Low-dose computed tomography with 4th-generation iterative reconstruction algorithm in assessment of oncologic patients

AIM To compare radiation dose and image quality of lowdose computed tomography(CT) protocol combined with hybrid-iterative reconstruction algorithm with standarddose CT examinations for follow-up of oncologic patients. METHODS Fifty-one patients with known malignant diseases which underwent, during clinical follow-up, both standarddose and low-dose whole-body CT scans were enrolled. Low-dose CT was performed on 256-row scanner, with 120 kV and automated m A modulation, and iterative reconstruction algorithm. Standard-dose CT was performed on 16-rows scanner, with 120 kV, 200-400 m As(depending on patient weight). We evaluated density values and signal-to-noise ratio, along with image noise(SD), sharpness and diagnostic quality with 4-point scale.RESULTS Density values in liver, spleen and aorta were higher in lowdose images(liver 112.55 HU vs 103.90 HU, P < 0.001), as SD values in liver and spleen(liver 16.81 vs 14.41). Volumetric-Computed-Tomographic-Dose-Index(CTDIvol) and Dose-Length-Product(DLP) were significantly lower in low-dose CT as compared to standard-dose(DLP 1025.6 m Gy*cm vs 1429.2 m Gy*cm, P < 0.001) with overall dose reduction of 28.9%. Qualitative analysis did not reveal significant differences in image noise and diagnostic quality.CONCLUSION Automatic tube-current modulation combined with hybriditerative algorithm allows radiation dose reduction of 28.9% without loss of diagnostic quality, being useful in reducing dose exposure in oncologic patients.

Quantitative evaluation of deep convolutional neural network-based image denoising for low-dose computed tomography

To minimize radiation risk,dose reduction is important in the diagnostic and therapeutic applications of computed tomography(CT).However,image noise degrades image quality owing to the reduced X-ray dose and a possible unacceptably reduced diagnostic performance.Deep learning approaches with convolutional neural networks(CNNs)have been proposed for natural image denoising;however,these approaches might introduce image blurring or loss of original gradients.The aim of this study was to compare the dose-dependent properties of a CNN-based denoising method for low-dose CT with those of other noise-reduction methods on unique CT noise-simulation images.To simulate a low-dose CT image,a Poisson noise distribution was introduced to normal-dose images while convoluting the CT unit-specific modulation transfer function.An abdominal CT of 100 images obtained from a public database was adopted,and simulated dose-reduction images were created from the original dose at equal 10-step dose-reduction intervals with a final dose of 1/100.These images were denoised using the denoising network structure of CNN(DnCNN)as the general CNN model and for transfer learning.To evaluate the image quality,image similarities determined by the structural similarity index(SSIM)and peak signal-to-noise ratio(PSNR)were calculated for the denoised images.Significantly better denoising,in terms of SSIM and PSNR,was achieved by the DnCNN than by other image denoising methods,especially at the ultra-low-dose levels used to generate the 10%and 5%dose-equivalent images.Moreover,the developed CNN model can eliminate noise and maintain image sharpness at these dose levels and improve SSIM by approximately 10%from that of the original method.In contrast,under small dose-reduction conditions,this model also led to excessive smoothing of the images.In quantitative evaluations,the CNN denoising method improved the low-dose CT and prevented over-smoothing by tailoring the CNN model.

Evaluation with low-dose dual-phase helical computed tomography of patients with thyroid lesions

Background The incidence of thyroid cancer has been increasing.Our aim was to evaluate the efficacy of low-dose dualphase helical computed tomography （CT） in the characterization of thyroid lesions,and to discuss the relationship between image characteristics and their pathology.Methods One hundred and six patients with thyroid lesions underwent low-dose dual-phase helical CT after the injection of contrast material.CT scans were obtained at arterial and venous phase with delays of 25 and 65 seconds,and tube current of 60 and 120 mA,respectively.The attenuation change in the lesion between the arterial and venous phase was analyzed and categorized as ＂increased,＂ ＂decreased,＂ ＂mixed＂ or ＂no change.＂ Results Histopathologic diagnosis was obtained by surgery in 106 patients （115 lesions）.Of the 106 patients,45 had nodular goiter,5 thyroid adenoma,6 thyroiditis,and 50 papillary thyroid carcinoma （PTC） （59 lesions）.The attenuation value showed a significant difference （P ＜0.05） between the arterial and venous phase for the high attenuation area.There was statistical significant difference in terms of attenuation value in high attenuation areas at both phases and in low attenuation areas on arterial phase between nodular goiter and PTC （P ＜0.05）.However,there was no significant difference in attenuation value between adenoma and PTC.Twenty-nine cases （76.3％） of goiter manifested mixed type,3 cases （3/5） of adenoma showed decreased type,6 cases （6/6） of thyroiditis showed increased type,and 55 cases （93.2％） of PTC showed decreased type attenuation.The sensitivity,specificity for thyroid carcinoma by dual-phase CT were 94.9％ and 80.4％ respectively.The overall diagnostic accuracy for thyroid lesions by dual-phase CT was 87.8％.Conclusions The performance of dual-phase helical CT is related to the pathological structure of the lesions.The analysis of enhancement patterns by using dual-phase helical CT will be helpful in the differential diagnosis of thyroid lesions.

Accuracy of baseline low-dose computed tomography lung cancer screening: a systematic review and meta-analysis

Background:Screening using low-dose computed tomography(LDCT)is a more effective approach and has the potential to detect lung cancer more accurately.We aimed to conduct a meta-analysis to estimate the accuracy of population-based screening studies primarily assessing baseline LDCT screening for lung cancer.Methods:MEDLINE,Excerpta Medica Database,and Web of Science were searched for articles published up to April 10,2022.According to the inclusion and exclusion criteria,the data of true positives,false-positives,false negatives,and true negatives in the screening test were extracted.Quality Assessment of Diagnostic Accuracy Studies-2 was used to evaluate the quality of the literature.A bivariate random effects model was used to estimate pooled sensitivity and specificity.The area under the curve(AUC)was calculated by using hierarchical summary receiver-operating characteristics analysis.Heterogeneity between studies was measured using the Higgins I 2 statistic,and publication bias was evaluated using a Deeks’funnel plot and linear regression test.Results:A total of 49 studies with 157,762 individuals were identified for the final qualitative synthesis;most of them were from Europe and America(38 studies),ten were from Asia,and one was from Oceania.The recruitment period was 1992 to 2018,and most of the subjects were 40 to 75 years old.The analysis showed that the AUC of lung cancer screening by LDCT was 0.98(95%CI:0.96-0.99),and the overall sensitivity and specificity were 0.97(95%CI:0.94-0.98)and 0.87(95%CI:0.82-0.91),respectively.The funnel plot and test results showed that there was no significant publication bias among the included studies.Conclusions:Baseline LDCT has high sensitivity and specificity as a screening technique for lung cancer.However,long-term follow-up of the whole study population(including those with a negative baseline screening result)should be performed to enhance the accuracy of LDCT screening.

Multiphase hepatic scans with multirow- detector helical CT in detection of hypervascular hepatocellular carcinoma

BACKGROUND: Multirow-detector helical CT (MDCT) allows faster Z-axis coverage and improves longitudinal re- solution to scan the entire liver. This study was to evaluate the value of multiphase hepatic CT scans using MDCT in diagnosing hypervascular hepatocellular carcinoma (HCC). METHODS: Multiphase hepatic CT scans in 40 patients were carried out with a Marconi Mx8000 MDCT scanner. The scans of early arterial phase (EAP), late arterial phase (LAP) and portal venous phase (PVP) were started at 21, 34 and 85 seconds after injection of contrast medium, re- spectively. The number of detected lesions was calculated in each phase. The density of the liver and tumor was great- er than 1 cm for HCC, and the density of the liver and tumor in each phase was statistically calculated. RESULTS: A total of 61 lesions were found in the 40 pa- tients , and lesions greater than 1 cm were seen in 47 cases. The density differences between the liver and tumor were statistically significant (P<0.05) at the LAP and EAP and between the LAP, EAP and PVP. In the 61 lesions, the de- tectability in the EAP, LAP and the double arterial phases (DAP) was 32%, 87%, and 94%, respectively. Significant difference was found between the LAP plus PVP and the EAP plus PVP; but no significant difference was observed between the DAP plus PVP and the LAP plus PVP. CONCLUSIONS: The utility of MDCT scan in the liver has optimized the protocol of arterial phase scan. MDCT is possible to scan the entire liver in a real arterial phase and it is very valuable in the detection of small HCC.

Low-Dose High-Pitch Cardiac CT to Evaluate Abnormal Pacemaker Lead Position

Displacement of a cardiac pacemaker lead or myocardial perforation by a lead is an infrequent complication of pacemaker implantation. While standard cardiac CT is useful for diagnosing such complications when routine examinations can not, the potential risks associated with exposure to the high doses of radiation used in CT are of concern. Here, we report three cases in which pacemaker lead displacement or myocardial perforation was definitively diagnosed by low-dose cardiac CT used in the high-pitch spiral mode, when other more routine examinations failed to suggest their occurrence. The mean dose of radiation used for definitively diagnosing the three patients was relatively low (2.19 mSv).

Use of low-dose computed tomography to assess pulmonary tuberculosis among healthcare workers in a tuberculosis hospital

Background:According to the World Health Organization,China is one of 22 countries with serious tuberculosis(TB)infections and one of the 27 countries with serious multidrug-resistant TB strains.Despite the decline of tuberculosis in the overall population,healthcare workers(HCWs)are still at a high risk of infection.Compared with high-income countries,the TB prevalence among HCWs is higher in low-and middle-income countries.Low-dose computed tomography(LDCT)is becoming more popular due to its superior sensitivity and lower radiation dose.However,there have been no reports about active pulmonary tuberculosis(PTB)among HCWs as assessed with LDCT.The purposes of this study were to examine PTB statuses in HCWs in hospitals specializing in TB treatment and explore the significance of the application of LDCT to these workers.Methods:This study retrospectively analysed the physical examination data of healthcare workers in the Beijing Chest Hospital from September 2012 to December 2015.Low-dose lung CT examinations were performed in all cases.The comparisons between active and inactive PTB according to the CT findings were made using the Pearson chi-square test or the Fisher’s exact test.Comparisons between the incidences of active PTB in high-risk areas and non-high-risk areas were performed using the Pearson chi-square test.Analyses of active PTB were performed according to different ages,numbers of years on the job,and the risks of the working areas.Active PTB as diagnosed by the LDCT examinations alone was compared with the final comprehensive diagnoses,and the sensitivity and positive predictive value were calculated.Results:A total of 1012 participants were included in this study.During the 4-year period of medical examinations,active PTB was found in 19 cases,and inactive PTB was found in 109 cases.The prevalence of active PTB in the participants was 1.24%,0.67%,0.81%,and 0.53%for years 2012 to 2015.The corresponding incidences of active PTB among the tuberculosis hospital participants were 0.86%,0.41%,0.54%,and 0.26%.Most HCWs with active TB(78.9%,15/19)worked in the high-risk areas of the hospital.There was a significant difference in the incidences of active PTB between the HCWs who worked in the high-risk and non-high-risk areas(odds ratio[OR],14.415;95%confidence interval(CI):4.733-43.896).Comparisons of the CT signs between the active and inactive groups via chi-square tests revealed that the tree-in-bud,cavity,fibrous shadow,and calcification signs exhibited significant differences(P=0.000,0.021,0.001,and 0.024,respectively).Tree-in-bud and cavity opacities suggest active pulmonary tuberculosis,whereas fibrous shadow and calcification opacities are the main features of inactive pulmonary tuberculosis.Comparison with the final comprehensive diagnoses revealed that the sensitivity and positive predictive value of the diagnoses of active PTB based on LDCT alone were 100%and 86.4%,respectively.Conclusions:Healthcare workers in tuberculosis hospitals are a high-risk group for active PTB.Yearly LDCT examinations of such high-risk groups are feasible and necessary.

The accuracy and optimal slice thickness of multislice helical computed tomography for right and left ventricular volume measurement

Background Multislice helical computed tomography (MSCT) has been used to depict coronary anatomy noninvasively, and proved useful for evaluating ventricular function. The aim of our study was to assess the accuracy of ventricular volume as measured by MSCT.Methods Fourteen human left ventricular (LV) and 15 right ventricular (RV) casts were scanned by MSCT. A series of LV and RV short-axis images were reconstructed later with slice thickness of 2.0 mm, 3.5 mm, 5.0 mm, 7.0 mm, and 10.0 mm. Ventricular volume was calculated by the multislice tomographic Simpson’s method. True LV and RV cast volumes were determined by water displacement. Results Both calculated LV and RV volumes correlated highly with the corresponding true volumes (all r>0.95, P<0.01). But with slice thickness from 2.0 mm to 10.0 mm, MSCT scanning overestimated the corresponding true volume by (3.21±5.95) ml to (12.58±8.56) ml for LV and (10.22±8.45) ml to (23.91±12.24) ml for RV (all P<0.01). There was a very high correlation between the overestimation and the selected slice thickness for both LV and RV volume measurements (r=0.998 and 0.996, P<0.01, respectively). However, when slice thickness was reduced to 5.0 mm, the overestimation for both LV and RV volume measurements became nonsignificant for slice thickness from 2.0 mm to 5.0 mm. Conclusions Both LV and RV volumes can be accurately estimated by MSCT. Thinner slice has more accurate calculated volume. However, 5.0 mm slice thickness is thin enough for an accurate measurement of LV or RV volume.

A NONLOCAL KRONECKER-BASIS-REPRESENTATION METHOD FOR LOW-DOSE CT SINOGRAM RECOVERY

Low-dose computed tomography(LDCT)contains the mixed noise of Poisson and Gaus-sian,which makes the image reconstruction a challenging task.In order to describe the statistical characteristics of the mixed noise,we adopt the sinogram preprocessing as a stan-dard maximum a posteriori(MAP).Based on the fact that the sinogram of LDCT has non-local self-similarity property,it exhibits low-rank characteristics.The conventional way of solving the low-rank problem is implemented in matrix forms,and ignores the correlations among similar patch groups.To avoid this issue,we make use of a nonlocal Kronecker-Basis-Representation(KBR)method to depict the low-rank problem.A new denoising model,which consists of the sinogram preprocessing for data fidelity and the nonlocal KBR term,is developed in this work.The proposed denoising model can better illustrate the generative mechanism of the mixed noise and the prior knowledge of the LDCT.Nu-merical results show that the proposed denoising model outperforms the state-of-the-art algorithms in terms of peak-signal-to-noise ratio(PSNR),feature similarity(FSIM),and normalized mean square error(NMSE).

Assessment of the efficacy of reduced-radiation noncontrast computed tomography scan compared with the standard noncontrast computed tomography scan for detecting urolithiasis:A prospective single-center study

Background:Noncontrast computed tomography(CT)scan of the kidneys,ureter and bladder is the standard investigative modality for diagnosing and following up patients with urolithiasis.With each scan,a patient receives radiation of 18-34 mGy.Dose considerations become pertinent because of a 10%lifetime incidence rate and higher than 50%risk of recurrence,necessitating repeated imaging in the lifetime of a stone former.Hence,this study aimed to assess the sensitivity of"reduced-radiation"CT imaging by altering scan settings to lower than the"standard"norms.Materials and methods:Altogether,222 patients(255"kidney-ureter"stone-bearing units or"renal units")with urolithiasis and patients undergoing CT for other reasons with incidental findings of renal/ureteric calculi between 2017 and 2019 were included.All patients were subjected to 3 sequential scans at tube current settings of 250 mA(CT-N/Standard),100 mA(CT-100),and 50 mA(CT-50)at a constant voltage of 120 kV.Their clinicodemographic and radiological findings were recorded and assessed for significance.Results:Of the 255 renal units,117 were between 30 and 44 years of age,75%were men.Of the 255 patients,178(70.1%)reported a first stone episode and 77 had recurrence.Lower ureteric calculi were predominant(40.4%).All calculi were identified on CT-N;CT-100 failed to detect calculi in 1 patient,and CT-50 failed in 3 patients,where all calculi were<3 mm in size.Meanwhile,none were undetected among patients with obesity.The sensitivity was 99.61%for the CT-100 and 98.82%for the CT-50,which indicated a 2.5 and 5 times lower radiation and dose/length,respectively,than CT-N.Conclusions:The reduced-radiation CT scan is safe,sensitive,and accurate for the diagnosis and follow-up of patients with urolithiasis with significantly lower radiation exposures.Our study lays the foundation to accept low-dose CT in general and CT-50 in particular,as the new"standard of care,"and attempt further dose reduction without loss of diagnostic efficacy.

非增强螺旋CT扫描对急性阑尾炎的诊断价值

目的 评价非增强螺旋CT扫描对急性阑尾炎的诊断价值。资料与方法 对 115例临床怀疑急性阑尾炎患者作非增强螺旋CT扫描 ,不口服或结肠内灌注对比剂 ,层厚 10mm ,Pitch 1,扫描范围从L3 椎体至耻骨联合。CT诊断急性阑尾炎的标准包括阑尾增粗横径超过 6mm ,或阑尾结石同时伴有阑尾周围的炎性改变。CT诊断结果与手术、病理或临床随访结果进行对照。结果 CT发现 5 6例真阳性 ,49例真阴性 ,7例假阴性和 3例假阳性。CT诊断急性阑尾炎的敏感性为 89%,特异性为 94%,准确性为 91%,阳性预测值为 95 %,阴性预测值为 88%。 49例无阑尾炎患者中 ,CT发现其他病变 2 2例 (45 %)。结论 非增强螺旋CT扫描 ,能快速、准确地诊断有无急性阑尾炎 ,而且还能发现除阑尾炎以外的其他各种病变。

多发伤早期救治中64层螺旋CT的应用

目的探讨64层螺旋CT在多发伤早期救治中的作用。方法回顾性分析2006年1月至2007年10月间救治的284例多发伤,男性232例,女性52例;平均年龄34.5岁。头颈伤54例,面部伤35例,胸部伤125例,腹部伤112例,骨盆及四肢伤104例,体表伤254例。合并休克103例。ISS10～54分,平均16.3分。37例因伤情过重直接送入手术室,247例到院后3h内64层螺旋CT检查。结果螺旋CT检查时间8.4min。21例初检时有漏诊。急诊手术154例,其中启动绿色通道74例,非手术治疗130例。治愈272例(95.8%);死亡12例(4.2%)。结论多发伤早期救治中应用64层螺旋CT有助于缩短院内术前时间,提高早期确诊率和救治水平。

64排螺旋CT血管造影与3D-DSA在颅内动脉瘤诊断中的对比研究

目的探讨64排螺旋CT血管造影(CTA)、三维数字减影血管造影(3D-DSA)在颅内动脉瘤诊断中的应用价值。方法回顾性分析39例颅内动脉瘤患者的64排螺旋CTA、3D-DSA和手术资料,以手术为标准判定CTA和3D-DSA的临床诊断价值。结果 39例患者共发现44个动脉瘤,其中35例为单个动脉瘤,3例为2个动脉瘤,1例为3个动脉瘤。动脉瘤直径最小2.2mm,最大直径27mm。3D-DSA检出动脉瘤44个,与手术结果一致。3D-DSA能清晰显示所有动脉瘤的位置、大小、形态以及瘤颈宽度、瘤顶指向,发现动脉瘤的敏感性、特异性均为100%。64排螺旋CTA检出动脉瘤43个,漏诊1个,假阳性1个,64排螺旋CTA所显示的动脉瘤的位置、大小、形态及与周围结构关系与手术治疗所见一致,对动脉瘤的敏感性、特异性分别为97.7%和97.4%。结论 64排螺旋CTA诊断颅内动脉瘤有较高准确性,绝大部分动脉瘤性蛛网膜下腔出血的患者可以直接依据64排螺旋CTA结果进行手术治疗,在指导动脉瘤治疗方面可对3D-DSA起到重要补充作用。

64排螺旋CT血管造影对颅内动脉瘤手术的指导价值

目的探讨64排螺旋CT血管造影(CTA)对开颅夹闭术治疗颅内动脉瘤的临床指导价值。方法依据CTA检查结果,对56例颅内动脉瘤的患者行动脉瘤夹闭术。CTA扫描层厚0.625mm,后处理技术包括多层面重建(MPR)、表面遮盖三维重建(3-SSD)、容积显示重建(VR)、最大密度投影重建(MIP)。对照手术结果,评估CTA对颅内动脉瘤诊断和手术的指导价值。结果CTA共发现56例58个动脉瘤,手术共夹闭56个动脉瘤。①手术中发现动脉瘤的位置与CTA检查结果完全一致,符合率为100%。②术中有5个动脉瘤瘤体无法完全暴露,其余51个动脉瘤瘤体形态术中观察结果与CTA结果完全吻合,其中24个椭圆形、19个圆形动脉瘤的瘤顶指向与手术发现完全吻合。③CTA对动脉瘤与主要分支动脉关系的检测结果与手术观察完全吻合,其中49个动脉瘤瘤颈与分支动脉无关,7个动脉瘤瘤颈累及分支动脉。④CTA共发现21个动脉瘤瘤体有泡状突起,其中术中证实15个突起部位即为动脉瘤破裂部位,6个未发现破裂口。⑤CTA检测的动脉瘤瘤颈平均直径为(5.92±0.86)mm;术中测量平均为(6.13±1.06)mm。⑥所有动脉瘤瘤颈宽度的检测,CTA与手术结果差异无统计学意义(P>0.05)结论64排螺旋CTA能清晰显示动脉瘤的瘤体大小、瘤颈、瘤顶指向、载瘤动脉及动脉瘤与邻近血管和骨性组织间的空间关系,诊断颅内动脉瘤有较高的准确性,对制定动脉瘤的治疗方案有重要的指导价值。

多层螺旋CT对结肠癌术前淋巴结转移诊断价值的研究

目的探讨多层螺旋CT(MSCT)诊断结肠癌术前腹腔淋巴结转移的价值。方法回顾性分析2015年3月—2017年1月间在我院经手术病理确诊为结肠癌的58例病人的临床及影像资料,其中男32例,女26例;年龄31～78岁,平均(49.58±14.28)岁。对术前MSCT检测到的腹腔可疑转移淋巴结进行分析,分别以淋巴结短径、相对强化值及综合上述2种参数等作为判定淋巴结转移的标准,并采用Kappa检验对MSCT诊断及术后病理结果的一致性进行分析。结果与病理结果对照分析后发现,以淋巴结短径≥8 mm、相对强化值≥50 HU及短径≥5 mm且相对强化值≥30 HU作为判断淋巴结转移的标准时MSCT诊断与病理结果一致性相对较好(κ分别为0.809、0.764、0.786)。在不同的腹腔淋巴结分布区域,上述3种诊断标准用于肠旁淋巴结组时,诊断结果与病理结果的一致性较好(κ分别为0.816、0.802、0.800),用在肠系膜中及肠系膜根部淋巴结组时,诊断结果与病理结果的一致性中等(κ分别为0.631、0.673、0.574及0.527、0.626、0.502)。结论 MSCT可根据淋巴结大小、强化差值等参数对结肠癌病人术前淋巴结转移做出判断,从而为评估临床预后提供重要信息。

颞下颌关节CT影像测量与解剖测量相关性研究

目的:探讨颞下颌关节(temporom and ibu lar joint,TM J)形态的多排螺旋CT(mu ltislice helical computed tomo-graphy,MSCT)影像测量与解剖测量的相关关系。方法:MSCT对4具成人和4具儿童尸体TM J扫描,经多层面后重建处理,对反映TM J形态的参数进行测量,并在标本上进行相应部位相应参数测量,两者测量结果进行相关性分析。结果:有关TM J骨性部分的参数两种测量结果间有非常显著的正相关关系,关节盘厚度的测量,两种方法间有较大的正相关关系。结论:可以利用MSCT对TM J形态进行定性和定量研究。

周围型肺癌胸膜凹陷征的螺旋CT表现

目的：研究周围型肺癌时胸膜凹陷征的螺旋CT表现。材料和方法：收集经手术、病理证实的周围型肺癌62例，根据周围型肺癌的生长部位，总结其胸膜凹陷的不同螺旋CT表现，分析其形成的原因。结果：根据肿瘤发生的部位及其与胸膜结构的解剖位置关系将周围型肺癌的胸膜凹陷征分为3种主要表现：①线条状高密度影，近胜层胸膜面处见小三角形影；②典型表现，横断面上呈一组有一定形态变化规律的胸膜皱缩征象，在三维SSD重建图像上形象地显示了上述脏层胸膜的凹陷改变；③水平裂和斜裂胸膜凹陷，表现为不光滑的曲线状。结论：螺旋CT尤3D重建利于显示周围型肺癌时胸膜凹陷征。

CT灌注成像在肝脏结节性病变鉴别诊断中的应用价值

目的:探讨CT灌注成像在肝脏结节性病变鉴别诊断中的应用价值。方法:采用16层螺旋CT对肝细胞癌(hepa-tocellular carcinomas,HCC)25例、肝转移瘤(hepatic metastastes,HM)19例和肝血管瘤(hemoangiomas,HA)6例进行灌注扫描,分别计算其肝动脉灌注量(hepatic arterial perfusion,HAP)、肝门静脉灌注量(hepatic portal perfusion,HPP)、总肝灌注量(totalliver perfusion,TLP)和肝动脉灌注指数(hepatic arterial perfusion index,HAPI),并进行对比分析。结果:HCC、HM和HA组各CT灌注参数具有显著性差异。结论:CT灌注成像在肝结节性病变的鉴别诊断中具有重要的应用价值。

螺旋CT图像常见伪影的分析和处理

目的研究螺旋CT成像中常见伪影的产生原因与处理方法,以减少螺旋CT检查时产生的伪影,提高图像质量,为临床提供良好的影像资料。方法收集本院156位患者不同类型和不同程度CT图像伪影病例,进行系统性分析,其中头颈部扫描61例,胸部扫描37例,腹部扫描33例,盆腔扫描15例,其它部位10例。结果针对螺旋CT常见伪影产生的机理和成因进行了分析,给出了避免、抑制以及消除基于物理结构、基于患者本身、基于扫描系统和基于重建方法四类不同图像伪影的处理方法。结论螺旋CT成像中伪影产生受多种因素影响,利用各种技术有效避免、抑制或消除图像伪影,对优化图像质量和提高临床医学诊断质量和效率具有重要意义。