PEDIATRIC EFFECTIVE DOSES IN DIAGNOSTIC RADIOLOGY
ABSTRACT Pediatric effective doses can be obtained for any radiologic examination using the selected radiographic technique factors (kV/mAs), the exposure geometry and the patient mass. The energy imparted ε to the patient may be computed from the exposure area product, x-ray tube voltage, half-value layer and patient thickness. Values of energy imparted may be subsequently converted to an effective dose E using published radiographic projection specific E/ε ratios determined using Monte Carlo techniques applied to anthropomorphic phantoms, with a correction applied for the patient mass. Pediatric effective doses (head, chest, abdomen and extremity) were computed for representative adult patients, as well as for pediatric patients ranging from new born to 15 year old youths. Values of patient effective dose were dependent on body size, selected technique factors as well as the type of radiographic imaging equipment used, with no clear trends for effective dose with patient age.
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ABSTRACT: The patient effective dose, E, is an indicator of the stochastic radiation risk associated with radiographic or fluoroscopic x-ray examinations. Determining effective doses for radiologic examinations by measurement or calculation is generally very difficult. By contrast, the energy imparted, epsilon, to the patient may be obtained from the x-ray exposure-area product incident on the patient. As energy imparted is approximately proportional to the effective dose for any given x-ray radiographic view, the availability of E/epsilon ratios for common radiographic projections provides a convenient way for estimating effective doses. Ratios of E/epsilon were obtained for 68 projections using E and epsilon values obtained from published dosimetry data computed using Monte Carlo techniques on an adult anthropomorphic phantom. The average E/epsilon ratio for the 68 projections in adults was 17.8+/-1.4 mSv/J, whereas uniform whole body irradiation corresponds to 14.1 mSv/J. The major determinant of E/epsilon ratios was the projection employed (the body region irradiated and x-ray beam orientation), whereas the tube potential and beam filtration were of secondary importance. Adult E/epsilon ratios may also be used to obtain effective doses to pediatric patients undergoing x-ray examinations by application of a correction factor based on the patient mass.Medical Physics 09/1997; 24(8):1311-6. · 2.91 Impact Factor
- British Journal of Radiology 10/1998; 71(849):994-5. · 1.22 Impact Factor
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ABSTRACT: Energy imparted is a measure of the total ionizing energy deposited in the patient during a radiologic examination and may be used to quantify the patient dose in diagnostic radiology. Values of the energy imparted per unit exposure-area product, omega (z), absorbed by a semi-infinite water phantom with a thickness z, were computed for x-ray spectra with peak x-ray tube voltages ranging from 50-140 kV and with added filtration, ranging from 1-6 mm aluminum. For a given phantom thickness and peak x-ray tube voltage, the energy imparted was found to be directly proportional to the x-ray beam half-value layer (HVL) expressed in millimeters of aluminum. Values of omega (z) were generated for constant waveform x-ray tube voltages and an anode angle of 12 degrees, and were fitted to the expression omega (z) = alpha x HVL + beta. Fitted alpha and beta parameters are provided that permit the energy imparted to be determined for any combination of tube voltage, half-value layer, and phantom thickness from the product of the entrance skin exposure (free-in-air) and the corresponding x-ray beam area. The results obtained using our method for calculating energy imparted were compared with values of energy imparted determined using Monte Carlo techniques and anthropomorphic phantoms for a range of diagnostic examinations. At 60, 80, and 120 kV, absolute values of energy imparted obtained using our method differed by 8%, 10%, and 12%, respectively, from the corresponding results of Monte Carlo computations obtained for an anthropomorphic phantom. The method described in this paper permits a simple determination of energy imparted for any type of diagnostic x-ray examination which may be used to compare the radiologic risks from differing types of x-ray examinations, optimize imaging techniques with respect to the patient dose, or estimate the patient effective dose equivalent.Medical Physics 05/1997; 24(4):571-9. · 2.91 Impact Factor
PEDIATRIC EFFECTIVE DOSES IN DIAGNOSTIC RADIOLOGY
Walter Huda1, Nikolaos A Gkanatsios2, Robert J Botash1 and Ann S Botash3
1Department of Radiology, SUNY Health Science Center at Syracuse, NY, USA
2Department of Radiology, University of Florida, Gainesville, FL, USA
3Department of Pediatrics, SUNY Health Science Center at Syracuse, NY, USA
Pediatric effective doses can be obtained for any radiologic examination using the selected radiographic technique factors
(kV/mAs), the exposure geometry and the patient mass. The energy imparted e to the patient may be computed from the
exposure area product, x-ray tube voltage, half-value layer and patient thickness. Values of energy imparted may be
subsequently converted to an effective dose E using published radiographic projection specific E/e ratios determined using
Monte Carlo techniques applied to anthropomorphic phantoms, with a correction applied for the patient mass. Pediatric
effective doses (head, chest, abdomen and extremity) were computed for representative adult patients, as well as for pediatric
patients ranging from new born to 15 year old youths. Values of patient effective dose were dependent on body size, selected
technique factors as well as the type of radiographic imaging equipment used, with no clear trends for effective dose with
The effective dose quantifies the radiation risk to a patient undergoing any diagnostic x-ray examination.1,2 Benefits of the
effective dose include the ease of comparing doses associated with diverse types of radiographic examination, as well as the
ability to compare patient doses with natural background and regulatory dose limits.3,4 In this study, effective doses to
patients ranging from newborns to adults were determined for representative x-ray examinations of major body regions (i.e.,
head, chest, abdomen and extremities).
Technique factors. For examinations of the head, chest and abdomen, radiographic techniques (i.e., kVp/mAs) were
obtained from technique charts for dedicated pediatric room which uses a 600 speed screen-film combination. Pediatric
radiographs, ranging from newborns to 15 year olds, are all performed without the use of a scatter removal grid.
Corresponding adult technique factors were obtained for conventional radiographic rooms which all use scatter removal
grids. Radiographic techniques for the extremity examinations were taken from charts for (non-grid) fine screen and single
emulsion film combination, with a nominal speed value of 80. Representative x-ray field sizes for each age and examination
were taken from the published literature,5 with an estimate was made of the (water equivalent) patient thickness based on
the body part and typical patient thickness.
Dosimetry. The entrance skin exposure, and x-ray beam half-value layer (HVL), were theoretically calculated using
computed x-ray spectra at each kVp. The predictions of the theoretical model were compared to measurements made on a
Philips Classic C-850 three-phase generator with a Eureka ROT-350 x-ray tube, and the total x-ray beam filtration adjusted
to ensure a good fit between theory and measurement. Relative and absolute values of x-ray tube output and HVL were
generally found to agree within about 5%.
Energy imparted, e, was computed from the exposure-area product, EAP, at the entrance plane of the patient and a
conversion factor w(z) using the expression
e =w(z)×EAPJ (1)
where z is the patient thickness.6 For a given x-ray tube voltage, the conversion factor w(z) is given by
were a and b are constants.7 Values of energy imparted were converted to the corresponding patient effective dose E using
where (E/e)i is the body/projection specific ratios of effective dose per unit energy imparted for examination i, and M is the
Technique factors. Table 1 lists the technique factors used for performing radiographic examinations of the head (AP),
chest (PA), abdomen (AP) and extremity (AP view of forearm). As the patient size increases, the kVp generally increases.
Also depicted in Table 1 are the corresponding values of x-ray beam cross-sectional area and the estimated patient thickness
in terms of water equivalence. As expected, both the x-ray beam cross-section and patient thickness monotonically increase
with increasing patient age.
Table 1: X-ray technique factors, exposure area and patient thickness for head, chest, abdomen and extremity examinations.
67 kVp/2.0 mAs
(110 cm2/9.0 cm)
72 kVp/2.0 mAs
(160 cm2/12 cm)
75 kVp/2.0 mAs
(210 cm2/14 cm)
77 kVp/2.0 mAs
(240 cm2/15 cm)
79 kVp/2.0 mAs
(270 cm2/16 cm)
75 kVp/15 mAs
(320 cm2/20 cm)
60 kVp/2.0 mAs
(140 cm2/8.0 cm)
66 kVp/2.0 mAs
(250 cm2/9.0 cm)
70 kVp/2.0 mAs
(430 cm2/10 cm)
74 kVp/3.0 mAs
(670 cm2/13 cm)
78 kVp/4.0 mAs
(780 cm2/14 cm)
120 kVp/2.0 mAs
(1300 cm2/15 cm)
66 kVp/2.0 mAs
(200 cm2/10 cm)
70 kVp/4.0 mAs
(300 cm2/13 cm)
72 kVp/5.0 mAs
(540 cm2/15 cm)
75 kVp/6.0 mAs
(820 cm2/17 cm)
78 kVp/7.0 mAs
(900 cm2/20 cm)
75 kVp/15 mAs
(1200 cm2/22 cm)
56 kVp/5.0 mAs
(35 cm2/1.8 cm)
60 kVp/5.0 mAs
(84 cm2/3.3 cm)
62 kVp/6 mAs
(140 cm2/5.0 cm)
65 kVp/6.0 mAs
(200 cm2/6.2 cm)
65 kVp/8.0 mAs
(200 cm2/7.9 cm)
Dosimetry. Table 2 summarizes the key dosimetry parameters for the four types of radiographic examination for patients
ranging from newborn to the adult. In each cell, the first value is the entrance skin air kerma (free-in-air) in µGy. The second
term gives the energy imparted to the patient, expressed in µJ. In parentheses on the second line are the corresponding values
of patient effective dose in µSv.
As expected, values of the entrance skin exposure and energy imparted for the pediatric examinations all monotonically
increase with increasing patient age. Comparison of adult examinations with 15 year old patients is complicated by the
differences in radiographic technique, with 15 year old chests are performed at 78 kVp whereas adult chests are performed
at 120 kVp. An additional difficulty is the use of grids for the adult head/chest/abdomen examinations, which is expected
to have a large impact on the resultant values of entrance skin air kerma and energy imparted.
For pediatric head examinations, the effective dose increased as the patient age (size) was reduced, whereas for chest,
abdomens and extremity exams, the converse was generally true. Adult head and abdomen examinations have effective doses
much greater than pediatric effective doses. Effective doses for adult chest and extremity examinations were comparable to
those for 15 year old youths. Overall, there was no clear trend of patient effective doses with patient age; effective doses are
a (complex) function of body size, selected technique factors as well as the type of radiographic imaging equipment which
is used to perform these studies.
Table 2: Values of entrance skin air kerma ( µGy), energy imparted ( µJ) and the corresponding patient effective
doses( m Sv) for the specified patient ages and type of radiographic examination.
100 µGy/78.2 µJ
(10 m Sv)
120 µGy/165 µJ
(7.3 m Sv)
140 µGy/260 µJ
(5.9 m Sv)
150 µGy/320 µJ
(4.3 m Sv)
150 µGy/400 µJ
(3.1 m Sv)
1100 m Gy/3200 m J
(19 m Sv)
77 µGy/66 µJ
(19 m Sv)
96 µGy/160 µJ
(16 m Sv)
110 µGy/340 µJ
(18 m Sv)
190 µGy/1100 µJ
(33 m Sv)
280 µGy/2100 µJ
(36 m Sv)
150 m Gy/2500 m J
(34 m Sv)
100 µGy/140 µJ
(62 m Sv)
230 µGy/580 µJ
(90 m Sv)
320 µGy/1500 µJ
(120 m Sv)
420 µGy/3300 µJ
(160 m Sv)
550 µGy/5100 µJ
(140 m Sv)
1100 m Gy/13000 m J
(290 m Sv)
130 µGy/9.5 µJ
(0.21 m Sv)
160 µGy/44 µJ
(0.50 m Sv)
200 µGy/130 µJ
(0.87 m Sv)
220 µGy/240 µJ
(0.92 m Sv)
300 m Gy/360 m J
(1.1 m Sv)
1. Values of entrance skin exposure and energy imparted to patients generally increased with increasing patient age.
2. Values of patient effective dose were dependent on body size, selected technique factors as well as the type of radiographic
imaging equipment used.
3. There was no simple trend when comparing adult effective doses with those of infants and children.
4. There was no simple trend for the variation of pediatric patient effective dose with age.
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Commission on Radiological Protection, Annals of the ICRP Vol 21 Nos 1-3. Pergamon Press, Oxford (1991).
2United Nations Scientific Committee on the Effects of Atomic Radiation. 1993 Report to the General Assembly: Medical
Radiation Exposures. United Nations, New York, NY (1993).
3National Council on Radiation Protection and Measurements. Report No. 100: Exposure of the U.S. Population from
Diagnostic Medical Radiation. NCRP, Bethesda, MD (1989).
4Nuclear Regulatory Commission. 10CFR19: Notices, Instructions, and Reports to Workers: Inspection and Investigations.
Nuclear Regulatory Commission, Washington, DC (1995).
5Hart, D; Jones, D.G.; Wall, B.F. NRPB Report R262: Estimation of Effective Dose in Diagnostic Radiology from Entrance
Surface Dose and Dose-Area Product Measurements. National Radiological Protection Board, Didcot, Oxon (1994).
6Gkanatsios, N.A. Master Thesis: Computation of Energy Imparted in Diagnostic Radiology. University of Florida,
Gainesville, FL (1995).
7Gkanatsios, N. A.; Huda, W. "Energy imparted in diagnostic radiology." Medical Physics 24:571-579 (1997).
8Huda, W.; Gkanatsios, N. A. "Effective doses and energy imparted in diagnostic radiology." Medical Physics 24:1311-