Michinobu Nagao

Peri-infarct dysfunction in post-myocardial infarction: assessment of 3-T tagged and late enhancement MRI

ObjectiveTo determine LV function at different distances from myocardial infarction (MI) by using 3-T tagged MRI and late gadolinium enhancement (LGE).MethodsCardiac MR images were acquired from 21 patients with previous MI. The harmonic phase (HARP) method was used to calculate radial and circumferential strain (RS, CS). The two strains were synchronised by subtracting the CS from the RS at the same time, and this was defined as the efficient strain (ES). Peak strain (P-RS, P-CS, P-ES) and time to peak strain (T-RS, T-CS, T-ES) were used as estimates of contractile function. Based on the presence of LGE, myocardium was classified into infarct, border zone, adjacent and remote areas.ResultsP-RS and P-ES were significantly greater for remote than for adjacent and infarct areas. P-CS values were significantly greater for remote and border zone than for infarct areas. T-RS and T-ES were significantly shorter for remote and border zone than for infarct areas. T-CS was significantly shorter for border zone than for infarct areas.ConclusionContractile dysfunction demonstrated by peak strain was correlated with location at different distances from the infarct. In the border zone, contractile deformation was characterised as earlier T-RS, T-CS and T-ES and greater P-CS than in the infarct area.

Myocardial ischemia in acute coronary syndrome: assessment using 64-MDCT.

OBJECTIVEnWe investigated the performance of 64-MDCT myocardial imaging in assessing myocardial ischemia in acute coronary syndrome (ACS).nnnMATERIALS AND METHODSnCardiac CT was performed in 35 patients with ACS: 24 patients with acute myocardial infarction (AMI) and 11 patients with unstable angina pectoris (UAP). We reconstructed 2D myocardial images at diastolic and systolic phases using the same raw data as those used for coronary CT angiography. The CT number in the myocardium was used as an estimate of ischemia. The myocardium was shown using a color scale that depicts faint low-density areas more clearly than gray scale. We evaluated the variations in myocardial enhancement during the cardiac cycle in the territory of the culprit lesion. In addition, we classified patients on the basis of the transmurality of myocardial enhancement and examined whether this feature correlates with myocardial damage.nnnRESULTSnMyocardial imaging at systole showed myocardial hypoenhancement in territories of the culprit lesion in 91% of patients with ACS, 96% of patients with AMI, and 75% of patients with UAP. The hypoenhancement areas at systole tended to be more extensive than those at diastole. The transmural extent of hypoenhancement at systole correlated with myocardial damage, which was shown by myocardial biomarkers.nnnCONCLUSIONnCT myocardial imaging can be used to assess myocardial ischemia in the appropriate region of ACS with high sensitivity.

Heterogeneity of posterior limbic perfusion in very early Alzheimer's disease

PURPOSEnThis study was designed to quantify the heterogeneity of cerebral perfusion on SPECT images in elderly controls and Alzheimers disease (AD) patients in mild stage using a three-dimensional fractal analysis (3D-FA).nnnMATERIAL AND METHODnSeventy-five patients with possible and probable AD based on the NINCDS/ADRDA criteria, and thirty-one elderly controls underwent 99mTc-HMPAO SPECT scanning. Dementia severity was assessed using the clinical dementia rating (CDR). Patients with CDR scores of 0.5 (n=33) were classified as very early and those with CDR 1 (n=42) as early. We delineated the SPECT images using 2 cutoffs (35% and 50% cutoffs of the maximal voxel radioactivity) and measured the number of voxels in the areas included by the contours obtained with each cutoff level. The fractal dimension (FD) was calculated by relating the logarithms of cutoff level and the number of voxels. Posterior limbic images were reconstructed at 30 degrees positive to the coronal plane, and posterior limbic FD was calculated.nnnRESULTnPosterior limbic FD for early AD, very early AD, and control groups were 1.03+/-0.16, 1.02+/-0.17, and 0.87+/-0.14 (P=0.001 versus early AD group, P=0.001 versus very early AD). Use of the posterior limbic FD and the ratio of posterior limbic FD to total FD separated very early AD patients from controls with a sensitivity of 76% and a specificity of 81%.nnnCONCLUSIONn3D-FA indicated significant differences in the heterogeneity of CBF distribution between patients with AD in mild stage and elderly controls. Posterior limbic FD may be useful for easily and objectively distinguishing patients with very early AD from aging people.

Relationship between regional severity of emphysema and coronary heart disease

We analyzed the relationship between regional severity of emphysema, which was evaluated by three-dimensional fractal analysis (3D-FA) of Technegas SPECT images, and coronary heart disease (CHD). For 22 patients with emphysema who underwent Technegas SPECT, we followed up CHD events. The follow-up period was 5.4±0.5 (mean ±SD) years. We defined the upper-lung fractal dimension (U-FD) and lower-lung fractal dimension (L-FD) obtained with 3D-FA of Technegas SPECT images as the regional severity of emphysema. FD became greater with the progression of emphysematous change. During the follow-up period, CHD events occurred in 6 (27%) of the 22 patients. The ratio of U-FD to L-FD for patients with CHD events (0.87±0.22) was significantly smaller than for patients without CHD events (1.52±0.38) (p=0.0015). These findings suggest that severer emphysema in the lower lung indicates a higher risk of CHD than that in the upper lung.