hold the key to innovation for improvements in patient care on the radiology front. 

What bothers me? What is my source of mistakes? What is easy? What is hard?

Through communicating these needs to computer programmers, engineers, and data scientists, radiologists can catalyze healthcare innovation in a way that is most helpful to them and, therefore, most helpful to the patient.

With a creative mind and the drive to run with an idea, a radiologist can contribute to healthcare innovations. Although radiologists may love PACS more than the EMR, Gray measurements more than glucose measurements, and darkness more than UV light, the innovations of the past show that there is immense potential to help more patients than simply the ones who present on the Barco screen.

And I believe the way to best capitalize on this potential is to let the needs be known: let’s get radiologists on multidisciplinary innovation teams to catalyze healthcare improvements.

Jack Cerne, M.D., is a clinical research associate in cardiovascular MRI at Northwestern University.

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2. Tj B, Cq K, Db C, et al. Outcomes from a postgraduate biomedical technology innovation training program: the first 12 years of Stanford Biodesign. Annals of biomedical engineering. doi:10.1007/s10439-013-0761-2

3. wiley_admin. EMR: The Progress to 100% Electronic Medical Records. The University of Scranton Online. Published September 17, 2013. Accessed December 1, 2020. https://elearning.scranton.edu/resource/health-human-services/emr_the-progress-to-100-percent-electronic-medical-records

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5. More People Being Diagnosed with Type 1 Diabetes. JDRF. Published February 18, 2020. Accessed December 2, 2020. https://www.jdrf.org/blog/2020/02/18/more-people-being-diagnosed-type-1-diabetes/

6. Cowie CC. Diabetes Diagnosis and Control: Missed Opportunities to Improve Health: The 2018 Kelly West Award Lecture. 

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7. Brown SA, Kovatchev BP, Raghinaru D, et al. Six-Month Randomized, Multicenter Trial of Closed-Loop Control in Type 1 Diabetes. 

. 2019;381(18):1707-1717. doi:10.1056/NEJMoa1907863

8. Automated Insulin Delivery. diaTribe. Published December 2, 2014. Accessed December 2, 2020. https://diatribe.org/automated-insulin-delivery

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10. Armellino D, Walsh TJ, Petraitis V, Kowalski W. Assessment of focused multivector ultraviolet disinfection withshadowless delivery using 5-point multisided sampling ofpatientcare equipment without manual-chemical disinfection. 

. 2019;47(4):409-414. doi:10.1016/j.ajic.2018.09.019

11. Portable Ultraviolet Light Surface-Disinfecting Devices for Prevention of Hospital-Acquired Infections: A Health Technology Assessment. 

Radiologists are well positioned – and have a responsibility – to help teams identify uses for technology in patient care.

The Needs of Innovation: Reflection and Collaboration

Imagine a motorcycle rider crashes his bike on his way to work. He hits his head on the road. He is taken to the hospital, but the CT scanner is broken. The patient feels fine and leaves the hospital. Later he becomes obtunded and passes away. If access to a CT scanner was available, the epidural bleed would have been seen. And, his life would have been saved.

The World Health Organization (WHO) estimates that two-thirds of the world’s population, such as this patient, lacks access to basic radiology care. Interventional radiology is even more inaccessible, and the influence this field can have on patient care is just as remarkable. Interventional radiology is challenging to implement in resource-limited settings because of difficulty maintaining and acquiring radiographic equipment, as well as a dearth of trained practitioners. Fortunately, these are not insurmountable challenges. Through adaptation and education, interventional radiologists can bring their services to populations throughout the world.

The first challenge is physical capital. Interventional radiology relies on equipment that is expensive to purchase and expensive to maintain. A CT scanner can cost up to $2.5 million, and an MRI scanner can cost up to $3 million. The average cost of an angiography system is $1.5 million. The WHO estimates that donations account for 80 percent of the medical equipment in developing countries.

When equipment is acquired through a donation, it is often misallocated in resource-limited settings

. A clinic in rural Africa may receive a CT scanner. However, if the CT scanner malfunctions, there may be no nearby technician to fix the machine. The CT scanner will quickly become dormant. A reliable power grid and climate-controlled settings are also uncommon, yet essential, for interventional radiology equipment. Fluoroscopy, CT, angiography, MRI, nuclear medicine, and advanced ultrasound equipment are often found in “medical equipment graveyards.” While 1 percent of medical equipment is out-of-service in high-income countries, 40 percent of medical equipment is out-of-service in low and middle-income countries

Human capital is another challenge that faces the practice of interventional radiology in resource-limited settings. For example, there were fewer than five practicing interventional radiologists in Nigeria in 2019. With a population of 200 million people, supply cannot meet demand

. The training paradigm for interventional radiology in the United States incorporates four years of training in diagnostic imaging. A foundation in image interpretation is essential for the safe practice of interventional radiology.

Unfortunately, diagnostic radiologists and imaging educators are also few in number in resource-limited settings. For instance, prior to RAD-AID, a non-profit organization serving imaging needs worldwide, Guyana had no radiology training program. In the 20 francophone countries in Africa, there are 117 radiologists. Some Asian countries have one radiologist per million population

. To increase the number of interventional radiologists, the number of trained diagnostic radiologists also needs to increase. Though the current number of radiologists is inadequate, continued growth is likely and will promote better access to interventional radiology.

Adapting procedures is one mechanism that can be used to overcome the challenges associated with the practice of resource-limited interventional radiology. When certain equipment is not available, many procedures can still be performed effectively and safely through alternative protocols and techniques. For instance, portal vein embolization through a trans-ileocolic approach has been successfully performed with hysterosalpingography catheters

. Percutaneous nephrostomy using only a trocar catheter is a viable alternative to the typical needle/wire/dilator/catheter combination

. Gastrostomy tube placements and vascular malformation corrections have been successfully performed with ultrasound

. Ethanol ablation of hepatocellular carcinoma has been shown to be an alternative to thermal ablation

. Adaptations to “high cost” interventional radiology procedures indicate hope for the practice of interventional radiology throughout the world. With continued innovation, interventional radiology procedures can be practiced in settings outside of the typical modern procedural suite.

Training initiatives can also aid the spread of interventional radiology to resource limited regions. Through offering webinars and open-access training documents, interventional radiologists can teach basic procedures to providers in remote settings. Simple biopsies and drainages, vascular access, and embolization procedures are excellent opportunities for low-cost, minimally invasive, treatments.

Ultrasound and fluoroscopy are relatively inexpensive, ranging $10,000-to-$200,000 and $20,000-to-$80,000, respectively, and can be used for many procedures

. Though the needs of communities in North America are very different compared to places, such as Sub-Saharan Africa, re-evaluation and assessment of local needs can be met through tailored teachings in more advanced procedures

. Volunteer-based efforts led by non-profit organizations, such as RAD-AID, have focused on developing a global interventional radiology curriculum. Collaborations with Ethiopia, Ghana, Guyana, Kenya, Nigeria, and Vietnam have resulted in regular webinars and workshops. Through volunteerism, there is ample opportunity for interventional radiologists to contribute to efforts such as these initiatives.

The practice of interventional radiology faces several hurdles to becoming a global practice. Through the adaptation of procedures and the education of practitioners, the spread of interventional radiology to resource-limited settings is possible. Interventional radiologists will continue to display ingenuity through creative procedural adaptations and teaching modalities. In the future, maybe a rider will, again, fall from his motorcycle. Not only will he be able to receive high-quality and timely imaging, but he will also be able to receive a high-efficacy percutaneous procedure for treatment: a radiology procedure that has yet to be realized!

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What will it take to bring interventional radiology to these areas?

The Feasibility of Global Interventional Radiology: Opportunities in Resource-Limited Settings

Stroke is the leading cause of disability and the fifth leading cause of death in the United States. Despite the significant morbidity and costs, stroke therapy recommendations have not been well-established until recently, and radiology now plays a central role in the treatment of those patients.

Radiologists are ideally positioned to practice stroke intervention, given their acumen with image interpretation and experience with endovascular therapies. Formerly, the paradigm treatment for ischemic stroke consisted of intravenous thrombolytic therapy, which is easy to administer, typically in the setting of the emergency department. Recently, several randomized clinical trials suggested that endovascular thrombectomy provides superior outcomes.

In particular, the MR CLEAN trial, a multi-center clinical trial involving 233 stroke patients randomized to an endovascular treatment arm, revealed endovascular thrombectomy within six hours after stroke onset was effective and safe. Patients in the endovascular arm achieved improved functional outcomes in 83 percent of cases compared to 19 percent in the medical management arm. Interventional radiologists performed the majority of the thrombectomies in this trial.

CT Predicts Stroke Patients Benefitting From Endovascular Thrombectomy

Four other ongoing trials were terminated early, given the results of the MR CLEAN trial (1). The other four trials (ESCAPE, EXTEND-1A, SWIFT PRIME, REVASCAT), despite premature termination, also demonstrated evidence that significantly better outcomes could be achieved with thrombectomy compared to medical management. Accordingly, the American Hospital Association guidelines changed in 2015, engendering many hospitals to offer this service. The updated guidelines stated a Class 1a recommendation for the use of thrombectomy for anterior circulation large vessel occlusion strokes, up to six hours since the patient was last known well.

Unfortunately, the existing trained radiologist workforce and infrastructure of the healthcare system have not been adequate to meet the demand to deliver safe and timely treatment; high volume practitioners have been necessary to achieve the best clinical outcomes, but eligible patients have been infrequent enough to adequately sustain practice volume.

Specialized stroke care centers, thereby, have been developed for endovascular interventions as a means to funnel patients to high-volume practitioners. Similar models for cardiac ischemia, trauma, and pediatric critical care exist. Despite these efforts, disparity between thrombectomy demand and capable-physician supply still persists. Thrombectomy is currently only available to 2 percent-to-3 percdent of eligible patients in the United States. The current thrombectomy rate is 3 per 100,000 people and is expected to grow to 24 per 100,000 person-years, given the new guidelines (2).

Given these demands, accompanied by the delayed treatment time for transferring patients to designated stroke centers, alternative models have been proposed to train more radiologists to become capable of safely providing these specialized therapies. The traditional training paradigm for diagnostic radiology residents planning to specialize in interventional neuroradiology (INR) entails a neuroradiology fellowship, followed by an INR fellowship. Similarly, in order to practice INR, most interventional radiology residents are required to complete neuroradiology and INR fellowships.

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The Society of Interventional Radiology has championed a new training pathway where proctors train interventional radiologists. This pathway is suggested to be comparable to conventional neurointerventional fellowships and, therefore, serves as an alternative pathway to provide radiologists with the experience necessary to safely perform acute stroke interventions. A proctor needs to have performed 50 acute ischemic stroke cases as a primary operator, with at least two years of practice data with outcomes meeting national standards. Options for learning from a proctor could include one of the following three options (3):

Hands-on training not limited to interventional techniques, but also including workup before and after management for thrombectomy

Full-time training at a different institution, given the unpredictable case rate for stroke care

Travel consultant, where the proctor travels to institution to provide hands-on training

A case study at Johns Hopkins University (JHU) demonstrated success with this model. JHU recruited an INR physician to teach four interventional radiologists how to perform cerebral thrombectomies. The trainees were available for six months, and the INR physician was flown-in by helicopter for each eligible thrombectomy case. Upon completion of training, 35 of the stroke cases were reviewed, and compared to the quality guidelines outlined in the Highly Effective Reperfusion Evaluated in Multiple Endovascular Stroke Trials (HERMES) meta-analysis published in 2016.

JHU 90-day mortality was 14 percent while HERMES was 15.3 percent. Therefore, upon being trained, the interventional radiologists had 90-day mortality ratings similar or better than the current benchmark (4). As demonstrated by the previous case study, and building upon their expertise in imaging and image-guidance, radiologists are able to acquire the skillset necessary to safely perform endovascular treatment in a short timeframe.

In summary, the morbidity and mortality of stroke is a detriment to patients and society, and, until recently, treatment attempts have often been ineffective or limited to a select group of patients. An immense opportunity now exists for radiologists to manage acute stroke patients with endovascular therapy and achieve excellent outcomes for many patients up to six hours after stroke onset.

Currently, the infrastructure of the healthcare system faces challenges in its ability to pair a capable physician and a patient in need. Radiologists are, however, ideally situated to contribute to this treatment revolution and lessen the disparity between the demand and the access for endovascular stroke therapy.

Vadlamudi V. Updates on Endovascular Therapy for Acute Ischemic Stroke. SIR-RFS Webinar. June 5, 2018.

. A population-based incidence of acute large vessel occlusions and thrombectomy eligible patients indicates significant potential for growth of endovascular stroke therapy in the USA. 

Sacks, D, AbuAwad, M, Ahn, S, et al. Society of Interventional Radiology Training Guidelines for Endovascular Stroke Treatment. 

Journal of Vascular and Interventional Radiology

SIR: Stroke treatment training program improves outcomes.

Interventional radiologists are uniquely positioned to practice stroke intervention. 

The Changing Landscape of Interventional Neuroradiology

Interventional Radiology has grown exponentially in recent years. Embolization procedures were first performed in 1970. Three years later, balloon angioplasties were being performed. Then, in the 1980s, complex interventions, such as Transjugular Intrahepatic Portosystemic Shunt (TIPS) placements were introduced

. These therapies are now offered in nearly every hospital. Such growth has been facilitated by advances in technology, combined with the creativity of practitioners. Evolving advances in augmented reality, artificial intelligence (AI), imaging modalities, robotics, and procedural techniques will play a big role in the future and facilitate further exponential growth.

In augmented reality, virtual images can be seen alongside real images. In contrast to virtual reality where the field of vision includes no real images, augmented reality offers the ability to maneuver objects and interact with the real world. This powerful development has wide-ranging applications for image-guided interventions. For example, an interventional radiologist could visualize vital signs within the same field of vision, overlying the patient during a critical intervention. These numbers could potentially appear on command when performing a key step of a procedure or when the radiologist has a concern.

Augmented and Virtual Reality – Radiology at the Center of Medical Technology

Needle placement or a procedure with an image-guided device is another application. For instance, the operator could also view a fused ultrasound image, during simultaneous visualization of needle insertion and ultrasound probe manipulations. Augmented reality can also be used to visualize anatomy underneath procedural drapes to guide an intervention when there is poor sonographic penetration or fluoroscopic guidance is insufficient. For example, a projected 3D hologram, recreated from a pre-programmed CT scan, can help the radiologist identify – and avoid – key structures during a percutaneous intervention, which may otherwise be invisible.

Recent developments in AI represent additional revolutionary opportunities of growth in the current and future practice of image-guided interventions. Utilizing AI, outcomes of interventions can be more accurately and quickly predicted, improving patient outcomes. Machine learning algorithms will be able to augment the interventional radiologist in guiding treatment decisions and selecting patient populations that would benefit most from interventions in areas, such as interventional oncology, where multimodal therapies abound.

Other future applications will include intraprocedural augmentation for the interventional radiologist. AI will enhance image guidance through anatomical recognition, to facilitate interventions and guide the operator through complex anatomy. Lastly, promising applications exist in the treatment of patients requiring time-sensitive interventions. Conditions, such as strokes and pulmonary embolisms, have been described to benefit from AI’s impact on expediting recognition and throughput to improve patient outcomes

Furthermore, continued enhancement of current image-guidance modalities and development of new ones will enhance future procedural practice. Limitations of current imaging modalities in interventional radiology include two-dimensionality and, oftentimes, radiation exposure. One new imaging guidance modality currently being pioneered is Fiber Optic RealShape (FORS)

. This imaging technology utilizes catheters embedded with light sensing technology. Currently, physicians are challenged by tortuous and diseased vasculature, which is difficult to visualize in 2D and often presents technical challenges to operators driving the catheter. Technologies, such as FORS and other evolving modalities, could optimize vascular imaging guidance, drastically decrease the procedural time, and radiation exposure for interventions, drastically increasing the safety for patients and practitioners alike in the future.

Another area with future potential in imaging-guided interventions is robotics, which has already been integrated into many fields of medicine. Oftentimes, in order for robotic systems to flourish in utilization, there must be a proven clinical benefit. For example, the DaVinci Surgical System results in smaller incision sites and higher surgical accuracy. These factors justify the cost.

Robotics have been applied to many endovascular procedures. Uterine artery embolization, cardiac ablation, and aneurysm repair have all been successfully performed with robotic navigation systems. Radiographic procedures are uniquely positioned to benefit from robotics due to added benefits to the operators. The interventionalists can work in a separate room from the procedural suite, thereby shielding them from radiation exposure and musculoskeletal injury from heavy protective aprons. More research, however, is needed to justify the cost of such systems, but it is expected that robotics will become more prominent in interventional suites. It is essential that benefits to the operator safety will not compromise patient outcomes, and quality-control studies continue to be rigorously applied and performed.

Lastly, the scope of practice of interventional radiology itself is expanding, as well. In addition to advancements in existing procedures and techniques, interventional radiologists are developing new procedures to address conditions, such as arthritis, obesity, and benign prostatic hypertrophy. Many of these procedures have been validated in small scale clinical trials. Chronic arthritis pain is being managed through embolization of hyperemic synovial tissue

. The left gastric artery has been embolized to decrease fundus blood flow, thereby restricting growth of ghrelin-producing cells and decreasing appetite

. Radiologists can also treat lower urinary tract symptoms through decreasing the size of the prostate with embolization

. Endovascular approaches continue to be identified as a way to treat conditions formerly managed with invasive surgeries and medication therapies. The future is bright as the value proposition of interventional radiology offering minimally invasive, high-quality, low-complication, cost-effective therapies aligns extremely well with the future of medicine and healthcare.

In summary, advancements in technology will foster improvements in efficiency, efficacy, and safety for interventional radiology and image-guided interventions. The degree of innovation and changing practice patterns will continue to be exponential, alongside exponential growth in technology. Interventional radiologists will be presented with ample opportunity to adapt and invent. This is an exciting challenge, and will mean a brighter future for patients.

Midulla M, Pescatori L, Chevallier O, et al. Future of IR: Emerging Techniques, Looking to the Future…and Learning from the Past. 

Keshava S, Kalva S. Artificial Intelligence in Interventional Radiology. 

Mascini L. Operate Using Live, 3D Image-Guided Navigation of the Inner Body. Innovation Origins: Your Sneak Peak of the Future. October 24, 2019. 

https://innovationorigins.com/operate-using-live-3d-image-guided-navigation-of-the-inner-body/

Balga S, Piechowiak R, Hartman T, et al. Genicular Artery Embolization for the Treatment of Knee Pain Secondary to Osteoarthritis. 

Pirlet C, Ruzsa Z, Costerousse O, et al. Transradial Left Gastric Artery Embolization to Treat Severe Obesity: A Pilot Study. 

Pisco J, Pinheiro L, Bilhim T, et al. Prostatic Arterial Embolization for Benign Prostatic Hyperplasia: Short- and Intermediate-term Results. 

From augmented reality to virtual reality to robotics to new procedural techniques – the future of interventional radiology is bright.