Discrepancies in thyroid uptake values, use of commercial thyroid probe systems versus scintillation cameras.
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Gamma Cameras↗
Biomedical subjects
W Robeson
Publications and source records attributed to W Robeson.
Fluorodopa positron emission tomography with an inhibitor of catechol-O-methyltransferase: effect of the plasma 3-O-methyldopa fraction on data analysis.
Flurodopa (FDOPA) is an analogue of L-di-hydroxyphenylalanine (L-dopa) used to assess the nigrostriatal dopamine system in vivo with positron emission tomography (PET). However, FDOPA/PET quantitation is complicated by the presence of the 3-O-methyl-FDOPA (3OMFD) fraction in brain and plasma. Pretreatment with entacapone (OR-611), a peripheral catechol O-methyl-transferase (COMT) inhibitor, greatly reduces the plasma 3OMFD fraction and provides an ideal situation to evaluate the contribution of the plasma 3OMFD fraction in several kinetic models of FDOPA uptake. We performed FDOPA/PET with and without the OR-611 preadministration in six Parkinson's disease (PD) patients. We measured the time-course of the plasma FDOPA and 3OMFD fractions using high-pressure liquid chromatography (HPLC). We calculated striato-occipital ratios (SOR), and estimated the striatal FDOPA uptake rate constant graphically using the plasma FDOPA and occipital tissue time activity curves (KiFD and KiOCC, respectively). We also estimated striatal dopa decarboxylase (DDC) activity (k3D) using a model incorporating independent measurements of 3OMFD transport kinetic rate constants. With the preadministration of OR-611, the pharmacological efficiency in plasma was prolonged significantly (21.1-37.7%; p < 0.01). We also observed significant mean elevations in SOR and KiOCC by 21.8 and 53.5%, respectively (p < 0.05). KiFD and k3D did not show significant change. We conclude that OR-611 prolongs the circulation time of FDOPA in the plasma but does not alter rate constants for striatal FDOPA uptake or decarboxylation.
Adult↗
Combined FDOPA and 3OMFD PET studies in Parkinson's disease.
UNLABELLED: PET has been used to quantify striatal 6-[18F]fluoro-L-dopa (FDOPA) uptake as a measure of presynaptic dopaminergic function. It has been suggested that the estimation of dopa-decarboxylation (DDC) rate, kD3, using a compartmental approach to dynamic FDOPA/PET data, can provide a better objective marker of parkinsonism. This modeling process, however, requires many assumptions to estimate DDC activity with acceptable errors. METHODS: We combined FDOPA 3-O-methyl-fluorodopa PET studies on three normal subjects and five Parkinson's disease patients. RESULTS: The contradicted modeling assumptions are: (a) the rate constants across the blood-brain barrier, KD1 and kD2, for 3OMFD and FDOPA were in similar range (ratio approximately equal to 1) and thus not equal to assumed values of KM1/KD1 of 2.3 derived from rat studies and applied to human FDOPA studies and (b) the KD1/kD2 ratio for frontal cortex was not equal to that for the striatum (0.70 +/- 0.15 versus 1.07 +/- 0.3; p < 0.002). Discriminant analyses indicate that simple estimates like the striatum-to-occipital ratio, or the graphically derived unidirectional transport rate constant (KiFD) separate normals from Parkinson's disease patients at least as accurately as estimates of striatal DDC activity (kD3). CONCLUSION: Measurements of striatal DDC activity with dynamic FDOPA/PET and compartmental modeling may be based on incorrect assumptions. Even though such complex models yield microparameters that may be applicable to certain clinical research demands, they may produce misleading results in other experimental settings.
Adult↗
Clinical significance of striatal DOPA decarboxylase activity in Parkinson's disease.
UNLABELLED: We performed dynamic PET studies with fluorodopa (FDOPA) in 9 normal volunteers and 16 patients with Parkinson's disease to investigate the applicability of dopa decarboxylase (DDC) activity measurements as useful markers of the parkinsonian disease process. METHODS: From the 3-O-methyl-FDOPA (3OMFD)/PET studies, we obtained mean population values of the kinetic rate constants for 3OMFD (K1M = 0.0400 and k2M = 0.0420). We applied these values to calculate striatal DDC activity using the FDOPA compartmental model. We estimated k3D in this group using dynamic FDOPA-PET and population mean K1M and k2M values. We then applied the mean population K1M and k2M values to estimate k3D(pop) to a new group (6 normal volunteers and 11 patients) studied only with dynamic FDOPA-PET. In all FDOPA/PET studies, we calculated striatal uptake rate constants (KiFD) using a graphical method and also measured the striato-occipital ratio (SOR). RESULTS: Although DDC activity has been postulated as a precise indicator of presynaptic nigrostriatal dopaminergic function, KiFD and SOR provided better between-group discrimination than did estimates of striatal DDC activity. KiFD and k3D(pop) both correlated significantly with quantitative disease severity ratings, with a similar degree of accuracy (r = 0.69 and 0.63 for k3D(pop) and KiFD, respectively; p < 0.01). CONCLUSION: Although estimated striatal DDC activity correlates with clinical disability, this measure is comparably less effective for early diagnosis. We conclude that a simple estimate such as striatal KiFD is superior to k3D measurements for most clinical and research applications.
Brain↗
Bladder wall radiation dose in humans from fluorine-18-FDOPA.
UNLABELLED: PET, in conjunction with 18F-fluorodopa (FDOPA), has become the standard technique to assess basal ganglia degeneration in patients with movement disorders. Based on published dosimetry data, the injected dose of FDOPA is limited to 111 Mbq (3 mCi) because of exposure to the bladder wall, which is the critical organ for such studies. These dosimetry studies are based on mathematical models for the bladder radioactivity accumulation and clearance when the subjects were asked to void approximately 2 hr after the intravenous injection of FDOPA. In this study, we improved the radiation dose estimate to the bladder wall using dynamic PET to image the bladder during the uptake phase as well as before and after voiding. METHODS: The subjects were tested on a new protocol. They were hydrated preinjection and given a first bladder void break at 40 min postinjection and a second void at the end of study at 120 min. RESULTS: The MIRD model, applied to the data collected from 10 adults of both sexes, yielded an average absorbed dose of 0.15 +/- 0.08 mGy/MBq (0.57 +/- 0.28 rad/mCi). CONCLUSION: This absorbed dose is significantly lower than previous estimates and allows for FDOPA injections up to 333 Mbq (9 mCi).
Adult↗
Assessment of disease severity in parkinsonism with fluorine-18-fluorodeoxyglucose and PET.
UNLABELLED: Fluorine-18-fluorodeoxyglucose (FDG) and PET have been used to identify an abnormal regional metabolic covariance pattern in Parkinson's disease (PD). To examine the potential use of this covariance pattern as a metabolic imaging marker for PD, we describe the Topographic Profile Rating (TPR), which is a method for calculating subject scores for this pattern in individual PD patients. We then assess the relationship between these metabolic measures and objective independent disease severity ratings. METHODS: Two independent groups of PD patients were studied with FDG-PET. Group A consisted of 23 patients (mean age 60.2 +/- 12.2; mean Hoehn and Yahr stages 2.4 +/- 1.3) and Group B had 14 patients (mean age 49.0 +/- 12.1; mean Hoehn and Yahr stage 3.2 +/- 1.2). The regional cerebral metabolic rates for glucose (rCMRGlc) in all patients in each group were measured. TPR was used to calculate subject scores for the disease-related covariance pattern on a patient-by-patient basis. RESULTS: In both PD patient groups, subject scores correlated with Hoehn and Yahr disease severity ratings (Group A: r = 0.59, p < 0.004; Group B: 0.57, p < 0.04), quantitative ratings for bradykinesia (Group A: r = 0.63, p < 0.002; Group B: r = 0.61, p < 0.03), rigidity (Group A: r = 0.59, p < 0.004; Group B: r = 0.59, p < 0.04), but not with tremor. CONCLUSION: These findings indicate that regional metabolic covariance patterns are robust imaging markers of disease severity. FDG-PET may be useful clinically in assessing parkinsonian disability and disease progression.
Adult↗
The metabolic topography of parkinsonism.
We used [18F]fluorodeoxyglucose/positron emission tomography (18F-FDG/PET) and a statistical model of regional covariation to study brain topographic organization in parkinsonism. We studied 22 patients with Parkinson's disease (PD), 20 age-matched normal volunteers, and 10 age- and severity-matched patients with presumed striatonigral degeneration (SND). We used FDG/PET to calculate global, regional, and normalized metabolic rates for glucose (GMR, rCMRglc, rCMRglc/GMR). Metabolic parameters in the three groups were compared using an analysis of variance, with a correction for multiple comparisons, and discriminant analysis. The scaled subprofile model (SSM) was applied to the combined rCMRglc dataset to identify topographic covariance profiles that distinguish PD patients from SND patients and normals. GMR, rCMRglc, and rCMRglc/GMR were normal in PD; caudate and lentiform rCMRglc/GMR was reduced in the SND group (p < 0.01). SSM analysis of the combined group of patients and normals revealed a significant topographic profile characterized by increased metabolic activity in the lentiform nucleus and thalamus associated with decreased activity in the lateral frontal, paracentral, inferior parietal, and parietooccipital areas. Individual subject scores for this profile were significantly elevated in PD patients compared with normals and SND patients (p < 0.001) and discriminated the three groups. In the PD group, subject scores for this factor correlated with individual subject Hoehn and Yahr (H & Y) scores (p < 0.02), and with quantitative rigidity (p < 0.01) and bradykinesia (p < 0.03) ratings, but not with tremor ratings. SSM analysis of right-left metabolic asymmetries yielded a topographic contrast profile that accurately discriminated mildly affected PD patients (H & Y Stage I) from normals. Our findings demonstrate that abnormal topographic covariance profiles exist in parkinsonism. These profiles have potential clinical application as neuroimaging markers in parkinsonism.
Adult↗
Quantitative brain FDG/PET studies using dynamic aortic imaging.
Positron emission tomography (PET) measurements of cerebral glucose utilization using 18F-fluorodeoxyglucose (FDG) are a useful tool in the investigation of localized brain function in normal and disease states. A major impediment to the application of FDG/PET in clinical investigation has been the need for arterial blood sampling to quantify cerebral glucose metabolism (CMRGlc). Qualitative studies, though informative in a variety of clinical settings, are of limited value for research applications and do not utilize the inherent quantitative nature of PET. We present a novel PET technique employing a whole-body PET tomograph with abdominal aortic imaging from 0 to 30 min as an alternative to arterial blood sampling to obtain the input function for cerebral metabolic rate calculations. Two or three arterial samples taken during the 10-45 min period were used to scale and extend the blood curve and the brain was imaged from 35-55 min post-injection. We performed 12 studies in which both arterial blood sampling and aortic scans were obtained. We found the correlation of global metabolic rates (GMR) when comparing the two techniques to be extremely high (R2 = 0.99). This suggests that the use of dynamic aortic imaging is less invasive and a viable alternative to arterial blood sampling in quantitative FDG/PET imaging.
Algorithms↗
Input functions for 6-[fluorine-18]fluorodopa quantitation in parkinsonism: comparative studies and clinical correlations.
UNLABELLED: PET has been used to quantify striatal 6-[18F]fluoro-L-dopa (FDOPA) uptake as a measure of presynaptic dopaminergic function. Striatal FDOPA uptake rate constants (Ki) can be calculated using dynamic PET imaging with measurements of the plasma FDOPA input function determined either directly or by several estimation procedures. METHODS: We assessed the comparative clinical utility of these methods by calculating the striato-occipital ratio (SOR) and striatal Ki values in 12 patients with mild to moderate PD and 12 age-matched normal volunteers. The plasma FDOPA time-activity curve (KiFD); the plasma 18F time-activity curve (KiP); the occipital time-activity curve (KiOCC); and a simplified population-derived FDOPA input function (KiEFD) were used to calculate striatal Ki. RESULTS: Mean values for all striatal Ki estimates and SOR were significantly lower in the PD group. Although all measured parameters discriminated PD patients from normals, KiFD and KiEFD provided the best between-group separation. KiFD, KiEFD and KiOCC measures correlated significantly with quantitative disease severity ratings, although KiFD predicted quantitative clinical disability most accurately. CONCLUSION: These results suggest that KiFD may be an optimal marker of the parkinsonian disease process. KiEFD may be a useful alternative to KiFD for most clinical research applications.
Adult↗
Striatal hypometabolism distinguishes striatonigral degeneration from Parkinson's disease.
Regional and global metabolic rates for glucose were estimated using 18F-fluorodeoxyglucose and positron emission tomography in 10 patients with a clinical likelihood of striatonigral degeneration (2 men and 8 women; mean age, 61.8 +/- 6.9 years; mean disease duration, 4.7 +/- 2.2 years; mean Hoehn and Yahr score, 3.5 +/- 0.8). Measures of brain glucose metabolism in these patients were compared with those for 10 age-matched normal volunteers, 10 disease severity-matched patients with Parkinson's disease (PD), and 10 disease duration-matched patients with PD. Normalized glucose metabolism was significantly reduced in the caudate (p < 0.03) and putamen (p < 0.003) as compared with that in normal and PD control subjects, and discriminated patients with striatonigral degeneration from control subjects (p < 0.002). Putamenal hypometabolism in patients with striatonigral degeneration correlated significantly with quantitative ratings of motor disability (p < 0.02). These results suggest that quantitative 18F-fluorodeoxyglucose positron emission tomography techniques may be useful in supporting a diagnosis of striatonigral degeneration in life, and in objectively assessing disease severity and potential therapeutic interventions.
Aged↗
Positron emission tomographic findings in Filipino X-linked dystonia-parkinsonism.
Regional and global metabolic rates for glucose (rCMRGlc and GMR) were estimated using [18F]fluorodeoxyglucose and positron emission tomography in 3 patients with Filipino X-linked dystonia-parkinsonism (lubag). In all 3 patients a selective reduction in normalized striatal glucose metabolism (rCMRGlc/GMR) was observed compared with 15 normal volunteer subjects. Presynaptic nigrostriatal function was assessed in these patients using [18F]fluorodopa and positron emission tomography. Striatal rate constants for [18F]flurodopa uptake were found to be in the normal range in all 3 patients with lubag. These findings suggest that the extrapyramidal manifestations of lubag are metabolically localized to the striatum and that clinical parkinsonism in these patients may be secondary to extranigral factors.
Adult↗
Striatal 18F-dopa uptake: absence of an aging effect.
L-[18F]6-Fluoro-DOPA (L-[18F]6-fluoro-3,4-dihydroxyphenylalanine; FDOPA) has been used with quantitative positron emission tomography (PET) to assess presynaptic nigrostriatal dopaminergic function in life. The relationship of estimated kinetic rate constants for striatal FDOPA uptake [Ki(FDOPA)] to the normal aging process has been the subject of conflicting reports. Resolution of this issue has been hampered by methodological differences in previous FDOPA/PET investigations. We studied 19 healthy normal subjects (aged 27-77 years) and measured striatal Ki-(FDOPA) according to each of the earlier methods. While significant correlations (p < 0.005) existed between Ki(FDOPA) values estimated by the various techniques, none correlated with normal aging. We conclude that normal striatal Ki(FDOPA) values estimated using quantitative FDOPA/PET are uncorrelated with the aging process.
Adult↗
Noninvasive quantitative fluorodeoxyglucose PET studies with an estimated input function derived from a population-based arterial blood curve.
The authors have developed a technique to estimate input functions from a population-based arterial blood curve in positron emission tomography (PET) studies with fluorine-18 fluorodeoxyglucose (FDG). A standardized pump injection was used in 34 subjects. A population-based blood curve was generated based on the first 10 subjects. In the remaining 24 subjects, an estimated input function (EIFa) was obtained by scaling the population-based curve with two arterial blood samples, one obtained at 10 minutes and the other at 45. Time integrals for EIFa and the real arterial input function (RIF) were in excellent agreement (r = .998, P < .0001). Cerebral metabolic rates for glucose calculated with EIFa and RIF and the autoradiographic method also correlated excellently (r = .992, P < .0001). Analogous correlations were achieved with arterialized venous samples as scaling factors. These results suggest that individually scaled, population-derived input functions may serve as an adequate alternative to continuous arterial blood sampling in quantitative FDG-PET imaging.
Adult↗
The use of a new radiopharmaceutical, 97Ru-DISIDA, and of 99Tcm-sulphur colloid for the simultaneous evaluation of duodenogastric reflux and gastric emptying.
There is no consensus or a uniform technique for measuring gastric emptying and numerous modalities have been reported. We report here the results obtained using a modification of the published techniques for the simultaneous measurement of duodenogastric reflux and gastric emptying utilizing simultaneously the recently developed radiopharmaceutical 97Ru-DISIDA, intravenously, and the oral administration of 99Tcm-sulphur colloid incorporated in a 'solid' test meal.
Administration, Oral↗
A new cholescintigraphic agent: ruthenium-97-DISIDA.
These are the first human experiments with 97Ru-DISIDA, a potentially new alternative to 131I-rose bengal where delayed imaging is indicated. 97Ru has a convenient half life. A DISIDA labeling kit was utilized to prepare the radiotracer for 17 patients (age 6 weeks-84 years). The cholescintigraphic data correlated well with other imaging procedures and with clinical findings. Dosimetric calculations were carried out and were compared with the radiation burden associated with the use of 99mTc-DISIDA and 131I-rose bengal.
Biliary Tract Diseases↗
Early detection of anthracycline-induced cardiotoxicity by stress radionuclide cineangiography in conjunction with Fourier amplitude and phase analysis.
Thirty-three cases of anthracycline related cardiotoxicity occurred in our institution in patients with a previously negative cardiovascular history, physical examination, and normal ECG. A total of 95 RNCA studies were performed in this group (73 studies included both rest and exercise RNCA). Twenty-one patients had two or more serial studies. Seventeen had a normal, baseline prechemotherapy study and 16 had studies done following the initiation of therapy. Fourier analysis, consisting of amplitude and phase images, were created for each study. In the subset with a baseline study, the rest LVEF became abnormal first in two of 17 patients (12%), the rest or stress LVEF in ten of 17 (59%), the rest Fourier image analysis in ten of 17 (59%), and the rest or stress Fourier image analysis in 16 of 17 (94%). In the subset without a baseline study, the rest LVEF was abnormal in ten of 16 (63%), the rest or stress LVEF in 15 of 16, (94%), the rest Fourier image analysis in 16 of 16 (100%), and the rest or stress Fourier image analysis in 16 of 16 (100%). The authors conclude that: 1) the exercise RNCA is superior to the rest RNCA alone in the early detection of anthracycline related cardiotoxicity, 2) the single most sensitive indicator of cardiotoxicity is Fourier image analysis; and 3) sequential rest and stress RNCA studies with Fourier amplitude and phase analysis is the most sensitive, noninvasive method of evaluating patients who receive potentially cardiotoxic agents.
Adolescent↗
Fourier amplitude and phase analysis in the clinical evaluation of patients with cardiomyopathy.
Fifty-four patients with a cardiomyopathy were studied by RNCA and Fourier amplitude and phase image analysis. The study group included patients with ischemic cardiomyopathy (27) and an equal number of patients with a primary cardiomyopathy: drug-induced (22), idiopathic (three), radiation-induced (one), and amyloidosis (one). Twenty-eight patients had rest studies alone and 26 had both rest and stress studies (80 total). The mean rest LVEF in the ischemic group was 27.9%, in the drug-induced group 36.5%, and in the idiopathic group 30%. The stress LVEF decreased in 92% of patients with ischemic cardiomyopathy and 45% of patients with primary (drug-induced) cardiomyopathy. Fourier amplitude and phase images were generated for each study. Amplitude and phase images were abnormal in all patients with an ischemic cardiomyopathy. LV amplitude abnormalities were regional and phase was directional. A zone of dysynergy on phase analysis was present in 44% of patients with ischemic cardiomyopathy. In the drug-induced primary cardiomyopathy group, all patients had abnormal amplitude and 86% had abnormal phase. Amplitude abnormalities were global rather than regional and phase patterns were nondirectional. Only one patient had a zone of dysynergy on the phase image. We conclude that the stress LVEF alone cannot consistently differentiate between ischemic and primary cardiomyopathies and that Fourier amplitude and phase analysis may be useful in determining the etiology of a cardiomyopathy (ischemic vs primary).
Adolescent↗
A clinical evaluation of the RNCA study using Fourier filtering as a preprocessing method.
Forty-one patients (25 male, 16 female) were studied by RNCA in our institution. There were 42 rest studies and 24 stress studies (66 studies total). Sixteen patients were normal, 15 had ASHD, seven had a cardiomyopathy, and three had left-sided valvular regurgitation. Each study was preprocessed using both the standard nine-point smoothing method and Fourier filtering. Amplitude and phase images were also generated. Both preprocessing methods were compared with respect to image quality, border definition, reliability and reproducibility of the LVEF, and cine wall motion interpretation. Image quality and border definition were judged superior by the consensus of two independent observers in 65 of 66 studies (98%) using Fourier filtered data. The LVEF differed between the two processes by greater than .05 in 17 of 66 studies (26%) including five studies in which the LVEF could not be determined using nine-point smoothed data. LV wall motion was normal by both techniques in all control patients by cine analysis. However, cine wall motion analysis using Fourier filtered data demonstrated additional abnormalities in 17 of 25 studies (68%) in the ASHD group, including three uninterpretable studies using nine-point smoothed data. In the cardiomyopathy/valvular heart disease group, ten of 18 studies (56%) had additional wall motion abnormalities using Fourier filtered data (including four uninterpretable studies using nine-point smoothed data). We conclude that Fourier filtering is superior to the nine-point smooth preprocessing method now in general use in terms of image quality, border definition, generation of an LVEF, and cine wall motion analysis. The advent of the array processor makes routine preprocessing by Fourier filtering a feasible technologic advance in the development of the RNCA study.
Adult↗