<i>In vivo</i> comparison of tantalum, tungsten, and bismuth enteric contrast agents to complement intravenous iodine for double‐contrast dual‐energy CT of the bowel

Rathnayake, Samira; Mongan, John; Torres, Andrew S.; Colborn, Robert E.; Gao, Dongwei; Yeh, Benjamin M.; Fu, Yanjun

doi:10.1002/cmmi.1687

Cited by 39 publications

(31 citation statements)

References 30 publications

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“…In addition, we did not study human subjects, for whom results may vary compared to this relatively small animal model, as the X-ray attenuation of humans will be greater. Finally, we have only studied gold based agents in this report, while agents based on bismuth, tantalum, ytterbium and other elements have been reported as CT contrast agents and for other applications 10,47–51 .…”

Section: Resultsmentioning

confidence: 99%

Evaluation of spectral photon counting computed tomography K-edge imaging for determination of gold nanoparticle biodistribution in vivo

et al. 2017

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Spectral photon counting computed tomography (SPCCT) is an emerging medical imaging technology. SPCCT scanners record the energy of incident photons, which allows specific detection of contrast agents due to measurement of their characteristic x-ray attenuation profiles. This approach is known as K-edge imaging. Nanoparticles formed from elements such as gold, bismuth or ytterbium have been reported as potential contrast agents for SPCCT imaging. Furthermore, gold nanoparticles have many applications in medicine, such as adjuvants for radiotherapy and photothermal ablation. Specific, longitudinal imaging of the biodistribution of nanoparticles would be highly attractive for their clinical translation. We therefore studied the capabilities of a novel SPCCT scanner to quantify the biodistribution of gold nanoparticles in vivo. PEGylated gold nanoparticles were used. Phantom imaging showed that concentrations measured on gold images correlated well with known concentrations (slope = 0.94, intercept = 0.18, RMSE = 0.18, R2 = 0.99). The SPCCT system allowed repetitive and quick acquisitions in vivo, and follow-up of changes in the AuNP biodistribution over time. Measurements performed on gold images correlated with the Inductively coupled plasma-optical emission spectrometry (ICP-OES) measurements in the organs of interest (slope = 0.77, intercept = 0.47, RMSE = 0.72, R2 = 0.93). TEM agreed with the imaging and ICP-OES in that much higher concentrations of AuNP were observed in the liver, spleen, bone marrow and lymph nodes (mainly in macrophages). In conclusion, we found that SPCCT is capable of repetitive and non invasive determination of the biodistribution of gold nanoparticles in vivo.

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Section: Resultsmentioning

confidence: 99%

Evaluation of spectral photon counting computed tomography K-edge imaging for determination of gold nanoparticle biodistribution in vivo

et al. 2017

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“…First, we did not compare the CMEP to conventional MD techniques. However, generation of the tungsten, or indeed any high-Z decomposition images is precluded at RSCT as the commercial software is limited to materials that do not have a k-edge between 40 and 140 keV (15, 17). Furthermore both RSCT and DSCT software are unable to generate three separate material-specific images; both are limited to two materials.…”

Section: Discussionmentioning

confidence: 99%

“…Three contrast-producing materials were included; tungsten, iodine and calcium, details of which are provided in Table 1. Tungsten was chosen for it’s distinct dual-energy ratio compared to calcium and iodine (19) and because it has been identified as a candidate element for contrast agent development (15, 17, 19, 27). Iodine and tungsten were formulated to concentrations of 5, 10, 15 and 20 mg/mL of the active element, while calcium was formulated to 20, 30, 40 and 50% calcium nitrate by weight.…”

Section: Methodsmentioning

confidence: 99%

“…Third, MD is often not compatible with high atomic number (Z) contrast elements currently in development (13–16). This is because these elements have k-absorption edges that lie within the diagnostic energy range (∼ 40 – 140 keV) (15, 17). The k-edge discontinuity is not represented well at DECT, as attenuation data is only captured at two discrete x-ray spectra.…”

Section: Introductionmentioning

confidence: 99%

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An Image-Domain Contrast Material Extraction Method for Dual-Energy Computed Tomography

et al. 2017

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Objectives Conventional material decomposition techniques for dual-energy CT (DECT) assume mass or volume conservation, where the CT number of each voxel is fully assigned to predefined materials. We present an image-domain contrast material extraction process (CMEP) method that preferentially extracts contrast-producing materials while leaving the remaining image intact. Materials and Methods Image processing freeware (Fiji) is used to perform consecutive arithmetic operations on a dual-energy ratio map to generate masks, which are then applied to the original images to generate material-specific images. First, a low-energy image is divided by a high-energy image to generate a ratio map. The ratio map is then split into material-specific masks. Ratio intervals known to correspond to particular materials (e.g. iodine, calcium) are assigned a multiplier of 1, while ratio values in between these intervals are assigned linear gradients from 0 to 1. The masks are then multiplied by an original CT image to produce material-specific images. The method was tested quantitatively at Dual-Source (DSCT) and Rapid kVp-Switching CT (RSCT) with phantoms using pure and mixed formulations of tungsten, calcium and iodine. Errors were evaluated by comparing the known material concentrations with those derived from the CMEP material-specific images. Further qualitative evaluation was performed in vivo at RSCT with a rabbit model using identical CMEP parameters to the phantom. Orally administered tungsten, vascularly administered iodine, and skeletal calcium were used as the three contrast materials. Results All five material combinations; tungsten, iodine and calcium, and mixtures of tungsten-calcium and iodine-calcium, showed distinct dual-energy ratios, largely independent of material concentration at both DSCT and RSCT. The CMEP was successful in both phantoms and in vivo. For pure contrast materials in the phantom, the maximum error between the known and CMEP-derived material concentrations was 0.9 mg/mL, 24.9 mg/mL and 0.4 mg/mL for iodine, calcium and tungsten respectively. Mixtures of iodine and calcium showed the highest discrepancies, which reflected the sensitivity of iodine to the image-type chosen for the extraction of the final material-specific image. The rabbit model was able to clearly show the three extracted material phases, vascular iodine, oral tungsten and skeletal calcium. Some skeletal calcium was misassigned to the extracted iodine image, however this did not impede the depiction of the vasculature. Conclusions The CMEP is a straightforward, image domain approach to extract material signal at dual-energy CT. It has particular value for separation of experimental high-Z contrast elements from conventional iodine contrast or calcium, even when the exact attenuation coefficient profiles of desired contrast materials may be unknown. The CMEP is readily implemented in the image-domain within freeware, and can be adapted for use with images from multiple vendors.

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“…This increases the attenuation in the high-kVp image, and when combined with the other photon interactions, results in a similar CT numbers at low- and high-kVp images[42]. The relative difference in low- to high-kVp CT number ratios allow for the contribution of two different materials to be determined at DECT material decomposition post-processing[19, 43]. …”

Section: Ct Technologymentioning

confidence: 99%

Opportunities for new CT contrast agents to maximize the diagnostic potential of emerging spectral CT technologies

Yeh

Fitzgerald

Edic

et al. 2017

Advanced Drug Delivery Reviews

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The introduction of spectral CT imaging in the form of fast clinical dual-energy CT enabled contrast material to be differentiated from other radiodense materials, improved lesion detection in contrast-enhanced scans, and changed the way that existing iodine and barium contrast materials are used in clinical practice. More profoundly, spectral CT can differentiate between individual contrast materials that have different reporter elements such that high-resolution CT imaging of multiple contrast agents can be obtained in a single pass of the CT scanner. These spectral CT capabilities would be even more impactful with the development of contrast materials designed to complement the existing clinical iodine- and barium-based agents. New biocompatible high-atomic number contrast materials with different biodistribution and X-ray attenuation properties than existing agents will expand the diagnostic power of spectral CT imaging without penalties in radiation dose or scan time.

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In vivo comparison of tantalum, tungsten, and bismuth enteric contrast agents to complement intravenous iodine for double‐contrast dual‐energy CT of the bowel

Cited by 39 publications

References 30 publications

Evaluation of spectral photon counting computed tomography K-edge imaging for determination of gold nanoparticle biodistribution in vivo

Evaluation of spectral photon counting computed tomography K-edge imaging for determination of gold nanoparticle biodistribution in vivo

An Image-Domain Contrast Material Extraction Method for Dual-Energy Computed Tomography

Opportunities for new CT contrast agents to maximize the diagnostic potential of emerging spectral CT technologies

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