Biomedical subjects

M Schwaiger

Publications and source records attributed to M Schwaiger.

At least 127 records · Page 7Linked to original sources

PubMed2000

Incomplete sympathic reinnervation of the orthotopically transplanted human heart: observation up to 13 years after heart transplantation.

OBJECTIVE: Heart transplantation (HTx) is associated with autonomic denervation of the donor heart. Sympathetic reinnervation (RI) as defined by the presence of functional nerve terminals occurs only if sympathetic ganglia outside the heart are connected with nerve terminals in the transplanted heart. The purpose of this study was to define the incidence and functional consequences of RI over time after HTx. The activity and distribution of norepinephrine (NE) uptake sites were assessed by positron emission tomography (PET) imaging. Symptom limited exercise testing was performed by bicycle-ergometer. METHODS: Forty-seven patients (m:f=42:5, 47.6+/-8. 2 years, age range 27-65 years) were investigated between 2 months and 13.6 years after HTx using PET and the NE analogue C-11-hydroxyephedrine (HED). Tracer uptake was quantified using dynamic imaging protocols yielding regional HED retention fraction. A regional value above 7%/min (+/-2.5 SD above the mean value of denervated hearts) was considered evidence for RI. The functional significance of RI was investigated in 34 patients (m:f=30:4, 49. 3+/-8.4 age range 27-62 years) by symptom limited exercise testing. Cardiac catheterization was performed at the time of PET imaging. RESULTS: RI could not be assessed in the first year after HTx, in 11% in the second year and in 80% of the patients from the third year on. Retention values plateaued then. In all time intervals, beyond the third year, not reinnervated patients were found. RI remained incomplete and was always restricted to the anterior wall of the left ventricle. Extent of retention of the left ventricle revealed a large individual range up to 66%, averaging of 20%. Recipient age at the time of HTx, reinnervated patients were 5.5 years younger than not reinnervated ones, proved as the only significant influencing factor for RI (P<0.05). Dividing patients into scintigraphically reinnervated (n=20) and not reinnervated (n=14), reinnervated patients displayed during exercise a higher maximal heart rate (137+/-14 vs. 123+/-20/min, P<0.05), heart rate increase (40+/-15 vs. 28+/-13/min, P<0.05), max. oxygen consumption (1674+/-424 vs. 1279+/-308 ml/min, P<0.01) and anaerobic threshold (887+/-170 vs. 717+/-183 mlO(2)/min, P<0.01) than not reinnervated ones. A correlation between transplant vasculopathy and RI could not be demonstrated. CONCLUSION: ++: RI assessed by PET and the NE analogue HED is time dependent, incomplete, displays a typical pattern and demonstrates a broad individual spread. Furthermore, RI enhances functional parameters of exercise testing.

Carbon Radioisotopes↗

PubMed2000

Sympathetic reinnervation of sinus node and left ventricle after heart transplantation in humans: regional differences assessed by heart rate variability and positron emission tomography.

BACKGROUND: Orthotopic heart transplantation (HTx) results in complete cardiac denervation. Reestablished partial sympathetic nerve function has been found in patients some years after HTx. However, the atrial and ventricular regional patterns of reinnervation have not been established. METHODS: Two parallel methods were used to evaluate the regional restoration of sympathetic nerves in the myocardium. Patients were investigated with respect to ventricular reinnervation (VI) using positron emission tomography (PET) and the norepinephrine analogue C-11-hydroxyephedrine (HED). Tracer uptake was quantified using dynamic imaging protocols, yielding regional HED retention fraction. A regional value above 7%/minute ( +/- 2.5 SD above the mean value of denervated hearts) was considered evidence of sympathetic reinnervation. Spectral analysis of heart rate variability (HRV) served as a quantitative marker for reinnervation at the sinus node (SI). Spectra of HRV during positive head-up tilt were calculated. The low frequency (LF) power spectral density (0.05 to 0.18 Hz) was evaluated. RESULTS: After HTx (4. 6 +/- 3.9 years; range, 0.2 to 13.6 years), 38 patients (aged 50.9 +/- 7.6 years; range, 37 to 65 years) were investigated by PET imaging and HRV. Twenty-two patients with a mean HED retention of 10. 7 +/- 2.6%/minute were classified as left ventricular reinnervated. Sixteen patients with a mean HED retention of 4.8 +/- 0.8%/minute did not reach the threshold. The time difference after HTx was significant for these 2 groups, 5.3 +/- 3.0 years vs 3.8 +/- 4.7 years ( p < 0.05 ). The LF power spectral density of the ventricular reinnervated patients was 5.9 +/- 8.6 ms(2), and 1.8 +/- 4.4 ms(2) (p <0.005 ) for those not reinnervated. Low frequency showed small values and narrow distribution for the patients not reinnervated, assuming sinus node denervation, and showed extended distribution for the reinnervated, suggesting a heterogeneous reinnervation pattern. CONCLUSIONS: Two non-invasive parallel methods were used to investigate regional reestablishment of cardiac nerves in the myocardium in HTx patients. Left VI assessed by PET imaging and SI by HRV was congruent in 60% of HTx patients. Lack of SI paralleled absence of VI. Our results suggest that partial VI occurs prior to SI.

Adult↗

PubMed2000

Regional pre- and postsynaptic sympathetic system in the failing human heart--regulation of beta ARK-1.

OBJECTIVES: Regional presynaptic sympathetic innervation varies considerably in the cardiomyopathic human heart, as shown in previous studies in vivo and in vitro. The goal of the present study was to correlate markers of presynaptic sympathetic innervation with local measurement of the postsynaptic beta-adrenergic system in failing human hearts. METHODS AND RESULTS: In nine left ventricular regions of hearts explanted from patients suffering from dilated cardiomyopathy, we measured the density of uptake(1) carriers ([3H]mazindol binding) as a marker of presynaptic function as well as beta-receptor density ([3H]CGP 12177 binding) and beta ARK-1 levels as the pivotal compounds of postsynaptic adrenergic signal transduction. Additionally, a subgroup of the patients was examined in vivo by HED-PET prior to heart transplantation. The density of uptake(1) was related to local hydroxyephedrine (HED) retention (as determined by pre-operative PET, r=0.65), whereas it was inversely correlated to regional beta ARK-1 levels (r=-0.61, P=0.04). In contrast, beta-adrenergic receptor density was not significantly correlated either to uptake(1) density or to local HED retention (r=0.15 and r=0.21). CONCLUSIONS: Regional beta ARK-1 levels rather than beta-adrenergic receptor density were correlated with presynaptic alterations in cardiomyopathic human left ventricles. It can be assumed that in the cardiomyopathic human heart, regional beta-adrenergic desensitization might be determined by differences in local beta ARK levels rather than by changes in beta-receptor density.

Adult↗

PubMed2000

Image processing in esophageal scintigraphy: topography of transit times.

In the investigation of esophageal transport, the knowledge provided by scintigraphy is mostly based upon the extraction as well as representation of the information obtained. Recently, new tools have been developed for use in computer-based image processing which have made visualization and quantitation of esophageal bolus transport possible through depiction of the 'topography of transit times'. Data extracted from the images obtained in multiple swallowing studies from a single healthy volunteer as well as in patients suffering from gastroesophageal reflux disease (GERD) and from Barrett's esophagus are compressed, filtered and depicted in quantifiable concise plots or multidimensional images. Profile plots demonstrated a considerable increase in local transit times along the esophagus superimposed, however, by a distinctive pattern of local delays. Above the level of the lower esophageal sphincter (LES), the bolus accumulates in a functional ampulla. Subprocesses of bolus transit through the LES, disclosed by spatiotemporal enhancement, allow for the differentiation between mass transit of the bolus and closure of the LES which was considerably retarded in the case of the patient with Barrett's esophagus. The image-processing tools developed for topographic visualization of transit times for esophageal bolus transport have greatly improved the extraction and quantifiable depiction of information obtained by scintigraphy. This can be used for definition of pathognomonic indices.

Barrett Esophagus↗

PubMed2000

Processing of histamine-induced itch in the human cerebral cortex: a correlation analysis with dermal reactions.

The subjective sensation of itch is a complex emotional experience depending on a variety of factors. In this study, the central nervous processing of pruritus was investigated in a human model. Activation of involved cerebral areas was correlated to scales of nociception and skin reactions. Six healthy male right-handed subjects participated in a standardized epidermal stimulus model with nine increasing doses of histamine dihydrochloride (0.03%-8%) on their right forearms. Controls consisted of three NaCl stimuli. Cerebral activation patterns were determined by H(2)(15)O positron emission tomography 120 s after stimulation. Dermal reactions to the stimulus (wheal, flare, temperature) were coregistered during the procedure. Itch sensation was determined by visual analog scale rating. Pain was not reported during the study; all volunteers had localized itch from 0.03% histamine on. Subtraction analysis versus control revealed significant activation of the left primary sensory cortex and motor-associated areas (mainly primary motor cortex, supplementary motor area, premotor cortex). Predominantly left-sided activations of frontal, orbitofrontal, and superior temporal cortex and anterior cingulate were also observed. Correlation analysis revealed coactivation of dermal reactions and cerebral response to itch in the following Brodmann areas with a Z score greater than 5: wheal, areas 5 (bilateral) and 19 (right); flare, areas 2-5 (left); temperature, area 10 (left) and left insula. Itch intensity ratings were mainly correlated with activation of the left sensory and motor areas. Functional covariates of the itch sensation in the central nervous system were identified. The intention to pruritofensive movements is probably mirrored by the activation of motor areas in the cortex. Other areas may be involved in emotional processing of sensations. Skin reactions wheal and flare also had significantly activated covariate areas in the central nervous system.J Invest Dermatol 115:1029-1033 2000

Adult↗

PubMed2000

Imaging in adults with congenital cardiac disease (ACCD).

Management of patients with congenital heart disease requires detailed information on cardiac and great vessel morphology. In previous years, the diagnosis and the treatment of congenital malformations has often depended on cardiac catherization, and in many institutions, cardiac catherization still remains the gold standard against which other modalities are measured. In the past decade, however, imaging methodologies have increasingly shifted toward the use of less invasive and noninvasive techniques. Currently, echocardiography is the initial method of choice in evaluating the anatomy, especially in younger patients. Meanwhile, several newer imaging techniques like magnetic resonance imaging (MRI) and spiral or multislice computed tomography (CT) are in use. They offer extremely useful information about abnormalities of the heart and great vessels as well as the assessment of cardiac anatomy and function. Echo, angiography, MRI and CT should be seen as complimentary investigations in adult congenital heart disease.

Adult↗

PubMed2000

Diagnosis of apical hypertrophic cardiomyopathy using magnetic resonance imaging.

Apical hypertrophic cardiomyopathy is an uncommon variant of non-obstructive hypertrophic cardiomyopathy with low prevalence outside East Asia. A case is reported of a non-Asian (European) 51 year old man with characteristic ECG and morphological changes of apical hypertrophic cardiomyopathy. Although the patient underwent catheterisation three years previously because of suggested coronary ischaemic heart disease, apical hypertrophic cardiomyopathy was not diagnosed. More recently, a regional wall motion abnormality was noticed at the apex on echocardiography. To rule out an ischaemic injury a stress perfusion scintigraphy was performed; no perfusion defect was present but an apical tracer enhancement was noted. Further evaluation by magnetic resonance imaging revealed the pathognomonic "ace of spades" configuration of the left ventricle with systolic obliteration of the apical region, which led to the diagnosis of apical hypertrophic cardiomyopathy.

Cardiomyopathy, Hypertrophic↗

PubMed2000

Positron emission tomography using [(18)F]Fluorodeoxyglucose for monitoring primary chemotherapy in breast cancer.

PURPOSE: To address the role of positron emission tomography (PET) using [(18)F]fluorodeoxyglucose (FDG) to monitor primary (neoadjuvant) chemotherapy in patients with locally advanced breast cancer. PATIENTS AND METHODS: Quantification of regional FDG uptake of the breast acquired after the first and second courses of chemotherapy was compared with the baseline scan in 22 patients with a total of 24 breast carcinomas. To evaluate the predictive value of PET imaging, histopathologic response after completion of chemotherapy classified as gross residual disease (GRD) or minimal residual disease (MRD) served as the gold standard. RESULTS: Significant differences in tracer uptake between nonresponding tumors (GRD) and responding lesions (MRD) were observed (P <.05) as early as after the first course of chemotherapy. Tracer uptake showed little change in tumors with GRD found later in pathologic analysis but decreased sharply to the background level in most tumors with MRD. After the first course, all responders were correctly identified (sensitivity 100%, specificity 85%) by a standardized uptake value decrease below 55% of the baseline scan. At this threshold, histopathologic response could be predicted with an accuracy of 88% and 91% after the first and second courses of therapy, respectively. CONCLUSION: This study demonstrates that in patients with advanced breast cancer undergoing primary chemotherapy, FDG-PET differentiates responders from nonresponders early in the course of therapy. This may help improve patient management by avoiding ineffective chemotherapy and supporting the decision to continue dose-intensive preoperative chemotherapy in responding patients.

Adult↗

PubMed2000

Effect of thyroid hormones on cardiac function, geometry, and oxidative metabolism assessed noninvasively by positron emission tomography and magnetic resonance imaging.

Thyroid hormones influence cardiac performance directly and indirectly via changes in peripheral circulation. Little, however, is known about the effect on myocardial oxidative metabolism and its relation to cardiac function and geometry. Patients with a history of thyroidectomy for thyroid cancer present a unique model to investigate the cardiac effects of hypothyroidism. Ten patients without heart disease were investigated in the hypothyroid state and again 4-6 weeks later under euthyroid conditions. Myocardial oxidative metabolism was measured by positron emission tomography with [11C]acetate and the clearance constant k(mono). Cine magnetic resonance imaging was applied to determine left ventricular geometry. A stroke work index (SWI = stroke volume x systolic blood pressure/ventricular mass) was calculated. Then, to estimate myocardial efficiency, a work metabolic index [WMI = SWI x heart rate/k(mono)] was obtained. Compared to hormone replacement, systemic vascular resistance and left ventricular mass were significantly higher in hypothyroidism. Ejection fraction and SWI were significantly lower. Despite an additional reduction of k(mono), the WMI was significantly lower, too. In summary, cardiac oxygen consumption is reduced in hypothyroidism. This reduction is associated with increased peripheral resistance and reduced contractility. Estimates of cardiac work are more severely suppressed than those of oxidative metabolism, suggesting decreased efficiency. These findings may provide an explanation for development or worsening of heart failure in hypothyroid patients with preexisting heart disease.

Acetates↗

PubMed2000

The clinical role of positron emission tomography in management of the cardiac patient.

Positron emission tomography (PET) is the most advanced scintigraphic imaging technique developed for in-vivo assessment of cardiac physiology and biochemistry. The currently available PET technology allows the measurement of regional tracer activity with high spatial and temporal resolution. Several radiopharmaceuticals have been introduced to study myocardial perfusion enabling accurate diagnosis and localization of coronary artery disease (CAD). Assessing myocardial blood flow at rest and under stress conditions and calculating (regional) coronary flow reserve by N-13 ammonia, Rb-82 or 0-15 water PET is the most sensitive means to detect any abnormal vasoreactivity which is already found at very early stages of the atherosclerotic process before any angiographic or clinical evidence of CAD. Flow tracers provide also quantitative information on the hemodynamic effects of any local, invasive (angioplasty) or systemic (risk factor modification) intervention. Metabolic imaging with F-18 deoxyglucose (FDG) PET represents currently the gold-standard for tissue viability assessment with well-validated information about the presence and extent of viable myocardium. The prognostic information of metabolic imaging extends to (preoperative) risk stratification in patients with congestive heart failure and facilitates the decision making between revascularization or conservative management. FDG has been also used in combination with SPECT providing comparable physiologic and pathophysiologic information but without need for the expensive and rarely available imaging technology of PET. More recently, newer tracers such as radiolabeled catecholamine analogs allowed the evaluation of cardiac autonomic innervation in a variety of cardiac diseases with involvement of neuronal innervation. C-11 hydroxyephedrine (HED) enabled imaging of alterations in neuronal innervation in diabetes, congestive heart failure and after heart transplantation. The unique functional and prognostic potential provided by PET imaging together with an expected easier access to this technology with better availability of lower cost instrumentation should raise its clinical acceptance in the near future.

Coronary Circulation↗

PubMed2000

Coronary microvascular reactivity to sympathetic stimulation in patients with idiopathic dilated cardiomyopathy.

UNLABELLED: The objective of this study was to assess noninvasively the microvascular reactivity to sympathetic stimulation in patients with idiopathic dilated cardiomyopathy (IDC) and in healthy volunteers, who underwent cardiac catheterization for exclusion of coronary artery disease. METHODS: Myocardial flow was quantified with 13N-ammonia PET and tracer kinetic modeling at rest and in response to cold pressor testing (CPT). Ten healthy volunteers (8 men, 2 women; mean age +/- SD, 50.7 +/- 15 y) and 10 matched patients (8 men, 2 women; mean age, 52.5 +/- 14 y) with IDC (mean left ventricular ejection fraction, 0.30 +/- 0.12) were included in the study. RESULTS: Myocardial perfusion at rest was not significantly different between the groups. However, myocardial vascular resistance (MVR) was significantly lower in IDC patients at rest than in healthy volunteers. In response to CPT a significant decrease in MVR was found in healthy volunteers (1.9 +/- 0.4 to 1.5 +/- 0.4 mm Hg x 100 g/mL; 22% decrease) but not in IDC patients (1.5 +/- 0.4 to 1.4 +/- 0.3 mm Hg x 100 g/mL; 9% decrease). Consequently, the increase of the myocardial blood flow in response to CPT was significantly lower (P < 0.008) in IDC patients (56 +/- 17 to 66 +/- 18 mL/100g/min; 20% increase) compared with healthy volunteers (52 +/- 12 to 80 +/- 30 mL/100 g/min; 52% increase), whereas both showed comparable hemodynamic reactions. CONCLUSION: The data indicate that CPT in combination with 13N PET imaging is a valuable noninvasive tool for assessment of coronary microvascular reaction to sympathetic stimulation in IDC patients. Lower coronary vascular resistance was found in IDC patients at rest compared with healthy volunteers, suggesting possible exhaustion of sympathetically induced dilation of the coronary microvasculature in IDC patients at rest. This mechanism may explain the impaired flow response to cold in IDC patients in the present study.

Blood Pressure↗

PubMed2000

Standardized annotation of nuclear medicine images.

There are no generally accepted standards for annotating nuclear medicine images. This is a potential problem whenever hardcopies from other centers are being evaluated, reinterpreted or compared to actual images of the same patient. Proposals for image annotation are elaborated to support image evaluation by a third party. In this paper, examples are given of lung scintigraphy, thyroid scintigraphy, bone scintigraphy both in planar and SPECT techniques, renal function scintigraphy, myocardial perfusion scintigraphy, and PET. They are presented to stimulate discussion in the nuclear medicine community.

Forms and Records Control↗

PubMed2000

6-O-(2-[18F]fluoroethyl)-6-O-desmethyldiprenorphine ([18F]DPN): synthesis, biologic evaluation, and comparison with [11C]DPN in humans.

UNLABELLED: 6-O(2-[18F]fluoroethyl)-6- -desmethyldiprenorphine ([18F]DPN) was developed and biologically evaluated. Results of animal experiments, binding studies in vivo, and a human PET study are reported and compared with those of [11C]DPN. METHODS: [18F]DPN was obtained by 18F-fluoroethylation of 3-O-trityl-6-O-desmethyldiprenorphine and subsequent deprotection in good radiochemical yields (23% +/- 7%; 100 min; 37 TBq/mmol). Binding of [18F]DPN to mu, kappa, and delta opioid receptors was shown by autoradiography studies on rat brain slices. Quantification of cerebral opioid receptor binding in men was performed by spectral analysis of a dynamic PET scan (25 frames, 90 min) after intravenous application of 63 MBq [18F]DPN (36 GBq/micromol) and correction for metabolites. RESULTS: [18F]DPN shows high affinity to opioid receptors. Parametric images (impulse response function at 60 min) of this human study showed a binding pattern of [18F]DPN equal to that of a control group (n = 9 healthy volunteers) after administration of [11C]DPN. CONCLUSION: The advantage of the longer half-life of 18F will allow extended scanning periods, more flexible interventions (e.g., displacement studies), and DPN to be available to PET centers without an on-site cyclotron.

Adult↗

PubMed2000

Phantom limb pain in the human brain: unraveling neural circuitries of phantom limb sensations using positron emission tomography.

Pain and other phantom limb (PL) sensations have been proposed to be generated in the brain and to be reflected in activation of specific neural circuits. To test this hypothesis, hypnosis was used as a cognitive tool to alternate between the sensation of PL movement and pain in 8 amputees. Brain activity was measured using positron emission tomography. PL movement and pain were represented by a propagation of neuronal activity within the corresponding sensorimotor and pain-processing networks. The sensation of movement was significantly (corrected for multiple comparisons) related to activity in the supplementary motor area and the primary sensorimotor cortex. The sensation of a painful PL posture activated the same brain areas but was weaker and less extended in the supplementary motor area. In contrast to the sensation of movement, pain was significantly related to activity in the thalamus, anterior cingulate, and lateral prefrontal cortex. Subjectively rated PL pain sensation correlated positively to activations in the anterior and posterior cingulate. These findings provide evidence that PL sensations are produced by the same central nervous processes that underlie the experience of the body when it is intact and that the corporeal awareness of PL pain is encoded in a thalamocortical network.

Adult↗

PubMed2000

Effect of N-butylscopolamine on intestinal uptake of fluorine-18-fluorodeoxyglucose in PET imaging of the abdomen.

AIM: Circumscribed or diffuse intestinal uptake of F-18-fluorodeoxyglucose (FDG) is a frequent finding in PET imaging of the abdomen often interfering with correct scan interpretation. The aim of the present study was to determine whether the antiperistaltic agent N-butylscopolamine reduces intestinal FDG-uptake. METHODS: Whole body scans from 40 patients with malignant lymphoma and no evidence for intraabdominal tumor involvement were analyzed (6 bed positions; scan start 60 min post injection of approximately 350 MBq FDG; emission time 9 min per position; no attenuation correction). Twenty patients received 20 mg N-butylscopolamine in combination with an intravenous injection of FDG (test group) and 20 patients received only FDG (control group). For analysis, the intensity of bowel loops and diffuse abdominal background were compared to normal liver on a 4 point scale (0 = lowest intensity, 3 = highest) by two experienced nuclear medicine physicians. Furthermore, focal intestinal uptake was evaluated quantitatively by a ROI technique and bowel to liver ratios (b/l) were calculated. RESULTS: Bowel loops had lower intensity and occupied less abdominal regions in the test group than in the control group (visual score 1 vs. 1.5, p = 0.01; abdominal regions 1 of 5 vs. 2.5 of 5, p = 0.04). The visual score for diffuse abdominal background was 0.5 in the test group and 1 in the control group (p = 0.04). Bowel uptake interfered with scan interpretation in 1 of 20 patients in the test group and 6 of 20 patients in the control group (p = 0.01). The b/l ratios were 1.5 +/- 0.7 in the test group and 2.3 +/- 1.4 in the control group (p = 0.08). CONCLUSION: Administration of N-butylscopolamine reduces intestinal uptake of FDG and may facilitate accurate interpretation of abdominal FDG-PET studies.

Abdomen↗

PubMed1999

Cardiological applications of nuclear medicine.

Cardiovascular mortality is falling in most industrialised nations. Primarily responsible for this encouraging trend are preventive measures such as risk-factor modification but improved medical and surgical management have helped too. Clinical decision making in the patient with coronary heart disease demands techniques that not only describe coronary anatomy but also provide functional indices for early detection and to monitor the severity and extent of disease. Nuclear medicine methods can characterise non-invasively myocardial function, perfusion, and metabolism. Novel radiopharmaceuticals, improvements in imaging equipment, and extensive validation have contributed to the growing clinical acceptance of these techniques and to their cost-effective integration in the workup of patients with cardiovascular disease.

Coronary Disease↗

PubMed1999

[Radioiodine therapy of functional autonomy of the thyroid gland. Treatment results in view of pretreatment scintigraphic diagnosis and early response of triiodothyronine levels to treatment].

AIM: The goal of this retrospective study was to evaluate the results of radioiodine therapy of thyroid autonomy with respect to the underlying scintigraphic pattern, administered I-131 doses and pretherapeutic Tc-99m and I-131 uptake. Furthermore, early post-therapeutic free triiodothyronine (FT3) levels were measured during the first 6 weeks after radioiodine therapy with respect to a FT3-increase. PATIENTS AND METHODS: Thyroid autonomy in 632 patients was followed for at least 3 months (mean 10.9 months). The patients were divided into several groups based on scintigraphic pattern of unifocal (UA), a multifocal (MFA), a focal/disseminated (FDA) and a disseminated (DA) autonomy. The early effects of therapy on thyroid function were assessed by evaluation of FT3 values of 786 patients during the 1st, 2nd, 3rd, 4th and 6th week after therapy. RESULTS: Successful elimination of thyroid autonomy as defined by normalization of FT3 and TSH levels was observed in 92.1% (582/632) of the patients. In 2.2% (14/632) of the patients, immunogenic hyperthyroidism following I-131 therapy was observed. There was no significant difference in the success rates in patients with UA and MFA of 94.9% and 96.1%, respectively, using similar target doses based on the amount of autonomous tissue. The success rate in MFA (96.6%) was similar if target dose was calculated based on the volume of the whole thyroid gland. Compared to MFA (96.6%), however, FDA and DA were associated with significantly lower success rate with 82.7% and 75.5%, respectively, although the target doses were not significantly different. Considering the quantitative Tc-99m uptake prior to therapy, there was no significant difference in the success rate for Tc-99m uptake < or = 3% and > 3%, while the success rate in patients with I-131 uptake of < or = 50% was significantly higher (p = 0.032) than in those with an uptake of > 50%. The determination of FT3 levels during the first 6 weeks after radioiodine therapy revealed a dependence of the FT3 decrease and FT3 increase on the scintigraphic pattern and thyroid function. Patients with FDA and DA with hyperthyroidism showed an increase of FT3 (> 2 to 14.7 pmol/l) in 11 to 18% of the cases, during the first 2 weeks after therapy which occurred significantly more frequently in patients with FDA and DA than in UA and MFA. A similar increase in FT3 level in patients with FDA and DA compared to patients with UA and MFA was observed in 317 patients with euthyroid pretherapeutic hormone levels. A decrease in FT3 level following radioiodine therapy was observed significantly more often and earlier in patients with UA and MFA with hyperthyroid values than in patients with FDA and DA during the first 6 posttherapeutic weeks. Concerning patients with euthyroid FT3 levels, the decrease in FT3 level was observed significantly more frequently in patients with UA and MFA only after 6 weeks following radioiodine therapy. CONCLUSION: In contrast to the multifocal autonomy (MFA), the target dose of 150 to 200 Gy based on total thyroid volume did not result in a comparably high success rate of approximately 95% in disseminated and focal/disseminated types of thyroid autonomy. Therefore, an increase of target dose of 200 to 300 Gy is recommended. The transient FT3 increase particularly observed in FDA and DA in the first weeks following radioiodine therapy makes short-term controls of thyroid function necessary, especially in patients with cardiac risk, in order to initiate necessary therapy.

Adult↗

PubMed1999

Imaging functional activation of the auditory cortex during focal repetitive transcranial magnetic stimulation of the primary motor cortex in normal subjects.

Positron emission tomography (PET) during focal repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising approach to study cortical connectivity in awake humans. However, the noise caused by the discharging magnetic coil might have confounding effects on the rTMS-related cortical activation pattern. In twelve healthy volunteers, 18-fluoro-2-deoxy-D-glucose (18FDG) PET was employed to visualize the functional activation of the primary auditory cortex (PAC) during 2 Hz rTMS of the left primary sensorimotor hand area. Magnetic stimuli (1800) were applied at an intensity of 140% of motor resting threshold during the uptake period of 18FDG. Though all subjects wore earplugs, rTMS-related noise induced a consistent bilateral increase of regional glucose utilization in the PAC (P < 0.05, corrected). Thus, rTMS-related acoustic input needs to be taken into account in combined rTMS/PET studies.

Adult↗