Dose-efficient ultrahigh-resolution scan mode using a photon counting detector computed tomography system

Leng, Shuai; Yu, Zhicong; Halaweish, Ahmed F.; Kappler, S.; Hähn, Katharina; Henning, André; Li, Zhoubo; Lane, John I.; Levin, David L.; Jorgensen, Steven M.; Ritman, Erik L.; McCollough, Cynthia H.

doi:10.1117/1.jmi.3.4.043504

Cited by 110 publications

(107 citation statements)

References 36 publications

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“…However, the system is usually operated using macro pixels (0.9 mm by 0.9 mm) by grouping together 4 by 4 native detector cells (0.5 mm by 0.5 mm pixel size at iso-center). To increase spatial resolution, an UHR mode was recently introduced in which 0.45 mm × 0.45 mm detector pixels were used, which corresponded to a pixel size of 0.25 mm × 0.25 mm at the iso-center [13]. This mode, however, only had one energy threshold and therefore lacked energy discrimination information.…”

Section: Methodsmentioning

confidence: 99%

“…The same 14 renal stones with mixed compositions were also used to assess the influence of spatial resolution and image noise in dual energy applications. Dual-energy analysis was performed to differentiate stone composition and quantify the amount of UA and NUA based on the CT number ratio (CTR) of each pixel inside the stone, which was calculated as the ratio of the CT numbers in the low-energy bin (25 to 75 keV) to those in the high-energy bin (75 to 140 keV) [13]. The results were compared with the reference standard achieved with microCT scans [15].…”

Section: Methodsmentioning

confidence: 99%

“…An ultra-high-resolution (UHR) imaging technique was recently developed on a research PCCT system with the effective detector size of 0.25 mm at the isocenter, compared to the 0.5 mm of standard macro mode on PCD and 0.5–0.625 mm on commercial EIDs [13]. Phantom and cadaveric studies demonstrated improved spatial resolution compared to regular imaging mode without sacrificing dose efficiency, unlike the UHR mode achieved with attenuating comb filters on EID systems [13]. This imaging technique can benefit lung, temporal bone, musculoskeletal and vascular imaging where excellent spatial resolution is required to delineate small anatomy and pathology.…”

Section: Introductionmentioning

confidence: 99%

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Ultra-high spatial resolution multi-energy CT using photon counting detector technology

Leng

Gutjahr

Ferrero

et al. 2017

Medical Imaging 2017: Physics of Medical Imaging

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Two ultra-high-resolution (UHR) imaging modes, each with two energy thresholds, were implemented on a research, whole-body photon-counting-detector (PCD) CT scanner, referred to as sharp and UHR, respectively. The UHR mode has a pixel size of 0.25 mm at iso-center for both energy thresholds, with a collimation of 32 × 0.25 mm. The sharp mode has a 0.25 mm pixel for the low-energy threshold and 0.5 mm for the high-energy threshold, with a collimation of 48 × 0.25 mm. Kidney stones with mixed mineral composition and lung nodules with different shapes were scanned using both modes, and with the standard imaging mode, referred to as macro mode (0.5 mm pixel and 32 × 0.5 mm collimation). Evaluation and comparison of the three modes focused on the ability to accurately delineate anatomic structures using the high-spatial resolution capability and the ability to quantify stone composition using the multi-energy capability. The low-energy threshold images of the sharp and UHR modes showed better shape and texture information due to the achieved higher spatial resolution, although noise was also higher. No noticeable benefit was shown in multi-energy analysis using UHR compared to standard resolution (macro mode) when standard doses were used. This was due to excessive noise in the higher resolution images. However, UHR scans at higher dose showed improvement in multi-energy analysis over macro mode with regular dose. To fully take advantage of the higher spatial resolution in multi-energy analysis, either increased radiation dose, or application of noise reduction techniques, is needed.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultra-high spatial resolution multi-energy CT using photon counting detector technology

Leng

Gutjahr

Ferrero

et al. 2017

Medical Imaging 2017: Physics of Medical Imaging

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“…In addition, two ultra-high-spatial-resolution imaging modes, with detector size of 0.25 mm × 0.25 mm at the iso-center, are available. This enables simultaneous multi-energy CT data acquisition with image thickness of 0.25 mm [12, 13]. Detailed descriptions of the system can be found elsewhere [5].…”

Section: Methodsmentioning

confidence: 99%

Impact of photon counting detector technology on kV selection and diagnostic workflow in CT

Zhou

Abdurakhimova

Bruesewitz

et al. 2018

Medical Imaging 2018: Physics of Medical Imaging

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The purpose of this study is to determine the optimal iodine contrast-to-noise ratio (CNR) achievable for different patient sizes using virtual-monoenergetic-images (VMIs) and a universal acquisition protocol on photon-counting-detector CT (PCD-CT), and to compare results to those from single-energy (SE) and dual-source-dual-energy (DSDE) CT. Vials containing 3 concentrations of iodine were placed in torso-shaped water phantoms of 5 sizes and scanned on a 2nd generation DSDE scanner with both SE and DE modes. Tube current was automatically adjusted based on phantom size with CTDIvol ranging from 5.1 to 22.3 mGy. PCD-CT scans were performed at 140 kV, 25 and 75 keV thresholds, with CTDIvol matched to the SE scans. DE VMIs were created and CNR was calculated for SE images and DE VMIs. The optimal kV (SE) or keV (DE VMI) was chosen at the point of highest CNR with no noticeable artifacts. For 10 mgI/cc vials in the 35 cm phantom, the optimal CNR of VMIs on PCD (22.6@50keV) was comparable to that of the best DSDE protocol (23.9@50keV) and was higher than that of the best SE protocol (19.7@80kV). In general, the difference of optimal CNR between PCD and SE increased with phantom size, with PCD 50 keV VMIs having an equivalent CNR (0.6% difference) with that of SE at the 25 cm phantom and 57% higher CNR at the 45 cm phantom. PCD-CT demonstrated comparable iodine CNR of VMIs to that of DSDE across patient sizes. Whereas SE and DSDE CT exams require use of patient-size-specific acquisitions settings, our findings point to the ability of PCD-CT to simplify protocol selection, using a single VMI keV setting (50 keV), acquisition kV (140 kV), and energy thresholds (25 and 75 keV) for all patient sizes, while achieving optimal or near optimal iodine CNR values.

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“…In addition, photon-counting detectors do not suffer from the fill factor limitations inherent to the traditional energy-integration detectors, thereby allowing the design of smaller detector pixels to achieve dose-efficient high resolution CT without the need for comb/grid filters. Recently Leng et al 1,2 demonstrated the high resolution acquisition modes of a whole-body research PCD-CT system. Due to smaller per-pixel area in combination with narrow energy bin required for higher image contrast and better spectral sampling, the high resolution modes are inherently prone to higher noise levels in the energy bin images.…”

Section: Introductionmentioning

confidence: 99%

Ultra-high resolution photon-counting detector CT reconstruction using spectral prior image constrained compressed-sensing (UHR-SPICCS)

Rajendran

Tao

Abdurakhimova

et al. 2018

Medical Imaging 2018: Physics of Medical Imaging

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Photon-counting detector based CT (PCD-CT) enables dose efficient high resolution imaging, in addition to providing multi-energy information. This allows better delineation of anatomical structures crucial for several clinical applications ranging from temporal bone imaging to pulmonary nodule visualization. Due to the smaller detector pixel sizes required for high resolution imaging, the PCD-CT images suffer from higher noise levels. The image quality is further degraded in narrow energy bins as a consequence of low photon counts. This limits the potential benefits that high-resolution PCD-CT could offer. Conventional reconstruction techniques such as the filtered back projection (FBP) have poor performance when reconstructing noisy CT projection data. To enable low noise multi-energy reconstructions, we employed a spectral prior image constrained compressed sensing (SPICCS) framework that exploits the spatio-spectral redundancy in the multi-energy acquisitions. We demonstrated noise reduction in narrow energy bins without losing energy-specific attenuation information and spatial resolution. We scanned an anthropomorphic head phantom, and a euthanized pig using our whole-body prototype PCD-CT system in the ultra-high resolution mode at 120kV. Image reconstructions were performed using SPICCS and compared with conventional FBP. Noise reduction of 18 to 46% was noticed in narrow energy bins corresponding to 25 – 65 keV and 65 – 12 keV, while the mean CT number was preserved. Spatial resolution measurement showed similar modulation transfer function (MTF) values between FBP and SPICCS, demonstrating preservation of spatial resolution.

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Dose-efficient ultrahigh-resolution scan mode using a photon counting detector computed tomography system

Cited by 110 publications

References 36 publications

Ultra-high spatial resolution multi-energy CT using photon counting detector technology

Ultra-high spatial resolution multi-energy CT using photon counting detector technology

Impact of photon counting detector technology on kV selection and diagnostic workflow in CT

Ultra-high resolution photon-counting detector CT reconstruction using spectral prior image constrained compressed-sensing (UHR-SPICCS)

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