КТ калькулятор

Three calculators for a CT specialist: effective dose, contrast washout, GFR

Calculator No. 1

A method for estimating the effective dose during a CT examination based on measurements of the absorbed dose in physical phantoms simulating the patient’s body.

Serves as a measure of the biological risk of radiation exposure during CT examinations and allows direct comparison with the effective dose for other types of x-ray diagnostic examinations. The unit of measurement is mSv.

The effective dose is calculated using the formula:

E = DLP*Edlp, where

DLP (Dose Length Product, product of dose and length) - absorbed dose for the entire CT study in mGy*cm.

Edlp - dose coefficient for the corresponding anatomical region mSv/(mGy*cm).

The calculation is carried out according to MU 2.6.1.3584-19 "Changes to MU 2.6.1.2944-19 "Control of effective radiation doses to patients during medical x-ray examinations"

Calculator No. 2

The calculator is designed to calculate the absolute and relative percentage of contrast agent washout from the adrenal glands during a contrast study. The technique is used to differentiate between malignant and benign lesions.

To interpret the results, the percentage of contrast washout must be calculated. To calculate it, two formulas are used.

Absolute washout percentage: 100 x (venous phase density (HU) - delayed phase density (HU))/(venous phase density (HU) - native phase density (HU))

Relative washout percentage: 100 x (venous phase density (HU) - delayed phase density (HU))/venous phase density (HU)

Calculator No. 3

Glomerular filtration rate (GFR) is the amount of blood cleared by the kidneys over a given period of time. GFR is the main indicator for assessing renal function and the stage of renal failure.

The rate of glomerular filtration is determined by the rate of blood purification (clearance) of certain substances excreted by the kidneys that are not secreted and reabsorbed in the tubules (most often creatinine, inulin, urea).

The CKD-EPI equation is the most accurate formula, last adjusted in 2021

142 * min(Scr/k, 1)α * max(Scr/k, 1)-1.200 * 0.9938Age * 1.012 [for women], where

Scr - plasma creatinine in mg/dl

k = 0.7 (women) or 0.9 (men)

α = -0.241 (women) or -0.302 (men)

min(Scr/κ, 1) - minimum value of Scr/κ or 1.0

max(Scr/κ, 1) - maximum value of Scr/κ or 1.0

age - age in years

To assess kidney function in children, the Schwartz formula is used:

k * height (cm) / plasma creatinine (µmol/l), where

For boys over 13 years old: k = 0.0616

For children under 3 years old: k = 0.0313