Radiation Exposure of Operators Performing Transesophageal Echocardiography During Percutaneous Structural Cardiac Interventions

JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY

VOL. 71, NO. 11, 2018

CROWN COPYRIGHT ª 2018 PUBLISHED BY ELSEVIER ON BEHALF OF THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION. ALL RIGHTS RESERVED

Radiation Exposure of Operators Performing Transesophageal Echocardiography During Percutaneous Structural Cardiac Interventions James A. Crowhurst, BSC (HONS),a,b Gregory M. Scalia, MBBS, MMEDSCI,a,b Mark Whitby, MSC, PHD,c Dale Murdoch, MBBS,a,b Brendan J. Robinson, BAPPSCI,a Arianwen Turner, BAPPSCI,d Liesie Johnston, BAPPSCI,d Swaroop Margale, MBBS,e Sarvesh Natani, MBBS, MD,e Andrew Clarke, MBBS,f Darryl J. Burstow, MBBS,a,b Owen C. Raffel, MB,a,b Darren L. Walters, MBBS, MPHILa,b

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learner should be able to: 1) state which staff members receive the highest radiation dose during percutaneous structural cardiac intervention pro-

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cedures; 2) compare x-ray C-arm projections and their impact on operator radiation dose; and 3) explain why certain patient, procedural, and environmental factors may affect staff radiation exposure in the cardiac catheter laboratory.

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From the aCardiology Department, The Prince Charles Hospital, Chermside, Queensland, Australia; bUniversity of Queensland,

Dr. Valentin Fuster.

St. Lucia, Queensland, Australia; cBiomedical Technical Services, The Prince Charles Hospital, Chermside, Queensland, Australia; d

Medical Imaging Department, The Prince Charles Hospital, Chermside, Queensland, Australia; eDepartment of Anaesthesia, The

Prince Charles Hospital, Chermside, Queensland, Australia; and the fDepartment of Cardio-thoracic Surgery, The Prince Charles Hospital, Chermside, Queensland, Australia. The authors have reported that they have no relationships relevant to the contents of this paper to disclose. Manuscript received August 22, 2017; revised manuscript received January 8, 2018, accepted January 11, 2018.

ISSN 0735-1097/$36.00

https://doi.org/10.1016/j.jacc.2018.01.024

Crowhurst et al.

JACC VOL. 71, NO. 11, 2018 MARCH 20, 2018:1246–54

Radiation Dose to TEE Operators

Radiation Exposure of Operators Performing Transesophageal Echocardiography During Percutaneous Structural Cardiac Interventions James A. Crowhurst, BSC (HONS),a,b Gregory M. Scalia, MBBS, MMEDSCI,a,b Mark Whitby, MSC, PHD,c Dale Murdoch, MBBS,a,b Brendan J. Robinson, BAPPSCI,a Arianwen Turner, BAPPSCI,d Liesie Johnston, BAPPSCI,d Swaroop Margale, MBBS,e Sarvesh Natani, MBBS, MD,e Andrew Clarke, MBBS,f Darryl J. Burstow, MBBS,a,b Owen C. Raffel, MB,a,b Darren L. Walters, MBBS, MPHILa,b

ABSTRACT BACKGROUND Transesophageal echocardiography operators (TEEOP) provide critical imaging support for percutaneous structural cardiac intervention procedures. They stand close to the patient and the associated scattered radiation. OBJECTIVES This study sought to investigate TEEOP radiation dose during percutaneous structural cardiac intervention. METHODS Key personnel (TEEOP, anesthetist, primary operator [OP1], and secondary operator) wore instantly downloadable personal dosimeters during procedures requiring TEE support. TEEOP effective dose (E) and E per unit Kerma area product (E/KAP) were calculated. E/KAP was compared with C-arm projections. Additional shielding for TEEOP was implemented, and doses were measured for a further 50 procedures. Multivariate linear regression was performed to investigate independent predictors of radiation dose reduction. RESULTS In the initial 98 procedures, median TEEOP E was 2.62 mSv (interquartile range [IQR]: 0.95 to 4.76 mSv), similar to OP1 E: 1.91 mSv (IQR: 0.48 to 3.81 mSv) (p ¼ 0.101), but significantly higher than secondary operator E: 0.48 mSv (IQR: 0.00 to 1.91 mSv) (p < 0.001) and anesthetist E: 0.48 mSv (IQR: 0.00 to 1.43 mSv) (p < 0.001). Procedures using predominantly right anterior oblique (RAO) and steep RAO projections were associated with high TEEOP E/KAP (p ¼ 0.041). In a further 50 procedures, with additional TEEOP shielding, TEEOP E was reduced by 82% (2.62 mSv [IQR: 0.95 to 4.76] to 0.48 mSv [IQR: 0.00 to 1.43 mSv] [p < 0.001]). Multivariate regression demonstrated shielding, procedure type, and KAP as independent predictors of TEEOP dose. CONCLUSION TEE operators are exposed to a radiation dose that is at least as high as that of OP1 during percutaneous cardiac intervention. Doses were higher with procedures using predominantly RAO projections. Radiation doses can be significantly reduced with the use of an additional ceiling-suspended lead shield. (J Am Coll Cardiol 2018;71:1246–54) Crown Copyright © 2018 Published by Elsevier on behalf of the American College of Cardiology Foundation. All rights reserved.

P

procedures,

performing fluoroscopically guided cardiac proced-

guided by fluoroscopy for structural pathology

ures (4–6), none of these studies were inclusive of

of the heart, are now commonplace, and

radiation dose to TEE operators in this environment.

ercutaneous

interventional

procedures such as transcatheter aortic valve replace-

Primary operators, usually the cardiologist per-

ment (TAVR) offer an alternative treatment option

forming the procedure, have tableside and ceiling-

to

procedures

suspended lead shields in place to protect them

and many others, including left atrial appendage

open-heart

surgery

from the harmful effects of radiation. These are usu-

occlusion

repair/

ally only in place on the right side of the procedure

implantations, require guidance with transesophageal

table, where the primary operator and their assistant

and

(1).

transcatheter

These mitral

valve

echocardiography (TEE) in addition to fluoroscopy (2,3).

stand. There is often no specific additional protection

This

and/or

installed at the head end or left side of the procedure

echocardiologist who operate the TEE probe and

table where the TEE operator (TEEOP) would stand.

console to the harmful effects of scattered ionizing

Recent guidelines have highlighted the risks of radi-

radiation. Although recent publications have high-

ation to TEEOP and the lack of evidence surrounding

lighted

radiation dose to TEEOP (7). All staff working in this

exposes

the

the

risks

echocardiographer

of

radiation

to

the

staff

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Radiation Dose to TEE Operators

ABBREVIATIONS

environment are monitored with optically

dosimeter to a computer. The personal dose equiva-

AND ACRONYMS

stimulated luminescent dosimeters that are

lent H p(10) (mSv) is then calculated by the application

interrogated on a monthly basis. Although all

of an appropriate algorithm, by the computer, which

staff wear these dosimeters, they do not

takes into consideration the typical photon energy

show how much radiation dose each staff

incident on the dosimeter. The IDD has a broad dose

member may receive on a case-by-case basis.

and energy response of 0.01 mSv to 5 Sv and 5 KeV to

With the lack of evidence surrounding this

6 MeV, respectively (NVLAP lab code 100555-0 for

ANA = anesthetist BMI = body mass index E = effective dose IDD = instantly downloadable dosimeter

issue, this study sought to measure the ra-

IQR = interquartile range

ANSI N13.11-2009 categories IA, IIA, and IIC).

diation dose to TEEOP during percutaneous

The personal dose equivalent H p (d) is defined as

interventional procedures that require TEE

the dose equivalent in soft tissue below a specified

guidance and compare their dose to other

point on the body at an appropriate depth. For

members of the multidisciplinary heart team.

penetrating x-rays, this depth is 10 mm and therefore

Secondly, we sought to investigate proce-

denoted as Hp (10). H p(10) is normally considered to

dural factors that would have an impact on

provide a conservative or close approximation to

OP2 = secondary operator

total radiation dose and the TEEOP dose.

effective dose (E) (11). However, because the IDD was

PA = posteroanterior

Additional lead shielding was also imple-

located outside the protective apron, Hp (10) in this

RAO = right anterior oblique

mented for the TEEOP, and the effectiveness

case would significantly overestimate effective dose.

TAVIS = transcatheter aortic

of the shielding solution was measured.

The results in H p(10) were therefore converted to

KAP = Kerma area product LADI = left atrial device implantation

LAO = left anterior oblique OP1 = primary operator

valve replacement or SEE PAGE 1255

intervention using open surgical access

TAVR = transcatheter aortic

METHODS

effective dose, by dividing the value by 21, in line with the methodology outlined in the NCRP 168 document (12). This conversion allows for the dose across key staff to be compared along and with other

valve replacement

studies.

TEE = transesophageal

This single, tertiary center, observational

echocardiography

study, conducted between September 2014

TEEOP = transesophageal

and November 2015, included all x-ray–

RADIATION PROTECTION. All personnel working in

echocardiography operator(s)

guided procedures requiring TEE guidance in

the hybrid theatre wore a lead apron or apron and

a single hybrid operating theatre, equipped with a

skirt with a minimum of 0.25 mm of lead-equivalent

contemporary cardiovascular x-ray system (Siemens

properties at the back and 0.5 mm at the front. A

Artis Zee ceiling, Siemens Healthcare, Erlangen,

collar for thyroid protection was also worn. In

Germany).

addition, there was the option for staff to wear a lead-

Four key roles (primary catheter operator [OP1],

lined theatre hat and lead goggles with lead-

secondary catheter operator [OP2], anesthetist [ANA],

equivalent properties of 0.5 mm. OP1 and OP2 stood

and the TEEOP) who were in attendance wore an

on the patient’s right side for all procedures, with the

instantly downloadable dosimeter (IDD) (Instadose,

exception of surgical access TAVR procedures, where

Mirion Technologies, San Ramon, California) for the

OP1 stood either on the patients’ left side (transapical

duration of each procedure. The IDD was worn on the

access TAVR) or at the head of the procedure table

outside of the lead thyroid protection collar by all key

(transaortic TAVR procedures). OP1 and OP2 were

staff, except for the TEEOP, who attached the IDD to

protected by a table-mounted lower body radiation

the posterior aspect of their left shoulder, so that the

lead shield (skirt), with 1-mm lead-equivalent prop-

dosimeter faced the radiation source.

erties, and when standing on the patient’s right side,

The IDD is a direct ion storage dosimeter, the basic

a ceiling-mounted “drop down” lead acrylic shield

principles of which are well described in the pub-

with 0.5-mm lead-equivalent properties. The ANA

lished reports (8–10). The design of the dosimeter is

was positioned at the head of the patient and was

based upon the storage of charge in a nonvolatile

provided with a lead acrylic shield on wheels with

analogue (MOSFET) memory cell, surrounded by a

1-mm lead-equivalent properties. The TEEOP was

small volume of air, essentially acting as an ion

positioned at the head of the patient, toward the

chamber. When scattered radiation emanating from

patient’s left side and stood obliquely, predominantly

the patient is incident on the detector, ionization

with their back to the x-ray source. The TEEOP had

occurs within the ion chamber, altering the stored

access to use the acrylic shield on wheels but had no

charge. This change in charge provides a measure of

other specific additional protection. A plan view of

the air Kerma (mGy) incident on the detector. The

approximate staff and shielding positions is demon-

exposure can then be downloaded by connecting the

strated in Figure 1.

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Radiation Dose to TEE Operators

Procedural radiation measures collected were:  Procedure type.

F I G U R E 1 Graphical Representation of Approximate Positions of Key Staff Members

and Lead Protection Apparel

 Fluoroscopy time.  Total radiation dose (Kerma area product [KAP]).

ANA

 Patient body mass index (BMI).  Patient sex. projection

most

used

during

each

OP

procedure.

TEE machine

Lead shield On wheels

E TE

 C-arm

Additional Shield PROCEDURES. To

aid analysis, procedures were

grouped into the following categories:

Ceiling suspended lead shield

 Transfemoral TAVR or intervention.

OP

1

 TAVR or intervention using open surgical access, either transaortic or transapical (TAVIS).  Mitral valve intervention.

C-arm

Monitors

Table mounted lead shield OP

2

 Left atrial device implantation (LADI).  Ventricular or atrial septum intervention/implants. ADDITIONAL PROTECTION MEASURES FOR TEEOP.

After reviewing data from the initial procedures, steps were taken to reduce TEEOP dose, and an

This diagram shows the approximate location of the key personnel monitored during structural cardiac intervention procedures and their position relative to the C-arm (x-ray

additional ceiling-suspended lead acrylic shield with

source). It shows the position of lead shield on wheels that was available for the ANA and

0.5-mm lead-equivalent properties (Mavig, Munich,

TEEOP and the position of the table and ceiling suspended shielding for OP1 and OP2. In

Germany), identical to that available to OP1, was

addition, the position of the additional ceiling-suspended shielding is shown, which was

mounted to the ceiling of the hybrid theatre, such that the TEEOP could use it for additional protection (Figure 2). With this solution in place, dosimeters

implemented for a further 50 procedures (dotted line). ANA ¼ anesthetist; OP1 ¼ primary operator; OP2 ¼ secondary operator; TEE ¼ transesophageal echocardiography; TEEOP ¼ transesophageal echocardiography operator.

were worn for a further 50 procedures, and the results from the IDD, worn by the 4 key roles, were compared for procedures before and after the additional protection was installed. Facility human research ethics

F I G U R E 2 Image of the Angiography Suite With Additional

committee approval was granted for this study.

Ceiling-Suspended Lead Shield

ANALYSIS. In line with other studies investigating

radiation dose levels (13), and international guidelines (14), the KAP was used as the primary measure for overall radiation dose and patient dose. Effective doses were compared across procedure type and TEEOP individuals. The C-arm projection most used during each procedure were divided into 5 categories, and each key operator effective dose per unit of KAP (E/KAP) was analyzed across these categories. C-arm projection categories were defined as: steep right anterior oblique (RAO) (>20  ), RAO (6 to 20 RAO), posteroanterior (PA) (5  to þ5  ), left anterior oblique (LAO) (6  to 20 LAO), and steep LAO (>20 ). A Pearson correlation coefficient was used for correlation of TEEOP E against the different radiation

This image shows the position of the additional ceiling-

measures. Categorical data were compared across

suspended lead shield (arrow) used by the TEEOP for addi-

groups with a chi-square or Fisher exact test. Continuous variables were tested for normality,

tional protection in the final 50 procedures. It is of the same style as that used by OP1, which is also shown. The authors advocate this type of shielding to be used for procedures

and groups were compared using a Mann-Whitney

where TEEOP are required on a regular basis. Abbreviations as

U test or Student’s t-test as appropriate. Statistical

in Figure 1.

significance across multiple groups was performed

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Radiation Dose to TEE Operators

C E N T R A L IL L U ST R A T I O N Radiation Dose to TEEOP Compared With the Rest of the Team and the Impact of Additional Radiation Protection

A

*

Effective Dose E ( Sv)

10.0

*

8.0 6.0 4.0 2.0 0.0 TEEOP

OP1

OP2

ANA

B TEEOP Effective Dose E ( Sv)

1250

10.0 8.0 6.0 4.0 2.0 0.0 No Shield

Shield

Crowhurst, J.A. et al. J Am Coll Cardiol. 2018;71(11):1246–54.

Radiation dose to the TEEOP is relatively high per procedure when compared with the rest of the attending team (A) but can be reduced by 82% by installing additional ceiling-suspended lead protection (B). The circles indicate outliers and asterisks indicate extreme outliers. ANA ¼ anesthetist; OP1 ¼ primary operator; OP2 ¼ secondary operator; TEEOP ¼ transesophageal echocardiography operator.

using a Kruskal-Wallis or analysis of variance test

<0.05 remained in the final model. Regression

as appropriate. Multivariate linear regression was

coefficients were exponentiated to obtain the relative

performed to investigate independent predictors for

effects

TEEOP dose from the variables collected. A small

measured in the original units. SPSS version 22 (IBM,

constant was added to all TEEOP dose values, and

Armonk, New York) was used for analysis.

of

predictors

on

the

outcome

variable

natural logarithmic transformations were applied. Scatter plots of continuous predictors by the log-

RESULTS

transformed outcomes were examined, and KAP was also log-transformed for use in regression modeling.

There were 98 procedures performed before the

Variables with p values <0.20 in univariable linear

installation of the additional ceiling-mounted lead

regression models were entered into a multivariable

acrylic shield and a further 50 procedures after

linear regression model. Variables with p values

installation. Overall, patients were 54.7% male with a

Crowhurst et al.

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Radiation Dose to TEE Operators

T A B L E 1 Patient-, Procedural-, and Radiation Dose-Related Data for Each Procedural Group for Procedures Before the Additional Lead Protection

for the TEEOP Was Installed All (N ¼ 98)

Male BMI, kg/m2 FT, min KAP, Gy ∙ cm2 STRAO projection

TAVIS (n ¼ 19)

57 (58.2)

TAVITF (n ¼ 33)

11 (57.9)

29.73 (24.39–33.96) 15.6 (10.2–21.1)

27.89 (23.44–33.54) 9.1 (7.6–10.5)

88.26 (59.63–154.72) 21 (21.4)

LADI (n ¼ 14)

18 (54.5) 29.71 (24.44–35.49)

0 (0)

123.23 (74.51–154.72)

0 (0)

22.3 (17.6–35.45) 62.89 (38.79–103.99)

14 (100.0)

p Value

3 (37.5)

24.89 (21.87–29.19)

11.2 (9.4–14.8)

143.04 (73.46–200.85)

VASI (n ¼ 8)

15 (62.5)

33.55 (30.49–37.04)

17.4 (14.2–20.2)

69.66 (46.65–95.70)

MVI (n ¼ 24)

10 (71.4)

0.595

35.49 (32.90–43.16)

<0.001 <0.001

13.3 (9.3–15.2) 113.16 (53.77–172.43)

6 (25.0)

0.002 <0.001

1 (12.5)

Values are n (%) or median (interquartile range). BMI ¼ body mass index; FT ¼ fluoroscopy time; KAP ¼ Kerma area product; LADI ¼ left atrial device implantation; MVI ¼ mitral valve intervention; STRAO ¼ steep right anterior oblique; TAVIS ¼ transcatheter aortic valve implantation or intervention using open surgical access, either transaortic or transapical; TAVITF ¼ transfemoral transcatheter aortic valve implantation or intervention; TEEOP ¼ transesophageal echocardiography operator; VASI ¼ ventricular or atrial septum intervention/implantation.

median BMI of 28.70 kg/m2 (interquartile range [IQR]:

significantly

24.09 to 32.64 kg/m 2). There was no significant

OP2 (p ¼ 0.856), ANA (p ¼ 0.366) (Figure 3).

difference in sex for procedures before and after the additional lead protection was installed (58.2% male

across

C-arm

projection

categories:

There was a large difference in the number of procedures

that

individual

TEEOP

performed,

vs. 48.0% male; p ¼ 0.240), though there was a difference in patient BMI (29.73 kg/m 2 [IQR: 24.39 to 33.96 kg/m 2] before, 26.26 kg/m 2 [IQR: 23.66 to

F I G U R E 3 Operator E/KAP Composite Measure Grouped by C-arm Projection

30.84 kg/m2 ] after; p ¼ 0.012). PROCEDURES

WITHOUT

ADDITIONAL

TEEOP

140.0 *

PROTECTION. Before the additional protection was

present, a significant difference in radiation dose

120.0

Median TEEOP E was the highest of the key roles, though not statistically higher than OP1 E: 2.62 m Sv (IQR: 0.95 to 4.76 m Sv) versus 1.91 m Sv (IQR: 0.48 to 3.81 m Sv) (p ¼ 0.101), but was significantly higher than OP2 E: 0.48 m Sv (IQR: 0.00 to 1.91 mSv) (p < 0.001) and ANA E: 0.48 mSv (IQR: 0.00 to 1.43 mSv) (p < 0.001) (Central Illustration, panel A). Many of the patient and radiation measures were significantly different across the procedural cate-

E to KAP Ratio (µSv/Gym2)

across the key roles was demonstrated (p < 0.001).

100.0

80.0

*

*

60.0

*

* 40.0

gories. Median TEEOP E was significantly different across procedure groups, with LADI procedures demonstrating the highest E at 4.76 m Sv (IQR: 3.81

20.0

to 11.91 m Sv) and TAVIS the lowest E at 0.95 m Sv (IQR: 0.00 to 1.91 m Sv) (p < 0.001). A predominantly steep RAO projection was more likely in LADI procedures (100%) and not used in other procedures, including TAVIS (0%) and transfemoral TAVR or intervention (0%) (p < 0.001) (Table 1). TEEOP E

0.0 STRAO

RAO

PA

LAO

STLAO

C-arm Angle Category Role ANA

OP1

OP2

TEEOP

had the strongest correlation with KAP (r ¼ 0.547; p < 0.001). The TEEOP effective dose/KAP (E/KAP) composite value, when grouped by predominant C-arm angle demonstrated that doses were higher in procedures

This box plot maps the significant incremental increase in TEEOP radiation effective dose per unit of KAP (E/KAP) from the STLAO projection through to the STRAO projection (p ¼ 0.041), before the additional shielding was in place. OP1 also demonstrated a significant difference in effective dose (0.045). The other key personnel monitored did not demonstrate a significant difference across C-arm categories. It highlights the need for

where more RAO and steep RAO projections were

TEEOP to be vigilant with their position relative to the C-arm in procedures with pre-

used (p ¼ 0.041). OP1 E/KAP was also significantly

dominantly RAO projections. The circles indicate outliers and asterisks indicate extreme

different across C-arm projections, with the PA projection demonstrating the highest value (p ¼ 0.045). E/KAP for the other team members did not differ

outliers. KAP ¼ Kerma area product; LAO ¼ left anterior oblique; PA ¼ posteroanterior; RAO ¼ right anterior oblique; STLAO ¼ steep left anterior oblique; STRAO ¼ steep right anterior oblique; other abbreviations as in Figure 1.

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Radiation Dose to TEE Operators

procedures where the shield was in place, compared

T A B L E 2 Impact of the Implementation of Additional Lead Shielding

with those without the shield after correcting for

for the TEEOP No Shield (n ¼ 98)

Male

57 (58.2) 2

BMI, kg/m

p Value

24 (48.0)

29.73 (24.39–33.96)

FT, min

the other variables in the multivariate model. The

Shield (n ¼ 50)

15.6 (10.2–21.1)

KAP, Gy ∙ cm2

88.26 (59.63–154.72)

TEEOP E/KAP ratio, mSv/Gy ∙ m2

28.42 (13.47–52.64)

0.240

26.26 (23.66–30.84)

0.012

15.9 (10.3–20.8)

0.971

64.14 (42.68–123.20) 8.40 (0.00–18.53)

procedure type was also demonstrated as a significant predictor for TEEOP dose, with LADI procedures demonstrating an 8.7 times greater dose than

0.048 <0.001

the reference group: TAVIS (p < 0.001). KAP was also

demonstrated

as

a

significant

predictor

(p < 0.001).

STRAO projection

35 (21.4)

8 (16.0)

0.648

TEEOP E, mSv

2.62 (0.95–4.76)

0.48 (0.00–1.43)

<0.001

OP1 E, mSv

1.91 (0.48–3.81)

2.86 (0.95–4.76)

0.129

DISCUSSION. These results demonstrate that before

the additional ceiling-suspended protection was in

OP2 E, mSv

0.48 (0.00–1.91)

0.95 (0.00–2.86)

0.176

ANA E, mSv

0.48 (0.00–1.43)

0.00 (0.00–1.43)

0.559

place, there was a significant radiation dose to the

0.173

TEE operator for structural intervention procedures

Procedure type TAVIS

19 (19.4)

9 (18)

requiring TEE support (Central Illustration). The

TAVITF

33 (33.7)

25 (50)

dose is at least as high as the dose to the primary

LADI

14 (14.3)

2 (4)

operator, with the associated risks from radiation.

MVI

24 (24.5)

12 (24)

VASI

8 (8.2)

2 (4)

Radiation dose to primary operators performing percutaneous cardiac procedures has been associ-

Values are n (%) or median (interquartile range). This table compares the different patient and radiation measures before and after the installation of additional radiation shielding for the TEEOP. ANA ¼ anesthetist; LAO ¼ left anterior oblique; OP1 ¼ primary operator; OP2 ¼ secondary operator; other abbreviations as in Table 1.

ated with cataracts (4) and higher rates of orthopedic illness and cancer (6). Other studies have also found a higher incidence in left-sided brain tumors in physicians performing interventional procedures (5). The American Society of Echocardiography issued guidelines in 2014 in an effort to highlight the

ranging from 1 procedure for 1 operator to 39 pro-

radiation risks associated with percutaneous struc-

cedures for another. However, there was no statisti-

tural intervention procedures and ways to reduce

cally

patient-,

that risk, including additional shielding (7). It too

procedural-, or radiation-related variable across the

highlighted the paucity of data on this important

individual operators. There was no significant dif-

topic (7). There are good data for radiation dose

ference in radiation dose to the other key personnel

to

across TEEOP categories.

intervention

significant

difference

in

any

operators

during (15,16),

coronary and

angiography

additional

and

protection

measures have proved to be effective in reducing IMPACT OF ADDITIONAL TEEOP PROTECTION. After

radiation exposure (17). However, to date, there are

the additional protection was installed, median

no data with regard to radiation dose to TEE oper-

TEEOP E was reduced by 81.7%: 2.62 m Sv (IQR: 0.95

ators assisting with these procedures.

to 4.76 m Sv) versus 0.48 mSv (IQR: 0.00 to 1.43 m Sv)

Drews et al. (18) investigated radiation dose to

(p < 0.001) (Central Illustration, panel B). Radiation

key personnel during surgical TAVR procedures

dose to the other key personnel did not change

with a mean KAP of 86.61 Gy ∙ cm 2, similar to the

significantly with the installation of the additional

88.26 Gy ∙ cm 2 median overall KAP in this study.

protection. All other variables were not significantly

They reported a mean E of 17.5 mSv for the ANA/

different, other than patient BMI and KAP. The pro-

TEEOP, compared with a median E of 2.62 m Sv for the

cedure numbers across procedure categories were not

TEEOP in the present study. However, in that study,

significantly different after the installation of the

the ANA performed the echocardiography, which is a

additional shielding (p ¼ 0.173). The TEEOP E/KAP

different model to the dedicated TEEOP seen in the

value was significantly lower with the additional

present study. In addition, their methodology in

protection in place; 28.42 mSv (IQR: 13.47 to 52.64 m Sv)

calculating effective dose also differed (18).

versus 8.40 m Sv (IQR: 0.00 to 18.53 mSv) (p < 0.001)

The dose to the primary operator can also be compared. The median OP1 E of 1.9 mSv in the present

(Table 2). regression

study appears similar to the 2.3 m Sv and 1.2 m Sv of the

demonstrated that the use of the shield was signif-

radial and femoral access arms, respectively, of

icantly associated with TEEOP radiation dose. A 76%

another study investigating operator radiation dose

(95% confidence interval: 59% to 86%) (p < 0.001)

during acute myocardial infarction intervention (15).

reduction

Again, however, a slightly different method to

Univariate

in

and

multivariate

TEEOP

dose

is

linear

demonstrated

in

Crowhurst et al.

JACC VOL. 71, NO. 11, 2018 MARCH 20, 2018:1246–54

Radiation Dose to TEE Operators

calculate E was used, as E cannot be directly

additional protection and is possibly due to the lower

measured.

patient BMI in that group; however, E/KAP was

At this center, the TEEOP stand with their back to

demonstrated to be significantly lower after the

the radiation source, thereby potentially lowering the

installation of the additional protection, indicating

effectiveness of the lead garment. As such, TEE op-

that the lower KAP was not the reason for the lower

erators should take care to ensure that there is

TEEOP doses.

adequate lead-equivalent protection in the rear of the

STUDY LIMITATIONS. This is a single center obser-

lead apron, and “backless” style lead aprons should

vational study, with all the inherent weaknesses of

be avoided completely. TEEOP dose was not signifi-

such. It is possible that a different work flow and/or

cantly different between operators, indicating that

room layout would produce different results.

the high doses seen were not attributed to the working practices of 1 or 2 individuals but more likely related to the close proximity of the TEEOP to the

CONCLUSIONS

radiation source. Increasing their distance from the source would reduce the dose, but this is difficult

This study highlights a comparatively significant

to achieve while operating the TEE probe, and the

scattered radiation dose to TEE operators during

use of the lead shield on wheels is ergonomically

percutaneous structural intervention, with the asso-

challenging.

ciated risks involved. The radiation dose is at least as

Procedures with increasing steepness of RAO

high as that to OP1, and doses are higher for proced-

C-arm projections are shown in this study to deliver

ures with predominantly RAO C-arm projections.

higher doses to the TEEOP. In comparison, the

With the additional ceiling-mounted lead protection

lowest E/KAP to the OP1 is seen in procedures with

in place, radiation dose to TEEOP was reduced

steep RAO projections. This is in agreement with a

dramatically. On the basis of these results, the au-

previous study that demonstrated the lowest oper-

thors advocate that similar shielding devices should

ator dose with RAO projections and considerably

be implemented in cardiac catheterization theatres

higher doses from backscatter when LAO projections

and hybrid operating theatres where TEE operators

were used (19). In a similar manner, highest TEEOP

are used to facilitate these procedures on a regular

E/KAP is seen in the present study with increasing

basis.

steepness of RAO projections, because they stand

ACKNOWLEDGMENTS The authors thank Dr. Karen

on the left side of the patient and are more exposed

Hay for her assistance with statistical analysis and to

to the higher backscattered radiation. TEEOP should

the staff that assisted with the study by wearing

be mindful of this when performing left atrial and

the IDDs.

mitral valve procedures, where RAO projections are predominantly used. If it is possible to stand on the

ADDRESS

patient’s right side for these procedures, then this

Crowhurst, Cardiac Investigations Unit, The Prince

FOR

CORRESPONDENCE:

should be considered. Radiation doses to the TEEOP

Charles

were significantly lower after the implementation of

Queensland,

the ceiling-suspended shield; however, doses to OP1

hotmail.com OR [email protected].

Hospital,

Rode

Australia.

Road,

E-mail:

Mr.

James

Chermside,

Jimcrowhurst@

did not significantly decrease and were higher than the

TEEOP

when

both

had

ceiling-suspended

shields present. The higher dose to OP1 is likely due to the shorter distance between the patient and OP1 during procedures and the fact that the shield may have been difficult to use for certain procedures, such as TAVIS, where the PA projection is commonly used, and in this study, higher doses are demonstrated. Normalizing the operator’s dose to KAP is advantageous as it then accounts for confounding factors that have an impact on operator dose. KAP is the primary measure for the amount of radiation used for the procedure. It is a measure of the dose output from the x-ray system and the area exposed. KAP was lower for procedures after the installation of the

PERSPECTIVES COMPETENCY IN SYSTEMS-BASED PRACTICE: The exposure of operators performing transesophageal echocardiography to ionizing radiation during percutaneous interventions on patients with structural heart disease is higher than that of other staff. TRANSLATIONAL OUTLOOK: Further efforts are needed to develop optimum ceiling-mounted lead shielding and other safety measures in catheterization laboratories and hybrid operating facilities to reduce the exposure of team members providing imaging support.

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