Coronary computed tomography angiographic detection of in-stent restenosis via deep learning reconstruction: a feasibility study.

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.

Comparison of lung CT number and airway dimension evaluation capabilities of ultra-high-resolution CT, using different scan modes and reconstruction methods including deep learning reconstruction, with those of multi-detector CT in a QIBA phantom study.

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).

Combining failure modes and effects analysis and cause-effect analysis: a novel method of risk analysis to reduce anaphylaxis due to contrast media.

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.

Evaluation of Velopharyngeal Closure Function With 4-Dimensional Computed Tomography and Assessment of Radiation Exposure in Pediatric Patients: A Cross-Sectional Study.

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.

Measurement of effective renal plasma flow using model analysis of dynamic CT in the preoperative evaluation of the renal transplant donors.

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.

Velopharyngeal closure analysis using four-dimensional computed tomography: a pilot study of healthy volunteers and adult patients with cleft palate.

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.

Ultra-High-Resolution Computed Tomography Angiography for Assessment of Coronary Artery Stenosis.

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.

[Development of a Striatal and Skull Phantom for Quantitative 123I-FP-CIT SPECT].

BACKGROUND: 123Iodine-labelled N-(3-fluoropropyl) -2ß-carbomethoxy-3ß-(4-iodophenyl) nortropane (123I-FP-CIT) single photon emission computerized tomography (SPECT) images are used for differential diagnosis such as Parkinson's disease (PD). Specific binding ratio (SBR) is affected by scattering and attenuation in SPECT imaging, because gender and age lead to changes in skull density. It is necessary to clarify and correct the influence of the phantom simulating the the skull. PURPOSE: The purpose of this study was to develop phantoms that can evaluate scattering and attenuation correction. METHODS: Skull phantoms were prepared based on the measuring the results of the average computed tomography (CT) value, average skull thickness of 12 males and 16 females. 123I-FP-CIT SPECT imaging of striatal phantom was performed with these skull phantoms, which reproduced normal and PD. SPECT images, were reconstructed with scattering and attenuation correction. SBR with partial volume effect corrected (SBRact) and conventional SBR (SBRBolt) were measured and compared. RESULTS: The striatum and the skull phantoms along with 123I-FP-CIT were able to reproduce the normal accumulation and disease state of PD and further those reproduced the influence of skull density on SPECT imaging. The error rate with the true SBR, SBRact was much smaller than SBRBolt. CONCLUSION: The effect on SBR could be corrected by scattering and attenuation correction even if the skull density changes with 123I-FP-CIT on SPECT imaging. The combination of triple energy window method and CT-attenuation correction method would be the best correction method for SBRact.

[Dose estimation with CTDI100, air in computed tomography].

Although the principal dosimetric quantity in computed tomography (CT) can be assessed using a pencil ionization chamber with an active length of 100 mm, standard CT dosimetry phantoms of polymethylmethacrylate (PMMA) , and plates of aluminum, most facilities do not possess the requisites. We present a practical method of estimating CTDI(100, c), CTDI(100, p) and the half-value layer (HVL) from CTDI(100, air), which is measured parallel with the axis of rotation of the scanner to free-in-air. The three data chosen for this method of estimation were as follows: 1) the relation of HVL to CTDI(100, air) per radiographic exposure (mAs); 2) the relation of HVL to CTDI(100, c) per CTDI(100, air); 3) the relation of HVL to CTDI(100, p) per CTDI(100, air). The data were based on the measured values of six CT scanners, so as to avoid dependence on the technical characteristics of a specific manufacturer. The estimated value has a possible maximum uncertainty of 20%, although this method of estimation is practical for dose assessment.

[The improvement in the cerebral blood flow analysis software in case of CT-perfusion inspection and the examination of the scan protocol].

In our hospital, CT-perfusion was introduced in April, 2002. It is used to diagnose, to determine what treatment to use and to prognosticate cerebral blood flow after operation in super acute period brain infarct. At the beginning of the introduction, processing time and dosage for partial areas needed improvement. Therefore, we investigated the possibility of shorter processing time and lower dosage of radiation with the help of improvement in the analysis software as well as a different scan method. Two methods of reducing radiation dosage were examined. (1) The speed of X-ray rotation was slowed down; while photon per image was maintained, total mAs was lowered. (2) Continuation scan was replaced by intermission one. Analyzing time with older and newer version of analysis software was compared. The dosage was able to decrease by 25% as a result of the rotation speed slowed down; it became further less by 50% with the intermission scan. Processing such as the vein extraction was automated by using new analysis software and successfully shorten the analysing time without damaging the reliability of analyses. We forecast that more clinical research on further lowering dosage and stabilization of analyzing will enable us to provide better information.