Flat-panel-detector-based volumetric CT: performance evaluation of imaging for skeletal structures of small animals in comparison to multislice CT

OBJECTIVES: The aim of this study was to compare the image performance of silicon-based flat-panel-detector-based volumetric computed tomography (fpVCT) to multislice spiral computed tomography (MSCT) for the visualization and detail detectability of skeletal structures in rodents of different development stages. MATERIALS AND METHODS: Rodents of different development stages were imaged with fpVCT (GE prototype with circular gantry with two 1024 x 1024, 200-microm pixel size, amorphous silicon/Cesium lodid (Csl) flat-panel detector) and eight-slice MSCT (LightSpeed Ultra). Imaging parameters (80 kVp, 100 mA) and the position of the rodents were identical in both techniques. Image quality, detail detectability, and contour of skeletal structures were judged by two observers in consensus using a 4-point scale (1 = unsatisfactory...4 = good). Findings were displayed and evaluated in axial slices, multiplanar reconstructions (MPR), maximum intensity projections (MIP) and volume rendering technique (VRT) in both modalities. Mean and standard of error of mean were calculated. RESULTS: In axial slices, visualization and detail detectability of very subtle skeletal structures, e.g., the basis of the skull was better in fpVCT than in MSCT (4 vs. 2 points). The MPRs of fpVCT showed less artifacts and more details than those of the MSCT. The MIPs and VRTs of the fpVCT demonstrated best image quality in all rodents of different development stages, whereas MSCT showed significant artifacts. CONCLUSION: fpVCT outperformed MSCT in imaging of small rodents. Due to the truly isotropic volume data set with high spatial resolution, fpVCT is a powerful tool in evaluating detailed skeletal structures.     

上半规管裂综合征的多层螺旋CT诊断

目的 探讨上半规管裂综合征的MSCT表现特点,进一步提高对该病的认识.方法 回顾性分析8例经临床和手术诊断为上半规管裂综合征患者的临床和MSCT资料,分析总结其位置、大小等CT表现,尤其是MPR图像特点.结果 8例患者MPR重组的上半规管最大层面图像均显示了上半规管壁的部分骨质缺损,其顶壁均未见气化,其中有6例发生在顶壁的正中部(4例还涉及顶前部),2例发生在顶壁的后部;其缺损的最大径为0.8～4.2mm,中位数为2.4mm.结论 高分辨率MSCT扫描结合MPR技术在上半规管裂综合征患者的影像诊断中具有较大的价值.     

上半规管裂综合征的多层螺旋CT诊断

目的 探讨上半规管裂综合征的MSCT表现特点,进一步提高对该病的认识.方法 回顾性分析8例经临床和手术诊断为上半规管裂综合征患者的临床和MSCT资料,分析总结其位置、大小等CT表现,尤其是MPR图像特点.结果 8例患者MPR重组的上半规管最大层面图像均显示了上半规管壁的部分骨质缺损,其顶壁均未见气化,其中有6例发生在顶壁的正中部(4例还涉及顶前部),2例发生在顶壁的后部;其缺损的最大径为0.8～4.2mm,中位数为2.4mm.结论 高分辨率MSCT扫描结合MPR技术在上半规管裂综合征患者的影像诊断中具有较大的价值.     

Experimental flat-panel high-spatial-resolution volume CT of the temporal bone

BACKGROUND AND PURPOSE: A CT scanner employing a digital flat-panel detector is capable of very high spatial resolution as compared with a multi-section CT (MSCT) scanner. Our purpose was to determine how well a prototypical volume CT (VCT) scanner with a flat-panel detector system defines fine structures in temporal bone. METHODS: Four partially manipulated temporal-bone specimens were imaged by use of a prototypical cone-beam VCT scanner with a flat-panel detector system at an isometric resolution of 150 microm at the isocenter. These specimens were also depicted by state-of-the-art multisection CT (MSCT). Forty-two structures imaged by both scanners were qualitatively assessed and rated, and scores assigned to VCT findings were compared with those of MSCT. RESULTS: Qualitative assessment of anatomic structures, lesions, cochlear implants, and middle-ear hearing aids indicated that image quality was significantly better with VCT (P < .001). Structures near the spatial-resolution limit of MSCT (e.g., bony covering of the tympanic segment of the facial canal, the incudo-stapedial joint, the proximal vestibular aqueduct, the interscalar septum, and the modiolus) had higher contrast and less partial-volume effect with VCT. CONCLUSION: The flat-panel prototype provides better definition of fine osseous structures of temporal bone than that of currently available MSCT scanners. This study provides impetus for further research in increasing spatial resolution beyond that offered by the current state-of-the-art scanners.     

MSCT胸部低剂量扫描对慢性肺部病变的应用研究

目的:比较低剂量及常规剂量扫描对慢性肺部弥漫性病变(范围较广泛者)的显示差异,探讨低剂量扫描诊 断慢性弥漫性或浸润性肺部病变的可行性及合理扫描方案。方法:34例慢性肺部病变患者及4例临床怀疑支气管扩张但 CT扫描未见异常的患者,行低剂量(50mAs)全肺螺旋扫描,14例患者并行常规剂量(195mAs)全肺增强扫描,所有病例 在病变部位加低剂量(50mAs)及常规剂量(220mAs)薄层(2.5mm)HRCT扫描。比较低剂量及常规剂量扫描对病变范 围、分布及病变特征的显示差异。结果:两种剂量全肺扫描(重建层厚7.5mm)图像对肺部病变分布的范围及各种征象的 显示差异无显著性意义(P>0.05);两种剂量的薄层HRCT图像对各种病变征象均可以显示,但是对支气管扩张、蜂窝样 改变、纤维索条及胸膜下线的显示以常规剂量为优(P<0.05),对其它征象的显示两组剂量差异无显著性意义(P> 0.05)。结论:对于怀疑肺弥漫性病变的患者,可以采用低剂量全肺扫描,病变部位加常规剂量薄层HRCT扫描。     

Investigations on an isolated skull with gunshot wounds using flat-panel CT

The use of computed tomography (CT) scanners is rapidly becoming established in forensic medicine. Current multislice CT (MSCT) scanners attain a resolution of 0.42 mm. An isolated skull with gunshot injuries was examined with a high-resolution eXplore Locus Ultra flat-panel CT (eLU-CT) and MSCT. Structures and minute fissures in the bone interior, which were neither visible macroscopically nor with the MSCT data, could be imaged with the eLU-CT data. In addition, a tiny interior impact defect from a retained missile could be detected by eLU-CT, which clearly aided the reconstruction of the gunshots in this case.     

Flat panel detector-based volumetric computed tomography (fpVCT): performance evaluation of volumetric methods by using different phantoms in comparison to 64-multislice computed tomography

OBJECTIVES: Evaluation of a silicon-based flat panel volumetric computed tomography (fpVCT) and multislice CT in terms of volumetry of phantoms with different algorithms. Furthermore, to compare the different volumetric analysis methods themselves. MATERIALS AND METHODS: Four phantoms of different materials have been scanned with fpVCT (GE prototype with circular gantry with 2 aSi/CsI flat panel detector) and a 64-slice spiral CT (MSCT: LightSpeed VCT). Three spherical phantoms of different materials and 1 phantom with an irregular shape were evaluated. True volumes were calculated in dependence from the diameter or by water displacement method. Imaging parameters (80 kVp, 100 mA) and the position of the phantoms were identical in both techniques. After reconstruction of the images different algorithms have been used 4 times for each phantom. These analysis methods have been performed: Region growing, threshold method, planimetry, 3-dimensional volumetry measurement by using the equation of an ellipsoid (ellipse) and an advanced lung analysis modus [single advanced lung analysis (ALA)]. The mean values and the standard deviations have been evaluated and compared with the true volumes. RESULTS: In all phantoms fpVCT showed better results with lower deviations from the true values than in MSCT, especially for small volumes of the phantoms. However, the results of the ALA single method demonstrated no significant difference between the fpVCT and MSCT. The comparison of the different analysis methods revealed that 3-dimensional measurement with the ellipse method was the worst method for volume estimation, especially for the irregularly formed phantom. CONCLUSION: fpVCT was superior to MSCT in the volumetry of small objects. The ellipse method has been shown to be the worst for volumetry with the highest relative deviations from the true volume value. The single ALA method shows the lowest standard deviation thereby revealing a reproducible volumetric method for small nodules. However, further future developments of volumetric analysis methods are necessary to use them accurately in daily routine. Due to the truly isotropic volume data set with high spatial resolution fpVCT is a powerful tool for the volumetry of small nodules.     

CT扫描薄层骨算法重建对颅底骨折的诊断价值

目的对比CT常规扫描与薄层骨算法重建扫描在颅底骨折诊断中的作用。方法对80例外伤性颅底骨折进行回顾性对比分析。所有检查均采用SOMATOMAR或GEHispeedNX/iProCT扫描机,均先行头颅CT常规扫描,层厚层距均为10mm,再行薄层颅底扫描骨算法重建,层厚层距均为1mm～3mm。结果80例颅脑外伤均有颅底骨折的临床体征,但头颅CT常规扫描仅有23例显示骨折线,而薄层骨算法重建扫描颅底80例均见明确骨折线,其中19例见多发骨折。并且对中颅窝、前颅窝极不容易直接显示骨折的部分区域也可清楚显示。同时可更清楚地显示出筛窦、蝶窦、及乳突气房内积液情况。结论薄层颅底扫描骨算法重建明显优于头颅CT常规扫描,它可以明确显示颅底骨质损伤情况,为临床诊断提供可靠而客观的影像学资料。     

Electrocardiographic assistance in multidetector CT of thoracic disorders

ECG-synchronized multislice spiral CT (MSCT) allows a significant reduction of cardiac motion artefacts and as a result a virtually artefact-free display of intrathoracic structures. With their advantages in imaging geometry and continuous spiral image acquisition multislice CT scanners provide superior image quality and spatial resolution in these patients. Possible clinical applications for ECG assistance in MSCT include CT angiography of the coronary arteries, functional cardiac CT imaging and imaging of the cardiac valves, CT angiography of the aorta or pulmonary vascular tree as well as ECG-gated imaging of the lung parenchyma. Prospective ECG triggering and retrospectively ECG-gated image reconstruction comprise the technical corsage for reduction of pulsation artefacts in cardiac and other thoracic CT applications. In addition the development of time-optimised reconstruction algorithms for retrospective cardiac gating in 8- and 16 slice spiral CT scanners have enabled further improvements in temporal resolution. This overview describes the technique, its clinical indications and the merits of electrocardiographic assistance in MSCT of chest disorders.     

Radiation exposure in multi-slice versus single-slice spiral CT: results of a nationwide survey

Multi-slice (MS) technology increases the efficacy of CT procedures and offers new promising applications. The expanding use of MSCT, however, may result in an increase in both frequency of procedures and levels of patient exposure. It was, therefore, the aim of this study to gain an overview of MSCT examinations conducted in Germany in 2001. All MSCT facilities were requested to provide information about 14 standard examinations with respect to scan parameters and frequency. Based on this data, dosimetric quantities were estimated using an experimentally validated formalism. Results are compared with those of a previous survey for single-slice (SS) spiral CT scanners. According to the data provided for 39 dual- and 73 quad-slice systems, the average annual number of patients examined at MSCT is markedly higher than that examined at SSCT scanners (5500 vs 3500). The average effective dose to patients was changed from 7.4 mSv at single-slice to 5.5 mSv and 8.1 mSv at dual- and quad-slice scanners, respectively. There is a considerable potential for dose reduction at quad-slice systems by an optimisation of scan protocols and better education of the personnel. To avoid an increase in the collective effective dose from CT procedures, a clear medical justification is required in each case.     

MSCT在鼻咽癌颅底骨侵犯的应用价值

目的：分析鼻咽癌颅底侵犯MSCT诊断价值。方法分析经病理证实28例鼻咽癌患者MSCT影像资料,比较多平面重组（ MPR）与横断面图像对颅底侵犯的检出情况。结果 MSCT多平面重组（ MPR）显示25例颅底侵犯,横断面图像显示19例。横断面表现主要为骨质破坏和颅底孔道增宽,而MPR除骨质改变外,还能清楚显示颅底侵犯的范围。结论 MSCT可精确显示鼻咽癌颅内侵犯的部位、途径及范围,有助于临床分期及指导放疗野的设置。     

Validation of a Monte Carlo tool for patient-specific dose simulations in multi-slice computed tomography

Estimating the dose delivered to the patient in X-ray computed tomography (CT) examinations is not a trivial task. Monte Carlo (MC) methods appear to be the method of choice to assess the 3D dose distribution. The purpose of this work was to extend an existing MC-based tool to account for arbitrary scanners and scan protocols such as multi-slice CT (MSCT) scanners and to validate the tool in homogeneous and heterogeneous phantoms. The tool was validated by measurements on MSCT scanners for different scan protocols under known conditions. Quantitative CT Dose Index (CTDI) measurements were performed in cylindrical CTDI phantoms and in anthropomorphic thorax phantoms of various sizes; dose profiles were measured with thermoluminescent dosimeters (TLD) in the CTDI phantoms and compared with the computed dose profiles. The in-plane dose distributions were simulated and compared with TLD measurements in an Alderson-Rando phantom. The calculated dose values were generally within 10% of measurements for all phantoms and all investigated conditions. Three-dimensional dose distributions can be accurately calculated with the MC tool for arbitrary scanners and protocols including tube current modulation schemes. The use of the tool has meanwhile also been extended to further scanners and to flat-detector CT.     

前颅凹底脑膜瘤的影像诊断与病理对照研究

目的:探讨前颅凹底脑膜瘤的影像学和病理组织学之间的关系.材料和方法:病理证实的前颅凹底脑膜瘤27例,男8例,女19例.年龄13～79岁,平均62岁.均行MRI检查(增强16例);15例行CT检查(增强8例).分析CT、MRI影像,并与手术病理对照.结果:27例前颅凹底脑膜瘤,起源于嗅沟15例,前颅凹底6例,眶顶4例,鞍结节向前生长2例.多数水肿明显,均匀增强;少数不均匀增强,并出现脑膜尾征,少数伴钙化、坏死、囊变和出血.累及邻近颅骨时引起骨质增生.结论:前颅凹底脑膜瘤具有典型的影像学表现.CT和MRI具有诊断价值,MRI优于CT ,但CT观察钙化和骨质改变优于MRI.     

Musculoskeletal applications of flat-panel volume CT

Flat-panel volume computed tomography (fpVCT) is a recent development in imaging. We discuss some of the musculoskeletal applications of a high-resolution flat-panel CT scanner. FpVCT has four main advantages over conventional multidetector computed tomography (MDCT): high-resolution imaging; volumetric coverage; dynamic imaging; omni-scanning. The overall effective dose of fpVCT is comparable to that of MDCT scanning. Although current fpVCT technology has higher spatial resolution, its contrast resolution is slightly lower than that of MDCT (5-10HU vs. 1-3HU respectively). We discuss the efficacy and potential utility of fpVCT in various applications related to musculoskeletal radiology and review some novel applications for pediatric bones, soft tissues, tumor perfusion, and imaging of tissue-engineered bone growth. We further discuss high-resolution CT and omni-scanning (combines fluoroscopic and tomographic imaging).     

汶川大地震颅脑损伤概况及多层螺旋CT的诊断价值

目的 总结汶川大地震颅脑损伤情况及多层螺旋CT的诊断价值.方法 对收治的汶川地震伤员1557例中因颅脑外伤的292例进行CT检查,其中CT检查阳性者225例.回顾性总结225例颅脑损伤患者的损伤类型及多层螺旋CT表现,分析多平面重组(MPR)及三维(3D)重组成像的应用价值.结果 颅脑损伤225例,主要包括颅骨骨折66例,脑挫裂伤50例,颅内血肿55例,蛛网膜下腔出血16例,硬膜下积液16例,头皮异物20例,外伤性脑梗死2例.其中22例进行了手术治疗.结论 地震住院救治伤员中颅脑损伤占的比例较大,MPR及3D图像可以为神经外科医师术前提供直观可靠的依据.     

CT机质量控制检测的探讨

目的:CT机质量控制检测方法的探讨及应用。方法:用美国模体实验室的Catphan 500模体和瑞典奥利科公司的Solidose 400剂量仪检测CT机扫描架的定位光精度、扫描床运动精度、层厚、CT值线性、视野均匀性、噪声、高对比度分辨率、低对比度分辨率和CT剂量指数(CTDI)。结果:所检测CT机作为整机均合格,但部分指标不合格。结论:通过对噪声、CT线性、对比度分辨率等图像性能参数的检测,可有效保证系统性能良好和维持最优化的图像质量;对CTDI的检测,可及时了解辐射危险水平,进而优化扫描方案,在保证诊断的前提下降低病人受照剂量。     

Comparison of the sensitivities of 5 different computed tomography scanners for the assessment of the progression of pulmonary emphysema: a phantom study

RATIONALE AND OBJECTIVES: To compare the sensitivities of 5 different computed tomography scanners (4 multislice CT [MSCT] and 1 single-slice CT) in the assessment of the progression of pulmonary emphysema. METHODS: A Perspex cylinder phantom was constructed containing small pieces of polythene foam with densities representative of lung. Changing the cylinder's volume simulated subtle lung density changes. The sensitivity to density changes was defined by the variation in the residual errors from the linear regression line between time and density. RESULTS: The single-slice CT scanner was significantly less sensitive to density changes than MSCT scanners. Also, among MSCT scanners, small but significant differences were found when the standardized acquisition protocol was used. CONCLUSIONS: Considering the large sensitivity differences between single- and multislice CT scanners, we would recommended using MSCT scanners in clinical multicenter trials in emphysema. The protocol standardization of MSCT scanners can still be further improved.     

A comparative evaluation of Cone Beam Computed Tomography (CBCT) and Multi-Slice CT (MSCT): Part I. On subjective image quality

Aims

To compare image quality and visibility of anatomical structures in the mandible between five Cone Beam Computed Tomography (CBCT) scanners and one Multi-Slice CT (MSCT) system.

Materials and methods

One dry mandible was scanned with five CBCT scanners (Accuitomo 3D, i-CAT, NewTom 3G, Galileos, Scanora 3D) and one MSCT system (Somatom Sensation 16) using 13 different scan protocols. Visibility of 11 anatomical structures and overall image noise were compared between CBCT and MSCT. Five independent observers reviewed the CBCT and the MSCT images in the three orthographic planes (axial, sagittal and coronal) and assessed image quality on a five-point scale.

Results

Significant differences were found in the visibility of the different anatomical structures and image noise level between MSCT and CBCT and among the five CBCT systems (p = 0.0001). Delicate structures such as trabecular bone and periodontal ligament were significantly less visible and more variable among the systems in comparison with other anatomical structures (p = 0.0001). Visibility of relatively large structures such as mandibular canal and mental foramen was satisfactory for all devices. The Accuitomo system was superior to MSCT and all other CBCT systems in depicting anatomical structures while MSCT was superior to all other CBCT systems in terms of reduced image noise.

Conclusions

CBCT image quality is comparable or even superior to MSCT even though some variability exists among the different CBCT systems in depicting delicate structures. Considering the low radiation dose and high-resolution imaging, CBCT could be beneficial for dentomaxillofacial radiology.     

螺旋CT三维重建在颌面部外伤中的临床应用价值

目的探讨螺旋CT三维重建对颌面部外伤的诊断准确性。方法50例颌面部外伤患者均经螺旋CT扫描及三维重建。结果螺旋CT三维重建在显示颌面部骨折的类型、位置、范围、骨折的移位、塌陷深度等方面明显优于常规CT,特别是对一些复合的粉碎性骨折,SSD可以显示出畸形的立体形态。结论螺旋CT三维重建能立体、直观地显示颌面部的解剖及病理解剖关系,增加了影像的信息量,为制定临床治疗方案提供大量依据。     

Applications of positron emission tomography/computed tomography image fusion in clinical positron emission tomography-clinical use,interpretation methods,diagnostic improvements

Positron emission tomography (PET)/computed tomography (CT) scanners with combined dedicated high performance PET and CT scanners have been introduced recently in PET imaging. Oncological imaging with fluorodeoxyglucose (FDG) is currently the dominant application of PET. The addition of CT to PET offers many advantages, including obtaining a fast and relatively low-noise transmission scan, shortening the duration of the examination, adding precise anatomical information to FDG imaging, and providing additional diagnostic information. However, the use of CT for attenuation correction can lead to some artifacts that need to be considered when interpreting a PET/CT study: quantitative measurements may be altered, high density IV and oral and metallic objects may produce artifacts, and the registration of PET and CT may occasionally be suboptimal. Areas where using PET/CT offers particular potential advantages include the head and neck region, abdomen, and pelvis. Even in the thorax, PET/CT offers some advantages. Although clinical data evaluating the added value of PET/CT over PET are presently limited, preliminary results are very encouraging. More studies are warranted to clearly define the clinical impact of PET/CT over PET; however, it is clear this dedicated fusion technology will be very important for patient imaging in the coming years.