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Radiation Dose for Small Bowel Follow-through Varies Widely

October 19, 2008
Written by: , Filed in: Gastrointestinal Imaging, Pediatric Radiology
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The objective of a recent study was to determine organ and effective radiation doses from small-bowel follow-through (SBFT) and abdomen/pelvis mutidetector array CT (MDCT) scans in a pediatric population with Crohn’s disease.

The study has concluded that the effective radiation dose for MDCT might be up to twice that for SBFT, with the majority of the dose on SBFT coming from the overhead abdominal radiography portion of the study.

Methodology
What comprises an SBFT was determined based on average fluoroscopy time and number of abdominal radiographs. The medical records were retrospectively reviewed for 30 pediatric patients with Crohn’s disease during a 1.5-year study interval. Patients younger than age 8 years were excluded, but children undergoing a combination of UGI/SBFT were included.

A 10-year-old anthropomorphic phantom abdomen was used to record radiation doses to the pediatric abdomen/pelvis with CT scan and SBFT.

For reproducing fluoroscopic dosages, three areas of the abdomen were exposed to 5 minutes of direct continuous fluoroscopy defined as central abdomen, right lower quadrant, and pelvis.

The effective dose (ED) from abdominal radiographs was used from the literature and multiplied by the average number of abdominal radiographs obtained during a SBFT.

Using a weight-based pediatric 16-slice MDCT protocol, the pediatric phantom was scanned three times to determine organ doses, EDs, and standard deviations.

Review for Practicing Radiologists The University of California, San Francisco School of Medicine, Department of Radiology and Biomedical Imaging Review for Practicing Radiologists an intensive clinical radiologic review and self-assessment covering the following radiology subspecialties: Vascular-Interventional, Breast, Neuro, Gastrointestinal and Pulmonary Imaging. The program is designed for radiologists in clinical practice. Click here to read more or order: Review for Practicing Radiologists

Results of the Study
The average fluoroscopy time per study was 5.1 minutes, and each child averaged 3.3 abdominal radiographs. The average patient underwent one SBFT or UGI/SBFT and one MDCT.

For 5 minutes of fluoroscopy, the EDs to the three areas of the abdomen were:

  • central abdomen, 0.35 mSv;

  • right lower quadrant, 0.15 mSv;
  • pelvis, 0.56 mSv.

When including abdominal radiography, a total dosage of 1.8-2.2 mSv was calculated (75%-92% of this dosage resulted from abdominal radiography). The ED to the phantom from the abdomen/pelvis MDCT scan was 3.48 mSv.

Conclusions
The ED for a pediatric adjusted abdomen/pelvis MDCT scan may be up to two times greater than that for an average pediatric SBFT. Most of the ED from an SBFT is from the abdominal radiographs. Given that the average child underwent one SBFT and one CT scan, the average ED per patient was 5.3-5.7 mSv during the course of their follow-up for Crohn’s disease.

Reviewer’s Comments
Although this is the first study to report dosages for pediatric patients with Crohn’s disease, whether this data will change imaging utilization patterns is questionable.

Even the authors of the article allude to the fact that most children are managed clinically and not through imaging. Therefore, under current patient management practices, 5.7 mSv seems like an acceptable dose for children.

Author:
Basil Hubbi, MD

Reference:

Gaca AM, Jaffe TA, et al. Radiation Doses From Small-Bowel Follow-Through and Abdomen/Pelvis MDCT in Pediatric Crohn’s Disease. Pediatr Radiol; 2008; 38 (March): 285-291

Review for Practicing Radiologists The University of California, San Francisco School of Medicine, Department of Radiology and Biomedical Imaging Review for Practicing Radiologists an intensive clinical radiologic review and self-assessment covering the following radiology subspecialties: Vascular-Interventional, Breast, Neuro, Gastrointestinal and Pulmonary Imaging. The program is designed for radiologists in clinical practice. Click here to read more or order: Review for Practicing Radiologists
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