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Great Ormond Street Hospital for Children London WC1N 3JH, UK
Why does the AJR pontificate on the radiation hazards of CT in the pediatric population [1–4] and then publish an article about CT examinations in children—most of which were not necessary? We radiologists must resist providing "pretty pictures" for clinicians when obtaining these pictures is not in the child's best interests.
In the study by Ko
ucu et al.
[4], five of the patients had a
clear history of foreign-body aspiration before CT and bronchoscopy
[4], and two patients had
radiopaque foreign bodies visible on chest radiographs. Bronchoscopy was
mandatory in all these children, but the CT examinations were superfluous. In
many of the others, the likelihood of foreign-body aspiration must have been
high because they all had bronchoscopy within 24 hr of CT.
When the possibility of an aspirated foreign body is a real concern, bronchoscopy must be performed. These foreign bodies are removed with a rigid bronchoscope. When the likelihood of an aspirated foreign body is low, an admittedly gray area, some pediatricians perform flexible bronchoscopy to exclude a foreign body; if a foreign body is found and a rigid scope and a person capable of using a rigid bronchoscope are available, they switch to a rigid bronchoscope during the same examination to avoid administering an anesthetic twice.
The important question with regard to CT in possible cases of foreign-body
aspiration in children is not, Can CT detect foreign bodies that you know are
present or are so likely to be present that bronchoscopy is inevitable? The
question is, Is CT reliable enough, when the likelihood of foreign-body
aspiration is low, such that bronchoscopy can be safely omitted? The study by
Koucu et al. [4] does
not address the latter question specifically, although the authors mention it
in the concluding paragraph of their article. Their findings—in eight
children, no foreign body was seen on CT, and none was found at
endoscopy—are encouraging. In other words, a better article could have
been produced with a more specific objective.
To suggest, as Koucu et al.
[4] did, that 100 mA is used in
a typical child protocol is disingenuous (and was not referenced). That high
dose may be a typical dose administered to children in an adult department,
but our routine pediatric CT doses are in the range of 25–50 mA, and we
would rarely use a higher tube current for chest scanning; the tube current
for our patients is based on the child's weight, with no more than 20 mA for
children weighing less than 15 kg and no more than 55 mA for those weighing up
to 44 kg at the moment. In the study by Koucu et al.
[4], their use of a lower peak
kilovoltage (80 kVp) is commendable.
Radiologists should be, and many are, continuously attempting to lower CT doses in children if possible. However, in addition to adhering to the ALARA (as low as reasonably achievable) principle, radiologists must, as the first part of a dose reduction strategy, limit CT studies to only those children who truly merit CT.
 Top References References |
|---|
ucu P, Ahmetoglu A, Koramaz 
, et al. Low-dose MDCT
and virtual bronchoscopy in pediatric patients with foreign body aspiration.
AJR 2004;183:1771
–1777KTU Farabi Hospital Trabzon 61080, Turkey
My colleagues and I thank Dr. McHugh for the letter concerning our recent article in the AJR [1]. We performed MDCT and virtual bronchoscopy in children with a clear history of aspiration to confirm the presence of a foreign body and to show its exact location, so this detailed information would be available before bronchoscopy. We think that this strategy may shorten the time needed for bronchoscopy and also may help decrease possible complications of the procedure. In our study, a radiopacity was seen on chest radiography that was compatible with a foreign body in two cases, and MDCT could have been avoided in those cases.
We think that MDCT can be performed to rule out a foreign body in patients without a clear history of aspiration with pulmonary infiltrates that fail to resolve in the usual amount of time; in patients with chronic, unexplained respiratory symptoms; and in patients with a low level of suspicion and normal or nonspecific findings on chest radiography. The issue in question—whether CT is reliable enough to safely omit bronchoscopy when the likelihood of foreign-body aspiration is low—cannot be answered by our study because ours is a preliminary investigation with a relatively small number of patients; thus, the answer lies in the future work with larger series. Few studies regarding the use of CT virtual bronchoscopy in children have been published in the literature [2–4]. The tube current values in the protocols for those studies were 110, 100, and 100 mA, respectively.
Over the past several years and during the time of our study, there was a strong tendency to minimize radiation doses in pediatric CT. We now use 25- to 50-mA (mean, 35 mA) tube currents with 80 kV. Thus, we reduced the radiation dose to a reasonable level. Now, in clinical practice, this protocol enables us to obtain good quality images without loss of diagnostic imaging.
|
TopReferencesReferences |
|---|
ucu P, Ahmetoglu A, Koramaz I, et al. Low-dose MDCT and
virtual bronchoscopy in pediatric patients with foreign body aspiration.
AJR 2004;183:1771
–1777
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