Spectral Photon-counting CT: Initial Experience with Dual–Contrast Agent K-Edge Colonography

Muenzel, Daniela; Bar-Ness, Daniel; Roessl, Ewald; Blevis, I.; Bartels, Matthias; Fingerle, Alexander A.; Ruschke, Stefan; Coulon, Philippe; Daerr, Heiner; Kopp, Felix K.; Brendel, Bernhard; Thran, Axel; Rokni, Michal; Herzen, Julia; Boussel, Loîc; Pfeiffer, Franz; Proksa, Roland; Rummeny, Ernst J.; Douek, Philippe; Noël, Peter B.

doi:10.1148/radiol.2016160890

Cited by 124 publications

(109 citation statements)

References 23 publications

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“…The 25 keV threshold was used to reject electronic noise, while the 50 and 90 keV thresholds were used to capture the K‐edge of Gd and Bi, respectively. Setting thresholds based on K‐edges helps improving the differentiation of these contrast agents, as shown in various studies …”

Section: Methodsmentioning

confidence: 93%

“…With PCD‐CT, a series of energy‐bin images can be generated from a single data acquisition, with each energy‐bin image representing the photons detected within a user‐defined energy window. This allows PCD‐CT to measure the change in x‐ray attenuation due to the K‐edges present in materials such as gadolinium (Gd) and bismuth (Bi) …”

Section: Introductionmentioning

confidence: 99%

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Feasibility of multi‐contrast imaging on dual‐source photon counting detector (PCD) CT: An initial phantom study

et al. 2019

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Purpose Photon‐counting‐detector‐computed tomography (PCD‐CT) allows separation of multiple, simultaneously imaged contrast agents, such as iodine (I), gadolinium (Gd), and bismuth (Bi). However, PCDs suffer from several technical limitations such as charge sharing, K‐edge escape, and pulse pile‐up, which compromise spectral separation of multi‐energy data and degrade multi‐contrast imaging performance. The purpose of this work was to determine the performance of a dual‐source (DS) PCD‐CT relative to a single‐source (SS) PCD‐CT for the separation of simultaneously imaged I, Gd, and Bi contrast agents. Methods Phantom experiments were performed using a research whole‐body PCD‐CT and head/abdomen‐sized phantoms containing vials of different I, Gd, Bi concentrations. To emulate a DS‐PCD‐CT, the phantoms were scanned twice on the SS‐PCD‐CT using different tube potentials for each scan. A tube potential of 80 kV (energy thresholds = 25/50 keV) was used for low‐energy tube, while the high‐energy tube used Sn140 kV (Sn indicates tin filter) and thresholds of 25/90 keV. The same phantoms were scanned also on the SS‐PCD‐CT using the chess acquisition mode. In chess mode, the 4 × 4 subpixels within a macro detector pixel are split into two sets based on a chess‐board pattern. With each subpixel set having two energy thresholds, chess mode allows four energy‐bin data sets, which permits simultaneous multi‐contrast imaging. Because of this design, only 50% area of each detector pixel is configured to receive photons of a pre‐defined threshold, leading to 50% dose utilization efficiency. To compensate for this dose inefficiency, the radiation dose for this scan was doubled compared to DS‐PCD‐CT. A 140 kV tube potential and thresholds = 25/50/75/90 keV were used. These settings were determined based on the K‐edges of Gd, and Bi, and were found to yield good differentiation of I/Gd/Bi based on phantom experiments and other literature. The energy‐bin images obtained from each scan (scan pair) were used to generate I‐, Gd‐, Bi‐specific image via material decomposition. Root‐mean‐square‐error (RMSE) between the known and measured concentrations was calculated for each scenario. A 20‐cm water cylinder phantom was scanned on both systems, which was used for evaluating the magnitude of noise, and noise power spectra (NPS) of I/Gd/Bi‐specific images. Results Phantom results showed that DS‐PCD‐CT reduced noise in material‐specific images for both head and body phantoms compared to SS‐PCD‐CT. The noise level of SS‐PCD was reduced from 2.55 to 0.90 mg/mL (I), 1.97 to 0.78 mg/mL (Gd), and 0.85 to 0.74 mg/mL (Bi) using DS‐PCD. NPS analysis showed that the noise texture of images acquired on both systems is similar. For the body phantom, the RMSE for SS‐PCD‐CT was reduced relative to DS‐PCD‐CT from 10.52 to 2.76 mg/mL (I), 7.90 to 2.01 mg/mL (Gd), and 1.91 to 1.16 mg/mL (Bi). A similar trend was observed for the head phantom: RMSE reduced from 2.59 (SS‐PCD) to 0.72 (DS‐PCD) mg/mL (I), 2.02 to 0.58 mg/mL (Gd), and 0.85 to 0.57 mg/mL (Bi). Co...

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Section: Methodsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Feasibility of multi‐contrast imaging on dual‐source photon counting detector (PCD) CT: An initial phantom study

et al. 2019

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“…Differentiation of enteric and intravascular contrast materials may be useful in trauma imaging, where identification of the source of free intra‐abdominal contrast medium enables diagnosis of hemorrhage versus bowel perforation . Muenzel et al demonstrated the potential of photon‐counting CT for differentiation of gadolinium‐enhanced polyps and iodine‐tagged fecal material in a colon phantom . Here, we demonstrated the possibility of using bismuth in vivo as an enteric contrast material to complement iodine and gadolinium intravascular contrast.…”

Section: Discussionmentioning

confidence: 63%

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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“…The material separation demonstrated in these studies, while appearing to be successful, was either qualitative without analysis of quantitative accuracy, or quantitative but limited to small object sizes suitable only for preclinical applications . More importantly, one of the major motivations for performing simultaneous dual‐contrast imaging is to reduce radiation dose . While it is well known that the process of material decomposition amplifies image noise and is therefore less dose efficient, the magnitude of this dose inefficiency has not been well established, particularly for the potential application of performing a single DECT scan to image two contrast agents vs performing two separate single‐energy CT (SECT) scans.…”

Section: Introductionmentioning

confidence: 99%

“…The use of two or more contrast agents has been primarily proposed and demonstrated using photon-counting-detectorbased multienergy CT (MECT) systems in multiple simulation studies, and phantom and animal experiments. [6][7][8][9][10] The use of dual-energy CT (DECT) to perform simultaneous imaging of two or more contrast agents (referred to as dual-or multicontrast imaging), however, has received less attention. With two contrast agents, a mixture of at least three materials (contrast materials and background materials) needs to be decomposed into the basis materials due to the take up of the contrast agent into biological tissues, such as blood or soft tissue.…”

Section: Introductionmentioning

confidence: 99%

Quantitative accuracy and dose efficiency of dual‐contrast imaging using dual‐energy CT: a phantom study

et al. 2019

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Purpose To evaluate the quantitative accuracy and dose efficiency of simultaneous imaging of two contrast agents using dual‐energy computed tomography (DECT), two imaging tasks each representing one potential clinical application were investigated in a phantom study: biphasic liver imaging with iodine and gadolinium, and small bowel imaging with iodine and bismuth. Methods To separate and quantify mixtures of two contrast agents using a single DECT scan, mixed iodine and gadolinium samples were prepared with the contrast enhancement values corresponding to the late arterial (iodine) and the portal‐venous (gadolinium) phase for biphasic liver imaging. Mixed iodine and bismuth samples were prepared mimicking the arterial (iodine) and the enteric (bismuth) enhancement for small bowel imaging. For comparison to the reference condition of performing two single‐energy CT (SECT) scans, contrast samples were prepared separately to mimic separate scans in the arterial/venous phase and arterial/enteric enhancement. Samples were placed in a 35 cm wide water tank and scanned using a third‐generation dual‐source DECT scanner with three tube potential pairs: 80/Sn150, 90/Sn150, and 100/Sn150 kV, all with default dose partitioning between two x‐ray beams to acquire DECT data. The same scanner operated in a single‐energy mode acquired SECT data (120 kV). Total radiation dose (CTDIvol) was matched for the single‐scan DECT and the two‐scan SECT protocols. The DECT protocol was followed by a generic image‐based three‐material decomposition method to determine the material‐specific images, based on which concentrations of each basis material were quantified and noise levels were measured. To compare with the SECT images directly acquired with the SECT protocol, the concentration values in each contrast‐specific image were converted to CT numbers at 120 kV (i.e., virtual SECT (vSECT) images). The noise level and noise power spectra differences between the SECT and vSECT images were compared to evaluate the dose efficiency of the single‐scan DECT protocol. The impact of dose partitioning in the DECT protocol on quantitative dual‐contrast imaging performance was also studied. Results For each imaging task, contrast materials were accurately quantified against the nominal concentrations using the DECT data with strong correlation (R2 ≥ 0.98 for both imaging tasks). Compared to the SECT protocol, the DECT protocol was not dose efficient. With the optimal x‐ray tube potential pair 80/Sn150 kV, the noise level in vSECT images increased by 401%/488% (arterial/portal‐venous) for the biphasic liver imaging task and by 10%/41% (arterial/enteric) for the small bowel imaging task compared to that in SECT images. The corresponding radiation dose increase is 2410%/3357% for the biphasic liver imaging task and 21%/99% for the small bowel imaging task, respectively, to achieve the same noise as that in SECT images. This could be improved by adjusting the dose partitioning in DECT. Conclusions DECT can be used to simultaneously separate and quantify ...

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Spectral Photon-counting CT: Initial Experience with Dual–Contrast Agent K-Edge Colonography

Cited by 124 publications

References 23 publications

Feasibility of multi‐contrast imaging on dual‐source photon counting detector (PCD) CT: An initial phantom study

Feasibility of multi‐contrast imaging on dual‐source photon counting detector (PCD) CT: An initial phantom study

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

Quantitative accuracy and dose efficiency of dual‐contrast imaging using dual‐energy CT: a phantom study

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