Ellipsoid volume is axis 1 × axis 2 × axis 3 × π/6, that is, the product of the three orthogonal axes multiplied by about 0.523. With the axes in centimeters the result is in cm³; in millimeters, in mm³.
Calculation support for physicians. The result does not replace the assessment of the exam or the decision of whoever signs the report. Page published on .
Formula
Volume = axis 1 × axis 2 × axis 3 × π/6
π/6 ≈ 0.523
What to look for
Geometric estimate from the three orthogonal axes. Use the same measurements as in the report.
Questions and answers
What is the ellipsoid volume formula?
Volume = axis 1 × axis 2 × axis 3 × π/6. The three axes are orthogonal to each other and in the same unit.
Where does 0.523 come from?
It is π divided by 6, about 0.5236. The volume of an ellipsoid is 4/3 × π × the three semi-axes; written with the full axes, this gives π/6 × axis 1 × axis 2 × axis 3.
Can I enter the axes in millimeters?
Yes. With the axes in millimeters the volume is in mm³; with the axes in centimeters, in cm³. 1 cm³ equals 1,000 mm³ and 1 mL.
Is ellipsoid volume an exact measurement?
No. It is a geometric estimate from the three orthogonal axes, and the calculation should use the same measurements that go into the report.
Valid with a 15-minute delayed phase and an ROI covering about half to two-thirds of the lesion, without necrosis or hemorrhage.A lesion stable for at least 1 year does not require further imaging. Hormonal evaluation should be considered in most incidentalomas.Hypervascular metastasis (such as renal cell or hepatocellular carcinoma) and pheochromocytoma can have high washout; interpret with the clinical picture.Indeterminate: follow the ACR flowchart according to size, oncologic history and prior exam. Chemical-shift MRI, comparison with prior imaging, PET/CT or biopsy can clarify.Lesion ≥ 4 cm: the ACR White Paper considers resection when it is not a lipid-rich adenoma or another characteristic benign lesion.Adrenal nodule measuring {0} cm,Lipid-rich adenoma (≤ 10 HU unenhanced). Washout is not needed.{0} with unenhanced attenuation of {1} HU.Enter the attenuation in the portal venous phase and in the 15-minute delayed phase.The attenuation in the portal venous phase must be greater than zero.The attenuation in the portal venous phase must be greater than the unenhanced attenuation.Absolute washout of {0}% (≥ 60%): consistent with adenoma.Absolute washout of {0}% (< 60%): indeterminate.Relative washout of {0}% (≥ 40%): consistent with adenoma.Relative washout of {0}% (< 40%): indeterminate.{0} with unenhanced attenuation of {1} HU, {2} HU in the portal venous phase, {3} HU in the delayed phase (15 min), absolute washout of {4}% and relative washout of {5}%.{0} with {1} HU in the portal venous phase, {2} HU in the delayed phase (15 min), relative washout of {3}%.Geometric estimate from the three orthogonal axes. Use the same measurements as in the report.Enter the three axes, greater than zero.{0} x {1} x {2} {3}, volume of {4}PI-RADS v2.1 does not define a PSAD cutoff and the density is not part of the PI-RADS category.Ellipsoid volume: anteroposterior x transverse x craniocaudal x π/6 (≈ 0.52).Enter the PSA in ng/mL.Enter the prostate volume or the three axes in centimeters.Prostate measuring {0} x {1} x {2} cm, estimated volume of {3} cm³. PSA density of {4} ng/mL/cm³ (PSA {5} ng/mL).Prostate volume of {0} cm³. PSA density of {1} ng/mL/cm³ (PSA {2} ng/mL).Enter the interval between the two exams, in days.Enter the two volumes in mm³ or the two mean diameters in mm.Volumes estimated as a sphere from the mean diameter; segmented volumetry is more reliable.Use the same technique and the same software for both measurements.Mean nodule diameter from {0} to {1} mm in {2} days (estimated volume from {3} to {4} mm³, {5}).Nodule volume from {0} to {1} mm³ in {2} days ({3}).No change in volume: VDT does not apply.Volume reduction: VDT does not apply.VDT of {0} days (< 400): rapid growth, suspicious range.VDT of {0} days (400 to 600): indeterminate range.VDT of {0} days (> 600): slow growth.{0} daysResultCopied