The Complete Radiation Dose Calculator

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The Complete Radiation Dose Calculator

Every modality. Every patient. Every number cited. Effective, organ, fetal and skin dose for Nuclear Medicine, X-Ray, Fluoroscopy and CT.

Reference Patient Sex Doses are for standard reference patients of these ages, not a specific child.

Stage of Pregnancy

Radiopharmaceutical

Activity Administered

Number of Administrations

Estimate From

Exam Type

Body Region Scanned

kVp

DLP (mGy·cm)

Number of Scans

Effective dose = DLP × k. Single regions use Deak et al. 2010, Table 5 (ICRP 103). Combined regions use AAPM Report 96, Table 3 (ICRP 60).

For abdomen and pelvis CT scans only.

CTDIvol (mGy)

Tube Current Modulation

Patient Size

Water Equivalent Diameter (cm)

Shown on many dose reports next to SSDE.

Fetal Depth, optional (cm)

On the axial image, from the front skin surface to the front edge of the fetus.

Hardy et al., Med Phys 2019: CTDIvol to fetal dose coefficients from 24 pregnant patient models, gestational age under 5 to 36 weeks. With modulation: Table V (or Table VIII with fetal depth). Fixed mA: Table VII average of four scanners (or Table VIII with fetal depth).

Choose two to four exams, then press Compare. Typical published adult values; Nuclear Medicine uses the activity you enter.

Scan Region

CTDIvol (mGy)

CTDIvol Phantom

Listed next to CTDIvol on the dose report. Children’s body scans are often reported with the 16 cm phantom.

Patient Size From

Water Equivalent Diameter (cm)

Shown on many dose reports and in the RDSR. It describes the patient’s size as an equivalent amount of water.

AAPM Report 204 conversion factors (Tables 1D and 2D for size; 1B, 1C, 2B, 2C for a single dimension). Water equivalent diameter is used directly in these tables (AAPM Report 220, Appendix).

How to Enter the Procedure

All K_a,r is treated as one skin site with one geometry. Jones and Pasciak recommend this for modest C-arm rotation.

Dose Report

Reference Air Kerma, K_a,r

mGy

Also called cumulative air kerma or reference point dose.

Geometry

Projection

Angled (oblique) runs: how to enter them

Mild angles: keep them with the PA runs on the same skin site. Jones and Pasciak recommend one skin site for modest C-arm rotation.
Clearly separate angles: enter them as their own part (Multiple Parts). Choose a new skin site only if the fields clearly do not overlap; if unsure, assume they overlap (NCRP Report 168).
Source to skin: measure along the angled beam to where it enters the skin.
Table and pad: keep the transmission factor if the beam passes through the table; use 1 if it misses the table.

Jones and Pasciak, JACMP 2011; Jones, Ensor and Pasciak, Med Phys 2014; NCRP Report 168.

Reference Point

21 CFR 1020.32: for C-arms, 15 cm from isocenter toward the tube, unless the manufacturer specifies another point (see the operator manual).

Source to Isocenter

Source to Skin

Where to get the source to skin distance

Tube under the table: the skin rests on the pad, so use the source to tabletop distance (the table height). Get it from the dose report or RDSR, the DICOM “Distance Source to Patient” tag (vendor dependent; on the Siemens units in Jones et al. 2014 it was table height plus a 15 cm default and had to be corrected), or have the technologist measure it once a set K_a,r is reached (Jones and Pasciak 2012; NCRP Report 168).

For angled runs, measure along the beam to where it enters the skin.

Much of this procedure was at steep angles (over 60°) or cone beam CT

Backscatter, f Factor and Table

What the Jones 2014 defaults are

Backscatter factor For embolization on modern C-arms, backscatter varies within a narrow range, about 1.3 to 1.5, so one value is reasonable.	1.4
f factor (tissue to air) One value for all procedures.	1.06

How accurate: across 41 procedures checked against film, the simplified method with a single backscatter factor averaged 12.6% from measured peak skin dose; the full method averaged 11.8%.

When to choose another option: if you know the beam quality and DAP, use From Beam Quality; if you have measured values for your system, use Enter My Own.

Jones, Ensor and Pasciak, Med Phys 2014 (Table I and Discussion).

Table and Pad Transmission

Default 0.80 (Jones et al. 2014). NCRP Report 168 gives typical attenuation of 1.2 to 1.4 (about 0.71 to 0.83). Use 1 if the system’s K_a,r calibration already includes the table and pad; measure it at acceptance testing.

Method: Jones and Pasciak, JACMP 2011 (Part I, with 2014 erratum) and 2012 (Part II); defaults and accuracy from Jones, Ensor and Pasciak, Med Phys 2014.

I Want to Find

DAP / KAP

Field Size Measured At

Field Width (cm)

Field Height (cm)

Source to Image Distance, SID (cm)

Source to Reference Point Distance (cm)

Collimated field size, not the nominal detector field of view. Using the full field of view when the beam was collimated underestimates K_a,r (Jones and Pasciak 2011).

DAP is the same at every distance from the tube; air kerma falls with the square of distance while the field area grows with it. K_a,r = DAP ÷ field area at the reference point (Jones and Pasciak 2011, Eq. 1–2 with 2014 erratum).

Added

About These Estimates and Sources

These are reference phantom, population average estimates, not patient specific doses. Effective dose is a radiation protection quantity for comparing exposures, not for predicting an individual’s risk, and it is not meaningful for radionuclide therapy. Embryo/fetal doses carry large uncertainties.

Nuclear Medicine

Stabin MG, Siegel JA. RADAR dose estimate report: a compendium of radiopharmaceutical dose estimates based on OLINDA/EXM version 2.0. J Nucl Med 2018;59:154–160 (electronic compendium, April 23, 2018).
Stabin MG. New-generation fetal dose estimates for radiopharmaceuticals. J Nucl Med 2018;59:1005–1006, Supplemental Table 1.
U.S. FDA prescribing information (DailyMed), Radiation Dosimetry sections: Amyvid, Axumin, Cerianna, Detectnet, Illuccix, Lutathera, Lymphoseek, Netspot, Neuraceq, Pluvicto, Posluma, Pylarify, Tauvid, Vizamyl, Xofigo.

X-Ray, Fluoroscopy and CT – Effective Dose

Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic Nuclear Medicine: a catalog. Radiology 2008;248:254–263.
Wall BF, Haylock R, Jansen JTM, et al. Radiation risks from medical X-Ray examinations as a function of the age and sex of the patient. HPA-CRCE-028. Health Protection Agency; 2011.
Mahesh M, Ansari AJ, Mettler FA Jr. Patient exposure from radiologic and Nuclear Medicine procedures in the United States and worldwide: 2009–2018. Radiology 2023;307(1):e221263.
Deak PD, Smal Y, Kalender WA. Multisection CT protocols: sex- and age-specific conversion factors used to determine effective dose from dose-length product. Radiology 2010;257:158–166.
AAPM Report No. 96. The measurement, reporting, and management of radiation dose in CT. 2008.

Embryo/Fetal Dose – X-Ray and CT

McCollough CH, Schueler BA, Atwell TD, et al. Radiation exposure and pregnancy: when should we be concerned? RadioGraphics 2007;27:909–918.
HPA, RCR, SCoR. Protection of pregnant patients during diagnostic medical exposures to ionising radiation. 2009.
Hardy AJ, Angel E, Bostani M, Cagnon C, McNitt-Gray M. Estimating fetal dose from tube current-modulated (TCM) and fixed tube current (FTC) abdominal/pelvis CT examinations. Med Phys 2019;46:2729–2743.
AAPM Report No. 204. Size-specific dose estimates (SSDE) in pediatric and adult body CT examinations. 2011.
Damilakis J, Tzedakis A, Perisinakis K, Papadakis AE. A method of estimating conceptus doses resulting from multidetector CT examinations during all stages of gestation. Med Phys 2010;37:6411–6420.

CT Size Specific Dose Estimate

AAPM Report No. 220. Use of water equivalent diameter for calculating patient size and size-specific dose estimates (SSDE) in CT. 2014.
AAPM Report No. 293. Size-specific dose estimate (SSDE) for head CT. 2019.
AAPM Report No. 246. Estimating patient organ dose with computed tomography: a review of present methodology and required DICOM information. 2019.

Fluoroscopy

Jones AK, Pasciak AS. Calculating the peak skin dose resulting from fluoroscopically guided interventions. Part I: Methods. J Appl Clin Med Phys 2011;12(4):231–244; Erratum J Appl Clin Med Phys 2014;15(4):402.
Jones AK, Pasciak AS. Calculating the peak skin dose resulting from fluoroscopically guided interventions. Part II: Case studies. J Appl Clin Med Phys 2012;13(1):174–186.
Jones AK, Ensor JE, Pasciak AS. How accurately can the peak skin dose in fluoroscopy be determined using indirect dose metrics? Med Phys 2014;41(7):071913.
International Atomic Energy Agency. Dosimetry in diagnostic radiology: an international code of practice. Technical Reports Series No. 457. Vienna: IAEA; 2007 (Appendix VIII).
National Council on Radiation Protection and Measurements. NCRP Report No. 168: Radiation dose management for fluoroscopically-guided interventional medical procedures. 2010.
U.S. Code of Federal Regulations, 21 CFR 1020.32, Fluoroscopic equipment (current as of October 2026).

Each result row is labeled with its effective dose basis. Most values use ICRP Publication 103 tissue weighting factors; Mettler et al. 2008 values and AAPM Report 96 combined region CT values use ICRP Publication 60. The two differ modestly for most exams, so totals that combine them are approximate.

Interpretation

American College of Obstetricians and Gynecologists. Committee Opinion No. 723: Guidelines for diagnostic imaging during pregnancy and lactation. Obstet Gynecol 2017;130:e210–e216 (reaffirmed 2026).
National Council on Radiation Protection and Measurements. NCRP Report No. 160: Ionizing radiation exposure of the population of the United States. 2009.

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Version 2 · October 18, 2026