IR Playbook: A Comprehensive Introduction to Interventional Radiology

This textbook offers a comprehensive guide to interventional radiology (IR) for medical students, residents, nurse practitioners, physician assistants, and fellows. IR is constantly evolving to meet the growing demands of patient care by applying cutting-edge technology to minimally invasive image-guided procedures. A dynamic specialty, interventional radiology has gained significant traction and interest in recent years, with combined IR/DR residencies rising to meet the increasing demand. This book addresses this growing need for a reference in IR, allowing students to gain a solid foundation to prepare them for their careers.

The book is divided into two main sections, with many images and key point boxes throughout that offer high-yield pearls along with the specific How To's necessary for practice. The first section is designed to give readers an introduction to IR, including radiation safety, commonly used devices, patient care, and anatomy.The second portion divides into sections covering major body areas, diseases, conditions, and interventions. These chapters cover procedures including pathophysiology, indications for treatment, as well as alternative treatments before delving into interventional therapy. IR Playbook gives medical students, residents, and trainees a full perspective of interventional radiology.

• Language: English
• Publisher: Springer
• Release date: Jun 6, 2018
• ISBN: 9783319713007

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Part IRadiology Basics

© Springer International Publishing AG, part of Springer Nature 2018

Nicole A. Keefe, Ziv J Haskal, Auh Whan Park and John F. Angle (eds.)IR Playbookhttps://doi.org/10.1007/978-3-319-71300-7_1

1. Evolution of IR Training

John A. Kaufman¹  

(1)

Department of Interventional Radiology, Oregon Health & Science University/Dotter Interventional Institute, Portland, OR, USA

John A. Kaufman

Email: [e-mail]

Keywords

Interventional radiologyFellowshipResidencyTraining

The most important individuals in any specialty are its trainees. Although medical students, residents, and fellows often feel that they are at the low end of the professional hierarchy, they are in reality far more valuable than their teachers. Without trainees there is no future. At any given moment, these are the people who have the most potential to make the greatest contributions over time. For this reason, training in interventional radiology (IR) has been a major focus of the specialty since its earliest years and continues to evolve and grow in importance. The purpose of this chapter is to briefly review the history of IR training as the backdrop for the latest step in evolution, the IR residency .

IR was not fully conceptualized or formed at a specific time or place but was gradually defined by many different individuals all over the world. The history of the specialty in the United States is just one of many histories, all equally fascinating and instructive. For the purposes of this chapter, training as it evolved in the United States will be discussed.

The influence of Europe on IR in the United States cannot be understated. Sven Seldinger (of the Karolinska Institutet in Sweden) invented percutaneous catheterization in 1953 [1]. Previous to that Berberich and Hirsch had demonstrated peripheral angiography and venography (1923), Egas Moniz of Portugal had described cerebral angiography (1927), Reynaldo dos Santos performed direct puncture aortography (1929), and Werner Forssmann of Germany catheterized his own heart (1929) [2, 3]. As a result, Europe was an early destination for radiologists seeking training in invasive diagnostic techniques [4].

In the 1960s, training in angiography could be obtained in only a few US centers. Among the first programs were those located at the University of Oregon (Charles Dotter), Stanford University in California (Herbert Abrams), and the University of Minnesota (Kurt Amplatz) [4]. Training was not standardized, and there was no formal regulation or certification. The length of training was also variable, with some programs requiring a 2-year commitment. Most trainees had already completed a diagnostic radiology (DR) residency . The graduates of these programs, as well as individuals originally from Europe, Latin America, and Asia created new training programs in other cities such that by the 1980s the then Society of Cardiovascular and Interventional Radiology (SCVIR , now Society of Interventional Radiology, SIR) recognized the need to develop a standardized curriculum. The SCVIR formed a committee to seek formal recognition of these training programs by the Accreditation Council of Graduate Medical Education (ACGME) [5].

Accreditation for Vascular and Interventional Radiology fellowships first became available from the ACGME in 1991. Eligibility for the fellowship required completion of a diagnostic radiology residency, with a fellowship duration of 1 year in length. Standards for faculty, resources, didactics, and clinical content had to be met in order for a program to receive accreditation. This was a new concept for IR fellowships, which had been used to self-regulation at the program level for many decades. In 1994, the American Board of Medical Specialties (ABMS) recognized Vascular and Interventional Radiology (VIR) as a subspecialty of Diagnostic Radiology, and the American Board of Radiology (ABR) began offering subspecialty certification in VIR by examination. Eligibility for examination was initially open to both interventionalists who had completed an ACGME fellowship and those who had not but was later restricted to graduates of accredited VIR fellowships. As a result, all VIR fellowships became accredited by the ACGME.

The impact of this first step, accreditation, was enormous. There was initially much controversy over the concept of any sort of specialization in diagnostic radiology and subsequently over certification of special competence. The issues of disenfranchisement of diagnostic radiologists performing interventional procedures who were not trained in VIR fellowships and the potential weakening of the structure of diagnostic radiology by differentiated subgroups were of great concern to both interventionalists and non-interventionalists alike. However, the uniformity of training brought by accreditation also solidified the educational community of IR. Without this initial unification, all subsequent changes would have been impossible.

Shortly after the recognition of VIR as a subspecialty, efforts to modify training were already underway. The primary intent of these efforts was to enhance training in non-procedural patient care. By the year 2000, becoming an IR required an internship (PGY 1), diagnostic radiology residency (PGY 2–5), and then a VIR fellowship (PGY 6). Even individuals with great interest in non-procedural care had little direct exposure to patient management during the 4 years between internship and fellowship. As IR practice was increasingly intervention based, with the interventions becoming more complex, the importance of this skill set was anticipated to grow with time.

The first attempt to provide more training in non-procedural patient care was the clinical pathway, proposed by the SIR in 2000 [6]. This 6-year program consisted of 16 months of training in non-radiology patient care specialties, 29 months of DR, 24 months of VIR, and 3 months of research. There was only limited implementation of this pathway, although it was successful in the few programs that offered it.

In 2005, the DIRECT (Diagnostic and Interventional Radiology-Enhanced Clinical Training) pathway was approved by the ABR as a pathway to specialty board certification in DR and subspecialty certification in VIR. This pathway, which required individual approval by the ABR, allowed for 24 months of training in non-procedural patient care, 27 months of DR, and 21 months of VIR. The initial intent of this pathway was to permit individuals transferring from other specialties into DR to apply 2 years of their other training toward the usual total of 6 years by reducing the DR rotations and to have more exposure to VIR. Several institutions developed successful programs that began at the PGY1 level, but overall the implementation of this pathway was also limited.

In 2006, the SIR initiated development of a proposal to further modify training as well as transition VIR from a subspecialty of DR to a primary specialty. As had been anticipated, IR was continuing to expand in breadth and complexity and with it the importance of non-procedural patient care. Practicing IRs were developing levels of content expertise that went well beyond their training in imaging and procedures, functioning as integral members of the clinical patient care team. The classic example was the IR who focused on cancer and was viewed first as a member of the cancer team and second as an IR.

A proposal for a new specialty and training program was presented to the ABR in 2007, which then worked with the SIR and multiple other stakeholders in DR over the next 5 years. A refined and carefully vetted proposal was ultimately approved by the member boards of the ABMS in 2012. The fundamental feature of the proposal was the unique combination of imaging expertise, procedural expertise, and non-procedural patient care that differentiated IR from all other primary specialties. The ABMS approved a new ABR certificate that included both IR and DR (the IR/DR certificate). With approval of the new certificate, the ABMS also approved the concept of a dedicated residency. The overarching significance of the ABMS approval of IR as a primary specialty of medicine was the affirmation by all other ABMS boards that competency in non-procedural patient care was not only a unique feature of IR but expected of individuals trained in IR. In essence, from the outside looking in, non-procedural patient care was recognized as an essential part of IR.

In 2015, the ACGME approved the structure of the training that fulfilled the requirements for IR/DR certification and began accrediting the first programs. Termed the IR residency, this training will have replaced all current VIR fellowships by the year 2020. As this training results in eligibility for a single certificate that includes two specialties (IR and DR), there are several features that are unique to these training programs. For example, the majority of these programs reside in DR departments and have shared leadership between DR (for the DR portions of the training) and IR (for the IR years). There are two basic configurations, the integrated and independent programs.

The integrated program requires a 1-year internship, preferably in surgery, followed by 5 years in a single department. The first 3 years are identical to the first 3 years of DR training, after which the resident spends the majority of the next 2 years in IR or IR-related rotations. One rotation in an ICU is mandated. Entry into integrated residencies is from medical school. This is a major change from the traditional entry from DR residency. For the first time, medical students who are procedurally oriented can consider IR as a career option directly from medical school (although they still must complete an internship).

The independent programs require a 1 year internship and completion of a DR residency. The standard independent IR residency is 2 years in length and also requires one ICU rotation. However, residents who receive extra IR training during DR residency in a formal early specialization in IR (ESIR) pathway are eligible for advanced placement into the second year of the IR residency. The independent program provides great flexibility, as residents can move between institutions (DR residency in one place, IR residency in another), whereas integrated residents much complete both DR and IR in the same institution. The independent pathway allows DR programs without IR residencies to remain competitive, as their graduates can still train in IR. If these programs can offer ESIR , their residents will be able to complete all of their training in the same time frame as integrated residents. Lastly, this pathway provides a training option in IR for those who develop and interest after starting DR.

The certification process is the same regardless of the residency, in that IR residents in both the integrated and independent programs take the same DR core examination as the DR residents. Subsequently, certification in IR/DR requires passing a combined computerized and oral examination after completion of training. The oral examination is considered an essential tool for assessing competency in IR, and was therefore retained for this certificate, although it has been dropped for DR.

The IR/DR certificate is unusual in that it indicates competency in two ABR primary specialties, IR and DR. This is a foundational concept, in that the IR/DR certificate can be used as the parent specialty certificate for other DR subspecialties, such as pediatric radiology or neuroradiology. More important, it emphasizes that general imaging competency is unique to IR compared to all other specialties that perform image-guided interventions. This competency is the special feature that IR brings to medicine and which all of the ABMS member boards wanted preserved in the IR specialty certificate.

IR training has been evolving for the entire history of the specialty and will continue to evolve. With each change new opportunities arise, as well as challenges. Initial accreditation of fellowships unified training programs and made system-wide changes feasible. Recognition as a specialty was based on the importance of non-procedural patient care and maintaining imaging competency. The next steps may be development of areas of content expertise to a level that would benefit from training beyond residency. Perhaps oncology or vascular fellowships would produce individuals with special competency in these areas. However, the very same issues that arose when the idea of recognized VIR fellowships was debated in the 1980s are likely to surface again; concerns about disenfranchising IRs who do not seek additional training or weakening of the structure of IR by allowing subgroups to differentiate. As in the past, IR will find a way, and this exciting specialty will continue to innovate, advance care, and lead in image-guided interventions.

References

1.

Seldinger SI. Catheter replacement of the needle in percutaneous arteriography; a new technique. Acta Radiol. 1953;39:368–76.Crossref

2.

Grigg ERN. The RSNA historic symposium on American Radiology: then and now. Radiology. 1971;100:1–26.Crossref

3.

Berberich J, Hirsch S. Die Rontgenographische Darstellung der Arterien und Venen im lebenden Menschen. Klin Wchnschr. 1923;49:2226.Crossref

4.

Baum S, Athanasoulis C. The beginnings of the Society of Interventional Radiology (SIR, née SCVIR, SCVR). J Vasc Interv Radiol. 2003;14:837–40.Crossref

5.

Ferris EJ, Baron MG, Becker GJ, Gardiner GA Jr, Levin D. Cardiovascular and interventional radiology fellowship training programs. Radiology. 1989;170:959–60.Crossref

6.

Kaufman JA. The interventional radiology/diagnostic radiology certificate and interventional radiology residency. Radiology. 2014;273:318–21.Crossref

© Springer International Publishing AG, part of Springer Nature 2018

Nicole A. Keefe, Ziv J Haskal, Auh Whan Park and John F. Angle (eds.)IR Playbookhttps://doi.org/10.1007/978-3-319-71300-7_2

2. Simulation Training in Interventional Radiology

Gabriel Bartal¹   and John H. Rundback²  

(1)

Diagnostic and Interventional Radiology, Meir Medical Center, Kfar Saba, Sackler Medical School, Tel Aviv University, Tel Aviv, Israel

(2)

Holy Name Medical Center, Interventional Institute, Teaneck, NJ, USA

Gabriel Bartal (Corresponding author)

John H. Rundback

Email: [e-mail]

Keywords

Medical Simulation TrainingPatient-Specific SimulationMedical EducationInterventional Radiology

Introduction

Medical simulation is a cross-disciplinary realistic and economical training and feedback method, in which learners can repeatedly practice and review tasks and processes using physical or virtual reality models. Simulation allows trainees to learn, develop, maintain, and improve skills in virtual environments or on models. They can be used until required proficiency is achieved, without harming the patients. Moreover, simulation-based education facilitates knowledge, ability, and approach that can be safely and efficiently acquired by student and/or physician. Simulated procedure-based skills and team working can be learnt, rehearsed, and measured, thus providing a base for certification in specific fields of medical practice.

Medicine has traditionally relied on a see one, do one approach to learning and experience. This exposes patients to inexperienced health-care practitioners , and the dangers and harm associated with this are increasingly unacceptable [1]. It is essential to explore, define, and implement models of physicians training models that do not expose the patient to preventable errors [2]. One such model is simulation-based training [1, 2].

Simulation is a model of an object, process, or system that can be manipulated in some way. It replicates some aspects of reality known as the simuland (i.e., the object, process, or system that is simulated). The value of simulation is a function of its ability to stand for the simuland with sufficient fidelity (accuracy) to serve trainee’s purpose.

With recent advances in medical imaging technologies like CT angiography and MR angiography , most of the diagnostic angiographic procedures (i.e., peripheral angiography, angiography in a bleeding patient, and almost any kind of diagnostic angiography) have become less common, reducing the number of occasions to learn basic catheter manipulation skills [2]. Nevertheless, gaining selective catheterization skills is necessary for therapeutic endovascular interventions.

The RSNA (Radiological Society of North America), SIR (Society of Interventional Radiology) and CIRSE (Cardiovascular Interventional Radiology Society of Europe) established a joint medical simulation task force in order to improve patient care by guiding the implementation of simulation in IR [3]. The United States Food and Drug Administration (FDA) also promotes adoption and implementation of simulation training in IR. For example, FDA requires mandatory proficiency training in a simulator before prior to performing carotid artery stenting (CAS) on patients [4].

Medical Error

Medical error is one of the most challenging problems of modern medicine. It is also one of the drivers to develop reliable and cost-effective best tools for simulation. Here are some examples of the scope of the problem:

1997: 180,000 deaths annually from medication errors and adverse reactions [5].

1999: 44,000 to 98,000 deaths annually from medical errors [6].

2000: 225,000 deaths annually from medical errors, including 106,000 deaths due to non-error adverse events of medications [7].

2010: The Office of Inspector General for Health and Human Services said that bad hospital care contributed to the deaths of 180,000 patients in Medicare alone in a given year.

2013: Serious harm seems to be 10- to 20-fold more common than lethal harm.

According to the Journal of Patient Safety, the numbers may be between 210,000 and 440,000 patients. These numbers make medical errors the third medical cause of death.

These sobering facts emphasize the need for methodical and standardized practitioner training to reduce error.

History of Medical Simulation

Medical simulation has a very long history; the first evidence comes from ancient Egypt, around 2000 BC, where surgeon priests simulated surgical procedures (e.g., rhinoplasty) on cadavers. Parisian Dr. Gregoire in the seventeenth century created a manikin from cadaver pelvis with skin stretched across it to simulate an abdomen and with the help of a dead fetus explained assisted complicated deliveries. In 1739 Dr. William Smellie introduced a mechanical labor device by creating female models from a real pelvis, with ligaments, muscles, skin, artificial materials, and cloth dolls to simulate the fetus. By 1747, he had three machines, with six artificial children.

In the modern era, simulation in medical education started with the use of standardized patients. For interventional radiologists, the case conference has been a long-standing form of simulation. Today, simulation training using devices and technology is becoming more common. Initially, simulation training used computer-based training modules such as RSNA’s Medical Imaging Resource Center and the AuntMinnie.​com Case of the Day [2].

Professions that require precise cognitive and physical tasks in high-risk environments are the best candidates for simulation training. Medical simulation is often used as a tool to assist a fellow or resident to practice performing a given procedure to improve proficiency. It can be practiced either under the guidance of a mentor, with performance feedback being provided by the mentor, or in a self-directed mode, with self-assessment coming from the learner. Recently, with implementation of computer-based training , the performance data is provided by the simulator.

Traditional Training

Training based on the current see one, do one, teach one model is insufficient as trainees learn by practicing on real patients, which can be an issue when performing interventional procedures. Modern hands-on medical and procedural training is limited by duty hour restrictions, intolerance for the use of live animal, medicolegal concerns, and the increasing range and complexity of procedures and instruments that must be mastered. Indeed, residents have expressed feeling inadequately trained to perform unsupervised procedures safely exposing patients to unnecessary harm [7]. Equally, mature practitioners have an ongoing need for maintaining familiarity with infrequently used devices or new devices and procedures.

Two categories of skills that may benefit from simulation training: procedural and non-procedural. Procedural ones include the physical skills a physician requires to complete an interventional procedure. Non-procedural skills encompass interpersonal, cognitive, or interpretive competencies.

Types of Simulators

1.

Phantoms or Part Task Trainers: Models of Anatomical Regions Aimed to Teach Specific Skills

Low-tech task trainers remain at the heart of clinical skills and procedural instruction. They are fundamental in the teaching of anatomic landmarks and in enabling learners to acquire, develop, and maintain the necessary motor skills required to perform specific tasks.

For example, realistic 3D patient-specific renal biopsy phantoms have been created using CT data, manufactured from an organ mold and casted thereafter (Fig. 2.1). Using gelatin gel materials with calibrated parameters allows phantoms to provide realistic mechanical, ultrasound, and CT properties and mimics various pathologies (Fig. 2.2) [8].

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Fig. 2.1

Kidney box phantom CT scan (upper row) and US images (lower row) [8]. (a, c) Phantom and ultrasound demonstrating a focal lesion (red arrow) within the lower pole of the right kidney. (b, d) The kidney is visualized in relation to the liver for ablation planning. (e) The 10 L ablation probe is visualized adjacent to and then within the renal lesion. The phantom box can aid in procedural planning in order to avoid vital structures and practice technique (Reprinted by permission from SafeToAct Ltd. © 2017)

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Fig. 2.2

Schematic presentation of the kidney phantom [8] (Reprinted by permission from SafeToAct Ltd. © 2017)

For biopsies, practice is important for maintaining and improving skills [6], yielding faster performance, reducing the number of missed target lesions [1], lowering procedure room time [7], and improving success rates [8]. Even experienced radiologists face a learning curve when equipment changes are made [7]. Thus, realistic phantoms can be useful for both practicing radiologists and trainees.

2.

Computer-based learning modules are digital simulations on the computer.

3.

Computer-assisted mannequins are full body models that can simulate physiological responses.

4.

Virtual reality simulators are immersive environments simulating live experience for the user and resembling the real world. For instance, Mentice AB (Gothenburg, Sweden) has created virtual reality simulation platforms for both uterine artery and prostatic artery embolization.

5.

Augmented reality simulators use the existing environment, overlay digital information on top of it, and then integrate digital simulation with physical simulator’s environment in real time.

The educational validity of simulators is evaluated based on five aspects [9–11]:

1.

Face validity evaluates how well a simulator mirrors real life. This is easiest to assess and is done by surveying participants regarding the realism of the simulator.

2.

Content validity measures of how well a simulator tests knowledge; it is intended to show how well the simulator trains one in the expected skills. This can be assessed by pre- and post-knowledge test to determine improvements in test score.

3.

Construct validity determines how well a simulator can differentiate participants by skill level. This can be assessed by including trainees of different experience levels in order to determine whether the final scores differ.

4.

Concurrent validity compares simulators with standard methods. This compares the simulation and the apprenticeship or didactic model.

5.

Predictive validity evaluates how well performance on a simulator predicts performance in real case. This is the hardest validity to determine.

Challenges in Interventional Radiologist’s Training

Training in IR is inherently visual and requires hands-on experience. Residents or fellows are usually trained 1:1 or 2:1 with a scrubbed supervisor. A senior operator’s view is an ideal additional teaching tool as he or she can comment in real time and impart specific valuable knowledge. Senior trainees do require supervision but also require a degree of independence to make decisions. This balance is hard to achieve as patient safety is overriding.

One of the limiting factors for many young IR physicians is a fear of personal radiation exposure (refer to Chap. 3 for more information on radiation safety). One of the important sources of personnel exposure is fluoroscopy time. Medical simulation allows practitioners to improve their performance in radiation-free conditions. Better and efficient performance of procedures will reduce fluoroscopy time and radiation exposure.

One of the most important guidance tools in image-guided interventions is ultrasound; this requires skill in scanning, image interpretation, and needle guidance [1]. Ultrasound-guided procedure simulations have shown improvement in knowledge maintenance, skills, and self-confidence, compared to pre-simulation training achievements [12]. Currently, most simulation is directed toward the vascular field, which is more complex and requires a very skilled operator.

Animal Simulation Labs

The use of animals for research and clinical training is both expensive and limited for one-time training events. Supply, ethical, and legal limitations support the use of non-animal alternatives (i.e., simulators). Several professional societies no longer allow the use of live animals in clinical training programs but endorse simulators instead [13].

Virtual Reality Simulation

This is a sophisticated and complex algorithm-based digital visualization of a medical procedure manipulated by a hardware component that an operator can interactively use in real time to accurately practice and test a surgical procedure [14, 15]. It contains all the benefits of a box/endo trainer, provides an added value of practicing full procedures, and allows learning the anatomy from different perspectives and practicing and managing complications. It can also provide accurate feedback on performance. 

Catheterization and Angiography

Catheterization and angiography are basic and important skills that one must master in order to become a competent interventional radiologist. Different techniques including fluoroscopy, road mapping and DSA (Digital Subtraction Angiography) can be practiced on simulators. Simulation can both shorten the training time and improve catheter skills [16]. It has been shown to effectively train catheter-based endovascular skills to residents without any experience [17].

Angioplasty and Stent Placement

Angioplasty and stenting are core procedures in vascular interventions. Training of renal angioplasty and stenting using the VIST-Lab (Mentice) simulator has been shown to accelerate an apprentices’ learning curve to reach proficient levels [15, 18]. Moreover, renal stenting outcomes when tested on the ANGIO Mentor (Simbionix 3D Systems simulator) improved after training on the simulator, showing technical skill improvement and increased patient safety [19]. All main vendors developed simulation training programs for major vasculature stenting. For example, carotid artery stenting results evaluated with the VIST-Lab (Mentice) simulator improved after novices’ simulation training [20].

Simulator training should be performed in a stepwise fashion, from the basic to more complex procedure. For example, the trainee will practice iliac artery stenting prior to superficial femoral artery angioplasty and stenting procedures, which results in better scores on the ANGIO Mentor (Simbionix 3D Systems) endovascular simulator [21, 22]. Simulation of stenting can be used for more than just gaining general skills, but procedures can be rehearsed on the ANGIO Mentor simulator based on pre-acquired CTA of a patient prior to performing a procedure on the same patient [23, 24]. It was reported that patient-specific rehearsals resulted in better simulation scores [21], and these rehearsals could, in some instances, lead to changes in the patient’s procedural plan [24].

Endovascular Aneurysm Repair

Training for medical procedures and surgery requires the adoption of a wide range of unique skills which include an in-depth understanding of anatomy and anatomic variations, tools and devices, logistical planning, complication avoidance, and haptic feedback. For these reasons, procedural and surgical simulators are particularly appealing for procedural training, proficiency assessment, and skill optimization. Surgical simulators have already been explored for sinus surgery [25], as well as gynecologic [26] and urology procedures [27].

There is early evidence supporting the role of simulators for endovascular aneurysm repair (EVAR) [28–31]. Potential advantages include improved safety (reduced radiation exposure, contrast media usage, and procedure time) [31], technical readiness (anticipate and prevent complications, optimize device and graft selection and sizing, assist in selection of ideal working projection) [30], and enhanced decision making and confidence in real procedures. While not yet proven, this may translate to financial improvement through fewer complications and resulting shorter patient stays or readmissions. Most importantly, the educational value in training inexperienced operators is immeasurable; an unlimited library of training cases representing specific care challenges can be developed and utilized for physician training.

The simulator is positioned on a table or gurney so that two operators can stand on both sides of the patient for the simulated procedure, also called procedure rehearsal (Fig. 2.3). Simulators generally use patient-specific CT data to create a fully interactive fluoroscopic simulation of anatomy. Images can be displayed in a typical fluoroscopic mode or with bony overlay. In addition, 3-dimensional modeling can be displayed (Fig. 2.4) both for endograft planning and treatment rehearsal. The simulator has specific aneurysm graft data embedded in the software planning, allowing digital selection of both specific graft manufacturers as well as sizes and configurations. For instance, even branched and fenestrated grafts have become available recently on the 3D Systems (Tel Aviv, Israel) simulator to rehearse these often complex procedures that might benefit from practice prior to actual live performance.

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Fig. 2.3

Examples of simulators. The Simbionix percutaneous renal access simulator (a) and the Simbionix ANGIO Mentor platform (b). Simbionix ANGIO Mentor photo courtesy of 3D Systems/Simbionix URO-PERC Mentor photo courtesy of 3D Systems

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Fig. 2.4

EVAR image displays simulated procedures. The simulator can be used both for planning (a) and treatment simulation (b). During planning (a), surface rendered center line images allow segmentation and measuring for graft selection; a spindle view (top right panel) and corresponding axial image (bottom right panel) allow accurate cross-sectional diameter measurements at every level. During procedure rehearsal (b), patient level CT data (bottom left) is shown along with either a 3-dimensional surface rendered landscaped view (middle panel) or traditional contrast-enhanced fluoroscopic rendering (right panel)

3D Systems (formerly Simbionix) platform (Tel Aviv, Israel) has two access limbs or ports through which each operator can insert blunt-ended catheters and a stiff wire that then appear and perform on the monitor as the digitally selected device. Selectable devices that can be simulated include sheaths, wires, shaped catheters, and endografts. The torque response of devices is generally 1:1, representing a potential limitation compared to actual procedures in which patient anatomy and friction may impact catheter movement. Similarly, there is currently no haptic feedback or force sensing function. However, the devices do respond to arterial tortuosity and diameter; in particular, grafts may shift position, foreshorten, or lose parallax upon simulated deployment as they would in real life. The individual controlling the input on the monitor can make quick adjustments for modifying device selection or sheath position without completely removing the catheters from the machine.

Operators have access to table side controls including fluoroscopic and C-arm projection. An electronic syringe can be attached to catheters to create an angiographic run during depression of the syringe plunger. There are handles and controls from manufacturers that look, feel, and respond like the deployment mechanisms of real grafts on separate insertable catheters.

Clinical Applications

Aortic Procedures Planning

The simulation workflow is as follows:

1.

Obtain a contrast-enhanced computed tomographic angiogram (CTA) on the patient and send the CT data to the simulation platform.

2.

Use the platform to perform center line measurements and endograft selection.

3.

Perform independent graft planning and selection using customary techniques (often from the axial CT data alone), then compare the planning notes and possible strategies.

4.

Rehearse the EVAR on the simulator using the different strategies and endograft configurations.

5.

Modify the actual treatment plan based upon observations during rehearsal.

6.

Order the desired grafts.

7.

Proceed with the actual live EVAR.

Inherent in this workflow is the ability to make multiple modifications in device and treatment strategy prior to actual procedure performance. In our experience, there have been three important facets of EVAR affected by procedure rehearsal: the selection of optimal angles to be used for endograft positioning and deployment, graft and component sizing and selection, and identifying the best obliquity for cannulation of the contralateral limb. While third-party software options exist to perform center-line imaging that may support best graft selection, our experience has shown that this is not a substitute for actually trying a graft in a simulated system (Fig. 2.5). Aneurysm morphologies with long distances to the aortic bifurcation and tortuous iliac access have particularly benefited from procedure rehearsal. In these cases, we have found that limb lengths measured from traditional cross-sectional imaging do not reliably determine the idealized limb length needed to avoid type 1B endoleaks.

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Fig. 2.5

Example of procedure simulation changing EVAR planning . Initial graft selection as determined by axial CT images resulted in a large type 1A endoleak (arrows) during rehearsal (a). A larger diameter graft (curved arrow) was therefore used for the actual procedure with successful sealing of the aneurysm neck (b)

Preliminary data supports the subjective advantages of EVAR procedural simulation (personal data). In an early analysis of 43 questionnaires completed by 23 different operators after 24 previously rehearsed EVAR procedures, all physicians reported a positive impact of rehearsal. Using a 10-point scale (10 being most favorable), EVAR simulation increased perception of intra-staff collaboration effectiveness (M = 9.12, SD = 1.03, median 9.00), primary operator procedure confidence (M = 8.51, SD = 1.4, median 9.00) and readiness (M = 8.51, SD = 1.12, median 9.00), and real case technical performance (M = 8.09, SD = 1.38, median 8.00). The similarity of C-arm projections to the real procedure was also rated high (M = 8.77, SD = 1.48, median 9.00).

Performance Assessment

Medical education requires assessment of knowledge, competence, performance, and action. These same skills are applicable for evaluation of the abilities acquired with simulation [32]. Moreover, simulation can provide trainee performance assessment reports; these can be used to compare improvement over time (Table 2.1).

Table 2.1

Assessment tools to evaluate trainee performance

Medical Simulation in Radiation Dose Management

Both trainees and experienced practitioners must maintain a constant awareness of radiation dosage and opportunities to minimize exposure for patients and personnel. Simulators can allow for repeatable training so as to increase procedural efficiency, reduce complication rates, and ideally, radiation exposure (refer to Chap. 3 for more information on radiation safety) [38, 39].

Future Prospects

A broad lack of adoption of machine-based manual simulation remains hampered by high cost, limited availability, and insufficient resources. Future platforms may be limited to high-volume training centers or as a part of educational courses. Nonetheless, there remains a need for more expeditious software development to incorporate rapidly evolving graft designs and strategies. An additional critical component will be the engineering of better haptic systems that provide force feedback during procedure rehearsal, since tactile sensory input is an important aspect of anticipating device performance and avoiding complications.

Nonmanual simulation may serve a future role as well. Thin client software platforms without a hands-on component may still serve a useful role in quickly testing devices in patient-specific anatomy. Simulators are an objective assessment tool for measuring trainee’s performance with pre-programmed metrics. Furthermore, the FDA encourages the use of simulation for training as part of introducing new medical device to the market. The time has come for IR’s to embrace simulation training. Even so, further research to evaluate simulator performance in relation to real-world skills is still required.

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© Springer International Publishing AG, part of Springer Nature 2018

Nicole A. Keefe, Ziv J Haskal, Auh Whan Park and John F. Angle (eds.)IR Playbookhttps://doi.org/10.1007/978-3-319-71300-7_3

3. Radiation Safety

Gabriel Bartal¹   and Eliseo Vano²  

(1)

Diagnostic and Interventional Radiology, Meir Medical Center, Kfar Saba, Sackler Medical School, Tel Aviv University, Tel Aviv, Israel

(2)

Department of Medical Physics, San Carlos University Hospital – Complutense University, Madrid, Spain

Gabriel Bartal (Corresponding author)

Eliseo Vano

Email: [e-mail]

Keywords

Radiation protectionOptimizationPatient dosimetryOccupational dosimetryX-ray systemRadiation risksPregnancyPediatrics

Introduction

Increasing numbers of medical specialists are performing fluoroscopy-guided interventional procedures (FGIP) [1, 2]. The use of medical ionizing radiation in the USA was reported sevenfold higher in 2006 compared to 1980, when the amount due to FGIP increased 33 times [3, 4]. The new international recommendations on radiation safety have led to national and international efforts to promote patient and staff radiation safety.

Key Points

Specialties that utilize image guidance:

Interventional radiology

Diagnostic radiology

Urology

Gastroenterology

Orthopedic surgery

Vascular surgery

Trauma and general surgery

Anesthesiology

Cardiology

Inherent in the growing use of medical radiation is a better understanding of the potential stochastic risks for cancer and the methods to monitor and reduce the risk of deterministic effects for skin injury. Modern angiography systems allow virtually unlimited exposure. CT or MR angiography are routinely used for most endovascular procedures. It is generally believed that the exposure to the staff is not significant and does not represent a real hazard. In fact, there is real risk to operators and staff of both tumor formation and damage to the eyes. Planning of each and every intervention should comprise radiation protection measures as part of the procedure [5]. Lack of radiation protection training of those working with fluoroscopy can increase the radiation risk to workers and patients alike. Patient dose monitoring is essential whenever fluoroscopy is used. The International Commission on Radiological Protection (ICRP) recommended that manufacturers should develop systems to indicate patient dose indices with the possibility of producing patient dose reports and shielding screens that can be effectively used for the protection of workers using fluoroscopy without hindering the clinical task [6].

Obesity is recognized worldwide as an epidemic causing devastating or fatal health disorders, such as diabetes and heart disease [7, 8]. The scatter radiation exposure to the operator’s waist increases dramatically with obese patients. It doubles with each additional 5 cm (1.97 in) of patient thickness; patient entrance air kerma increases by a factor of 8.4 when thickness increased from 24 to 34 cm [9–15]. Complex FGIP are associated with high radiation doses. These procedures can result in patient skin doses that are high enough to cause radiation injury and an increased risk of cancer [16].

Pediatric patients have a higher average risk of developing cancer compared with adults receiving the same radiation dose. The longer life expectancy in children allows more time for any harmful effects of radiation to manifest, and developing organs and tissues are more sensitive to the effects of radiation. Special attention is required to optimize appropriate protocols for pediatric patients. Major pediatric interventional procedures should be performed by experienced pediatric interventional operators, preferably with additional training in radiological protection [17, 18].

The Society of Interventional Radiology (SIR) and the Cardiovascular and Interventional Radiology Society of Europe (CIRSE) have jointly produced several guidelines that should be part of the education material for trainees aiming to be interventionists:

1.

Patient Radiation Dose Management [19]

2.

Occupational Radiation Protection in Interventional Radiology [20]

3.

Radiation Management for Interventions using Fluoroscopic or Computed Tomographic Guidance during Pregnancy [21]

4.

Occupational Radiation Protection of Pregnant or Potentially Pregnant Workers in Interventional Radiology [22]

X-ray Systems for Interventional Radiology

X-ray and imaging systems for interventional radiology are complex and have several modes to acquire images using different levels of radiation dose depending on the required image quality and diagnostic information for the clinical task. New technology in interventional imaging systems allows for substantial reduction in patient doses while maintaining enough image quality and diagnostic information, thanks to advanced image processing and refined selection of technical parameters during the imaging acquisition. During the commissioning of x-ray systems, some basic information about the modes of operation should be obtained [23].

Basic Radiation Physics Units

Absorbed dose is the energy absorbed per unit mass. The unit of absorbed dose is the gray (Gy); 1 gray is 1 Joule per kilogram.

Air kerma is the kinetic energy released in a mass of air. For the x-ray energies utilized in interventional procedures, the air kerma is numerically equal to the absorbed dose in air. The units for air kerma are the gray (Gy) or milligray (mGy) (Fig. 3.1).

The dose-area product (DAP) also called the kerma-area product (KAP) is the sum of the products of the incident doses and the areas of the x-ray fields for all segments of an interventional procedure. It can be determined at any convenient location between the x-ray source and the patient. The practical used unit for DAP is Gy·cm². This quantity is presented by most of the interventional x-ray systems during the procedures, and the cumulative value is reported at the end of the procedure (Fig. 3.1).

Air kerma at the patient entrance reference point. This patient entrance reference point is located 15 cm from the isocenter in the direction of the focal spot for C-arm interventional x-ray equipment (Fig. 3.2). These two quantities (DAP and air kerma) are the most used by the x-ray systems to show interventionists the radiation dose received by the patients [24].

Equivalent dose is derived from the absorbed doses in specific tissues, weighted by the relative effect of the type and energy of the radiation encountered. For x-rays used in interventional procedures, the weighting factor is 1. Dose limits for occupational exposures are expressed in equivalent doses for deterministic effects in specific tissues. It is measured in Sievert (Sv).

Effective dose measures the global risk of the person exposed to ionizing radiation and takes into account the equivalent doses in the different tissues and the radiosensitivity of that tissue (Table 3.1). This quantity is used to determine radiation exposure risk to cancer development. Dose limits for occupational exposures are expressed as effective dose for stochastic effects throughout the body [26]. It is also measured in Sievert (Sv).

Personal dose equivalent is the operational quantity for individual monitoring and represented by Hp(d) (Fig. 3.3). It is the dose equivalent in soft tissue at an appropriate depth, d, below a specific point on the human body. The specified point is normally taken at 10 mm, termed Hp(10) for monitoring the effective dose. For the assessment of the dose to the skin and to the hands and feet, Hp(0.07) is used. A depth of 3 mm is adequate for monitoring the dose to the lens of the eye. In practice, Hp(0.07) and Hp(10) can be used for monitoring occupational doses during interventions guided by radiological imaging. A typical personal dosimeter provides two values, Hp(0.07) and Hp(10). Hp(0.07) from the collar dosimeter worn over protective garments (apron, thyroid shield) which provides a reasonable estimate of the dose delivered to the surface of the unshielded skin and to the lens of the eye. A single under-lead dosimeter does not provide any information about eye dose [27].

../images/432673_1_En_3_Chapter/432673_1_En_3_Fig1_HTML.png

Fig. 3.1

Most of the interventional x-ray systems offer information of the relevant dosimetric parameters inside the catheterization room. In the figure, the values of the kerma-area product from two different systems are highlighted

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Fig. 3.2

Shows the position of the patient entrance reference point as defined by the International Electrotechnical Commission [24]. Below the patient and table is the x-ray tube and above the patient is the image intensifier, commonly called the II (pronounced eye-eye) (Reprinted with permission from Ref. [25])

Table 3.1

Tissue weighting factors recommended by International Commission on Radiological Protection (ICRP)

Adapted with permission from Ref. [26]

Remainder tissues (14 in total): adrenals, extrathoracic (ET) region, gallbladder, heart, kidneys, lymphatic nodes, muscle, oral mucosa, pancreas, prostate, small intestine, spleen, thymus, uterus/cervix

../images/432673_1_En_3_Chapter/432673_1_En_3_Fig3_HTML.png

Fig. 3.3

Typical position of the personal dosimeters to estimate occupational radiation risk. The indicated dose limits (recommended by ICRP) are still valid except the one for the lens of the eyes than now has been lowered to a value of 20 mSv/year (Reprinted with permission from Ref. [1])

Summary of Biological Effects of Ionizing Radiation

The biological effects of radiation can be grouped into two types: deterministic effects (tissue reactions) and stochastic effects (cancer and heritable effects).

Key Points

Deterministic effects: Side effect occurs above a threshold radiation dose and severity increases with increasing dose.

Stochastic effects: Risk of developing side effect increases above a certain dose but the severity does not.

Deterministic Effects

Deterministic effects describe a relationship between radiation and side effects which occur above a certain threshold. With increasing doses above the threshold, the probability of occurrence will rise steeply to l00% (i.e., every exposed person will show the effect), and the severity of the effect will increase with dose. Such effects can occur in some complex interventional procedures [26, 28]. In FGIP, the tissues of concern for deterministic effects are the skin and the lens of the eye.

Key Points

Deterministic effects that occur above a threshold absorbed dose:

Fetal abnormality: 0.1–0.5 Gy

Sterility: 2–3 Gy

Skin erythema: 2–5 Gy

Hair loss: 2–5 Gy

Lethality (whole body): 3–5 Gy

Cataracts: 5 Gy

Irreversible skin damage: 20–40 Gy

Stochastic Effects

There is good evidence from cellular and molecular biology that radiation damage to the DNA in a single cell can lead to a transformed cell that is still capable of reproduction. Despite the cellular repair mechanisms, there is a small probability that this type of damage can lead to a malignant condition termed the somatic effect . For stochastic effects, a simple linear non-threshold dose-response relationship is assumed for radiological protection purposes. At higher doses and dose rates, the probability of developing cancer increases. At even higher doses, close to the thresholds of deterministic effects (tissue reactions), the probability increases more slowly and may begin to decrease, because of the competing effect of cell killing. These effects, both somatic and heritable, are called stochastic. The probability of such effects is increased when ionizing radiation is used in medical procedures [28].

Effects of In Utero Irradiation

There are radiation-related risks to the embryo/fetus during pregnancy that are related to the stage of pregnancy and the absorbed dose to the embryo/fetus. At doses below 100 mGy, lethal effects are extremely infrequent, and there is no reason to believe that exposure will result in any fetal abnormalities. During the period of major organogenesis, conventionally taken to be from the third to the eighth week after conception, malformations can occur, particularly in the organs under development at the time of exposure. These effects have a threshold of approximately 100 mGy [28, 29].

Radiation Protection System in Medicine

Several features of radiation exposure in medicine require an approach to radiation protection that is somewhat different from that for other types of radiation exposure. Medical uses of radiation for patients is voluntary in nature, with an expectation of direct individual health benefit to the patient.

In medicine, the goal is to use the appropriate radiation dose to obtain the desired image or desired therapy without excess exposure. In this regard, the ICRP introduced the use of diagnostic reference levels for imaging procedures. Radiation protection should be part of the quality assurance (QA) programs in interventional radiology (Fig. 3.4).

../images/432673_1_En_3_Chapter/432673_1_En_3_Fig4_HTML.png

Fig. 3.4

For medical exposures, only the principles of justification and optimization are applied. Dose limits only apply to the occupational and public exposures to ionizing radiation

Radiation protection in medicine serves to identify the minimal dose for patients while allowing appropriate diagnosis or therapy and optimizing protection. The term ALARA (as low as reasonably achievable) is used to identify the optimization principle. ALARA is only part of the concept of optimization. The entire concept implies, more precisely, keeping patient exposure to the minimum necessary to achieve the required medical objective, both diagnostic and therapeutic. That said, dose to a patient should not be limited if effective diagnosis and treatment are imperiled. The physicians and other health professionals involved in the procedures that irradiate patients should always be trained in the principles of radiological protection, including the basic principles of physics and biology [17]. Physicians, radiographers, and medical physicists all play an essential role in the safe use of fluoroscopy in medical practice [30].

Key Points

As Low As Reasonably Achievable (ALARA) is based on the safety principle of minimizing radiation dose and limiting radioactive materials into the environment by employing all reasonable methods. The three major principles for a good protection are:

1.

Time

2.

Distance

3.

Shielding

Radiation Protection of Patients (And Diagnostic Reference Levels)

Diagnostic reference levels (DRLs ) are used in medical imaging to indicate whether, in routine conditions, the levels of patient dose from a specified imaging procedure are unusually high or low for that procedure. If so, a local review should be initiated to determine whether protection has been adequately optimized or whether corrective action is required [26].

DRLs should be reviewed at intervals that represent a compromise between the necessary stability and the long-term changes in the observed patient dose distributions [31, 32]. National DRLs should be set as the seventy-fifth percentile of median values obtained in a sample of representative centers. Median values of the DRL quantity for medical imaging procedures should be compared with DRLs to identify whether the data are substantially higher or lower than might be anticipated [32].

To protect a patient from excess radiation, the patient should be placed as far as possible away from the x-ray tube (portion underneath the table) and as close as possible to the image receptor (part above the table). Tight collimation also decreases patient dose and improves image quality by reducing scatter.

Radiation Protection of Staff (Including Pregnant Women)

There are different theories regarding possible dangers of exposure to personnel. It is extremely important to adapt the behavior and a safe working culture to the new powerful x-ray machines. Over time, longer procedures can lead to cumulative damage to our eyes if the proper protection is not regularly used. Reports on the radiosensitivity of the eye that can lead to visual impairment are available [33, 34].

In 2010, joint guidelines on protection of personnel were published by SIR (North American Society of Interventional Radiology) and CIRSE (Cardiovascular Interventional Radiology Society of Europe) in the Journals of both Societies (JVIR and CVIR) [20]. These guidelines provide a comprehensive overview that includes detailed instructions on why and how to protect IR from occupational exposure. These guidelines should become an integral part of any IR training program as well as routine practice in IR Labs.

Effective use of occupational radiation protection methods requires both appropriate education and training in radiation protection for all interventional radiology personnel and the availability of appropriate protective tools and equipment. Regular review and investigation of personnel monitoring results, accompanied by changes in how procedures are performed and equipment used, will ensure continual improvement in the practice of radiation protection in the interventional suite [35].

Passive and Active Personnel Radiation Protection

Personnel radiation protection process includes passive and active tools (Table 3.2). Passive radiation protection is based on the equipment in the IR lab. Active radiation protection is based on the passive protection tools and is about adapting our behavior to the unfriendly environment in the fluoroscopy room.

Table 3.2

Passive and active radiation protection equipment

Active protection tools include protective drapes suspended from the table and from the ceiling. Table-suspended drapes hang from the side of the patient table, between the under-Table X-ray tube and the operator. They should always be employed, as they have been shown to substantially reduce operator dose.

Key Point

0.5 mm lead blocks approximately 95–99.5% of 70- to 100-kVp X-rays. Leaded glasses reduce exposure by a factor of 8–10.

It is not enough to have the protective tools available, but they must be used appropriately in order to safely protect all staff and patients within an interventional suite. The use of these tools must also be judged against their impedance to performing the procedure. Protective resources such as radiation protection gloves could lengthen the procedure in some cases and thus compromise the security and protection of the patient, as the tactile sensation of the catheter is reduced. In addition, the use of a leaded screen suspended from the ceiling could inhibit the movement of the C-arm x-ray system in some cases. Staff exposure drops dramatically with distance from the x-ray source. The inverse square law describes the proportional reduction in radiation density by the square of the distance.

Key Points