低剂量CT扫描在儿童胸部检查中的应用

随着CT在临床上的广泛应用及病人检查次数的增加,CT检查所致的X线辐射引起人们的广泛关注。辐射致癌已得到公认,特别对于儿童,由于其器官尚未发育完善,对X线较敏感,其相应的X线致癌风险大幅提高,因此降低儿童检查的辐射剂量非常重要。由于肺组织含气量较多,组织结构具有优良对比,使得胸部低剂量CT扫描得以广泛应用。儿童与成人的胸部解剖生理特点不同,就目前各种低剂量CT扫描技术和迭代重建技术在儿童胸部CT扫描中的应用,及其降低X线辐射剂量的效果予以综述。     

螺旋CT检查中无定位图像扫描操作技术

在螺旋CT检查中，首先进行定位图像扫描，然后在定位图像上确定扫描起始点和终止点，以此确定扫描范围。经过实践，笔者认为有很多部位做CT扫描，无需扫描定位图像，可直接在体表定位确定扫描范围进行螺旋扫描，同样达到诊断要求，减少了患者的受照剂量。特别是多层螺旋CT（MSCT）应用以来，大范围扫描得以开展，象胸腹主动脉加下肢动脉CT血管造影（CTA）检查，扫描定位图像患者的受照时间是16s左右。运用无定位图像扫描操作技术，患者就可以减少这些受照剂量。     

儿童CT检查的放射防护

近几十年来,CT成为诊断疾病的重要影像学手段之一.但是,考虑到患儿的高辐射敏感性,行CT时应当慎重.可以通过对剂量指数、剂量长度乘积、扫描层厚和面积这些CT相关参数的控制来降低患儿受照剂量.在保证CT图像清楚的前提下,对管电流、管电压、螺距的控制,同样可降低患儿受照剂量.通过有效剂量和集体剂量评估患儿的受照剂量.应当在辐射防护三原则的基础上开展患儿CT检查工作.     

多层螺旋CT低剂量扫描诊断肺结节的价值

目的:探讨多层螺旋CT低剂量扫描诊断肺结节的价值。材料和方法:对147例肺部结节患者分别行多层螺旋CT低剂量扫描和常规剂量扫描,进行双盲法分析。结果:低剂量螺旋CT显示的结节较常规剂量扫描稍小,但二者对结节的检出无明显差异。结论:低剂量螺旋CT扫描与常规螺旋CT扫描发现肺结节的几率相仿,但可以有效地降低患者的受照剂量。     

儿童CT检查中扫描参数的优化

目的 了解儿童CT检查扫描条件选择及其所致辐射剂量的相关性,以期通过适当调节mAs、扫描长度等参数,降低儿童CT检查患者受照剂量。方法 比较江苏省7家医院不同年龄组（<1岁、1~5岁、6~10岁和11~15岁）儿童头颅、胸部、腹部多排螺旋CT检查主要扫描参数的差异。选用相同的检查参数在TM160剂量模体上测量CTDI₁₀₀,计算DLP,并通过经验加权因子,估算出不同部位检查的有效剂量（E）。对mAs、扫描长度和DLP进行多元线性回归分析,比较两家典型医院由于选择扫描条件不同所导致的剂量差异。结果 儿童头颅、胸部、腹部CT检查所致患者的有效剂量均值分别为2.46、5.69、11.86 mSv,各部位检查DLP与mAs、扫描长度均呈正相关（r=0.81、0.81、0.92,P<0.05）。较高的mAs选择,致使本研究各年龄组儿童胸腹部CT检查有效剂量是德国Galanski等研究的1.2~3.0倍;B医院各年龄组腹部检查选择了较高的扫描长度,以致其所致有效剂量均高于本研究均值。结论 建议通过合理优化儿童不同部位CT检查mAs、扫描长度等扫描参数,降低受检者所受辐射风险。     

儿童在头颅CT检查中的辐射防护

目的:探讨儿童在头颅CT检查时的辐射防护方法,减少其受照剂量.方法:运用放射实践的正当化和防护的最优化的原则,选择合适的曝光参数,做好相应的防护措施.结果:通过上述方法完成检查,可显著降低儿童的受照剂量.结论:儿童尚处于生长发育的关键阶段,对X线具有较高的敏感性,在CT检查中必须加强对儿童的辐射防护.     

四川省CT机头部单层扫描剂量评价

随着X线计算机体层摄影装置（CT）的应用越来越普遍，在诊断过程中所致受检者受照剂量水平也日益受到关注。结合CT机应用性能的检测，笔者对四川省CT机头部单层扫描剂量（CTDI）作了抽查，反映出四川省目前CT检查所致患者的受照剂量水平。同时，采用两种常用的方法对CTDI进行描述，并对测量结果加以比较。     

儿童胸部CT扫描时腹部屏蔽方法与效果研究

目的 研究儿童胸部CT扫描时腹部的屏蔽方法及其效果。方法 用美国CIRS公司生产的5岁儿童体模代替儿童受检者,在腹部内布放热释光剂量计LiF（Mg,Cu,P）,按儿童胸部CT扫描的通常程序对体模进行扫描,测量在无屏蔽、用铅衣覆盖和用铅衣包裹时腹腔内主要器官与组织的剂量。结果 儿童胸部CT扫描时,腹腔内部分器官的吸收剂量可达到数mGy。3种扫描之间,相同位置处的剂量值差异有统计学意义（χ²=16.00,P<0.05）;正面覆盖和包裹屏蔽方式之间的剂量值差异有统计学意义（Z=-2.52,P<0.05 ）。较之于无屏蔽措施,采用0.35 mm铅衣包裹腹部,可分别降低睾丸和结肠的剂量71.2%和42.3%,采用同样当量铅衣铺盖腹部剂量可降低55.9%和26.1%。结论 开展儿童胸部CT扫描时,使用铅防护衣可有效屏蔽腹部受照,对性腺和结肠的防护具有重要作用,特别是包裹式的屏蔽措施值得推荐。     

婴儿头颅CT中铋屏蔽对辐射剂量和影像质量的影响

目的 研究婴儿头颅CT检查中使用铋屏蔽材料降低眼晶状体受照剂量的效果及对图像质量的影响。方法 使用适合患儿使用的自制铋屏蔽防护眼罩、婴儿体模,采用热释光探测器测量受照剂量。CT扫描条件选择120 kV、130 mA轴位扫描,分别进行铋屏蔽和无屏蔽两组模体测试,比较模体内相当于晶状体位置的受照剂量;应用同样CT扫描参数,对临床疑为颅内出血的99例患儿佩戴铋屏蔽眼罩后进行头部扫描,由2名高年资医生分别进行图像质量评估,并比较评分的一致性。结果 体模实验显示,无屏蔽时眼罩后方区域吸收剂量为25 mGy,经铋防护眼罩屏蔽后眼罩后方的吸收剂量为17 mGy,降低辐射剂量32%。佩戴铋屏蔽眼罩对患儿头部CT图像质量无明显影响。结论 在婴儿头颅CT扫描中使用铋屏蔽防护眼罩,可明显降低眼晶状体放射吸收剂量,同时对CT图像质量的影响是可接受的。     

低剂量扫描在常规CT定位图像中的应用

近年来,随着CT机的普及,辐射剂量对人体造成的潜在危害以及如何在有效保证图像质量的前提下降低放射剂量,受到越来越多医务工作者的关注.在螺旋CT检查中,首先进行定位图像扫描,然后在定位图像上确定扫描起始点和终止点,以此确定扫描范围.相对于CT诊断图像而言,定位扫描剂量常常被忽视,常规剂量定位扫描不仅增加患者的辐射剂量,同时也使球管寿命缩短.如果无定位图像扫描,又不能具体的确定扫描范围,为了减少患者的受照剂量,减少曝光时间、延长球管的使用寿命,在不影响定位的前提下,笔者对常规CT定位图像扫描参数进行了改进,得到了很好的效果,现报道如下.     

CT of 338 active professional boxers.

Computed tomography (CT) was performed in 338 active professional boxers. CT scans were abnormal in 25 boxers (7%). The most common CT abnormality was brain atrophy (22 cases). Focal lesions of low attenuation consistent with posttraumatic encephalomalacia were noted in only three boxers. Boxers with abnormal CT scans did not differ from those with borderline or normal CT scans in regard to age, win-loss record, number of bouts, or history of an abnormal electroencephalogram. Thirty-seven boxers with borderline CT scans (49%) and 17 with abnormal CT scans (68%) reported a previous technical knockout (TKO) or knockout (KO), compared with only 89 (37%) of the 238 boxers with normal CT scans (P < .01). Brain atrophy was noted more frequently in boxers with a large cavum septum pellucidum (CSP) than in those with a small or no CSP (P < .05). Boxers with abnormal or borderline CT scans who experienced a TKO or KO were slightly older than those with normal CT scans and a history of a TKO or KO (P < .05).     

Effect of spineboard and headblocks on the image quality of head CT scans

Trauma patients at risk for, or suspected of, spinal injury are frequently transported to hospital using full spinal immobilisation. At the emergency department, immobilisation is often maintained until radiological work-up is completed. In this study, we examined how these devices for spinal stabilization influence visual image quality. Image quality was judged for both patient CT scans and phantom CT scans. CT scans of 217 patients were assessed retrospectively by two radiologists for visual scoring of image quality, scoring both quantity and impact of artifacts caused by the immobilization devices. For the phantom CT scans, eight set-ups were made, using a vacuum mattress without headblocks and a rigid and a soft-layered spineboard without headblocks, with standard soft-foam headblocks, or with new design headblocks. Overall, artifacts were found in 67 % of CT scans of patients on immobilization devices, which hampered diagnosis in 10 % of the cases. In the phantom CT scans, artifacts were present in all set-ups with one or more devices present and were seen in 20 % of all scan slices. The presence of headblocks resulted in more artifacts in both the patient CT scans and the phantom CT scans. Considerable effort should therefore be made to adjust the design of the immobilization devices and to remove the headblocks before CT scans are made.     

双螺旋CT增强扫描对外伤性肾损伤的诊断价值

目的:探讨CT增强扫描在对伤性肾损伤诊断中的应用价值。材料和方法:回顾性分析28例肾损伤的CT平扫及增强扫描表现。结果:28例中,平扫能确诊肾损伤20例、可疑肾损伤5例、未见异常3例,敏感性89.2%、特异性71.4%;CT增强扫描后,全部确诊为肾损伤,敏感性100%、特异性100%。结论:CT增强扫描在外伤性肾损伤的诊断中具有重要的作用,能明显提高诊断准确率。     

Chronic diffuse infiltrative lung disease: comparison of diagnostic accuracy of high-resolution and conventional CT

We compared the accuracies of high-resolution CT (HRCT) and conventional CT in determining the specific diagnoses in 75 consecutive patients with chronic diffuse infiltrative lung disease. Without knowledge of clinical or pathologic data, two reviewers independently assessed three separate sets of CT scans in random order: three HRCT scans, three 10-mm collimation CT scans obtained at the same levels as the HRCT scans, and a complete conventional CT scan. The HRCT scans were obtained at the level of the aortic arch, tracheal carina, and 1 cm above the right hemidiaphragm by using 1.5-mm collimation and a high spatial resolution algorithm. Observers gave the most likely diagnosis along with their degree of diagnostic confidence. The correct diagnosis, irrespective of confidence level, was reached with 71% of the HRCT scans and with 72% of both the corresponding 10-mm and complete conventional CT scans. Confidence level 1 (definite) was reached with 49% of HRCT scans, 31% of corresponding 10-mm scans, and 43% of complete conventional CT examinations; the correct diagnosis was made in 92%, 96%, and 94% of those examinations, respectively. In none of the patients were findings on the limited HRCT scan normal when findings on the conventional CT scan were abnormal. We conclude that in most patients with chronic infiltrative lung disease a specific diagnosis can be made by obtaining a limited number of HRCT scans.     

颞骨平行枕眶线多层螺旋CT扫描法及其价值

目的:探讨以平行枕眶线扫描图像为基础的常规轴位和冠状位MPR图像是否能够取代直接轴位和冠状位图像。方法:三位医师分别观察50例颞骨CT扫描图像,分析直接常规轴位(25例)、冠状位(25例)CT扫描图像和其相应的常规轴位、冠状位MPR图像显示颞骨结构的差异。结果:所有观察者均认为直接常规轴位、冠状位CT扫描图像略优于相应的轴位、冠状位MPR图像。直接轴位、冠状位CT扫描图像和相应的轴位、冠状位MPR图像的质量差异较小。结论:以平行枕眶线扫描图像为基础的常规轴位和冠状位MPR图像可取代直接轴位和冠状位扫描图像。     

Effectiveness of contrast regimens in CT detection of vascular malformations of the brain

Forty-three patients with cerebral vascular malformation were studied with precontrast, immediate contrast, and 1 hr delayed high dose contrast computed tomography (CT) scans. The precontrast scans were abnormal in 81% of patients. The delayed high dose scans demonstrated one angiographically occult, thrombosed arteriovenous malformation not seen on pre- or immediate contrast scans, four cases with additional zones of encapsulated hemorrhage or infarction not seen on pre- or immediate contrast CT, and two cases of venous angiomas seen on immediate contrast scans but not on delayed high dose scans. In 50% of patients, large vessels surrounding the malformation faded on the delayed dose scans which were less specific for vascular malformation than immediate contrast CT. We conclude that: (1) delayed high dose scans offer no significant advantage in patients with symptoms suggesting vascular malformation of the brain; and (2) while less specific than immediate contrast CT, these scans do not preclude detection of vascular malformations of the brain. Therefore, delayed high dose CT can be used in patients with suspected blood-brain barrier lesions without fear of missing vascular malformations.     

Treatment response on CT scan in patients with brain metastases treated with irradiation

To evaluate the role of CT scans in the assessment of response to therapeutic irradiation of brain metastases, CT findings of 64 patients were reviewed retrospectively. Enhanced tumor on CT scans disappeared in 21 patients, who survived significantly longer than those whose CT scans showed less than 50% regression (p less than 0.01). Ring contrast enhancement (ring CE) of the tumor on pre-RT CT scan did not seem to affect the patient's prognosis for survival. Tumors with ring-CE on pre- and post-RT CT scans, however, did not regress as much as those without ring-CE. Patients without ring-CE on pre- and post-RT CT scans tended to survive longer than those with ring-CE. This study suggests that tumor regression and the CE pattern on pre- and post-RT CT scans would be useful prognostic indicators for patients with brain metastases.     

Hypersensitivity pneumonitis: evaluation with CT

Thirteen chest radiographs and computed tomographic (CT) scans obtained from 11 patients with hypersensitivity pneumonitis were reviewed. The CT findings were correlated with open lung biopsy findings in seven patients. The two patients with acute hypersensitivity pneumonitis showed air-space opacification on CT scans. An open lung biopsy, done in one of these patients, demonstrated noncaseating granulomas and filling of the air spaces with macrophages. The nine patients with subacute hypersensitivity pneumonitis showed small, rounded opacities and patchy air-space opacification on CT scans. These findings reflected the histologic findings, which consisted of interstitial pneumonitis, cellular bronchiolitis, and small, noncaseating granulomas. The six patients with symptoms for 12 months or longer also showed irregular linear opacities on CT scans, corresponding to areas of fibrosis. CT scans were superior to radiographs in helping to assess the type and extent of abnormalities, and high-resolution CT scans were superior to conventional CT scans.     

Complex fractures of the proximal humerus: role of CT in treatment

The authors reviewed the computed tomography (CT) scans, plain radiographs, and subsequent treatment of 17 patients with complex proximal humeral fractures. CT scans and radiographs were compared in the demonstration of fracture lines, displacement of fracture fragments, rotation of fragments relative to their normal positions, and status of the head and articular surface of the humerus. The impact of CT findings on the decision to treat with surgery versus closed reduction and on the choice of surgical procedure was assessed. Surgery was not performed in nine patients because CT scans showed no significant displacement of fragments previously judged displaced or "indeterminate" on radiographs. Surgery was performed in eight patients; CT demonstrated significant abnormalities not definitely shown with radiography. In six of these eight patients, CT scans demonstrated unsuspected abnormalities that directed the choice of surgical procedure. CT scans provide clinically useful information for the treatment of complex proximal humeral fractures when radiographs provide inadequate or indefinite information.     

本院CT辐射剂量参考水平与警示值的建立及其在胸部CT剂量优化中的运用尝试

目的 通过建立本医疗机构胸部CT辐射剂量参考水平与警示值,并以此指导本院进行胸部CT扫描方案与检查流程的优化,控制CT受检者所受剂量水平。方法 连续调取浙江大学医学院附属第二医院2018年1月1日至2019年12月31日进行胸部CT扫描的205 511例受检者资料,根据检查时间将受检者分为改进前和改进后两组。改进前组为2018年度进行胸部CT检查的受检者,共90 507例,改进后组为2019年度进行检查的受检者,共115 004例。设定2018年度胸部CT辐射剂量分布的均值为本院胸部CT辐射剂量指导水平（DRL）,第75个百分位数和第25个百分位数为本院辐射剂量诊断参考范围（diagnostic reference range,DRR）的上限和下限,第97.5个百分位数为本院CT辐射剂量警示值,超过DRR上限则认为辐射剂量偏高,超过警示值则认为辐射剂量超高。根据2018年度胸部CT超高剂量扫描的原因分析结果,对2019年度受检者的胸部CT的扫描方案与检查流程进行改进。统计改进前后行胸部平扫CT、胸部增强CT、肺癌筛查低剂量CT的受检者人次、偏高剂量扫描人次、超高剂量扫描人次、单次扫描剂量;统计改进前后因不同原因造成剂量超高的人次、占比。将改进前后两组受检者各项参数进行统计学比较。结果 改进后本院胸部平扫CT受检者的平均扫描剂量下降8.67%,两组比较差异有统计学意义（t=55.71,P<0.05）,胸部低剂量CT受检者的平均扫描剂量下降20.13%,差异有统计学意义（t=81.99,P<0.05）;改进后胸部增强CT受检者的平均扫描剂量与改进前差异无统计学意义（P>0.05）;改进后辐射剂量偏高的胸部CT受检者比率较改进前减少9.18%,其中胸部平扫CT、胸部低剂量CT受检者比率分别减少3.66%、17.15%,改进后辐射剂量偏高的胸部增强CT受检者比率增加1.7%;改进后辐射剂量超高的胸部平扫CT、胸部增强CT、胸部低剂量CT受检者比率较改进前分别减少0.55%、1.06%、1.74%;超高剂量扫描的受检者中,改进后剂量可优化的受检者比率较改进前分别减少4.72%、31.49%、19.18%。结论 建立本院胸部CT辐射剂量参考水平及剂量警示值有助于推动剂量优化,降低受检者平均剂量,避免高剂量扫描。