NCI Dosimetry System for Radiography and Fluoroscopy

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The National Cancer Institute Dosimetry System for Radiography and Fluoroscopy (NCIRF) 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 diagnostic radiography, fluoroscopy, and fluoroscopically guided interventional procedures.

NCIRF integrates computational human phantoms with a streamlined GEANT4 Monte Carlo radiation transport engine. Unlike NCICT and NCINM, which rely on pre-calculated dose conversion coefficients, NCIRF performs direct Monte Carlo radiation transport simulations based on user-specified imaging and geometric parameters.

NCIRF supports population-based dose evaluation, benchmarking, and regulatory-facing analyses, rather than real-time or patient-specific clinical dose estimation.

Intended use
NCIRF is intended for reference dose reconstruction and comparative analyses.
It is not intended for real-time clinical decision support or site-specific clinical optimization.

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Step	Description
1	Select phantom library and patient characteristics
2	Define x-ray beam spectrum and output
3	Specify beam geometry and isocenter
4	Run Monte Carlo simulations
5	Review organ and effective dose output

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Two libraries of computational human phantoms are available in NCIRF 3.0:

• Reference size phantoms
• Size-specific phantoms

Reference size phantoms are categorized by body posture:

• Arms Raised
• Arms Lowered
• Arms Rotated

Users select patient age and gender from ICRP-defined reference groups. Reference height and weight are displayed automatically and are not editable.

For patients whose ages fall between reference groups, users may interpolate organ doses or select the nearest reference age group.

View reference-size phantom selection

Size-specific phantoms include:

• 169 pediatric models (79 male, 90 female)
• 193 adult models (93 male, 100 female)

Users specify age group, gender, height (cm), and weight (kg). Selection of the appropriate age group is essential for accurate calculation of active and shallow bone marrow doses, which rely on age-dependent dose response functions.

View size-specific phantom selection and height–weight map

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Users define the x-ray beam spectrum by selecting combinations of:

• Peak tube potential (kVp)
• Half-value layer (HVL, mm Al)

A predefined set of kVp–HVL combinations is provided in NCIRF 3.0.

Additional parameters include:

• Source-to-isocenter distance (SID, cm)
• Field width and height at isocenter (cm)
• Dose Area Product (DAP, Gy·cm²)

DAP is required to convert Monte Carlo–derived dose per particle into absolute absorbed organ doses.

View x-ray beam parameter input

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Beam orientation is defined using:

• Positioner Primary Angle (PPA)
• Positioner Secondary Angle (PSA)

Angles may be entered numerically, adjusted using arrow controls, or selected from predefined beam directions consistent with the NEMA DICOM standard.

View beam geometry definition

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Phantom views (top, frontal, and lateral) display:

• Isocenter location
• Beam width and height
• X-ray source position and beam direction

Users may reposition the isocenter interactively. Patient bed thickness (Bed Thickness, cm) is explicitly included in Monte Carlo calculations.

View phantom and beam geometry

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Users specify the number of Monte Carlo histories to control statistical uncertainty.

From NCIRF version 2.0 onward, multithreading is supported, with options ranging from 1 to 24 threads. Optimal performance typically corresponds to the number of available CPU cores.

Monte Carlo simulations are executed in the background using GEANT4.

Note: During Monte Carlo execution, the user interface may appear temporarily unresponsive.

View Monte Carlo performance scaling

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Following completion of the simulation, the output table reports:

• Organ absorbed doses (mGy)
• Monte Carlo statistical uncertainties (%)

Effective dose (mSv) is calculated using tissue weighting factors defined in ICRP Publication 103.

From NCIRF version 2.0 onward, peak skin dose (PSD) is also calculated. Approximately 10⁵ histories are typically sufficient to achieve stable PSD estimates.

View dose output

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Batch Manager supports automated execution of multiple simulation cases.

Two versions are available:

• Batch Manager – Reference size
• Batch Manager – Size-specific

Batch parameter sets may be saved, loaded, and executed. In addition, MCNP input files may be generated for execution on external computing environments.

View Batch Manager interfaces