NCICT User Manual
NCI Dosimetry System for Computed Tomography
The National Cancer Institute Dosimetry System for Computed Tomography (NCICT) is a reference-grade radiation dose estimation system developed by the National Cancer Institute (NCI) for estimating organ absorbed doses and effective dose associated with computed tomography (CT) examinations.
NCICT is based on pre-calculated organ dose conversion coefficients derived from Monte Carlo radiation transport simulations, multiple computational human phantom models, and a reference CT scanner framework. The system supports patient-specific dose calculations, population-based dose evaluation, and benchmarking. The program is not intended for clinical decision support.
Organ dose calculations are performed through four sequential steps:
- Patient characteristics definition
- Scan parameters
- Scan coverage definition
- Organ and effective dose output
A Batch Calculation mode is provided to support automated dose reconstruction for large datasets.
NCICT supports three phantom libraries to accurately matching patient's anatomy and body dimensions.
- ICRP reference pediatric and adult phantoms (n=12)
- Body size-dependent pediatric and adult phantoms (n=360)
- Pregnant women and fetal phantoms at 8,10,15,20,25,30,35 and 38-week fetal ages
When detailed body size information is unavailable, users may select one of the ICRP-defined reference age groups and sex:
- Newborn male or female
- 1, 5, 10, or 15 years male or female
- Adult male or female (assumed ≥20 years)
When age and sex of the ICRP phantoms are selected, reference height and weight corresponding to a given phantom are assigned automatically.
If a patient’s age falls between reference groups, users may interpolate organ doses or select the nearest reference age group.
When patient height and weight are available, users may directly specify body size within the pediatric or adult phantom libraries. This approach maps the patient’s body size to the closest matching body size–dependent phantom. Phantom's height and weight can be adjusted using the + and - buttons next to the height and weight fields.
As an alternative and more intuitive way, users can click "Phantom Height Weight Map" button to display the interactive phantom size map. The blue cells representing height and weight can be selected which will be reflected on the main panel.
When fetal organ doses are of interest, users can select "Fetus" tab and fetal age ranging from 8 to 38 weeks. Since fetal age may not be proportional to the maternal diameter in pregnant patients, the maximum maternal abdominal diameter (cm) is also displayed next to the fetal age for users to select better matching pregnant women phantoms when diameter is available.
Separate tabs are provided to support fetal and maternal organ dose calculations for eight gestational ages. Maternal abdominal perimeter (cm) also can be used to select a phantom.
Two scanner parameter scenarios are supported.
Users enter CTDIvol, CTDI phantom type, and tube potential (kVp).
When CTDIvol is not available, it may be reconstructed using scanner model, tube potential (kVp), mAs, pitch, and collimation.
A vendor-neutral, generic tube current modulation (TCM) model may be applied. Average CTDIvol is computed automatically.
View TCM settings
Scan coverage may be defined interactively, numerically, or by selecting predefined NIH clinical protocols (e.g., head, chest, abdomen).
View scan range definition
NCICT reports organ absorbed doses (mGy) and effective dose (mSv). Results are appropriate for comparative and population-level analyses, rather than individual risk estimation.
View dose output table
Batch mode supports automated dose calculation using CSV-formatted input files when CTDIvol is available.