Calculators

Body surface area

DuBois: 0.007184 × height0.725 × weight0.425. Mosteller: √(height × weight / 3600). The reference ranges on this site index to DuBois.

Volumes, ejection fraction, output

Compare indexed values with the age- and sex-matched ranges on the charts page or in the normal values tables.

Regurgitant volume and fraction

MethodRegurgitant volumeAssumes
Ventricular stroke volumesLV SV − RV SVSingle regurgitant valve, no shunt
Stroke volume minus forward flowLV SV − aortic forward flowNo other lesion on the same ventricle
Direct (phase contrast)Aortic reverse flowSemilunar valves only

Fraction = regurgitant volume / stroke volume of the ventricle upstream of the valve. Published CMR thresholds: aortic regurgitant fraction >33% predicts progression to symptoms or surgery (Myerson 2012); mitral regurgitant fraction ≥40% or regurgitant volume ≥55 mL predicts surgery (Myerson 2016).

Qp:Qs

Qp from main pulmonary artery phase contrast, Qs from ascending aorta. ESC 2020 ACHD guideline: shunt closure is indicated for a Qp:Qs >1.5 with right heart volume overload (ASD) or a Qp:Qs >1.5 with LV volume overload (VSD), absent pulmonary vascular disease.

Extracellular volume fraction

ECV = (1 − Hct) × ΔR1myo / ΔR1blood, with R1 = 1/T1. λ is the partition coefficient before the haematocrit correction. Pooled normal ECV by field strength, vendor and sequence is in normal values.

T2* iron

Myocardial T2* at 1.5TGrade
> 20 msNormal
10 to 20 msIron overload
< 10 msSevere iron overload

Grading per Kawel-Boehm 2020 (Table 63). Liver iron concentration from liver T2* uses the Wood 2005 calibration at 1.5T: LIC (mg/g dry weight) = 0.0254 × R2* + 0.202, R2* = 1000 / T2*.

Atrial area index

Maximal area at ventricular end-systole, appendage excluded. Normal range (mean ± 2 SD) from Kawel-Boehm 2020, Tables 15 and 18: LA area/BSA men 12 (7 to 16), women 12 (8 to 15) cm²/m²; RA area/BSA men 11 (7 to 15), women 12 (8 to 15) cm²/m².

eGFR

CKD-EPI 2021 creatinine equation (race-free), reported in mL/min/1.73 m² with the KDIGO G stage. Gadolinium guidance by eGFR is on the safety page.

Gadolinium dose

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  8. Wood JC, Enriquez C, Ghugre N, et al. MRI R2 and R2* mapping accurately estimates hepatic iron concentration in transfusion-dependent thalassemia and sickle cell disease patients. Blood 2005;106(4):1460-1465. doi:10.1182/blood-2004-10-3982
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