Biomedical subjects
Publications and source records attributed to G Rizzo.
Extracardiac and cardiac flow velocity waveforms were recorded in a severely growth-retarded fetus 1 day and a few hours before fetal death. At the first scan, the typical Doppler patterns of a growth-retarded fetus were found, but the brain-sparing effect was lost at the last examination and a huge tricuspid insufficiency was demonstrated.
A hybrid method for attenuation correction (HAC) in positron emission tomography (PET) brain studies is proposed. The technique requires the acquisition of two short (1 min) transmission scans immediately before or after the emission study, with the patient and the head fixation system in place and after removing the patient from the scanner with the head fixation system alone. The method combines a uniform map of attenuation coefficients for the patient's head with measured attenuation coefficients for the head fixation system to generate a hybrid attenuation map. The HAC method was calibrated on 30 PET cerebral studies for comparison with the conventional measured attenuation correction method by ROI analysis. Average differences of less than 3% were found for cortical and subcortical regions. The HAC technique is particularly suitable in a PET clinical environment, allowing a reduction of the total study time, greater comfort for patients and an increase in patient throughput.
OBJECTIVE: Our purpose was to evaluate the incidence and patterns of chromosomal abnormalities in fetuses with absent end-diastolic velocity in umbilical artery and to analyze maternal and fetal factors associated with abnormal karyotype. STUDY DESIGN: One hundred ninety-two fetuses of known karyotype with absent end-diastolic velocity in the umbilical artery at a gestational age > 20 weeks were considered. The following potential risk factors were analyzed in a multiple logistic regression model: maternal age, gravidity, parity, gestational age at diagnosis, presence of gestational hypertension and preeclampsia, presence of fetal malformations, different biometric measurements, head/abdominal circumference ratio, amniotic fluid volume, and several Doppler index values calculated from uterine arteries, fetal heart, and fetal peripheral arteries and veins. RESULTS: Sixteen cases had an abnormal karyotype. In two cases a triploidy was present, whereas the remaining 14 cases had autosomal aberrations. The risk factors statistically significantly and independently associated with the presence of an abnormal karyotype were maternal age > 35 years, gestational age at diagnosis < 27 weeks, presence of multiple malformations, and absence of gestational hypertension and preeclampsia. All the fetuses with an abnormal karyotype but one were correctly identified by at least one risk factor. CONCLUSIONS: An abnormal karyotype is present in 8.3% of fetuses with absent end-diastolic velocity in umbilical artery and is associated with maternal and fetal risk factors. The knowledge of these factors may be useful in the management of such fetuses.
OBJECTIVE: Our purpose was to evaluate Doppler-detectable differences in the fetal circulation of discordant twins with a growth defect resulting from either placental insufficiency or twin-to-twin transfusion syndrome. STUDY DESIGN: Serial weekly Doppler recordings were performed for at least 3 weeks preceding delivery in 15 pairs of dichorionic twins (group A) in which the smaller twin had fetal distress (i.e., antepartum fetal heart rate late decelerations) and in 10 pairs of diamniotic and monochorionic twins (group B) in which the diagnosis of twin-to-twin transfusion syndrome was confirmed postnatally. Doppler recordings were obtained from umbilical artery, descending aorta, and middle cerebral artery, and the pulsatility index values were calculated. Furthermore, peak velocity from cardiac outflow tract and the percent of reverse flow in the inferior vena cava were calculated. For all these index values the intertwin differences (delta value) were calculated by subtracting the values obtained in the larger twin with those of the smaller twin. RESULTS: In group A significant changes of delta values were evidenced for all the parameters tested. In particular, delta values of pulsatility index from the umbilical artery and descending aorta progressively increased approaching the occurrence of late decelerations, whereas the delta value for the middle cerebral artery reached a nadir 2 weeks before delivery. Similarly, delta values of peak velocity from outflow tracts significantly decreased, whereas those of the percent reverse flow in the inferior vena cava increased during the time considered. In group B fetuses no significant intertwin differences in pulsatility index values were evidenced in the vessels investigated, resulting in absence of modifications in delta values during the time interval considered. Moreover, significant changes were found in delta values of both the peak velocity from the outflow tract and the percent of reverse flow in the inferior vena cava. However, these changes were limited to the last recording, where the former delta value increased and the latter decreased. CONCLUSIONS: Serial Doppler recordings may show hemodynamic changes in the fetal circulation of discordant twins. Different trends occur according to the underlying pathophysiologic mechanisms of the growth defect. The knowledge of these temporal changes may be useful in the management of such fetuses.
The objective of this study was to evaluate whether Braxton-Hicks contractions induce changes in fetal heart rate variation in normal and growth-retarded fetuses. 110 uncomplicated singleton pregnancies were cross-sectionally studied as well as 16 pregnancies complicated by fetal growth retardation secondary to uteroplacental insufficiency. Fetal heart rate variability was analyzed by a commercially available computerized system (2CTG Hewlett Packard, Italy) 10 min before and 10 min after the Braxton-Hicks contraction. All the included fetal heart rate tracings fulfilled the following criteria: (1) presence of a single Braxton-Hicks contraction in the 20 min considered; (2) absence of fetal heart rate decelerations after the contraction, and (3) stable fetal heart rate behavioral pattern in the period analyzed. 82 tracings of normal fetuses were analyzed during an active fetal heart rate pattern (type B) and the remaining 28 during a quiet pattern (type A). In both patterns no significant differences in delta value, long-term irregularity, short-term variability and interval index were found before and after the contraction. All the tracings of growth-retarded fetuses were analyzed during the fetal heart rate pattern A. Short-term variation and interval index significantly decreased during the first 5 min after the contraction while no significant differences were found in the other indices investigated. The decrease in these indices was significantly more marked in those fetuses developing fetal distress within 7 days. In conclusion, Braxton-Hicks contractions induce a significant decrease of short-term variation and interval index only in growth-retarded fetuses. This can be useful in the early identification of fetal compromise in such fetuses.
In an effort to determine the factors influencing the abnormal ventricular filling patterns of fetuses of type I diabetic mothers, Doppler flow velocity waveforms were recorded from fetal atrioventricular valves in 37 pregnancies complicated by type I diabetes immediately before an elective cesarean section. The ratio between the peak velocities during early passive ventricular filling and active atrial filling was calculated at the level of both atrioventricular valves and related to different factors including ventricular chamber wall thickness, heart rate, umbilical vein hematocrit and time to peak velocities values obtained at the outflow tract. Multiple stepwise regression demonstrated that the interventricular wall thickness, heart rate and hematocrit values significantly and independently affected the ratios between early and active ventricular filling from mitral and tricuspid valves. As a consequence all these factors should be taken into account in the interpretation of atrioventricular Doppler indices.
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Reference limits for the PI from the umbilical, middle cerebral, and renal arteries were constructed using BPD, AC, FL, and transverse cerebellar diameter as independent variables and their efficacy tested in a population of SGA fetuses. Therefore, 153 normal fetuses and 90 SGA fetuses with established dates between 20 and 40 weeks of gestation were considered. Normal fetuses showed a linear negative relationship between the PI from all the vessels investigated and all the biometric parameters considered. Although the BPD related better with the PI from the umbilical artery (r = 0.646) and the renal artery (r = 0.765) and the transverse cerebellar diameter related better with middle cerebral artery PI values (r = 0.510), no evident differences in fitting were found among the variables tested. In SGA fetuses the nomograms on BPD, AC, and FL significantly underestimated PI values in all the vessels studied when compared to the nomograms based on gestational age, while a similar ability in identifying abnormal PI values was found for nomograms based on gestational age and transverse cerebellar diameter. These newly developed nomograms based on transverse cerebellar diameter may prove useful in the evaluation of Doppler indices of fetuses with uncertain gestational age.
A system aimed at the management and fusion of multimodal biomedical images, including X-ray computed tomography, magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography, has been implemented for neurological applications. This bioimaging integration system (BIS) consists of a network for image transmission from acquisition machines to dedicated image processing workstations, a software library for image standardization, and an image registration technique to project multimodal volumetric images into a common reference space. The registration procedure was evaluated in MRI/PET correlation studies, in which misalignment errors of 2.6 mm in the xy transaxial plane and 3.4 mm along the z axis were found. BIS has been validated for the anatomical-functional correlation analysis of MRI and PET images in neurological research protocols and clinical studies.
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UNLABELLED: SPECT studies of regional cerebral perfusion with a high-resolution system were compared to PET studies of regional cerebral glucose utilization (rCMRglc) in 21 patients with probable Alzheimer's disease (AD). Ten normal subjects were also evaluated with SPECT and 10 with PET. METHODS: rCMRglc (for PET) and counts (for SPECT) in the associative cortices were normalized to the average rCMRglc, and counts in the calcarine cortex and basal ganglia were considered as a "reference area" to obtain a ratio. The ratio differences between patients and controls were tested with ANOVA performed separately for PET and SPECT. RESULTS: The difference between probable AD patients and controls was significant for both PET (p < 0.00001) and SPECT (p < 0.005); this difference was significant for the frontal, temporal and parietal cortices (p < 0.0001) for PET, and for the temporal (p < 0.005) and parietal (p < 0.001) cortices for SPECT. Temporo-parietal defects were detected in all subjects with PET and in 90% with SPECT. CONCLUSION: PET and SPECT are able to detect characteristic temporo-parietal abnormalities in probable AD. However, the presence of abnormalities in other associative areas is better evaluated with PET.
Regional cerebral blood flow was measured using positron emission tomography (PET) in normal subjects while performing simple aimless proximal and distal arm movements. The aim of the experiment was to compare the somatotopic organization of precentral and mesial (the so called supplementary motor area, SMA) motor cortices and to evaluate whether in man, as in the monkey, the rostral and caudal sectors of SMA are functionally different. The results showed that proximal and distal arm movements are to a large extent segregated in the precentral motor cortex, but not in the SMA. They also showed that the SMA is made of at least two functional sectors. Only the caudal one is activated during simple aimless movements.
On the basis of the data obtained in sheep fetuses showing a high interdependence between umbilical vein oxygenation and ductus venosus flow, we investigated the effect of maternal hyperoxygenation on ductus venosus velocity waveforms in normal third-trimester human fetuses. Ductus venosus velocity waveforms were recorded by using color and pulsed Doppler ultrasonography before and after 15 min of maternal administration of humidified 60% oxygen. During maternal hyperoxygenation, there was a significant increase of both estimated peak velocities during systole, diastole and atrial contraction and the mean temporal velocity during the total cardiac cycle and systolic and diastolic portions. On the other hand, during maternal hyperoxygenation, no significant changes were found in fetal heart rate or in the ratios between peak velocities and mean temporal velocities during systole and diastole. These findings suggest a close relationship between fetal oxygenation and ductus venosus velocity waveforms that may be useful in monitoring fetal hypoxemia.
Doppler ultrasound was used to study the main uterine artery flow velocity waveforms in an unselected population of 272 primiparous women at 22 weeks' gestation. The incidences of subsequent complications were as follows: gestational hypertension alone, 4.4%; intrauterine fetal growth retardation alone, 4%; and gestational hypertension with intrauterine growth retardation, 3.6%. The flow velocity waveform was considered abnormal when the resistance index in the uterine artery was greater than 0.58. This identified 9.5% of the population as 'at risk' and predicted either of the above outcomes with an overall sensitivity of 74% (kappa index, 0.72). The sensitivity of prediction for gestational hypertension alone was 50% while for proteinuric gestational hypertension it was 88%. The best result was obtained for the prediction of pregnancies affected by both gestational hypertension and intrauterine growth retardation, where the sensitivity was 100%.