# Volume doubling time (VDT) calculator

> Calculate the volume doubling time of a nodule between two exams, by volumetry or by mean diameter, with the NELSON and BTS 2015 reference ranges.

_Category: · VDT · pulmonary nodule · publicado em 2026-11-10_

Canonical URL: https://www.laudos.ai/en/calculadoras/tempo-de-duplicacao-de-volume

## Page summary

- **What this page explains:** Calculate the volume doubling time of a nodule between two exams, by volumetry or by mean diameter, with the NELSON and BTS 2015 reference ranges.
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## 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](https://radcommons.laudos.ai/systems/fleischner-2017 "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.

## Continue here

-   [Adrenal washout](https://www.laudos.ai/en/calculadoras/washout-adrenal "Adrenal washout")
-   [Ellipsoid volume](https://www.laudos.ai/en/calculadoras/volume-elipsoide "Ellipsoid volume")
-   [PSA density](https://www.laudos.ai/en/calculadoras/densidade-de-psa "PSA density")
-   [Lung-RADS](https://www.laudos.ai/classificacoes/lung-rads "Lung-RADS")
-   [Pulmonary nodule](https://www.laudos.ai/glossario/nodulo-pulmonar "Pulmonary nodule")
-   [Chest CT report](https://www.laudos.ai/laudo/tc-torax "Chest CT report")

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