【作者】 武志芳；

【导师】 李思进；

【作者基本信息】 山西医科大学 ， 内科学， 2011， 博士

【摘要】 背景PET／CT（Positron emission tomography/ computed tomography，PET／CT）的分子水平PET检查的高灵敏度、特异性结果与清晰显示解剖的CT的结果相结合，尤其在肿瘤、神经系统方面，已经使其成为一个广为接受的对肿瘤的诊断、评估、分期和再分期的手段。在PET／CT系统中，CT扫描很快，普及型CT全身扫描需要数秒时间，一个呼吸周期基本能得到所需的图像，获得的图像几乎是某时刻的快照，因此基本不受呼吸运动影响；而PET扫描速度较慢，每个体位PET采集要2分钟-10分钟，获得的是经历几个，甚至几十个呼吸周期的平均图像。因此在对肺部进行PET／CT扫描时，由于CT扫描速度明显快于PET扫描速度，PET和CT扫描受呼吸运动位移的影响不同，从而导致PET／CT图像中相同层面的PET图像和CT图像在位置及相位上存在一定程度的不匹配而形成PET图像伪影。另外一个产生呼吸伪影的原因是由于在PET／CT系统中，PET图像的衰减校正是通过CT扫描得到的组织密度图像完成的，同一个患者的PET图像和CT图像在空间位置和时相上并不完全匹配(特别在运动幅度最大的膈膜附近)，用瞬间的CT图像去对平均PET的图像做衰减校正必然出现误差，导致PET图像出现伪影，可能影响胸腹部肿瘤的准确诊断与治疗计划的制定。控制呼吸伪影对肺部病变的诊断、癌症分期和放疗靶区的划定有很重要的意义。呼吸控制技术以1999年开展的主动呼吸控制（active breathing control，ABC）技术和深吸气呼吸控制（deep-inhalation breath holding，DIBH）技术为代表。减少呼吸所致运动的方法有：外源性呼吸限制(如：呼吸机的强制通气)和自我呼吸限制(随呼吸命令进行呼吸控制)，还有就是通过呼吸运动监测设备进行呼吸门控。由于前者要求患者必须进行呼吸训练，许多患者并不能耐受这一过程。目前呼吸门控成为减少呼吸伪影和进行放疗靶区划定的依据。呼吸门控的PET／CT显像（respiratory-gated PET/CT，RG PET/CT），即4D PET／CT的呼吸门控采集，是指通过特定的设备采集呼吸运动信号，利用特殊的扫描程序，将呼吸周期分为若干时相，然后将与呼吸信号同步采集的各时相图像信息归类分析，将处于同一呼吸时相的PET图像和CT图像进行配准和衰减校正，从而提供病灶三维空间影像随时间变化的运动信息。其中CT图像不仅提供解剖学信息，还用于PET图像的衰减校正。国外有少量文献对RG PET／CT进行了报道，但国内仅有数篇综述，尚未见到任何临床研究报道。国外对PET/CT及4D CT对放疗生物靶区划定的意义做了较多研究，而对RGPET／CT对放疗靶区划定的价值尚无定论；少量文献对呼吸幅度门控PET/CT的标准化摄取值(standard uptake value，SUV)、肿瘤体积和信噪比进行了研究。RG PET／CT对呼吸伪影校正的价值，呼吸门控PET中各种半定量指标如SUV值对临床诊断、分期和放疗靶区的勾画的价值成为临床研究的热点。目的通过复习文献及模拟呼吸器的采集，建立合适的RG PET/CT条件和方法；对肺部结节进行RG PET/CT门控采集，并与非门控PET/CT进行比较，初步探讨呼吸门控技术对肺部结节SUV、体积估测的影响；测量呼吸运动所引起的位置移动变化；对呼吸门控技术不同时相与非门控采集肺部结节SUV、体积和位移进行相关性分析；观察RG PET/CT与常规采集信噪比的差异及辐射剂量的差别，以期为临床提供有价值的信息。方法2010年5月至2011年3月在我科进行PET/CT显像的患者，发现有多个肺部结节，并同意进行呼吸门控显像的患者共19例，14例患者进入本研究，其中男6例，女8例，年龄29~80岁，平均年龄（63.7±7.1）岁。PET/CT为GE Discovery VCT型。18F-FDG注射剂量按5.55～7.40 MBq/kg计算，注药后静卧休息60 min，显像前排空膀胱。然后用3D模式采集PET图像，约6—7个床位。按2 min／床位进行PET扫描，用CT对PET图像进行衰减校正、图像重建和融合。呼吸门控采集时要求患者平稳、均匀呼吸，用Varian公司实时监测系统记录呼吸曲线，并向PET／CT采集控制系统发送呼吸运动节律信号。先启动呼吸控制系统记录呼吸节律信号，再进行RG PET/CT采集。CT为4D扫描，PET共扫1个床位6分钟，分为6个bins。CT图像的“后门控”处理在后台工作站上进行。先对呼吸曲线设置不同的相位值，共设定6个时相（phase1-phase6）：0，16%，33%，50%，66%，83%，吸气末为0，呼气末为50％，下一个吸气末为100％(即0时相)，一直循环；再对不同相位设置运动幅度可接受的相位范围；最终得到6个相位的多层CT图像系列。将得到的不同时相CT重新发回采集工作站，PET扫描的呼吸门控图像在后处理工作站自动划分为6个时相的呼吸门控系列图像，从而得到相匹配的一个呼吸周期内6个时相的PET/CT融合图像。SUV、体积和位移由AW系统半自动分析获得，每个肺部结节的每个指标均要进行非门控图像、门控显像的6个时相共七次测量。SNR由公式算出。部分病人进行了放疗靶区的勾画。结果①通过复习文献和呼吸模拟器的呼吸门控采集，在保证PET计数和CT图像质量的基础上，尽可能避免CT的辐射危害，得到了适合临床应用的RG PET/CT采集方法。呼吸门控CT采集条件管电压120KV，管电流30mA，扫描范围略大于PET一个床位即15.7cm，螺距及层厚均为固定采集条件，只有电影采集时间(cine duration=234567+18)随着每个病人不同的呼吸周期而变化；呼吸门控PET采集条件与常规采集不同，主要为呼吸信号触发的每个床位6分钟、6个bin的采集，制定成专门的采集协议，每个病人均可用此协议完成采集。②本研究对37个肺部结节进行RG PET/CT检查，结果发现呼吸门控显像可以提高病灶的SUV值。SUVmax和SUVmean分别可以达到13.69±6.70和8.56±4.11，明显高于非门控PET/CT 12.76±6.74及7.66±4.00 9P <0.001:；SUVmax提高率可高达39.99%，最高为32.34%，二者平均提高率为7.29%和11.72%（P <0.001）；SUVmax在门控与非门控PET/CT中有差别，但相关性非常好（r=0.971），线性回归方程为Y. =1.384+0.964x；在门控显像中，根据呼吸曲线人为区分出6个时相，分别对SUVmax与SUVmean进行测定，并与非门控显像分别进行比较发现：门控显像各时相SUVmax与SUVmean均高于非门控显像；不同时相间以phase1即吸气末最高，而phase4（呼气末吸气初）最低；不同时相彼此之间差异无统计学意义（P>0.05），但不同时相与非门控显像SUV变化相关性很高( P <0.01)；本研究还对4个结节常规显像中SUV<2.5(定义为轻度摄取)的肺部结节进行了分析，发现其中有一个结节SUVmax在门控显像中由2.13升至2.52，变化率达到18.31%，如果以临床判断标准SUV是否大于2.5作为标准，那么呼吸门控显像有可能影响到临床诊断和分期；③用呼吸门控与非门控PET显像对病灶体积大小的测量比较发现：非门控PET/CT测定肺部结节体积为5.27±7.74，去除呼吸运动伪影，应用RG PET/CT所得到的病灶体积明显减小，更趋于真实，仅有4.36±6.97，二者之间差别有统计学意义，且二者间有很好的相关性（r=0.957）；RG PET/CT显像不同时相与非门控显像所测定的体积有很好的相关性；对1名患者应用RG PET/CT进行了放疗靶区勾画，由于RG PET/CT所测定的病灶范围和体积已经考虑了呼吸运动影响，所以有可能减小相应放疗生物靶区的面积；④对37个结节分别选取不同呼吸时相PET和CT病灶匹配的层面，对每个结节进行三维测定包括非门控状态1次，门控状态6个时相共6次，因此每个结节处理7次，得到相应的三维位置变化，主要由前后位、头脚位和左右位组成。由于每个结节位置不同，不能进行统计分析，因而采用以Phase 1即吸气末作为参考点（“0”），其他时相与第一时相求差值后进行比较，观察其结节的运动，并描绘出每个病灶运动的轨迹。结果显示：肺部结节的呼吸运动呈现三维运动；呼吸运动在头脚位，即沿身体长轴上下移动幅度最明显，其中Phase3即呼气末移动幅度最大F上下移动的幅度最大可以达到(1.72G5.88)cmH非门控显像与呼吸门控不同时相间位置移动没有相关性。⑤本文研究显示在现有的采集条件下，门控与非门控PET/CT显像SNR差别没有统计学意义，表明现有采集条件能满足图像判定的要求；在不影响图像质量的前提下，将CT管电流降至30mA，减少了患者所受照射，每个床位患者所接受的辐射剂量均高于非门控显像；在RG PET/CT显像中，经过模拟呼吸周期和cine duration参数我们得到:呼吸门控PET/CT辐射剂量与呼吸周期呈正相关关系，呼吸周期越长，完成扫描所需要的时间越长，遭受的辐射剂量越大。结论①RG PET/CT在实时呼吸门控监测仪器记录呼吸曲线和患者自由、平稳呼吸的前提下，4D CT采集条件管电压120KV，管电流30mA，及4D PET呼吸信号触发的每个床位6分钟、6个bins的采集就能满足临床要求；②RG PET/CT与非门控采集相比较，可以显著提高肺部结节SUV值，从而改变疾病的诊断和分期；③RG PET/CT可消除呼吸伪影，使病灶的大小更趋于真实，为放疗生物靶区勾画提供更加准确的依据；④通过RG PET/CT对不同门控时相的肺部病灶三维位置位移的分析，肺部病灶呼吸运动呈现三维运动，其中以沿身体长轴上下位置移动的幅度最明显；⑤管电流为30mA进行的RG PET/CT采集，信噪比接近于非门控显像，能满足临床需求；⑥RG PET/CT辐射剂量高于非门控采集，呼吸门控PET/CT辐射剂量与呼吸周期呈正相关关系，呼吸周期越长，完成扫描所需要的时间越长，遭受的辐射剂量越大。目的：初步评价18F-FDG PET/CT在癌性胸腔积液中应用价值。资料与方法：回顾性分析27例胸腔积液患者，经胸腔穿刺或随访证实，恶性胸水9例，良性胸水7例，未经证实的肿瘤合并胸水11例。分析癌性胸腔积液SUVmax（避开胸膜和肺组织）、胸膜结节及增厚的PET/CT表现。结果：良、恶性胸腔积液的SUVmax比较，差异无统计学意义。良、恶性胸水各自在双时间点显像的SUVmax比较，差异无统计学意义。9例癌性胸水中，PET发现31处局灶性高代谢灶，CT仅发现13枚胸膜结节。12处CT表现胸膜增厚的病灶中，PET显示20处局灶性高代谢灶。结论：胸腔积液本身的SUVma及双时间点显像SUVmax对癌性、良性胸膜病变鉴别没有价值。PET/CT有助于癌性胸膜病变的定性诊断。更多还原

【Abstract】 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.更多还原