The isolated porcine forelimb serves as a versatile tool for the assessment of the biological performance of needle-free injection devices such as INJEX. Further studies are necessary to correlate the model for drug delivery in humans.

After receiving between 100 and 300 mu Ci of the positron-emitting radioisotope 124I (half-life, 4.2 days), 64 patients with a variety of thyroid disorders were imaged with a high resolution positron camera. A 3-dimensional image of the distribution of radioiodine uptake within the thyroid was obtained from a single 10- to 15-min scan. This image may be viewed as a sequence of 2-mm thick transverse, sagittal, or frontal sections or as a 3-dimensional shaded surface. The functional volume of the thyroid may be estimated by counting the volume elements (voxels) inside the thyroid surface. The precision of the estimate varied from 6-15%, depending on the size and clinical status of the thyroid. The volume estimation procedure was validated with phantoms and with the thyroids of patients who subsequently underwent partial thyroidectomy. This 3-dimensional imaging technique may be useful for diagnosis and management of thyroid diseases.

A high-density avalanche chamber (HIDAC) positron camera was used for tomographic imaging of the human thyroid in vivo. Images were made 7 and 24 h after the oral administration of the positron-emitting radionuclide, sodium iodide 124I (with activities varying between 0.3 and 1 mCi), to patients scheduled for either partial thyroidectomy or radioiodine treatment. The results of thyroid imaging performed on 38 patients and their clinical relevance are discussed; as an illustration, three typical cases are presented. In Graves' disease, it was found that, whereas standard 131I and 124I scintigrams showed a diffuse goitre, positron images indicated a marked heterogeneity of the activity distribution, with "cold" areas in 8 out of the 11 cases studied. In conventional scintigrams, multinodular goitre showed a non-uniform radioiodine distribution, while positron images revealed considerable regional differences of activity uptake, with hot and cold areas in all of the 13 cases studied. As a consequence of the high spatial resolution of the camera [2.5 mm full width at half maximum (FWHM)], the functional volume of the thyroid may be estimated from 2 mm-thick transverse tomographic sections to within about 13%. This estimate may be compared with the measured volume after partial thyroidectomy, and in a follow-up scan, a further estimate can be made of the residual thyroid tissue remaining within the patient's body. In the case of radioiodine treatment in Graves' disease and multinodular goitre, the appropriate therapeutic dose of 131I can calculated according to the functional volume of the thyroid estimated from 124I tomographic images.