Thyroidal radioisotope uptake in euthyroid cats: a comparison between 131I and 99mTcO4.

Two thyroidal evaluation systems in euthyroid cats (n = 12) were compared. A single, confirmed hyperthyroid cat was included for interest. Firstly, thyroidal uptake of an intravenous bolus of approximately 111 MBq (3 mCi) 99MTcO4 was estimated by using a scintillation camera and calculating the ratio of thyroid to salivary activities at 20 min and 4 h. Thyroid to salivary activity ratios were 1:1 at 20 min and 2:1 at 4 h. Two discrete areas of salivary uptake were identified, namely a parotid/mandibular complex and a more rostral buccal/sublingual complex. These results were compared to radioiodine uptake of an oral dose of approximately 0.925 MBq (25 microCi) 131I using a standard thyroid uptake system, measured at 1, 2, 4, 6, 8, 10, 12, 24 and 48 h after administration. Mean radioiodine thyroidal uptake started at 33% at 1 h, stabilised at 21% between 4 and 24 h, and dropped to 18% at 48 h. There was a significant correlation between the early thyroid:salivary ratio of the parotid/mandibular complex and the radioiodine uptake at 12 h.

Use of indium-111-labelled platelets in black stroke patients. A pilot study.

Human blood platelets labelled with indium-111 oxine have been shown to accumulate on damaged vascular surfaces and abnormal platelet deposition has been demonstrated in the carotid arteries of white stroke patients. Gamma scintigraphy of the carotid and cerebral arteries of 5 black stroke patients and 5 age- and sex-matched controls using 111In-labelled platelets showed no abnormal accumulation indicative of carotid artery disease.

The cardiovascular status of the black stroke patient.

The cardiac status of 102 consecutive black stroke patients entered to the Medunsa Stroke Databank was determined. Cardiological examination, echocardiography and a gated blood pool scan revealed structural and/or functional cardiac abnormalities in 73.6% of patients. Rheumatic heart disease was diagnosed in 15.6%, mitral valve prolapse in 5.8% and mitral annulus calcification in 4.9% of cases. 'Possible' cardiac sources of cerebral embolism were detected in 22.5% and 'definite' sources in 23.5% of patients. Hypertensive heart disease was diagnosed in 35.2% and cardiomyopathy in 13.7% of the study population. Ischaemic heart disease was present in 6.86%. Ultrasonography revealed ventricular bands in 29.4% of patients. The high incidence of structural cardiac abnormalities detected by non-invasive means is in keeping with recent studies in white stroke patients.

Evaluation of different formulae for the study of platelet survival.

The International Committee of Standardization in Haematology has recommended in 1977 three methods for calculating the mean platelet survival time of isotope labelled platelets, although in recent years other mathematical equations were also suggested for the determination of platelet survival times. Seven different methods of calculating the mean survival time for normals were investigated and were compared with one another.

A comparison of 111In-labelled polymer beads and 99mTc-Sn-colloid as solid food and semi-solid food tracers for scintigraphic gastric emptying studies.

In order to establish the efficacy of labelling a solid meal and a semi-solid meal with either 111In-labelled polymer beads or 99mTc-tin colloid beagle dogs were fed variously labelled meals of different consistencies and then monitored by scintigraphy for gastric motility patterns. The labelling with each tracer was either performed by thoroughly mixing it into the food before cooking, or alternatively by surface labelling after the food had been cooked. For the 99mTc-Sn-colloid tracer no difference was found in the measured gastric emptying times resulting from either pre-cooking labelling or surface labelling of the meals. Cooking the tracer together with the ingredients does however seem to promote a firm entrapment of the 111In-polymer beads into a solid protein, and in this manner the 111In-labelled resin appears to be a reliable solid food tracer. Surface labelling with 111In-polymer beads of a solid meal with a smooth texture fails totally and the tracer empties with the liquid phase.

Gastrointestinal scintigraphy using 99mTc- or 111In-labelled polymer beads.

In order to establish normal and pathological stomach emptying characteristics by external measurement of a radioactive meal using a gamma camera and computer system, it is necessary for the radioactively labelled substance to have the same behaviour in the stomach as the ingested food. Resins containing chelating groups which enable binding to either reduced 99mTcO4- or 111In+3 were tested for their suitability as tracers mixed into solid food. The preparation of such styrene-divinyl-benzene resins containing either triethylenetetramine substituents or the fully carboxymethylated derivatives is discussed, as well as the procedures of labelling with either 99mTc-pertechnetate or 111In-chloride. An evaluation of the resins for gastrointestinal scintigraphy was performed on 3 chacma baboons and a male human volunteer with encouraging results.