A method for registration between CT and single photon emission computed tomography lung perfusion images

Abstract

Objective To compare the registration errors of single photon emission computed tomography (SPECT) and CT images using a visual method and the methods of different numbers and combinations of the external markers,and to explore an accurate,reproducible and simple registration method of CT-SPECT lung perfusion images. Methods Two patients with lung cancer underwent thoracic CT scans and SPECT lung perfusion scans. The 9 external markers were fixed on the thoracic region before CT scans and SPECT lung per-fusion scans. Two series of images were registered using a visual method and the methods of different numbers and combinations of the external markers respectively based on Pinnacle~3 planning treatment system. After regis-tration , space coordinates of the 9 external markers were recorded respectively. The accuracy of registration was assessed using the absolute differences value of the 9 external markers coordinates between two series of images after registration. Results After registration using 9 external markers, the error in the left-right direction was the greatest, (1. 92 ±1.56 ) mm. Compared with that of using 9 external markers, there were statistical differ-ences using the visual method,2 external markers,3 external markers,4 external markers ( P < 0. 05 ), and there was no statistical difference using 5 external makers,6 external markers,7 external markers,8 external markers (P =0.081,0.061,0. 854,0. 860, respectively). Comparing the registration methods based on the middle thoracic external markers with the registration methods based on the pectus external markers using 4 ex-temal markers,5 external markers,6 external markers,there was no statistical difference between two methods and between the former and 9 external markers ( P =0.395,0. 110, respectively), and there was statistical difference between the latter and 9 external markers ( P = 0. 010). There was no statistical difference in the three registrations using 5 external markers ( P =0. 613,0. 26,0. 531 ,respectively). Conclusion The method of 5 external markers distributing non-coplanar is an accurate, reproducible and simple registration method of CT-SPECT lung perfusion images. Choosing the middle thoracic external markers less influenced by respiratory movement is a better method. Key words: Carcinoma, non- small- cell lung; Radiotherapy; Tomography, emission-computed, single-photon; Medical image registration