Spectral CT imaging: Technical principles of dual-energy CT and multi-energy photon-counting CT

Spectral computed tomography (CT) imaging encompasses a unique generation of CT systems based on a simple principle that makes use of the energy-dependent information present in CT images. Over the past two decades this principle has been expanded with the introduction of dual-energy CT systems. The first generation of spectral CT systems, represented either by dual-source or dual-layer technology, opened up a new imaging approach in the radiology community with their ability to overcome the limitations of tissue characterization encountered with conventional CT. Its expansion worldwide can also be considered as an important leverage for the recent groundbreaking technology based on a new chain of detection available on photon counting CT systems, which holds great promise for extending CT towards multi-energy CT imaging. The purpose of this article was to detail the basic principles and techniques of spectral CT with a particular emphasis on the newest technical developments of dual-energy and multi-energy CT systems.     

胃窦癌64层螺旋CT灌注成像特点及其与肿瘤血管生成的关系

目的利用64层螺旋CT探讨胃窦癌的CT灌注特点,并探讨其与肿瘤血管生成间的关系。方法 30例胃窦癌患者（胃窦癌组）的CT灌注参数与24例正常胃患者（对照组）进行比较,胃窦癌各灌注参数与MVD及VEGF进行了相关性分析。结果在胃窦癌组与对照组患者CT灌注参数的比较中,胃窦癌组血容量（BV）明显高于对照组（P〈0.01）,而2组灌注值（PF）、强化峰值（PE）和达峰时间（TTP）的差异无统计学意义（P〉0.05）。BV与胃窦癌患者MVD计数呈正相关（r=0.522,P=0.02）,而PF（r=0.072,P=0.78）、PE（r=0.253,P=0.31）和TTP（r=0.235,P=0.35）与胃窦癌MVD计数无相关性。PF（r=-0.208,P=0.45）、PE（r=-0.251,P=0.37）、TTP（r=-0.284,P=0.31）和BV（r=-0.472,P=0.09）与VEGF表达均无相关性。结论 BV能反映胃窦癌内血管生成的状况,CT灌注成像可以作为胃窦癌微血管状态的评价工具。     

计算机断层扫描螺旋尿路成像与仿真内窥镜技术的临床应用

目的 探讨螺旋CT尿路成像（SCTU）与CTVE）的检查方法、成像技术以及在泌尿外科疾病中的应用价值,提高诊断水平。方法 应用螺旋CT对46例泌尿系统疾病患者（包括肾肿瘤2例,肾盂旁囊肿2例,输尿管结石6例,输尿管狭窄4例,输尿管肿瘤2例,重复肾重复输尿管畸形1例,膀胱肿瘤28例,膀胱子宫内膜异位症1例）行容积扫描,所得数据在工作站利用软件进行后处理,获得泌尿系立体图像;并对6例输尿管疾病、29例膀胱疾病患者进行了CT仿真内窥镜（CTVE）成像。所有图像均与B超、静脉尿路造影、逆行肾盂造影、常规CT扫描、膀胱镜检查等比较。并将术中所见或病理结果作为诊断的金标准。结果 所有患者均取得了高质量的泌尿系图像,除1例膀胱肿瘤（肿瘤直径为4mm）漏诊外,其余患者均得到了明确诊断,并与手术或病理结果相符合。结论 SCTU与CTVE是较可靠的非侵入性检查手段,具有一定的优越性,可作为泌尿系常规检查方法的有益补充。     

CT in pelvic trauma

The use of computed tomography is extremely important in the care of patients with pelvic trauma. We believe that it should be performed on all patients with severe pelvic injury. It depicts the pelvic anatomy in exquisite detail, enabling one to plan therapy on the basis of pathologic anatomy rather than the presumed mechanism of injury. CT is more expensive than tomography but gives considerably more information at a lower radiation dose. It is also of considerable value in postoperative follow-up for determination of the adequacy of reduction and fracture healing.     

CT guided extralemniscal myelotomy

Summary CT guided Extralemniscal Myelotomy (E.M.) is described. Direct visualization of the target is the main advantage of the method. The method was applied successfully in two patients.Presented at the European Congress of Neurosurgery in Barcelona, 1987.     

CT引导下组织间植入 125 I粒子治疗肺癌的临床应用

目的 探讨CT引导下组织间植入125I粒子治疗肺癌的临床价值. 方法 18例肺癌患者采用CT引导下125I放射性粒子植入.粒子植入之前采用三维治疗计划系统模拟布源,在螺旋CT引导下将125I粒子植入肿瘤组织内.术后2个月复查CT一次,随访6个月. 结果 全组18例18个病灶共植入粒子812粒,平均每个病灶植入粒子45.1粒.2个月后采用CT评价,完全缓解(CR)7例,部分缓解(PR)10例,无变化(NC)1例,总有效率(CR PR)为94%(17/18). 结论 经皮穿刺放射性粒子组织间永久植入治疗中晚期肺癌为一种近期疗效满意、微创、低毒的新方法,值得进一步临床应用,长期观察.     

CT in der Traumadiagnostik

The recent introduction of ultrafast multidetector CT (MDCT) scanners has had a great impact on daily clinical routine, especially in the diagnostic processing of patients with trauma. The acquisition of very thin slices means that the result of a CT examination is no longer seen as a stack of slices in a defined transverse orientation that needs to be determined before the examination starts, but more as a volume. This allows all images to be handled as a 3D dataset with the option of computing secondary slices in any desired orientation without the repeated application of radiation. The diagnostic management of polytrauma in particular has benefited from the substantial increase in speed with the use of MDCT. The option of performing a single fast, comprehensive and highly reliable examination with MDCT moves CT into the foremost position in trauma diagnostics for the first time. The whole emergency radiological diagnostic procedure can be done on the CT table. It is almost always unnecessary for patients to be relocated and moved for any further examinations, e. g. angiography.     

Future generation CT imaging

X-ray CT technology has been available for more than 30 years, yet continued technological advances have kept CT imaging at the forefront of medical imaging innovation. Consequently, the number of clinical CT applications has increased steadily. Other imaging modalities might be superior to CT imaging for some specific applications, but no other single modality is more often used in chest imaging today. Future technological developments in the area of high-resolution detectors, high-capacity x-ray tubes, advanced reconstruction algorithms, and improved visualization techniques will continue to expand the imaging capability. Future CT imaging technology will combine improved imaging capability with advanced and specific computer-assisted tools, which will expand the usefulness of CT imaging in many areas.     

CT and stone fragility

Informed selection of treatment requires knowledge of the size and composition of a calculus. Spiral CT has a growing role in the detection of calculi, with an overall accuracy in excess of 95%. Moreover, the margin of error in determining stone size does not exceed 3.6%, and stone volume is underestimated by <5%. Pixelograms, the compilation of multiple points of attenuation, may provide clues to stone composition and durility.     

The timing of CT

There were 276 patients with severe head injuries admitted to the Neurosurgical Clinic of the A.H.E.P.A University Hospital during the last two years. Comatose state, dilated pupils without reaction to light and respiration disturbances (Glasgow Score 7) were the main characteristic state in 60% of the patients. Computed Tomography (CT) helped determine the diagnosis and decide the further care of our cases. The appearance of delayed hematomas, three intracerebral and one extradural, was noted 48 hours after injury.Because of these cases we stress the value of a CT-scan, it s timing and discuss briefly the literature regarding the pathophysiology of delayed hematomas.     

PET/CT Fusion Scan Enhances CT Staging in Patients with Pancreatic Neoplasms

Background  The role of fusion positron emission tomography/computed tomography scans (PET/CT) in staging of patients with pancreatic neoplasms (PN) is poorly defined. PET/CT may serve as an adjunct to standard imaging by increasing occult metastases detection. The purpose of this study was to assess the additional value, in relation to computed tomography (CT), of PET/CT imaging for patients with PN. Methods  Eighty-two patients with potentially resectable PN underwent staging with PET/CT and CT of the chest and abdomen. Sensitivity of diagnosing pancreatic cancer by PET/CT avidity was evaluated. The sensitivity of detecting metastases was compared between PET/CT, standard CT, and the combination of PET/CT and CT. The impact of PET/CT on patient management was estimated by calculating the percentage of patients whose treatment plan was altered due to PET/CT. Results  The sensitivity and specificity of PET/CT in diagnosing pancreatic cancer were 89% and 88%, respectively. Sensitivity of detecting metastatic disease for PET/CT alone, standard CT alone, and the combination of PET/CT and CT were 61%, 57%, and 87%, respectively. Findings on PET/CT influenced the clinical management in seven patients (11%), two with a supraclavicular lymph node (LN), two occult liver lesions, two peritoneal implants, and one peri-esophageal LN. Conclusion  This study evaluated PET/CT in the initial work-up of patients with PN. PET/CT increased sensitivity (87%) for detection of metastatic disease when combined with standard CT. In invasive cancer, PET/CT changed the management in 11% of our patients. PET/CT should be considered in the initial work-up of patients with potentially resectable pancreatic lesions.     

逆行性膀胱增强CT扫描与顺行性增强CT扫描的ROC曲线比较分析

目的比较分析逆行性膀胱增强CT扫描与顺行性膀胱增强CT的关系.方法逆行性膀胱增强CT80例,顺行性膀胱CT50例.研究采用双盲法对图像进行诊断分析.两种方法的数据结果进行等级分类并应用先进的ROC曲线对资料进行统计处理.结果逆行法与顺行法POC曲线下面积分别为0.99±0.013和0.96±0.026,逆行法在图像质量上和诊断水平上优于顺行法﹙(P＜0.05).结论逆行法简单易行,随到随做,不需要禁食和试敏.逆行法最长用时不超过15min.而顺行法要超过1.5h.逆行法拓宽了适应症.对过敏和尿失禁者也可应用.逆行法在体外可控制膀胱内浓度,图像较顺行法清晰可靠,没有分层,节省时间,降低成本.     

PET/CT与低剂量CT诊断T1期肺癌

FDG-PET/CT对于T1期肺癌N期与M期病灶诊断优于普通CT,但受CT衰减校正(CT attenuation-correc-ted,CTAC)数据采集与重建模式影响与早期肺癌糖代谢低的特点,T1期(直径≤3 cm,实性、部分实性、非实性)原发灶检出与定性比较困难。肺部低剂量CT(low dose CT,LDCT)可以弥补前者缺点。通过改进数据采集重建模式,使CTAC图像质量达到LDCT质量要求或对高危患者追加肺部LDCT,制定合理随访计划,配合肿瘤标志物检查,发挥功能影像和解剖影像相结合,无创与微创方法相结合的优势,使其对T1期肺癌诊断的定位、定性、定量、定期与预后判断更准确。     

CT能谱单能量成像用于提高脑血管CTA成像质量

目的探讨CT能谱单能量图像对提高脑血管CTA成像质量的价值。方法回顾性分析53例接受脑血管能谱CTA检查的患者,获得5组单能量图像(50、70、90、110、130keV)、1组质量控制(QC)图像。分别测定6组图像的噪声、CNR,并对图像质量进行评分。采用单因素方差分析比较6组图像的CNR及噪声差异,组间两两比较采用LSD-t检验;采用多组独立样本秩和检验(Kruskal-Wallis H)比较图像质量评分差异。结果 6组中,70keV组与90keV组图像噪声差异无统计学意义(P0.05),其余各组间两两比较差异均有统计学意义(P均0.05);6组图像CNR、图像质量评分两两比较差异均有统计学意义(P均0.05),50keV单能量图CNR、图像质量评分均最高,70keV单能量图、QC图及90、110、130keV单能量图的CNR、图像评分均依次递减。结论能谱CT 50keV单能量图像能显著提高脑血管CTA的图像质量,值得临床推广应用。