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

Abstract

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.

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

“…This tungsten compound is not viable for development due to toxicity, but is inexpensive, water soluble, and has the same X-ray attenuation characteristics as potentially viable tungsten-based agents. The contrast materials were formulated in distilled water to concentrations of 10 mg/mL of the active element (20, 26, 27) which provided a contrast enhancement of ~280 HU for both elements at 120 kVp. Although higher contrast enhancement in the coronary arteries can be achieved clinically (28), we chose a relatively low concentration of 10 mg/mL for two reasons.…”

“…In our study the ratio ranges were defined as 0.5 – 1.2, for tungsten, 1.4 – 1.6 for calcium, and 1.8 – ∞ for iodine. These ratio ranges were approximated from different literature sources (25, 33, 34) and validated empirically for the phantom set-up used. For the three image datasets, 60 keV, 80 keV and 67 keV were used for the E1, E2 and E3 inputs respectively.…”

“…For the three image datasets, 60 keV, 80 keV and 67 keV were used for the E1, E2 and E3 inputs respectively. As in previous work, the 60 and 80 keV levels were chosen as they approximate the mean photon energies of the physical 80 and 140 kVp spectra (33, 34). A 67 keV virtual monochromatic spectral level was chosen for E3 as it is has been shown to match the 120 kVp CT numbers of bone (35).…”

“…Unlike iodine and calcium, which both show a marked loss of X-ray attenuation at high kVp CT settings, the high-Z elements provide sufficient X-ray attenuation across the range of kVp settings used for DECT. The signal of high-Z contrast agents can thus be readily separated from the signal of calcium (18–20). While the utility of high-Z contrast agents has been shown in preclinical animal models of abdominal disease (21, 22), their performance for quantitative separation tasks such as CACS remain unknown.…”

Engineering Multifunctional Gold Decorated Dendritic Mesoporous Silica/Tantalum Oxide Nanoparticles for Intraperitoneal Tumor‐Specific Delivery

“…Generally, imaging patients especially those with larger body sizes requires high voltages (100–140 KeV). It has been reported that Ta (K‐edge 67 KeV) has enhanced CT contrast at ≈100 KeV and Au (K‐edge 81 Kev) shows high contrast at around 120 KeV, more advantageous over the conventional iodine‐based contrast agents (K‐edge 33 Kev) for high voltage imaging applications.…”