Quantitative Analysis Of Lung Volume Using MSCT: Comparison With Pulmonary Function Test

Purpose To study the quantitative analysis of lung volume using multi-slice spiral CT (MSCT) and the the correlation of indices between CT lung volume and pulmonary function test (PFT), as well as the effect of dose,thickness,image reconstruction algorithms,upper threshold for measurements and the CT features of emphysema, so as to evaluate the usefulness of MSCT with three-dimensional (3D) postprocessing for quantitative analysis of lung volume. Materials and methods 1. Eighty-five cases were divided into three groups, 20 were group A, 6 were group B, 59 were group C, there are no diseases which affecting the pulmonary function. 2. The whole lung in group A was scanned with conventional dose at breathholding state of eupnea, with 10mm thickness,10mm interval and 1.25mm thickness,1.25mm interval,standard and bone algorithms reconstruction; The part lung in group B was respectively scanned with conventional and low dose at the same breathholding state of eupnea, with 1.25mm thickness ,1.25mm interval ,standard and bone algorithms reconstruction; In group C, CT scan and PFT were performed within 3 day in all case. the whole lung was respectively scanned with low dose at the end of full inspiration and full expiration, with 1.25mm thickness,1.25mm interval,standard algorithms reconstruction. 3. The 3D models of the lung were reconstructed with AW4.2 workstation, threshold limits segmentation and shaded surface display (SSD) were used, The total lung volume(V) and mean lung density(MLD) in group A,the part lung volume(VP) and MLD with the upper thresholds of –200Hu and –300Hu were calculated by integrated pulmonary quantitative software, as well as the relative indices of CT lung volume and lung density in group C. Results 1. In group A, there was highly significant difference of V and MLD between 10mm and 1.25mm thickness(P<0.01), the V and MLD of 1.25mm thickness were smaller than 10mm thickness. 2. In group B, the VP of low dose was smaller than conventional dose, there was significant difference at standard algorithms reconstruction(P<0.05) and highly significant difference at bone algorithms reconstruction(P<0.01), but there was no significant difference between MLD of low dose and conventional dose(P>0.05). 3. In group B, the VP of standard algorithms reconstruction was smaller than bone reconstruction, there was significant difference at conventional dose,–200Hu and –300Hu upper thresholds (P<0.05), as well as low dose,–300Hu upper threshold (P<0.05), and highly significant difference at low dose,–200Hu upper threshold (P<0.01), the MLD of standard algorithms reconstruction was highly significant difference frome bone reconstruction (P<0.01). 4.In 59 cases of group C, there were 32 healthy controls and 27 patients with emphysema diagnosed by CT morphology, but 39 healthy controls and 20 patients with emphysema diagnosed by PFT. Comparing the indices of non-emphysema and emphysema groups, TLC showed significant difference (P<0.05), the others indices of PFT showed highly significant difference (P<0.01). 5. In group C, except Vin-Vex, the relative indices of CT lung volume and lung density showed highly significant difference between –200Hu and –300Hu upper thresholds. 6. Between non-emphysema and emphysema cases diagnosed by CT morphology, VIBin and VIDin showed no significant difference (P>0.05), VICin and MLDin showed significant difference (P<0.05), the others indices of CT lung volume and lung density showed highly significant difference (P<0.01), the VIAex of emphysema was 5.7 times of non-emphysema. 7. In group C, there were different correlation between indices of PFT and indices of CT lung volume and density. The full inspiration volume(Vin) was highest correlated with total lung capacity(TLC)(r=0.870), and the full expiration volume(Vex) with residual volume(RV)(non-emphysema r=0.746,emphysema r=0.870)also, the Vin-Vex was highcorrelated with forced vital capacity(FVC), as well as Vex/Vin with RV/TLC,VIAin with TLC,VIAex with RV,VIBex with RV. The negative correlation existed between MLDin and TLC,MLDex and RV,MLDex-MLDin and RV/TLC. Conclusion 1. MSCT with 3D postprocessing such as threshold limits segmentation and shaded surface display (SSD) is suitable to quantitative analysis of lung volume and density. 2. Thinner thickness improves the accuracy of data. 3. The dose of 60mAs meets the requirements of radiation dose decrease and image auto-segmentation. 4. Reconstruction of standard algorithms and –300Hu upper threshold meet the requirements of image auto-segmentation and max information remaining. 5. The indices of CT lung volume are well correlated with PFT, better than indices of CT lung density. 6. The indices of CT lung volume and density show significant differences between emphysema and non-emphysema cases, the VIAex is a sensitive index for emphysema. 7. Quantitative analysis of lung volume using MSCT with 3D postprocessing is useful for assessing the pulmonary function.