The Application Of Gemstone Spectrum CT In Diagnosis Of SPN

ObjectiveTo evaluate the diagnosis of gemstone spectral imaging (GSI) of solitary pulmonary nodules with Discovery CT750HD.Methods1. A pulmonary nodule phantom imaging with Discovery CT750HD:The spherical pulmonary nodules made with three different kinds of materials (Polypropylene, Monomer casting nylon and ACRYLIC). Each material was applied to represent different density (-100HU,60HU and100HU). The diameters of nodes were20.0mm,10.0mm,5.0mm. All the nodules were set in a plastic lung phantom (-900HU). Phantom was fixed in a container filled with fluid, muscle and bone to simulate thorax. The phantom scan was performed under both single energy (SE) and mixed energy (ME) CT techniques. Scans were performed with Discovery CT750HD scanner using GSI (Gemstone Spectral Imaging) technique (GSIKV,630mA,64×0.625mm slices,0.516:1pitch,50cm scan field of view,38cm display field of view) with there different ratation time (0.5s,0.8s,1.0s). In addition, images were generated using the high resolution120kVp technique (convert mA according to GSI imaging CTDI, other parameters were the same with SECT). Scans were performed with and without the added bone.1.1Quantitative CT numbers and SD numbers measurement of nodules (diameters of nodes were20.0mm) at different scan conditions were done by three experienced radiologists on the workstation. CT numbers SNR of each nodule under different SECT and MECT were compared.1.2Using the spectral analysis software to acquire the best contrast-to-noise ratio (CNR) curves of all nodules. The homologous keV of of the best CNR measurement of nodules were done by three experienced radiologists on the workstation, repeated three times and took the averages. Comparing the CT numbers of the homologous keV of best CNR with the CT numbers of73keV, the diameter of nodes was20.0mm.1.3Using the spectral analysis software to acquire the spectrum curves of all nodules. The curves slope could evaluate the difference of spectrum curves. Analysising the Linear correlation between the curves slope and nodules density, nodules diameter, ratation time and added bone.2. Pulmonary nodule patients imaging with Discovery CT750HD:GSI of42pulmonary nodule patients (squamous carcinoma17, adenocarcinoma15, pneumonia10) confirmed by pathology or foliowup data. Scans were performed with Discovery CT750HD (GSIKV,630mA,64×0.625mm slices,0.516:1pitch,50cm scan field of view,38cm display field of view,0.8s ratation time). Analysising the differences of spectrum curves between different pulmonary nodules pathology.Results1. A pulmonary nodule phantom imaging with Discovery CT750HD:(1) The phantom scanned under SE in Nacl+Model or Nacl+Model+Bone with Discovery CT750HD:All the CT numbers didn’t show significant difference (P>0.05). In conditions of (0.8s, ratation time) and (1.0s, ratation time;60HU, density), the SNR didn’t show significant difference (P>0.05), the other conditions the SNR showed significant difference (P<0.05).(2) The phantom scanned under ME in Nacl+Model or Nacl+Model+Bone with Discovery CT750HD:All the CT numbers showed significant difference (P <0.05). All the SNR also showed significant difference (P<0.05).1.2(1) The CNR of pulmonary nodules met normal distribution. The confidence interval was (64.75-65.27).65keV image of pulmonary nodule and lung had the best CNR.(2) The CT numbers of65keV,73keV and standard CT numbers of nodules (diameters of nodes were20.0mm) show significant difference (P<0.05). The CT numbers of65keV and73keV also show significant difference (P<0.05). The CT numbers of-100HU,60HU,100HU were-133.95±0.60,23.47±1.04,89.33±1.38under73keV, and were-119.51±2.43,40.39±1.43,102.63±1.88under65keV. The CT numbers of73keV were more accurate.1.3Taking the nodules density, nodules diameter, ratation time, added bone as independent variable and taking the spectrum curves slope as dependent variable to acquire multiple regression linear model."The spectrum curves slope" was positively related with "nodules density","nodules diameter". And "nodules density" had more strong linear correlation than "nodules diameter".2. Pulmonary nodule patients imaging with Discovery CT750HD:Analysis of variance showed:F=167.727, P=0.000<0.005. Comparing any two kinds of pulmonary nodules pathology (squamous carcinoma, adenocarcinoma, pneumonia) showed P<0.005. So the spectrum curves slope had a marked difference between different pulmonary nodules pathology.ConclusionThe Discovery CT750HD results indicated that SECT can alleviate beam hardening effect, acquire more accurate CT numbers than MECT, and get the best CNR at65keV. The CT numbers of73keV had some differences with standard CT numbers, but were more accurate than65keV. The spectrum curves slope of pulmonary nodules was positively related with nodules density, nodules diameter, nodules density was more obviously. The spectrum curves slope of pulmonary nodules also had differences between different pulmonary nodules pathology.