Michael Bettmann, MD, FACR, FSIR, FAHA
Interventional radiology (IR) faces major challenges, as it has throughout its relatively
brief history. This opinion piece will subjectively review the evolution of IR and
address some of the major opportunities and challenges it faces. The exact starting
point of IR, or image-guided interventional procedures, is not clear, but the field
evolved from and is based on several specific advances. Access to the vascular system,
for diagnostic purposes, was a widespread goal in medicine from the early 20th century,
one that became clear not very many years after the first description of X-rays and
their use by W.C. Roentgen in 1895. In the 1920s and 1930s, various individuals attempted,
with varying degrees of success, to image the heart and the vessels of the brain,
and to derive physiologic information from the cardiovascular system. These attempts
were limited by complex vascular access, limited imaging capability, and relatively
toxic contrast agents. Access to the arteries and veins was difficult and limited
until Sven Ivor Seldinger, then a resident physician in radiology in Sweden, developed
a method of accessing the femoral artery without a cut-down by using a hollow-bore
needle with a removable trocar and a threadable guiding wire. This was published in
1953.[1] Interestingly, Dr. Seldinger did not try to patent his technique and made no money
from it. He spent his entire subsequent career as a general radiologist in a relatively
rural practice in Sweden. Like many but not all major advances in IR, Seldinger's
invention was based on the work of several prior investigators—it was a major step
forward, but not a leap. Due to this technical advance, angiography became widely
available and widely utilized, but for diagnostic purposes, but soon investigators
began using angiography for information beyond the anatomical. In the 1960s, Herbert
L. Abrams, at Stanford University in California, following Fellowship training in
cardiovascular angiography in Sweden, described the use of epinephrine intra-arterially
during renal angiography. He demonstrated that normal blood vessels contracted following
epinephrine infusion, but the arteries in renal cell carcinomas (RCCs) did not, allowing
preoperative identification of RCC.[2] Subsequently, others, notably Stanley Baum, a trainee of Dr. Abrams, used epinephrine
to induce spasm in gastrointestinal tract arteries that were actively bleeding, leading
to nonoperative control.[3] Simultaneously, others, most importantly and creatively Charles Dotter, realized
that with relatively safe and usable arterial access, the catheter could serve as
a therapeutic device. He pioneered dilatation of atherosclerotic arteries using progressively
larger dilators passed over a guidewire through the arterial narrowing or occlusion.[4] Dotter also conceptualized and pioneered the infusion of a “clot busting” drug through
a catheter, to treat thrombotic or embolic occlusions, and with collaborators, also
conceptualized the use of a metallic device, a stent, to help keep narrowed or occluded
arteries open. Many investigators began using various techniques to try to open partially
or completely occluded arteries starting in the late 1960s. After hearing a presentation
by Charles Dotter in Germany in the late 1960s, a young German vascular medicine doctor
working in Switzerland, Andreas Gruentzig, developed an inflatable balloon on a catheter
with a fixed maximum diameter that could be inserted over a guidewire and used to
unblock arteries. He then investigated this approach, first in animal models and then
in high-quality clinical studies in lower extremity arteries and then, in 1977, in
human coronary arteries. These progressive studies, again based on the work of many
angiographers, were the start of the widespread use of percutaneous transluminal angioplasty
(PTA). PTA not only revolutionized the treatment of atherosclerosis clinically but
also led to remarkable research advances in understanding and treating atherosclerosis
and in vascular biology.
Simultaneously, radiologists with expertise in areas other than cardiovascular disease
developed a large variety of image-guided, minimally invasive interventions. These
include abdominal, thoracic, musculoskeletal, and neurologic procedures, such as biopsies,
gastrostomies, nephrostomies, and joint injections and spine interventions. As with
vascular interventions, these advances in diagnosis and treatment have evolved broadly
and even dramatically over time with new tools, new techniques, and new indications.
They are the result of the intelligence, effort, and creativity of numerous physicians
from many different countries. Although not all, many of these advances have been
the result of work by radiologists.
IR, however, is not a product of technical advances alone. Interestingly, until the
early 1970s, there was relatively little understanding about the function of the blood
vessel wall. Heart attacks, for example, were thought to usually be the result of
gradual progressive narrowing of a coronary artery, until the lumen reached a tipping
point and closed off completely. With advances in cardiac surgery and with the advent
of angioplasty, the study of the arterial wall burgeoned, and it was progressively
understood that the arterial wall is a complex biologic organ that interacts in many
ways with blood and with other factors. Much of this scientific research that has
formed the basis for the striking advances in cardiovascular care came from and through
cardiology. IR remained largely focused on technology rather than basic science. For
various reasons, some related to factors such as the prevalence of heart attacks as
compared with the prevalence of symptomatic lower extremity arterial disease, cardiologists
organized many large prospective randomized studies of various treatments and techniques.
These in turn stimulated a lot of basic research. As a smaller field with less direct
patient control, IR overall was less productive in basic science research and organized
few large clinical trials. Some argue that IR made up for this with creativity and
entrepreneurship, as manifest by the expansion of IR into many organs and diseases.
Perhaps most notably, interventional radiologists have expanded the use of minimally
invasive therapy into oncology in very important, impactful ways. IR has also come
to play a major role in the care of patients with end-stage renal disease, and into
the treatment of venous diseases, including both acute conditions such as deep venous
thrombosis and pulmonary emboli, and chronic problems including varicosities and venous
stasis disease. Many of these advances have been related to the development of new
technology, such as microcatheters, infusion catheters, implantable catheters, and
occlusion materials. There have also been important advances based on the adaptation
of medications for use with minimally invasive therapy, including older materials
such as Lipiodol and newer chemotherapeutic agents.
IR is a relatively young specialty and has continued to evolve based on clinical opportunities
and needs, and on creativity, energy, and enthusiasm. The breadth and depth of IR
work is impressive, and has led to major advances in patient care. IR has, however,
been limited in its acceptance and impact for several reasons. One, obviously, is
our reliance on advanced and expensive technology: we require and rely on high-quality
imaging equipment. This ideally is not just an angiographic suite with a dedicated,
advanced C-arm, staffed by trained doctors, technicians, and nurses, but also or sometimes
alternatively a rapid multislice computed tomography, similarly staffed. Ultrasound
is of tremendous use and importance for IR procedures and adds cost and the need for
expertise. Also, very importantly, IR for the most part depends on collaboration and
on referrals from other physicians and providers. This leads to a conundrum. IR is
based on the delivery of minimally invasive, image-guided treatment. Other specialties
are based on organ systems or broad disease categories. Patient flow and referral
patterns are largely based on the latter, not primarily on the specific technique
used for treatment. Unlike for cardiologists or neurosurgeons, patients are most often
still sent to IR not for consultation but rather for specific procedures. This has
led to considerable efforts in some regions to make IR a specialty separate from diagnostic
radiology, with dedicated clinical training and facilities for evaluating patients
and deciding the best options.
In the minds of interventional radiologists, the advantages of using minimally invasive,
image-guided treatments are that they tend to be safer and probably usually less expensive
than the alternatives. We as interventional radiologists believe that both safety
and overall outcomes are improved with expertise that results from our training and
experience; procedures performed by well-trained, experienced interventional radiologists
with expertise in both imaging and in interventions are better for patients than if
performed by other specialists. Conversely, we as interventionalists learned by doing,
as other specialties—for example, vascular surgeons or urologists or nephrologists—may
be doing over the last decade or two. IR has been responding to challenges—“turf battles”—since
its inception. Dealing with this is difficult, as there are separate areas of expertise
that justify arguments for control of various procedures by different specialties.
For example, regarding peripheral arterial disease, vascular surgeons argue that they
have superior understanding of the natural history and treatments of the disease and
of the patients. Cardiologists argue that they have a better understanding of the
natural history of cardiovascular disease and the treatment options, and follow the
patients over time, in addition to having expertise with highly technical cardiac
interventions. Similar concerns exist with other specialists, including gastroenterologists
and sometimes even general surgeons and neurologists.
Over the last few decades, IR has responded to such challenges in part by changing
the specialty to a clinically independent one, and in part by developing new types
of procedures that other specialties either are not interested in performing or are
less capable of trying. Examples include much of what has become interventional oncology
and, perhaps to a lesser extent, treatment of chronic venous disease. The future of
minimally invasive, image-guided therapy is bright because of its safety and efficacy
in many areas, but whether or not IR as a subspecialty or an independent specialty
will thrive remains an open question.
There is, I believe, no question that IR will continue, but for the specialty to truly
thrive will require some clear progress. We believe that what we do, for example,
transarterial chemoembolization and ablative therapy for liver malignancies, is safer,
less expensive, and at least as effective as alternatives. Despite experience now
of several decades, studies to support this are still limited. Such studies do exist
to some extent, but they tend to be relatively small and, in many cases, are not as
methodologically strong as they could be. To do such studies requires a commitment
to not only procedures that we believe in but a commitment to high-quality clinical
science. This remains an important goal for IR. Too many articles in IR journals conclude
with phrases such as “further investigations are needed...”
Second, IR cannot exist alone. It is imperative that we strive to achieve and maintain
close working relationships with other specialties, perhaps most importantly ones
such as vascular medicine, pulmonology, general practice, and oncology, specialties
that are not particularly procedure-oriented. Finally, we need to be true clinicians.
This too presents a conundrum. Are we imagers or proceduralists? The answer, obviously,
is that we are both, and this makes life complex and difficult. All we do is based
on imaging, so we need to be expert diagnostic radiologists. To help the specialty
of IR grow and thrive, however, we also need to be true clinicians. We need to follow
patients in clinics and admit and follow them as needed-in collaboration.
Other specialties have learned to meet these challenges, in various ways. Many do
this through subspecialization, and I believe that this is the future of IR. General
surgeons are clinicians but also technicians with areas of special expertise (thoracic,
gastroenterologic, trauma). We as IR physicians, individually and as a specialty,
must develop and support expertise in three broad areas:
-
Expertise in imaging and interventional techniques and technology
-
Longitudinal (and collaborative) clinical care
-
High-quality research
We've done well in the first, and cannot abandon it. We have made progress in the
second but this must remain a focus. We have challenges in the third; addressing them
is important, perhaps crucial for the future success of IR.
