Radiology: Iterative reconstruction slashes pediatric rad dose
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| Chest CT images in a 10-year-old girl (weight, 37 kg; green zone) with a known history of rhabdomyodarcoma A, Transverse and, B, coronal images reconstructed with FBP (9.1 mGy, 88 mA, 120 kVp). Follow-up, C, transverse and, D, coronal images reconstructed with ASIR (2.9 mGy, 55 mA, 120 kVp) show ill-defined ground-glass opacity (arrow) and resulted in 68% CTDIvol reduction when compared with prior FBP images. Source: Radiology 2012;263:537-546 |
As concerns about radiation exposure have increased, CT vendors have developed techniques to help maintain image quality at reduced radiation dose. Methods include automatic exposure control and hybrid iterative reconstruction, which are designed to reduce noise. However, iterative reconstruction had not been studied among the pediatric population.
Sarabjeet Singh, MD, from the department of radiology at Massachusetts General Hospital in Boston, and colleagues conducted a retrospective analysis to assess image quality and radiation dose reduction with hybrid iterative reconstruction of pediatric chest and abdominal CT studies compared with filtered back projection (FBP).
The researchers analyzed 234 exams acquired from Jan. 1, 2009, to July 31, 2010, and compared 70 patients’ exams with their prior FBP CT studies to assess image quality.
Two pediatric radiologists independently examined exams for the 70 patients with both iterative reconstruction and FBP CT studies and graded subjective noise, visibility of small structures, diagnostic confidence, lesion detection and image artifacts.
“Despite significantly lower radiation dose associated with CT images reconstructed with the ASIR [iterative reconstruction] technique as compared with those reconstructed with the FBP technique, both radiologists found there were no substantial differences in subjective image quality metrics,” wrote Singh and colleagues.
They reported that compared with FBP, iterative reconstruction enabled dose reduction of 46.4 percent (3.7 vs. 6.9 mGy) for chest CT and 38.2 percent (5.0 vs. 8.1 mGy) for abdominal CT. Iterative reconstruction images also were associated with substantially less objective noise than FBP images (chest 13.3 +/- 3.8; abdomen, 13.8 +/-5.2), according to Singh et al.
The researchers noted the effectiveness of the automatic exposure control technique, which enabled fluctuation in tube current, and lower radiation dose, among some patients. They recommended use of automatic exposure control for this reason.
Singh and colleagues concluded by emphasizing the feasibility of the hybrid iterative reconstruction technique in children undergoing low-dose chest and abdominal CT exams as the method enables substantial dose reduction while maintaining acceptable image quality.