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1.
目的探讨心率对16层螺旋CT冠状动脉造影图像质量的影响及其重建相位窗的优选。方法本文收集接受16层螺旋CT冠状动脉造影(MSCTCA)检查者69例,按心率分成小于60次/min、61~65次/min、66~70次/min和大于70次/min共四个组,将冠状动脉图像质量根据冠状动脉伪影多少及血管连续性分为0~3分四个等级,评价不同心率对重建图像质量的影响,并分别优选出各组显示不同冠状动脉节段的最佳相位窗。结果第1组至第4组左冠状动脉及其分支的检查成功率分别为95%、93.3%、83.3%和50%,右侧冠状动脉分别为90%、93.3%、77.8%和50%。第3组和第4组间所有冠状动脉节段的成功率均有统计学差异(P<0.05)。第1组所有冠状动脉节段均以75%相位窗显示最佳;第2组显示两侧冠状动脉以75%为最佳显示相位窗者均占80%(12/15);第3组中左、右冠状动脉以75%为最佳显示相位窗者分别占72.2%和55.5%,右侧冠状动脉以45%为最佳显示相位窗者占33.3%;第4组病例显示左侧、右侧冠状动脉的最佳相位窗分布较分散,分别在75%~95%和35%~45%。结论对于16层螺旋CT来说,心率低于70次/min时冠状动脉检查可获得较高的检查成功率。心率低于65次/min时,两侧冠状动脉的最佳显示相位窗通常为75%;心率超过65次/min,尤其超过70次/min时,应选择35%~45%和75%~95%两个节段的多相位窗重建。  相似文献
2.
目的探讨心率对16层螺旋CT冠状动脉造影最佳重建相位窗及图像质量的影响.方法 90例受检者行16层螺旋CT回顾性心电门控条件下冠状动脉造影,对原始数据进行R-R间期75%及10%~90%(间隔10%)多个时相重建,按心率≤65 bpm和>65 bpm分为2组,图像质量分为3级.结果第1组图像质量为Ⅰ级的冠脉比率 (82.2%)显著高于第2组 (47.4%),Ⅲ级者则相反 (5.3%和22.4%).两组中图像质量为Ⅲ级的冠脉共计45支,占总数的12.5%.LAD、LCx和RCA在75% 相位窗显示最佳者居多,随心率增加,75% 相位窗显示最佳者减少(第1、2组分别为92.3%和61.4%).15支冠状动脉在不同相位窗重建互相弥补.结论对于大多数心率≤65 bpm者,各支冠状动脉能同时在75%相位窗最佳显示;最佳重建相位窗和互补相位窗的选择可提高冠脉的显示率.  相似文献
3.
目的对低心率、高心率和心律不齐患者采用前瞻性心电门控单心动周期冠状动脉CTA,比较图像质量差异及其影响因素。方法采用256排宽探测器CT对208例患者行前瞻性心电门控单心动周期冠状动脉CTA检查,不使用药物控制心率;其中低心率组87例(心率≤70次/分),高心率组38例(心率70次/分),心律不齐组83例(5个心动周期内的心率变化10次/分)。常规重建相位为75%或45%;以多时相重建中运动伪影最小者为最优相位。采用单变量线性回归评估影响图像质量评分的因素。结果 105例(105/208,50.48%)最优相位与常规相位不同。最优相位图像中,3组图像质量评分、SNR和CNR差异均无统计学意义(P均0.05)。线性回归显示,心脏相位和伪影类型是图像质量评分的影响因素(P均0.001)。结论在不限制心率的前瞻性心电门控宽探测器冠状动脉CTA中,高心率或心律不齐并非影响图像质量的重要因素。  相似文献
4.
目的评价将iDose4迭代重建(IR)技术用于胸部低剂量增强扫描的可行性。方法选取71例体质量指数(BMI)正常(18.5≤BMI〈25.0kg/m2)且接受胸部CT增强扫描的患者,随机分为A组(120kVp,100 mAs)、B组(80kVp,100mAs)、C组(120kVp,50mAs),分别采用iDose4 IR技术和FBP进行重建,记录各组的噪声、SNR、CNR和有效剂量(ED)。按1~3分评价各组总体图像质量,并对3组结果进行比较。结果比较同一个患者的FBP和IR图像,IR技术明显降低了图像的噪声,提高了图像的SNR、CNR。B、C组IR后的图像噪声、SNR和CNR与A组FBP图像比较差异均无统计学意义(P均〉0.05)。B、C组IR后的图像总体质量与A组FBP重建图像质量差异无统计学意义(P〉0.05)。结论运用IR技术进行低剂量胸部CT增强扫描可获得满足诊断要求的图像。  相似文献
5.
Direct coronal CT scanning can be efficiently performed by a new co-table equipment, which requires a comfortable prone positioning of the patient, whereby the patient must only extend his head slightly. The co-tableunit is linked to the original CT table board directly within a few minutes, coming through the opening of the gantry from the rear. This practical co-table method serves to reduce motion artifacts and to improve image quality significantly. By this method coronal follow-up CT scans are exactly reproducable.  相似文献
6.
Lower peripheral quantitative computed tomography (pQCT)-derived leg muscle density has been associated with fragility fractures in postmenopausal women. Limb movement during image acquisition may result in motion streaks in muscle that could dilute this relationship. This cross-sectional study examined a subset of women from the Canadian Multicentre Osteoporosis Study. pQCT leg scans were qualitatively graded (1–5) for motion severity. Muscle and motion streak were segmented using semi-automated (watershed) and fully automated (threshold-based) methods, computing area, and density. Binary logistic regression evaluated odds ratios (ORs) for fragility or all-cause fractures related to each of these measures with covariate adjustment. Among the 223 women examined (mean age: 72.7?±?7.1 years, body mass index: 26.30?±?4.97?kg/m2), muscle density was significantly lower after removing motion (p?<?0.001) for both methods. Motion streak areas segmented using the semi-automated method correlated better with visual motion grades (rho?=?0.90, p?<?0.01) compared to the fully automated method (rho?=?0.65, p?<?0.01). Although the analysis-reanalysis precision of motion streak area segmentation using the semi-automated method is above 5% error (6.44%), motion-corrected muscle density measures remained well within 2% analytical error. The effect of motion-correction on strengthening the association between muscle density and fragility fractures was significant when motion grade was?≥3 (p interaction <0.05). This observation was most dramatic for the semi-automated algorithm (OR: 1.62 [0.82,3.17] before to 2.19 [1.05,4.59] after correction). Although muscle density showed an overall association with all-cause fractures (OR: 1.49 [1.05,2.12]), the effect of motion-correction was again, most impactful within individuals with scans showing grade 3 or above motion. Correcting for motion in pQCT leg scans strengthened the relationship between muscle density and fragility fractures, particularly in scans with motion grades of 3 or above. Motion streaks are not confounders to the relationship between pQCT-derived leg muscle density and fractures, but may introduce heterogeneity in muscle density measurements, rendering associations with fractures to be weaker.  相似文献
7.

Background

Stable bearing devices are often utilized by prehospital first responders in modern management of severely injured patients. It is not known whether these devices influence radiation exposure or image quality in whole-body computed tomography (WBCT). Additionally, manufacturers currently provide no specifications concerning these criteria. This investigation analyzed the influence of nine different bearing devices on these specified criteria.

Methods

The influence of nine different bearing devices on radiation exposure and image quality in WBCT was investigated. The dose-length-product (DLP100) was obtained through use of a CT-ionisation chamber placed in the centre of a 32 cm CT-phantom and compared with a reference value. Moreover, the results were calculated as effective dose data E (mSv). The image quality was assessed by three expert radiologists using the following scoring scale (0 = no artefacts; 1 = minor artefacts; 2 = clearly artefacts; 3 = massive artefacts).

Results

Out of nine bearing devices examined, four showed significantly higher (2.5–4.5%, p < 0.05) DLP100 and five showed no significant difference between DLP100 and the reference value. The image quality was classified in the categories “0”, “1”, “2” and “3” in 4, 3, 1 and 1 case, respectively.

Conclusions

In diagnostic producers using WBCT, bearing devices may be associated with relevant increases in radiation dose and can affect the image assessability. Some bearing devices are associated with no significant influence on radiation dose and reduction of image quality. Considering all results to get the best balance between image quality and radiation dose, aluminium and metal-free devices should be preferred.  相似文献
8.
Pialat JB  Burghardt AJ  Sode M  Link TM  Majumdar S 《BONE》2012,50(1):111-118
Motion artifacts are a common finding during high-resolution peripheral quantitative computed tomography (HR-pQCT) image acquisitions. To date it is not clear (i) when to repeat an acquisition, (ii) when to exclude a motion-degraded dataset post hoc, and (iii) how motion induced artifacts impact measures of trabecular and cortical parameters. In this study we present inter- and intra-observer reproducibility of a qualitative image quality grading score and report the prevalence of repeat acquisitions in our population. Finally the errors in bone density and micro-architectural parameters estimated from repeat acquisitions with and without motion degradation are presented. The relationship between these errors and the image quality grade is evaluated for each parameter. Repeat acquisitions performed due to operator-observed motion in the reconstructed image occurred for 22.7% of the exams (29.7% radius, 15.7% tibia). Of this subset, 88 exams with repeat acquisitions had at least one acquisition graded 1 (best quality). In this subset, the percent differences in bone density and micro-architecture measures tended to increase as the relative image quality decreased. Micro-architectural parameters were more sensitive to motion compared to geometric and densitometric parameters. These results provide estimates of the error in bone quality measures due to motion artifacts and provide an initial framework for developing standardized quality control criteria for cross-sectional and longitudinal HR-pQCT studies.  相似文献
9.

Purpose

To compare metallic artifact reduction (MAR) algorithms proposed by four vendors according to the delivered dose and iterative level using a phantom study.

Methods

Four CT systems (Revolution GSI®, Ingenuity Elite®, Somatom Edge®, and Aquilion Prime®) equipped with MAR algorithms (Smart MAR®, O-MAR®, iMAR®, and SEMAR®) were compared. Acquisitions were performed with CIRS model 062M Phantom containing a titanium rod core insert using 120 kV and two dose levels (3 and 7 mGy). Images were reconstructed with and without MAR algorithms using standard “soft tissue” kernel for filtered back projection (FBP) and intermediary iterative level. Artifact propagation was assessed by counting the number of pixels containing a HU outside a defined threshold interval (> 100HU and < ?80 HU). Artifact correction was evaluated by computing the differences between images with and without MAR.

Results

Accuracy of NCT values increased significantly using MAR algorithms, IR, and high dose levels (P < 0.001). Image noise reduced ?31 ± 15 (SD) % (range: ?50%;?14%) with Smart-MAR®, ?28 ± 3 (SD) % (range ?31%; ?25%) with O-MAR®, ?32 ± 7 (SD) % (range: ?40%; ?24%) with iMARCN®, ?52 ± 8 (SD) % (range: ?60%; ?42%) with iMARTH® and ?29 ± 6 (SD) % (range: ?37%; ?23%) with SEMAR®. The number of pixels outside the threshold interval was also reduced using MAR algorithms. Each MAR algorithm corrected in distinct patterns, with satisfactory artifact correction for all MAR algorithms.

Conclusion

This study demonstrates that artifact correction using MAR algorithms differs according to the main manufacturers, although corrections are satisfactory for all systems. Corrections also improved by using IR and increasing the dose level.  相似文献
10.
目的探讨计算机X线摄影的正确曝光条件,在保证影像质量的情况下,降低被检者辐射剂量。方法利用konica 170 CR系统,选择胸部后前位、腰椎前后位、膝关节前后位3个摄影位置,60例患者分别以不同的KVP和mAs曝光,分析对比影像质量。结果适当的高KVP(90~105)摄影,可以降低X线曝光量3.57~5.00倍,影像质量无差异。结论 CR高KVP摄影,降低X线曝光量,降低被检者辐射剂量。  相似文献
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