Comparison of Multimodality Image-Based Volumes in Preclinical Tumor Models Using <i>In-Air</i> Micro-CT Image Volume as Reference Tumor Volume

Abstract

Purpose: Changes in tumor volume are used for therapy response monitoring in preclinical studies. Unlike prior studies, this article introduces in-air micro-computed tomography (micro-CT) image volume as reference tumor volume in rodent tumor models. Tumor volumes determined using imaging modalities such as magnetic resonance imaging (MRI), micro-CT and ultrasound (US), and with an external caliper are compared with the reference tumor volume. Materials and Methods: In vivo MR, US and micro-CT imaging was performed 4, 6, 9, 11 and 13 days after tumor cell inoculation into nude rats. On the day of the imaging study, in vivo caliper measurements were also made. After in vivo imaging, tumors were excised followed by in-air micro-CT imaging and ex vivo caliper measurements of excised tumors. The in-air micro-CT image volume of excised tumors was determined as reference tumor volume. Then tumor volumes were calculated using formula V = (π/6) × a × b × c, where a, b and c are maximum diameters in three perpendicular dimensions determined by the three image modalities and caliper, and compared with reference tumor volume by linear regression analysis as well as Bland-Altman plots. Results: The correlation coefficients (R 2) of the regression lines for in vivo tumor volumes measured by the three imaging modalities were 0.9939, 0.9669 and 0.9806 for MRI, US and micro-CT respectively. For caliper measurements, the coefficients were 0.9274 and 0.9819 for caliper in vivo and caliper ex vivo respectively. In Bland-Altman plots, the average of tumor volume difference from reference tumor volume (bias) was significant for caliper and micro-CT, but not for MRI and US. Conclusion: Using the in-air micro-CT image volume as reference tumor volume, tumor volume measured by MRI was the most accurate among the three imaging modalities. In vivo caliper volume measurements showed unreliability while ex vivo caliper measurements reduced errors.

Low-Cost Robotic Manipulation of Live Microtissues for Cancer Drug Testing

“…Since 𝐴 ≈ ℎ 2 and 𝑉 𝑐 ≈ ℎ 3 , then 𝑑 𝑚𝑎𝑥 ~ 𝑄 1 3 ⁄ ℎ 1 6 ⁄ . Substituting our typical values (𝑄 = 56 µL/s, 𝜌 𝑐 = 1.079 g/cm 3 for mouse tumors 64 ), we predict that the maximum distance between the capillary and the bottom of a cuboid that allows for lifting the cuboid is 𝑑 𝑚𝑎𝑥 ≈ 1.2 mm for a 400 µm cuboid and 𝑑 𝑚𝑎𝑥 ≈ 1.1 mm for a 250 µm cuboid.…”

Monitoring the Growth of an Orthotopic Tumour Xenograft Model: Multi-Modal Imaging Assessment with Benchtop MRI (1T), High-Field MRI (9.4T), Ultrasound and Bioluminescence

“…To measure a 10% change the high-field MRI, low-field MRI and ultrasound imaging will respectively require 4, 20 and 33 animals, using the intra-user CVs, a power of 80% and 5% type I error and assuming no significant contrast changes. Furthermore, studies that have measured on the variability of calliper estimations of tumour volume report CVs between 12–35%, and generally more varied than imaging such MRI, US and CT [ 5 ; 22 ; 35 ; 47 ]. Thus calliper measurements, would mostly yield even larger required groups from power calculations than imaging.…”

“…The accessibility of each small animal imaging platform will vary between institutions and research groups, and deciding which systems to use can be complex, and has led to a few studies comparing the application of different systems [ 7 ; 18 ]. However, only a limited number of studies have directly compared small-animal MRI and US imaging systems in assessing tumour volumes, though there are some alternative applications and clinical reports available [ 19 – 22 ]. A key advantage of non-invasive imaging is its ability to monitor individual animals longitudinally [ 23 ; 24 ].…”