片岡 由美

OBJECTIVES: Evaluation of in-stent restenosis (ISR), especially for small stents, remains challenging during computed tomography (CT) angiography. We used deep learning reconstruction to quantify stent strut thickness and lumen vessel diameter at the stent and compared it with values obtained using conventional reconstruction strategies. METHODS: We examined 166 stents in 85 consecutive patients who underwent CT and invasive coronary angiography (ICA) within 3 months of each other from 2019-2021 after percutaneous coronary intervention with coronary stent placement. The presence of ISR was defined as percent diameter stenosis ≥ 50% on ICA. We compared a super-resolution deep learning reconstruction, Precise IQ Engine (PIQE), and a model-based iterative reconstruction, Forward projected model-based Iterative Reconstruction SoluTion (FIRST). All images were reconstructed using PIQE and FIRST and assessed by two blinded cardiovascular radiographers. RESULTS: PIQE had a larger full width at half maximum of the lumen and smaller strut than FIRST. The image quality score in PIQE was higher than that in FIRST (4.2 ± 1.1 versus 2.7 ± 1.2, p < 0.05). In addition, the specificity and accuracy of ISR detection were better in PIQE than in FIRST (p < 0.05 for both), with particularly pronounced differences for stent diameters < 3.0 mm. CONCLUSION: PIQE provides superior image quality and diagnostic accuracy for ISR, even with stents measuring < 3.0 mm in diameter. CLINICAL RELEVANCE STATEMENT: With improvements in the diagnostic accuracy of in-stent stenosis, CT angiography could become a gatekeeper for ICA in post-stenting cases, obviating ICA in many patients after recent stenting with infrequent ISR and allowing non-invasive ISR detection in the late phase. KEY POINTS: • Despite CT technology advancements, evaluating in-stent stenosis severity, especially in small-diameter stents, remains challenging. • Compared with conventional methods, the Precise IQ Engine uses deep learning to improve spatial resolution. • Improved diagnostic accuracy of CT angiography helps avoid invasive coronary angiography after coronary artery stenting.

OBJECTIVE: Ultra-high-resolution CT (UHR-CT), which can be applied normal resolution (NR), high-resolution (HR), and super-high-resolution (SHR) modes, has become available as in conjunction with multi-detector CT (MDCT). Moreover, deep learning reconstruction (DLR) method, as well as filtered back projection (FBP), hybrid-type iterative reconstruction (IR), and model-based IR methods, has been clinically used. The purpose of this study was to directly compare lung CT number and airway dimension evaluation capabilities of UHR-CT using different scan modes with those of MDCT with different reconstruction methods as investigated in a lung density and airway phantom design recommended by QIBA. MATERIALS AND METHODS: Lung CT number, inner diameter (ID), inner area (IA), and wall thickness (WT) were measured, and mean differences between measured CT number, ID, IA, WT, and standard reference were compared by means of Tukey's HSD test between all UHR-CT data and MDCT reconstructed with FBP as 1.0-mm section thickness. RESULTS: For each reconstruction method, mean differences in lung CT numbers and all airway parameters on 0.5-mm and 1-mm section thickness CTs obtained with SHR and HR modes showed significant differences with those obtained with the NR mode on UHR-CT and MDCT (p < 0.05). Moreover, the mean differences on all UHR-CTs obtained with SHR, HR, or NR modes were significantly different from those of 1.0-mm section thickness MDCTs reconstructed with FBP (p < 0.05). CONCLUSION: Scan modes and reconstruction methods used for UHR-CT were found to significantly affect lung CT number and airway dimension evaluations as did reconstruction methods used for MDCT. KEY POINTS: • Scan and reconstruction methods used for UHR-CT showed significantly higher CT numbers and smaller airway dimension evaluations as did those for MDCT in a QIBA phantom study (p < 0.05). • Mean differences in lung CT number for 0.25-mm, 0.5-mm, and 1.0-mm section thickness CT images obtained with SHR and HR modes were significantly larger than those for CT images at 1.0-mm section thickness obtained with MDCT and reconstructed with FBP (p < 0.05). • Mean differences in inner diameter (ID), inner area (IA), and wall thickness (WT) measured with SHR and HR modes on 0.5- and 1.0-mm section thickness CT images were significantly smaller than those obtained with NR mode on UHR-CT and MDCT (p < 0.05).

OBJECTIVE: Some patients with cleft palate (CP) need secondary surgery to improve functionality. Although 4-dimensional assessment of velopharyngeal closure function (VPF) in patients with CP using computed tomography (CT) has been existed, the knowledge about quantitative evaluation and radiation exposure dose is limited. We performed a qualitative and quantitative assessment of VPF using CT and estimated the exposure doses. DESIGN: Cross-sectional. SETTING: Computed tomography images from 5 preoperative patients with submucous CP (SMCP) and 10 postoperative patients with a history of CP (8 boys and 7 girls, aged 4-7 years) were evaluated. PATIENTS: Five patients had undergone primary surgery for SMCP; 10 received secondary surgery for hypernasality. MAIN OUTCOME MEASURES: The presence of velopharyngeal insufficiency (VPI), patterns of velopharyngeal closure (VPC), and cross-sectional area (CSA) of VPI was evaluated via CT findings. Organ-absorbed radiation doses were estimated in 5 of 15 patients. The differences between cleft type and VPI, VPC patterns, and CSA of VPI were evaluated. RESULTS: All patients had VPI. The VPC patterns (SMCP/CP) were evaluated as coronal (1/4), sagittal (0/1), circular (1/2), and circular with Passavant's ridge (2/2); 2 patients (1/1) were unevaluable because of poor VPF. The CSA of VPI was statistically larger in the SMCP group (P = .0027). The organ-absorbed radiation doses were relatively lower than those previously reported. CONCLUSIONS: Four-dimensional CT can provide the detailed findings of VPF that are not possible with conventional CT, and the exposure dose was considered medically acceptable.

BACKGROUND: Contrast media agents are essential for computed tomography (CT)-based diagnoses. However, they can cause fatal adverse effects such as anaphylaxis in patients. Although it is rare, the chances of anaphylaxis increase with the number of examinations. OBJECTIVE: We aimed to design a quality improvement initiative to reduce patient risk to contrast media agents. METHODS: We analysed CT processes using contrast iodine in a tertiary-care academic hospital that performs approximately 14 000 CT scans per year in Japan. We applied a combination of failure modes and effects analysis (FMEA) and cause-effect analysis to reduce the risk of patients developing allergic reactions to iodine-based contrast agents during CT imaging. RESULTS: Our multidisciplinary team comprising seven professionals analysed the data and designed a 56-process flowchart of CT imaging with iodine. We obtained 177 failure modes, of which 15 had a risk-probability number higher than 100. We identified the two riskiest processes and developed cause-and-effect diagrams for both: one was related to the exchange of information between the radiation and hospital information system regarding the patient's allergy, the other was due to education and structural deficiencies in observation following the exam. CONCLUSION: The combined method of FMEA and cause-and-effect analysis reveals high-risk processes and suggests measures to reduce these risks. FMEA is not well-known in healthcare but has significant potential for improving patient safety. Our findings emphasise the importance of adopting new techniques to reduce patient risk and carry out best practices in radiology.

Abstract BackgroundThe aims of this study were to perform a four-dimensional assessment of velopharyngeal closure function in pediatric patients with cleft palate using 320-row area detector computed tomography (CT), and to estimate the organ-absorbed doses using Monte Carlo simulation.MethodsWe evaluated CT image data obtained between July 2018 and August 2019 from five pediatric patients with cleft palate (four boys and one girl; age range, 4–7 years) at Fujita Health University Hospital. The presence of velopharyngeal insufficiency (VPI), patterns of velopharyngeal closure (VPC), and cross-sectional area of VPI were evaluated. In addition, organ-absorbed doses were assumed in the Monte Carlo simulation. However, we did not perform statistical analysis because of the insufficient number of patients enrolled in this study.ResultsThe existence of VPI and hypernasality were completely concordant. The VPC patterns were circular (two patients), circular with Passavant’s ridge (one patient), and unevaluable (two patients). The organ-absorbed doses were relatively lower than those in past reports.ConclusionsOur method could be an alternative for patients who refuse the conventional nasopharyngoscopic evaluation.

OBJECTIVES: Renal scintigraphy is widely used to evaluate residual function of a transplanted kidney from the donor. Dynamic computed tomography (CT) imaging can evaluate both kidney morphology and regional renal function. The aim of this study was to develop an imaging protocol and a calculation method using dynamic CT for assessing the effective renal plasma flow (ERPF) by model analysis, and to evaluate the validity of the obtained ERPF values. METHODS: Preoperative dynamic CT examination with a low radiation dose exposure system was performed for 25 renal transplant donors, and ERPF was calculated from the obtained images (CT-ERPF). To calculate CT-ERPF, we set the region of interest (ROI) in the renal cortex using automatic ROI-setting software developed in our laboratory. We compared the processing time with automatic and manual ROI settings. To evaluate the validity of CT-ERPF, we examined the correlation of age with CT-ERPF and compared with reported ERPF values. We also compared the uptake rates of technetium-99m-dimercaptosuccinic acid and CT-ERPF in terms of the right-to-left ratio. RESULTS: There was good agreement of CT-ERPF assessed using automatic and manual ROIs. CT-ERPF was negatively correlated with age and showed values below the reference ERPF range in 21 cases. The right-to-left ratio of CT-ERPF showed a significant correlation with that of technetium-99m-dimercaptosuccinic acid. CONCLUSIONS: Using our method, CT-ERPF was a useful indicator for preoperative evaluation of donor's renal function.

BACKGROUND: Nasopharyngoscopy is a common method to evaluate velopharyngeal closure in patients with cleft palate. However, insertion of a fiberoptic nasopharyngoscope causes discomfort in patients. The aim of this study was to estimate the reliability of short-time exposure images obtained using 320-row area detector computed tomography (320-ADCT) as a novel evaluation method for the assessment of velopharyngeal function. METHODS: We evaluated five healthy adult volunteers and five postoperative adult patients with cleft palate. During a 3.3-s imaging exposure, the participants were asked to perform two tasks: nasal inspiration and subsequent oral expiration through a catheter into a water-filled cup. The movement of the velopharyngeal structures was recorded during each examination, and the presence of velopharyngeal insufficiency (VPI) and velopharyngeal closure (VPC) patterns were estimated. If VPI was detected, the cross-sectional area was also calculated. Cohen's kappa and weighted kappa coefficients were used to evaluate the concordance of nasopharyngoscopy and 320-ADCT evaluation. RESULTS: Speech pathology evaluation did not reveal hypernasality in any study participant. Micro-VPI was detected by nasopharyngoscopy in one healthy volunteer and two patients. 320-ADCT detected micro-VPI in two more patients. The cross-sectional area of the VPI in these subjects ranged from 2.53 to 16.28 mm2. Nasopharyngoscopy and 320-ADCT were concordant in detecting VPI in eight participants (κ = 0.6) and in assessing VPC patterns in nine (κ = 0.82). Moreover, images obtained using 320-ADCT allowed for reduced dead angle and, thus, easy detection of micro-VPI and Passavant's ridges. CONCLUSION: Although the radiation exposure cannot be ignored, our novel evaluation method using 320-ADCT enables more detailed evaluation of VPC than nasopharyngoscopy. Future studies should investigate the relationship between 320-ADCT findings and speech pathology evaluations.

BACKGROUND: Limitations of coronary computed tomography (CTA) include false-positive stenosis at calcified lesions and assessment of in-stent patency. A prototype of ultra-high resolution computed tomography (U-HRCT: 1,792 channels and 0.25-mm slice thickness×128 rows) with improved spatial resolution was developed. We assessed the diagnostic accuracy of coronary artery stenosis using U-HRCT.Methods and Results:Seventy-nine consecutive patients who underwent CTA using U-HRCT were prospectively included. Coronary artery stenosis was graded from 0 (no plaque) to 5 (occlusion). Stenosis grading at 102 calcified lesions was compared between U-HRCT and conventional-resolution CT (CRCT: 896 channels and 0.5-mm slice thickness×320 rows). Median stenosis grading at calcified plaque was significantly improved on U-HRCT compared with CRCT (1; IQR, 1-2 vs. 2; IQR, 1-3, P<0.0001). Assessability of in-stent lumen was evaluated on U-HRCT in 79 stents. Stent strut thickness and luminal diameter were quantitatively compared between U-HRCT and CRCT. Of 79 stents, 83.5% were assessable on U-HRCT; 80% of stents with diameter 2.5 mm were regarded as assessable. On U-HRCT, stent struts were significantly thinner (median, 0.78 mm; IQR, 0.7-0.83 mm vs. 0.83 mm; IQR, 0.75-0.92 mm, P=0.0036), and in-stent lumens were significantly larger (median, 2.08 mm; IQR, 1.55-2.51 mm vs. 1.74 mm; IQR, 1.31-2.06 mm, P<0.0001) than on CRCT. CONCLUSIONS: U-HRCT with improved spatial resolution visualized calcified lesions with fewer artifacts. The in-stent lumen of stents with diameter ≥2.5 mm was assessable on U-HRCT.

Purpose: We measured the computed tomography (CT) dose profile with CT dose phantom for several X‐ray beam widths on 64‐slice, and 320‐slice multi detector‐row CT (MDCT) using micro ionization chamber, and assessed the association of the CTDI100 value with CT dose phantom length. Methods: The CT dose profile (CTDP) was measured as Dm using radiation monitor (Model 9015, Radcal, Monrovia, CA) with micro ionization chamber (10X5‐0.18, Radcal, Monrovia, CA) which have an active length of 19 mm and a 0.18 cm3 active area on 64‐slice MDCT (Aquilion CX, Toshiba Medical Systems, Tochigi, Japan), and 320‐slice MDCT (Aquilion One, Toshiba Medical Systems, Tochigi, Japan). The MDCT systems were used with a tube voltage of 120 kV, tube current of 100 mA, rotation time of 1 second, and nominal X‐ray beam widths of 4, 12, 32, and 160 mm (4*1 mm, 4*3 mm, 64*0.5 mm, and 320*0.5 mm axial slice acquisitions, respectively). A micro ionization chamber was placed in the center of the single CT dose phantom, and we acquired several axial scans as 5 mm increments of phantom length. Then two, and three coupled dose phantom were placed together to simulate a 300‐mm‐long, and 450‐mm‐long phantom. We acquired several axial scans in similar method. Results: The observed percent increase of the Dm with extended length from 150 mm to 300 mm of the CT dose phantom was 120 % at range from −60 to 60 mm. However, it was greatly increased toward peripheral area of the DP. With extended length from 300 mm to 450 mm of CT dose phantom, the observed percent increase of the Dm was slightly increased. There was no difference in the form of the CTDP between 300‐mm‐long phantom and 450‐mm‐long phantom. Conclusion: In upward of the 300‐mm‐long CT dose phantom, there is no difference in the form of the CTDP. © 2013, American Association of Physicists in Medicine. All rights reserved.

X線CTを利用した冠動脈CT検査(Coronary CTA)が広く行われるようになった。本研究では、本大学病院のCoronary CTA検査で患者の受ける線量を2006年から2012年までの推移を評価した。CT装置は64列から320列に変更も行われた。線量評価は撮影条件変更ごとのプロトコールにしたがった。線量測定には人体等価ファントムを用いて表面体内の線量を測定した。各部位の吸収線量から、全肺線量と、最適な造影濃度で撮影するために経時的に同一部位で撮影を行うボーラストラッキング(リアルプレップ)の断面線量をそれぞれ求めた。さらに、現在行われている撮影条件から実効線量を算出した。その結果、64列CTでは2006年から2007年までに全肺線量は45%、プレップ断面の線量は40%に低減した。320列CTでは2008年から2012までに、それぞれ57%、58%に低減した。2006年から2012年までは全肺で16%、プレップ断面で10%に低減した。現在のCoronary CTAでの実効線量は、8.26mSvであった。(著者抄録)

健常成人10名(平均45歳)、右延髄梗塞に伴う球麻痺患者1名(62歳女)を対象に、320列面検出器型CTによる嚥下機能評価および臨床応用について検討した。正常嚥下動態については、MPR像と3D-CTのvolume rendering(VR)像で嚥下諸器官の動態を明瞭に描出できた。特に声帯閉鎖を明瞭に描出でき、嚥下中の喉頭閉鎖の3事象(喉頭前庭閉鎖・声帯閉鎖・喉頭蓋反転)を同時に正確に計測可能であった。嚥下障害動態については、VR像で造影剤の健側のみの通過と、嚥下障害の症状である咽頭残留を明瞭に描出できた。更に、咽頭残留の原因として、食塊が食道入口部を通過する段階で、麻痺側の咽頭収縮不全(咽頭腔が消失せずに残存)と食道入口部開大不全の病態を明瞭に確認できた。また、残留の位置が左梨状窩と右喉頭蓋谷であることを正確に特定できた。

320列area detector CT用いることで、肺血管走行把握目的の肺動静脈分離画像が簡便に得られる撮影タイミング・造影法を考案した。肺腫瘍の肺葉切除予定患者46例を対象とした。内腔CT値差が他の時相と比較して50HU以上を分離良好とした場合、肺動脈の分離は100%、肺静脈の分離は59%、大動脈の分離は97%であった。肺血管走行把握を目的としたVR画像作成は、32例中29例で10分以内で完了した。分離が容易ではなかった症例は、いずれも肺動脈のCT値が肺静脈相や大動脈相でも低下がとぼしい症例で、疾患としては、慢性心房細動2例、心房中隔欠損1例が含まれていたが、その他は明らかでなかった。

現在、臨床で使用されているCT装置での頭部CT検査、腹部CT検査での線量を2005年5月～12月、50施設60装置で評価した。線量評価は国際電気標準会議で示されているCTDIvolとした。使用した線量測定器は国家標準で校正された電離箱型CT用線量計、ファントムは、アクリル製円柱形を使用した。頭部は直径16cm、腹部は直径32cmのPMMAファントムを使用した。頭部CT検査時のCTDIvolでは、平均62.48mGy、腹部CT検査時のCTDIvolでは、平均16.76mGyであった。施設間格差は頭部、腹部とも8-10倍であった。メーカによる線量差は、2倍程度であった。MDCT装置の列数による線量差は8列が最も大きくなっていたが、多列化と線量増加の間には相関は認めなかった。

生殖腺が線束内に含まれない頭部、胸部、腹部(肝臓)の一般的なCT検査における生殖腺線量を測定した。加えて、臨床で使用されている防護エプロンによる生殖腺線量の低減効果を検討した。得られたデータと国際放射線防護委員会(ICRP)のデータ比較、リスク評価も試みた。マルチスライスCTを使用した通常のX線CT検査において、生殖腺が含まれない散乱線線量は、頭部で0.01mGyから、腹部(肝)で1mGy程度であった。散乱線線量は制御可能であり、防護によって生殖腺線量を20～30%低減できることが示唆された。

臨床現場で汎用性のある低減目標値を評価する方法を検討した.X線CT検査の低減目標値は,1998年に測定を行った中部地区に稼動中のCT装置38台の結果を参考にした.提案した低減目標値は,PMMAファントム中の空気吸収線量で頭部59mGy(16cmφ),腹部23mGy(32cmφ)で,現行の低減目標値より頭部で1.45倍,腹部で2.06倍であった.提案した低減目標値は,オペレータコンソールと比較を行うことができるため有用であることが示唆された

PMMA(polymethylmethacrylate)ファントム中心のCTDI(CT dose index)100,c,上下左右の表面下10mmにおけるCTDIを平均したCTDI100,pおよびHVL(half-value layer)を推定し,CTDIvol(CTDI volum)をPMMAファントム中における空気吸収線量および物質(PMMA)の吸収線量で評価する方法の検討を行った.測定が困難なHVLも推定することが可能であった.HVLを推定できるため,f-factorを用いて物質の吸収線量の評価が可能である.X線CT用電離箱のみ所有していれば,X線CTの線量評価を行うことができるため,より多くの施設がX線CT検査の被爆線量を把握するための手段として有用であると考えられた

平成14年4月よりCT-perfusion検査が施行され,超急性期脳梗塞の診断・治療方針決定,術後の脳血流の診断に利用されているが,導入当初,解析処理時間,局所の被ばく線量に問題があった.そこで解析ソフトウエアの改良とスキャン方式の変更により短時間処理,低被ばく線量化の検討をした.新ソフトウエアでは解析手順が簡略化されたため,平均10分かかっていたのが,5分以内の時間短縮となった.脳梗塞の疑い2例,クモ膜下出血の手術後7～10日目4例のfunctional mapの定量値CBPにおいて,新・旧解析ソフトウエアは高い相関を示した.新しいスキャンパラメータの線量を装置表示のCTDIw,DLPで評価したところ,従来と比較し,約45%にまでの減少が可能となった.個々の解析mapは,臨床診断上問題となる結果はなかった.低線量化によりmapのノイズが目立つが,解析パラメータのノイズ除去レベルを変更することで解決できた

マルチスライスCT(MSCT)における可変管電流制御システム(Real-EC)を使用し,最も被ばく低減が期待できる胸部について,被ばく線量低減効果を国際放射線防護委員会(ICRP)が提唱しているCT線量評価Dose-length product(DLP),人体等価ファントムを用いて検討した.MSCTの導入で,広範囲短時間撮影が可能となった.シングルスライスヘリカルCT(SSCT)比較して,被爆線量は増加したが,Real-ECにより,画質を維持しつつSSCTよりも患者被爆の低減が可能となり,有用性が示唆された