A phantom study investigating the relationship between ground‐glass opacity visibility and physical detectability index in low‐dose chest computed tomography

Ichikawa, Katsuhiro; Kobayashi, Takeshi; Sagawa, Motoyasu; Katagiri, Ayako; Uno, Yukiko; Nishioka, Ryo; Matsuyama, Jun

doi:10.1120/jacmp.v16i4.5001

Cited by 15 publications

(9 citation statements)

References 33 publications

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“…NPS was measured using a water phantom with a diameter of 30 cm simulating the absorption characteristics of the adult abdomen . The central 256 × 256 pixels in each uniform noise image with a DFOV of 100 mm obtained by scanning the water phantom were processed by the established method using the 2D FFT . The 2D NPS measurements were radially averaged and binned into 40 frequency bins.…”

Section: Methodsmentioning

confidence: 99%

“…22 The central 256 9 256 pixels in each uniform noise image with a DFOV of 100 mm obtained by scanning the water phantom were processed by the established method using the 2D FFT. 15,17,23 The 2D NPS measurements were radially averaged and binned into 40 frequency bins. To reduce the Medical Physics, 47 (2), February 2020 variability of the NPS results, we considered the average among 80 consecutive axial slices.…”

Section: C System Sensitivity Measurementmentioning

confidence: 99%

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

et al. 2019

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Purpose Two ultra‐high‐resolution (UHR) computed tomography (CT) scanners are clinically available. One is achieved by a CT system with a 0.25 mm × 160 row detector (Detector‐UHR), whereas the other is with a 0.6 mm × 32 row detector with in‐plane comb filtering in a dual source CT (Comb‐UHR). We compared radiation dose efficiencies of the two UHR modes to that of a routine scan mode (RS), using physical image quality measures for an assumed condition of abdominal CT angiography (CTA). Methods A wire phantom, a 300‐mm cylindrical water bath phantom, and a microdisk phantom were used for measuring the modulation transfer function (MTF), noise power spectrum (NPS), and slice sensitivity profiles (SSP), respectively, at CTDIvol of 20 mGy. Images with minimal slice thicknesses were reconstructed by filtered back projection methods. System performance functions (SPF2) based on the prewhitening theorem were calculated by dividing MTF2 by NPS measurements. The ideal observer's detectability index (d'2) was also estimated for a task corresponding to a 1‐mm diameter vessel. Furthermore, a bar‐pattern phantom placed in a water phantom resembling an adult abdomen was scanned, and the visibility of the bars was observed. Results System performance function (SPF2) results showed that Comb‐UHR has a 70% dose efficiency compared to RS and provides better than twofold SPF2 compared to Detector‐UHR. The d'2 values of Detector‐UHR, Comb‐UHR, and RS were 6.5, 14.7, and 16.0, respectively. Although the bar‐pattern phantom images were consistent with the SPF results, bar widths < 1.0 mm for Detector‐UHR and < 0.75 mm for Comb‐UHR and RS were not resolved. Conclusions Though both the UHR modes exhibited system performances extending to 2.6 cycles/mm, they appeared not to be advantageous compared to RS in the conditions applicable to abdominal CTA, because of their insufficient dose efficiencies.

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Section: Methodsmentioning

confidence: 99%

Section: C System Sensitivity Measurementmentioning

confidence: 99%

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

et al. 2019

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“…In the malignant group, the average window width and window level was of 1,356 and −210 HU on pulmonary window. The diameter of the GGO, the size of solid or pathological invasive component, and the composition of ground glass proportion have great limitations to qualitative diagnosis (13). The tumors can be divided into gas type and solid type according to mediastinal window width and window level technology.…”

Section: Discussionmentioning

confidence: 99%

Value of window technique in diagnosis of the ground glass opacities in patients with non-small cell pulmonary cancer

Yao

2016

Oncology Letters

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The aim of the present study was to examine the value of window technique in qualitative diagnosis of the ground glass opacities (GGO) in patients with non-small cell pulmonary cancer. A total of 124 clinically suspected pulmonary cancer patients were analyzed retrospectively. The lesions were affirmed by puncture biopsy, and were GGO on pulmonary window while were invisible on mediastinal window. Sixty-four multi-detector spiral computed tomography with the window width and window level of 1,500 Hounsfield units (HU) and −450 HU on pulmonary window, while the window width and window level of 400 and 40 HU on mediastinal window, was used in the study. The window adjustment technique was used to analyze the window width and window level of lesion on pulmonary window and mediastinal window, for searching invisible threshold on 3-megapixel medical displays. The diagnostic accuracy and the cut-off value were compared on receiver operating characteristic (ROC) curve. The results showed that the window width and window level on pulmonary window and mediastinal window of malignant lesions were significantly less than those of benign ones (P<0.05). The cut-off value on pulmonary window was the window width and window level of 1,300 and −220 HU, the area under the ROC was 0.830 [sensitivity was 72.5%, specificity was 84.3%; 95% confidence interval (CI), 0.712–0.945]. The cut-off value on mediastinal window was the window width and window level of 360 and 30 HU, and the area under the ROC was 0.623 (was 62.0%, specificity was 55.7%; 95% CI, 0.541–0.745). In conclusion, the window technique has high sensitivity and accuracy in qualitative diagnosis of the GGO.

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“…2,12 2.F | System performance function Samei and Richard used the following detectability index, d', to assess the IR techniques' imaging performance: The two-dimensional NPS measurements were radially averaged and split into 40 frequency bins.…”

Section: E | Noise Power Spectrummentioning

confidence: 99%

Quality evaluation of image‐based iterative reconstruction for CT: Comparison with hybrid iterative reconstruction

Kawashima

Ichikawa

Matsubara

et al. 2019

J Applied Clin Med Phys

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The purpose of this study is to evaluate the physical image quality of a commercially available image‐based iterative reconstruction (IIR) system for two object contrasts to resemble a soft tissue (60 HU) and an enhanced vessel (270 HU), and compare the results with those of filtered back projection (FBP) and iterative reconstruction (IR). A 192‐slice computed tomography (CT) scanner was used for data acquisitions. IIR images were processed from the FBP images. Task‐based in‐plane transfer function (TTF) and slice sensitivity profile (SSPtask) were measured from rod objects inside of a 25‐cm diameter water phantom at four dose levels (2.5, 5, 10, and 20 mGy). Noise power spectrum (NPS) was measured from the water‐only part. System performance (SP) function was calculated as TTF2/NPS over FBP, IR, and IIR for comparison. In addition, an image subtraction was performed using images of rod objects, a bar‐pattern phantom, and a clinical abdomen case to observe the noise reduction performance of IIR. As a results, IIR mostly preserved TTF and SSPtask of FBP, whereas IR exhibited enhanced TTF at 10 and 20 mGy for 60 HU contrast and at all doses for 270 HU contrast. SP of IIR at 2.5, 5, 10 mGy (half doses) were similar to those of FBP at 5, 10, 20 mGy, respectively. IR exhibited enhanced SP at medium to high frequencies. The subtracted images showed weak remained edge signals in the bar‐pattern and abdominal images. In conclusion, IIR uniformly improved the task‐based image quality of FBP over the entire frequency range, whereas IR improved the characteristics over medium to high frequencies. The dose reduction potential of IIR estimated from SP is approximately 50%, when allowing the slight signal reductions.

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A phantom study investigating the relationship between ground‐glass opacity visibility and physical detectability index in low‐dose chest computed tomography

Cited by 15 publications

References 33 publications

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

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

Value of window technique in diagnosis of the ground glass opacities in patients with non-small cell pulmonary cancer

Quality evaluation of image‐based iterative reconstruction for CT: Comparison with hybrid iterative reconstruction

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