Chest roentgenographic techniques for demonstrating human lung tumour xenografts in nude rats

Roentgenographic techniques were investigated for imaging orthotopic lung tumours in anaesthetized nude rats endobronchially implanted with human lung cancer cells. A conventional radiographic unit with a dual-screen, double-emulsion film mammographic receptor produced images preferable to those from a mammographic unit because of superior resolution. Typical exposure factors were 300 mA, 29 kVp, and 17 ms at a focus-film distance of 76 cm with a 2.11 by 2.41 mm effective focal spot and inherent filtration of 1.2 mm aluminium. Sensitivity for tumour detection was 0.93 for 59 animals with pathologically proved tumours and 0.96 for 54 animals with tumours larger than 4 mm or 50 mg. For 24 pathologically tumour-free animals, specificity was 1.00. For 55 animals radiographically judged to have tumours, positive predictive value was 1.00. For all 83 animals, accuracy was 0.95. This technique effectively demonstrates orthotopic human lung tumours in nude rats and should be useful for noninvasive monitoring of tumour presence, location, size, and changes in size.