Hybrid Assessment of Myocardial Ischemia Using Stress-Only Nuclear Myocardial Perfusion Imaging and Rest Computed Tomography Perfusion Imaging.

BACKGROUND: Sequential assessment using CT coronary angiography (coronary CT) and nuclear myocardial perfusion imaging (MPI) is considered an anatomical and functional evaluation of coronary artery disease (CAD). However, there can be unexpected radiation exposure. Hybrid MPI with stress-only nuclear MPI and rest CT-MPI using coronary CT may contribute to reducing the radiation dose in sequential assessment with nuclear MPI after coronary CT. We analyzed the diagnostic performance and total radiation dose of hybrid MPI for detection of significant CAD compared with sequential assessment using nuclear MPI after coronary CT.Methods and Results:The results for 101 patients who underwent coronary CT, nuclear MPI and invasive coronary angiography within 3 months of all imaging were analyzed. We calculated the summed difference score (SDS) from standard nuclear MPI and hybrid SDS from hybrid MPI, which revealed myocardial ischemia. The diagnostic performance of SDS and hybrid SDS for detecting significant CAD was analyzed using receiver-operating characteristic (ROC) curve analysis. We also compared the total radiation dose of both methods. The area under the ROC curve was not different between SDS and hybrid SDS (0.901 and 0.815, P=0.079). Total radiation dose of hybrid MPI was significantly lower than standard nuclear MPI with CT angiography (4.62 mSv vs. 9.72 mSv, P<0.0001). CONCLUSIONS: Hybrid MPI showed a precise diagnostic accuracy for significant CAD detection.

Superiority of the extracellular volume fraction over the myocardial T1 value for the assessment of myocardial fibrosis in patients with non-ischemic cardiomyopathy.

PURPOSE: This study aimed to assess the efficacies of the myocardial T1 value and the extracellular volume fraction (ECV) for determining the severity of myocardial fibrosis in patients with non-ischemic cardiomyopathy. MATERIALS AND METHODS: Myocardial fibrosis is considered the most important indicator of cardiac damage associated with non-ischemic cardiomyopathy. Recently, modified Look-Locker inversion recovery imaging (MOLLI) has been used for T1 mapping and measurement of the ECV for the assessment of myocardial fibrosis. The present study included 22 patients (mean age, 61.5±12.7; 21 male) with non-ischemic heart failure. Motion corrected myocardial T1 mapping was automatically performed using a MOLLI sequence, and the ECV was estimated from the pre- and post-contrast blood and myocardial T1 values corrected for the hematocrit level. All endomyocardial biopsy specimens were obtained from the inferoposterior left ventricular wall. The percentage of myocardial fibrosis (%F) was determined after Elastica Masson-Goldner staining as follows: (fibrosis area/[fibrosis area+myocardial area])×100. RESULTS: No correlation was noted between the %F and the pre- (r=0.290, p=0.191) or post-contrast T1 values (r=-0.190, p=0.398); however, a significant correlation was noted between the %F and ECV (r=0.750, p<0.001). CONCLUSIONS: In this study, the ECV reflected the extent of myocardial fibrosis, but the pre- and post-contrast T1 values did not. The ECV may be used to estimate the severity of myocardial fibrosis in patients with non-ischemic cardiomyopathy.

4D flow MRI assessment of extracranial-intracranial bypass: qualitative and quantitative evaluation of the hemodynamics.

INTRODUCTION: Our aim was to assess the feasibility of using time-resolved 3D phase-contrast (4D flow) MRI to characterize extracranial-intracranial (EC-IC) bypass. METHODS: We enrolled 32 patients who underwent EC-IC bypass (15 men, 17 women; mean age 66.4 years). In all, 16 underwent radial artery graft (RAG) bypass and 16 underwent superficial temporal artery (STA) bypass. 4D flow MRI, time-of-flight (TOF) magnetic resonance angiography (MRA), and computed tomography angiography (CTA) were performed. Bypass patency, flow direction, and blood flow volume (BFV) of each artery were determined by 4D flow MRI. Arterial diameters were measured by TOF-MRA and CTA. We compared RAG and STA bypasses by evaluating the flow direction and BFV of each artery. We evaluated the correlation between arterial diameters (measured by CTA or MRA) and the BFV and the detectability of flow direction (measured by 4D flow MRI) of each artery. RESULTS: 4D flow MRI confirmed the patency of each bypass artery. Flow direction of the M1 segment of the middle cerebral artery and BFV in the bypass artery differed between RAG and STA groups (p < 0.01). BFV in the bypass slightly correlated with the diameters on CTA (p < 0.05, R (2) = 0.287). Of the 29 arteries in the circle of Willis, nine were not depicted on 4D flow MRI. Cutoff values for arterial diameters on CTA and TOF-MRA for detecting the artery on 4D flow MRI were 2.4 and 1.8 mm, respectively. CONCLUSION: 4D flow MRI provided unique information for characterizing EC-IC bypasses, although this detectability is limited when addressing small arteries with slow flow.

Contrast-enhanced Steady-state Free Precession in the Assessment of Hypertrophic Obstructive Cardiomyopathy after Alcohol Septal Ablation.

PURPOSE: We evaluated the feasibility of contrast-enhanced steady-state free precession (ceSSFP) in the assessment of myocardial injury and obstruction of the left ventricular outflow tract (LVOT) in patients with hypertrophic obstructive cardiomyopathy (HOCM) after alcohol septal ablation (ASA). METHODS: Twelve patients with HOCM underwent 16 magnetic resonance (MR) examinations following ASA. Precontrast SSFP, ceSSFP and late gadolinium enhancement (LGE) imaging were performed with a 1.5-tesla imager. ceSSFP was performed 3 to 7 min after gadolinium injection. We visually and quantitatively evaluated the signal patterns of the myocardium after ASA on SSFP and LGE MR imaging. We observed the LVOT using ceSSFP in the 3-chamber view. RESULTS: We could visualize ASA-induced myocardial infarction (MI) in all 16 studies by LGE and ceSSFP but in only 6 studies (37.5%) by precontrast SSFP. Contrast was higher between MI and remote myocardium with LGE than ceSSFP (P < 0.01). ASA-induced hypointense regions were well visualized by the 2 sequences after contrast in the 7 patients who underwent MR imaging within 7 weeks of ASA and in a few patients after 80 weeks from ASA. The ceSSFP allowed comparable visualization of the jet flow crossing the LVOT to that derived from echocardiographic data. CONCLUSION: Contrast-enhanced steady-state free precession allows assessment of myocardial injury as well as of the left ventricular outflow tract after alcohol septal ablation in a single scan without penalty in scan time and cine imaging contrast.

Simultaneous assessment of myocardial scar and coronary arteries using navigator-gated 3-dimensional fat-suppressed delayed-enhancement MRI at 3.0 T: a technical feasibility study.

OBJECTIVE: To assess technical feasibility of navigator-gated 3-dimensional (3D) fat-suppressed delayed-enhancement magnetic resonance imaging (DE-MRI) at 3.0 T for simultaneous visualization of myocardial scars and coronary arteries. METHODS: Thirty patients with various myocardial diseases underwent navigator-gated 3D fat-suppressed DE-MRI using a 3.0-T scanner. The ability of this imaging technique to detect myocardial scars was compared with that of 2D DE-MRI. Visualization of the coronary arteries by this MRI technique was scored, and the relationship between myocardial scars and coronary arteries was assessed. RESULTS: Navigator-gated 3D fat-suppressed DE-MRI detected 71 of 75 segments with a myocardial scar. This imaging visualized proximal coronary arteries with an acceptable image quality and demonstrated a relationship between the myocardial scars and coronary arteries in 11 of the patients with scars. CONCLUSION: Navigator-gated 3D fat-suppressed DE-MRI at 3.0 T was feasible for simultaneous visualization of myocardial scars and proximal coronary arteries.

Assessment of renal impairment by non-contrast-enhanced conventional magnetic resonance imaging: comparison with 99mTc-DTPA renography.

PURPOSE: The aim of this study was to determine whether non-contrast-enhanced magnetic resonance imaging (MRI) can detect three levels of renal impairment by evaluating the differences and agreement with (99m)Tc-diethylenetriamine pentaacetic acid (DTPA) renography. MATERIALS AND METHODS: A total of 28 patients with kidney disease were enrolled in the study. MRI findings, including visual corticomedullary differentiation (CMD) on T1- and T2-weighted imaging (T1WI, T2WI), cortical irregularity, the number of renal cysts, and the volume of the kidney, were evaluated for individual kidneys and pairs of kidneys. The differences and agreement between MRI findings and the three levels of renal impairment based on the glomerular filtration rate (GFR) measured using (99m)Tc-DTPA renography were analyzed. RESULTS: All MRI findings except the number of renal cysts in pairs of kidneys were consistent with the patient's classification. The agreement between the patient's classifications based on GFR and that based on the visual CMD on T1WI and T2WI was almost perfect or substantial in both individual kidneys and pairs of kidneys. CONCLUSION: Non-contrast-enhanced MRI was capable of distinguishing three levels of renal function, including serious renal impairment.

Delayed-enhancement MRI of apical hypertrophic cardiomyopathy: assessment of the intramural distribution and comparison with clinical symptoms, ventricular arrhythmias, and cine MRI.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is reported to show patchy midwall myocardial hyperenhancement on delayed-enhancement magnetic resonance imaging (DE-MRI). The intramural distribution of myocardial hyperenhancement and its correlation with clinical symptoms, ventricular arrhythmias, and cardiac function have not been described forsymptomatic apical HCM. PURPOSE: To evaluate the features and significance of myocardial hyperenhancement on DE-MRI insymptomatic apical HCM. MATERIAL AND METHODS: Thirteen patients with symptomatic apical HCM and their 65 apical segments were investigated. Myocardial hyperenhancement and regional and global functional parameters were determined with MRI. We investigated the intramural distribution and frequencies of this myocardial hyperenhancement and compared them with the patients' clinical symptoms, the presence of ventricular arrhythmias, and cine MRI. RESULTS: Eight (61.5%) patients with symptomatic apical HCM displayed apical myocardial hyperenhancement, and 22 (33.8%) of the 65 apical segments examined showed myocardial hyperenhancement. Of the myocardial hyperenhancement observed, 81.8% showed a subendocardial pattern.The hyperenhanced apical myocardium had a lower percentage of systolic myocardial thickening, and was associated with serious symptoms (e.g. syncope) and ventricular arrhythmias. CONCLUSION: Patients with symptomatic apical HCMshowed myocardial hyperenhancement involving the subendocardial layer, which might be related to regional systolic dysfunction, serious clinical symptoms, and ventricular arrhythmias.

MR imaging for preoperative diagnosis and assessment of local tumor extent on localized giant cell tumor of tendon sheath.

OBJECTIVE: The purpose of this study was to clarify the usefulness of MR imaging for preoperative diagnosis and evaluation of the extent of localized giant cell tumor of tendon sheath (GCTTS). DESIGN AND PATIENTS: We retrospectively reviewed the MR images of 25 patients with surgically proved GCTTS (seven males and 18 females; mean age, 41 years) including five recurrences. T1- and T2-weighted imaging was carried out on 24 and 22 lesions, respectively. Gadolinium-enhanced images were obtained for 20 lesions. We evaluated the tumor extent around the phalanx (the degree of circumferential occupation by a tumor around the phalanx on an axial plane) and involvement of the bone, joint, and tenosynovial space by both MR imaging and surgery (gold standard). RESULTS: MR signal intensities of the GCTTSs were consistently equal to those of skeletal muscle or between those of muscle and fat on T1-weighted images; on T2-weighted images, the signal intensities tended to be between those of muscle and fat. Most lesions were inhomogeneous due to low-signal-intensity areas, and enhanced following gadolinium administration. The tumor extent around the phalanx was 168.5 +/- 99.2 degrees (63-360 degrees). MR imaging did not identify the bone involvement (five lesions), but depicted the involvement of the joint in four of five lesions and the tenosynovial space in nine of ten lesions. CONCLUSIONS: This study confirms that MR imaging is able to depict the characteristic internal signal of GCTTS. Moreover, it can accurately assess the tumor size and degree of extent around the phalanx, which can affect the type of surgical approach.

Quantitative and qualitative assessment of reactive hematopoietic bone marrow in aplastic anemia using MR spectroscopy with variable echo times.

OBJECTIVE: To assess quantitative and qualitative differences in water components between normal bone marrow and reactive hematopoietic marrow in aplastic anemia using magnetic resonance (MR) spectroscopy with variable echo times (TEs). DESIGN: Water content, T2 value of the water component, and signal change in water related to TE were assessed in normal bone marrow and reactive hematopoietic bone marrow by a stimulated echo acquisition mode with TEs of 30, 45, 60, and 90 ms. PATIENTS: Six patients with aplastic anemia (13-84 years) and seven normal volunteers (25-38 years) were examined. RESULTS AND CONCLUSION: Reactive hematopoietic marrow showed significantly higher water content than normal bone marrow. The T2 value of water components tended to be longer in reactive hematopoietic marrow. Water signal ratio related to TE was significantly higher in reactive hematopoietic marrow. These results suggest a quantitative and qualitative difference in water components between normal and reactive hematopoietic bone marrow.