NON-SKELETAL DISTRIBUTION OF BONE-SEEKING RADIOPHARMACEUTICALS

A variety of factors may change the normal distribution of bone-seeking radiopharmaceuticals. This paper presents a classification of non-skeletal bone tracer distribution according to physiologic, pathologic, and artifactual causes. The mechanisms thought to account for non-skeletal distribution are reviewed. Examples of non-skeletal bone tracer distribution include calcinosis cutis and pulmonary mineralization in hyperadrenocorticism, renal infarct, acute rhabdomyolysis, urine contamination, lymph node uptake following extravasation of the radiopharmaceutical, thyroid uptake due to free pertechnetate in the injectate, and intramuscular uptake following injection of butorphanol.     

DISTINGUISHING RHINITIS AND NASAL NEOPLASIA BY RADIOGRAPHY

To compare the incidence of radiographic signs in dogs with rhinitis and primary nasal neoplasia and to assess the performance of observers for distinguishing these conditions, the nasal radiographs of 72 dogs with either rhinitis (n = 42) or primary nasal neoplasia (n = 30) were examined by two independent observers using custom-designed forms to record their interpretations. Rhinitis was associated with a higher incidence of focal or multifocal lesions, localised soft tissue opacities, lucent foci, and a lack of frontal sinus involvement. Neoplasia was associated with soft tissue opacities and loss of turbinate detail that affected the entire ipsilateral nasal cavity, signs of invasion of the bones surrounding the nasal cavity, and soft tissue/fluid opacities within the ipsilateral frontal sinus. The signs with the highest positive predictive value (PPV) for rhinitis were absence of frontal sinus lesions and lucent foci in nasal cavity (PPV of each 82%), and invasion of surrounding bones for neoplasia (PPV 88%). There were no significant differences in the position of the lesion within the nasal cavity, incidence of unilateral versus bilateral lesions, calcified lesions, or absence of teeth. There was moderate agreement between observers about the diagnosis (kappa 0.59). Areas (SE) under ROC curves were 0.94 (0.03) and 0.96 (0.03) for observers A and B, respectively (not significantly different; P = 0.68). These results indicate a high accuracy for radiologists examining dogs with nasal diseases. Differentiation of rhinitis and nasal neoplasia should be based on finding combinations of radiologic signs that together have a high PPV. Differences in interpretation between experienced observers in this study suggest that certain signs are potential sources of error.