Interventional radiology offers targeted, minimally-invasive
therapeutic approaches that are viable alternatives to surgery. Some of
the most common procedures include angioplasty, stenting, thrombolysis,
embolization, radiofrequency ablation, and biopsy.
The rise in
demand for these image-guided procedures coincides with the
proliferation of new imaging technologies and interventional devices in
oncology, neuroradiology, and vascular interventions. Such procedures
are typically guided by fluoroscopy or computed tomography (CT) and
require several stages of imaging for treatment planning, guidance, and
follow up. The heavy use of imaging exposes patients and staff to
Growing awareness of dose
management has prompted equipment manufacturers to develop new
dose-control solutions, helping physicians to strike the right balance
between image quality and dose management.
Radiation safety in IR
2010, radiation safety concerns heightened with the release of new data
suggesting lens opacities (cataracts) occur at doses far lower than
those previously believed to cause cataracts.1 That same
year, the Society of Interventional Radiology (SIR) Safety and Health
Committee worked with the Cardiovascular and Interventional Radiological
Society of Europe (CIRSE) to develop a joint guideline on patient
radiation management.2 SIR-CIRSE also created guidelines for
occupational radiation protection designed for everyone working in the
interventional fluoroscopy suite. These include not only technologists
and nurses but also individuals such as anesthesiologists who may be in a
radiation environment only occasionally.1
to the SIR-CIRSE guidelines, occupational radiation protection is
necessary wherever radiation is used in the practice of medicine and is
especially important for image-guided medical procedures.1
The guidelines recommend that workers be required to wear dosimeters to
track radiation dose exposure. The recommendations in the United States
for occupational dose limits are set at 50 mSv in any one year, with a
lifetime limit of 10 mSv multiplied by the individual’s age in years. In
the European Union, the limit for E (stochastic effects throughout the
body) is 20 mSv per year, averaged over defined periods of 5 years.1
Low-dose image-guided systems
most effective way to decrease occupational exposure is reducing
patient dose across the entire treatment cycle. This benefits both
patients and staff, as decreasing patient dose results in a proportional
decrease in scatter dose to the operator.1 Of course, the greatest reduction occurs when imaging is performed without ionizing radiation, such as with ultrasound.1
is a heavy dependence on fluoroscopy guidance in order to track
instruments in the body for interventional radiology as well as many
conventional surgical procedures,” said Ron A. Von Jako, MD, PhD, Chief
Medical Officer at GE Healthcare OEC, who consults on the development of
these technologies. “And the longer it takes to do an individual
procedure, the longer the exposure may be to the user and the patient.”
Ultrasound as an alternative
device manufacturers have developed several new concepts for reducing
dose, such as combining fluoroscopic and ultrasound imaging units. With
efficiency and safety in mind, GE Healthcare introduced a combined
fluoroscopy/ultrasound All-In-One Unit, the OEC Elite + Venue 40*, part
of its family of Hybrid Operating Solutions (Figure 1). The GE Venue 40
tablet is mounted within the OEC 9900 Elite C-arm’s workstation,
allowing interventionalists to access the ultrasound tablet to guide the
insertion and placement of needles, guidewires, and catheters.
combined fluoroscopy/ultrasound unit minimizes the footprint in an
already crowded operating suite and can eliminate the need to wheel in
another imaging system. This helps to preserve a sterile environment and
allows staff to view collocated displays for fluoroscopy and ultrasound
without leaving the OR.
“Substituting an ultrasound probe
appropriately in some diagnostic or operative steps may obviate the need
to generate an additional x-ray,” said Von Jako. Mounting data suggest
ultrasound is promising in several interventional applications; as a
result, applications for ultrasound-guided techniques are expanding.
some cases, ultrasound is an emerging imaging technique with
possibilities to guide a pain-management needle to perform cervical and
lumbar facet blocks, occipital nerve blocks, epidural injections and
guidance for periradicular injections in the lumbar spine, where
fluoroscopy is the current standard,” said Dr. Von Jako. “Ultrasound can
be utilized early in fluoroscopic procedures to identify and access an
arterial lumen with decent anatomical features within more traditional
locations and enable nontraditional regions with less obvious external
landmarks to be found, perhaps in patients with nonpulsatile blood flow
or those with anatomical changes due to previous surgeries or various
Dr. Von Jako also noted that in the peripheral
vascular area, interventionalists rely on fluoroscopy to track and get a
needle or catheter tip into a blood vessel. “Ultrasound assistance here
in combination with a fluoroscopic-guided catheter procedure can be
useful,” said Dr. Von Jako.
Ultrasound is also useful for
enabling hemodialysis access or access to various vessels for
endovascular interventions. “By combining [ultrasound] with a C-arm, it
may assist in facilitating interventional procedures mainly through the
identification of soft tissues, blood vessels, and nerves, without
exposing patients and personnel to the low levels of pulsed radiation,
and by carefully displacing some fluoroscopic steps, the possibility to
perform continuous imaging, and the visualization of the fluid injected
in a real-time fashion,” said Dr. Von Jako.
A recent study
compared fluoroscopic C-arm guidance to ultrasound guidance in patients
undergoing retrograde femoral artery cannulation.3 The study
demonstrated that 30% of a patient subgroup had a higher bifurcation, in
which a reduction in vascular complications were achieved using
ultrasound and with markedly better first-pass cannulation rates using
fewer tries in less time.
“So ultrasound is promising, as it
could be used to speed up cannulation attempts in some choice access
sites, which include the femoral, radial, and brachial access areas; the
axillary area under the armpit; and these areas that could benefit
significantly from ultrasound when you are doing a procedure where you
are going to guide a catheter with fluoroscopy. So it can be a good
substitute for some steps that use fluoroscopy,” said Dr. Von Jako.
combined use of fluoroscopy and 3-dimensional (3D) cardiac ultrasound
is gaining acceptance in a variety of cardiovascular and vascular
procedures. Philips Healthcare just released EchoNavigator, (Figure 2) a
live image-guidance tool to help interventionalists perform minimally
invasive structural heart disease repairs by providing an integrated
view of fluoroscopy and 3D ultrasound images.
In reference to
GE’s combined fluoroscopy-ultrasound unit, Dr. Von Jako noted, “Having
an additional modality such as ultrasound close at hand, with the base
C-arm platform with [the same] look and feel interface, provides value
to the interventionalists. This integrated platform increases the ease
and operative workflow.”
Fluoroscopy: Watch your pulse rate
effective approach to lowering dose is to establish protocols using low
pulse-rate fluoroscopy. Doctors at Johns Hopkins Hospital, Baltimore,
MD, who led 2 clinical trials involving intra-arterial chemotherapy,
took steps to reduce radiation dose exposure to staff and their
pediatric patients—who are particularly susceptible to the effects of
“Reducing radiation dose exposure is critical not only
for patients but also for the staff who perform the procedures. There
is an attainable balance between reducing radiation dose while
maintaining patient safety and image quality. Clinicians can achieve
this by going back to the basics of physics and fluoroscopy, and
tailoring the examination to the individual patient. I routinely use
fluoroscopic pulse rates of 3 pulses/sec for children and 3 or 4
pulses/sec for adults, without any compromise in patient safety or image
quality,” said Monica S. Pearl, MD, DABR, an Assistant Professor and
Interventional Neuroradiologist at Johns Hopkins Hospital.
Pearl was the Principal Investigator on a recent trial treating
retinoblastoma and another study on recurrent diffuse intrinsic pontine
gliomas (DIPG). In both studies, chemotherapy was delivered locally
either through the ophthalmic artery for retinoblastoma or the basilar
artery for DIPG. Because these are rare tumors in children, doctors
applied low-dose protocols.
“We have been able to significantly
reduce radiation exposure to these children by removing the x-ray
scatter grids and applying specifically designed pediatric protocols
using low pulse-rate fluoroscopy, 2 or 3 pulses per second (pulse/sec),
rather than default rates, which are much higher, by using low
pulse-rate roadmaps at 4 pulse/sec; and setting up variable frame rates
for digital subtraction angiography (DSA), starting frame rates at 2
frames per second (frames/sec),” said Dr. Pearl. “In fact, the last
intra-arterial chemotherapy treatment for retinoblastoma, which involves
catheterizing the ophthalmic artery via a transfemoral approach, was
performed with a fluoroscopy time of 2.4 minutes and a total delivered
dose of 3.3 mGy.”
“Published radiation doses from diagnostic cerebral angiograms range from 350 to 4100 mGy.4-7
The delivered dose from a diagnostic cerebral angiogram can vary
widely, but is for a large part dependent on operator technique and
equipment. The physician performing the examination must make a
conscious effort to employ techniques that aim to reduce radiation dose.
These maneuvers are simple to apply and result in substantial dose
savings to patients and staff,” said Dr. Pearl.
conducted the trials using fluoroscopy and DSA on the Artis Zee system
from Siemens Healthcare (Figure 3), but used ultrasound guidance for
difficult femoral artery access. They created low-dose 3D DSA protocols,
routinely used for the evaluation of intracranial aneurysms.
data provide crucial information on aneurysm morphology and are
imperative for determining endovascular or neurosurgical treatment
options. One of the lower-dose 3D DSA protocols delivered 32% less dose
than the standard protocol without compromising accuracy or image
quality. There was no perceptible difference in image quality,” she
In addition, the Artis Zee system provides
Combined Applications to Reduce Exposure (CARE), settings that help
users to control pulsed fluoroscopy, fully-automatic exposure, automated
copper filter settings for reduced skin dose, radiation-free
positioning of collimators, radiation-free positioning of the system,
and dose monitoring and documentation.
“In the last couple of
years, with the Artis Zee and CARE features on the system, we have seen a
significant drop in our radiation doses. The radiation doses we see
today on our exam protocols are half of what they were a few years ago.
This can be attributed to improvements in technology, increased
radiation awareness, and support from the engineers who are willing to
work with us and modify our protocols,” said Dr. Pearl.
added, “When creating lower dose protocols, it is critical to maintain
diagnostic image quality and communicate effectively with your
engineers. Siemens really does share this responsibility of reducing
radiation dose and has been fully supportive in creating and modifying
our adult and pediatric protocols.”
Dose control throughout treatment
efficiency and combined technologies may reduce fluoroscopy or CT time,
managing dose across the treatment cycle is critical.
dependence on fluoroscopy is increasing with the demand for less
invasive procedures and emerging new techniques,” said Dr. Von Jako.
such technique is liver embolization (radioembolization), a standard
palliative treatment for liver cancer, the fifth most-common cancer in
men and the seventh most-common cancer in women.9 Throughout
the course of treatment, however, multiple rounds of imaging are
employed for treatment staging, planning, guidance, and follow up. Plus,
the procedure itself uses radiation to kill the tumor. Therefore, if
the benefits of liver embolization outweigh the risks of radiation
exposure, doctors need to focus on how to best manage the dose.
Goldstein, MD, Vascular and Interventional Radiologist, Maricopa
Medical Center, Phoenix, AZ, has found tumor therapy very effective,
particularly when the disease is at an early stage, where there is a
solitary lesion, or when the patient would otherwise not be a good
candidate for surgery or chemotherapy. “You can have quite a lot of
benefit with a very simple treatment, with a quick recovery time, and
low risk using image guidance,” he said.
with an angiogram to map the vasculature of the abdomen and plan
therapy delivery. A CT scan is then administered to determine the size
of the tumor or percentage of involvement of the liver to calculate the
dose needed to treat the tumor. “During the treatment procedure, we need
to get the catheter in place, and we use angiography to see how the
blood is flowing as we deliver the microspheres. There is then also
follow-up imaging with CT, MRI, or PET,” Dr. Goldstein explained.
minimize the use of fluoroscopy, Dr. Goldstein and his team use new
digital road mapping technology to help guide the catheters and wires.
Healthcare, for example, introduced FlightPlan for Liver, a
treatment-planning process for liver embolization. The physician selects
the tip of the catheter and a hypervascular tumor on a 3D image, and
lets the software highlight the vessels traveling from the catheter to
the lesion. The highlighted vessels can then be used as a roadmap with
the Innova Vision application, by superimposing the map on the live
fluoroscopic image for the to doctor guide the catheter into the target
artery. Interventionalists can identify the tumor-feeding vessels and be
more selective when planning liver embolization.
pointed out that because radioembolization delivers a highly
concentrated volume of radiation to the tumor site, it is less harmful
to healthy surrounding tissue than either external beam radiation or
The radioactive particles used in
radioembolization emit beta radiation, which has a mass nearly as heavy
as an electron. “Because it has some mass, the radiation is absorbed in
the tissue before it travels or penetrates too far. This energy is
deposited within 1 or 2 mm from where the spheres are concentrated, so
you’re delivering a really high dose of radiation just to where the
tumor is and not a significant amount to the whole liver,” said Dr.
Goldstein. “With external beam radiation, even if you’re fractionating
the dose and delivering it from multiple directions, you are still
delivering a very high dose of radiation to the normal liver, which is
He added, “Compared to chemoembolization,
radioembolization maximizes the amount of radiation dose you’re giving
to the tumor, while minimizing the radiation dose to the patient, so
that you have the best of both worlds.”
of all specialties, demand is growing for automated dose monitoring,
optimization, display, and traceability of work. This year, GE
Healthcare announced it is introducing DoseMap, available on GE’s Innova
IGS 540 platform, an image-guided system with a 41-cm × 41-cm detector
for vascular and interventional imaging. The DoseMap monitoring solution
displays live cumulative patient dose levels and offers the operator
the chance to change dose delivery, to help clinicians better monitor
the dose and, in turn, to improve patient care by empowering clinicians
to reduce/amend dose levels. GE also offers DoseWatch, a multimodality
dose tracking and reporting solution.
Also new is an x-ray tube
technology in both the Artis Q and Artis Q.zen (both pending 510(k)
clearance) by Siemens. These angiography systems are engineered to help
physicians identify small vessels up to 70% more accurately than with a
conventional x-ray tube technology. The Artis Q.zen combines this x-ray
source with a new detector technology and can use doses as low as half
the standard levels applied in angiography, which is particularly useful
during longer interventions.
Putting ALARA into practice
benefits of minimally invasive procedures may outweigh the risks of
radiation exposure, but the entire clinical team should still take steps
to minimize radiation exposure to levels that are as low as reasonably
“Whenever ionizing radiation is used in
diagnostic imaging procedures, such as in CT, x-ray or angiography, we
always strive for the ALARA standard with regard to the exposure to
patients and the health care team,” noted Dr. Goldstein.
education on the basics of mobile and fixed-room C-arm safety is a
must. “Radiology technologists are a key part in managing the C-arm
usage and establishing good communication with the physician on when to
anticipate the next clear shot—that helps lower the amount of potential
images taken,” Dr. Von Jako stressed. “Additionally, not just the
radiology technologists need to be trained to use the C-arms but also
the physicians, as they too may be functionally operating a C-arm at
some degree, and more states are requiring certifications for physicians
to operate a C-arm.”
Following basic safety guidelines is
critical to dose safety. Adequate maintenance and usage of wraparound
lead aprons at least ½-mm in diameter can cut down exposure to the user,
along with a thyroid collar and special lead-lined glasses, which
improve protection, especially over cumulative exposures.
the basics, such as how far away to stand from the beam and placing the
beam source under the table, helps to better protect the user over a
career of use. Positioning the C-arm image intensifier closer to the
patient minimizes external exposure, minimizes patient skin exposure
while creating a better image, and protects the physician and staff.
the image intensifier further away from the patient allows for greater
scatter radiation and as much as 80% of the scatter can come off the
patient. But if you step 3 or more feet away, it cuts down the amount of
dose exposure significantly by a factor of 4,” said Dr. Von Jako.
useful method is using pulse mode at 15 frames per second, instead of
high-level fluoroscopy at 30 frames per second. The amount of dose that
can be reduced using pulse mode versus a high level beam can be up to
30% or more. If you collimate the beam, narrowing it down to the
field-of-view you want, this feature cuts down the dose to the patient,
as does another feature called last image hold (LIH), allowing for a
review of recent anatomical images without taking extra shots. These are
advantages that already exist in C-arms. Adding an ultrasound option to
this may help in certain procedures and circumstances to
further the opportunity in reducing x-ray time,” he said.
Goldstein’s team uses real-time dose monitoring that staff can see
onscreen during procedures. Another tactic is minimizing fluoroscopy
“By applying these simple techniques,” said Dr. Pearl, “you
can answer the clinical question, perform a good study, and
significantly reduce your dose.”
- Miller, DL, Vañó, E, Bartal G. Occupational radiation protection in
interventional radiology: A joint guideline of the Cardiovascular and
Interventional Radiology Society of Europe and the Society of
Interventional Radiology. J Vasc Interv Radiol. 2010;21:607–615.
- Radiation safety. Cardiovascular and Interventional Radiological
Society of Europe (CIRSE). http://www.cirse.org/index.php?pid=153.
Accessed February 28, 2013.
- Seto AH, Abu-Fadel MS, Sparling JM, et al. Real-time ultrasound
guidance facilitates femoral artery access and reduces vascular
complications: FAUST (Femoral Arterial Access With Ultrasound Trial). JACC Cardiovasc Interv. 2010 Jul;3:751-758. doi: 10.1016/j.jcin.2010.04.015.
- Mooney RB, McKinstry CS, Kamel HA. Absorbed dose and deterministic effects to patients from interventional neuroradiology. Br J Radiol. 2000;73:745-751.
- Struelens L, Vanhavere F, Bosmans H, et al. Skin dose measurements
on patients for diagnostic and interventional neuroradiology: A
multicentre study. Radiat Prot Dosimetry. 2005;114:143-146.
- Vano E, Gonzalez L, Fernandez JM, Guibelalde E. Patient dose values in interventional radiology. Br J Radiol. 1995;68:1215-1220.
- Theodorakou C, Horrocks JA. A study on radiation doses and irradiated areas in cerebral embolisation. Br J Radiol. 2003;76:546-552.
- Pearl M, Katz Z, Messina S, et al. Diagnostic quality and accuracy
of low dose 3D DSA protocols in the evaluation of intracranial aneurysms
[abstract]. In: 50th Annual Meeting of the American Society of Neuroradiology; New York, NY. April 23-26, 2012:p.249, abstract nr 0-511.
- Liver cancer incidence and mortality worldwide in 2008 summary.
Globocan 2008. http://globocan.iarc.fr/factsheets/cancers/liver.asp.
Accessed March 4, 2013.