Effect of Slice Thickness Reconstruction on Quantitative Vascular Parameters in Perfusion CT

Objective: The purpose of this study was to determine how the slice thickness reconstruction influences quantitative perfusion CT parameters. Materials and Methods: Eighteen patients with cancer (15 non-small-cell lung cancer, 2 rectal cancer and 1 renal cancer) were examined prospectively with multidetector row CT. A 90-second perfusion study was performed after intravenous bolus injection of contrast material. Blood flow, blood volume, mean transit time and permeability-surface area product were determined at three different slice thickness reconstruction (1.25, 2.5 and 5 mms) both in tumors and in paraspinal muscle. Mean values, limits of agreement between measurements and within-subject coefficient of correlation were obtained for these thicknesses. Results: Mean ± standard deviation BF, BV, MTT and PS in lesions were 118.7 ± 117.9 mL/min/100g tissue, 8.2 ± 8.2 mL/100g tissue, 7.5 ± 5.4 seconds and 10.3 ± 7.2 mL/min/100g tissue respectively at1.25 mmslice thickness; 116.1 ± 115.7 mL/min/100g tissue, 7.8 ± 8.7 mL/100g tissue, 7 ± 4.5 seconds and 10.4 ± 7.5 mL/min/100g tissue at 2.5 mms; and 119.6 ± 115.7 mL/min/100g tissue, 7.8 ± 8.8 mL/100g tissue, 5.4 ± 3.4 seconds and 9.6 ± 7.5 mL/min/100g tissue at 5 mms. Differences between means for different slice thickness where relatively small in all parameters (<15%) except in MTT where difference was up to 37%. 95% limits of agreement were worse when comparing more different slice thicknesses (e.g. 1.25 vs 5 mms) than when comparing more close slice thicknesses (1.25 vs 2.5 mms or 2.5 vs 5 mms). Conclusions: There is a significant variability in perfusion parameter measurements at different slice thickness reconstruction, particularly in MTT. The more close together the slice thicknesses were, the smaller was the variability.