Quantitative assessment of lung cancer tumor vascular parameters by using high speed perfusion CT: influence of tumor region of interest

Abstract

Objective To prospectively determine whether position and size of tumor region of interest (ROI) influence estimates of lung cancer vascular parameters at 256-slice CT perfusion study.Methods After institutional review board approval and informed consent,16 men and 11 women with lung cancer underwent 70-second CT perfusion study. Perfusion, blood volume, peak enhancement weredetermined for 60 or 120 mm2 circular ROIs placed at the tumor edge and center and around (outlining) visible tumor. ROI analysis was repeated twice by two observers in the same way to get the average values.The correlation between the measurements and microvascular density counts was determined in 19 patients with operation.Measurements were compared by using Pair-Samples t test,a difference with P≤0.05 was significant.Results Perfusion,blood volume,peak enhancement measurements were substantially higher at the edge than at the center for both 60 and 120 mm2 ROI. For 60 and 120 mm2 ROI,median of the three measurements were (M=15.40,9.50 ml · min- 1 · 100 ml - 1,M =35.60,25.40 ml · 100 g-1,and M=16.47,10.20 HU),respectively,at the edge versus(M =14.80,8.52 ml · min- 1 · 100 ml- 1,M =33.50,23.90 ml · 100 g- 1,and M =15.64,9.40 HU),respectively,at the center(t value was 10.95,9.80,7.06,2.93,7.74 and 10.09,respectively,all P ＜ 0.05 ). Measurements varied substantially depending on the ROI size,values for the ROI for outlined tumor were intermediate between those at the tumor edge and center.Perfusion(M=12.51 ml.min- 1 · 100 ml-1),blood volume(M=29.31 ml.100 g-1),peakenhancement (M =12.93 HU) for the ROI outlining tumor were intermediate between those at the tumor edge and center.There was a good correlation between perfusion,blood volume,peak enhancement for the ROI outlining tumor and microvascular density[ ( 19.43 ± 8.78 ) vessels/0.74 mm2 ],respectively ( r value 0.732,0.590 and 0.544,all P ＜ 0.05 ).Conclusions Position and size of tumor ROI substantially influence ultimate perfusion values.ROI for outlined entire tumor is more reliable for perfusion measurements and more appropriate clinically than use of arbitrarily determined smaller ROI. Key words: Lung neoplasms; Tomography,X-ray computed; Perfusion