Significance of systolic-phase imaging on full-phase ECG-gated CT angiography to detect intimal tears in aortic dissection.

PURPOSE: For patients with aortic dissection (AD) and intramural hematoma (IMH), the optimal cardiac phase to detect intimal tears (IT) and ulcer-like projections (ULP) on retrospective electrocardiogram (ECG)-gated computed tomography angiography (CTA) remains unclear. The purpose of this study was to compare the accuracy of retrospective ECG-gated CTA for detecting IT in AD and ULP in IMH between each cardiac phase. MATERIALS AND METHODS: A total of 75 consecutive patients with AD and IMH of the thoracic aorta were enrolled in this single-center retrospective study. The diagnostic performance to detect IT and ULP in the thoracic aortic regions (including the ascending aorta, aortic arch, and proximal and distal descending aorta) was compared in each cardiac phase on retrospective ECG-gated CTA. RESULTS: In the systolic phase (20%), the accuracy, sensitivity, and specificity to detect IT in AD was 64% (95% confidence interval [CI] 56-72%), 69% (95%CI 60-78%), and 25% (95%CI 3.3-45%), respectively. In the diastolic phase (70%), the accuracy, sensitivity, and specificity to detect IT in AD was 52% (95%CI 43-60%), 52% (95%CI 42-61%), and 50% (95%CI 25-75%), respectively. The accuracy to detect IT in AD on ECG-gated CTA was significantly higher in the systolic phase than that in the diastolic phase (P = 0.025). However, there were no differences in the accuracy (83%; 95%CI 78-89%), sensitivity (71%; 95%CI 62-80%), or specificity (100%; 95%CI 100%) to detect ULP in IMH between the cardiac cycle phases. CONCLUSION: Although it is currently recommended for routine diagnosis of AD and IMH, single-diastolic-phase ECG-gated CTA has risk to miss some IT in AD that are detectable in the systolic phase on full-phase ECG-gated CTA. This information is critical for determining the optimal treatment strategy for AD.

Ultrashort echo time time-spatial labeling inversion pulse magnetic resonance angiography with denoising deep learning reconstruction for the assessment of abdominal visceral arteries.

Current contrast-enhanced magnetic resonance angiography (MRA) and non-contrast-enhanced balanced steady-state free precession (bSSFP) MRA cause susceptibility artifacts from metallic devices in assessing endovascular visceral-artery interventions. The aims of this study are to investigate and compare image quality (IQ) and susceptibility artifacts of three-dimensional (3D) ultrashort echo time (UTE) time-spatial labeling inversion pulse (Time-SLIP) with those of 3D bSSFP Time-SLIP and to assess denoising deep learning reconstruction (dDLR) for the improvement of the signal-to-noise ratio (SNR) in 3D UTE with sparse sampling in phantoms and human subjects. This is a prospective type of study. Pulsatile glycerin-water flow phantom with platinum-tungsten-alloy coil, stainless-steel, nitinol, and cobalt-alloy stents were used. Ten healthy volunteers (seven males) and three patients (two males) were included in this study. 3D UTE Time-SLIP and 3D bSSFP Time-SLIP at 3T were used. The phantom-based study compared the signal-intensity ratio of the device levels (SRdevice ) and distal segments (SRdistal ) to the proximal segments. The volunteer-based study measured SNR, contrast ratio (CR), and IQ. The patient study evaluated local artifacts from metallic devices. Statistical tests included paired t-tests, Wilcoxon-signed rank tests, and Kruskal-Wallis tests. In the phantom-based study, SRdevice was small with UTE Time-SLIP, except the stainless-steel stent. SRdistal was greater (49.1%-90.4%) on bSSFP images than UTE images (-11.1% to 9.6%). Among volunteers, dDLR in UTE images improved SNR (p < 0.05) and IQ (p < 0.05), but CR was unaffected. UTE Time-SLIP showed inferior SNR and IQ than bSSFP Time-SLIP in images with and without dDLR (p < 0.05 for each). However, among patients, UTE Time-SLIP showed reduced metal artifacts compared to bSSFP Time-SLIP. Irrespective of the lower SNR and IQ of 3D UTE Time-SLIP than those of 3D bSSFP Time-SLIP, the former appeared to better depict flow after stenting or coiling. This indicates the potential of 3D UTE Time-SLIP to provide suitable diagnostic images of target vessels. dDLR improved SNR with reducing artifacts related to radial sampling, while maintaining the contrast. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 2.

Myocardial viability with chronic total occlusion assessed by hybrid positron emission tomography/magnetic resonance imaging.

BACKGROUND: The present study was performed to compare the relationship of 18F-fluorodeoxyglucose (FDG) uptake and late gadolinium enhancement (LGE) transmurality with the improvement of left ventricular function in patients with coronary chronic total occlusion (CTO) assessed by hybrid FDG positron emission tomography (PET)/magnetic resonance imaging (MRI). METHODS: Thirty-eight consecutive patients with CTO underwent FDG PET/MRI. Twenty-three patients then underwent percutaneous coronary intervention (PCI), and the final study population comprised 15 patients who underwent both initial and follow-up MRI. The degree of wall motion abnormality in each of the 17 myocardial segments was evaluated based on the extent of wall thickening on cine MRI using a 5-point scale. RESULTS: Among all 646 myocardial segments at baseline, FDG uptake significantly decreased as the transmurality of LGE is advanced. Of the 15 patients who underwent PCI, 152 segments showed wall motion abnormalities at baseline. The functional recovery of the wall motion abnormality of the PET-viable/MRI-viable segments was highest, and that of the PET-nonviable/MRI-nonviable segments was lowest. There were no differences in functional recovery between the PET-viable/MRI-nonviable and PET-nonviable/MRI-viable segments. CONCLUSION: Simultaneous assessment of FDG and LGE using a hybrid PET/MRI system can help to predict functional recovery after PCI in patients with CTO.

Volume-based glucose metabolic analysis of FDG PET/CT: The optimum threshold and conditions to suppress physiological myocardial uptake.

OBJECTIVE: FDG PET/CT plays a significant role in the diagnosis of inflammatory heart diseases and cardiac tumors. We attempted to determine the optimal FDG uptake threshold for volume-based analyses and to evaluate the relationship between the myocardial physiological uptake volume in FDG PET and several clinical factors. METHODS: A total of 190 patients were retrospectively analyzed. The cardiac metabolic volume (CMV) was defined as a volume within the boundary determined by a threshold (SUVmean of blood pool × 1.5). RESULTS: The SUVmean of the blood pool measured in the descending aorta (DA) (r = 0.86, intraclass correlation coefficient [ICC] = 0.93, P < 0.0001) and that in the left ventricle (LV) cavity (r = 0.87, ICC = 0.90, P < 0.0001) showed high inter-operator reproducibility. However, the SUVmean in the LV cavity showed a significant correlation with the CMV (P = 0.0002, r = 0.26). The CMV in the patients who fasted < 18 hours were significantly higher (49.7  ±  73.2 vs. 18.0  ±  53.8 mL, P = 0.0013) compared to the patients with > 18-hour fasting. The multivariate analysis demonstrated that only the fasting period > 18 hours was independently associated with CMV = 0. CONCLUSION: Our findings revealed that the DA is suitable to decide the threshold for the volume-based analysis. The fasting time was significantly associated with the cardiac FDG uptake.

Technical aspects of cardiac PET/MRI.

PET/MRI is a novel modality that enables to combine PET and MR images, and has significant potential to evaluate various cardiac diseases through the combination of PET molecular imaging and MRI functional imaging. Precise management of technical issues, however, is necessary for cardiac PET/MRI. This article describes several technical points, including patient preparation, MR attenuation correction, parallel acquisition of PET with MRI, clinical aspects, and image quality control.

The effects of 18-h fasting with low-carbohydrate diet preparation on suppressed physiological myocardial (18)F-fluorodeoxyglucose (FDG) uptake and possible minimal effects of unfractionated heparin use in patients with suspected cardiac involvement sarcoidosis.

BACKGROUND: (18)F-fluorodeoxyglucose (FDG) PET plays an important role in the detection of cardiac involvement sarcoidosis (CS). However, diffuse left ventricle (LV) wall uptake sometimes makes it difficult to distinguish between positive uptake and physiological uptake. The aims of this study were to evaluate the effects of 18-h fasting with low-carbohydrate diet (LCD) vs a minimum of 6-h fasting preparations on diffuse LV FDG uptake and free fatty acid (FFA) levels in patients with suspected CS. METHODS: Eighty-two patients with suspected CS were divided into 2 preparation protocols: one with a minimum 6-h fast without LCD preparation (group A, n = 58) and the other with a minimum 18-h fast with LCD preparation (group B, n = 24). All patients also received intravenous unfractionated heparin (UFH; 50 IU/kg) before the injection of FDG. RESULTS: Group A showed a higher percentage of diffuse LV uptake than did group B (27.6 vs 0.0%, P = .0041). Group B showed higher FFA levels (1159.1 ± 393.0, 650.5 ± 310.9 µEq/L, P < .0001) than did group A. Patients with diffuse LV uptake (n = 16) showed lower FFA levels than did other patients (n = 66) (432.1 ± 296.1, 888.4 ± 381.4 µEq/L, P < .0001). UFH administration significantly increased FFAs in both groups, even in the patients with diffuse LV FDG uptake. CONCLUSIONS: The 18-h fast with LCD preparation significantly reduced diffuse LV uptake and increased FFA levels. In particular, the FFA level was significantly lower in patients with LV diffuse uptake than in patients without LV diffuse uptake. Acutely increasing plasma FFA through the use of UFH may not have a significant role in reducing physiological LV FDG uptake.

Administration of unfractionated heparin with prolonged fasting could reduce physiological 18F-fluorodeoxyglucose uptake in the heart.

BACKGROUND: The physiological uptake of 18F-fluorodeoxyglucose (FDG) in the heart often interferes with the accurate diagnosis of inflammatory cardiac diseases (CDs). Unfractionated heparin (UFH) administration may suppress its uptake through the alteration of myocardial metabolism. PURPOSE: To clarify the effectiveness of UFH administration to suppress the physiological FDG uptake in the heart. MATERIAL AND METHODS: The physiological FDG uptake in the heart was compared among 178 patients who fasted less than 18 h, 37 patients who fasted more than 18 h, and 64 patients who fasted more than 18 h and were administered UFH (UFH-CD group) prior to FDG PET/CT. Free fatty acid (FFA), triglyceride, insulin, and blood glucose levels were measured after UFH administration. Myocardial FDG uptake was evaluated by visual assessment and on the basis of maximum standardized uptake value (SUVmax). RESULTS: In the UFH-CD group, the FFA level increased 15 min after UFH administration (P < 0.01). Blood glucose and insulin levels remained unchanged (P = NS). FDG physiological uptake was observed in 69% of the patients who fasted less than 18 h, 38% of the patients fasted more than 18 h, and 22% of the UFH-CD group (P < 0.01 for trend). SUVmax decreased in the UFH-CD group compared with the patients who fasted less than 18 h (P < 0.01) and the patients who fasted more than 18 h (P = 0.029). CONCLUSION: UFH administration and fasting more than 18 h could effectively suppress FDG physiological uptake in the heart and can be a useful method of detecting inflammatory CDs and tumors.

Post-ISCHEMIA Trial Era: Reconsideration of the Role of Nuclear Cardiology in Patients with Chronic Coronary Artery Disease.

The International Study of Comparative Health Effectiveness with Medical and Invasive Approaches (ISCHEMIA) trial has had a great impact on the management of chronic coronary artery disease (CAD). One of the implications of this trial is the importance of close patient follow-up. To improve patient prognosis, evaluation of the residual extent of ischemia after treatment may be important because several studies have shown a close relationship between residual ischemia and cardiac events. For this assessment, myocardial perfusion single-photon emission computed tomography (MPS) has been utilized and is almost the only modality. Among the participants in the ISCHEMIA trial, more than 10% were excluded due to the absence of obstructive CAD. The pathophysiology of ischemia without non-obstructive coronary artery disease (INOCA) is gaining recognition; however, diagnosis is difficult, except for the assessment of myocardial flow reserve (MFR). Myocardial perfusion positron emission tomography (PET) is the most common modality for noninvasive evaluation of MFR; however, its availability in Japan is limited. For a breakthrough in this situation, a novel gamma camera with a cadmium zinc telluride (CZT) semiconductor might be one of the solutions that enables the evaluation of MFR with a commercially available perfusion tracer, similar to PET. Another solution is a novel PET tracer with a longer half-life. Clinical trials with 18F labeled perfusion agents have been initiated in Japan, and in a few years, delivery of this perfusion tracer will result in more frequent and easier assessment of MFR.

Detection of the intimal tear in aortic dissection and ulcer-like projection in intramural hematoma: usefulness of full-phase retrospective ECG-gated CT angiography.

PURPOSE: To compare the accuracy of non-electrocardiogram (ECG)-gated CT angiography (CTA), single-diastolic-phase ECG-gated CTA, and full-phase ECG-gated CTA in detecting the intimal tear (IT) in aortic dissection (AD) and ulcer-like projection (ULP) in intramural hematoma (IMH). MATERIALS AND METHODS: A total of 81 consecutive patients with AD and IMH of the thoracic aorta were included in this single-center retrospective study. Non-ECG-gated CTA, single-diastolic-phase ECG-gated CTA, and full-phase ECG-gated CTA were used to detect the presence of the IT and ULP in thoracic aortic regions including the ascending aorta, aortic arch, and proximal and distal descending aorta. RESULTS: The accuracy of detecting the IT and ULP was significantly greater using full-phase ECG-gated CTA (88% [95% CI: 100%, 75%]) than non-ECG-gated CTA (72% [95% CI: 90%, 54%], P = 0.001) and single-diastolic-phase ECG-gated CTA (76% [95% CI: 93%, 60%], P = 0.008). CONCLUSION: Full-phase ECG-gated CTA is more accurate in detecting the IT in AD and ULP in IMH, than non-ECG-gated CTA and single-diastolic-phase ECG-gated CTA.

Accelerated (99m)Tc-sestamibi clearance associated with mitochondrial dysfunction and regional left ventricular dysfunction in reperfused myocardium in patients with acute coronary syndrome.

BACKGROUND: Accelerated clearance of (99m)technetium-sestamibi (MIBI) has been observed after reperfusion therapy in patients with acute coronary syndrome (ACS), but the mechanisms have not been fully investigated. MIBI retention may depend on mitochondrial function. The clearance rate of (11)carbon-acetate reflects such mitochondrial functions as oxidative metabolism. The purpose of this study was to examine the mechanisms of accelerated MIBI clearance in ACS. We therefore compared it to oxidative metabolism estimated using (11)C-acetate positron emission tomography (PET). METHODS: Eighteen patients [mean age 69.2 ± 8.7 years, 10 males (56 %)] with reperfused ACS underwent MIBI single-photon emission computed tomography (SPECT), echocardiography, and (11)C-acetate PET within 3 weeks of the onset of ACS. MIBI images were obtained 30 min and 3 h after MIBI administration. Regional left ventricular (LV) function was evaluated by echocardiography. The measurement of oxidative metabolism was obtained through the mono-exponential fitting of the (11)C-acetate time-activity curve (k mono). RESULTS: Among 95 segments of reperfused myocardium, MIBI SPECT showed 64 normal segments (group N), 14 segments with accelerated MIBI clearance (group AC), and 17 segments with fixed defect (group F). Group AC showed lower k mono than group N (0.041 ± 0.009 vs 0.049 ± 0.010, p = 0.02). Group F showed lower k mono than group N (0.039 ± 0.012 vs 0.049 ± 0.010, p = 0.01). However, k mono was similar in group AC and group F (p = 0.99). CONCLUSIONS: Segments with accelerated MIBI clearance showed reduced oxidative metabolism in ACS. Loss of MIBI retention may be associated with mitochondrial dysfunction.