記述言語：英語   掲載種別：研究論文（学術雑誌）  

IntroductionThe severity of obstructive sleep apnea (OSA) is assessed by the apnea-hypopnea index (AHI) determined from polysomnography (PSG). However, PSG requires a specialized facility with well-trained specialists and takes overnight. Therefore, simple tools, which could distinguish severe OSA, have been needed before performing PSG.ObjectivesWe propose the new index using cine-MRI as a screening test to differentiate severe OSA patients, who would need PSG and proper treatment.MethodsThirty-six patients with suspected OSA (mean age 54.6 y, mean AHI 52.6 events/h, 33 males) underwent airway cine-MRI at the fourth cervical vertebra level during 30 s of free breathing and PSG. The minimum airway ellipticity (AE) in 30 s duration was measured, and was defined as the severity of OSA. Patients were divided into severe OSA, not-severe OSA, and normal groups, according to PSG results. The comparison of AE between any two of the three groups was performed by Wilcoxon rank-sum test. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-off of AE for identifying severe OSA patients.ResultsThe minimum AE for severe OSA was significantly lower than that for not-severe OSA and normal (severe, 0.170.16; not severe, 0.31 +/- 0.17; normal, 0.38 +/- 0.19, P<.05). ROC analysis revealed that the optimal cutoff of the minimum AE 0.21 identified severe OSA patients, with an area under the curve of 0.75, 68% sensitivity, and 83% specificity.ConclusionAE is a feasible quantitative index, and a promising screening test for detecting severe OSA patients.

DOI： 10.1111/crj.12598

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1259/bjr.20160007

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本循環器学会  

<p><b><i>Background:</i></b> This study evaluated right ventricular (RV) volume, strain, and morphology using cardiac 4-dimensional computed tomography (4D-CT) to detect pulmonary hypertension (PH) in adults with repaired tetralogy of Fallot (TOF) scheduled for transcatheter pulmonary valve implantation (TPVI).</p><p><b><i>Methods and Results:</i></b> Using cardiac 4D-CT data, we calculated RV strain in 3 different geometries and RV outflow tract (RVOT) mass in 42 patients with repaired TOF. We compared RV strain and RVOT mass between patients with and without PH. Receiver operating characteristic (ROC) analysis was conducted to evaluate the diagnostic performance of these measurements for identifying PH. Four-chamber (4ch) strain was significantly smaller for patients with (n=10) than without (n=32) PH (8.8±1.7% vs. 11.1±2.4%, respectively; P<0.01), whereas RVOT mass was significantly larger in the PH group (12.5±3.5 vs. 9.2±3.2 cm²; P<0.01). ROC analysis of the diagnostic performance revealed that the respective sensitivity and specificity was 70% and 84% (area under the curve [AUC]=0.784) for 4ch strain of 8.8%; 80% and 69% (AUC=0.766) for RVOT mass of 10.7 cm²; and 80% and 81% (AUC=0.844) for a 4ch strain/RVOT mass ratio of 0.97.</p><p><b><i>Conclusions:</i></b> RVOT mass and 4ch strain obtained from cardiac 4D-CT may be helpful for identifying PH in patients with repaired TOF.</p>

DOI： 10.1253/circj.cj-24-0386

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Radiography  

Introduction: Dual-energy computed tomography (DECT) can generate virtual non-contrast (VNC) images. Herein, we sought to improve the accuracy of VNC images by identifying the optimal slope of contrast media (SCM) for VNC-image generation based on the iodine concentration and subject's body size. Methods: We used DECT to scan a multi-energy phantom including four iodine concentration rods (15, 10, 5, and 2 mg/mL), and 240 VNC images (eight SCM ranging from 0.49 to 0.56 × three body sizes × ten scans) that were generated by three-material decomposition. The CT number of each iodine and solid water rod part was measured in each VNC image. The difference in the CT number between the iodine and the solid water rod part was calculated and compared using paired t-test or repeated measures ANOVA. Results: The SCM that achieved an absolute value of the difference in CT number of <5.0 Hounsfield units (HU) for all body sizes simultaneously was greater at lower iodine concentration (SCM of 0.5, 0.51, and 0.53 at 10, 5, and 2 mg/mL iodine, respectively). At an iodine concentration of 15 mg/mL, no SCM achieved an absolute difference of <5.0 HU in CT number for all body sizes simultaneously. At all iodine concentrations, the SCM achieving the minimal difference in the CT number increased with the increase in body size. Conclusion: By adjusting the SCM according to the iodine concentration and body size, it is possible to generate VNC images with an accuracy of <5.0 HU. Implications for practice: Improving the accuracy of VNC images minimizing incomplete iodine subtraction would make it possible to replace true non-contrast (TNC) images with VNC images and reduce the radiation dose.

DOI： 10.1016/j.radi.2023.03.003

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Radiological Physics and Technology  

PURPOSE: We assessed the physical properties of virtual monochromatic images (VMIs) obtained with different energy levels in various contrast settings and radiation doses using deep learning-based spectral computed tomography (DL-Spectral CT) and compared the results with those from single-energy CT (SECT) imaging. MATERIALS AND METHODS: A Catphan® 600 phantom was scanned by DL-Spectral CT at various radiation doses. We reconstructed the VMIs obtained at 50, 70, and 100 keV. SECT (120 kVp) images were acquired at the same radiation doses. The standard deviations of the CT number and noise power spectrum (NPS) were calculated for noise characterization. We evaluated the spatial resolution by determining the 10% task-based transfer function (TTF) level, and we assessed the task-based detectability index (d'). RESULTS: Regardless of the radiation dose, the noise was the lowest at 70 keV VMI. The NPS showed that the noise amplitude at all spatial frequencies was the lowest among other VMI and 120 kVp images. The spatial resolution was higher for 70 keV VMI compared to the other VMIs, except for high-contrast objects. The d' of 70 keV VMI was the highest among the VMI and 120 kVp images at all radiation doses and contrast settings. The d' of the 70 keV VMIs at the minimum dose was higher than that at the maximum dose in any other image. CONCLUSION: The physical properties of the DL-Spectral CT VMIs varied with the energy level. The 70 keV VMI had the highest detectability by far among the VMI and 120-kVp images. DL-Spectral CT may be useful to reduce radiation doses.

DOI： 10.1007/s12194-022-00695-x

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記述言語：英語   出版者・発行元：(公社)日本放射線技術学会  

深層学習ベースのデュアルエネルギースペクトラルCT(DL-Spectral CT)により取得した、仮想単色X線画像(VMI)の物理的特性について調査した。Catphan 600ファントムをDL-Spectral CTにより種々の照射線量で撮像し、50keV、70keVおよび100keVで得られたVMIを再構成した。その際、同じ照射線量でシングルエネルギーCT(SECT)画像も撮像した。これらの画像を評価した結果、ノイズは70keVで得られたVMI(70keV VMI)が最も小さかったが、ノイズパワースペクトルでは、70keV VMIのノイズ振幅が他のVMIやSECT画像に比べ低かった。また、70keV VMIの空間分解能は他のVMIよりも高く、70keV VMIのtask-based detectability index(d')では他のVMIやSECT画像よりも高かった一方、最小線量における70keV VMIのd'では、他の画像の最大線量よりも高値であった。これらの所見から、70keV VMIでは低放射線量でも高検出能が保たれていることが示され、DL-Spectral CTは放射線量の低減に有用と判断された。

記述言語：英語   掲載種別：研究論文（学術雑誌）  

PURPOSE: Although a novel deep learning software was proposed using post-processed images obtained by the fusion between X-ray images of normal post-operative radiography and surgical sponge, the association of the retained surgical item detectability with human visual evaluation has not been sufficiently examined. In this study, we investigated the association of retained surgical item detectability between deep learning and human subjective evaluation. METHODS: A deep learning model was constructed from 2987 training images and 1298 validation images, which were obtained from post-processing of the image fusion between X-ray images of normal post-operative radiography and surgical sponge. Then, another 800 images were used, i.e., 400 with and 400 without surgical sponge. The detection characteristics of retained sponges between the model and a general observer with 10-year clinical experience were analyzed using the receiver operator characteristics. RESULTS: The following values from the deep learning model and observer were, respectively, derived: Cutoff values of probability were 0.37 and 0.45; areas under the curves were 0.87 and 0.76; sensitivity values were 85% and 61%; and specificity values were 73% and 92%. CONCLUSION: For the detection of surgical sponges, we concluded that the deep learning model has higher sensitivity, while the human observer has higher specificity. These characteristics indicate that the deep learning system that is complementary to humans could support the clinical workflow in operation rooms for prevention of retained surgical items.

DOI： 10.1007/s11548-022-02816-8

記述言語：英語   出版者・発行元：(NPO)日本歯科放射線学会  

CT画質や照射線量低減に対し、深層学習をベースとした画像再構成(DLR)がもたらす効果について検討し、歯科インプラント手術における術前画像診断として、低照射線量マルチスライスCT(MDCT)スキャンによるプロトコルを提案した。ヒト頭部モデル下顎ファントムを用いて、読影者評価には、Catphan phantom600とTOSファントムを物理特性分析に用いた。管電圧120kV、管電流120-60mA～40-30mAの条件下で、320列MDCT装置でスキャンし、DLR画像を再構成した。また、120mAで取得し、フィルタ補正逆投影(FBP)法で再構成した画像を参照画像として比較した。なお、再構成処理した画像は、読影者2名により、それぞれ盲検下で4点スケール法で画質を評価した。その結果、管電流40mAで取得しDLRで再構成した画像(40DLR)と、参照プロトコルによる取得画像の画質に有意差はみられなかったが、40DLRで取得した1.0cycles/minでのシステム性能関数(SPF)では、参照プロトコルで取得した画像に比べ、156.7%も改善が得られた。以上の実験結果から、今回提案したDLRプロトコルにより、照射線量が2/3低減することに成功し、歯科インプラント手術に際し、高速スキャンで最小侵襲の術前画像診断として、有用なMDCT画質が得られることが確認された。

記述言語：英語   出版者・発行元：(公社)日本医学放射線学会  

超高精細CT(U-HRCT)による冠動脈CT造影(CCTA)で、モーションアーチファクトに対し、心拍数(HR)が及ぼす影響について検討した。模擬冠動脈が付随した模擬心臓動態ファントムと、CCTA受診患者でU-HRCTと従来のCT(CRCT)画像を比較し、U-HRCT CCTAにおける最適なHRの上限を決定した。安静下およびHRシミュレーション(10bpm間隔で40-90bpm)下で、心臓動態ファントムを両CTで走査し、模擬冠動脈モデルのシャープネスと血管内腔径を定量的に評価した。また、U-HRCTによるCCTAの臨床画像に関しては、視覚評価も行った。その結果、HR≦60bpmではU-HRCTの血管内腔径の誤差はCRCTよりも小さい傾向だったが、HR>60bpmでは逆に大きく、モーションアーチファクトに強く影響されていた。なお、画像シャープネスでは、U-HRCTではCRCTに比べ有意に優れており、視覚評価のスコアでは患者のHRと負に相関した(Spearman r=-0.71、p<0.01)。一方、ROC解析では最終診断が得られなかった画質のHR最適カットオフ値で61bpmが得られ、AUCは0.87、感度95%、特異度71%であった。以上より、HR≦60bpmの場合には、U-HRCTが冠動脈造影ではCRCTよりも診断精度が高く、U-HRCTによるCCTAにより、最適なHRの上限値が約60bpmであることが示唆された。

記述言語：日本語   出版者・発行元：(NPO)日本CT技術学会  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Oral Radiology  

Objectives This study aimed to investigate the impact of a deep learning-based reconstruction (DLR) technique on image quality and reduction of radiation exposure, and to propose a low-dose multidetector-row computed tomography (MDCT) scan protocol for preoperative imaging for dental implant surgery. Methods The PB-1 phantom and a Catphan phantom 600 were scanned using volumetric scanning with a 320-row MDCT scanner. All scans were performed with a tube voltage of 120 kV, and the tube current varied from 120 to 60 to 40 to 30 mA. Images of the mandible were reconstructed using DLR. Additionally, images acquired with the 120-mA protocol were reconstructed using filtered back projection as a reference. Two observers independently graded the image quality of the mandible images using a 4-point scale (4, superior to reference; 1, unacceptable). The system performance function (SPF) was calculated to comprehensively evaluate image quality. The Wilcoxon signed-rank test was employed for statistical analysis, with statistical significance set at p value < 0.05. Results There was no significant difference between the image quality acquired with the 40-mA tube current and reconstructed with the DLR technique (40DLR), and that acquired with the reference protocol (3.00, 3.00, p = 1.00). The SPF at 1.0 cycles/mm acquired with 40DLR was improved by 156.7% compared to that acquired with the reference protocol. Conclusions Our proposed protocol, which achieves a two-thirds reduction in radiation dose, can provide a minimally invasive MDCT scan of acceptable image quality for dental implant surgery.

DOI： 10.1007/s11282-021-00584-w

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：British Journal of Radiology  

Objectives The lung nodule volume determined by CT is used for nodule diagnoses and monitoring tumor responses to therapy. Increased image noise on low-dose CT degrades the measurement accuracy of the lung nodule volume. We compared the volumetric accuracy among deep-learning reconstruction (DLR), model-based iterative reconstruction (MBIR), and hybrid iterative reconstruction (HIR) at an ultra-low-dose setting. Methods Artificial ground-glass nodules (6 mm and 10 mm diameters, −660 HU) placed at the lung-apex and the middle-lung field in chest phantom were scanned by 320-row CT with the ultra-low-dose setting of 6.3 mAs. Each scan data set was reconstructed by DLR, MBIR, and HIR. The volumes of nodules were measured semi-automatically, and the absolute percent volumetric error (APEvol) was calculated. The APEvol provided by each reconstruction were compared by the Tukey-Kramer method. Inter- and intraobserver variabilities were evaluated by a Bland-Altman analysis with limits of agreements. Results DLR provided a lower APEvol compared to MBIR and HIR. The APEvol of DLR (1.36%) was significantly lower than those of the HIR (8.01%, p = 0.0022) and MBIR (7.30%, p = 0.0053) on a 10-mm-diameter middle-lung nodule. DLR showed narrower limits of agreement compared to MBIR and HIR in the inter- and intraobserver agreement of the volumetric measurement. Conclusions DLR showed higher accuracy compared to MBIR and HIR for the volumetric measurement of artificial ground-glass nodules by ultra-low-dose CT. Advances in knowledge DLR with ultra-low-dose setting allows a reduction of dose exposure, maintaining accuracy for the volumetry of lung nodule, especially in patients which deserve a long-term follow-up.

DOI： 10.1259/bjr.20210915

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Purpose In an ultrahigh-resolution CT (U-HRCT), deep learning-based reconstruction (DLR) is expected to drastically reduce image noise without degrading spatial resolution. We assessed a new algorithm's effect on image quality at different radiation doses assuming an abdominal CT protocol. Methods For the normal-sized abdominal models, a Catphan 600 was scanned by U-HRCT with 100%, 50%, and 25% radiation doses. In all acquisitions, DLR was compared to model-based iterative reconstruction (MBIR), filtered back projection (FBP), and hybrid iterative reconstruction (HIR). For the quantitative assessment, we compared image noise, which was defined as the standard deviation of the CT number, and spatial resolution among all reconstruction algorithms. Results Deep learning-based reconstruction yielded lower image noise than FBP and HIR at each radiation dose. DLR yielded higher image noise than MBIR at the 100% and 50% radiation doses (100%, 50%, DLR: 15.4, 16.9 vs MBIR: 10.2, 15.6 Hounsfield units: HU). However, at the 25% radiation dose, the image noise in DLR was lower than that in MBIR (16.7 vs. 26.6 HU). The spatial frequency at 10% of the modulation transfer function (MTF) in DLR was 1.0 cycles/mm, slightly lower than that in MBIR (1.05 cycles/mm) at the 100% radiation dose. Even when the radiation dose decreased, the spatial frequency at 10% of the MTF of DLR did not change significantly (50% and 25% doses, 0.98 and 0.99 cycles/mm, respectively). Conclusion Deep learning-based reconstruction performs more consistently at decreasing dose in abdominal ultrahigh-resolution CT compared to all other commercially available reconstruction algorithms evaluated.

DOI： 10.1002/acm2.13318

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, we investigated the influence of beam hardening on the dual-energy computed tomography (DECT) values of iodine maps, virtual monoenergetic (VME) images, and virtual non-contrast (VNC) images. 320-row DECT imaging was performed by changing the x-ray tube energy for the first and second rotations. DECT values of 5 mg/mL iodine of the multi-energy CT phantom were compared with and without a 2-mm-thick attenuation rubber layer (similar to 700 HU) wound around the phantom. It was found that the CT density values UH, with/without the rubber layer had statistical differences in the iodine map (184 +/- 0.7 versus 186 +/- 1.8), VME images (125 +/- 0.3 versus 110 +/- 0.4), and VNC images (-58 +/- 0.7 versus -76 +/- 1.7) (p < 0.010 for all). This suggests that iodine mapping may be underestimated by DECT and overestimated by VME imaging because of x-ray beam hardening. The use of VNC images instead of plain CT images requires further investigation because of underestimation.

DOI： 10.1186/s41747-021-00217-1

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Purpose: Quantitative evaluations of airway dimensions through computed tomography (CT) have revealed a good correlation with airflow limitation in chronic obstructive pulmonary disease. However, large inaccuracies have been known to occur in CT airway measurements. Ultra-high-resolution CT (UHRCT) might improve measurement accuracy using precise scan modes with minimal focal spot. We assessed the effects of scan mode and focal spot size on airway measurements in UHRCT.Methods: COPDGene. phantom, comprising a plastic tube mimicking human airway of inner diameter 3 mm, wall thickness 0.6 mm, and inclination 30 degrees was scanned at super high resolution (SHR, beam collimation of 0.25 mm x 160 rows) and high resolution (HR, beam collimation of 0.5 mm x 80 rows) modes using UHRCT. Each acquisition was performed both with small (0.4 x 0.5 mm) and large (0.6 x 1.3 mm) focal spots. The wall area percentage (WA%) was calculated as the percentage of total airway area occupied by the airway wall. Statistical analysis was performed to compare the WA% measurement errors for each scan mode and focal spot size.Results: The WA% measurement errors in the SHR mode were 9.8% with a small focal spot and 18.8% with a large one. The measurement errors in the HR mode were 13.3% with a small focal spot and 21.4% with a large one. There were significant differences between each scan mode and focal spot size (p < 0.05).Conclusions: The SHR mode with a small focal spot could improve airway measurement accuracy of UHRCT.

DOI： 10.1016/j.ejmp.2019.12.025

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Objective The aim of the study was to investigate the feasibility of coronary computed tomography (CT) angiography with a low kilovoltage peak scan and a refined scan timing prediction using a small contrast medium (CM) dose. Methods In protocol A, 120-kVp scanning and a standard CM dose were used. The scan timing was fixed. In protocol B, 80 kVp and a 60% CM dose were used. The scan timing was determined according to the interval from the CM arrival to the peak time in the ascending aorta. We measured the CT number and recorded the radiation dose. Results Higher CT numbers were observed in the left circumflex (proximal, P = 0.0235; middle, P = 0.0007; distal, P < 0.0001) in protocol B compared with protocol A. The radiation dose in protocol B was significantly lower than in protocol A (2.2 +/- 0.9 vs 4.3 +/- 1.7 mSv). Conclusions Low-contrast, low-radiation dose, high-image quality coronary CT angiography can be performed with low kilovoltage peak scanning and a refined scan timing prediction.

DOI： 10.1097/RCT.0000000000000951

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Purpose: A 320-row CT scanner can briefly scan the entire heart. Therefore, the feasible scan timing is required. The aim of this study was to propose a refined method for feasible scan timing for coronary CT angiography (CCTA) using a time-density curve of the ascending aorta (AAo).Methods: One-hundred and twenty-nine patients were prospectively enrolled. All patients were performed test bolus method. For the initial 65 patients, the scan timing was determined as a 3.0 s delay at the peak time in the AAo, which was defined as the conventional protocol (COV-P). For the next 64 patients, a scan timing of 1.0, 3.0, or 5.0 s delay was determined according to the interval from the contrast media arrival to peak time in the AAo, which was defined as the arrival to peak protocol (AP-P). The optimal scan timing was identified by the measurement of CT number in the left atrium, left ventricle, AAo, and descending aorta. The coronary enhancement and heterogeneity were compared between the two protocols.Results: The optimal scan timing was significantly higher in the AP-P than in the COV-P (85.9% vs. 61.5%, p = 0.0017). The CT number in the left circumflex artery (LCX) was significantly higher in the AP-P than the COV-P (344.5 Hounsfield units vs. 316.3 Hounsfield units, p = 0.0484). The heterogeneous index of the LCX was significantly greater for the COV-P than the AP-P (-36.8 vs. -25.8, p = 0.0028).Conclusions: The AP-P can be used to determine the optimal scan timing for CCTA and contributes to stable coronary enhancement.

DOI： 10.1016/j.clinimag.2019.01.005

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Introduction: We propose a new dynamic flow imaging using 320-detector row CT, and investigate the assessment of coronary flow in aneurysms of Kawasaki disease in adulthood. Methods: Six patients with Kawasaki disease and coronary aneurysms associated (26.7 years old) and six controls were enrolled. Dynamic coronary CT angiography with 320-row CT was continuously performed at mid-diastole throughout 15-25 cardiac cycles with prospective Electrocardiogram gating after injection of contrast media. Dynamic data sets of 15-25 cycles were computed into 90-100 data sets by motion coherence image processing. Next, time-density curves for coronary arteries were calculated for all the phases. On the basis of the maximum slope method, coronary flow index was defined as the ratio of the maximum upslope of the attenuation of coronary arteries to the upslope of the attenuation of ascending aorta on the time-density curves. Coronary flow indexes for the proximal and distal sites of coronary arteries and intra-aneurysm were measured.

DOI： 10.1017/S1047951117002293

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Objectives: To elucidate the utility of PROPELLER for motion artefact reduction on shoulder MRI and to examine the influence of streak artefacts on diagnosis of clinical images.Methods: 15 healthy volunteers and 48 patients underwent shoulder MRI with/without PROPELLER (coronal oblique proton density-fast spin echo [PD-FSE], sagittal oblique T2-FSE). In a volunteer study, all sequences were performed in both static and exercise-loaded conditions. Two radiologists graded artefacts and delineation of various anatomical structures in the volunteer study and motion and streak artefacts in the clinical study. Mean scores were compared between sequences with/without PROPELLER. In the clinical study, mean scores of motion artefacts were compared with mean scores of streak artefacts. Wilcoxon signed-rank test was used for all comparisons.Results: In both studies, PROPELLER significantly reduced motion artefacts (P < 0.05). In the volunteer study, it significantly improved delineations in sagittal oblique images in the exercise-loaded condition (13 < 0.05). In the clinical study, streak artefacts appeared dominantly on images with PROPELLER (13 < 0.05), but influenced diagnosis to a lesser extent than motion artefacts.Conclusion: PROPELLER can reduce motion artefacts in shoulder MRI. While it does cause streak artefacts, it affects diagnosis to a lesser extent. (C) 2016 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.ejrad.2016.07.008

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Purpose: To compare hybrid iterative reconstruction (HIR) with filtered back projection (FBP) in the volumetry of artificial pure ground-glass nodules (GGNs) with low-dose computed tomography (CT).Materials and methods: Artificial GGNs (10 mm-diameter, 523.6 mm3, 660 HU) in an anthropomorphic chest phantom were scanned by a 256-row multi-slice CT with three dose levels (10, 30, 100 mAs). Each scan was repeated six times. Each set was reconstructed by FBP and HIR at 0.625-mm thickness. The volumes of artificial GGNs placed at the lung apex and middle lung field of the chest phantom were measured by two observers. Semi-automated measurements were performed by clicking the cursor in the center of GGNs, and manual measurements were performed by tracing GGNs on axial section. Modification of the trace was added on a sagittal or coronal section if necessary. Measurement errors were calculated for both the FBP and HIR at each dose level. We used the Wilcoxon signed rank test to identify any significant difference between the measurement errors of the FBP and HIR. Inter-observer, intraobserver, and inter-scan variabilities were evaluated by Bland Altman analysis with limits of agreements given by 95% confidence intervals.Results: There were significant differences in measurement errors only at the lung apex between FBP and HIR with 10 mAs in both the semi-automated (observer 1, 37% vs. 7.2%; observer 2, 39% vs. 1.9%) and manual methods (observer 1, 29% vs. 7.5%; observer 2, 30% vs. 1.1%), respectively (P< 0.05). HIR provided each variability equal to or less than one half of that of FBP at 10 mAs in both methods. In the semi-automated method, the inter-observer and intra-observer variabilities obtained by HIR at 10 mAs were 11% to 17% and 6.7% to 6.7%, whereas those for FBP at 10 mAs were 29% to 30% and 38% to 20%, respectively. The inter-scan variability for FBP at 100 mAs vs. HIR at 10 mAs was 9.5% to 11%, and that for FBP at 100 mAs vs. FBP at 10 mAs was 73% to 32%. In the manual method, the inter-observer and intra-observer variabilities for HIR at 10 mAs were 14% to 22% and 9.8% to 22%, and those for FBP at 10 mAs were 45% to 36% and 31% to 28%, respectively. The inter-scan variability for FBP at 100 mAs vs. HIR at 10 mAs was 7.4% to 23%, and that for FBP at 100 mAs vs. FBP at 10 mAs was 52% to 26%.Conclusion: HIR is superior to FBP in the volumetry of artificial pure GGNs at lung apex with low-dose CT. (C) 2015 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.ejrad.2015.08.018

記述言語：英語   掲載種別：研究論文（学術雑誌）  

OBJECTIVE: To evaluate the confidence ratings of diagnoses of simulated lesions other than lung cancer on low-dose screening CT with hybrid iterative reconstruction (IR). METHODS: Simulated lesions (emphysema, mediastinal masses and interstitial pneumonia) in a chest phantom were scanned by a 320-row area detector CT. The scans were performed by 64-row and 160-row helical scans at various dose levels and were reconstructed by filtered back projection (FBP) and IR. Emphysema, honeycombing and reticular opacity were visually scored on a four-point scale by six thoracic radiologists. The ground-glass opacity as a percentage of total lung volume (%GGO), CT value and contrast-to-noise ratio (CNR) of mediastinal masses were calculated. These scores and values were compared between FBP and IR. Wilcoxon's signed-rank test was used (p < 0.05). Interobserver agreements were evaluated by κ statistics. RESULTS: There were no significant differences in visual assessment. Interobserver agreement was almost perfect. CT values were almost equivalent between FBP and IR, whereas CNR with IR was significantly higher than that with FBP. %GGO significantly increased at low-dose levels with FBP; however, IR suppressed the elevation. CONCLUSION: The confidence ratings of diagnoses of simulated lesions other than lung cancer on low-dose CT screening were not degraded with hybrid IR compared with FBP. ADVANCES IN KNOWLEDGE: Hybrid IR did not degrade the confidence ratings of diagnoses on visual assessment and differential diagnoses based on CT value of mediastinal masses, and it showed the advantage of higher GGO conspicuity at low-dose level. Radiologists can analyse images of hybrid IR alone on low-dose CT screening for lung cancer.

DOI： 10.1259/bjr.20150159

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逐次近似応用再構成がCT During Hepatic Arteriographyの血管描出能に及ぼす影響

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冠動脈CTにおける動き補正技術を用いた血管形状の正確性 Phantom Study

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