Dosimetry in Micro-computed Tomography: a Review of the Measurement Methods, Impacts, and Characterization of the Quantum GX Imaging System

Abstract

PurposeX-ray micro-computed tomography (μCT) is a widely used imaging modality in preclinical research with applications in many areas including orthopedics, pulmonology, oncology, cardiology, and infectious disease. X-rays are a form of ionizing radiation and, therefore, can potentially induce damage and cause detrimental effects. Previous reviews have touched on these effects but have not comprehensively covered the possible implications on study results. Furthermore, interpreting data across these studies is difficult because there is no widely accepted dose characterization methodology for preclinical μCT. The purpose of this paper is to ensure in vivo μCT studies can be properly designed and the data can be appropriately interpreted.ProceduresStudies from the scientific literature that investigate the biological effects of radiation doses relevant to μCT were reviewed. The different dose measurement methodologies used in the peer-reviewed literature were also reviewed. The CT dose index 100 (CTDI100) was then measured on the Quantum GX μCT instrument. A low contrast phantom, a hydroxyapatite phantom, and a mouse were also imaged to provide examples of how the dose can affect image quality.ResultsData in the scientific literature indicate that scenarios exist where radiation doses used in μCT imaging are high enough to potentially bias experimental results. The significance of this effect may relate to the study outcome and tissue being imaged. CTDI100 is a reasonable metric to use for dose characterization in μCT. Dose rates in the Quantum GX vary based on the amount of material in the beam path and are a function of X-ray tube voltage. The CTDI100 in air for a Quantum GX can be as low as 5.1 mGy for a 50 kVp scan and 9.9 mGy for a 90 kVp scan. This dose is low enough to visualize bone both in a mouse image and in a hydroxyapatite phantom, but applications requiring higher resolution in a mouse or less noise in a low-contrast phantom benefit from longer scan times with increased dose.ConclusionsDose management should be considered when designing μCT studies. Dose rates in the Quantum GX are compatible with longitudinal μCT imaging.

Photon-counting cine-cardiac CT in the mouse

“…The absorbed radiation dose associated with imaging was ∼190 mGy (vs. ∼170 mGy for our 4D EID-CT imaging protocols [19]). These doses are comparable to many commercial micro-CT scanners when reconstructing 10 cardiac phases [20], and are consistent with our previous results showing dose benefits associated with four-threshold, PCD-based spectral imaging over DE EID-CT [21]. Notably, additional PCD dose optimizations (e.g.…”

In-vivo lung fibrosis staging in a bleomycin-mouse model: a new micro-CT guided densitometric approach

“…Images were acquired with a respiratory gated technique with the following parameters: X-ray tube voltage 90 KV, X-ray tube current 88 µA, total scan time of 4 min. A ring reduction correction was applied to the sinograms and the entire set of projection radiographs was input into a GPU-based filtered back-projection algorithm with a Ram-Lak filter 36 . The retrospectively gated acquisition protocol in ‘high speed’ mode (acquiring projections without averaging in list-mode over a total angle of 360°), resulted in two 3D datasets with 50 μm isotropic reconstructed voxel size, corresponding to the two different phases of the breathing cycle (i.e.…”

A Multimodal Imaging Approach Based on Micro-CT and Fluorescence Molecular Tomography for Longitudinal Assessment of Bleomycin-Induced Lung Fibrosis in Mice

“…CAUTION: Before starting, always remove any metal jewelry or metal objects near the imaging area, to avoid scattering of x-rays. NOTE: Radiation-induced lung fibrosis is a common finding during radiation induced lung injury 24 . Neither Micro-CT derived indices nor histological findings associated with lung fibrosis were present in saline treated control mice on day 21 subjected to four Micro-CT imaging sessions, indicating that the X-ray dose delivered to the animals during Micro-CT examinations was not sufficient to affect the findings.…”