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

Yeh, Benjamin M.; Fitzgerald, Peter; Edic, Peter M.; Lambert, Jack W.; Colborn, Robert E.; Marino, Michael; Evans, Paul M.; Roberts, Jeannette C.; Wang, Zhen J.; Wong, Margaret J.; Bonitatibus, Peter J.

doi:10.1016/j.addr.2016.09.001

Cited by 149 publications

(142 citation statements)

References 202 publications

(205 reference statements)

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“…Unfortunately, clinically approved iodine-based contrast agents have a relatively low K-edge (33.17 keV), which is unfeasible for K-edge imaging in clinical routine because of absorption of low energy photons below the K-edge. Therefore, the development and further promotion of new contrast agents, which are partially on the product roadmap [32], is of particular interest to fully exploit the benefits of SPCCT imaging.…”

Section: Discussionmentioning

confidence: 99%

Experimental feasibility of spectral photon-counting computed tomography with two contrast agents for the detection of endoleaks following endovascular aortic repair

et al. 2018

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ObjectivesAfter endovascular aortic repair (EVAR), discrimination of endoleaks and intra-aneurysmatic calcifications within the aneurysm often requires multiphase computed tomography (CT). Spectral photon-counting CT (SPCCT) in combination with a two-contrast agent injection protocol may provide reliable detection of endoleaks with a single CT acquisition.MethodsTo evaluate the feasibility of SPCCT, the stent-lined compartment of an abdominal aortic aneurysm phantom was filled with a mixture of iodine and gadolinium mimicking enhanced blood. To represent endoleaks of different flow rates, the adjacent compartments contained either one of the contrast agents or calcium chloride to mimic intra-aneurysmatic calcifications. After data acquisition with a SPCCT prototype scanner with multi-energy bins, material decomposition was performed to generate iodine, gadolinium and calcium maps.ResultsIn a conventional CT slice, Hounsfield units (HU) of the compartments were similar ranging from 147 to 168 HU. Material-specific maps differentiate the distributions within the compartments filled with iodine, gadolinium or calcium.ConclusionSPCCT may replace multiphase CT to detect endoleaks without sacrificing diagnostic accuracy. It is a unique feature of our method to capture endoleak dynamics and allow reliable distinction from intra-aneurysmatic calcifications in a single scan, thereby enabling a significant reduction of radiation exposure.Key Points• SPCCT might enable advanced endoleak detection.• Material maps derived from SPCCT can differentiate iodine, gadolinium and calcium.• SPCCT may potentially reduce radiation burden for EVAR patients under post-interventional surveillance.

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Section: Discussionmentioning

confidence: 99%

Experimental feasibility of spectral photon-counting computed tomography with two contrast agents for the detection of endoleaks following endovascular aortic repair

et al. 2018

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“…Second, the assumption of volume conservation results in the unphysical presence of negative concentrations of materials, notably iodine when using commercially available two-MD (5). 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).…”

Section: Introductionmentioning

confidence: 99%

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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“…However, due to its low solubility in water and the potential of salicylate toxicity, bismuth subsalicylate is of limited use as a contrast agent for imaging in human subjects . Our study demonstrates the potential of spectral CT for multicontrast differentiation and we hope this will intensify the ongoing research and development of new CT contrast agents . The threshold settings, reconstruction kernels and material decomposition method used in this study remain novel and thus are likely not necessarily optimal.…”

Section: Discussionmentioning

confidence: 90%

“…As a result, rather than use high‐attenuation contrast agents for the bowel, water or air is more frequently used with current generation CT in order to separate vascular from nonvascular bowel. It appears possible that photon‐counting CT may encourage development of alternative and potentially more specific or sophisticated CT contrast agents . In addition, multicontrast imaging with photon CT has the advantage of perfect coregistration of all material maps.…”

Section: Discussionmentioning

confidence: 99%

Photon‐counting CT for simultaneous imaging of multiple contrast agents in the abdomen: An in vivo study

et al. 2017

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Purpose To demonstrate the feasibility of spectral imaging using photon-counting detector (PCD) x-ray computed tomography (CT) for simultaneous material decomposition of 3 contrast agents in vivo in a large animal model. Methods This Institutional Animal Care and Use Committee-approved study used a canine model. Bismuth subsalicylate was administered orally 24–72 hours before imaging. PCD CT was performed during intravenous administration of 40–60 ml gadoterate meglumine; 3.5 minutes later, iopamidol 370 was injected intravenously. Renal PCD CT images were acquired every 2 seconds for 5–6 minutes to capture the wash-in and wash-out kinetics of the contrast agents. Least mean squares linear material decomposition was used to calculate the concentrations of contrast agents in the aorta, renal cortex, renal medulla and renal pelvis. Results Using reference vials with known concentrations of materials, we computed molar concentrations of the various contrast agents during each phase of CT scanning. Material concentration maps allowed simultaneous quantification of both arterial and delayed renal enhancement in a single CT acquisition. The accuracy of the material decomposition algorithm in a test phantom was −0.4±2.2 mM, 0.3±2.2 mM for iodine and gadolinium solutions, respectively. Peak contrast concentration of gadolinium and iodine in the aorta, renal cortex, and renal medulla were observed 16, 24, and 60 seconds after the start each injection, respectively. Conclusion Photon-counting spectral CT allowed simultaneous material decomposition of multiple contrast agents in vivo. Besides defining contrast agent concentrations, tissue enhancement at multiple phases was observed in a single CT acquisition, potentially obviating the need for multi-phase CT scans and thus reducing radiation dose.

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

Cited by 149 publications

References 202 publications

Experimental feasibility of spectral photon-counting computed tomography with two contrast agents for the detection of endoleaks following endovascular aortic repair

Experimental feasibility of spectral photon-counting computed tomography with two contrast agents for the detection of endoleaks following endovascular aortic repair

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

Photon‐counting CT for simultaneous imaging of multiple contrast agents in the abdomen: An in vivo study

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