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Biomedical subjects

E P Ritter

Publications and source records attributed to E P Ritter.

At least 19 recordsLinked to original sources
PubMed2002

Does intravenous ondansetron affect gastric emptying of a solid meal, gastric electrical activity or blood hormone levels in healthy volunteers?

BACKGROUND: In previous studies, tropisetron has been shown to accelerate gastric emptying of a solid meal. However, it is uncertain whether other specific 5-hydroxytryptamine-3 receptor antagonists, such as ondansetron, also have a gastroprokinetic effect in humans. AIM: To evaluate the effect of ondansetron on gastric half-emptying time (T1/2) of a solid meal, gastric myoelectrical activity and hormone levels in 14 healthy volunteers. METHODS: In a placebo-controlled, randomized, crossover study, we investigated the effects of ondansetron (8 mg intravenously) on the gastric emptying of solids (by scintigraphy), gastric myoelectrical activity (by electrogastrography) and the post-prandial release of cholecystokinin, gastrin, human pancreatic polypeptide, gastric inhibitory polypeptide, vasoactive intestinal polypeptide, motilin, substance P and galanin. RESULTS: The average T1/2 values were 86 min and 85.5 min without lag time (P=0.082) and 92 min and 93 min with lag time (P=0.158) for the placebo and ondansetron treatments, respectively. The average T1/2 of female volunteers was significantly longer than that of male volunteers. The dominant gastric electrical frequency and hormone plasma concentrations were not altered by ondansetron. CONCLUSIONS: Ondansetron did not affect the gastric emptying of solids, the dominant gastric electrical frequency or the plasma concentrations of the analysed gastrointestinal peptides.

Adult↗
PubMed2001

Deactivation of thalamocortical activity is responsible for suppression of parkinsonian tremor by thalamic stimulation: a 99mTc-ECD SPECT study.

Four patients with Parkinson's disease (PD) achieved excellent improvement of their unilateral tremor by chronic deep brain stimulation (DBS) of the contralateral ventral intermediate (Vim) nucleus of the thalamus. Repeated measurements of cerebral blood flow were obtained 14 days apart off and on stimulation using 99mTc-ECD SPECT. Subjects were scanned at rest and the data were compared with those of normal healthy volunteers. During stimulation, there were highly significant deactivations in the motor area and supplementary motor area on the electrode side and in the prefrontal area and the anterior cingulum bilaterally. No cerebellar deactivation was detected. We conclude that the mechanism responsible for suppression of parkinsonian tremor by thalamic stimulation is deactivation of thalamocortical activity.

Aged↗
PubMed1995

Separation of autonomous function from cell density in non-immunogenic hyperthyroidism. I. Quantification by double-isotope parametric scintigraphy.

UNLABELLED: A new quantitative subtraction method of thyroid scans is proposed which shows that regional function (F) by far exceeds regional cellularity or cell density (C) in potentially toxic thyroidal areas of non-immunogenic hyperthyroidism (NIH). METHODS: A multistep processing of radioiodine and MIBI thyroid scans of patients with non-immunogenic hyperthyroidism led to normalized images of regional function excess and of perinodular enhancement. Two numeric factors were derived from regions of interest: Q (cell density ratio) comparing MIBI uptake in autonomous and suppressed areas and T (toxicity index): the maximal F/C contrast. RESULTS: Q never exceeded 61; T, however, expanded toxicity levels over a range of 6-8735 with toxic adenomas (median = 165) and with hot areas of multifocal functional autonomy (median = 15). T was weakly correlated to serum TT3 (r = 0.41), but not to autonomous tissue mass, ultrasonographic or cytologic criteria. CONCLUSIONS: T is governed by inherent features of autonomous tissue and the response of the imbedded thyroid tissue to TSH stimulation. This standardized technique consolidates experiences from visual analysis; the huge T range mirrors the natural evolution from compensated autonomy towards hyperthyroid, decompensated stages.

Diagnosis, Differential↗
PubMed1994

Dual-isotope SPET 201Tl rest/99mTc-MIBI stress: one-day protocol for pre-operative myocardial imaging?

We compared the results of a rest 201TI/stress 99mTc-MIBI protocol, both by means of separate single isotope and simultaneous dual isotope acquisition, with a standard stress/rest 99mTc-MIBI 2-day protocol in 11 patients with low probability of CAD and 14 patients with chronic CAD. In patients with CAD 406 segments (sgs) were analysed. In the standard protocol 119 sgs were classified as pathological of which 50.4% were fixed and 49.6% reversible defects. With the MIBI-stress/TI-rest single 33% of 119 pathological sgs were fixed and 67% reversible defects. With the MIBI-stress/TI-rest dual only 20% were fixed and 80% reversible defects. The reversibility of 59 MIBI-stress/MIBI-rest reversible defects was quantified: MIBI-stress/MIBI-rest 35 +/- 16% MIBI-stress/TI-rest single 50 +/- 26% and MIBI-stress/TI-rest dual 48 +/- 22%. The results of 99mTc-MIBI rest and 201TI rest studies in patients with chronic CAD are not the same. Dual-isotope 1-day 201TI-rest/99mTc-MIBI-stress SPET data, acquired separately, may give fast and complete information on myocardial perfusion at stress and rest, respectively, and on myocardial viability.

Female↗
PubMed1990

[Urokinetography in the diagnosis and follow-up of obstructive uropathy in children].

With regard to different paediatric urological diseases nuclear-medical urokinetography using the tracer 99m-Tc-DTPA can identify typical functional patterns. By means of 261 investigations on 240 children, retroperistaltic waves, initial pyeloureteral and the final ureterovesical conus, dysperistaltic waves and interrupting empty strips with lacing, constrictive peristalsis can be shown in comparison with the normal anterograde "stair" pattern. Moreover, UKG as a functional method makes it possible to control the therapeutic success of antibiotics in urinary inflammations, the situation after stone discharges and application of vegetative systemic drugs. In our opinion the operative procedure and the prognosis of megaureters can be assessed. Consequently urokinetography is among the important preoperative investigations in paediatric urology and in the follow-up programme after reconstructive urological operations. Nuclear-medical isotope investigation is without significant risk and yields many diagnostic details. The method can be recommended for functional urological diagnosis in children or teenagers with high frequency of follow-up investigations or in patients with contrast medium allergy. Finally, ureter physiology can be checked in patients subjected to bone scintigraphy. Clinical research is possible via UKG without additional radiation exposure.

Child↗
PubMed1984

[Application of ROC analysis to evaluating different methods of skeletal scintigraphy. Description of a practicable method].

Various techniques producing similar information can be compared by the use of ROC analysis. A practical and quick method of ROC analysis, which is otherwise very time-consuming, has been described for comparing various types of skeletal scintigraphy. Data is obtained by means of a phantom and evaluated with the help of a scheme which requires only moderate computational facilities.

Bone and Bones↗
PubMed1984

[Exposure technics for computed scintigrams].

The technique of making copies on radiographic films or on multiformat cameras from computer scintigrams, computer tomograms, digital radiographs or other similar digital images should be carefully studied in order to make the best use of the characteristics of the film. Contrast transfer was studied using a nuclear medicine camera computer system with registration on radiographic film. Possible difficulties in obtaining copies and a simple software arrangement are described, which would influence contrast transmission.

Absorptiometry, Photon↗
PubMed1982

[Questions of accuracy when using "not therapy-specific" computer systems for irradiation planning (author's transl)].

The conditions were examined under which little and medium computer systems not having been primarily developed for radiotherapy can be used in order to make sufficiently precise calculations of dose distributions. The adapted accuracy of the principal factors influencing the dose distribution renders possible a time-saving calculation of several dose distributions and a final calculation. By comparison with a reference calculation made as accurately as possible, the isodose curve shows only little deviations. The following factors were examined in order to find out an eventual influence exerted upon an isodose displacement: number of scan points in the cross-section, correction of the oblique ray incidence, inhomogeneities, dissociations of the rotation field. To our opinion, the isodose displacements found for a dose calculation with adapted accuracy are acceptable when related to influencing factors depending on the individual patients.

Computers↗
PubMed1980

[Quality assurance of brachytherapy by means of interactive computer-assisted planning of the dose distribution using visual optimization (author's transl)].

Not earlier than with present generation of afterloading apparatuses,--efficient, reliable and appropriate for many purposes,--it was possible in brachytherapy to give up the previous impractical application techniques. Brachytherapy thus has found the widespread use it merits because of its good results. Additional utilization of a computer for the planning of dose distributions will guarantee the quality possible now in brachytherapy. To that end, a method of computer-assisted planning is described. It can be used for different application techniques. Further improvement of the results obtained till now is discussed in detail.

Brachytherapy↗