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G J Meyer

Publications and source records attributed to G J Meyer.

At least 19 recordsLinked to original sources
PubMed2004

Pre-operative localisation of hyperfunctional parathyroid tissue with 11C-methionine PET.

PURPOSE: Previous studies have shown high sensitivity of positron emission tomography (PET) with 11C-methionine in the pre-operative localisation of parathyroid adenoma and hyperplasia. Nonetheless, in secondary and tertiary hyperparathyroidism (HPT) and in patients with recurrent disease, pre-operative localisation of adenomatous (PTA) or hyperplastic tissue is still a problem with all available methods. The aim of this study was to define the optimal imaging protocol and to compare the diagnostic value of 11C-methionine PET and 99mTc-methoxyisobutylisonitrile (MIBI) single-photon emission computed tomography (SPECT): in particular, we wished to define the benefit of 11C-methionine in those patients with inconclusive or negative conventional imaging. METHODS: Thirty highly pre-selected patients with HPT were enrolled. Sixteen patients had primary HPT, 12 patients had secondary HPT, and two patients had recurrences of parathyroid carcinomas. All patients had ultrasound of the neck, dual-phase scintigraphy with 99mTc-MIBI and PET with 11C-methionine. SUV(parathyroid)/SUV(cervical soft tissue) (target-to-background) and SUV(parathyroid tissue)/SUV(thyroid tissue) (target-to-non-target) ratios were calculated. After surgery, histology of specimens was obtained in all patients but one. RESULTS: In 12 patients with secondary or tertiary HPT, 36 hyperplastic parathyroid glands were histologically verified. Twenty-five of 36 lesions (69%) were detected with 11C-methionine PET and 17 (47%) with 99mTc-MIBI scintigraphy. PET studies were positive in 17/18 (94%) cases in which HPT was related to adenomas or carcinomas. 99mTc-MIBI scintigraphy/SPECT yielded pathological lesions in 9/18 cases (50%). All eight atypical localisations of parathyroid glands were detected with PET but only six of the eight were detected with 99mTc-MIBI scintigraphy/SPECT. In 10/11 patients with recurrent HPT and non-diagnostic scintigraphy/SPECT, hyperfunctional parathyroid tissue was identified with 11C-methionine PET. The highest SUV(parathyroid)/SUV(cervical soft tissue) ratio was found 10 min, and the highest SUV(parathyroid tissue)/SUV(thyroid tissue) ratio 40 min post injection. In three patients clear delineation of hyperfunctional tissue was only achieved after 40 min post injection. CONCLUSION: 11C-methionine PET is a clinically useful method in highly pre-selected patients with recurrent primary HPT as well as in secondary and tertiary HPT if ultrasound and 99mTc-MIBI SPECT are inconclusive or negative. PET imaging of atypical PTA localisations is more accurate than conventional scintigraphy. In order to achieve optimal contrast of parathyroid glands versus thyroid tissue and adjacent soft tissue, imaging at both 10 min and 40 min is recommended.

Adult↗
PubMed2003

Positron emission tomography with 11C-acetate and 18F-FDG in prostate cancer patients.

Visualisation of primary prostate cancer, its relapse and its metastases is a clinically relevant problem despite the availability of state-of-the-art methods such as CT, MRI, transrectal ultrasound and fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET). The aim of this study was to evaluate the efficacy of carbon-11 acetate and (18)F-FDG PET in the detection of prostate cancer and its metastases. Twenty-five patients were investigated during the follow-up of primary prostate cancer, suspected relapse or metastatic disease using (11)C-acetate PET; 15 of these patients were additionally investigated using (18)F-FDG PET. Fourteen patients were receiving anti-androgen treatment at the time of the investigation. Lesions were detected in 20/24 (83%) patients using (11)C-acetate PET and in 10/15 (75%) patients using (18)F-FDG PET. Based on the results of both PET scans, one patient was diagnosed with recurrent lung cancer. Median (18)F-FDG uptake exceeded that of (11)C-acetate in distant metastases (SUV =3.2 vs 2.3). However, in local recurrence and in regional lymph node metastases, (11)C-acetate uptake (median SUVs =2.9 and 3.8, respectively) was higher than that of (18)F-FDG (median SUVs =1.0 and 1.1, respectively). A positive correlation was observed between serum PSA level and both (11)C-acetate uptake and (18)F-FDG uptake. (11)C-acetate seems more useful than (18)F-FDG in the detection of local recurrences and regional lymph node metastases. (18)F-FDG, however, appears to be more accurate in visualising distant metastases. There may be a role for combined (11)C-acetate/(18)F-FDG PET in the follow-up of patients with prostate cancer and persisting or increasing PSA.

Acetates↗
PubMed2002

Establishment of radioactive astatine and iodine uptake in cancer cell lines expressing the human sodium/iodide symporter.

The sodium/iodide symporter (NIS) has been recognized as an attractive target for radioiodine-mediated cancer gene therapy. In this study we investigated the role of human NIS for cellular uptake of the high LET alpha-emitter astatine-211 ((211)At) in comparison with radioiodine as a potential radionuclide for future applications. A mammalian NIS expression vector was constructed and used to generate six stable NIS-expressing cancer cell lines (three derived from thyroid carcinoma, two from colon carcinoma, one from glioblastoma). Compared with the respective control cell lines, steady state radionuclide uptake of NIS-expressing cell lines increased up to 350-fold for iodine-123 ((123)I), 340-fold for technetium-99m pertechnetate ((99m)TcO(4)(-)) and 60-fold for (211)At. Cellular (211)At accumulation was found to be dependent on extracellular Na(+) ions and displayed a similar sensitivity towards sodium perchlorate inhibition as radioiodide and (99m)TcO(4)(-) uptake. Heterologous competition with unlabelled NaI decreased NIS-mediated (211)At uptake to levels of NIS-negative control cells. Following uptake both radioiodide and (211)At were rapidly (apparent t(1/2) 3-15 min) released by the cells as determined by wash-out experiments. Data of scintigraphic tumour imaging in a xenograft nude mice model of transplanted NIS-modified thyroid cells indicated that radionuclide uptake in NIS-expressing tumours was up to 70 times ((123)I), 25 times ((99m)TcO(4)(-)) and 10 times ((211)At) higher than in control tumours or normal tissues except stomach (3-5 times) and thyroid gland (5-10 times). Thirty-four percent and 14% of the administered activity of (123)I and (211)At, respectively, was found in NIS tumours by region of interest analysis ( n=2). Compared with cell culture experiments, the effective half-life in vivo was greatly prolonged (6.5 h for (123)I, 5.2 h for (211)At) and preliminary dosimetric calculations indicate high tumour absorbed doses (3.5 Gy/MBq(tumour) for (131)I and 50.3 Gy/MBq(tumour) for (211)At). In conclusion, NIS-expressing tumour cell lines of different origin displayed specific radionuclide uptake in vitro and in vivo. We provide first direct evidence that the high-energy alpha-emitter (211)At is efficiently transported by NIS. Application of (211)At may direct higher radiation doses to experimental tumours than those calculated for (131)I. Thus, (211)At may represent a promising alternative radionuclide for future NIS-based tumour therapy.

Adenocarcinoma↗
PubMed2001

Crowded Cu(I) complexes involving benzo[h]quinoline: pi-stacking effects and long-lives excited states.

The Friedländer condensation was employed to synthesize two series of 3,3'-polymethylene bridged ligands, L, based on 2-(2'-pyridyl)-benzo[h]quinoline and 2,2'-bibenzo[h]quinoline (BHQ) along with the fully aromatic naphtho[1,2-b]-1,10-phenanthroline. Complexes [Cu(L)(2)](+) were prepared as their perchlorate or hexafluorophosphate salts. The solution state structures were analyzed by NMR and shielding effects reflected significant interligand pi-stacking interaction in the complexes. Solid-state structures of the complexes where L = 3,3'-tetramethylene-2,2'-bibenzo[h]quinoline or naphtho[1,2-b]-1,10-phenanthroline were determined by X-ray analysis. The tetramethylene bridged complex showed a highly distorted coordination geometry with the BHQ rings of opposing ligands pi-stacked at a interplanar distance of about 3.37 A. Complexes of the BHQ series showed a pronounced MLCT absorption maximum which shifted bathochromically from 496 to 610 nm as the 3,3'-bridge decreased from 4 to 2 carbons. The BHQ complexes luminesced strongly in CH(2)Cl(2) solution and the tetramethylene-bridged system showed the longest yet recorded excited-state lifetime for a copper MLCT excited state, tau = 5.3 micros and Phi = 0.10.

Chemical Phenomena↗
PubMed2001

The hard science of Rorschach research: what do we know and where do we go?

As the final article in the Special Series on "The Utility of the Rorschach for Clinical Assessment," the authors provide an overview of this instrument's current status. They begin with a thorough review of global and focused meta-analyses, including an expanded analysis of K. C. H. Parker, R. K. Hanson, and J. Hunsley's (1988) data set, and conclude that Rorschach, Minnesota Multiphasic Personality Inventory, and IQ scales each produce roughly similar effect size magnitudes, although all tests have greater validity for some purposes than for others. Because this evidentiary foundation justifies addressing other issues, the authors build on contributions to the Special Series to identify 11 salient theoretical and empirical gaps in the Rorschach knowledge base and make recommendations for addressing these challenges to further the evolution of the Rorschach and document its strengths and inherent limitations.

Humans↗
PubMed2001

Superiority of form% over Lambda for research on the Rorschach Comprehensive System.

Lambda is an important variable in the Rorschach Comprehensive System. However, because of the way it is calculated it has properties that can produce problems for parametric statistical analyses. We illustrate these difficulties and encourage the use of Form% (i.e., pure form responses/total responses) instead of Lambda in research. Form% is easy to calculate, and it is conceptually and mathematically comparable to Lambda. Because it is much more normally distributed, Form% is suitable to use in parametric analyses (e.g., t tests, analyses of variance, correlations, factor analyses, multiple regressions).

Data Interpretation, Statistical↗
PubMed2001

Psychological testing and psychological assessment. A review of evidence and issues.

This article summarizes evidence and issues associated with psychological assessment. Data from more than 125 meta-analyses on test validity and 800 samples examining multimethod assessment suggest 4 general conclusions: (a) Psychological test validity is strong and compelling, (b) psychological test validity is comparable to medical test validity, (c) distinct assessment methods provide unique sources of information, and (d) clinicians who rely exclusively on interviews are prone to incomplete understandings. Following principles for optimal nomothetic research, the authors suggest that a multimethod assessment battery provides a structured means for skilled clinicians to maximize the validity of individualized assessments. Future investigations should move beyond an examination of test scales to focus more on the role of psychologists who use tests as helpful tools to furnish patients and referral sources with professional consultation.

Diagnosis, Differential↗
PubMed2001

[1-(11)C]Acetate as a quantitative perfusion tracer in myocardial PET.

UNLABELLED: Our objective was to investigate the properties of [1-(11)C]acetate as a quantitative perfusion tracer for myocardial PET studies. METHODS: We determined the flow dependence of the effective acetate extraction by a comparison with [(13)N]ammonia in 24 patients at rest (n = 8) and under pharmacologic vasodilation (n = 16). Furthermore, we compared the statistical quality of the perfusion values derived with both tracers. Quantification was based on an irreversible 2-compartment model for [(13)N]ammonia and a reversible 1-compartment model for [1-(11)C]acetate. Area-conserving polar maps were used to determine the correlation between the unidirectional uptake parameters of both tracers on a pixel-by-pixel basis for the whole left ventricular myocardium. RESULTS: A fit of a generalized Renkin-Crone formula to the data yielded the unidirectional acetate extraction fraction E(f) = 1 - 0.64e(-1.20/f). An extraction correction based on this formula led to good quantitative agreement of perfusion values derived with [(13)N]ammonia and [1-(11)C]acetate over the whole observed flow range (average difference of flow values, 3%; correlation coefficient, 0.96). This agreement proved the applicability of acetate as a quantitative perfusion tracer even under stress conditions. An analysis of the statistical properties of the parameter estimates showed, moreover, that statistical errors were reduced by a factor of nearly 2 in comparison with ammonia. CONCLUSION: [1-(11)C]acetate allows accurate quantification of myocardial perfusion with PET at rest as well as under stress conditions. The use of acetate leads to distinctly improved statistical accuracy for the perfusion estimates in comparison with ammonia. This accuracy facilitates the generation of reliable parametric polar maps, which are especially useful for clinical application of myocardial perfusion quantification.

Acetic Acid↗
PubMed2001

Introduction to the final special section in the special series on the utility of the Rorschach for clinical assessment.

A special Series was organized to clarify the merits of the Rorschach for clinical assessment. Except for a neutral meta-analytic review, articles were solicited from scholars known to have opposing views on the Rorschach. The authors participated in a structured, sequential, evidence-based dialogue that focused on strengths and limitations when using the Rorschach for applied purposes. The debate has taken place over 4 iterations, with later articles building on and reacting to those generated earlier. The first 5 articles in the Special Series were published earlier (G. J. Meyer, 1999), and the final 6 articles are published in this issue of Psychological Assessment. This article provides a brief overview of the full Special Series and an introduction to the 6 articles contained in this Special Section. The Special Series provides clinicians, researchers, educators, and students with a thorough review of the evidence and logic that are critical for understanding the Rorschach's strengths and limitations in clinical assessment.

Humans↗
PubMed2000

Tuning charge recombination rate constants through inner-sphere coordination in a copper(I) donor-acceptor compound.

The coordination compounds [Cu(bpy-MV2+)(PPh3)2](PF6)3, where bpy-MV2+ is the 1-(4-(4'-methyl-2,2'-bipyridin-4-yl)butyl)-1'-methyl-4, 4'-bipyridinediium(2+) cation, and [Cu(dmb)(PPh3)2](PF6), where dmb is 4,4'-dimethyl-2,2'-bipyridine, have been prepared and characterized. Visible light (417 nm) excitation of [Cu(bpy-MV2+)(PPh3)2]3+ at room temperature leads to rapid intramolecular electron transfer, kcs > 1 x 10(8) s-1, to form a charge-separated state with an electron localized on the pendant viologen group and a copper(II) metal center, abbreviated [CuII-bpy-MV.+]. This state recombines to ground-state products with first-order rate constants that can be tuned with solvent over a approximately 10(7)-10(5) s-1 range. The activation parameters were determined from temperature-dependent electron-transfer data with Arrhenius analysis. A model is proposed wherein a solvent molecule is coordinated to Cu(II) in the charge-separated state, [(S)CuII-bpy-MV.+]. Visible light excitation of [Cu(dmb)(PPh3)2](PF6) in argon-saturated dichloromethane produces long-lived photoluminescent excited states, tau = 80 ns, that are dynamically quenched by the addition of Lewis basic solvents. The measured quenching constants each correlate well with the lifetime of the charge-separated state measured after excitation of [Cu(bpy-MV2+)(PPh3)2]3+ in the corresponding solvent.

Journal Article↗
PubMed2000

Dopamine transporter binding in Gilles de la Tourette syndrome.

Preliminary studies in patients with Gilles de la Tourette syndrome (TS) provided evidence of presynaptic dopaminergic dysfunction, demonstrating increased reuptake sites. Therefore we investigated striatal dopamine transporter binding in 12 TS patients and 9 control subjects using single photon emission computed tomography and 123I-labeled 2beta-carbomethoxy-3beta-(4-iodophenyl)tropane. In TS patients we found significantly higher relative striatal activity ratios (mean +/- SD 12.33 +/- 3.58) than in controls (9.36 +/- 1.35, P< 0.05). Only five patients, however, showed striatum/occipital cortex ratios more than 2 SD above the normal means. Seven patients had activity ratios within the average ratio of the control group plus 2 SD. Regarding the relationship between clinical parameters and striatum/occipital cortex ratios, we found an association between binding ratios and "self-injurious behavior" and "lack of impulse control." This study corroborates previous data suggesting an involvement of the dopaminergic system in TS pathology. Our results demonstrate that an increase in dopamine transporter capacity is a possible but not a necessary alteration, and which appears more likely when self-injurious behavior and lack of impulse control are associated.

Adult↗
PubMed2000

Dopamine D2 receptor imaging in Gilles de la Tourette syndrome.

OBJECTIVES: To examine postsynaptic dopamine D2 receptors in Tourette syndrome (TS). MATERIAL AND METHODS: Seventeen patients and a control group were investigated using single photon emission computed tomography (SPECT) and iodobenzamide (123I-IBZM). RESULTS: In neuroleptic treated patients (n = 7) 123I-IBZM-binding was significantly reduced compared to both normal controls (P < 0.0001) and unmedicated patients (P < 0.001). In unmedicated patients (n = 10) mean binding ratio did not differ from that of control group. Patients in advanced stages of the disease, however, revealed significantly reduced relative striatal binding compared to patients in the early stages (P<0.005) and normal controls (P<0.0001). CONCLUSION: The results lend further support to the hypothesis that the dopamine receptor is involved in TS pathology. During the natural course of the disease tics often improve in early adulthood. It is suggested that this spontaneous recovery from tics may be associated with reduced receptor binding capacity.

Adolescent↗