| Background Becaused of lung nodules displacement of the respiratory, SUV and volumemeasurement is not accurate, clinical diagnosis, staging, and outline of radiotherapy target areabecome the clinical research focus.OBJECTIVE Patients with lung nodules by the respiratory gated PET/CT acquisition,compared of the non gated PET/CT, summed up the conditions and methods for respiratorygated acquisition, the affect of SUV and volume measuerment by respiratory gated techniquewas discussed initially; the position movements caused by respiratory motion were measured;correlation analysis of SUV, size and displacement for lung nodules was gived between differentphase of the respiratory gated and non gated technology for lung nodules; the Signal to Noisedifference of RG PET/CT and conventional acquisition was observed, in order to providevaluable clinical information.METHODS May 2010 to March 2011,patients in our department for PET/CT imaging werefound to have multiple pulmonary nodules, and a total of 19 cases in patients agreed to acceptthe respiratory gated imaging, of which 14 patients did the completion of imaging, 6 males and 8females, aged 29 to 80 years, mean age 63.7±7.1 years. The type of PET/CT is the GEDiscovery VCT. 18F FDG dose injected is computed by 5.55 ~ 7.40 MBq / kg, patients shouldbe supine rest for 60 minutes after injection, then make bladder empty before imaging, 3D modefor PET scanning is used, about 6 7 beds, 2 minutes per bed, with CT attenuation correction forreconstruction and fusion of PET images. In respiratory gating acquisition,the breathing ofpatients should be stable, breathing curve is recorded by real time monitoring system withVarian company, and the signals of respiration rhythm are sent to PET/CT acquisition standardcontrol system. The respiratory rhythm respiratory control system is started to record signalsfirstly, which acquired by the RG PET/CT. The 4D CT scan is used, 6 minutes for one beddivided into six bins is to PET scan. SUV, volume and displacement are obtained by the AWsystem of semi automatic analysis, each indicator of each lung nodules has to be non gated andgated imaging with a total of seven measurements of 6 phases. SNR is calculated by the formula.Radiotherapy target areas are outlined for some patients. RESULTS①In this study, RG PET/CT examination is done by 14 patients with 37 lungnodules, it is found that respiratory gated imaging can improve the focus of the SUV value,SUVmax and SUVmean is up to 13.69±6.70 and 8.56±4.11 respectively, which issignificantly higher than non gated PET/CT, 12.76±6.74 and 7.66±4.00 (P<0.001); theincrease rate of SUVmax is up to 39.99%, with a maximum of 32.34%, both the average increaserate is 7.29% and 11.72% (P<0.001). SUVmax in the gated and non gated PET/CT is different,but the correlation is very good (r=0.971), the relevant equation is y = 1.384 +0.964x; in thegated imaging, 6 time phases are artificially distinguished according to respiration curve, whichare respectively measured on the SUVmax and SUVmean, compared with non gated imaging, itis found that: SUVmean and SUVmax of all phase gated imaging are higher than those ofnon gated imaging; in all phases, phase1 is maximum, and the phase 4 is minimum; there is nosignificant difference in different phases (P>0.05), but the correlation of change in SUV is highbetween the different phases and non gated imaging (P<0.01). In this study, four lung noduleswith SUV<2.5 (defined as a mild intake) with conventional imaging are analyzed, and SUVmaxon one nodule in the gated imaging is rose to 2.52 by 2.13, with the change rate of 18.31%, it isindicated that the improving for SUV value in the gated imaging is likely to influence theimprovement of clinical diagnosis and staging;②Comparingwithgatedandnon gatedPET/CTimagingforlesionvolumesizemeasurements,it is discovered that: lung nodule volume measured in non gated PET/CT is 5.27±7.74,removing respiratory motion artifacts, lung nodule volume in RG PET/CT is significantlyreduced by only 4.36±6.97, there are statistically significant differences between the two, but agood correlation (r=0.957) exists between the volume measured in RG PET/CT imaging andnon gated imaging with different phases ; the radiotherapy target is outlined for a patient withRG PET/CT, as the impact of respiratory movement in the scope and size has been considered inRG PET/CT imaging, the corresponding radiotherapy target area may be reduced.③37 nodules were selected for PET and CT lesion size and shape of a more consistent level,with 42% of the maximum SUV outlined gated six phase and non gated PET imaging lesions,mainly around the places of head feet, anterior posterior and left right. The results showed thepulmonary nodules moved with three dimensional motion along with respiratory motion, Phase3 moved up and down farthest, which could reach the maximum rate of 1.72±5.88cm. Theresults also showed that respiratory motion was most obvious during the head feet, namely, upper and lower range of body, and there was no significant correlation between non gated andgated imaging; the correlation with two imaging method was very good in left right mobile,except Phase 5; the correlation with Phase 4 and Phase 5 was also very good in anterior posteriormobile.④This study appears in the collection of existing conditions, there is no significant SNR ingated and non gated PET/CT; in the premise without affecting the image quality, the CT tubecurrent is reduced to 30mA, irradiation dose is lower, but still 1.5 times higher than conventionalscanning.CONCLUSIONSRG PET/CT can significantly improve the SUV of pulmonary nodule, and change the diagnosisand staging accordingly; RG PET/CT can reduce nodule size, help to determine the true size ofthe nodules, provide the basis for the radiotherapy target delineation; there is a good correlationin the SUV and size of lesions between different gated phases and non gated imaging;pulmonary nodules move with three dimensional motion along with respiratory motion, Phase 3moves up and down farthest. Up down displacement is more obvious than the left right andanterior posterior motion; the SNR of RG PET/CT is close to the non gated. RG PET/CT has agood prospect for clinical application. Objective An analysis on useful value of 18F FDG PET/CT in carcinomatous pleural effusion.Materials and methods Twenty two patients with pleural effusion refered to our departmentfor whole body 18F FDG PET/CT.9 patients with carcinomatous pleural effusion and 7 patientswere confirmed by means of diagnostic thoracocentesis, biopsy,or clinical follow up.Theattribution of pleural effusion in 11 patients with cancer was not proved.Respectively ananlyzeddifference of SUVmax from carcinomatous and benign pleural effusion,of CT and PET findingsin pleura.Results No significant difference was seen in the degree of FDG uptake in carcinomatous andbenign pleural effusions.In the 9 patients of carcinomatous pleural effusion PET found 31nodules,only CT showed 13 nodules。In addition,PET showed 20 local uptake in 12 pleuralthickening lesions. Simultaneously,PET/CT show more much pleural nodules and nodularpleural thickening.Conclusions SUVmax of pleural effusion itself and dual time point FDG PET imaging are notvaluable in differentiating carcinomatous from benign pleural disease。PET/CT is helpful toestablishment of the diagnosis on carcinomatous pleural effusion.
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