MR-relaxometry of myocardial tissue: significant elevation of T1 and T2 relaxation times in cardiac amyloidosis

OBJECTIVE: This study evaluates if MR-relaxometry of myocardial tissue reveals significant differences in cardiac amyloidosis (CA) compared with patients with systemic amyloidosis but without cardiac involvement (NCA) and a healthy control group. Therefore, we measured T1 and T2 relaxation times (RT) of the left ventricular myocardium with magnetic resonance imaging at 1.5 T. MATERIAL AND METHODS: Nineteen consecutive patients (14 males, 5 females; mean age, 59 +/- 6.1 years) with histologically proven CA were evaluated. T1-RT and T2-RT were measured by using a saturation-recovery TurboFLASH sequence and a HASTE sequence, respectively. Additionally, morphologic and functional data were acquired. Results were compared with patients with systemic amyloidosis but without cardiac involvement (NCA; 5 males, 4 females, 48.9 +/- 15.4 years) and 10 healthy, age-matched control subjects (5 males, 5 females, 60.4 +/- 6.4 years). RESULTS: MR-relaxometry revealed a significant elevation of T1-RT of the left ventricular myocardium in CA-patients compared with that in NCA-patients and the age-matched control group [mean +/- SD (95% CI) 1340 +/- 81 (1303-1376) msec, 1213 +/- 79 (1160-1266) msec, 1146 +/- 71 (1096-1196) msec, respectively; CA vs. control, P < 0.0001; CA vs. NCA:, P < 0.0003; NCA vs. control, P = 0.07]. T2-RT showed a marginal but significant increase in CA-patients compared with NCA-patients and the control group [mean +/- SD (95% CI) 81 +/- 12 (76-86) msec, 71 +/- 11 (64-79) msec, 72 +/- 9 (65-79) msec, respectively; CA vs. control, P = 0.04; CA vs. NCA, P = 0.04; NCA vs. control, P = 0.91]. T1-RT was best suited to discriminate between the groups as shown by logistic regression. A cut-off value of >or=1273 milliseconds for T1-RT was defined using receiver-operator characteristics-analysis to establish the diagnosis of CA with a high sensitivity (84%) and specificity (>89%). CONCLUSIONS: Measurement of T1 and T2 RT is a novel approach for noninvasive evaluation of CA. MR-relaxometry might improve diagnostic reliability of magnetic resonance imaging for evaluation of cardiac involvement in systemic amyloidosis.     

心肌淀粉样变性的临床表现及MRI特征

目的 探讨心肌淀粉样变性临床表现及MRI特征.方法 回顾性分析5例经组织病理检查确诊的心肌淀粉样变性患者,其中3例经心脏移植,2例经心内膜活检证实.5例患者均经心电图、X线胸片、超声心动图和MR检查.结果 5例均确诊为心肌淀粉样变性,男女比例为4∶1,5例患者均有心电图异常;X线胸片3例有肺淤血,5例心脏增大,3例伴有少至中、大量胸腔积液;超声心动图示心房扩大,左心室壁肥厚,心室舒张受限,部分出现心肌回声增强;MRI表现为左心室壁普遍增厚,但以室间隔增厚为主,左心室射血分数32.5%±15.0%,限制性心室舒张期充盈受限;延迟增强MRI 4例表现为全心心内膜下为主的弥漫性粉尘样强化,同时累及乳头肌,其中3例患者室间隔左、右心室壁心内膜下均出现强化,在室间隔形成"斑马征",1例表现左心室透壁性强化,自内向外强化程度渐弱.结论 MRI"一站式"扫描能够全面显示心肌淀粉样变性心脏结构和功能变化,心肌弥漫性粉尘样强化和"斑马征",在心肌淀粉样变性诊断中具有很高的参考价值.     

Effect of long-term atrial-demand ventricular pacing on cardiac sympathetic activity

It has been shown that either dual-chamber or atrial pacing may be better than ventricular single-chamber pacing, but the long-term effect of dual-chamber pacing on cardiac sympathetic activity is unclear. The aim of this study was to assess the effect of long-term dual-chamber pacing on cardiac sympathetic activity, compared with atrial pacing and unpaced individuals. We studied 11 patients with dual-chamber pacemakers (Group D), nine with atrial single-chamber pacemakers (Group A) over the long term (mean 44 +/- 36 months) and 10 normal individuals without cardiac pacing. All underwent myocardial 123I-metaiodobenzylguanidine (MIBG) imaging to assess cardiac sympathetic activity. The heart-to-mediastinum (H/M) MIBG uptake ratio and the MIBG washout rate from the myocardium were calculated. Echocardiography was performed in all patients with cardiac pacing to assess left ventricular function. In Group D, the H/M ratio on delayed images was significantly lower than that of Group A (1.82 +/- 0.51 vs 2.56 +/- 0.50, P < 0.001) and normal individuals (2.65 +/- 0.35, P < 0.05). The myocardial MIBG washout rate of Group D was significantly higher than that of either Group A (52 +/- 13% vs 36 +/- 8%, P < 0.01) or normal individuals (31 +/- 7%, P < 0.05). Neither the H/M ratio nor MIBG washout rate differed significantly between patients in Group A and normal individuals. Furthermore, the echocardiographic parameters did not differ significantly between the two pacing groups. We conclude that long-term ventricular pacing, even in the presence of atrioventricular synchrony, accelerates cardiac sympathetic activity without deteriorating left ventricular function.     

Gated SPECT findings revealing diastolic dysfunction in acute hypothyroidism

PURPOSE: The purpose of this study was to assess left ventricular (LV) function by gated SPECT in acute hypothyroidism. METHODS: Thirty-eight acute hypothyroid patients without any cardiac disease and 40 healthy controls underwent gated SPECT at rest. Fourteen patients had a second examination during thyroxine replacement therapy. Gated SPECT was performed using Tc-99m sestamibi with 16 frames per cardiac cycle. The LV end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR), and time to peak filling (TTPF) were measured by quantitative gated SPECT (QGS). Systolic wall thickening/motion was determined in 5 myocardial segments. RESULTS: Hypothyroid patients exhibited a decrease in PFR (222 +/- 52 EDV/s) and prolongation of TTPF (194 +/- 32 msec) as compared with controls (247 +/- 41 EDV/s and 179 +/- 17 msec, respectively; P < 0.05). During thyroxine therapy, the mean values for EDV (74 +/- 21 mL) and PFR (265 +/- 64 EDV/s) increased significantly in 14 follow-up patients (pretreatment values 67 +/- 18 mL and 219 +/- 50 EDV/s, respectively; P < 0.05). A significant difference was detected in the mean TTPF between the thyroxine group and the controls (195 +/- 35 msec vs 179 +/- 17 msec; P < 0.05). No significant differences were found in wall thickening and motion values (P > 0.05). CONCLUSION: Gated SPECT findings revealed diastolic dysfunction as indicated by a decrease in PFR and a prolongation in TTPF in patients with acute hypothyroidism.     

Quantitative assessment of myocardial T2 relaxation times in cardiac amyloidosis

Purpose

To evaluate cardiac MRI (CMR) in the diagnosis of cardiac amyloidosis by comparing the T2 relaxation times of left ventricular myocardium in a pilot patient group to a normal range established in healthy controls.

Materials and Methods

Forty‐nine patients with suspected amyloidosis‐related cardiomyopathy underwent comprehensive CMR examination, which included assessment of myocardial T2 relaxation times, ventricular function, resting myocardial perfusion, and late gadolinium enhancement (LGE) imaging. T2‐weighted basal, mid, and apical left ventricular slices were acquired in each patient using a multislice T2 magnetization preparation spiral sequence. Slice averaged T2 relaxation times were subsequently calculated offline and compared to the previously established normal range.

Results

Twelve of the 49 patients were confirmed to have cardiac amyloidosis by biopsy. There was no difference in mean T2 relaxation times between the amyloid cases and normal controls (51.3 ± 8.1 vs. 52.1 ± 3.1 msec, P = 0.63). Eleven of the 12 amyloid patients had abnormal findings by CMR, eight having LGE involving either ventricles or atria and four demonstrating resting subendocardial perfusion defects.

Conclusion

CMR is a potentially valuable tool in the diagnosis of cardiac amyloidosis. However, calculation of myocardial T2 relaxation times does not appear useful in distinguishing areas of amyloid deposition from normal myocardium. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.     

Combined T1-T2 mapping of human femoro-tibial cartilage with turbo-mixed imaging at 1.5T

PURPOSE: To evaluate the influence of Gd-DTPA on cartilage T2 mapping using turbo-mixed (tMIX) imaging, and to show the possible usefulness of the tMIX technique for simultaneously acquiring T1 and T2 information in cartilage. MATERIALS AND METHODS: Twenty volunteers underwent MRI of the knee using the tMIX sequence before and after gadolinium administration. T1 and T2 maps were calculated. The mean T1 was determined on the pre- and postcontrast T1 maps. T2 relaxation values before and after gadolinium administration were statistically analyzed. RESULTS: The obtained relaxation values are in correspondence with previously published data. The mean T1 before gadolinium administration was 449 msec +/- 34.2 msec (SD), and after gadolinium administration it was 357 msec +/- 55.8 msec (SD). The postcontrast T1 relaxation range was 221.5-572.8 msec. The mean T2 of the precontrast T2 maps was 34.2 msec +/- 3.1 msec (SD), and the mean T2 of the postcontrast T2 maps was 32.5 msec +/- 3.1 msec (SD). These are statistically significant different values. A correction for the postcontrast T2 values, using a back-calculation algorithm, yielded a 98% correlation with the precontrast T2 values. CONCLUSION: The absolute difference of pre- and postcontrast T2 is very small and is ruled out using the back-calculation algorithm. Combined T1-T2 tMIX cartilage mapping is a valuable alternative for separate T1 and T2 cartilage mapping.     

心肌淀粉样变性的MRI与超声心动图诊断价值

目的 探讨心肌淀粉样变性的MRI与超声心动图诊断价值.方法 回顾性分析11例经病理活检证实的心肌淀粉样变性患者的MR和超声心动图检查结果.结果 MRI和超声心动图示心肌淀粉样变性患者中,11例均存在不同程度的左心室、室间隔轻度增厚,5例房间隔轻度增厚,7例左心室心肌质量增加,7例左心房增大,6例左心室射血分数减低,10例舒张功能减低,多伴随心包积液、胸腔积液.8例MRI延迟增强显示特征性的弥漫性、广泛性心内膜下至透壁性延迟强化.6例超声心动图显示心肌回声增强,呈磨玻璃样改变,并可见散在颗粒样斑点状强回声.结论 超声心动图具有较好的初步诊断价值,延迟增强MRI能为心肌淀粉样变性诊断及鉴别诊断提供更为全面、丰富的信息.     

Acute myocardial infarction: MR evaluation in 29 patients

This study evaluated the ability of MR to identify and characterize the region of myocardial infarction in humans. Twenty-nine patients, all with ECG and enzyme rises consistent with an acute myocardial infarction, were studied by MR 3-17 days from the onset of acute chest pain. Four patients were excluded because of inability to acquire adequate MR studies. For comparison, 20 normal subjects were studied who also had gated MR examinations. The site of infarction was visualized in 23 patients as an area of high signal intensity in relation to the normal myocardium, a contrast that increased on the second-echo image. The regions of abnormal signal intensity corresponded to the anatomic site of infarction as defined by the ECG changes. The mean T2 relaxation time of the infarcted myocardium (79 +/- 22 msec) was significantly prolonged in comparison with the mean T2 (43.9 +/- 9 msec) of normal myocardium (p less than .01). The mean percentage of contrast (intensity difference) between normal and infarcted myocardium was much greater on the second-echo images (65.6 +/- 34.0%) than the first-echo images (27.5 +/- 18.7%). In the normal subjects there was no difference in T2 between the anterolateral (40.3 +/- 5.7 msec) and septal (39.5 +/- 7.4 msec) regions, and percentages of contrast between these two regions of myocardium on the first-echo (9.1 +/- 7.4%) and second-echo (15.0 +/- 13.3%) images were similar. Thus, MR can be used to directly visualize acute infarcts. However, it has several pitfalls, including the necessity to differentiate signal from slowly flowing blood in the ventricle, from increased signal from a region of infarction and artifactual variation of signal intensity in the myocardium due to respiratory motion or residual cardiac motion.     

Sodium T2* relaxation times in human heart muscle

PURPOSE: To determine sodium transverse relaxation (T2*) characteristics for myocardium, blood and cartilage in humans. METHODS: T2* measurements were performed using a 3D ECG-gated spoiled gradient echo sequence. A 1.5 Tesla clinical scanner and a 23Na heart surface coil were used to examine eight healthy volunteers. In biological tissue, the sodium 23 nucleus exhibits a two-component T2 relaxation due to the spin 3/2 and its quadrupolar nature. The long T2* components of normal myocardium, blood, and cartilage were quantified. For myocardium, the T2* was determined separately for the septum, anterior wall, lateral wall, and posterior wall. RESULTS: The long T2* relaxation time components of 13.3 +/- 4.3 msec (septum 13.9 +/- 3.2 msec, anterior wall 13.8 +/- 5.4 msec, lateral wall 11.4 +/- 4.1 msec, posterior wall 14.1 +/- 3.7 msec), 19.3 +/- 3.3 msec, and 10.2 +/- 1.6 msec, were significantly different for myocardium, blood, and cartilage, respectively (P < 0.00001, Friedman's ANOVA). CONCLUSION: Measurement of 23Na T2* relaxation times is feasible for different regions of the human heart muscle, which might be useful for the evaluation of cardiac pathologies.     

Concentrations of human cardiac phosphorus metabolites determined by SLOOP 31P NMR spectroscopy.

Human cardiac 31P nuclear magnetic resonance (NMR) spectra are usually quantified in relative terms, i.e., the ratio of metabolite signals is calculated. If 31P NMR spectroscopy of the heart is to emerge as a clinically relevant diagnostic modality, reliable quantification of absolute concentrations of 31P metabolites is required. We applied spectral localization with optimal point spread function (SLOOP) 31P NMR spectroscopy to measure absolute concentrations of phosphocreatine (PCr) and adenosine triphosphate (ATP) in human myocardium. The accuracy of the quantification was first validated in a phantom study. Seven healthy volunteers (aged 19-29 years) were then examined at 1.5 T using a nominal spatial resolution of 25 mL. SLOOP allowed us to obtain localized spectra from compartments anatomically matched to the left ventricular wall. The a priori knowledge of the anatomical structure was obtained from 1H images. The spatially varying effects of saturation, off-resonance, and sensitivity were considered during the reconstruction process. Metabolites were quantified with reference to an external 31P standard. Concentrations of 9.0 +/- 1.2 and 5.3 +/- 1.2 mmol/kg wet wt (mean +/- SD, n = 9) were determined for PCr and ATP in normal heart, respectively. The influence of nuclear Overhauser enhancement on metabolite quantification is discussed.     

High-resolution, multicontrast three-dimensional-MRI characterizes atherosclerotic plaque composition in ApoE-/- mice ex vivo

PURPOSE: To systematically investigate intrinsic MR contrast mechanisms that would facilitate plaque characterization and quantification in the aortic root and brachiocephalic artery of ApoE-/- mice ex vivo. MATERIALS AND METHODS: To establish unambiguous MR parameters for routinely analyzing atherosclerotic plaque ex vivo at 11.7 T, relaxation times of plaque components were quantitatively assessed. Magnetization transfer and lipid-proton three-dimensional MR imaging was investigated for visualization of collagen- and lipid-rich plaque regions, respectively. A three-dimensional multiecho sequence with a spatial resolution of 47 x 47 x 63 microm was implemented providing a variable degree of T2-weighting. RESULTS: Relaxation time measurements showed clear tissue heterogeneity between atherosclerotic plaque components in the T2-values, but similar T1-values at 11.7 T (T1/T2 mean +/- SD; cellular plaque component: 1.2 +/- 0.3 seconds/26.3 +/- 0.4 msec; fibrofatty plaque component: 1.1 +/- 0.2 seconds/13.7 +/- 2.0 msec). The three-dimensional multiecho sequence allowed the calculation of the intrinsic proton density and T2-maps. The sum of the multiecho data provided strong T2-weighting that facilitated quantification of various components of atherosclerotic plaque in the mouse aortic root and correlated well with histology (P < 0.0001). CONCLUSION: High-resolution MRI allows for accurate classification and quantification of atherosclerotic plaque components in the aortic root of mice.     

MRI of splenomegaly

Splenomegaly was evaluated by a 0.1 T MR system using multi-echo SE image. (TR = 1500 msec., TE = 40, 80 and 120 msec.) Calculated measurement of T2 relaxation time was obtained. Material consists of 32 cases including 14 liver cirrhosis, 3 chronic myelocytic leukemia, 1 malignant lymphoma and 14 normals. 1) T2 value of normal spleen measured 113.7 +/- 5.68 msec. 2) Splenomegaly due to congestion had the prolonged T2 value of 122.6 +/- 10.25 msec. 3) T2 value of splenomegaly with malignant cell infiltration such as leukemia and lymphoma were shorter than normal spleen. Good histological correlation was obtained in MRI findings of splenomegaly due to congestion and malignant cell infiltration.     

Myocardial infarct size quantification by MR imaging early after coronary artery occlusion in dogs

The feasibility of using magnetic resonance (MR) imaging to estimate myocardial infarct size was explored in an in vitro model using only the inherent differences in contrast between infarcted and noninfarcted myocardium. Eight dogs underwent coronary occlusion; their hearts were removed 6 hours later. Estimates of T2 for normal and infarcted myocardium were derived from MR images. Infarct size was quantified anatomically using triphenyltetrazolium-chloride (TTC) staining and compared with MR estimates. The T2 values derived from the images clearly discriminated between infarcted (126 +/- 22 msec) and normal myocardium (88 +/- 10 msec, P less than .05), providing images with good contrast between normal and infarcted myocardium. Comparable differences in T2 values were also noted from spectrometric determinations. Estimates of infarct size by MR imaging compared well with TTC estimates (r = 0.98) over a wide range of infarct sizes from 3% to 29% of the left ventricular mass. These results suggest the potential for in vivo quantification of infarct size based on the inherent contrast difference between infarcted and normal myocardium.     

Evaluation of sodium T1 relaxation times in human heart

PURPOSE: To evaluate the sodium longitudinal relaxation (T(1)) characteristics for myocardium and blood in humans. MATERIALS AND METHODS: Eleven healthy volunteers were examined by using a (23)Na heart surface coil at a 1.5 T clinical scanner equipped with a broadband spectroscopy option. (23)Na MR measurements were performed by using a three-dimensional spoiled gradient echo sequence (in-plane resolution, 3.5 mm x 7 mm; slice thickness, 24 mm; TE, 3.1 msec; bandwidth, 65 Hz/pixel; TR, 21 to 150 msec). RESULTS: Longitudinal T(1) relaxation time components were 31.6+/-7.0 msec and 31.1+/-7.5 msec for myocardium and blood, respectively. CONCLUSION: (23)Na T(1) relaxation times of myocardium and blood can be determined in humans. The results are in agreement with values obtained from animal studies.     

Measurement of regional left ventricular function using labelled magnetic resonance imaging

A technique for assessing regional left ventricular function using magnetic resonance imaging is described. Spatial modulation of magnetization (SPAMM) is effected immediately before images are obtained at various intervals during the cardiac cycle using a modified field echo even rephasing technique (FEER). By performing such modulation in two planes, a grid pattern of labelling can be produced across the image. On the resulting labelled short axis images of the left ventricle, the systolic increase in thickness (thickening) and decrease in length (shortening) of different regions of myocardium can then be measured. The findings in five normal volunteers are presented. Radial shortening was twice as great in the endocardium (mean 20.4%, standard deviation (SD) 5.7) than in the epicardium (mean 10.2%, SD 5.5) and appears to offer more promise as a marker of regional function than simple thickening (mean 9.8%, SD 13.6).     

T 1 rho-relaxation mapping of human femoral-tibial cartilage in vivo

PURPOSE: To demonstrate the in vivo feasibility of measuring spin-lattice relaxation time in the rotating frame (T(1rho)); and T(1rho)-dispersion in human femoral cartilage. Furthermore, we aimed to compute the baseline T(1rho)-relaxation times and spin-lock contrast (SLC) maps on healthy volunteers, and compare relaxation times and signal-to-noise ratio (SNR) with corresponding T(2)-weighted images. MATERIALS AND METHODS: All MR imaging experiments were performed on a 1.5 T GE Signa scanner (GEMS, Milwaukee, WI) using a custom built 15-cm transmit-receive quadrature birdcage radio-frequency (RF) coil. The T(1rho)-prepared magnetization was imaged with a single-slice two-dimensional fast spin-echo (FSE) pulse sequence preencoded with a three-pulse cluster consisting of two hard 90 degrees pulses and a low power spin-lock pulse. T(1rho)-dispersion imaging was performed by varying the spin-lock frequency from 100 to 500 Hz in five steps in addition to varying the length of the spin-lock pulse. RESULTS: The average T(1rho)-relaxation times in the weight-bearing (WB) and nonweight-bearing (NWB) regions of the femoral condyle were 42.2 +/- 3.6 msec and 55.7 +/- 2.3 msec (mean +/- SD, N = 5, P < 0.0001), respectively. In the same regions, the corresponding T(2)-relaxation times were 31.8 +/- 1.5 msec and 37.6 +/- 3.6 msec (mean +/- SD, N = 5, P < 0.0099). T(1rho)-weighted images have approximately 20%-30% higher SNR than the corresponding T(2)-weighted images for similar echo time. The average SLC in the WB region of femoral cartilage was 30 +/-4.0%. Furthermore, SLC maps provide better contrast between fluid and articular surface of femoral-tibial joint than T(1rho)-maps. The T(1rho)-relaxation times varied from 32 msec to 42 msec ( approximately 31%) in the WB and 37 msec to 56 msec ( approximately 51%) in NWB regions of femoral condyle, respectively, in the frequency range 0-500 Hz (T(1rho)-dispersion). CONCLUSION: The feasibility of performing in vivo T(1rho) relaxation mapping in femoral cartilage at 1.5T clinical scanner without exceeding Food and Drug Administration (FDA) limits on specific absorption rate (SAR) of RF energy was demonstrated.     

MR imaging relaxation times of abdominal and pelvic tissues measured in vivo at 3.0 T: preliminary results

PURPOSE: To measure T1 and T2 relaxation times of normal human abdominal and pelvic tissues and lumbar vertebral bone marrow at 3.0 T. MATERIALS AND METHODS: Relaxation time was measured in six healthy volunteers with an inversion-recovery method and different inversion times and a multiple spin-echo (SE) technique with different echo times to measure T1 and T2, respectively. Six images were acquired during one breath hold with a half-Fourier acquisition single-shot fast SE sequence. Signal intensities in regions of interest were fit to theoretical curves. Measurements were performed at 1.5 and 3.0 T. Relaxation times at 1.5 T were compared with those reported in the literature by using a one-sample t test. Differences in mean relaxation time between 1.5 and 3.0 T were analyzed with a two-sample paired t test. RESULTS: Relaxation times (mean +/- SD) at 3.0 T are reported for kidney cortex (T1, 1,142 msec +/- 154; T2, 76 msec +/- 7), kidney medulla (T1, 1,545 msec +/- 142; T2, 81 msec +/- 8), liver (T1, 809 msec +/- 71; T2, 34 msec +/- 4), spleen (T1, 1,328 msec +/- 31; T2, 61 msec +/- 9), pancreas (T1, 725 msec +/- 71; T2, 43 msec +/- 7), paravertebral muscle (T1, 898 msec +/- 33; T2, 29 msec +/- 4), bone marrow in L4 vertebra (T1, 586 msec +/- 73; T2, 49 msec +/- 4), subcutaneous fat (T1, 382 msec +/- 13; T2, 68 msec +/- 4), prostate (T1, 1,597 msec +/- 42; T2, 74 msec +/- 9), myometrium (T1, 1,514 msec +/- 156; T2, 79 msec +/- 10), endometrium (T1, 1,453 msec +/- 123; T2, 59 msec +/- 1), and cervix (T1, 1,616 msec +/- 61; T2, 83 msec +/- 7). On average, T1 relaxation times were 21% longer (P <.05) for kidney cortex, liver, and spleen and T2 relaxation times were 8% shorter (P <.05) for liver, spleen, and fat at 3.0 T; however, the fractional change in T1 and T2 relaxation times varied greatly with the organ. At 1.5 T, no significant differences (P >.05) in T1 relaxation time between the results of this study and the results of other studies for liver, kidney, spleen, and muscle tissue were found. CONCLUSION: T1 relaxation times are generally higher and T2 relaxation times are generally lower at 3.0 T than at 1.5 T, but the magnitude of change varies greatly in different tissues.     

Assessment of left ventricular perfusion, volumes, and motion in mice using pinhole gated SPECT.

Quantitative functional normal data should be a prerequisite before applying SPECT in murine models of cardiac disease. Therefore, we investigated the capability of in vivo pinhole gated SPECT for establishment of a reference database for left ventricular myocardial perfusion, volumes, and motion in normal mice. METHODS: A small-animal dedicated pinhole gamma-camera with a field of view of 17 cm and a focal distance of 12 cm was used with a 1.5-mm pinhole and a 2.5-cm radius of rotation. Phantoms were designed to test spatial resolution and microvolume measurements of accuracy. Eight adult normal mice (CD1) were studied using a heated mixture of air (0.3 L/min) and 1.5%-2.5% isoflurane for anesthesia. For myocardial perfusion, 350-450 MBq of (99m)Tc-tetrofosmin were used in 0.15-0.25 mL. Gated acquisitions (8 or 10 time bins per cardiac cycle) were obtained using a 180 degrees circular arc and 48 anterior projections of 300 R-R intervals. Image reconstruction was done using a specific Algebraic Reconstruction Technique (ART) cone-beam algorithm. For quantification, reconstructed images were processed using standard nuclear medicine software. RESULTS: Millimetric spatial resolution and volume calibration linear relationships (r(2) = 0.99) in the 10- to 100-muL range were obtained in phantoms and used to scale in vivo volume values. In mice, left ventricular perfusion was lower in the apex (65% +/- 6%) versus lateral (72% +/- 5%), inferior (74% +/- 5%), septum (75% +/- 4%), and anterior (74% +/- 2%) walls. The left ventricular ejection fraction was 60% +/- 9%, end-diastolic volume was 50 +/- 8 muL, end-systolic volume was 20 +/- 6 muL, stroke volume was 29.5 +/- 6 muL, and cardiac output was 9.6 +/- 1.6 mL/min. Wall thickening was higher in the apex (47% +/- 12%) versus lateral (30% +/- 9%), inferior (33% +/- 8%), septum (37% +/- 10%), and anterior (33% +/- 10%) walls. CONCLUSION: This work shows that in vivo pinhole gated SPECT can be used for assessment of left ventricular perfusion, volumes, and cardiac function in normal mice.     

法布里病累及心脏的临床及MR特征分析

目的:探讨法布里病（AFD）累及心脏的临床及心脏MR（CMR）特征。方法:回顾性纳入2018年1月至2021年3月阜外医院经基因检测或病理确诊的AFD患者8例（AFD组）,其中男3例、女5例,年龄26~60（50±11）岁;同时纳入性别、年龄匹配的肥厚型心肌病（HCM）患者16例（HCM组）和健康对照者16名（正常组）...     

Recent myocardial infarction: assessment with unenhanced T1-weighted MR imaging

The purpose of the study was to prospectively evaluate a T1-weighted technique for detection of myocardial edema resulting from recent myocardial infarction (MI) or intervention. This study was HIPAA compliant and institutional review board approved. Fifteen men and one woman (mean age, 57.8 years+/-11.5 [standard deviation]) were examined with T1-weighted magnetic resonance (MR) imaging and inversion-recovery cine pulse sequence in two groups, recent MI and chronic MI, and gave informed consent. T1 relaxation times of MI and adjacent myocardium were compared (Student t test and correlation analysis). In patients with recent MI, areas of myocardial edema were well depicted with T1-weighted MR imaging. T1 relaxation times of recent infarcts were longer than those of older MIs (925 msec+/-169 vs 551 msec+/-107, P<.001). From local edema, T1 relaxation time of infarcted myocardium is increased, may remain elevated for 2 months, and enables imaging with T1-weighted techniques.