NCICT User Manual

Introduction

National Cancer Institute dosimetry system for Computed Tomography (NCICT) is a computer software developed to estimate organ and effective doses for patients undergoing computed tomography (CT) examinations. The program is based on a library of organ dose conversion coefficients calculated by Monte Carlo radiation transport simulations using computational human phantoms combined with a reference CT scanner. Organ dose calculation is conducted in four steps as described below: input patient characteristics, input scanner parameters, input scan range, and output of organ and effective doses. To automate dose calculations, Batch Calculation mode is available.

Calculation steps

Patient characteristics

You need to input the characteristics of a given patient whose organ dose is sought. Given that the gender of the patient is known, two different scenarios are assumed to decide the size of the body. The first case (shown below on the left) is when the age of the patient is available but no information on body size is known. You can select the patient’s age from five age groups: newborn, 1, 5, 10, 15 years old, and adult (generally assumed to be over 20 years). The best estimation needs to be used for in-between ages. For example, you may choose a 5 years old phantom for a 6-year-old patient. Once age is selected, the reference height and weight defined by the International Commission on Radiological Protection (ICRP) will be displayed at the bottom, which is not editable. Another scenario (shown below on the right) is when the height and weight of the patient are available. You can first choose “Age Group” between “Pediatric” and “Adult” and select gender. Within the age group, you can choose height and weight by referring to phantom maps, which will be displayed in a separate window when the button, “Show Phantom Height Weight Map”, is clicked.

Scanner parameters

You need to input technical parameters for a given CT scanner. There can be two different scenarios. First, you may have CTDIvol available from a given CT scanner, which is usually included in the dose (or protocol) page after the scan is completed. In this case, you will also need CTDI phantom type (16 cm head phantom or 32 cm body phantom) and tube potential (kVp) other than CTDIvol for dose calculation. Please select the head or body filter, which is equivalent to the type of CTDI phantom, input CTDIvol, and then skip to STEP3. When CTDIvol is not available, which is mostly the case dealing with old scanners in dose reconstruction projects, CTDIvol needs to be reconstructed using several parameters. First, please select the manufacturer and model of the CT scanner in question from the dropdown menus shown on the left. Next, please select the type of CTDI phantom between head and body. Then please input tube potential (kVp), current-time product (mAs), pitch, and total collimation (mm). Tube current modulation strength can be selected among 0.0, 0.25, 0.5, 0.75, and 1.0, which will create a generic modulation curve based on the algorithm (5). Then NCICT will select normalized CTDIw (mGy/mAs) from a built-in library and derive CTDIvol using other parameters. Pre-measured effective diameter (cm) will be shown at the bottom with the two dose descriptors, Dose-Length-Product (DLP) and Size Specific Dose Estimates (SSDE).

Scan range

Scan locations (start and end) need to be defined on the phantom selected from STEP1. You have three options. First, the red bars on the phantom can be dragged using a mouse to adjust scan locations. The other option is for you to enter scan locations in the two boxes at the bottom: scan start and scan end. The values are the distance from the top of the phantom (e.g., 10 cm of scan start means scan starts at 10 cm below the top of the head). Once the values are entered, the location of the red bars is automatically adjusted. The last option is selecting “Predefined protocol”, which is based on the protocol from the National Institutes of Health Clinical Center. There are seven options including head, neck, chest, abdomen, pelvis, abdomen-pelvis (AP), and chest-abdomen-pelvis (CAP). Once the protocol is selected, the red bars on the phantom are automatically adjusted. The predefined protocol will be kept at the same location although new phantoms are selected in STEP1.

Dose output

Once STEP1 through STEP3 is completed, organ absorbed doses (mGy) and effective dose (mSv) are displayed in the table on the right. Whenever doses are updated (e.g., when new phantom, another gender, the body size is selected, or when new scan parameters or scan locations are entered), the organ and effective doses are automatically copied to Clipboard, which can be easily pasted into other documents such as MS Word, Excel, etc. The organ names can be copied from the table by selecting the column using a mouse. The table includes all organs for which tissue weighting factors from ICRP Publication 103 are defined. It should be noted that some organ doses are rough estimations of more accurate doses to thin radiosensitive layers: the lenses, stomach wall, skin, urinary bladder, colon, small intestine. Depending on the gender selected, gender-specific organs show zero dose (e.g., dose to the prostate and testes will be zero for females). Active and shallow (bone surface in the old ICRP definition) marrow doses are calculated from fluence to spongiosa region within the skeleton combined with dose response function derived from Monte Carlo calculation for detailed spongiosa structure models. It should be also noted that the effective dose (mSv) displayed at the bottom row is not what ICRP defines. Gender-specific organ doses need to be averaged across males and females to obtain an effective dose based on the ICRP definition. The effective dose calculated for a male or female patient here is a gender-specific quantity that may be used for comparison by protocols, hospitals, scanners, etc.

Batch dose calculations

You can list patient and scan parameters into a csv-formatted file (see ncict_batch_input.csv included in the folder, NCICT3.XX) following the header (the first line of the batch input file). NCICT can import the input file and export the output organ doses. For now, the batch mode works when you know your own CTDIvol. The parameters required for batch runs include: Patient ID, Scan Start (cm), Scan End (cm), Phantom Group (1-pediatric female, 2-pediatric male, 3-adult female, 4-adult male, 5-fetus, 6-pregnant woman), Height (cm), Weight (kg), kVp, TCM Strength (0,0.25,0.5,0.75, and 1), CTDI phantom (1-16cm,2-32cm), CTDIvol(mGy). When you want to use the phantom group 5 (fetal dose) or 6 (pregnant women dose), the height and weight must be inputted as follows: phantom group = 5 (fetus phantoms), height = 164 (pregnant women height), weight = 10 (fetus gestational age in weeks), if you want to calculate fetal dose for the 10-month-old fetus).

Features under development

• TCM adjustment for adult head and pediatric patients
• Monte Carlo errors next to the organ dose list
• Lymph node dose

Version history

• 20221214 Official release version 3.0.20221123
• 20221123
  • NCICT2.0 published: Lee et al. “CT organ dose calculator size adaptive for pediatric and adult patients,” BPEX 8:065020 (2022)
• 20211123
  • Error fixed when a blank line remained in the batch file which is sometimes caused by editing csv file in Excel
• 20211120
  • Tube current profile per image slice is displayed on the left of the phantom picture.
  • “Average CTDIvol” is displayed when TCM strength is greater than zero.
  • “Custom CTDIvol” is displayed when CTDIvol is entered by users..
  • Several bugs related to TCM in the batch module were fixed.
• 20211027
  • Height and weight made uneditable when body size-dependent phantoms selected. The body size is only adjustable using the up and down arrows.
  • Input for pregnant women (phantom group 5) and fetal (phantom group 6) phantoms can be used in batch input
  • Menus for User Manual and User Forum added under “Help” menu
• 20211021
  • mA will be calculated from custom CTDIvol values and TCM can be applied to mA
• 20210915
  • Bug stopping the program when the batch input file is not available fixed
  • mA and rotation time separated from mAs to properly adjust mA in the TCM mode
  • mA limit added to limit too high mA for obese patients under TCM mode
  • TCM mode disabled when a custom CTDIvol entered
• 20210520
  • NCICT automatically selects a phantom best matching the height and weight of a patient in the batch mode
• 20210513 Official release version 3.0.20210513
  • A batch function added (see the template input file: ncict_batch_input.csv)
  • Tube current modulation added based on generic modulation profiles
• 20210307
  • Effective diameter for pregnant women phantoms added
• 20200312 Official release version 3.0.20200312
  • Speed up the scan range dragging on Windows version
• 20191205
  • Mother’s dose added, NCICT 3.0.20191205
  • Presented at RSNA 2019
• 20190301
  • Eight pregnant phantoms with fetus added. Fetal organ dose made available.
  • NCICT3.0 Build 20190301 launched
• 20181118 Official release version 2.0.20181118
  • 98 more adult phantoms were added to the dose library, completing all 351 phantoms
  • NCICTX presented at AAPM 2018, NCICTX renamed to NCICT 2.0.20181118
• 20160401
  • 72 adult phantoms + 181 pediatric phantoms, NCICTX 20160401
  • NCICTX presented at AAPM 2016
• 20151201
  • NCICT1.0 published in Journal of Radiological Protection: Lee et al. JRP 2015
  • NCICT1.0 presented at RSNA 2015
• 20141201 Official release version 1.0.20141201
  • ICRP pediatric and adult phantoms replaced NCI phantoms: NCICT 1.0.20141201
• 20120418
  • MATLAB version translated into Visual Basic 6.0 version of NCICT 1.0.20120418
  • Batch routine implemented to automate multiple calculations
  • Public beta testing started with a non-official data agreement form
• 20110517
  • NCI phantom- and MATLAB-based NCICT 1.0.20110517