Medical Fred

G. Rueter,

DSc

Average Diagnostic

#{149} Burton

J.

Conway,

Index terms: Diagnostic radiology, 60.11, 70.11 #{149} Quality assurance. exposure to patients and personnel, #{149} Radiations, measurement, 33.11,

I

From

1990;

the

Center

33.11, Radiations, 33.11, 70.11

70.11

177:341-345

for Devices

#{149} John

L McCrohan,

MS

#{149} Orhan

Radiation Exposure Values Radiographic Examinations’

National surveys of more than 600 facilities that performed chest, lumbosacral spine, and abdominal cxaminations were conducted as a part of the Nationwide Evaluation of XRay Trends program. Radiation cxposures were measured with use of a set of standard phantoms developed by the Center for Devices and Radiological Health of the Food and Drug Administration, U.S. Public Health Service. X-ray equipment parameters, film processing data, and data regarding techniques used were collected. There were no differences in overall posteroanterior chest exposures between hospitals and private practices. Seventy-six percent of hospitals used grids, compared with 33% of private practices. In general, hospitals favored a high tube voltage technique, and private facilities favored a low tube voltage technique. Forty-one percent of private practices and 17% of hospitals underprocessed their film. Underprocessing in hospitals increased from 17% in 1984 to 33% in 1987. Average exposure values for these examinations may be useful as guidelines in meeting some of the new requirements of the Joint Commission on Accreditation of Healthcare Organizations.

Radiology

MS

and

Radiological

T

Center for Devices and Radiological Health of the Food and Drug Administration, U.S. Public HE

cooperates

with

Conference of Radiation gram Directors (CRCPD)

Health

Service,

Control in the

duction

of a program

the

Procon-

to estimate

ra-

diation exposures associated with specific radiologic examinations. This program is known as the Nationwide Evaluation of X-Ray Trends (NEXT) program. The original goal of NEXT was to provide useful data for participaring local, state, and federal agencies to use in setting priorities and planning programs to improve specific areas of radiologic health practices. The data are also useful to mdividual facilities. From 1973 to 1983, the NEXT program surveyed exposures from 12 common medical and dental examinations. Participation in the program was voluntary; consequently, the samples from which exposure estimates were derived were not always representative of the national average. Compounding this problem was the fact that, in all cases, the technique selected for the surveyed cxamination was a manual technique provided by the resident operator. This technique was susceptible to error, since it often was difficult to provide a technique for the “standard” patient. In addition, there were often no established technique factors available for systems that employed automatic exposure control. In 1984, the NEXT program began employing clinically validated standard exposure equivalent phantoms

Health,

Food

and

Drug

Administration,

H. Suleiman,

for

Physics PhD

Three

for use with automatic exposure control systems. In addition to the assessment of the developed posteroanterior (PA) chest phantom (1), the NEXT protocol was evaluated in a pilot survey (2,3) prior to the actual national survey. The CRCPD also assumed a more active role and, to the extent possible, committed all of its member agencies to participate in this annual survey. Resource limitations restricted the survey to one examination per year. In addition to the chest phantom, an abdomen-lumbosacral spine phantom was also developed (4). This approach has been used for NEXT surveys since 1984 (5,6). Complete data from the 1984-1987 annual surveys have been published by the CRCPD (7). The results of these national surveys take on additional importance with the recent requirement of the Joint Commission on Accreditation of Healthcare Organizations that radiography facilities have a “quantitative value” for the dose and exposure given for each procedure. Many believe that such values, when compared

with

national

“averages”

or

“standards of care,” are necessary for the adequate evaluation of a facility. The data presented here provide statistically representative national averages for chest, abdomen, and lumbosacral spine projections with use of standard exposure equivalent phantoms. The NEXT protocol has also been used in Sweden (8), and the results provide an interesting comparison with data from the United States.

5600

Fishers Ln, HFZ-240, Rockville, MD 20857. From the 1989 RSNA scientific assembly. Received March 12, 1990; revision requested April 18; revision received June 12; accepted June 29. Address reprint requests to F.G.R. The mention of commercial products, their sources, or use in connection with material reported herein is not to be construed as either actual or implied endorsement of such products by the Department of Health and Human Services. ‘#{176} RSNA, 1990

Abbreviations: AHA American Hospital Association, CRCPD = Conference of Radiation Control Program Directors, ESE entrance skin exposure, NEXT Nationwide Evaluation of X-Ray Trends, PA posteroanterior, STEP sensitometric technique for the evaluation of processors.

341

Figures

1, 2.

(1) ESE for the PA chest

35

pro-

jection of a standard adult patient, that is, height of 172 cm (5 ft 8 inches), weight of 74.5 kg (164 lb), and a chest and abdomen thickness of 23 cm (9 inches). Checked bars = hospital data from 1984, and striped bars = private practice data from 1986. (2) Routine tube voltage values used with standard adult patient for the PA chest projection. Checked bars = hospital data from 1984, and striped bars = private practice data from 1986.

% 30 0

0

25

f

f

20

S

S

U

U

15

r

e

5

I

y S

MATERIALS

AND

A

129

sample

participating

physical

No Grid (n102)

2.5

Maximum (mR) Mean (mR)

beds) from medical,

surgical

to the

tabuin

100 beds,

was size

on-site

Minimum (mR) First quartile (mR) Median (mR) Third quartile (mR)

Private

1984

Grid

of

by

than

and

for the

110-129

Projections

(n317)

examina-

sample

(less

300 stay,

for PA Chest

Hospitals

base

1987. The presented

were

90-109

The

a sample data

PA chest

a stratified

and short

Table 1 ESE Values

abdomen-lumbosa-

examination the AHA

70-89

kVp

(AHA)

This

be selected

100-299 nonfederal,

29 24 29

1970

of in

(10).

tabulation of hospitals (11) easily defined and available

was

y

conducted

(9) demonstrated that the majority medical radiographs were obtained hospitals.

e

1.

Exposure

U.S.

V

(mR)

ESE Sample

r

LA

10

V

densitometer

Middleton,

by

PA

Chest

Although there are minor differences due to hospital bed size and between private practices and hospitals, the major observed differences in cxposure are due to technical factors normally associated with the examination, such as the speed of the screen-film combination, grid usage, density of the radiograph, and processing technique. Figure 1 shows the distribution of entrance skin cxposure (ESE) values, free-in-air, for the PA chest projection for hospitals (1984) and private practice facilities (1986). The numeric values are tabulated in Table 1. Table 2 compares PA chest exposures between hospitals (1984) and private practice facilities (1986). The exposures are further categorized on the basis of screen-film speed and November

1990

Table Effect

2 of Screen-Film

Speed

on ESE for PA Chest

Projections

in Hospitals

and Private

Facilities

Speed 100 Grids

200

400

Grids

No Grid

1

5.2 16.4 24.8 32.2 65.5 25.2 1.6 61

5.2 8.2 11.6 18.1 44.3 14.9 1.9 26

2.5 9.7 13.6 18.1 47.3 15.2 0.7 126

2.4 5.6 6.7 9.2 16.7 8.1 0.7 36

4.0 9.2 11.6 16.0 46.5 13.5 0.9 69

2.7 5.7 6.9 8.4 15.4 7.4 0.5 26

5.3 8.2 11.8 16.0 16.9 11.8 1.0 15

4.2 4.8 8.4 14.7 27.2 10.7 2.7 8

0.5 10.0 14.9 31.0 56.2 20.8 5.1 10

8.7 14.0 20.6 34.8 80.9 28.8 7.3 9

6.2 8.6 11.3 22.1 47.0 16.0 2.2 22

4.8 8.6 11.9 23.6 37.3 15.8 2.7 13

1.2 6.9 9.8 17.2 33.1 12.0 2.0 18

7.2 10.5 12.0 18.0 21.1 14.0 1.3 12

2.5 3.6 7.2 11.4 16.2 7.5 1.3 12

9.8 9.8 16.9 38.0 38.0 21.6 8.5 3

2.8 2.8 10.7 15.2 15.2 9.6 3.6 3

Grid

Grid

500

No Grid

No Grid

in hospitals (1984) Minimum (mR) 8.2 First quartile (mR) 18.5 Median (mR) 29.5 Third quartile (mR) 38.6 Maximum (mR) 71.4 Mean (mR) 31.4 Standard error of the mean 3.8 No.ofhospitals 19 PA chest in private facilities (1986) Minimum (mR) 17.0 First quartile (mR) 17.0 Median (mR) 52.8 Third quartile (mR) 54.5 Maximum (mR) 54.5 Mean (mR) 41.4 Standard error of the mean 12.2 No.ofprivatefacilities 3

300

No Grid

Grids

No Grid

PA chest

Note.-ESE * Includes

values air gap.

are in units

22.1 22.1 22.1 22.1 22.1 22.1

of 2.58 X lO

C/kg

(mR),

free-in-air

at 2.3 cm.

22.

affecting

0/

20.

0

is film

0

evaluated cessing

18. 0

f

16.

the

%

mal,

14. 12.

U

U

r

8.

V

6.

r

e y

4.

V

2.

e

S

1

99

ty on

the

normal ing sate

y

of radiograph

Under

Normal

Over

4.

Figures

3, 4. (3) Optical density of a radiograph of the LucAl phantom, which represents the chest of a standard adult patient. Checked bars hospital data from 1984, and striped bars private practice data from 1986. OD optical density. (4) Efficiency of the film processor for units servicing PA chest projections. Underprocessing is defined as less than 80% of the manufacturers’ recommendations, overprocessing is defined as greater than 120% of the recommendations. Checked bars hospital data from 1984, and striped bars private practice data from 1986.

usage.

lower

In general,

speed

creased

the

systems

and

use

grids

tals ties

of

in-

exposures.

Nearly

76%

grids

for

only

33%

them.

of

scatter of

This

the

hospitals

used

suppression,

the

private

pattern

whereas facilities

of grid

use

used

is asso-

ciated with more frequent use of higher tube voltage technique by hospitals. Figure 2 compares the fre-

quency

distributions

in hospitals

tice

(1984)

(1986).

of tube

voltage

private

prac-

and

A bimodal

distribution of tube voltage is evident for both hospitals and private practice; however, private practice had more facilities in the 70-89-kVp range, whereas hospi-

Volume

177

Number

#{149}

2

had a larger percentage of faciliin the 1 10-129-kVp range. The ranges of optical densities are

shown in Figure 3. There is a rather broad distribution for both hospitals and private facilities, with a “peak”

4. Slightly

radiograph

acceptance from

One

of radiographs

that

are

optimum.

of the

most

overlooked

factors

17% densiwith

an underprocess-

facility would by overexposing

have

also The

the

to compenpatient.

results large

in loss percentage

Un-

of

(41%) of private facilities that were underprocessing is of major concern to us. Ongoing publicand privatesector efforts to improve processor quality

may

control

correct

this

situa-

tion.

Swedish

Comparison

hospitals in Sweden (4.15 X 106 C/kg), the hospitals in the 17.7

mR

(4.57

used a high tered beam the United

use grids, projection

the for

(8) was 16.1 mR and the ESE for United States was

X 106

C/kg).

scatter and,

Hospitals

suppressors in general,

tube voltage, heavily filtechnique. Hospitals in States used a low tube

voltage

without

voltage hospitals

with a grid. The Swedish tended to use somewhat

slower screen-film (two thirds used far

are

over

as a facility

processing,

in Sweden used 100% of the time

in the range of 1.00-1.74. Optical density is measured in an area corresponding to the lung on the radiograph, and an “ideal” radiograph should have an optical density near 1 .4. Nearly half of the phantom radiographs had optical densities outside the 1.00-1.75 range, indicating

be

Pronor-

overprocessing

For hospitals that ESE for the PA chest grid

can

(12). with

were underprocessthe same optical

derprocessing image quality.

S

1.99

and

in Figure

of the hospitals ing. To obtain

S

of a radiograph Processing

by use of STEP values associated

under-,

plotted

S

quality

processing.

a grid

or a high

tube

combinations

a speed of 200). Hospitals in Sweden used a range of processing efficiencies but, in general, had less underprocessing and more

Radiology

343

#{149}

overprocessing United States.

than

hospitals

in the

% 0

Abdomen-Lumbosacral

Spine S

At the time of preparation of this article, the only results of the NEXT survey for the abdomen-lumbosacral spine projections that were available

were

for hospitals.

The

1970

x-ray

U

r V

ex-

posure study report (9) and National Council on Radiation Protection and Measurements report no. 100 (10) suggest that the majority of these procedures are performed in hospitals. We believe that the hospital data

are

generally

representative

of this

examination nationally. Analysis of 1989 data is currently under way to assess abdomen-lumbosacral spine projections in private facilities. Figure 5 is a histogram of the ESE for the abdomen-lumbosacral spine. There is, as expected, a slightly higher ESE for the lumbosacral spine than for the abdomen projection. Table 3 lists the numerical values for the respective projections. Table 4 shows the results from NEXT 1987 on the effect of screenfilm “speed” on ESE. There were only four facilities in the project that did not use a grid; hence, data for such facilities were essentially nonexistent. Figure 6 shows the distribution of tube voltage for the abdomen-lumbosacral spine. As expected, because of the different imaging task (bone vs

soft

age

tissue),

tube

a slightly

voltage

higher

was

observed

using the same technique factors for abdomen and lumbosacral spine procedures. Abdomen optical density values were measured behind the soft-tissue portion of the radiograph, whereas the lumbosacral spine optical densities were measured behind the spinal column. Therefore, the optical density values reported for the lumbosacral spine projections were lower. The lumbosacral spine optical distribution

between

(Fig

1.00 and

1.24,

7)

peaked

whereas

the

majority of the abdominal values were 1.50 and above. The quality of film processing in hospitals seems to have declined from 1984 to 1987. Seventeen percent of hospitals were underprocessing in 1984 and 33% were underprocessing in

344

1987

(Fig

Radiology

#{149}

8).

Was

this

difference

S

an

uu

i -

199

..uu

-

299

ju

399

>

3i.iU

499

89

80-89

kVp

(mA)

ESE

6.

5.

Figures

5, 6. Data

(5) ESE for the abdomen from hospitals for 1987.

patient. spine. (6) Tube standard adult = lumbosacral

Table 3 ESE Values

voltage

values

patient. spine.

Data

used from

for Abdomen

and lumbosacral Checked bars

spine abdomen,

for the abdomen hospitals

for

and

1987.

and Lumbosacral

projection striped

Minimum (mR) First quartile (mR) Median (mR) Third quartile (mR) Maximum (mR) Mean (mR) Standard error of the mean

CONCLUSION There

were

average

no PA

tween hospitals The ESE value

mR (4.08 for

x

X

private

106

C/kg)

practice

C/kg).

106

differences exposures and private for hospitals

in overbepractice. was 15.8

chest

and

was

Seventy-six

the

15.7

Average C/kg)

and

424

mR

(10.9

X l0

(ti

spine survey

surveys did of hospitals.

(PA

ESE

(4.05

is not

percent

of

tween

C/kg)

for

bars

Spine 248)

=

not utilize ESE values

a grid. They are in units

were not of 2.58 X

lumbosacral spine projections. This is consistent with differences in imaging tasks between the abdomen and lumbosacral spine projections. It was encouraging to note that the average screen-film “speed” values were in the 300-400 range, which can primanly be attributed to the increasing use of rare-earth screen phosphors. Thirty-three percent of the hospi-

mR

ESEs were 369 mR (9.52 for abdomen projections

for a

striped

tals in the 1987 NEXT survey (abdomen and lumbosacral spine) were underprocessing, whereas 17% of hospitals in the 1984 NEXT survey

hospitals used grids compared with 33% of private practices. In general, hospitals used a high tube voltage technique (110-130 kVp), and private practice facilities favored a low tube voltage technique (70-90 kVp). Forty-one percent of private practices and 17% of hospitals underprocessed film.

iO

Lumbosacral

17.9

change

projections

Spine

13.9

a function

a standard adult = lumbosacral

abdomen,

62.3 259.3 347.4 514.8 2154.0 422.2

in processing practice of time, or were the processors normally used for PA chest radiographs better controlled (subject to a better quality-assurance program) than those used to process abdomen and lumbosacral spine films?

all

spine

bars

65.8 230.1 318.7 452.2 1607.4 368.4

Note-Only three abdomen and two lumbosacral included in this data. Data are from the 1987 NEXT iO- C/kg (mR), free-in-air at 23 cm.

as

for bars

lumbosacral

Checked

Abdomen (n 245)

actual

aver-

for the How-

lumbosacral spine projection . ever, a large majority of the surveys for both procedures (88% for the abdomen and 92% for the lumbosacral spine) were between 70 and 89 kVp. There was a common practice of

density

e y

chest) known

1984

were

underprocessing. if this

and

1987

It

beor if processors

was

a trend

used for chest radiography differ from processors used for abdominal radiography. This is contrary to our observations in mammography, where the trend in processing for mammography facilities (13) mdicates an improvement between 1985 and 1988. U

X

References 1.

Conway BJ. Butler PF, Duff JE, et al. Beam quality independent attenuation

November

1990

Table Effect

4 of Screen-Film

Speed

on ESE for Abdomen

and Lumbosacral

Spine Speed

100 Grid Abdomen Minimum(mR) Firstquartile(mR) Median(mR) Thirdquartile(mR) Maximum(mR) Mean(mR) Standard error ofthemean No.ofhospitals Lumbosacral spine Minimum(mR) Firstquartile(mR) Median(mR) Thirdquartile(mR) Maximum(mR) Mean(mR) Standard error ofthemean No.ofhospitals Note-Data

are from

200 No Grid

376 376 553 731 731 553

718 718 718 718 718 718

178 2

944

532 207

1987 NEXT

243 322 475 691 1607 580 84 20

819 819 819 819 819 819

154 318 671 1172 2154 813

.

. .

3

142 17

.

1 survey

of hospitals.

35

%

%

No Grid

1

. .

290 290 361 944

the

Grid

300

ESE values

.

.

.

. .

.

. .

.

. .

.

.

.

.

. .

.

.

.

.

Grid

. .

.

.

.

.

.

.

. .

.

.

.

.

.

.

.

.

.

.

No Grid

93 227 315 440 1078 351

of 2.58

.

. .

.

.

. .

.

. .

.

. .

.

. .

.

. .

. .

.

20 114

. . .

0 X iO

C/kg

(mR),

7.

80

30

0

0

f

25

f

20

S U

8.

S

15

U

r 10

V

e

5

y S

0

ii

r

9.

V

e -

199 149 1

74

1

99

of radiograph

7.

y S Under

Normal

10. Over

8.

Figures

7, 8. (7) Optical density of a radiograph of the abdominal phantom which represents a standard adult patient. The abdomen densities were obtained in the soft-tissue portion of the image. The lumbosacral spine densities were obtained in the image of the spine. Data from hospitals for 1987. Checked bars = abdomen, striped bars = lumbosacral spine, OD = optical density. (8) Efficiency of the film processors in hospitals for units servicing the PA chest and abdomen projections. Underprocessing is defined as less than 80% of the manufacturers’ recommendations, overprocessing is defined as greater than 120% of the recommendations. Checked bars PA chest data from hospitals in 1984, and striped bars = abdomen data from hospitals in 1987.

2.

:

phantom for estimating patient exposure from x-ray automatic exposure controlled chest examinations. Med Phys 1984; 11:827-832. Butler PF, Conway BJ, Suleiman OH, Koustenis GH, Showalter CK. Chest radiography: a survey of techniques and exposure levels currently used. Radiology 1985; 156:533-536. Butler PF, Conway BJ, Suleiman OH, Koustenis GH, Showalter CK. Results of a six-state study to collect exposure, technique and processing data in chest radiography. Medical Imaging and Instrumentation ‘84. SPIE 1984; 486:21-28.

Volume

177

Number

#{149}

2

4.

5.

6.

Conway BJ, Duff JE, Fewell TR, Jennings RJ. A patient-equivalent attenuation phantom for estimating patient exposures from automatic exposure controlled x-ray examinations of the abdomen and lumbosacral spine. Med Phys (in press). Rueter FG. Preliminary report-NEXT 1984. 17th Annual National Conference on Radiation Control. Frankfort, Ky: Conference of Radiation Control Program Directors, Inc., 1985; 95-105. Rueter FG. NEXT87 Project preliminary report. 20th Annual National Conference on Radiation Control. Frankfort, Ky: Conference of Radiation Control Program Directors, Inc., 1988; 238-246.

11.

12.

13.

136 144 246 335 405 250 37 15

459 459 459 459 459 459

87 136 308 385 428 273

.

. .

. .

1

free-in-air

Grid

1

.

93 252 333 487 1360 383

. . .

.

346 346 346 346 346 346

18 113

.

500 No Grid

66 220 301 433 1372 350

0

26 85

are in units

. . .

. . .

62 267 366 517 1851 420

0

.. .

Grid

. . .

19 86

0

.

400

48 7

No Grid

... ... ... ... ... ...

...

0 ... ... ... ... ... ...

...

0

at 23 cm.

Conway BJ. Nationwide evaluation of xray trends (NEXT): tabulation and graphical summary ofsurveys. 1984 through 1987. Frankfort, Ky: Conference of Radiation Control Program Directors, Inc., 1987. Leitz WK, Hedberg-Vikstr#{246}m BRK, Conway BJ, Showalter CK, Rueter FG. Assessment and comparison of chest radiography techniques in the United States and Sweden. Br J Radiol 1990; 63:33-40. Population exposure to x-rays, U.S. 1970. Bureau of Radiological Health, FDA, Department of Health, Education, and Welfare publication no. 73-8047. Washington, DC: Government Printing Office, 1973. Exposure of the U.S. population from diagnostic medical radiation. NCRP report no. 100. Bethesda, Md: National Council on Radiation Protection and Measurements, 1989. American Hospital Association. Amencan hospital association guide to the health care field. American Hospital Association, Chicago: 1986. Suleiman OH, Showalter CK, Koustenis GH, Hotte E. A sensitometnic evaluaton of film chemistry processor systems in the state of New Jersey. Department of Health and Human Services, Food and Drug Administration, publication 82-8189. Rockville, Md: Bureau of Radiological Health, 1982. Conway BJ, McCrohan JL, Rueter FG, Suleiman OH. Mammography in the eighties. Radiology 1990; 177:335-339.

Radiology

345

#{149}