Patient-specific dose calculations for pediatric CT of the chest, abdomen and pelvis

• Published in: Pediatric radiology Vol. 45; no. 12; pp. 1771 - 1780
• Main Authors: Kost, Susan D., Fraser, Nicholas D., Carver, Diana E., Pickens, David R., Price, Ronald R., Hernanz-Schulman, Marta, Stabin, Michael G.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-11-2015; Springer Nature B.V
• Subjects: Adolescent; Child; Child, Preschool; Female; Humans; Imaging; Infant; Male; Medicine; Medicine & Public Health; Monte Carlo Method; Multidetector Computed Tomography - statistics & numerical data; Neuroradiology; Nuclear Medicine; Oncology; Original Article; Pediatrics; Pelvis - diagnostic imaging; Radiation Dosage; Radiography, Abdominal - statistics & numerical data; Radiography, Thoracic - statistics & numerical data; Radiology; Ultrasound; Children; Effective dose; Computed tomography; Monte Carlo; Organ dose; Patient size
• ISSN: 0301-0449; 1432-1998
• DOI: 10.1007/s00247-015-3400-2

Background
Organ dose is essential for accurate estimates of patient dose from CT.
Objective
To determine organ doses from a broad range of pediatric patients undergoing diagnostic chest–abdomen–pelvis CT and investigate how these relate to patient size.
Materials and methods
We used a previously validated Monte Carlo simulation model of a Philips Brilliance 64 multi-detector CT scanner (Philips Healthcare, Best, The Netherlands) to calculate organ doses for 40 pediatric patients (M:F = 21:19; range 0.6–17 years). Organ volumes and positions were determined from the images using standard segmentation techniques. Non-linear regression was performed to determine the relationship between volume CT dose index (CTDI
vol
)-normalized organ doses and abdominopelvic diameter. We then compared results with values obtained from independent studies.
Results
We found that CTDI
vol
-normalized organ dose correlated strongly with exponentially decreasing abdominopelvic diameter (R
2
 > 0.8 for most organs). A similar relationship was determined for effective dose when normalized by dose-length product (R
2
 = 0.95). Our results agreed with previous studies within 12% using similar scan parameters (e.g., bowtie filter size, beam collimation); however results varied up to 25% when compared to studies using different bowtie filters.
Conclusion
Our study determined that organ doses can be estimated from measurements of patient size, namely body diameter, and CTDI
vol
prior to CT examination. This information provides an improved method for patient dose estimation.