The National Cancer Institute Dosimetry System for Radiography and Fluoroscopy (NCIRF) is a software tool designed to estimate organ and effective doses for patients undergoing diagnostic radiography, fluoroscopy, and fluoroscopically guided interventional procedures. The program utilizes computational human phantoms integrated with a streamlined GEANT4 Monte Carlo radiation transport package. Unlike NCICT and NCINM, which rely on pre-calculated dose conversion coefficients, NCIRF performs direct Monte Carlo radiation transport based on user-provided input data.

Two libraries of the computational human phantoms are implemented into NCIRF3.0: the reference size phantoms (Reference size tab) and body size-specific phantoms (Size-specific tab) with various height and mass.

The Reference Size phantoms are categorized based on body posture: arms Raised, arms Lowered, and arms Rotated. Users can specify the patient's age and gender. Age selection includes five groups: newborn, 1, 5, 10, 15 years, and adult (typically considered over 20 years). For patients with ages that fall between the ICRP-defined groups, users may: (1) interpolate organ doses between younger and older age groups (e.g., interpolate doses from the 1-year and 5-year phantoms for a 3-year-old patient), or (2) select the age group closest to the patient’s age (e.g., use the 5-year group for a 4-year-old patient). Once age and gender are selected, the reference height and weight for the corresponding reference individual, as defined by the International Commission on Radiological Protection (ICRP), will be displayed. These values are fixed and cannot be edited.

The Size-Specific phantoms include 169 pediatric models (79 males and 90 females) and 193 adult models (93 males and 100 females) with a range of heights and weights. Users can select the Age Group (pediatric or adult) and Gender (male or female). After selection, they can adjust the patient's Height (in cm) and Weight (in kg) using the up and down arrows next to the respective input boxes. A Phantom Height-Weight Map is provided, an example of the adult female shown below for reference. Selecting the appropriate Age Group is essential for NCIRF to accurately calculate active and shallow bone marrow doses by applying the correct age-dependent dose response functions.

Next, users need to select x-ray beam characteristics. A series of x-ray energy spectra, combinations of the peak tube potential and half-value layer, can be selected from the list. Below is the full list of peak tube potentials and HVLs available in NCIRF3.0.

Peak tube potential (kVp)	Half value layer (Al mm)
50	1.890
50	2.800
50	3.300
50	3.750
60	2.250
60	3.420
70	2.610
70	4.050
70	6.830
80	3.010
80	4.610
80	5.570
80	6.380
80	7.700
90	3.380
90	5.180
100	3.750
100	5.710
110	4.110
110	6.180
110	7.330
110	8.230
110	9.680
120	4.530
120	6.520

Additional parameters, such as the source-to-isocenter distance (SID) (cm), field width (cm), and field height (cm) at the isocenter, can be entered or adjusted using the up and down arrows next to the respective text boxes. Adjustments to the beam field size are automatically updated in the phantom images. However, it is important to note that the Source-to-Isocenter Distance is not visually represented in the phantom images due to space constraints. Finally, the Dose Area Product (Gy-cm²) must be entered, as it is required to convert the Monte Carlo organ dose (absorbed dose per particle launched) into absolute doses.

Users must input two angles: the Positioner Primary Angle (PPA) and Positioner Secondary Angle (PSA), corresponding to the azimuthal and polar angles in a polar coordinate system. These angles can be entered directly into the text boxes or adjusted using the up and down arrows. Changes to the angles will be reflected in the phantom images displayed in the top, front, and lateral views. Alternatively, users can select a predefined beam direction from the dropdown menu. The definitions of PPA and PSA align with the National Electrical Manufacturers Association (NEMA) DICOM standard.

The phantom is shown in top, left lateral, and frontal views based on the selected age and gender. The isocenter, as well as the width and height of the x-ray beam at the isocenter specified earlier, are visually displayed on the phantom. Users can adjust the isocenter's position on the top, lateral, and frontal views using the mouse. The red dot represents the x-ray source location, and the red arrow indicates the beam's direction. Additionally, users can specify the thickness (cm) of the patient bed, Bed Thickness(cm), which will be explicitly incorporated into the Monte Carlo radiation transport calculations.

Users must specify the number of Monte Carlo histories for the simulation. The history count can be adjusted by reviewing the Monte Carlo statistical errors displayed alongside the organ dose results. Starting from NCIRF version 2.0, multithreading is available to enhance calculation speed. Users can select the desired Number of threads for Monte Carlo simulations from a dropdown menu, offering options from 1 to 24. The selected number of threads typically corresponds to the number of CPU cores on the user's computer. While it is possible to choose a number of threads exceeding the available CPU cores, doing so may not improve performance.

Once all parameters are defined, Monte Carlo calculations are initiated when users click the Calculate Dose button. The MCNP input file is generated and converted into a Geant4-compatible format, after which the Monte Carlo radiation transport simulations are executed in the background.

Note: During the Monte Carlo calculation, the user interface may appear frozen. However, once the calculations are complete, the interface will return to normal.

In test calculations using an iMac Pro with a 2.3 GHz 18-Core Intel Xeon W processor, the number of threads correlates with the calculation time as shown below. Detailed results of the sensitivity analysis are available at Lee et al. BPEX 2023.

Once the Monte Carlo calculations are complete, the organ dose table on the right pane of the user interface will be updated with the organ absorbed doses (mGy) and Monte Carlo errors (%) next to each value. If any input parameters are changed, the organ dose table will be cleared in preparation for the next Monte Carlo run. The effective dose (mSv) is calculated using the tissue weighting factors defined in ICRP Publication 103.

Starting from NCIRF version 2.0, the peak skin dose (PSD) is also calculated through Monte Carlo radiation transport. To improve accuracy, an image smoothing technique (referred to as "dose smoothing" in NCIRF dose calculation) is applied to minimize dosimetric errors in each voxel. As a general guideline, 10⁵ histories are sufficient to achieve a stable PSD, although other organ doses may require more particle histories to reach stable results.

Batch Manager is available to automatically run multiple input files. There are two versions of Batch Manager available from NCIRF version 3.0 for Reference size phantoms and Size-specific phantoms. Batch Manager corresponding to the phantom libraries selected from Reference size or Size-specific tabs will be popped up. Depending on the phantom library currently selected, it is reflected to the button: Batch Manager - Reference size or Batch Manager - Size-specific. Different Batch Manager will be opened when those buttons are clicked.Both Batch Manager tools list the same parameters, except for those related to the phantom. Batch Manager - Reference Size includes the Phtm Lib, which represents (1) arms raised, (2) arms lowered, and (3) arms rotated. Meanwhile, Batch Manager - Size-specific includes PhtGrp, representing (1) pediatric female, (2) pediatric male, (3) adult female, and (4) adult male, as well as Height and Weight parameters.

Once the Batch Manager is opened, all user input parameters are transferred to it by clicking the Send Setting to Batch Manager button. Users can save the list of parameters in Batch Manager as a CSV file using the Save Batch Set button or load an existing batch set file using the Load Batch Set button. Double-clicking any event row in Batch Manager updates the input parameters in the user interface. Monte Carlo calculations can be initiated directly using the Run Batch Set button, and upon completion, a message saying Batch calculation is completed will appear. However, the current version does not support monitoring the status of ongoing runs. The Generate MCNP Input button creates MCNP input files for Monte Carlo simulations to be executed on external computing servers.

• Non-Commercial Research Use There is no charge to use these resources for non-commercial research purposes. Please click Software Transfer Agreement form, fill out the form in your web browser*, save it to your computer, then obtain the signatures and submit it to Dr. Choonsik Lee.
• Commercial Use Contact Dr. Kevin Chang of the NCI Technology Transfer Center to discuss accessing the free trial version and the licensing process for commercial use.