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Biomedical subjects

A J van Dongen

Publications and source records attributed to A J van Dongen.

5 recordsLinked to original sources
PubMed2000

Minimizing liver, bowel, and gastric activity in myocardial perfusion SPECT.

UNLABELLED: When using 99mTc-tetrofosmin for myocardial perfusion SPECT, increased liver, intestinal, or gastric activity may create a major problem in the visual and quantitative interpretation Of the inferoposteroseptal walls, particularly at rest. The aim of this study was to determine what measures were required to minimize this extracardial activity. METHODS: Ninety-seven patients had a SPECT scan at rest without attenuation correction. They were divided into 3 groups. Preparation consisted of no action taken (group 1), 150 mL whole milk 10 min after administration of tetrofosmin (group 2), or 450 mL water 10 min before acquisition (group 3). A further 55 patients had a SPECT scan at rest with attenuation correction. They were also divided into 3 groups, and preparation consisted of 150 mL whole milk 10 min after administration of tetrofosmin (group 4), 450 mL water 10 min before acquisition (group 5), or both whole milk and water (group 6). The presence of activity in liver, bowel, and stomach was determined visually on reconstructed images. Activity was defined as interfering when it might result in either an underestimation or an overestimation of the uptake in the myocardial wall. RESULTS: Interfering activity was seen in 83% of the patients in group 1, in 74% in group 2, in 33% in group 3, in 61% in group 4, in 67% in group 5, and in 20% of group 6. CONCLUSION: The interpretation of inferoposteroseptal wall activity on myocardial rest SPECT images is facilitated by having the patient drink both whole milk and water at specified times before data acquisition.

Adult↗
PubMed1997

In vitro and in vivo detection of functional somatostatin receptors in canine insulinomas.

UNLABELLED: Ten dogs with hypoglycemia due to insulinomas were studied to assess the expression of somatostatin receptors (SSTRs) in canine insulinomas and its potential diagnostic value. METHODS: The response of circulating glucose and insulin concentrations to the subcutaneous administration of a somatostatin analog, octreotide, was measured. SSTRs were visualized in vitro by autoradiography. [Iodine-125-Tyr3]-octreotide and [125I-Tyr11]-somatostatin-14 (SRIF-14) were used as radioligands. SPECT was performed 6 hr after the injection of [111In-DTPA-D-Phe1]-octreotide. RESULTS: After subcutaneous injection of 50 micrograms octreotide, plasma glucose concentration rose from 2.3 +/- 0.2 mmol/liter to 3.2 +/- 0.3 mmol/liter at 3.5 hr (p < 0.05) and plasma insulin concentration decreased from 451 +/- 135 pmol/liter to a nadir of 249 +/- 115 pmol/liter at 30 min (p < 0.05). In vitro autoradiography revealed that all primary insulinomas and their metastases had specific SSTRs for both [125I-Tyr3]-octreotide and [126I-Tyr11]-SRIF-14. Scatchard analysis of SSTR binding in the tumor tissue of one dog revealed high-affinity binding sites for [125I-Tyr3]-octreotide (dissociation constant (Kd) 1.7 nM, maximum binding capacity (Bmax) 499 fmol/mg membrane protein). The primary tumor and/or metastases in five of six dogs could be visualized and localized by SPECT with [111In-DTPA-D-Phe1]-octreotide. In the remaining dog, multiple metastases (< 3 mm) were found in the liver at necropsy, apparently too small to be visualized by SPECT. CONCLUSION: The in vitro autoradiography and ligand binding studies indicate that canine insulinomas express one type of SSTR. This is in contrast with findings in humans where, on the basis of ligand binding studies, different subtypes of SSTRs have been identified. The uniformity of SSTRs, their high frequency of expression and the high incidence of metastatic disease make canine insulinomas very suitable for investigation of the value of SRIF analogs in the diagnosis and treatment of metastasized endocrine pancreatic tumors.

Animals↗
PubMed1991

Can technetium 99m bisdiethylphosphinoethanebis-t butylisocyanide (99mTc-DEPIC) be used for routine radionuclide ventriculography?

Radionuclide ventriculography is a useful investigation in the evaluation of cardiac function. Generally, in vivo technetium 99m-labelled red blood cells (RBC) yield good quality images in ventriculography. However, it is widely believed that some drugs have an adverse effect on RBC labelling. Zanelli et al. (1987) developed a radiopharmaceutical (technetium 99m bis-diethylphosphinoethanebis-t-butylisocyanide, 99mTc-DEPIC) to obtain better results in patients using such drugs. We undertook a prospective study of 6 patients with cardiovascular and/or pulmonary disease using several kinds of drugs to evaluate imaging of the cardiac blood pool with 99mTc-DEPIC and in vivo labelled 99mTc-RBC. After injection, blood samples were taken, and gated equilibrium blood pool studies were performed. The radiochemical purity of the injected 99mTc-DEPIC varied from 76.4 to 93.6% (mean 86.4%, SD 5.7%). The protein (pre-albumin) binding was 100%. Biological half-life in blood varied from 3.3 to 4.7 h (mean 4.1 h, SD 0.5 h). For 99mTc-RBC no significant blood disappearance was seen for 8 h. The percentage of RBC-bound 99mTc varied from 96.9% to 98.3% (mean 97.0%, SD 0.5%) and was stable for at least 8 h. The heart-to-lung, heart-to-spleen, and heart-to-liver ratios were higher for 99mTc-RBC than for 99mTc-DEPIC. Furthermore, 99mTc-DEPIC showed a significant decline of the ejection fraction with time. Visually, the images with 99mTc-RBC were superior to those with 99mTc-DEPIC, especially a few hours after injection. According to our findings, in vivo labelling of 99mTc-RBC is still the method of choice for routine radionuclide ventriculography.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular Diseases↗
PubMedDate not supplied

Good clinical practice, a transparent way of life. A review.

Investigators are regarded as central to the concept of clinical trials. Apart from bearing scientific responsibility, they will be confronted with a great number of ethical dilemma's concerning, amongst others, the justification and design of the trial, subject selection and informed consent, and presentation of the trial results. The ethical principles of biomedical research should be observed in accordance with a consistent moral code. The moral code of Good Clinical Practice (GCP) was developed in order to rule out inconsistencies. The principal tenets are that clinical trials should be good science, verifiable, monitored, well documented, and that they comply with the highest ethical standards. The principles of GCP are the protection of the rights of human subjects, integrity and reproducibility of data, and transparency of conduct.

Clinical Trials as Topic↗