DOI:10.2214/AJR.07.3057
AJR 2008; 190:467-473
© American Roentgen Ray Society
Prospective Evaluation of Image Quality with Use of a Patient Image Gallery for Dose Reduction in Pediatric 16-MDCT
Dagmar Honnef1,
Joachim E. Wildberger1,
Gabriel Haras2,
Christian Hohl1,
Gundula Staatz3,
Rolf W. Günther1 and
Andreas H. Mahnken1
1 Department of Diagnostic Radiology, University Hospital RWTH Aachen,
Pauwelsstrasse 30, D-52074 Aachen, Germany.
2 Siemens Medical Solutions, Forchheim, Germany.
3 Division of Pediatric Radiology, Department of Radiology,
Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen,
Germany.
Received October 10, 2006;
accepted after revision September 11, 2007.
Address correspondence to D. Honnef
(honnef{at}rad.rwth-aachen.de).
Abstract
OBJECTIVE. The purposes of this study were to evaluate prospective
adjustment of dose settings in pediatric 16-MDCT by use of computer-simulated
images in a patient image gallery and to compare the dose reduction achieved
with that of standard pediatric protocols.
SUBJECTS AND METHODS. The image gallery consisted of images from
weight-dependent sample examinations performed with varied simulated tube
current–exposure time settings. The scanning parameters prospectively
chosen on the basis of the image quality of the image gallery were used for 30
16-MDCT examinations (chest, n = 15; abdomen, n = 8; pelvis,
n = 7) of 22 children (14 boys, eight girls; mean age, 6.8 ±
5.8 years; mean body weight, 26.7 ± 19.6 kg). Three blinded
radiologists used a 4-point grading scale to rate the overall image quality of
the image gallery and the 16-MDCT scans. Objective and subjective image
quality was assessed for the simulated and actual CT scans. The concordance
correlation coefficient (K) was determined.
RESULTS. There was mainly moderate concordance with regard to
objective (chest, K = 0.69; abdomen, K = 0.33; pelvis, K = 0.55) and
subjective (chest soft-tissue window, kappa coefficient [
] = 0.00;
chest lung window, = 0.53; abdomen, = 1.00; pelvis, =
0.48) analysis of image gallery compared with actual 16-MDCT examinations.
Compared with use of previous weight-adapted pediatric standard protocols, use
of an image gallery resulted in further dose reduction for abdominal and
pelvic CT but not for thoracic CT.
CONCLUSION. A patient image gallery can be used as a basis for
pediatric 16-MDCT examinations. The gallery provides a preexamination overview
of expected image quality. Radiation exposure can be optimized with regard to
patient weight and the image quality needed to answer the clinical
question.
Keywords: dose • image quality • MDCT • pediatric
Introduction
Radiation exposure is the crucial point in use of CT. Children are up to 10
times more sensitive to radiation exposure than adults
[1], so it is essential to
optimize scanning parameters in pediatric 16-MDCT. However, because pediatric
examinations are performed relatively infrequently in most hospitals, CT
techniques used in examinations of children are often not adjusted to the size
or body region scanned [2].
Selecting appropriate technique factors that produce an optimal balance
between radiation dose and image noise and yield images that help answer the
clinical question can be difficult. A patient image gallery therefore was
developed that displays computer-simulated images with various reduced tube
current–exposure time settings
[3]. The aims of our
prospective study were to assess whether a patient image gallery can be used
for prospective adjustment of dose settings in pediatric thoracic, abdominal,
and pelvic MDCT and to evaluate image noise and overall image quality of
actual scans in comparison with simulated images.
Subjects and Methods
Patient Image Gallery
A patient image gallery is produced with computer-simulated dose-reduction
software. The algorithms used for dose simulation are part of the commercial
software Syngo Explorer (VAMP). The low-dose simulation technique is used to
increase the amount of random noise in the raw scan data. The simulation
considers quantum noise of the X-rays due to finite radiation dose, which
represents the main source of image noise. Because the physical principles are
well known, this effect can be modeled precisely by addition of
Poisson-distributed noise to the CT projection data (intensity values). The
variance is proportional to the difference of the inverse intensities
simulated minus the original intensities. For large patients and very low tube
currents, deficits in detector electronics also contribute to total noise.
This effect, however, can be neglected in the patient population under study
and for tube current range. The method was validated with water phantoms and
body part phantoms of varying sizes scanned at various tube
current–exposure time and kilovoltage values. Images at lower tube
current–time settings were generated by synthetic addition of noise and
compared with images actually acquired with lower tube current–time
settings.
We considered a total of 160 raw scan data (chest, n = 64;
abdomen, n = 59; pelvis, n = 37). The modified raw scan data
files were calculated with the same reconstruction parameters as for the
original CT scans. Raw scan data of existing high-dose reference pediatric
MDCT scans from six large hospitals in Europe were used.
With the data generated, we produced a patient image gallery consisting of
weight-dependent reference examinations with different simulated effective
tube current–time settings, convolution kernels (B30f, B60f), and slice
thicknesses (2 and 5 mm). The CT examinations displayed were used to obtain an
impression of the effects of varying examination parameters on image quality.
Data were presented in the following weight groups: less than 7.5 kg,
7.5–12.4 kg, 12.5–17.4 kg, 17.5–24.9 kg, 25.0–34.9 kg,
35.0–44.9 kg, 45.0–54.9 kg, and 55.0–64.9 kg. Figure
1A,
1B,
1C,
1D shows an example for 20-kg
body weight with the original MDCT scan and the corresponding
computer-simulated images at the same level with serial dose reductions. The
connection between decrease in tube current and increase in image noise and
reduction in image quality in the same patient is evident.
View larger version (124K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A —6-year-old girl with suspected intraabdominal abscess.
Example of image gallery images for 20-kg body weight with tube voltage of 100
kVp, B30f kernel, and 5-mm slice thickness. Original MDCT scan with effective
tube current–time product of 60 mAs.
|
|
View larger version (124K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1B —6-year-old girl with suspected intraabdominal abscess.
Example of image gallery images for 20-kg body weight with tube voltage of 100
kVp, B30f kernel, and 5-mm slice thickness. Computer-simulated images
corresponding to A at same level with serial dose reductions to
effective tube current–time products of 43 mAs (B), 30 mAs
(C), and 21 mAs (D). Increased noise and reduced image quality
with decreasing tube current in same patient are evident.
|
|
View larger version (128K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C —6-year-old girl with suspected intraabdominal abscess.
Example of image gallery images for 20-kg body weight with tube voltage of 100
kVp, B30f kernel, and 5-mm slice thickness. Computer-simulated images
corresponding to A at same level with serial dose reductions to
effective tube current–time products of 43 mAs (B), 30 mAs
(C), and 21 mAs (D). Increased noise and reduced image quality
with decreasing tube current in same patient are evident.
|
|
View larger version (131K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1D —6-year-old girl with suspected intraabdominal abscess.
Example of image gallery images for 20-kg body weight with tube voltage of 100
kVp, B30f kernel, and 5-mm slice thickness. Computer-simulated images
corresponding to A at same level with serial dose reductions to
effective tube current–time products of 43 mAs (B), 30 mAs
(C), and 21 mAs (D). Increased noise and reduced image quality
with decreasing tube current in same patient are evident.
|
|
Patients
Twenty-two patients (14 boys, eight girls) undergoing routine MDCT of the
chest, abdomen, pelvis, or a combination of these areas were examined
according to the patient image gallery. The age range was 13 days–19
years (mean age, 6.8 ± 5.8 years; median, 6.6 years). Parental consent
in accordance with the requirements of our local ethics committee was obtained
for each patient. The lowest body weight was 1.2 kg, the highest 64 kg (mean
body weight, 26.7 ± 19.6 kg; median, 23.5 kg). Nonionic IV contrast
material (iopromide, Ultravist 370, Bayer HealthCare) was administered to all
patients in conformity with body weight (1.5–2 mL/kg body weight) by
manual or power injection. The clinical indications for MDCT included cancer
(n = 17), inflammation (n = 4), trauma (n = 3), and
other (n = 6). A total of 30 examinations were performed. A gonad
shield was used for all boys
[4].
Application of the Patient Image Gallery
Before contrast-enhanced 16-MDCT, thoracic (n = 15), abdominal
(n = 8), and pelvic (n = 7) examinations were planned by
selection of scan parameters from the patient image gallery that would result
in the lowest radiation dose for an image quality considered acceptable for
visualization of the scanned region according to the as low as reasonably
achievable principle [5]. The
optimized parameters were prospectively used on a 16-MDCT scanner (Sensation
16, Siemens Medical Solutions). The parameters for the clinical CT scans had
to be identical to those of the simulated images. Because the image gallery in
the prototype version did not provide each weight group every possible peak
kilovoltage, the tube voltage was 100 or 120 kVp. Depending on the clinical
question and patient size for spatial resolution, the collimation was 16
x 1.5 mm with a 24- to 30-mm/rotation table speed or 16 x 0.75 mm
with a 12- to 13.5-mm/rotation table speed. The reconstructed slice thickness
for the study was 5 mm. Gantry cycle time was always 0.5 second. Each of the
clinical MDCT scans was obtained with reconstruction kernels and increments
identical to those for the image gallery.
Image Evaluation of Clinical Scans
For qualitative analysis, all images obtained at CT examinations and the
simulated images from the image gallery were read independently on a
workstation (Leonardo, Siemens Medical Solutions) by three radiologists with
expertise in pediatric radiology. The real and simulated images were displayed
at soft-tissue (kernel, B30f; width, 400 H; level, 80 H) and lung (kernel,
B60f; width, 1,200 H; level, –700 H) windows. The images were read at
random with the readers blinded to patient information and scanning technique.
The blinded radiologists reviewed the images using a 4-point grading scale of
the image quality in which they considered image noise and artifacts (1,
excellent image quality without artifacts, borders sharply delineated, no
image noise; 2, good diagnostic image quality with minor to moderate
artifacts, impaired but not troublesome border delineation, slightly increased
image noise; 3, fair diagnostic image quality with artifacts and impaired but
sufficient border delineation, increased image noise; 4, nondiagnostic image
quality). The grades determined by the three radiologists were combined, and
the median value was used for statistical analysis.
Objective image evaluation was performed by measurement of CT attenuation
on the scanner workstation by placement of an individually adapted circular
region of interest (ROI) in the muscles (thorax and upper abdomen;
autochthonous muscles; pelvis; psoas muscle) in mediastinal and abdominal
windows on four slices on both real and simulated reduced tube
current–time images at the same level
(Fig. 2). Because we could not
ensure identical applications of contrast media in the reference patients for
the image gallery and the patients in the actual images, for example owing to
different sizes of venous access, precise ROI measurement in the aorta was not
performed. Therefore, ROI placement was done in homogeneous regions of the
muscles by one investigator, who did not assess subjective image quality and
was blinded to the tube current–time settings. The SD of the attenuation
measurements of the ROIs was assigned to image noise. These values were
averaged for each patient and scan of the image gallery.
Statistical Analysis
The effective dose, dose–length product, and volume CT dose index as
parameters of radiation exposure were calculated with a software application
(CT-Expo V1.5, Medizinische Hochschule Hannover)
[6] and summarized with median,
mean, and corresponding SD. In calculation of these parameters, patients were
assigned to three body weight groups according to the computer program: less
than 10 kg, less than 30 kg, and 30 kg and greater. The percentage dose
reduction compared with that in a previously used weight-adapted protocol for
imaging of children (chest peak kilovoltage, 120 kVp; chest effective tube
current–time product, 120 mAs; abdominopelvic peak kilovoltage, 120 kVp;
abdominopelvic effective tube current–time product, 165 mAs) was
determined. In a previously recommended pediatric protocol
[7], body weight was multiplied
by 1 for chest examinations and by 2.5 for abdominal MDCT to specify the
effective tube current–time setting at 120 kVp (effective tube
current–time product, at least 20 mAs).
We compared the scores for the images that had a computer-simulated reduced
tube current–time product with the images that had an actual reduced
tube current–time product by calculating the kappa coefficient
(). A kappa coefficient of 0.81–1.00 indicated very good,
0.61–0.80 good, and 0.41–0.60 moderate concordance between groups
[8]. The corresponding 95% CI
for the true value of kappa also was calculated. The concordance of the SD of
the attenuation measurements between image gallery and CT scans was analyzed
with Bland-Altman plots. The degree of concordance was quantified by
calculation of the concordance correlation coefficient (K)
[9] with corresponding 95% CI.
Statistical analyses were conducted with the SAS version 9.1 (SAS Institute)
and S-Plus version 6.1 (Insightful) statistical analysis software packages and
with the Excel (Microsoft Office XP Standard) spreadsheet application.
Results
Images from all examinations were read in clinical routine without
complaints about image quality. Statistical analysis showed mainly moderate
concordance in visually assessed image quality
(Table 1) and in image noise
(Table 2) between the clinical
and simulated scans. The subjective rating for abdominal CT even showed
maximal concordance without dissemination. The Bland-Altman plots are
displayed in Figure 3A,
3B,
3C.
Table 3 gives an overview of
the calculated dose values and reductions in effective dose compared with the
aforementioned pediatric protocols for different body regions and weight
groups. The results indicate that, depending on weight group, the patient
image gallery enabled minor decreases or increases in radiation dose for chest
MDCT (Fig. 4A,
4B,
4C,
4D) but considerable dose
reduction for both abdominal (Fig.
5A,
5B) and pelvic (Fig.
6A,
6B) MDCT compared with a
previously used weight-adapted pediatric protocol.
View larger version (7K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3A —Bland-Altman plots for objective analysis of examined body
regions. Graph shows results for chest. All values are within lower and upper
agreement limits (dotted lines). Concordance correlation coefficient
is 0.6933. Mean value of differences between image gallery and CT is
–0.2133 (black line apart from zero line).
|
|
View larger version (7K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3B —Bland-Altman plots for objective analysis of examined body
regions. Graph shows results for abdomen. Concordance correlation coefficient
is 0.3300. Mean value of differences between image gallery and CT is
0.1500.
|
|
View larger version (7K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3C —Bland-Altman plots for objective analysis of examined body
regions. Graph shows results for pelvis. Concordance correlation coefficient
is 0.5486. Mean value of differences between image gallery and CT is
1.8571.
|
|
View this table:
[in this window]
[in a new window]
|
TABLE 3: Calculated Dose Values for Examinations Planned with Simulated Images
and Relative Dose Reductions for Effective Dose for Clinical MDCT Compared
with Virtually Calculated Previously Used Weight-Adapted Pediatric
Protocols
|
|
View larger version (80K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4A —9-year-old 26-kg girl with mediastinal lymphoma and pleural
effusion. All images were rated good diagnostic quality. Computer-simulated
images (patient image gallery) for 30-kg body weight at 120 kVp and 28-mAs
effective tube current–time setting in soft-tissue (A) and lung
(B) windows with mean image noise of 10.5 H.
|
|
View larger version (84K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4B —9-year-old 26-kg girl with mediastinal lymphoma and pleural
effusion. All images were rated good diagnostic quality. Computer-simulated
images (patient image gallery) for 30-kg body weight at 120 kVp and 28-mAs
effective tube current–time setting in soft-tissue (A) and lung
(B) windows with mean image noise of 10.5 H.
|
|
View larger version (121K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4C —9-year-old 26-kg girl with mediastinal lymphoma and pleural
effusion. All images were rated good diagnostic quality. Clinical chest MDCT
scan corresponding to A and B obtained with true tube current at
soft-tissue (C) and lung (D) windows. Mean image noise is 12.1
H; volume CT dose index, 3.7 mGy; effective dose, 1.9 mSv. Dose was not
reduced in comparison with weight-adapted standard pediatric protocol.
|
|
View larger version (33K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4D —9-year-old 26-kg girl with mediastinal lymphoma and pleural
effusion. All images were rated good diagnostic quality. Clinical chest MDCT
scan corresponding to A and B obtained with true tube current at
soft-tissue (C) and lung (D) windows. Mean image noise is 12.1
H; volume CT dose index, 3.7 mGy; effective dose, 1.9 mSv. Dose was not
reduced in comparison with weight-adapted standard pediatric protocol.
|
|
View larger version (130K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5A —7-year-old 25-kg girl with splenic rupture. Both images were
rated good diagnostic quality. Computer-simulated image (patient image
gallery) for 30-kg body weight at 120 kVp and 41-mAs effective tube
current–time setting with mean image noise of 8.8 H.
|
|
View larger version (106K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5B —7-year-old 25-kg girl with splenic rupture. Both images were
rated good diagnostic quality. Clinical abdominal MDCT scan corresponding to
A obtained with true tube current shows splenic rupture
(arrow). Mean image noise, 9.2 H; volume CT dose index, 5.8 mGy;
effective dose, 2.6 mSv; 37% dose reduction compared with previously
recommended weight-adapted standard pediatric protocol.
|
|
View larger version (124K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6A —13-year-old 36-kg girl with right ovarian abscess. To avoid
sedation, MRI was not performed. Both images were rated good diagnostic.
Computer-simulated image (patient image gallery) for 40-kg body weight at 120
kVp and 57-mAs effective tube current–time setting with mean image noise
of 11.9 H.
|
|
View larger version (114K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6B —13-year-old 36-kg girl with right ovarian abscess. To avoid
sedation, MRI was not performed. Both images were rated good diagnostic.
Clinical plelvic MDCT scan corresponding to A obtained with true tube
current shows right ovarian abscess (arrow). Mean image noise is 11.1
H; volume CT dose index, 4.3 mGy; effective dose, 2.7 mSv; 37% dose reduction
compared with standard pediatric protocol.
|
|
Discussion
Pediatric patients are up to 10 times more sensitive to radiation than
adults [1]. It therefore is
essential to consider optimizing scanning parameters for pediatric examination
protocols while keeping radiation exposure as low as possible. Radiation dose,
however, depends not only on scanning parameters but also on scan design. For
example, overbeaming and overscanning contribute to overall radiation
exposure, and they differ according to the number of detector rows (four, 16,
32, and 64). Several articles about dose reduction in pediatric CT have been
published [7,
10–15],
but a systematic evaluation with children is difficult, especially because of
radiation risk [1].
Several strategies are possible for assigning an individual pediatric
protocol. Patient age or weight typically is used for this purpose
[7,
12–15].
Haaga [16] suggested using the
patient's diameter to determine CT parameters. The optimal variable to use
would be the cross-sectional area presented to the scanning plane
[17]. Nevertheless, it is a
well-accepted method and in clinical routine still the easiest strategy to use
patient body weight to adjust scanning parameters, even though there are
inaccuracies [10,
12]. Because of the variety of
clinical questions, it is difficult to establish uniform protocols that follow
the patient's body weight alone. We therefore used a different approach in our
study. Use of a patient image gallery consisting of "standard"
patients representing different body weight groups yielded a prospective
impression of dose reduction. Not only the patient body weight but also the
image quality needed for answering the clinical question can be taken into
account before selection of the technical parameters at the scanner console.
We did not evaluate this aspect, but it has been reported
[11] that reducing tube
current does not affect detection of high-visibility structures as much as it
does depiction of low-visibility structures. Because radiation dose varies
linearly with tube current at a fixed peak kilovoltage and scanning time, the
minimum tube current that yields a diagnostically sufficient image for the
clinical question is optimal
[7,
10,
11,
14,
15]. According to this
principle, with a patient image gallery one can change the tube current for
each weight group to learn the effect of lower or higher effective tube
current–time settings on image quality.
The addition of image noise to real CT studies by computer simulation has
been implemented as a way of producing a range of scans with noise equivalent
to reduction of dose levels in single-detector helical CT and 4-MDCT of the
chest [18,
19] and in 4-MDCT of the
abdomen [11]. The technique
requires access to the raw projection data and addition of statistical noise
appropriate to the lower exposure level before reconstruction. Experienced
radiologists [18] were unable
to differentiate simulated reduced-dose CT images from real reduced-dose CT
images in single-detector helical chest CT of adults, but they compared the
images on only two levels in the same patient. It is even more challenging to
compare different patients—patient image gallery versus real
patients—as in our study. In the aforementioned study
[18] the amount of image noise
was measured in the descending aorta. We did not use this method because we
could not guarantee equal enhancement level and homogeneity because our
computer-simulated images were of patients other than those in the clinical
images. Therefore, for interindividual comparison of image noise, the ROI was
placed in the muscles, although we were aware that this placement does not
represent the image noise of the center of the body. Mayo et al.
[18] did not take into account
differences in patient size for their simulations, whereas our simulation
program had different weight groups.
Frush et al. [11] examined
the effect of simulated dose reduction on detection of low- and
high-visibility structures in the abdomen. Scanning parameters were 120 mA,
140 kVp with a 2.5-detector configuration, 15-mm table speed, and 0.8-second
gantry cycle (96 mAs). These parameters were identical for both phantom
validation and computer simulations of the clinical CT scans. High-visibility
structures were seen equally well at any level of tube current simulation, but
a significant association between tube current and detection of low-visibility
structures was found at 60 mA for the hepatic artery and 80 mA for the bile
duct. A limitation of that study
[11] was the high tube voltage
(140 kVp), which is no longer state of the art
[7,
13,
14].
In our investigation, the moderate concordance of the objective and the
subjective analyses emphasizes that real images are comparable with those from
a patient image gallery. Results of objective and subjective analysis do not
always agree in terms of coefficient values. For subjective image quality, not
only image noise but also contrast enhancement phase and body fat distribution
are important. Furthermore, one must be aware of restrictions in use of a
patient image gallery. Differences in physical characteristics, such as no or
very large breasts and large tumor formations, can affect image noise.
Differences in contrast administration and in breathing-related artifacts also
can influence scoring.
With use of the patient image gallery for abdominal and pelvic MDCT, we
decreased the effective dose up to 63.3% and 60.0%, respectively, compared
with a previously recommended weight-adapted standard pediatric protocol. The
profit for thoracic MDCT was not significant, the reduction in effective dose
being up to 16.7%. This difference occurred primarily because selection of
tube current–time settings for the image gallery as an infinitely
variable reduction of the tube current–time product is not yet possible.
We suggest, however, that with a wider variety of selectable tube
current–time settings, dose reduction may be possible for chest CT.
There were limitations to our study. Because of different patient sizes,
the ROIs for image noise measurement were not always the same size, but within
one weight group ROIs were identical. Because of the limited number of
patients, we did not compare every simulated image in every weight group.
Because this study was an evaluation of a basic approach, the patient image
gallery consisted mainly of 120-kVp examinations. At present, however, 80-kVp
protocols for patients weighing less than 50 kg are recommended
[13]. Our intention is further
improvement of the tool with a wider variety of CT parameters, especially CT
at 80 and 100 kVp. This development would be of especial interest in imaging
of neonates and infants to achieve even greater dose reduction. A high-dose
reference group does not exist because recruitment of such a group would be
ethically unjustifiable on the basis of the results of earlier investigations
[7,
10,
11,
13,
14].
Especially radiosensitive organs are the gonads, breasts, and thyroid.
Although we used gonad shields for boys, we did not use bismuth breast or lead
thyroid shields. Phantom studies
[20] and clinical studies with
children [21] have shown a
decrease in radiation dose without impairment of image quality.
Another limitation of this study was that our results were scanner
specific. We did not evaluate whether the patient image gallery is applicable
to other MDCT scanners made by the same manufacturer or to scanners made by
other manufacturers. The radiation dose parameters calculated with a
commercially available computer program also were not patient specific. The
calculated values were based on phantom measurements. The computed volume CT
dose index, dose–length product, and effective dose in this study were
estimates of the radiation exposure because every patient has a unique body
shape and tissue composition. Thus our intention was not to calculate the
actual dosage but to estimate the relative percentage dose reduction,
comparing the previously used pediatric protocol with the protocols derived
from the patient image gallery.
A patient image gallery is applicable in clinical routine. It allows
preexamination evaluation of the effect of dose reduction on diagnostic image
quality with regard to patient weight without exposing patients to radiation.
With a patient image gallery, the radiologist can prospectively identify
acceptable image quality for a specific clinical question. The ability to
visualize changes in image quality and reduce tube current–time product
leads to a reduction in radiation exposure in pediatric MDCT.
Acknowledgments
We thank Sven Stanzel, Institute of Medical Statistics, University Hospital
RWTH, Aachen, Germany, for help with statistical analysis and Michael Barker,
Department of Pediatrics, University Hospital RWTH, Aachen, Germany, for
professional assistance.
References
- Brenner DJ, Elliston CD, Hall EJ, Berdon WE. Estimated risks of
radiation induced fatal cancer from pediatric CT. AJR2001; 176:289
–296[Abstract/Free Full Text]
- Paterson A, Frush DP, Donnelly LF. Are settings adjusted for
pediatric patients? AJR 2001;176
: 297–301[Abstract/Free Full Text]
- Haras G. Method for determining acquisition parameters
for a medical tomography device and an associated apparatus.
Patent DE 10 2005 001 681 A1. 2005
- Hohl C, Mahnken AH, Klotz E, et al. Radiation dose reduction to the
male gonads during MDCT: the effectiveness of a lead shield.
AJR 2005; 184:128
–130[Abstract/Free Full Text]
- Slovis TL. The ALARA concept in pediatric CT: myth or reality?
Radiology 2002;223
: 5–6[Free Full Text]
- Stamm G, Nagel HD. CT-Expo—a novel program for dose
evaluation in CT. Rofo 2002;174
:1570
–1576[Medline]
- Honnef D, Wildberger JE, Stargardt A, et al. Multislice spiral CT
(MSCT) in pediatric radiology: dose reduction for chest and abdomen
examinations. Rofo 2004;176
:1021
–1030[Medline]
- Altman DG. Practical statistics for medical
research. Boca Raton, FL: Chapman & Hall,1991
- Lin LI. A concordance correlation coefficient to evaluate
reproducibility. Biometrics 1989;45
: 255–268[CrossRef][Medline]
- Donnelly LF, Emery KH, Brody AS, et al. Minimizing radiation dose
for pediatric body: applications of single-detector helical
CT—strategies at a large children's hospital.
AJR 2001; 176:303
–306[Free Full Text]
- Frush DP, Slack CC, Hollingsworth CL, et al. Computer simulated
radiation dose reduction for abdominal multidetector CT of pediatric patients.
AJR 2002; 179:1107
–1113[Abstract/Free Full Text]
- Frush DP, Soden B, Frush KS, Lowry C. Improved pediatric
multidetector body CT using a size-based color-coded format.
AJR 2002; 178:721
–726[Abstract/Free Full Text]
- Siegel MJ. Multiplanar and three-dimensional multi-detector row CT
of thoracic vessels and airways in the pediatric population.
Radiology 2003;229
: 641–650[Abstract/Free Full Text]
- Vock P. CT radiation exposure in children: consequences of the
American discussion for Europe. Radiologe2002; 42:697
–702[CrossRef][Medline]
- Brody AS. Thoracic CT technique in children. J Thorac
Imaging 2001; 16:259
–268[CrossRef][Medline]
- Haaga JR. Radiation dose management: weighing risk versus benefit.
AJR 2001; 177:289
–291[Free Full Text]
- Kalra MK, Maher MM, Toth TL, et al. Strategies for CT radiation
dose optimization. Radiology 2004;230
: 619–628[Abstract/Free Full Text]
- Mayo JR, Whittall KP, Leung AN, et al. Simulated dose reduction in
conventional chest CT: validation study. Radiology1997; 202:453
–457[Abstract/Free Full Text]
- Mahnken AH, Wildberger JE, Simon J, et al. Detection of coronary
calcifications: feasibility of dose reduction with a body weight-adapted
examination protocol. AJR 2003;181
: 533–538[Abstract/Free Full Text]
- Hohl C, Wildberger JE, Süss C, et al. Radiation dose reduction
to breast and thyroid during MDCT: effectiveness of an in-plane bismuth
shield. Acta Radiol 2006;47
: 562–567[CrossRef][Medline]
- Fricke BL, Donnelly LF, Frush DP, et al. In-plane bismuth breast
shields for pediatric CT: effects on radiation dose and image quality using
experimental and clinical data. AJR 2003;180
: 407–411[Abstract/Free Full Text]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Abstract
Introduction
