KERMA ratios vs. SSDE: is one better at estimating pediatric CT radiation doses?

Department of Radiology, Cincinnati Children's Hospital Medical Center, MLC 5031, 3333 Burnet Ave., Cincinnati, OH, 45229-3026, USA, .
Pediatric Radiology (Impact Factor: 1.57). 03/2012; 42(5):525-6. DOI: 10.1007/s00247-012-2371-9
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    ABSTRACT: OBJECTIVE: Medical physicists currently use two standardized phantoms to estimate CT patient radiation dose. This "one-size-fits-all" adult model results in underestimates of displayed pediatric CT radiation dose on the console of current CT scanners. The purpose of this article is to discuss the Alliance for Radiation Safety in Pediatric Imaging Vendor Summit. CONCLUSION: Stakeholders were invited to discuss the development of better estimates of pediatric patient radiation dose. These stakeholders agreed to partner to improve CT radiation dose estimates for children.
    American Journal of Roentgenology 06/2009; 192(5):1169-75. DOI:10.2214/AJR.08.2172 · 2.73 Impact Factor
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    ABSTRACT: Patient organ doses may be estimated from CTDI values. More accurate estimates may be obtained by measuring KERMA (Kinetic Energy Released in Matter) in anthropomorphic phantoms and referencing these values to free-in-air X-ray intensity. To measure KERMA ratios (R(K)) in pediatric phantoms at CT. CT scans produce an air KERMA K in a phantom and an air KERMA K(CT) at isocenter. KERMA ratios (R(K)) are defined as (K/K(CT)), measured using TLD chips in phantoms representing newborns to 10-year-olds. R(K) in the newborn is approximately constant. For the other phantoms, there is a peak R(K) value in the neck. The median R(K) values for the GE scanner at 120 kV were 0.92, 0.83, 0.77 and 0.76 for newborns, 1-year-olds, 5-year-olds and 10-year-olds, respectively. Organ R(K) values were 0.91 ± 0.04, 0.84 ± 0.07, 0.74 ± 0.09 and 0.72 ± 0.10 in newborns, 1-year-olds, 5-year-olds and 10-year-olds, respectively. At 120 kV, a Siemens Sensation 16 scanner had R(K) values 5% higher than those of the GE LightSpeed Ultra. KERMA ratios may be combined with air KERMA measurements at the isocenter to estimate organ doses in pediatric CT patients.
    Pediatric Radiology 03/2012; 42(5):527-35. DOI:10.1007/s00247-011-2336-4 · 1.57 Impact Factor
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    ABSTRACT: The purpose of our study was to measure patient size on CT images as a function of age at a large tertiary care children's hospital to develop current patient size data for modeling optimal x-ray exposure factors in children. Anteroposterior and transverse dimensions of the head, thorax, abdomen, and pelvis were measured on CT examinations of pediatric patients less than 21 years old performed between June and November 2007. Patients with diseases that could affect measurements were excluded. From 1,009 patients, 336 examinations of each of four body regions were selected; 2,688 measurements were made and separated into 21 groups. Statistical model building and prediction equations were established for each region and 95% prediction intervals were used for analyses. Rapid growth of the head occurred from birth to approximately 2 years followed by a gradual plateau until 21 years. The thoracic, abdominal, and pelvic regions showed a linear relationship between age and size. Fitted equations showed transverse trunk measurements increased more rapidly than anteroposterior measurements. The anteroposterior trunk size growth rate was relatively region independent; transverse pelvic dimensions grew more rapidly than thoracic or abdominal regions. There was a broad overlap of predicted patient size ranges as a function of age within each region. Excellent interobserver agreement was measured by Pearson's correlation coefficient (r) (all p < 0.0001). Fitted average patient sizes are age dependent; however, predicted individual patient size does not correlate well with age. Our study suggests that pediatric patient body size should be determined for individual patients before performing diagnostic imaging procedures that entail radiation risks.
    American Journal of Roentgenology 06/2010; 194(6):1611-9. DOI:10.2214/AJR.09.3771 · 2.73 Impact Factor


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