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Myocardial ischemia is caused by a mismatch between myocardial oxygen consumption and oxygen delivery in coronary artery disease (CAD). Stratification and decision-making based on ischemia improves the prognosis in patients with CAD. Non-invasive tests used to evaluate myocardial ischemia include stress electrocardiography, echocardiography, single-photon emission computed tomography, and magnetic resonance imaging. Invasive fractional flow reserve is considered the reference standard for assessment of the hemodynamic significance of CAD. Computed tomography (CT) angiography has emerged as a first-line imaging modality for evaluation of CAD, particularly in the population at low to intermediate risk, because of its high negative predictive value; however, CT angiography does not provide information on the hemodynamic significance of stenosis, which lowers its specificity. Emerging techniques, e.g., CT perfusion and CT-fractional flow reserve, help to address this limitation of CT, by determining the hemodynamic significance of coronary artery stenosis. CT perfusion involves acquisition during the first pass of contrast medium through the myocardium following pharmacological stress. CT-fractional flow reserve uses computational fluid dynamics to model coronary flow, pressure, and resistance. In this article, we review these two functional CT techniques in the evaluation of myocardial ischemia, including their principles, technology, advantages, limitations, pitfalls, and the current evidence.

Cardiovascular cine magnetic resonance (CMR) accelerated by compressed sensing (CS) is used to assess left ventricular (LV) function. However, it is difficult for prospective CS cine CMR to capture the complete end-diastolic phase, which can lead to underestimation of the end-diastolic volume (EDV), stroke volume (SV), and ejection fraction (EF), compared to retrospective standard cine CMR. This prospective study aimed to evaluate the diagnostic quality and accuracy of single-breath-hold full cardiac cycle CS cine CMR, acquired over two heart beats, to quantify LV volume in comparison to multi-breath-hold standard cine CMR. Eighty-one participants underwent standard segmented breath-hold cine and CS real-time cine CMR examinations to obtain a stack of eight contiguous short-axis images with same high spatial (1.7 × 1.7 mm2) and temporal resolution (41 ms). Two radiologists independently performed qualitative analysis of image quality (score, 1 [i.e., “nondiagnostic”] to 5 [i.e., “excellent”]) and quantitative analysis of the LV volume measurements. The total examination time was 113 ± 7 s for standard cine CMR and 24 ± 4 s for CS cine CMR (p < 0.0001). The CS cine image quality was slightly lower than standard cine (4.8 ± 0.5 for standard vs. 4.4 ± 0.5 for CS; p < 0.0001). However, all image quality scores for CS cine were above 4 (i.e., good). No significant differences existed between standard and CS cine MR for all quantitative LV measurements. The mean differences with 95 % confidence interval (CI), based on Bland–Altman analysis, were 1.3 mL (95 % CI, −14.6 – 17.2) for LV end-diastolic volume, 0.2 mL (95 % CI, −9.8 to10.3) for LV end-systolic volume, 1.1 mL (95 % CI, −10.5 to 12.7) for LV stroke volume, 1.0 g (95 % CI, −11.2 to 13.3) for LV mass, and 0.4 % (95 % CI, −4.8 – 5.6) for LV ejection fraction. The interobserver and intraobserver variability for CS cine MR ranged from −4.8 – 1.6 % and from −7.3 – 9.3 %, respectively, with slopes of the regressions ranging 0.88–1.0 and 0.86–1.03, respectively. Single-breath-hold full cardiac cycle CS real-time cine CMR could evaluate LV volume with excellent accuracy. It may replace multi-breath-hold standard cine CMR.

BackgroundTo evaluate the treatment outcomes of external-beam radiotherapy (EBRT) with or without radioactive iodine therapy (RAIT) for metastatic or recurrent lesions of differentiated thyroid cancer (DTC).MethodsBetween August 1997 and March 2018, 73 lesions (distant metastases, 50; regional lymph-node metastases, 17; postoperative tumor-bed recurrences, 6) in 36 patients that had received EBRT with or without RAIT were reviewed. Doses of EBRT were 8–70 Gy (median 40 Gy). Seventeen patients received RAIT after EBRT.ResultsMedian follow-up time of imaging studies was 14 months (range 1–110 months). Two-year overall survival rates and control rates of EBRT sites were 71% and 62%, respectively. Two-year control rates for EBRT of < 30 Gy (n = 7), 30 Gy (n = 13), 31–49 Gy (n = 25), 50 Gy (n = 20), and > 50 Gy (n = 8) were 0%, 56%, 53%, 79%, and 100%, respectively. There were statistically significant differences in control rates between < 30 Gy and 30 Gy (p = 0.003), and between 50 Gy and > 50 Gy (p = 0.037). Control rates of > 50 Gy were significantly better compared to ≤ 50 Gy (p = 0.021). Two-year control rates with (n = 28) and without (n = 45) post-EBRT RAIT were 89% and 45%, respectively (p = 0.009). In multivariate analysis, EBRT of > 50 Gy and post-EBRT RAIT were significant independent factors for favorable control of EBRT sites (hazard ratio [HR], 5.72; 95% confidence interval [CI], 1.21–27.1; p = 0.028 and HR, 2.98; 95% CI, 1.28–6.98; p = 0.012, respectively).ConclusionEBRT of > 50 Gy and post-EBRT RAIT appeared to be useful for long-term control of EBRT sites for metastatic or recurrent lesions of DTC.

PurposeTo evaluate the image quality and lesion visibility of virtual monoenergetic images (VMIs) reconstructed using a new monoenergetic reconstruction algorithm (nMERA) for evaluation of breast cancer.Materials and methodsForty-two patients with 46 breast cancers who underwent 4-phasic breast contrast-enhanced computed tomography (CT) using dual-energy CT (DECT) were enrolled. We selected the peak enhancement phase of the lesion in each patient. The selected phase images were generated by 120-kVp-equivalent linear blended (M120) and monoenergetic reconstructions from 40 to 80 keV using the standard reconstruction algorithm (sMERA: 40, 50, 60, 70, 80) and nMERA (40 +, 50 +, 60 +, 70 +, 80 +). The contrast-to-noise ratio (CNR) was calculated and objectively analyzed. Two independent readers subjectively scored tumor visibility and image quality each on a 5-point scale.ResultsThe CNR at 40 + and tumor visibility scores at 40 + and 50 + were significantly higher than those on M120. The CNR at 50 + was not significantly different from that on M120. However, the overall image quality score at 40 + was significantly lower than that at 50 + and on M120 (40 + vs M120, P < 0.0001 and 40 + vs 50 +, P = 0.0001).ConclusionsVMI reconstructed with nMERA at 50 keV is preferable for evaluation of patients with breast cancer.

Background Coronary magnetic resonance angiography (CMRA) is a promising technique for assessing the coronary arteries. However, a disadvantage of CMRA is the comparatively long acquisition time. Compressed sensing (CS) can considerably reduce the scan time. The aim of this study was to verify the feasibility of CS CMRA scanning during the waiting time between contrast injection and late gadolinium enhancement (LGE) scan in a clinical protocol. Methods Fifty clinical patients underwent contrast-enhanced CS CMRA and conventional CMRA on a 3 T CMR scanner. After contrast injection, CS CMRA was scanned during the waiting time for LGE CMR. A conventional CMRA scan was performed after LGE CMR. We assessed acquisition times and coronary artery image quality for each segment on a 4-point scale. Visible vessel length, sharpness and diameter of right (RCA), left anterior descending (LAD), and left circumflex (LCX) coronary arteries were also quantitatively compared among the scans. Results All CS CMRA scans were successfully performed within the LGE waiting time. The median total scan time was 207 s (163, 259 s) for CS and 785 s (698, 975 s) for conventional CMRA ( p  < 0.001). No significant differences were observed in image quality scores, vessel length measurements, sharpness, and diameter between CS and conventional CMRA. Conclusions We could achieve all CS CMRA scans within the LGE waiting time. Contrast-enhanced CS CMRA could considerably shorten the scan time while maintaining image quality compared with conventional CMRA.

Computed tomography (CT)-derived three-dimensional maximum principal strain (MP-strain) can provide incremental value to coronary CT angiography for cardiac dysfunction assessment with high diagnostic performance in patients with myocardial infarction. Global longitudinal strain (GLS) measured using two-dimensional speckle tracking echocardiography (2D-STE) is more sensitive than left ventricular ejection fraction (LVEF) for detecting early myocardial dysfunction. We aimed to compare CT-derived MP-strain with each of 2D-STE-derived strains (i.e., longitudinal, circumferential, and radial strains), and identify the major determinants of CT-derived MP-strain among 2D-STE-derived strains. We studied 51 patients who underwent cardiac CT and echocardiography. CT images were reconstructed at every 5% (0–95%) of the RR interval. A dedicated workstation was used to analyze CT-derived MP-strain on the 16-segment model. We calculated CT-derived global MP-strain with all the 16 segments on a per patient basis. Pearson’s test was used to assess correlations between CT-derived MP-strain and STE-strain at global and segmental levels. The intra-class correlation coefficient for interobserver agreement for CT-derived global MP-strain was 0.98 (95% confidence interval 0.96–0.99). The low-CT-derived global MP-strain group (≤ 0.43) had more patients with LV dysfunction than the high-CT-derived global MP-strain group (> 0.43). CT-derived global MP-strain was associated with STE-GLS ( r  = 0.738, P  < 0.001), global circumferential strain ( r  = 0.646, P  < 0.001), and global radial strain ( r  = 0.432, P  = 0.001). In multivariate analysis, STE-GLS had the strongest association to CT-derived global MP-strain among three directional STE-strains and LVEF by echocardiography (standardized coefficient =  − 0.527, P  < 0.001). STE-GLS is a major determinant of CT-derived global MP-strain. CT-derived MP-strain may enhance the value of coronary CT angiography by adding functional information to CT-derived LVEF.

Background Feature tracking (FT) has become an established tool for cardiovascular magnetic resonance (CMR)-based strain analysis. Recently, the compressed sensing (CS) technique has been applied to cine CMR, which has drastically reduced its acquisition time. However, the effects of CS imaging on FT strain analysis need to be carefully studied. This study aimed to investigate the use of CS cine CMR for FT strain analysis compared to conventional cine CMR. Methods Sixty-five patients with different left ventricular (LV) pathologies underwent both retrospective conventional cine CMR and prospective CS cine CMR using a prototype sequence with the comparable temporal and spatial resolution at 3 T. Eight short-axis cine images covering the entire LV were obtained and used for LV volume assessment and FT strain analysis. Prospective CS cine CMR data over 1.5 heartbeats were acquired to capture the complete end-diastolic data between the first and second heartbeats. LV volume assessment and FT strain analysis were performed using a dedicated software (ci 42 ; Circle Cardiovasacular Imaging, Calgary, Canada), and the global circumferential strain (GCS) and GCS rate were calculated from both cine CMR sequences. Results There were no significant differences in the GCS (− 17.1% [− 11.7, − 19.5] vs. − 16.1% [− 11.9, − 19.3; p = 0.508) and GCS rate (− 0.8 [− 0.6, − 1.0] vs. − 0.8 [− 0.7, − 1.0]; p = 0.587) obtained using conventional and CS cine CMR. The GCS obtained using both methods showed excellent agreement (y = 0.99x − 0.24; r = 0.95; p < 0.001). The Bland–Altman analysis revealed that the mean difference in the GCS between the conventional and CS cine CMR was 0.1% with limits of agreement between -2.8% and 3.0%. No significant differences were found in all LV volume assessment between both types of cine CMR. Conclusion CS cine CMR could be used for GCS assessment by CMR-FT as well as conventional cine CMR. This finding further enhances the clinical utility of high-speed CS cine CMR imaging.

Background Cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) is a valuable technique for detecting myocardial disorders and fibrosis. However, we sometimes observe a linear, mid-wall high intensity signal in the basal septum in the short axis view, which often presents diagnostic difficulties in the clinical setting. The purpose of this study was to compare the linear, mid-wall high intensity in the basal septum identified by LGE with the anterior septal perforator arteries identified by coronary computed tomography angiography (CorCTA). Methods We retrospectively selected 148 patients who underwent both CorCTA and CMR LGE within 1 year. In the interpretation of LGE, we defined a positive linear high intensity (LHI+) as follows: ① LHI in the basal septum and ② observable for 1.5 cm or more. All other patients were defined as a negative LHI (LHI-). In LHI+ patients, we assessed the correlation between the LHI length and the septal perforator artery length on CorCTA. We also compared the length of the septal perforator artery on CorCTA between LHI+ patients and LHI- patients. Results A population of 111 patients were used for further analysis. Among these , there were 55 LHI+ patients and 56 LHI- patients. In LHI+ patients, linear regression analysis revealed that there was a good agreement between LGE LHI and septal perforator arteries by CorCTA in terms of length measurements. The measured length of the anterior septal perforator arteries was significantly shorter in LHI- patients than in LHI+ patients (10 ± 8 mm vs. 21 ± 8 mm; P  < 0.05). Conclusions The LHI observed in the basal septum on short axis LGE may reflect contrast enhancement of the anterior septal perforator arteries. It is important to interpret this septal LHI against knowledge of anatomic structure, to avoid misinterpretations of LGE and prevent misdiagnosis.

Background Deep learning–based methods have been used to denoise magnetic resonance imaging. Purpose The purpose of this study was to evaluate a deep learning reconstruction (DL Recon) in cardiovascular black-blood T2-weighted images and compare with intensity filtered images. Material and Methods Forty-five DL Recon images were compared with intensity filtered and the original images. For quantitative image analysis, the signal to noise ratio (SNR) of the septum, contrast ratio (CR) of the septum to lumen, and sharpness of the endocardial border were calculated in each image. For qualitative image quality assessment, a 4-point subjective scale was assigned to each image (1 = poor, 2 = fair, 3 = good, 4 = excellent). Results The SNR and CR were significantly higher in the DL Recon images than in the intensity filtered and the original images (p < .05 in each). Sharpness of the endocardial border was significantly higher in the DL Recon and intensity filtered images than in the original images (p < .05 in each). The image quality of the DL Recon images was significantly better than that of intensity filtered and original images (p < .001 in each). Conclusions DL Recon reduced image noise while improving image contrast and sharpness in the cardiovascular black-blood T2-weight sequence.

Objectives The purpose of this study was to estimate the myocardial area at risk (MAAR) using coronary computed tomography angiography (CTA) and Voronoi algorithm-based myocardial segmentation in comparison with single-photon emission computed tomography (SPECT). Methods Thirty-four patients with coronary artery disease underwent 128-slice coronary CTA, stress/rest thallium-201 SPECT, and coronary angiography (CAG). CTA-based MAAR was defined as the sum of all CAG stenosis (>50 %) related territories (the ratio of the left ventricular volume). Using automated quantification software (17-segment model, 5-point scale), SPECT-based MAAR was defined as the number of segments with a score above zero as compared to the total 17 segments by summed stress score (SSS), difference (SDS) score map, and comprehensive SPECT interpretation with either SSS or SDS best correlating CAG findings (SSS/SDS). Results were compared using Pearson's correlation coefficient. Results Forty-nine stenoses were observed in 102 major coronary territories. Mean value of CTA-based MAAR was 28.3 ± 14.0 %. SSS-based, SDS-based, and SSS/SDS-based MAAR was 30.1 ± 6.1 %, 20.1 ± 15.8 %, and 26.8 ± 15.7 %, respectively. CTA-based MAAR was significantly related to SPECT-based MAAR ( r  = 0.531 for SSS; r  = 0.494 for SDS; r  = 0.814 for SSS/SDS; P  < 0.05 in each). Conclusions CTA-based Voronoi algorithm myocardial segmentation reliably quantifies SPECT-based MAAR. Key points • Voronoi algorithm allows for three-dimensional myocardial segmentation of coronary CT angiography • Stenosis-related CT myocardial territories correlate to SPECT based area at risk • CT angiography myocardial segmentation may assist in clinical decision-making