The bacterial endotoxin test in the PET facility.

A method by which the gel-clot Limulus amebocyte lysate test may be performed in 20 rather than 60 min with sufficient sensitivity to satisfy the needs of the nuclear medicine or positron emission tomography laboratories has been developed and validated for use as a substitute for the Bacterial Endotoxin Test described in the United States Pharmacopeia, 22nd revision. Using this method, results may be obtained from the test prior to the human administration of radiopharmaceuticals without extensive loss of activity and with increased safety when compared to tests performed after administration. Additionally, studies on the shelf-lives of the reagents used in the test were conducted. When refrigerated between use, control standard endotoxin dilutions of 5 EU/ml or greater may be used for at least 1 mo after preparation and reconstituted lysate retains its labeled sensitivity for at least 10 days, considerably longer than the manufacturer's stated shelf-lives.

The value of urine creatinine analysis in the evaluation on Schilling tests.

We performed a prospective study to assess the clinical value of evaluating the adequacy of 24-hour urine specimens submitted for Schilling tests. A total of 121 specimens were evaluated of which 51 had abnormal vitamin B12 excretion values. Of those 51, there were 23 with apparently inadequate total creatinine content (implying a collection of less than 24 hours). Six of 12 specimens with less than 600 ml had adequate total creatinine content as well as normal vitamin B12 excretion. Compared with evaluation of specimen volume alone, these data support the inexpensive urine creatinine assay as a valuable source of information regarding the adequacy of 24-hour urine collections thereby improving the specificity of the Schilling test.

Absent platelet aggregation with normal fibrinogen binding in basset hound hereditary thrombopathy.

Platelets from dogs with Basset Hound Hereditary Thrombopathy (BHT) initially displayed a thrombasthenia-like aggregation defect but have been shown to have normal amounts of platelet membrane glycoproteins IIb and IIIa (GPIIb-IIIa), and therefore are more accurately described as thrombopathic. The presence of normal quantities of GPIIb-IIIa, however, did not rule out the possibility of a functionally abnormal glycoprotein complex which would be unable to bind radio-labeled fibrinogen. Therefore, fibrinogen binding in BHT platelets was evaluated. Platelets from BHT and normal dogs were activated with 1 x 10(-5) M ADP in the presence of 125I-fibrinogen and the surface-bound radioactivity was quantitated. The amount of fibrinogen bound by BHT dog platelets was not significantly different than that bound by normal dog platelets. Platelets from dogs with BHT bound 30,282 +/- 3,133 and normal dog platelets bound 31,664 +/- 2,772 molecules of fibrinogen per platelet. The quantitatively normal GPIIb-IIIa complex binds fibrinogen in normal amounts and does not seem to represent the abnormality responsible for the aggregation defect in BHT platelets. Therefore, other factors central to normal platelet function and related to platelet aggregation must be considered.

Prevention of motion artifacts on dual isotope subtraction parathyroid scintigraphy.

A simple, effective technique is described to identify and eliminate motion artifacts which might potentially invalidate dual isotope subtraction parathyroid scintigraphy. Cobalt-57 markers, appropriately placed on the patient, allow detection of movement and permit realignment if movement occurs between imaging sequences. This technique should assure the accuracy of dual isotope parathyroid subtraction scintigraphy.

Radioiodine therapy of hyperthyroidism precludes thallium-201 myocardial scintigraphy.

The authors attempted to perform Tl-201 myocardial perfusion scintigraphy in a 42-year-old man 23 and 35 days after he received 9.8 mCi of oral I-131 for documented Graves' disease. Interference from primary and scattered photons from residual thyroid I-131 made Tl-201 myocardial scintigraphy technically impossible. A series of phantom and patient studies using I-131 and Tl-201 were performed, yielding guidelines for planning Tl-201 myocardial scintigraphy following radioiodine therapy.

Severe systemic reaction to diphosphonate bone imaging agents: skin testing to predict allergic response and a safe alternative agent.

We describe a severe systemic reaction which occurred in a patient on two occasions after i.v. injection of chemically related diphosphonate bone imaging agents. Skin testing showed reactivity to multiple commercially available diphosphonate compounds but no significant response to pyrophosphates. A subsequent pyrophosphate bone scan resulted in no adverse reaction. Severe systemic reactions to diphosphonates can occur, skin testing may prove useful in evaluating allergic reactions, and pyrophosphates appear to be a safe alternative agent in patients proven or suspected allergic to diphosphonates.

Thyroid uptake and imaging with iodine-123 at 4-5 hours: replacement of the 24-hour iodine-131 standard.

A study was carried out to determine the suitability of utilizing a 4 to 5 hr interval from administration of iodine-123 to imaging and uptake measurement as a replacement for the 24-hr standard originally established with iodine-131. In 55 patients who underwent scintigraphy at 4 and 24 hr, there was no discrepancy between paired images. In 55 patients who had uptake measured at 4 and 24 hr and in 191 patients who had uptake measured at 5 and 24 hr, the early measurements proved equal or better discriminants of euthyroid from hyperthyroid patients. In our institutions, these findings and the logistical advantages of completing the exam in 4-5 hr led us to abandon the 24-hr study in the majority of patients.