Effects of breath holding CT scan during mid-expiration on PET/CT

Objective: To study the effects of breath holding during mid-expiration of CT scan on PET/CT and SUV of lung. Methods: From September 2010 to December 2010, 200 patients including 120 males and 80 females (23-87 (55.01± 11.60) years), who underwent ¹⁸F-FDG PET/CT studies were included. Patients were randomly divided into 2 groups using random number table. In breath holding (BH) group (52 males, 48 females, age ranging from 29-83 (55.43±10.38) years), all underwent PET/CT studies with BH CT during mid-expiration.In free breath (FB) group (68 males, 32 females, age ranging from 23-87 (55.68± 12.72) years), all underwent PET/CT studies with FB CT. PET/CT images were analyzed by 1 senior technologist and 2 nuclear physicians. Analysis was carried out for the special registration of PET and CT, SUV of lung tissue on the bottom of lung and respiratory motion artifacts of lung on CT scanning. The diaphragmatic dome showed on the same layer of PET and CT was considered as well-registration between CT and PET. Two-sample t test, χ² test and one-way analysis of variance were used to analyze data. Results: In BH group, 28% (28/100) of expiratory motion artifacts was observed, which was significantly lower than that of FB group (96%, 96/100; χ²=98.132, P<0.01). In BH group, 40% (80/200) was considered well-registration between CT and PET, which was significantly higher than that of FB group (30%, 60/200; χ²=4.396, P<0.05). There were 3 types of registration between CT and PET: location of diaphragm on CT higher than that on PET, matching between PET and CT, location of diaphragm on PET higher than that on CT. SUV in low lung tissue of these different types were increased one by one, with more significant difference found in BH group (SUV_max: 0.73±0.28, 1.00±0.29, 1.60±0.68; SUV_mean: 0.59±0.23, 0.81±0.22, 1.33±0.34; F=21.93, 24.57, both P<0.01) than those in FB group (SUV_max: 0.84±0.36, 1.08±0.27, 1.16±0.24; SUV_mean: 0.69±0.29, 0.85±0.20, 0.94±0.24; F=7.23, 6.29, both P<0.01). Conclusion: Artifacts of respiratory motion on CT could be reduced significantly by BH CT scanning during mid-expiration, while the rate of well-registration between PET and CT is increased. (authors)