The impact of dual energy CT imaging on dose calculations for pre-clinical studies

Abstract

BackgroundTo investigate the feasibility of using dual-energy CT (DECT) for tissue segmentation and kilovolt (kV) dose calculations in pre-clinical studies and assess potential dose calculation accuracy gain.MethodsTwo phantoms and an ex-vivo mouse were scanned in a small animal irradiator with two distinct energies. Tissue segmentation was performed with the single-energy CT (SECT) and DECT methods. A number of different material maps was used. Dose calculations were performed to verify the impact of segmentations on the dose accuracy.ResultsDECT showed better overall results in comparison to SECT. Higher number of DECT segmentation media resulted in smaller dose differences in comparison to the reference. Increasing the number of materials in the SECT method yielded more instability. Both modalities showed a limit to which adding more materials with similar characteristics ceased providing better segmentation results, and resulted in more noise in the material maps and the dose distributions. The effect was aggravated with a decrease in beam energy. For the ex-vivo specimen, the choice of only one high dense bone for the SECT method resulted in large volumes of tissue receiving high doses. For the DECT method, the choice of more than one kind of bone resulted in lower dose values for the different tissues occupying the same volume. For the organs at risk surrounded by bone, the doses were lower when using the SECT method in comparison to DECT, due to the high absorption of the bone. SECT material segmentation may lead to an underestimation of the dose to OAR in the proximity of bone.ConclusionsThe DECT method enabled the selection of a higher number of materials thereby increasing the accuracy in dose calculations. In phantom studies, SECT performed best with three materials and DECT with seven for the phantom case. For irradiations in preclinical studies with kV photon energies, the use of DECT segmentation combined with the choice of a low-density bone is recommended.

A new tissue segmentation method to calculate 3D dose in small animal radiation therapy

“…The stoichiometric calibration was originally designed for a highly collimated fan beam [ 8 ], but it fails when applied to CBCT acquisitions whose divergent broad beam produces more scattered radiation. No gold standard tissue segmentation method exists for CBCT images and various approaches have been explored, such as, recently, dual energy CBCT [ 24 ]. Our method, based on the (HU, ρZ eff ) relationship, showed satisfactory results for dose calculation at 225 kV based on 40kVp CBCT images.…”

On the determination of planning target margins due to motion for mice lung tumours using a four-dimensional MOBY phantom

“…12 Using human tissue density values is common practice in pre-clinical radiotherapy, due to the absence of small animal tissue density information in the literature. 13 As a result of the assignment, each MOBY voxel represents a density value of a specific organ.…”

VOXSI: A voxelized single- and dual-energy CT scenario generator for quantitative imaging

“…Besides conventional SECT imaging, interest in dual-energy CT (DECT) for radiology and radiotherapy is increasing [2] . A growing body of literature suggests that DECT is beneficial for subjective and objective image quality, soft tissue characterization, projection or image based metal artifact reduction, brachytherapy dose calculations, particle therapy dose calculations, and small animal radiotherapy dose calculations [3] , [4] , [5] , [6] , [7] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] .…”