Iodine contrast-to-noise ratio improvement at unit dose and contrast media volume reduction in whole-body photon-counting CT

Sawall, Stefan; Klein, Laura; Amato, Carlo; Wehrse, E.; Dorn, Sabrina; Maier, Joscha; Heinze, Sarah; Ziener, Christian H.; Uhrig, Monika; Kachelrieß, Marc

doi:10.1016/j.ejrad.2020.108909

Cited by 48 publications

(33 citation statements)

References 19 publications

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“…This effect has been investigated for iodine in a recent publication. 12 For the same phantom size and tube voltage, the values herein found are compatible with the one of the publication. For all high-Z elements, the simulations were in good agreement with the measurements.…”

Section: Summary and Discussionsupporting

confidence: 85%

“…In case of two energy thresholds, the final image

f_{P C 2}

is calculated as:

f_{P C 2} = w_{1} f_{1} + w_{2} f_{2},

where

f_{1 false/ 2}

are the bin images and

w_{1 false/ 2}

are the weighting coefficients with

w_{1} + w_{2} = 1

. The CNR of the final image can be directly computed as:

{CNR}_{PC 2} = \frac{{false(w_{1} normalΔ μ_{1} + w_{2} normalΔ μ_{2} false)}^{2}}{w_{1}^{2} V_{1} + w_{2}^{2} V_{2}},

If the weights are chosen to maximize the

{CNR}_{normalPC 2}

(i.e.,

w_{i} \propto Δ μ_{i} / V_{i}

), the CNRCD of the final image can be directly calculated as: 12,13,14

{CNRCD}_{truemax} = \sqrt{{CNRCD}_{1}^{2} + {CNRCD}_{2}^{2}},

where

{CNRCD}_{i}

is the CNRCD of the i‐th bin image.…”

Section: Methodsmentioning

confidence: 99%

“…If the weights are chosen to maximize the CNR PC2 (i.e., w i / Δμ i =V i ), the CNRCD of the final image can be directly calculated as: 12,13,14 CNRCD max ¼…”

Section: A Contrast In Pcctmentioning

confidence: 99%

“…The advantages of PC detectors over EI detectors have been already partially investigated and improvements have been shown regarding spatial resolution, 10 image noise 11 , and iodine contrast enhancement. 12 Another feature of PC detectors is the presence of multiple and adjustable energy thresholds which can be used to differentiate incoming photons according to their energy and therefore provide spectral information. EI detectors are also capable of spectral imaging, but techniques like dual-source, kV-switching or sandwich detector have to be used.…”

Section: Introductionmentioning

confidence: 99%

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Potential of contrast agents based on high‐Z elements for contrast‐enhanced photon‐counting computed tomography

et al. 2020

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Purpose In clinics, only iodine‐ and barium‐based contrast agents are currently used for contrast‐enhanced x‐ray computed tomography (CT). Recently, the introduction of new photon‐counting (PC) detectors increased the interest in developing new contrast agents based on heavier elements. These elements may provide more contrast and spectral information compared to iodine and barium thanks to their k‐edges at higher energies. In this paper, the potential of high‐Z elements in contrast‐enhanced CT was evaluated for different patient sizes and x‐ray spectra using a PC detector. Methods An adult liver phantom with five high‐Z element solutions (iodine, gadolinium, ytterbium, tungsten, and bismuth) was scanned with a whole‐body photon‐counting computed tomography (PCCT) prototype. For each element, the contrast‐to‐noise ratio at unit concentration and at unit dose (CNRCD) was evaluated in low threshold images (T0=20keV) as function of the tube voltage (80, 100, 120, and 140 kV) and in bin images (tube voltage = 120 kV) as function of the higher threshold (T0=20keV and T1∈false[50,90false]keV). Simulations were performed for validation with measurements and to investigate more elements (cerium and gold), different patient sizes (infant, adult, and obese), and spectrum filtration (with and without 0.4‐mm tin filter). The dose reductions associated with the CNRCD improvements over iodine were quantified as well. Results CNRCD improvements and dose reductions depend on the investigated scenario. For the infant phantom, dose reductions around 30% were reached using cerium or gadolinium in combination with the tin filter. For the adult and obese phantom, reductions around 50% were provided by gadolinium or ytterbium in combination with the tin filter. Independently of the high‐Z element, the CNRCD of two optimally combined bin images was higher than the CNRCD of the low threshold image. Good agreement was found between measurements and simulations. Conclusions Between the investigated elements, gadolinium resulted to have the highest potential as novel contrast agent in PCCT, providing significant dose reductions for all patient sizes. Compared to the other elements, the implementation of gadolinium as CT contrast agent may be facilitated since it is already deployed as contrast agents for magnetic resonance imaging.

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Section: Summary and Discussionsupporting

confidence: 85%

“…In case of two energy thresholds, the final image

f_{P C 2}

is calculated as:

f_{P C 2} = w_{1} f_{1} + w_{2} f_{2},

where

f_{1 false/ 2}

are the bin images and

w_{1 false/ 2}

are the weighting coefficients with

w_{1} + w_{2} = 1

. The CNR of the final image can be directly computed as:

{CNR}_{PC 2} = \frac{{false(w_{1} normalΔ μ_{1} + w_{2} normalΔ μ_{2} false)}^{2}}{w_{1}^{2} V_{1} + w_{2}^{2} V_{2}},

If the weights are chosen to maximize the

{CNR}_{normalPC 2}

(i.e.,

w_{i} \propto Δ μ_{i} / V_{i}

), the CNRCD of the final image can be directly calculated as: 12,13,14

{CNRCD}_{truemax} = \sqrt{{CNRCD}_{1}^{2} + {CNRCD}_{2}^{2}},

where

{CNRCD}_{i}

is the CNRCD of the i‐th bin image.…”

Section: Methodsmentioning

confidence: 99%

“…If the weights are chosen to maximize the CNR PC2 (i.e., w i / Δμ i =V i ), the CNRCD of the final image can be directly calculated as: 12,13,14 CNRCD max ¼…”

Section: A Contrast In Pcctmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Potential of contrast agents based on high‐Z elements for contrast‐enhanced photon‐counting computed tomography

et al. 2020

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“…Von den Geräteherstellern wurden hierfür unterschiedliche Techniken entwickelt, um selbst mit den nicht energieselektiven energieintegrierenden Detektoren dennoch das energieabhängige Absorptionsverhalten erfassen zu können. Dies wurde zumindest bei 2 unterschiedlichen Energien realisiert, man spricht dann von "Dual-Energy-CT" [31] [35,36].…”

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The Eye of the CT Scanner: The story of learning to see the invisible or from the fluorescent screen to the photon-counting detector

Schlemmer

2021

Rofo

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Roentgen’s photographs with the “new kind of rays” triggered a worldwide storm of enthusiasm in all social circles. It was a stroke of luck that the photographic dry plates available to him were also sensitive to invisible X-rays. The discovery, research and utilization of X-rays are based on methods for making them visible, from fluorescent screens to photographic plates and digital X-ray detectors. From this point of view, this paper aims to outline the 125-year success story of X-ray imaging from its discovery to the recent development of photon-counting detectors. The scientific-historical view during the transition from the 19th to the 20th century reveals an impressive period of profound scientific and social upheaval in which revolutionary discoveries and technological developments led to enormous progress in medicine. The cross-fertilization of physics and medicine and their combination with inventiveness, engineering and entrepreneurial spirit created the impressive possibilities of today’s imaging diagnostics. This contribution accompanies the Roentgen Lecture the author gave on November 13, 2020 in Roentgen’s birth house as part of its inauguration and the closing ceremony of the 101st Congress of the German Roentgen Society in Remscheid-Lennep. Key Points: Citation Format

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No gadolinium K‐edge detected on the first clinical photon‐counting computed tomography scanner

Baubeta,

Laurin Gadsböll,

Will

et al. 2024

J Applied Clin Med Phys

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PurposeThis study aimed to elucidate whether gadolinium contrast in clinically relevant doses can be used with photon‐counting computed tomography (PCCT) as an alternative contrast agent in clinical applications.Material/methodsA CTDI phantom with 3D printed rods filled with different concentrations of gadolinium and iodine contrast was scanned in a PCCT and an energy‐integrated computed tomography (EICT). Attenuation values at different monoenergetic steps were extracted for each contrast concentration.ResultsFor PCCT, gadolinium reached an attenuation >100 HU (103 HU) at 40 keV with a concentration 5 mmol/L whereas the same level was reached at 50 keV (118 HU) for 10 mmol/L and 90 keV (114 HU) for 25 mmol/L. For iodine, the same level of attenuation was reached at 100 keV (106 HU) with a concentration 8.75 mg I/mL.For EICT the lowest gadolinium contrast concentration needed to reach >100 HU (108 HU) was 10 mmol/L at 50 keV. For 25 mmol/L 100 HU was reached at 100 keV. For iodine contrast 108 HU was reached at 110 keV for 8.75 mg I/mL.ConclusionNo K‐edge potential or difference in attenuation curves between iodine and gadolinium contrast is detected on the first clinical available PCCT. Clinically relevant attenuation levels were barely achieved in this setting with gadolinium concentrations approved for human use. The results of this study suggest that, given current scanning technology, gadolinium is not a clinically useful contrast agent for computed tomography because no K‐edge was detected.

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Iodine contrast-to-noise ratio improvement at unit dose and contrast media volume reduction in whole-body photon-counting CT

Cited by 48 publications

References 19 publications

Potential of contrast agents based on high‐Z elements for contrast‐enhanced photon‐counting computed tomography

Potential of contrast agents based on high‐Z elements for contrast‐enhanced photon‐counting computed tomography

The Eye of the CT Scanner: The story of learning to see the invisible or from the fluorescent screen to the photon-counting detector

No gadolinium K‐edge detected on the first clinical photon‐counting computed tomography scanner

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