High Atomic Number Contrast Media Offer Potential for Radiation Dose Reduction in Contrast-Enhanced Computed Tomography

Roessler, Ann-Christin; Hupfer, Martin; Kolditz, Daniel; Jošt, Gregor; Pietsch, Hubertus; Kalender, Willi A.

doi:10.1097/rli.0000000000000232

Cited by 32 publications

(19 citation statements)

References 9 publications

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“…Our measured results, which are determined using large physical phantoms, corroborate results of prior studies which used physical phantoms to image hafnium and tungsten,(18) and indirectly simulated large patient diameter with either computer simulations,(9) or through filtration of the x-ray source. (10) Our results highlight the advantage of potential non-iodinated high-Z agents for use in large-to-obese patients, given that 1) their low dual-energy ratios imply sustained contrast at the high-kVp settings required for this population, and 2) contrast enhancement by high-Z elements is not diminished by large patient size, unlike that of iodine and barium agents.…”

Section: Discussionsupporting

confidence: 85%

The Effect of Patient Diameter on the Dual-Energy Ratio of Selected Contrast-Producing Elements

Lambert¹,

Fitzgerald²,

Edic³

et al. 2017

J Comput Assist Tomogr

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Objectives To assess whether the low- to high-kVp CT number ratio at dual-energy CT (DECT) is affected by changes in patient diameter. Methods Seven contrast-producing elements were housed sequentially within an abdomen phantom. Fat rings enlarged the phantom diameter from 26 to 45 cm. The phantom was scanned using single-energy CT (SECT) at tube potentials of 80 and 140 kVp, and rapid-kVp-switching DECT. Results CT numbers decreased proportionally (~20% CT number reduction for smallest to largest phantom diameters) for low- and high-energy acquisitions, but resulted in consistent dual-energy ratios for each contrast element. For 17/21 material pair combinations, the dual-energy ratio ranges of the two elements did not overlap, implying that discrimination should remain possible for these material pairs at all patient sizes. Conclusions The dual-energy ratio for different contrast materials is largely unaffected by changes in phantom diameter. This should allow for robust separation of most contrast material combinations irrespective of patient size.

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Section: Discussionsupporting

confidence: 85%

The Effect of Patient Diameter on the Dual-Energy Ratio of Selected Contrast-Producing Elements

Lambert¹,

Fitzgerald²,

Edic³

et al. 2017

J Comput Assist Tomogr

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show abstract

“…Although the contrast elements in our study were selected to produce such distinct ratios, the CMEP is not limited to these elements. Several other high-Z elements that are candidates for novel contrast agents such as gold (29), hafnium (30), tantalum (13) and ytterbium (31) have dual-energy ratios similar to that of tungsten. Other elements, such as gadolinium, have ratios similar to that calcium (19), while others still, such as barium, have ratios similar to iodine (18).…”

Section: Discussionmentioning

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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“…Gadolinium also raises toxicity and retention concerns, particularly for the large injected doses required for use as a CT contrast agent compared to MRI (19, 48). Further benefits offered by high-Z contrast elements include greater attenuation and thus brighter image contrast (16, 17, 49), good tolerability (46, 47), utility in double contrast DECT studies (18, 21, 22, 50), and compatibility with metal artifact reduction (27). Agents based on these elements are still however in preclinical toxicity testing stages, with a hafnium chelate (47) and a tantalum nanoparticle-based agent (46) appearing most promising for clinical translation in the medium term.…”

Section: Discussionmentioning

confidence: 99%

Improved Calcium Scoring at Dual-Energy Computed Tomography Angiography Using a High-Z Contrast Element and Novel Material Separation Technique

Lambert

Sun

Ordovás

et al. 2018

J Comput Assist Tomogr

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High Atomic Number Contrast Media Offer Potential for Radiation Dose Reduction in Contrast-Enhanced Computed Tomography

Abstract: Hafnium and tungsten both seem to be candidates for contrast-medium-enhanced CT of normal and obese adult patients with strongly reduced radiation dose at unimpaired image quality. Computed tomography examinations of obese patients will decrease in dose for higher kV values.

Cited by 32 publications

References 9 publications

The Effect of Patient Diameter on the Dual-Energy Ratio of Selected Contrast-Producing Elements

The Effect of Patient Diameter on the Dual-Energy Ratio of Selected Contrast-Producing Elements

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

Improved Calcium Scoring at Dual-Energy Computed Tomography Angiography Using a High-Z Contrast Element and Novel Material Separation Technique

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