3D DIMENSIONAL TUMOUR VOLUME CALCULATION
The importance of capturing tumour height in in-vivo efficacy studies
TUMOUR WIDTH AS A PROXY FOR HEIGHT
In the current practices for the measurement of tumour volume a number of assumptions are made to account for the limitations of a callipers.
The first of these is that the tumour is spheroidal in shape and that the height of the tumour is equal to its width.
Volume is calculated using a variation of a spheroidal equation π/6 * L * W * W
However on investigation of 7,286 BioVolume 3D scans
(Fig 1.0) average tumour height is shown to be significantly lower that it's width.
Fig1.0 | BioVolume scan height and width alignment by size (mm) | n = 7,286
HEIGHT MEASUREMENTS IMPACT ON VOLUME
In the below example (Fig2.0) 3 tumour models all have exactly the same length and width but their height varies.
Fig 2.0 | Example tumour models with consistent width and varying heights
Using a spheroidal equation the volume of these tumours will be the same for all 3, and lead to measurement error in excess of 700% (Fig. 3.0) where the height is furthest away from the width.
Fig 3.0 | Tumour volume error for spheroidal (LxWxW) and ellipsoid BioVolume (LxWxH) measurements of example tumour models
A COMPARISION OF BIOVOLUME (LxWxH) AND CALLIPER (LxWxW) TO MRi
In order to test the hypothesis outlined above a small comparative study was conducted with a UK based pharmaceutical company to assertain the volume accuracy of callipers and BioVolume against those obtained via MRi imaging.
BioVolume and calliper measurements were taken at 11 points across a study consisting of 18 animals with and 3 different tumour strains. 3 MRi sessions were conducted at small, medium and large growth stages.
As illustrated in Fig4.0 and through further in depth analysis BioVolume (LxWxH) shows no statistically significant difference from the MRi measurements, with Calliper (LxWXW) measurements statistically different.
Fig 4.0 | Comparative tumour growth for MRI / BioVolume & Calliper measurement
Also of note is a drop in tumour volume with callipers on the first date in February date, when the imaging (Fig 5.0) from the BioVolume measurement is reviewed we can see that this is not the case.
Fig 5.0 | Comparative tumour growth for MRI / BioVolume & Calliper measurement with BioVolume image and segmentation trace log.