Technical Note: Performance comparison of ultra‐high‐resolution scan modes of two clinical computed tomography systems

Kawashima, Hiroki; Ichikawa, Katsuhiro; Takata, Takushi; Nagata, Hiroji; Hoshika, Minori; Akagi, Noriaki

doi:10.1002/mp.13949

Cited by 27 publications

(17 citation statements)

References 30 publications

(56 reference statements)

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“…The noise power spectrum (NPS) was measured from the images of the water phantom of 110-mm diameter using an established method based on two-dimensional fast Fourier transform (FFT) [4]. An index of system sensitivity (SPF; system performance function) [1] that was computed by the following formula:…”

Section: Imaging Performance Comparisonmentioning

confidence: 99%

“…The scanner's geometric design (the number of detectors, detector pitch, focal spot size, and magnifications) plays an essential role in determining the spatial resolution of a CT image [1]. In a general-purpose clinical CT scanner, the magnification is approximately 1.8-2.0 to ensure the scan field of view (SFOV) to examine patients with different sizes.…”

Section: Introductionmentioning

confidence: 99%

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A challenge for high-speed and high-resolution CT for extremities with clinical feasibility

Kawashima,

Ichikawa

2024

Medical Imaging 2024: Physics of Medical Imaging

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Existing micro-CT systems can visualize the trabecular bone microstructure; however, its application is limited because of the small scan field of view and the long scan time for clinical use. We developed a high-resolution CT for human extremities (HRCTe) with clinical feasibility, which can achieve a spatial resolution of ~100 µm and a short acquisition time of 6.5 seconds. A complementary metal-oxide-semiconductor X-ray detector with a 99-µm pixel pitch and a compact X-ray tube with a focal spot size of 0.8 mm were installed in the HRCTe. In order to maximize the performance of the Xray tube and the detector, we introduced a low-magnification geometry. This resulted in an effective focal spot size of 0.14 mm, ensuring the resolution performance of the pixel pitch at the iso-center of 81µm. The scan z-directional coverage was 50 mm. For the technical assessment, modulation transfer function (MTF) and noise power spectrum (NPS) were measured using a wire phantom and a water phantom, respectively. A squared system performance function (SPF 2 ) was calculated as MTF 2 /NPS. These results were compared with those measured using a high-resolution mode of a whole-body CT with a 0.25-mm detector (WCT) and a dental CT (DCT). The 5%MTF of the HRCT, WCT, and DCT were approximately 3.8, 1.9, and 1.5 mm -1 . The SPF 2 at 2.0 mm -1 of the developed CT was 260% higher than that of WCT. The trabecular bones in an anthropomorphic foot phantom were visualized much clearer with HRCTe than with both WCT and DCT.

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Section: Imaging Performance Comparisonmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A challenge for high-speed and high-resolution CT for extremities with clinical feasibility

Kawashima,

Ichikawa

2024

Medical Imaging 2024: Physics of Medical Imaging

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“…HRCT as a post-processing feature (mainly a narrow slice thickness of 1–2 mm) is useful for lung analysis in general [ 14 , 15 ], and in particular for analysis of NSIP as in SSc-ILD [ 9 , 16 ]. It shows submillimeter structures, bronchial structures and lung parenchyma pathologies [ 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

Influence of CT Image Matrix Size and Kernel Type on the Assessment of HRCT in Patients with SSC-ILD

et al. 2022

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Background: Interstitial lung disease (ILD) is a frequent complication of systemic sclerosis (SSc), and its early detection and treatment may prevent deterioration of lung function. Different vendors have recently made larger image matrices available as a post-processing option for computed tomography (CT), which could facilitate the diagnosis of SSc-ILD. Therefore, the objective of this study was to assess the effect of matrix size on lung image quality in patients with SSc by comparing a 1024-pixel matrix to a standard 512-pixel matrix and applying different reconstruction kernels. Methods: Lung scans of 50 patients (mean age 54 years, range 23–85 years) with SSc were reconstructed with these two different matrix sizes, after determining the most appropriate kernel in a first step. Four observers scored the images on a five-point Likert scale regarding image quality and detectability of clinically relevant findings. Results: Among the eight tested kernels, the Br59-kernel (sharp) reached the highest score (19.48 ± 3.99), although differences did not reach statistical significance. The 1024-pixel matrix scored higher than the 512-pixel matrix HRCT overall (p = 0.01) and in the subcategories sharpness (p < 0.01), depiction of bronchiole (p < 0.01) and overall image impression (p < 0.01), and lower for the detection of ground-glass opacities (GGO) (p = 0.04). No significant differences were found for detection of extent of reticulations/bronchiectasis/fibrosis (p = 0.50) and image noise (p = 0.09). Conclusions: Our results show that with the use of a sharp kernel, the 1024-pixel matrix HRCT, provides a slightly better subjective image quality in terms of assessing interstitial lung changes, whereby GGO are more visible on the 512-pixel matrix. However, it remains to be answered to what extent this is related to the improved representation of the smallest structures.

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“…Spatial resolution of a given CT image is technically limited by the hardware restrictions of the CT system, e.g. the detector pixel size or the focal spot size [4]. Within these given limits, spatial resolution can be modified by the reconstruction parameters selected by the user.…”

Section: Introductionmentioning

confidence: 99%

1024-pixel image matrix for chest CT – Impact on image quality of bronchial structures in phantoms and patients

et al. 2020

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Objectives To compare objective and subjective image quality of bronchial structures between a 512pixel and a 1024-pixel image matrix for chest CT in phantoms and in patients. Materials and methods First, a two-size chest phantom was imaged at two radiation doses on a 192-slice CT scanner. Datasets were reconstructed with 512-, 768-, and 1024-pixel image matrices and a sharp reconstruction kernel (Bl64). Image sharpness and normalized noise power spectrum (nNPS) were quantified. Second, chest CT images of 100 patients were reconstructed with 512-and 1024-pixel matrices and two blinded readers independently assessed objective and subjective image quality. In each patient dataset, the highest number of visible bronchi was counted for each lobe of the right lung. A linear mixed effects model was applied in the phantom study and a Welch's t-test in the patient study. Results Objective image sharpness and image noise increased with increasing matrix size and were highest for the 1024-matrix in phantoms and patients (all, P<0.001). nNPS was comparable among the three matrices. Objective image noise was on average 16% higher for the 1024matrix compared to the 512-matrix in patients (P<0.0001). Subjective evaluation in patients yielded improved sharpness but increased image noise for the 1024-compared to the 512matrix (both, P<0.001). There was no significant difference between highest-order visible bronchi (P>0.07) and the overall bronchial image quality between the two matrices (P>0.22). Conclusion Our study demonstrated superior image sharpness and higher image noise for a 1024-compared to a 512-pixel matrix, while there was no significant difference in the depiction and subjective image quality of bronchial structures for chest CT.

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Technical Note: Performance comparison of ultra‐high‐resolution scan modes of two clinical computed tomography systems

Cited by 27 publications

References 30 publications

A challenge for high-speed and high-resolution CT for extremities with clinical feasibility

A challenge for high-speed and high-resolution CT for extremities with clinical feasibility

Influence of CT Image Matrix Size and Kernel Type on the Assessment of HRCT in Patients with SSC-ILD

1024-pixel image matrix for chest CT – Impact on image quality of bronchial structures in phantoms and patients

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