Computerized cranial tomography in the evaluation of pituitary tumours in rats

The use of the rat as an animal model in studies of pituitary tumours has been hampered by the great individual variation and the necessity of killing the animal to assess the development and progression of tumour growth. A study was designed to determine whether computed tomography (CT) could be used to monitor the growth of pituitary tumours in female Sprague-Dawley rats. Animals were injected with oestradiol valerate 2 mg/3 weeks sc, an amount known to lead to development of pituitary tumours (from 45 to 378 mg pituitary weight). Control rats were treated with vehicle alone. Anaesthetized rats injected with contrast were studied by computerized axial tomography and the single CT scans (coronal cuts) were correlated with direct anatomical measurements obtained after pituitary dissection. All pituitaries weighing more than 54 mg were detected by the CT scanner. A good correlation between measurements made after anatomical dissection was found in the two main axes of the coronal cuts. In conclusion, CT scanning can be used for assessment of pituitary tumour size in the rat. This technique should be especially helpful in studies where individual evaluation and/or repeated measurements over time are necessary.