A new quantitative method for the analysis of cardiac perfusion tomography (SPET): validation in post-infarct patients treated with thrombolytic therapy

In this study a new method for assessment of perfusion defects (PDs) derived from myocardial perfusion tomograms was evaluated in patients treated with thrombolytic therapy. Using global constraints and dynamic programming, a model-based delineation algorithm defined myocardial borders, the basal plane and absolute and relative PD size in 49 thallium-201 chloride (²⁰¹TL CL) and 60 technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) tomograms. Tomographic (single-photon emission tomography: SPET) and planar quantification of PDs was compared to enzymatic infarct size as well as to global (LVEF) and regional ventricular function (RWM) obtained by contrast angiography. The algorithm delineated the myocardium and the valve plane in most cases, even when large PDs were present. Manual correction of the automatic delineation of the basal plane was necessary in less than 20% of the studies. Using ²⁰¹T1 C1, LVEF correlated better with tomographic PD (r=–0.67) than with planar PD (r=–0.54). Comparing planar to tomographic imaging using ^99mTc-MIBI, a higher correlation with enzymatic infarct size (r=0.73 vs 0.57) and with global ventricular function (r=–0.64 vs –0.52) was found when tomographic techniques were used. No close correlation between PD and RWM was found. The beneficial effect of thrombolysis was shown by a significant difference of PD in patients with open versus occluded infarct-related vessels. It can be concluded that this new automated algorithm for quantification of SPET perfusion defect size provides a useful tool in evaluating thrombolytic therapy.     

Relationship of infarct size and severity versus left ventricular ejection fraction and volumes obtained from 99mTc-sestamibi gated single-photon emission computed tomography in patients treated with primary percutaneous coronary intervention

The current technique of choice for perfusion imaging is gated single-photon emission computed tomography (SPECT), which allows the simultaneous assessment of perfusion and left ventricular (LV) function. We examined the relationships of infarct size and severity with LV ejection fraction (EF) and volumes in 215 myocardial infarction patients treated with primary percutaneous coronary intervention within 6 h of symptom onset. Patients were studied with resting gated SPECT 1 month later. Infarct size was expressed as LV percent, and infarct severity as the lowest activity ratio within the defect. LVEF, end-diastolic (ED) and end-systolic (ES) volume indexes (Vi) were calculated with commercial software. There was a significant correlation between infarct size and LVEF (r=–0.68, P<0.00001), EDVi (r=0.53, P<0.00001), and ESVi (r=0.62, P<0.00001). Slightly lower correlations were demonstrated using infarct severity. LVEF and volumes were related to infarct location. A significantly higher correlation was observed between infarct size and LVEF in anterior than in non-anterior infarctions (r=–0.75 vs –0.60, P<0.05). In multivariate analysis, infarct size and infarct location were significant predictors of LVEF (R²=0.50) and ESV (R²=0.40). Infarct size and infarct severity were significant predictors of EDVi (R²=0.29). Infarct size (and severity) and LVEF (and volumes) derived from a single gated SPECT study correlate closely. Infarct location influences this relationship, with anterior infarctions showing a lower LVEF than inferior or lateral ones of the same extent.     

Quantitative analysis of cardiac function: Comparison of electro-cardiogram dual gated single photon emission tomography,planar radionuclide ventriculogram and contrast ventriculography in the determination of LV volume and ejection fraction

A dual gated tomography (DGT) program for end systolic and end diastolic acquisition and subsequent processing for calculation of LVEF, end diastolic and end systolic volumes (EDV, ESV) has been evaluated in 20 healthy volunteers (25 years–40 years) and 45 patients (25 years–60 years): 20 with ischaemic heart disease and 25 with valvular heart disease (VHD). All had biplane multigated blood pool (MUGA) studies in the 40° LAO projection using in vivo ^99mTc- RBCs, immediately followed by DGT. The results in the patients group were correlated with contrast ventriculography (CV). In the volunteer group, the normal values for LVEF, EDV and ESV measured with DGT were found to be 63%±10%, 91 ml±6 ml and 30 ml±6 ml and r value for the LVEF=0.91 compared with MUGA. In the IHD group, r values compared with CV were 0.915 and 0.97 for the EDV and ESV and 0.934 for the LVEF. Compared with the MUGA, the r value for LVEF was 0.883. In the VHD group, r values were 0.98 for both the EDV and ESV and 0.948 for the LVEF (P<0.002) compared with CV and 0.789 for the LVEF compared with the MUGA. We feel that DGT is an accurate and reproducible technique for LV function measurements.     

A new method for quantification of pulmonary thallium uptake in myocardial SPECT studies

Quantified pulmonary thallium 201 (TI) uptake was assessed in 32 normal subjects and 66 patients with suspected coronary artery disease (CAD) by a new method utilizing SPECT acquisition data. In 26 subjects pulmonary uptake was assessed with both SPECT and planar techniques. Pulmonary/myocardial (PM) ratios for the whole right lung (PM1) and for the upper left lung (PM2) were computed and compared with stress test, coronary angiography, radionuclide angiography (ERNA), and quantified TI single photon emission computed tomography (SPECT) results. Excellent correlation between pulmonary uptake assessed by planar and SPECT technique was disclosed (r=0.92). The PM ratios (PM1/PM2) sensitivity and specificity in patients with CAD were 88%/92% and 60%/70%, for predicting perfusion abnormalities 90%/87% and 88%/88%, and an inverse correlation to left ventricular ejection fraction (LVEF) was found (r=–0.40/r=–0.37,P<0.01). Significant correlations to coronary angiography findings (r=0.54/r=0.49,P<0.001) and to number of vessel territories with abnormal perfusion (r=0.70/r=0.69,P< 0.001) were seen. Thus, pulmonary TI uptake can be assessed in SPECT studies. The new method's discriminative ability seems higher than that of the standard planar techniques currently employed. Positive correlations to coronary angiography findings and even stronger ones to perfusion abnormalities were observed.     

Comparison between vertical parallel hole collimator and 30° rotating slant hole collimator for assessing global and regional left ventricular function by radionuclide angiography

Left ventricular ejection fraction (LVEF) and regional wall motion abnormalities were determined in 40 patients (30 with coronary artery disease and 10 with valvular heart disease) using equilibrium radionuclide angiography. Scintigraphic acquisitions were collected in random order with 2 different collimators as follows: in anterior face (AF), left anterior oblique (25°–45° LAO) and 70° LAO, with a vertical parallel hole collimator (VTC), and in 25°–45° LAO and 65°–80° LAO with a 30° rotating slant hole collimator (RSHC), with the slant of the collimator directed towards the cardiac apex in both projections. Results were compared to contrast ventriculography (CV) performed in the 30° right anterior view (3 segments: anterior, apical, inferior) and in a 60° left anterior oblique view (3 segments: septal, apical and lateral). Radionuclide LVEF in both series was closely correlated with contrast ventriculographic LVEF (r=0.89, VTC vs CV and r=0.87, RSHC vs CV, respectively). Regional wall motion analysis was only performed among the 30 patients suffering from coronary heart disease. Eight contrast angiographic studies were normal and 22 abnormal. Global sensitivity and specificity were 100% and 63% with the VTC (3 false positives) and 91% and 87% with the 30° RSHC (2 false negatives and 1 false positive, P=ns). Agreement for the localisation of the regional wall motion abnormalities between CV and radionuclide angiography was 70.6% with the VTC and 71.2% with the RSHC (P=ns). Intensity of the regional wall motion abnormalities was assessed with the 30° RSHC as well as with the VTC (r=0.7 score CV vs score VTC and r=0.8 score CV vs score RSHC, P=ns). We conclude that the use of a rotating slant hole collimator associated with radionuclide ventriculography allows reliable determination of left ventricular ejection fraction and accurate assessment of regional wall motion abnormalities with only two projections while the vertical collimator requires three.     

A semi-automated method for edge detection in the evaluation of left ventricular function using ECG-gated single-photon emission tomography

Thallium-201 gated single-photon emission tomography (GSPET) of myocardium was performed at rest in 18 patients. Images were reconstructed to obtain end-diastolic (ED) and end-systolic (ES) images. The endocardial and epicardial edges of the left ventricle (LV) for the ED and ES images were defined for the mid-ventricular images of the short-axis slices, using a semi-automated method. LV wall thickness was measured for ED and ES images at 10° intervals. Mean LV thickness was derived as the mean of the LV thickness for the three mid-ventricular slices. The systolic thickening (ST) was derived as: mean LV thickness (ES) —mean LV thickness (ED). The systolic thickening ratio (STR) was defined as: ST/mean LV thickness (ED). LV cavity area was measured. The dilation ratio (DR) was defined as: [mean cavity area (ED) — mean cavity area (ES)]/mean cavity area (ED). LV ejection fraction (LVEF) was estimated using technetium-99m gated blood pool study. There was a linear correlation between LVEF and ST (r=0.85), LVEF and STR (r=0.77) and LVEF and DR (r=0.81). There was a strong correlation (r=0.85) between regional STR and regional percent count increase in 52 segments which did not have perfusion defects. As well as for the evaluation of myocardial perfusion, GSPET images can be of use for the assessment of LV function using an appropriate method for LV edge detection. Correspondence to: Kuang-Tao A. Yang     

Reproducibility of image interpretation in MRI of the prostate: application of the sextant framework by two different radiologists

The aim of this study was to reproduce prostate cancer (PCA) localization by MRI based on prostatic sextants (right and left base, middle, and apex) with minimal systematic error. Combined endorectal/body-phased-array-coil MRI of the prostate at 1.5 T was retrospectively evaluated twice, with an interval of more than 1 month, by each of two independent radiologists (R1 readings R11 and R12, and R2 readings R21 and R22) in 23 patients (age 51–75 years) who had radical prostatectomy within 1 month of MRI. PCA stage was pT2 in 14 patients, and pT3 in nine. Median Gleason score was 7 (range 5–9). Histopathology showed 83 sextants with PCA and 55 without. Reproducibility of sextant positions was within one MRI slice (3 mm) in over 80% of cases. For PCA localization, ROC analysis (AUC=0.584±0.048–0.724±0.043) yielded no significant intra-reader differences. R11 and R21 differed slightly (P=0.035). Intra-observer agreement (kappa=0.52–0.58) exceeded inter-observer agreement (kappa=0.35–0.45). Intra-observer Spearman correlation (r=0.72–0.74) exceeded inter-observer correlation (r=0.43–0.51) for sextants with PCA, but not for sextants without (r=0.69–0.74). Per-sextant localization and reporting provides a highly reliable framework in MRI of the prostate. MRI of the prostate should be followed up by the same radiologists to minimize systematic error of interpretation.     

Demonstration of disturbed free fatty acid metabolism of myocardium in patients with non-insulin-dependent diabetes mellitus as measured with iodine-123-heptadecanoic acid

Myocardial free fatty acid metabolism and left ventricular function were evaluated in 15 middle-aged patients with non-insulin-dependent diabetes mellitus (NIDDM) and in 8 healthy control subjects. The study subjects had no evidence of coronary heart disease on the basis of clinical history, exercise ECG or myocardial perfusion scintigraphy. During peak exercise, iodine-123 hepatadecanoic acid (HDA) was intravenously injected. Myocardial activity distribution of ¹²³I-HDA was measured 10, 30, and 50 min after exercise using single-photon emission tomography (SPET); and then further corrected by free ¹²³I-iodine. Venous blood samples were drawn for detecting the plasma activity of ¹²³I. The net extraction of ¹²³I-HDA into the myocardium was obtained by dividing the corrected tissue ¹²³I concentration by the integral of the plasma time activity curve. The net extraction was 0.40 ± 0.06 min^–1 (mean ± SD) patients with NIDDM and 0.38 ± 0.06 min^–1 in control subjects (P>0.1), respectively. The faster elimination rate of ¹²³I-HDA was found in patients with NIDDM (0.029±0.008 min^–1) than in control subjects (0.022±0.004 min^–1; P<0.01). There was no statistically significant difference in left ventricular ejection fraction (LVEF) at rest between patients with NIDDM (53±9%) and control subjects (56±2%), whereas the increase of LVEF during exercise remained lower in patients with NIDDM (3.4±8.2%) than in control subjects (11.8±5.8%; P<0.025). A significant correlation (r=0.64; P < 0.01) was found between the net extraction of ¹²³I-HDA and the change of LVEF, as well as with exercise load (r=0.68; P<0.01). In conclusion, evidence of an increased fatty acid utilization and triglyceride synthesis rate was observed in the diabetic myocardium. Offprint requests to: J.T. Kuikka     

Effect of mental stress on left ventricular ejection fraction and its relationship to the severity of coronary artery disease

To evaluate the relationship between the mental stress-induced decrease in left ventricular ejection fraction (LVEF) and the severity of exercise-induced ischaemia, 20 patients with stable coronary artery disease (CAD) underwent radionuclide ventriculography during mental stress testing and stress myocardial perfusion single-photon emission tomography (SPET). We also examined whether changes in haemodynamic and neurohormonal parameters are related to changes in LVEF during mental stress. The LVEF decreased from 54.8%ᆥ.7% to 49.8%ᆤ.2% with mental stress (P<0.0005). Ten of the 20 patients (50.0%) had a ̓% decrease in LVEF. The remaining ten patients had no or a <5% decrease in LVEF. There was a significant correlation between the change in LVEF during mental stress and the size of the reversible defect on stress myocardial perfusion SPET (r=-0.80, P<0.0005), with close regional correspondence (75% identical). This correlation was less strong in the 12 patients with a total defect score at rest of <10 (r=-0.69, P=0.014) than in the eight patients with a total defect score at rest of ⁶ (r=-0.94, P=0.001). The changes in blood pressure and heart rate were not significantly correlated with the change in LVEF, but the percent change in adrenaline concentration correlated with the change in LVEF. It is suggested that mental stress impairs systolic function by inducing transient myocardial ischaemia. The effect of neurohormonal responses during mental stress on LV systolic function may also be important in patients with CAD.     

Evaluation of a miniature CdTe detector for monitoring left ventricular function

A miniature CdTe probe interfaced to a microcomputer was used to measure left ventricular ejection fraction (LVEF) in 25 patients. LVEF obtained with the CdTe module, in the beat-to-beat mode, or the integrated gated mode agreed well with LVEF obtained with a gamma camera (r=0.80; r=0.82 respectively). Similarly, LVEF by CdTe probe agreed with LVEF obtained by gated equilibrium studies performed with a computerized NaI probe. The CdTe probe can provide comparable measurement of LVEF at a fraction of the cost of a cameracomputer system and, being small and lightweight, the CdTe probe is adaptable for monitoring patients in intensive care facilities.This work supported in part by USPHS Grant #GM 10548     

The relationship between cognitive impairment and in vivo metabolite ratios in patients with clinical Alzheimer's disease and vascular dementia: a proton magnetic resonance spectroscopy study

Previous magnetic resonance spectroscopy (MRS) studies have shown increased myo-inositol (MI) and decreased N-acetyl aspartate (NAA) levels in the parieto-occipital lobes of patients with Alzheimer's disease (AD) compared to those with other dementias and normal subjects. This study aimed to establish the quantitative relationship between metabolite ratios and degree of cognitive impairment in patients with mild to moderate AD and sub-cortical ischaemic vascular dementia (SIVD). Forty-four older people with clinical dementia were recruited from a memory clinic and followed up for 2.0–3.5 years; 20 cases were finally classified as probable AD, 18 as SIVD and 6 as mixed type. Mini Mental State Examination (MMSE) and short echo time single voxel automated MRS from the mesial parieto-occipital lobes were performed at the time of initial referral. Spearman rank correlation coefficients were calculated for MMSE scores and measured metabolite ratios MI/Cr, NAA/Cr, Cho/Cr and NAA/MI. The AD group showed a significant correlation between MMSE and NAA/MI (r=0.54, P=0.014) and NAA/Cr (r=0.48, P=0.033), and a negative, non-significant association with MI/Cr (r=–0.41, P=0.072). MI/Cr was negatively correlated with NAA/Cr (r=–0.51, P=0.021). Neither Cho/Cr ratios nor age correlated with cognitive function. The SIVD group showed no correlation between any of the measured metabolite ratios and MMSE score. This study reinforces the specific association between reduced NAA and increased MI levels in the parieto-occipital region and cognitive impairment in AD. MRS may have a role in evaluating disease progression and therapeutic monitoring in AD, as new treatments become available.     

Effect of temporal sampling on evaluation of left ventricular ejection fraction by means of thallium-201 gated SPET: comparison of 16- and 8-interval gating, with reference to equilibrium radionuclide angiography

Gated myocardial single-photon emission tomography (SPET) allows the evaluation of left ventricular ejection fraction (LVEF), but temporal undersampling may lead to systolic truncation and ejection fraction underestimation. The aim of this study was to evaluate the impact of temporal sampling on thallium gated SPET LVEF measurements. Fifty-five consecutive patients (46 men, mean age 62±12 years) with a history of myocardial infarction (anterior 31, inferior 24) were studied. All patients underwent equilibrium radionuclide angiography (ERNA) and gated SPET 4 h after a rest injection of 185 MBq (5 mCi) of thallium-201 using either 8-interval (group 1, n=25) or 16-interval gating (group 2, n=30). In group 2, gated SPET acquisitions were automatically resampled to an 8-interval data set. Projection data were reconstructed using filtered back-projection (Butterworth filter, order 5, cut-off 0.20). LVEF was then calculated using commercially available software (QGS). A higher correlation between gated SPET and ERNA was obtained with 16-interval gating (r=0.94) compared with the resampled data set (r=0.84) and 8-interval gating (r=0.71). Bland-Altman plots showed a dramatic improvement in the agreement between gated SPET and ERNA with 16-interval gating (mean difference: –0.10%±5%). Using multiple ANOVA, temporal sampling was the only parameter to influence the difference between the two methods. When using 8-interval gating, gated SPET LVEF was overestimated in women and underestimated in men (ERNA minus gated SPET = –4.0%±9.6% in women and 3.6%±7.6% in men, P=0.01). In conclusion, 16-interval thallium gated SPET offered the best correlation and agreement with ERNA, and should be preferred to 8-interval gated acquisition for LVEF measurement.     

Evaluation of biventricular ejection fraction with ECG-gated 16-slice CT: preliminary findings in acute pulmonary embolism in comparison with radionuclide ventriculography

This study aimed to assess the feasibility of cardiac global function evaluation during a whole-chest multi-slice CT (MSCT) acquisition in patients referred for suspicion of pulmonary embolism (PE), and to compare the results with planar equilibrium radionuclide ventriculography (ERNA). Ten consecutive haemodynamically stable patients (six female, four male; mean age 69.7 years; heart rate 65–99 bpm) with suspicion of PE underwent an MSCT and ERNA within a 6 h period. CT acquisition was performed after contrast medium injection by using 16×1.5 mm collimation and retrospective ECG gating. Left ventricular (LVEF) and right ventricular (RVEF) ejection fractions were calculated using dedicated three-dimensional software. Relationships between measurements obtained with MSCT and ERNA were assessed using linear regression analysis and reliability of MSCT was assessed with intra-class correlation coefficient. Bland–Altman analysis was performed to calculate limits of agreement between MSCT and ERNA. MSCT was performed successfully in ten patients with a mean acquisition time of 16.5±2.8 s. Functional cardiac evaluation was possible on CT for all patients except for one due to poor opacification of right ventricle. Linear regression analysis showed a good correlation between MSCT and ERNA for the LVEF (R=0.91) and the RVEF (R=0.89) measurements. Intra-class correlation was superior for LVEF (0.92) than for the RVEF (0.68). Bland–Altman plots demonstrated that MSCT substantially overestimated the ERNA RVEF. Morphological CT data demonstrated PE in four of ten of patients and alternative diagnoses in five of ten patients. Our study reveals that MSCT with retrospective ECG gating may provide in one modality a morphological and a functional cardiopulmonary evaluation. Comparison with ERNA demonstrated a good correlation for both ventricular ejection fractions.     

Determinants of the response of left ventricular ejection fraction to vasodilator stress in electrocardiographically gated 82rubidium myocardial perfusion PET

Purpose Myocardial perfusion imaging with ⁸²Rb PET allows for ECG-gated studies to be obtained early after radiotracer injection, capturing ventricular function close to peak pharmacologic action of dipyridamole. This is different from gated SPECT and may potentially provide additional diagnostic information. We sought to identify potential correlates of the PET-derived ejection fraction response to vasodilator stress. Methods One hundred ten consecutive patients undergoing ⁸²Rb PET myocardial perfusion imaging during evaluation for coronary artery disease were included. Using a GE Discovery STRx PET-CT scanner, ECG-gated images (eight bins) were obtained at rest and 4 min after dipyridamole infusion, 90 s after infusion of 1,480–2,220 MBq of ⁸²Rb. Summed rest, stress, and difference scores (SRS, SSS, and SDS) were determined using a five-point scoring system and 20-segment model. Ejection fraction was calculated using automated QGS software. Results Significant reversibility (SDS ≥ 4) was found in 23 patients (21%). Mean LVEF in all patients was 47 ± 13% at rest and 53 ± 13% during dipyridamole. LVEF increased in 89 patients, and decreased in 17 patients during vasodilation. The change in LVEF was inversely correlated with SDS (r = −0.26; p = 0.007). Additionally, it was inversely correlated with resting LVEF (r = −0.20; p = 0.03) and SSS (r = −0.25; p = 0.009). No significant correlations were observed with SRS, heart rate, blood pressure, age, hypertension, hypercholesterolemia, or pretest likelihood of disease. At multivariate regression analysis, SDS was an independent predictor of the change in LVEF. Conclusions Gated ⁸²Rb PET during pharmacologic stress allows for assessment of the functional response to vasodilation. The magnitude of LVEF increase is determined by stress perfusion/reversible perfusion defects. Functional response to hyperemia may thus be incorporated in future evaluations of diagnostic and prognostic algorithms based on ⁸²Rb PET.     

Physiological coxa varus–genu valgus influences internal knee and ankle joint moments in females during crossover cutting

This study evaluated the ankle and knee electromyographic, kinematic, and kinetic differences of 20 nonimpaired females with either neutral (group 1) or coxa varus–genu valgus (group 2) alignment during crossover cutting stance phase. Two-way mixed model ANOVA (group, session) assessed mean differences (p<0.05) and correlation analysis further delineated relationships. During impact absorption, group 2 displayed earlier peak horizontal braking (anterior-posterior) ground reaction force timing, decreased and earlier peak internal knee extension moments (eccentric function), and earlier peak internal ankle dorsiflexion moment timing (eccentric function). During the pivot phase, group 2 displayed later and eccentrically-biased peak ankle plantar flexion moments, increased peak internal knee flexion moments (eccentric function), and later peak knee internal rotation timing. Correlation analysis revealed that during impact absorption, subjects with coxa varus–genu valgus alignment (group 2) displayed a stronger relationship between knee internal rotation velocity and peak internal ankle dorsiflexion moment onset timing (r=–0.64 vs r =–0.26) and between peak horizontal braking ground reaction forces and peak internal ankle dorsiflexion moment onset timing (r=0.61 vs r=0.24). During the pivot phase these subjects displayed a stronger relationship between peak horizontal braking ground reaction forces and peak internal ankle plantar flexion moment onset timing (r=–0.63 vs r=–0.09) and between peak horizontal braking forces and peak internal ankle plantar flexion moments (r=–0.72 vs r=–0.26). Group differences suggest that subjects with coxa varus–genu valgus frontal-plane alignment have an increased dependence on both ankle dorsiflexor and plantar flexor muscle group function during crossover cutting. Greater dependence on ankle muscle group function during the performance of a task that requires considerable 3D dynamic knee joint control suggests a greater need for frontal and transverse plane weight bearing tasks that facilitate eccentric ankle muscle group function to optimize injury prevention conditioning and post-surgical rehabilitation programs.     

Pituitary gland signal in pre-term infants during the first year of life: an MRI study

Our purpose was to determine the pituitary gland signal of premature neonates and infants. We retrospectively measured, in a midline sagittal T1-weighted MRI scan, the pituitary signal of 121 premature infants (mean gestational age: 32.8 weeks, mean chronological age:6.9 months, mean corrected age:5.2 months). The relative signal intensity of the adenohypophysis and neurohypophysis was measured as (A–V)/V and (P–V)/V, respectively (where A, P, V are the mean signal intensities of the adenohypophysis, neurohypophysis and vermis white matter, respectively). On visual inspection the adenohypophysis was rated relative to the vermis white matter (VWM) and scored as hyperintense (grade 3), isointense (grade 2) and hypointense (grade 1). (A–V)/V and (P–V)/V had a negative correlation with chronological age (r=–0.38, r=–0.35, respectively, P<0.01) and corrected age (r=–0.42, r=–0.40, respectively, P<0.01). The (A–V)/V was different in the three grade groups; significant difference was found between grades 3 and 2 and grades 3 and 1. The adenohypophysis was bright in 93% of babies under 2 months of chronological age. In five babies of mean gestational age 29.1 weeks a hyperintense adenohypophysis was observed at 2.9–3.7 months of chronological age (corrected age 0.37–2 months). We conclude that in pre-term babies the adenohypophysis appears in hypersignal that may persist up to 2 months of corrected age. The adenohypophyseal and neurohypophyseal signals decrease with age.     

Analysis of the human brain in primary progressive multiple sclerosis with mapping of the spatial distributions using 1H MR spectroscopy and diffusion tensor imaging

Primary progressive multiple sclerosis (ppMS; n=4) patients and controls (n=4) were examined by 1H magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) in order to map choline (Cho), creatine and N-acetylaspartate (NAA), the fractional anisotropy (FA) and the apparent diffusion constant (ADC). After chemical shift imaging (point-resolved spectroscopy, repetition time/echo time 1,500 ms/135 ms) of a supraventricular volume of interest of 8×8×2 cm³ (64 voxels) MRS peak areas were matched to the results of DTI for the corresponding volume elements. Mean FA and NAA values were reduced in the ppMS patients (P<0.01, both) and the ADC increased (P<0.02). The spatial distribution of NAA showed strong correlation to ADC in both ppMS patients and controls (r =–0.74 and r= –0.70; P<0.00001, both), and weaker correlations to FA (r=0.49 and r=0.41; P<0.00001, all). FA and ADC also correlated significantly with Cho in patients and controls (P<0.00001, all). The relationship of Cho and NAA to the ADC and the FA and thus to the content of neuronal structures suggests that these metabolite signals essentially originate from axons (NAA) and the myelin sheath (Cho). This is of interest in view of previous reports in which Cho increases were associated with demyelination and the subsequent breakdown of neurons.     

Gated 99mTc-MIBI single-photon emission computed tomography for the evaluation of left ventricular ejection fraction: comparison with three-dimensional echocardiography

Objective  Parameters of left ventricular systolic function directly influence the management of patients with suspected coronary artery disease (CAD). Quantitative gated single-photon emission computed tomography (QGS; Cedars-Sinai Medical Center, Los Angeles, CA, USA) allows the computation of left ventricular ejection fraction (LVEF) from myocardial perfusion imaging studies which are frequently performed on patients with suspected CAD. Three-dimensional (3D) echocardiography is considered to be the echocardiographic “gold standard” for the quantification of LVEF. We sought to compare QGS with 3D echocardiography in the evaluation of EF in patients with suspected CAD. Methods  Ninety-one consecutive patients with suspected CAD, scheduled for coronary angiography, underwent rest electrocardiographic-gated technetium-99m methoxyisobutylisonitrile SPECT (G-SPECT) with measurement of LVEF by QGS and transthoracic 3D echocardiography with off-line measurement of LVEF (Tomtec 4D LV Analysis 1.1). The diagnosis of CAD was based on coronary angiography, performed on every patient. Results  Nine patients were excluded from the analysis owing to unsuitability for 3D echocardiography (8 patients) or G-SPECT (1 patient). In the remaining group of 82 patients, 71 (87%) had significant CAD, 34 (42%) had a history of myocardial infarction, and 50 (61%) had perfusion defects at rest G-SPECT images. The mean LVEF measured by QGS and 3D echocardiography was 53 ± 13% and 53 ± 10%, respectively. The mean difference in LVEF between 3D echocardiography and QGS was 0.1 ± 6.0% (P = 0.87), and the correlation between the values obtained by both methods was high (r = 0.88, P < 0.001). The largest discrepancies were observed in patients with small ventricular volumes. Conclusions  In patients undergoing diagnostic work-up for CAD, the measurement of LVEF by QGS algorithm provides high correlation and satisfactory agreement with the results of reference ultrasound method-3D echocardiography.     

Use of technetium-99m sestamibi ECG-gated single-photon emission tomography for the evaluation of left ventricular function following coronary artery bypass graft: comparison with three-dimensional magnetic resonance imaging

In patients who had undergone cardiac surgery (coronary artery bypass graft) and whose hearts showed abnormal movement during the cardiac cycle, we studied the accuracy of functional assessment using ECG-gated single-photon emission tomography (SPET) and the automated software developed by Germano et al. by comparing the findings with magnetic resonance (MR) images acquired three-dimensionally. Sixteen patients who had undergone cardiac surgery underwent ^99mTc-sestamibi gated SPET (MIBI-g-SPET) and MRI on the same day. Left ventricular end-diastolic and end-systolic volumes (EDV, ESV) and ejection fraction (LVEF) were measured using MIBI-g-SPET and the aforementioned algorithm. Regional wall thickening was assessed using a four-point scale on MIBI-g-SPET and cine MRI. There was a good correlation between MIBI-g-SPET and MRI in respect of EDV (r=0.89), ESV (r=0.93) and LVEF (r=0.89). A high degree of agreement was found between the wall thickening scores obtained by MIBI-g-SPET and MRI in total segments (κ=0.62) and in septal segments (κ=0.67). It is concluded that ECG-gated perfusion SPET can provide regional and global functional information, including absolute volumes, in patients following cardiac surgery. Received 5 January and in revised form 18 March 1999     

Validation of a new counts-based gated single photon emission computed tomography method for quantifying left ventricular systolic function: Comparison with equilibrium radionuclide angiography

Background  Because myocardial wall thickness is smaller than the spatial resolution of single photon emission computed tomography (SPECT) imaging, changes in myocardial wall thickness are related to changes in maximum pixel counts via the partial volume effect, allowing for quantification of regional systolic wall thickening. We have developed a new gated SPECT method for computing the global left ventricular ejection fraction (LVEF) based entirely on changes in maximum regional myocardial counts during systolic contraction. This new method is independent of endocardial edge detection or other geometric measurements. Methods and Results  In 23 patients the gated SPECT method was validated by comparison with radionuclide angiography. The correlation between computed LVEFs was excellent (slope=0.97, r=0.91). The measurement of LVEF by gated SPECT was highly reproducible, with minimal intraoperator (slope=0.97, r=0.97) or interoperator (slope=1.00, r=0.97) variability. Measurements of regional thickening indexes were also reproducible, with a mean intraoperator correlation coefficient of 0.89±0.05 (range 0.79 to 0.95) for the 14 myocardial regions. Finally, the measurement of LVEF was not significantly influenced by changes in reconstruction filter parameters over a range of cutoff frequencies from 0.16 to 0.28. Conclusions  This new counts-based gated SPECT method for measuring global left ventricular systolic function correlates well with radionuclide angiography, is highly reproducible, and has theoretic advantages over geometric methods. Supported by a grant from the American Heart Association, Virginia Affiliate, Inc., and by a grant from DuPont Pharma Radiopharmaceuticals, N. Billerica, Mass.