Volume doubling time is the interval between the exams, in days, multiplied by ln 2 and divided by ln(V2 ÷ V1). In the reference ranges, a VDT below 400 days is rapid growth (positive in NELSON), 400 to 600 is indeterminate, and BTS 2015 only discharges with a VDT above 600 days by volumetry.
Example
VDT
154 days
Volume change
+50%
VDT of 154 days (< 400): rapid growth, suspicious range.
Report lineNodule volume from 120 to 180 mm³ in 90 days (+50%). VDT of 154 days (< 400): rapid growth, suspicious range.
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
VDT = interval (days) × ln 2 ÷ ln(V2 ÷ V1)
By mean diameter: V = π/6 × d³ (sphere)
Thresholds
VDT
Range
Reference
< 400 days
Rapid growth, suspicious range
NELSON: positive
400 to 600 days
Indeterminate
NELSON: indeterminate
> 600 days
Slow growth
BTS 2015: discharge only with VDT > 600 days by volumetry
What to look for
Use the same technique and the same software for both measurements.
Volumes estimated as a sphere from the mean diameter; segmented volumetry is more reliable.
Source
VDT = interval x ln 2 / ln(V2/V1) (Schwartz, 1961). Reference ranges: NELSON (VDT < 400 days positive; 400 to 600, indeterminate) and BTS 2015 (discharge only with VDT > 600 days by volumetry).
The same logic runs in the public tool of RadCommons, the Laudos.AI classification corpus.
Questions and answers
How is volume doubling time calculated?
VDT = interval between the exams, in days, × ln 2 ÷ ln(V2 ÷ V1), where V1 is the prior volume and V2 the current one. A nodule that went from 120 to 180 mm³ in 90 days has a VDT of 154 days.
What doubling time is considered suspicious?
In the reference ranges, a VDT below 400 days is rapid growth (positive in the NELSON trial) and 400 to 600 days is indeterminate. BTS 2015 only discharges with a VDT above 600 days by volumetry.
Can I calculate VDT from the diameter?
Yes, by estimating each volume as a sphere from the mean diameter (π/6 × d³). Segmented volumetry is more reliable, and both measurements should use the same technique and the same software.
What if the nodule shrank or did not change?
With a reduction in volume, or with no change, the doubling time does not apply.
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