Open Journal of Radiology, 2013, 3, 143-151
http://dx.doi.org/10.4236/ojrad.2013.33024 Published Online September 2013 (http://www.scirp.org/journal/ojrad)
Evaluation of a Suspended Person al Radiation Protection
System vs. Conventional Apron and Shields in Clinical
Clare Savage1*, Thomas M. Seale IV2, Cathryn J. Shaw2, Bruner P. Angela2,
Daniel Marichal2, Chet R. Rees2
1River City Imaging, San Antonio, USA
2Department of Radiology, Medical Center, Baylor University, Dallas, USA
Received May 16, 2013; revised June 16, 2013; accepted June 23, 2013
Copyright © 2013 Clare Savage et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Purpose: This clinical study compares conventional lead aprons and ancillary shields to a functionally weightless per-
sonal overhe ad-supported system with exp anded coverage. Materials and Methods: Primary operators performed pro-
cedures (N = 126, fluoroscopy minutes = 120 9) using one of 2 methods of radiation pr otection and wearing do simeters
on multiple body locations. Method “LAS” (Lead-Apron+Shields): lead skirt, vest, thyroid shield, with 100% use of
under-table shield, side shield, and mobile suspended lead-acrylic shield. Method “Zgrav”: ZeroGravity system (CFI
Medical Solutions) with variable use of shielding. The studied early model moving with the operator had a curved
lead-acrylic head shield (0.5 mm Pb) and expansive lead apron (0.5 - 1.0 mm Pb) that covered leg to distal calf and
proximal arm to elbow, and a drape th at permitted sterile entry an d exit. Study was institutional review board approv ed
and HIPPA-compliant. Results: Measured with a sensitive electronic dosimeter, eye exposures were 99% (P < 0.001)
reduced for Zgrav with upgraded face shield vs. LAS, regardless of use or non-use of suspended shield with Zgrav.
With optically stimulated luminescence (OSL) dosimeters, operator exposures, standardized to minutes of fluoroscopy
and Fluoroscopic Patient Dose Area Product, were reduced by 87% - 100% for eye & head, neck, humerus, and tibia
(Zgrav vs. LAS) . Overall eye & head expo sure reduction for entire stud y was 94%. Non-equiv alence of torso exposures
was not demonstrated. A brief user survey showed ergonomic advantages of Zgrav. Conclusion: Compared to conven-
tional lead aprons with shields, the suspended system provided superior operator protection during interventional fluo-
roscopy, allowing operators to perform procedures without potentially obstructive shields.
Keywords: Radiation Protection; Radiation; Fluoroscopy
The growth in utilization and complexity of fluoro scopic
procedures has increased workload for interventionalists,
resulting in cumulative radiation doses and orthopedic
strains that can be limiting or career ending [1-11]. De-
spite suffering significantly increased neck and back pain,
lost work time, and cervical disc herniations (P < 0.01)
, exposures remain excessive as demonstrated by one
operator receiving the equivalent of 60 skull films during
1 month’s practice using available shielding . Data
suggest that cataract formation is occurring at exposures
less than previously believed with a low or absent thre-
shold dose [5-10]. Lead glasses are often limited to an
attenuation factor of 2 - 3 times for the eyes due to angle
of coverage relative to the radiation path and backscatter
from the unprotected head to the eyes, and are considered
heavy, prone to fogging, and incompatible with correc-
tive eyewear [6-14]. Lead glasses do not protect the cer-
vical bone marrow and nervous system where even mod-
erate doses of radiation are associated with elevated in-
cidence of nervous system tumors [1,11,15-17]. Ancil-
lary protection including table shields, hanging lead-
acrylic shields, and attenuating drapes reduce scatter
when positioned properly, but are sometimes awkward
and difficult to position due to interferen ce with op erator,
patient, or image receptor, especially with oblique pro-
jections where scatter may increase several-fold [1,5,6,
18-21]. These shields produce a discontinuous barrier
opyright © 2013 SciRes. OJRad
C. SAVAGE ET AL.
that is not always in the path of scatter and may not be
used without a lead apron. As stated by the recent Joint
Inter-Society task Force on Occupational Hazards in the
Interventional Labo ratory, “Intervention al physicians and
their professional societies, working together with indus-
try, should strive toward the ultimate definition of
ALARA as close to a zero radiation exposure work en-
vironment as possible, and ultimately eliminate the need
for personal protective apparel and prevent its orthopedic
and ergonomic consequences” .
The suspended personal radiation protection system
was designed to enhance radiation protection and im-
prove ergonomics and comfort by eliminating weight on
the operator, while maintaining a neutral or positive ef-
fect on task accomplishment. The purpose of this study
was to assess radiation doses to actual operators during
interventional cases using either th e suspended system or
conventional aprons and ancillary shielding.
2. Materials and Methods
Several operators performed procedures in three Inter-
ventional Radiology suites (Siemens, Munich, Germany)
equipped with 3 ancillary shields (Figure 1), including a
mobile suspended lead-acrylic shield, an under-table
shield, and a side shield that extends upwards from the
under-table skirt (Mavig, Munich, Germany). Primary
operators wore multiple dosimeters (described below)
while using one of two methods of operator protection:
“LAS” (lead apron + shields) and “Zgrav” (suspended
radiatio n protect i on system).
Method LAS utilized a conventional skirt and vest,
thyroid collar, and 100% use of all 3 types of ancillary
shields (Figure 1, Ta ble 1 ). Most wrap-around skirts and
vests were 0.5 mm Pb in front (1 mm in frontal area of
overlap) and 0.25 mm Pb in back. One used in 6 of 35
LAS cases was 0.25 mm in the front and back, with 0.5
mm Pb in the frontal overlap area. Thyroid shields were
0.5 mm Pb equivalent.
Method Zgrav utilized the suspended personal radia-
tion protection system (ZeroGravity, CFI Medical Solu-
tions, Fenton, MI) with or without ancillary shields ac-
cording to operator discretion (Figure 2, Table 1). Use
of Zgrav vs. LAS was not controlled. The test system
was early model commercial stock approved device. This
overhead-suspended system had a curved lead-acrylic
head shield (0.5 mm Pb), and lead apron extending to the
distal calves (1 mm Pb centrally [63.5 × 69.3 cm], 0.5
mm peripherally) with 0.5 mm Pb arm flaps extending to
the elbows. A sterile plastic drape permits quick entry
and exit while maintaining sterility. Newer models use
thicker Pb throughout the apron (1 mm Pb).
Operators used patient-exposure reduction techniques
including reduction of air gaps, pulsed fluoroscopy, col-
limation, minimization of fluoroscopy times, minimize-
Fi gure 1. Ancillary shielding consisting of under-table shield,
side shield, and mobile suspended lead-acrylic shield were
used aggressively in all LAS procedures and sometimes
with Zgrav as depicted in Table 1.
Table 1. Ancillary shields used (proportion of procedures).
Pb-acrylic Side-table Under-table
All Phases 100% 100% 100%
Phase I <50% <50% 100%
Eye 61% >50% 100%
Wrist 0% >50% 100%
tion of severely obliqued or lateral receptor angles.
Hands are never placed in the direct beam. During most
cases, LAS and Zgrav operators stood in the control
room or at a distance behind a floor-supported mobile
shield during digital subtraction angiog raphy (DSA ). The
patient was positioned to allow the operator to work at
the right side of the table when possible.
Since the left-anterior side of the operator is expected
to receive the highest doses, dosimeters were placed ac-
cordingly (Figure 3) . The operator wearing the do-
simeters was always in the primary operator position.
Optically stimulated luminescence (OSL) dosimeter
badges (Landauer Luxel, Glenwood, IL) were placed on
Copyright © 2013 SciRes. OJRad
C. SAVAGE ET AL.
Copyright © 2013 SciRes. OJRad
Figure 2. Zerogravity device in clinical use. Top left (a) Device provides shielding without the challenges of the suspended
shield when using left anterior oblique tube angulation during body intervention. Operator looks over the face shield to the
monitor. Top right (b) Device mores and turns in the field with the operator. Bottom left (c) Operator is able to lean over
large patient. Bottom right (d) operator steps out of device to perform delicate work at back table, and can then re-engage the
device for fluoroscopy while maintaining sterility.
Dosimeters were worn when fluoroscopy was antici-
pated to exceed 2 minutes. Inclusion into this report oc-
curred when operator wearing badges was the primary
operator for the entire procedure without change in posi-
tion with another operator, and when procedural data and
dosimeter data were available. OSL badge data was ex-
cluded for 2 sets that were found, after exposure, to have
been positioned incorrectly.
operators prior to donning the LAS or Zgrav, in the loca-
tions depicted in Figure 3. Three to five control badges
were mailed for readings with each set of badges, and
their mean was subtracted from the others to correct for
background radiation or possible x-ray examination dur-
The data in this report is categorized into 2 phases,
differing by time and dosimeter type. For more sensitive,
per-case determinations of exposure, a recently calibrated
electronic direct dosimeter (EDD-30, Unfors, Billdal,
Sweden) was acquired for Phase II. It has a small sensor
on a wire that could be placed nearly anywhere, provid-
ing readings as low as 1 nSv. It may be reset for each
case so there are no cumulative effects of natural back-
ground radiati on.
Procedure type, fluoroscopy time, and Total Patient
Dose-Area-Product (uSv/Gycm²) as measured by the
imaging equipment were available for each case. Total
Patient Dose-Are a-Product (D AP) includes DAP fr om all
sources including fluoroscopy and DSA. Determination
of DAP due to fluoroscopy only (Fluoroscopic Patient
DAP) was also available in the last 27 of 67 procedures
C. SAVAGE ET AL.
in Phase I and all 50 procedures in Phase II as the study
was consolidated into one suite that provided this infor-
mation. In this study, Fluoroscopic Patient DAP provides
a better correlate for pertinent scattered radiation due to
the operators’ habits of exiting the area during DSA (see
Discussion). Operator exposure results were standardized
to fluoroscopy time, Total Patient DAP, and Fluoro-
scopic Patient DAP.
A variety of procedures included: arterial diagnostic
(lower extremity, renal, visceral, bronchial, subclavian),
arterial interventional (hepatic in fusion, peripheral, renal,
and visceral stent placement, chemo-embolization, em-
bolization of pulmonary and muscular arteriovenous mal-
formations, embolization of visceral, uterine, and trans-
lumbar aortic arteries), venous interventional (trans-
jugular and trans-femoral inferior vena cava [IVC] filters,
IVC percutaneous transluminal angioplasty, transjugular
liver biopsy, transjugular intrahepatic portosystemic
shunt, permcath placements), and non-vascular interven-
tional (biliary, nephrostomy, fiducial placements, abscess
drain, gast r i c tube).
Details of the phases follow:
Phase I: Operators performed 67 procedures using
Zgrav (n = 32) or LAS (n = 35) wearing multiple OSL
dosimeter badges (Figure 3). Study parameters are de-
picted in Tables 1 and 2. For Zgrav, the mobile sus-
pended and side shields were used in <50% of proce-
dures, and the under-table shield was used 100% of the
time. All 3 ancillary shields were used in 100% of LAS
procedures. The Zgrav face shield was upgraded to a
more comprehensive, taller version (Figure 2) for the
latter 13 Phase I Zgrav patients and throughout Phase II.
Phase II: The data obtained with the Unfors EDD-30
electronic dosimeter constitutes Phase II. The sensor was
worn on the eyeglasses frame near the left eye, or on the
dorsum of the left wrist (Figure 3, Table 2). The sus-
pended lead-a crylic shie ld was alw ays used for LAS, an d
used in 61% and 0% with Zgrav when the dosimeter was
worn on the eye and wrist, respectively (Table 1 ). Only 1
designated suite was used for phase II, minimizing un-
controlled variables. The upgraded taller face shield
(Figure 2) was used throughout phase II. The use of the
EDD-30 electronic dosimeter in conjunction with the
OSL badges in some procedures created partial overlap
between Phases I and II (12 procedures, 82 minutes of
Evaluation of ergonomics: Four operators with exten-
sive use of the device, including 3 study participants (CS,
DM, and CJS) completed a brief survey regarding the
ergonomics of the device.
Figure 3. OSL badge dosimeter locations. Asterisks depict
the two possible locations for EDD-30 electronic dosimeter
in phase II.
Table 2. Other study parameters.
Patient DAP (Gy cm2)
Dosimeter Type Procedures (N) Operators (N) Minutes FluoroscopyDAP Fluoroscopy DAP Total
Phase I OSL badges 67
Zgrav 32 3 307 47.486* 267.801
LAS 35 3 307 50.561** 318.839
Phase II EDD-30
Zgrav 28 2 329 103.884 281.364
LAS 22 3 122 47.734 222.364
Zgrav 15 2 186 83.316 414.680
LAS 7 2 40 22.083 131.520
*Data available for last 13 cases, 112 minutes of fluoroscopy. **Data available for last 14 cases, 132 minutes fluoroscopy.
Copyright © 2013 SciRes. OJRad
C. SAVAGE ET AL. 147
Ninety five percent confidence intervals for OSL data
were determined based on manufacturer specifications
(95% CI range is +15%) and control readings. In Phase II,
one tailed unpaired T-test was used to compare Zgrav
and LAS results, and two tailed unpaired T-test was used
to compare Zgrav + mobile suspended lead-acrylic shield
vs. Zgrav without this shield. Disclosure: CRR has a fi-
nancial interest in the Zerogravity device.
Total N = 126, fluoroscopy = 1209 minutes. Eye expo-
sure can be reported for all procedures because it was the
only site measured in both phases. It was reduced by
94% for Zgrav compared to LAS (means = 0.142 and
2.401 uSv/minute fluoroscopy, respectively). Figure 4
shows how face shield protects eyes without obstructing
line of sight to the monitor.
Phase I: Phase I information and results are depicted in
Tables 1, 2, Figures 5(a) and (b). Operator exposures
for several body locations were considerably higher for
LAS than Zgrav, despite the consistent use of all ancil-
lary shields with LAS (Figures 5(a) and (b)). Operator
exposures, standardized to minutes of fluoroscopy (Fig-
ure 5(a)) and Fluoroscopic Patient Dose Area Product
(Figure 5(b)), were reduced by 87% - 100% for eye &
head, neck, humerus, and tibia (Zgrav vs. LAS). Torso
and back exposures were low for both modalities (all
95% confidence intervals include 0) so reductions were
not calculated. Accurate comparisons for these areas, to
determine presence or absence of effect of the 1.0 mm Pb
would require data collection on a larger scale. Upper
forehead exposures were reduced by both Zgrav face-
shield models compared to LAS, however the later model
shield was superior (58% reduction for early model [N =
19], 92% reduction for later model [N = 13]).
Results standardized to minutes of fluoroscopy (Fig-
ure 5(a), entire Phase I) were similar to results stand ard-
ized to fluoroscopic patient DAP (Figure 5(b), last 27
Figure 4. Head shield is in path of scatter but not in line of
sight to monitor.
patients of Phase I). The similar overall appearances of
Figures 5(a) and (b) shows apparent consistency of re-
sults for both standardization schemes with regard to
exposure reductions (Zgrav vs. LAS) and body part dis-
Phase II: Information and results for Phase II are seen
in Tables 1, 2, and Figure 5(c). Zgrav provided 99%
reductions in Eye exposures (P < 0.001) compared to
LAS. The highest exposure in the Zgrav group was lower
than the lowest exposure in the LAS group (Figure 5(c)),
despite 100% use of all ancillary shields in the LAS
group (Table 1). Exposures for the 28 Zgrav procedures
were consistently undetectable or barely detectable, with
a mean of 0.007 uSv/Gycm² (range = 0 to 0.04 ± 0.012
SD), vs 0.767 (0.19 to 4.44 ± 1.256) for LAS (P < 0.001).
The strikingly greater variance for LAS compared to
Zgrav indicates less consistent shielding for LAS over a
broad range of procedure types and operator positions.
Finally, Figure 5(c) demonstrates that the use of the mo-
bile suspended lead-acrylic shield did not significantly
impact the eye and head exposure when using Zgrav
(Mean + SD = 0.00796 ± 0.0146 uSv/Gycm² with shield
vs 0.00697 ± 0.0092 without shield, P = 0.14). This
finding for Zgrav differs from widely reported results for
conventional lead aprons where the mobile suspended
shield reduced eye exposures [5,6 ,2 0, 2 1] .
Operator wrist exposures were similar for LAS and
Zgrav (Mean + SD = 2.10 uSv/Gycm2 ± 0.75 vs 2.11 ±
0.76, P > 0.05). Since the mobile suspended lead-acrylic
shield was used in 100% of LAS procedures and 0% of
Zgrav procedures in the wrist group (Table 1), this sug-
gests ineffectiveness of the ancillary shield s for reducing
hand exposures, and that their omission does not increase
exposures. These results were consistent with other re-
ports [20,22,23]. When standardized to Total DAP (in-
stead of fluoroscopic DAP), wrist exposure for all pro-
cedures in Phase II = 0.39 uSv/Gycm².
The ergonomic survey results for the device were as
follows: On a scale of 0 - 5 , “relief of b ack pain normally
experienced with a lead apron with 0 = no relief, and 5 =
complete relief” was a 4 in one person, and not evaluable
in 3 persons due to lack of back pain with lead apron.
Relative to lead apro n, “device comfort” (scale 1 - 5 with
5 = “Much more comfortable” and 1 = “Much less com-
fortable,” and 3 = equal) was 4.75. All responders “al-
ways or nearly always use all 3 ancillary shields when
using lead apron”. Zgrav was considered less “hassle or
obstruction” compared to using all 3 shields and lead
apron (4.75 on scale of 1 - 5 with 1 = Zgrav is much
more obstructive, 5 = Zgrav is much less obstructive, 3 =
equal). Procedure time was felt to be “about equal” for
Zgrav relative to lead apron for all persons (3 on a scale
f 1 - 5). o
Copyright © 2013 SciRes. OJRad
C. SAVAGE ET AL.
Figure 5. a. Operator exposures measured with Optically Stimulated Luminescence (OSL) dosimiters and standardized to
fluoroscopy minutes in phase I. b. Operator exposures me asured with Optically Stimulated Luminescence (OSL) dosimeters
and standardized to fluorosc opic DAP in phase I. c. Operator exposures measured with EDD-30 and standardized to fluoro-
scopic Dose Area Produc t (DAP) in phase II. Substantial reducti ons with Zgrav are seen for both standardization techniqu es
and dosimeter types. Depiction of individual cases shows consistency of Zgrav protection relative to LAS and no apparent
benefit of mobile suspended lead-acrylic shie ld when using Zgrav.
The tested device was developed to provide near com-
prehensive radiation protection sustainable throughout a
spectrum of interventional cases. ZeroGravity differs
from other weightless lead-apron substitutes by combin-
ing additional head shield ing, rapid sterile entry/exit, and
overhead suspension allowing body motion without
floor-base motion [24,25].
The LAS technique, the most broadly studied protec-
tion method, is limited by difficulty maintaining ideal
shielding position during interventional procedures, and
the barrier discontinuity of multiple, separate devices
[1,5,6,18-20]. Alternatively, the ZeroGravity provides a
single continuous enveloping barrier that shields the top
of the head through the lower tibias (broken only by pro-
trusion of the arms through the arm flaps). The device
automatically maintains its position between the scatter
and the operator as the many dynamic factors change.
This effect is demonstrated in Figure 5(c), where ex-
Copyright © 2013 SciRes. OJRad
C. SAVAGE ET AL. 149
treme variability in eye exposures in the LAS group oc-
curred despite aggressive use of the mobile suspended
lead-acrylic shield in all cases, while eye exposures in
the Zgrav group were consistently substantially lower.
These differences are unlikely due to material properties
since both the mobile suspended shield and the Zgrav
face shield use similar Pb-acrylic (0.5 mm Pb).
Combinations of lead apron, attenuating drapes, ac-
cessory shields and glasses have been studied using
phantoms to extrapolate radiation protection theoretically
provided to the practicing interventionalist [13,14, 20-
22,26,27]. Although phantom studies provide prelimi-
nary information, application to clinical practice is prob-
lematic due to many dynamic factors including large
patients, interference with operator’s hands or arms from
accessory shields, and inability to use shielding in certain
image receptor obliquities or operator stances. Results
with phantoms showing significantly reduced eye expo-
sures using shields are not fully corroborated by clinical
studies using the same shielding, with one study docu-
menting high clinical eye doses and recommending pro-
tective eyewear in addition to the suspended shield
[20-23,27-29]. A feasibility study of an earlier prototype
of the suspended personal radiation protection system
using phantoms showed 16 - 78 fold decreases in expo-
sure to various body areas compared to a lead apron due
to thicker lead and greater surface area covered .
Without eye protection, a standard workload could
easily exceed the annual limit of 150 mSv, and could be
further compounded for interventionalists who become
patients and receive additional medical exposures .
The concurrent use of the mobile suspended lead-acrylic
shield produced no detectable differences in eye and
head exposures in the Zgrav group (Figure 5(c)), sup-
porting our current practice of abandoning the cumber-
some suspended shield, and sometimes forgoing the side
shield when obstructive to work. When wearing conven-
tional lead aprons, aggressive use of available ancillary
shields is recommend.
To facilitate comparison across the literature, operator
exposure was standardized to Total Patient DAP, which
is a widely accepted reporting method that reflects the
protective power of the shielding, and minimizes effects
of uncontrolled variables [22,29,32,33]. Similar to our
LAS group, other reports showed high case-to-case vari-
ance of DAP-standardized operator exposures due to the
dynamic factors of clinical practice . Figure 6 shows
our LAS group u sed shielding very eff ectively compared
to other DAP-standardized reports, attributable to rigor-
ous optimization of shielding when not using the Zero-
Further standardization to Fluoroscopic Patient DAP
and strict adherence to data from only the primary op-
erator position p rovide a more pure comparison o f Zgrav
Figure 6. Operator head exposures per Total Patient DAP
in clinical studies with mobile suspended lead-acrylic
shields. LAS group of current study shows exposures in the
low range of similar studies, indicating aggressive use of
ancillary shields with lead aprons by operators in current
study. Zgrav group of current study shows substantially
lower exposures than all studies using conventional means.
Dosimeter location is indicated under each study, and pro-
cedure ty pe is at bottom.
to LAS. Due to the operators’ practice of exiting the area
during DSA, Patient DAP during DSA is irrelevant to
operator exposure, yet accounted for 2.8 times the con-
tribution of Fluoroscopic Patient DAP towards Total Pa-
tient DAP (Table 2). Pure primary operator exposures
are difficult to obtain in teaching institutions and uncon-
firmed in many reports, but are important since secon-
dary operators are farther from the source and partially
shielded by the p rimary operato r, showing relative reduc-
tions of 50% .
DAP Standardized wrist exposures were similar to
other reports. Absence of significant difference between
LAS and Zgrav was unsurprising since neither Zg rav nor
the mobile suspended lead-acrylic shield protect the
hands or forearms [20,22,23]. In keeping with ALARA,
we perform 100% of procedures without ever placing the
fingers in the direct beam.
Detailed analysis of the device’s ability to improve
operator comfort and relieve strain is beyond the study’s
scope. However, survey results suggested that, compared
to lead aprons and all 3 ancillary shields, the suspended
personal radiation protection system was more comfort-
able, relieved back pain in the one afflicted responder,
was less obstructive to work effort than the other shields
and did not affect procedure time.
This study has potential limita tions. The wide case va-
riety, representative of an actual interventional practice,
makes cohort matching difficult. The study does not in-
clude all consecutive cases for any operator or lab due
largely to the occurrences of change in operator status
Copyright © 2013 SciRes. OJRad
C. SAVAGE ET AL.
(primary vs. secondary) at a teaching institution resulting
in exclusions. This study was not powered to detect po-
tential differences in under-lead exposures from different
Pb equivalencies for Zgrav vs. LAS. A larger multi-cen-
ter study by Marx, et al., showed that, beside case vol-
ume, double lead thickness was the single largest deter-
minant of under-lead exposure and more important than
ancillary shielding, with 1 mm lead equivalent aprons
resulting in a 2/3 reduction in measured under-lead ex-
posures . Another study showed reductions of 78% to
83% using thicker lead to protect the torso . Finally,
study results may differ for operators who stay in the
area during DSA sequences, receiving higher exposures
with different energy spectra.
In conclusion, the test device significantly reduced ex-
posures for many body areas compared to rigorous con-
ventional shield ing techniques in the clinical settin g. It is
a single, weightless apparatus protecting a great propor-
tion of the body in various operator, patient and tube
configurations. Future studies could include in-depth
evaluation of its ergonomic benefits, and analysis of cost
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