KERMA ratios in pediatric CT dosimetry.

Area of Science:

• Medical Physics
• Radiological Sciences
• Diagnostic Imaging

Background:

• Computed tomography (CT)DI values offer basic patient organ dose estimates.
• Measuring Kinetic Energy Released in Matter (KERMA) in anthropomorphic phantoms provides more accurate dose assessments.
• Referencing phantom KERMA measurements to free-in-air X-ray intensity enhances accuracy.

Purpose of the Study:

• To quantify KERMA ratios (R(K)) within pediatric phantoms during CT scans.
• To establish a method for more precise pediatric CT dose estimation.
• To investigate age-specific variations in R(K) values.

Main Methods:

• KERMA ratios (R(K)) were defined as the ratio of air KERMA (K) in a phantom to air KERMA at the CT isocenter (K(CT)).
• Thermoluminescent dosimeter (TLD) chips were used to measure K in phantoms simulating newborns to 10-year-old children.
• Measurements were conducted using GE and Siemens CT scanners at 120 kVp.

Main Results:

• R(K) remained relatively constant in the newborn phantom.
• A peak R(K) value was observed in the neck region for older pediatric phantoms.
• Median R(K) values decreased with age, ranging from 0.92 in newborns to 0.76 in 10-year-olds for a GE scanner.

Conclusions:

• KERMA ratios (R(K)) can be effectively combined with isocenter air KERMA measurements.
• This combination allows for improved estimation of organ doses in pediatric CT patients.
• The study highlights the importance of age-specific dosimetry in pediatric CT.