Reproducibility of Abdominal Aortic Aneurysm Diameter Measurement and Growth Evaluation on Axial and Multiplanar Computed Tomography Reformations

Purpose

To compare different methods measuring abdominal aortic aneurysm (AAA) maximal diameter (Dmax) and its progression on multidetector computed tomography (MDCT) scan.

Materials and Methods

Forty AAA patients with two MDCT scans acquired at different times (baseline and follow-up) were included. Three observers measured AAA diameters by seven different methods: on axial images (anteroposterior, transverse, maximal, and short-axis views) and on multiplanar reformation (MPR) images (coronal, sagittal, and orthogonal views). Diameter measurement and progression were compared over time for the seven methods. Reproducibility of measurement methods was assessed by intraclass correlation coefficient (ICC) and Bland–Altman analysis.

Results

Dmax, as measured on axial slices at baseline and follow-up (FU) MDCTs, was greater than that measured using the orthogonal method (p?=?0.046 for baseline and 0.028 for FU), whereas Dmax measured with the orthogonal method was greater those using all other measurement methods (p-value range: <0.0001–0.03) but anteroposterior diameter (p?=?0.18 baseline and 0.10 FU). The greatest interobserver ICCs were obtained for the orthogonal and transverse methods (0.972) at baseline and for the orthogonal and sagittal MPR images at FU (0.973 and 0.977). Interobserver ICC of the orthogonal method to document AAA progression was greater (ICC?=?0.833) than measurements taken on axial images (ICC?=?0.662–0.780) and single-plane MPR images (0.772–0.817).

Conclusion

AAA Dmax measured on MDCT axial slices overestimates aneurysm size. Diameter as measured by the orthogonal method is more reproducible, especially to document AAA progression.     

Sonographic surveillance of abdominal aortic aneurysms: what is the smallest change in measured diameter that reliably reflects aneurysm growth?

OBJECTIVE: The decision to repair an abdominal aortic aneurysm may be based on an apparent increase in aneurysm diameter seen in successive sonographic examinations. However, true aneurysm growth can be diagnosed only if the measured increase in aneurysm diameter exceeds the variability inherent in the measurement. This study uses analysis of variance to determine the smallest change between 2 successive, independent sonographic measurements of aneurysm diameter that reliably indicates aneurysm growth. METHODS: Pairs of independent observers examined 63 patients with abdominal aortic aneurysms. Each observer obtained a sonographic measurement of the anteroposterior aneurysm diameter in the transaxial and longitudinal scan planes, and the transverse aneurysm diameter in the transaxial scan plane. Analysis of variance yielded the total variance associated with each type of measurement as well as the contributions made by variance among aneurysms, variance between observers and residual variance. These components were used to estimate interobserver standard error of measurement, interobserver reliability and the smallest measurement change needed to diagnose true aneurysm growth. RESULTS: Differences among aneurysms made the largest contribution to overall variance. Interobserver reliability was excellent, ranging from 0.89 to 0.94 (with perfect reliability being 1.00). The smallest difference between 2 successive, independent anteroposterior diameter measurements that indicated aneurysm growth at the 95% confidence level was 0.78 cm in the transaxial scan plane and 0.92 cm in the longitudinal scan plane. The smallest difference between 2 successive, independent transverse diameter measurements that indicated aneurysm growth at the same confidence level was 1.05 cm. CONCLUSION: Despite high interobserver reliability, only changes in measured aneurysm diameter greater than or equal to 0.78 cm indicate aneurysm growth at the 95% confidence level. Smaller changes in measured diameter may not be real, but due to variability in measurement.     

Standardized volume rendering for magnetic resonance angiography measurements in the abdominal aorta

Purpose: To compare three methods for standardizing volume rendering technique (VRT) protocols by studying aortic diameter measurements in magnetic resonance angiography (MRA) datasets.

Material and Methods: Datasets from 20 patients previously examined with gadolinium-enhanced MRA and with digital subtraction angiography (DSA) for abdominal aortic aneurysm were retrospectively evaluated by three independent readers. The MRA datasets were viewed using VRT with three different standardized transfer functions: the percentile method (Pc-VRT), the maximum-likelihood method (ML-VRT), and the partial range histogram method (PRH-VRT). The aortic diameters obtained with these three methods were compared with freely chosen VRT parameters (F-VRT) and with maximum intensity projection (MIP) concerning inter-reader variability and agreement with the reference method DSA.

Results: F-VRT parameters and PRH-VRT gave significantly higher diameter values than DSA, whereas Pc-VRT gave significantly lower values than DSA. The highest interobserver variability was found for F-VRT parameters and MIP, and the lowest for Pc-VRT and PRH-VRT. All standardized VRT methods were significantly superior to both MIP and F-VRT in this respect. The agreement with DSA was best for PRH-VRT, which was the only method with a mean error below 1 mm and which also had the narrowest limits of agreement (95% of cases between 2.1 mm below and 3.1 mm above DSA).

Conclusion: All the standardized VRT methods compare favorably with MIP and VRT with freely selected parameters as regards interobserver variability. The partial range histogram method, although systematically overestimating vessel diameters, gives results closest to those of DSA.     

螺旋CT血管造影在腹主动脉瘤诊断中的应用

目的 :评价螺旋 CT血管造影 (SCTA)在腹主动脉瘤诊断中的价值。方法 :13例腹主动脉瘤病人行螺旋 CT增强扫描 ,后进行各种重建 :表面阴影显示 (SSD)、多平面重建 (MPR)、最大密度投影 (MIP)。结果 :SSD明确显示动脉瘤的范围和周围血管的关系 ;MPR对瘤体内附壁血栓范围的显示较佳 ;而 MIP对瘤壁的钙化及对管腔各段的精确测量颇有价值。结论 :螺旋 CT血管造影操作简单、安全、诊断明确 ,能帮助和指导手术 ,可取代 DSA对腹主动脉瘤的诊断     

电子束CT在主动脉瘤诊断中的临床应用

目的　评价电子束CT(electronbeamcomputedtomography ,EBCT)血管造影及三维重建在主动脉瘤诊断中的临床应用价值。方法　收集经EBCT诊断的主动脉瘤 3 2例 ,男 2 4例 ,女 8例 ,其中 9例与手术结果作了对照。胸主动脉扫描采用单层步进容积增强扫描序列 (SVS ) ,心电门控采像 ;腹主动脉扫描采用单层连续容积增强扫描序列 (CVS ) ,无心电门控。所得图像进行后处理三维重建 ,主要采用多层面重组法 (MPR )、最大密度投影法 (MIP )、表面阴影显示法 (SSD )、容积再现法 (VR )进行处理。结果　 3 2例主动脉瘤中 ,真性主动脉瘤 8例 ,假性动脉瘤 5例 ,夹层动脉瘤 19例。其中 9例动脉瘤接受手术治疗 ,手术证实EBCT诊断符合率为 10 0 %。结论　EBCT血管造影可获得高分辨率的大血管解剖影像 ,三维重建图像能直观地显示主动脉瘤病变的范围、大小形态及夹层动脉瘤内膜撕裂口 ,对诊断具有优良价值 ,并能指导手术。在主动脉瘤的诊断上 ,可取代常规血管造影。     

MSCT血管成像对腹主动脉瘤的诊断价值

目的:评价多层螺旋CT血管成像(MSCTA)在诊断腹主动脉瘤中的价值.方法:对31例经手术证实的腹主动脉瘤患者的MSCTA与数字减影血管造影(DSA)进行对照性研究.采用容积再现(VR)、最大密度投影(MIP)、多平面重组(MPR)、仿真内镜技术(VE)及表面遮盖显示(SSD)后处理方法.结果:MSCTA与DSA对腹主动脉瘤的诊断符合率达100%,对瘤体长度、近端瘤颈直径、近端瘤颈长度、近端瘤颈角度等参数的测量无明显差异,对瘤体直径的测量值差异有显著性,MSCTA测量值较DSA准确.结论:MSCTA可明确诊断腹主动脉瘤,对重要参数的测量值准确,可作为腹主动脉瘤诊断及术前评估的首选影像学检查方法.     

Maximum Diameter Measurements of Aortic Aneurysms on Axial CT Images After Endovascular Aneurysm Repair: Sufficient for Follow-up?

Purpose

To assess the accuracy of maximum diameter measurements of aortic aneurysms after endovascular aneurysm repair (EVAR) on axial computed tomographic (CT) images in comparison to maximum diameter measurements perpendicular to the intravascular centerline for follow-up by using three-dimensional (3D) volume measurements as the reference standard.

Materials and Methods

Forty-nine consecutive patients (73?±?7.5?years, range 51?C88?years), who underwent EVAR of an infrarenal aortic aneurysm were retrospectively included. Two blinded readers twice independently measured the maximum aneurysm diameter on axial CT images performed at discharge, and at 1 and 2?years after intervention. The maximum diameter perpendicular to the centerline was automatically measured. Volumes of the aortic aneurysms were calculated by dedicated semiautomated 3D segmentation software (3surgery, 3mensio, the Netherlands). Changes in diameter of 0.5?cm and in volume of 10% were considered clinically significant. Intra- and interobserver agreements were calculated by intraclass correlations (ICC) in a random effects analysis of variance. The two unidimensional measurement methods were correlated to the reference standard.

Results

Intra- and interobserver agreements for maximum aneurysm diameter measurements were excellent (ICC?=?0.98 and ICC?=?0.96, respectively). There was an excellent correlation between maximum aneurysm diameters measured on axial CT images and 3D volume measurements (r?=?0.93, P?r?=?0.93, P?Conclusion Measurements of maximum aneurysm diameters on axial CT images are an accurate, reliable, and robust method for follow-up after EVAR and can be used in daily routine.     

Contrast-bolus MR angiography of the transplanted kidney with a low-field (0.5-T) scanner: diagnostic accuracy, sensitivity and specificity of images and reconstructions in the evaluation of vascular complications

PURPOSE: This study was performed to assess the feasibility, interobserver variability, sensitivity, specificity and diagnostic accuracy of raw data and postprocessed images from a low-field (0.5-T) magnetic resonance (MR) unit in evaluating vascular complications of kidney grafts. MATERIALS AND METHODS: We enrolled 49 patients undergoing MR angiography (MRA) for a clinical suspicion of renal artery stenosis. The raw data, maximum intensity projections (MIP) and multiplanar reconstruction (MPR) image sets were evaluated independently. We calculated the number and degree of stenosis, and sensitivity, specificity and accuracy for MIP, MPR and raw data image sets, together with interobserver variability. RESULTS: Interobserver agreement was substantial. There were no differences among the MIP and MPR algorithms and raw data images for the detection of stenosis. Raw data images were more accurate in quantifying the severity of stenosis, with higher sensitivity (75% vs. 62.5%), equal specificity and higher diagnostic accuracy (75% vs. 71.43%). CONCLUSIONS: Contrast-enhanced MRA, even with a low-field (0.5-T) unit, is a feasible, sensitive and accurate technique for the study of the renal arteries of the transplanted kidney.     

CT after Endovascular Repair of Abdominal Aortic Aneurysms: Diagnostic Accuracy of Diameter Measurements for the Detection of Aneurysm Sac Enlargement

Purpose

To evaluate the diagnostic accuracy of diameter measurements for the detection of aneurysm volume increase during follow-up after endovascular aortic repair (EVAR) of abdominal aortic aneurysms (AAAs).

16层螺旋CT在血管病变诊断中的临床应用

目的评价16层螺旋CT血管造影(16SCTA)及重建技术在血管病变诊断中的临床应用价值。方法100例血管病变行16SCTA,采用准直0.75 mm,层厚1 mm,间隔0.5 mm。重建应用多平面重建(MPR),最大密度投影(M IP)及容积显示技术(VRT)。结果100例血管病变中65例经手术病理或DSA证实。100例病变中,8例脑动脉瘤,2例脑动静脉畸形,6例肺动静脉畸形,9例肺动脉栓塞伴下肢深静脉血栓,4例肺隔离症,20例冠状动脉软斑块和/或钙化,12例主动脉瘤,3例肾动脉狭窄,2例肠系膜上动脉血栓,1例股动脉狭窄,33例软组织血管瘤。这3种重建技术均能显示病变的大小、形态及范围,对病变可进行任意角度重建和观察,VRT可立体地显示病变。MPR和M IP可显示血栓,M IP和VRT显示钙化。结论综合应用16层螺旋CT的各种重建技术,能够全面而清晰地显示血管病变,可取代DSA,为患者提供一种安全可靠的诊断手段,对临床治疗具有重要指导意义。     

主动脉瘤多层螺旋CT血管成像的临床应用价值

目的探讨多层螺旋CT血管成像(MSCTA)技术在诊断主动脉瘤中的临床应用价值.资料与方法对32例主动脉瘤和主动脉夹层患者进行MSCTA检查,将原始图像传至工作站进行后处理,运用不同的重建方法对血管进行显示,包括多平面重组(MPR)、最大密度投影(MIP)、表面遮盖法(SSD)和容积再现(VR)技术.结果主动脉瘤13例,主动脉夹层19例,多种重建图像与轴位图像相结合能清晰地显示动脉瘤的解剖细节及其与周围器官的空间解剖关系.结论 MSCTA技术对主动脉瘤的诊断具有独特的优越性,对于选择治疗方法、观察术后疗效及随访具有重要价值.     

Reproducibility of magnetization transfer ratio histogram-derived measures of the brain in healthy volunteers

Using two MR scanners, we evaluated the intraobserver, interobserver, image-reimage, and interimager variabilities in the assessment of magnetization transfer ratio (MTR) histograms obtained monthly on four occasions from five healthy volunteers. With multiple observers, the mean coefficients of variations ranged from 2.2% to 8.2% for "pure" image-reimage variability, from 1.2% to 4.9% for interobserver variability, and from 2.1% to 4.9% for image-reimage variability. The mean intraobserver coefficients of variations were always lower than 1%. The mean coefficients of variations ranged from 10.2% to 14.6% for pure interimager variability and from 8.6% to 14.3% for interimager variability with multiple observers. Interimager variability accounted for 96.0% of the overall variability of average MTR, for 96.7% of peak location, and for 41.1% of the peak height. The use of different MR scanners is the main source of variability when obtaining MTR histograms.     

Observer variability in the sonographic measurement of renal length in childhood.

The intra- and interobserver variability of the measurement of renal length in an unselected series of children attending for renal tract ultrasound were estimated using a standard technique and test-retest protocol. The standard errors of measurement were calculated and the limits of agreement derived. The results indicate that for normal kidneys there is a 95% probability that a second measurement by one observer will be within 4.6 mm of his first reading. Similarly, a single measurement will be within 7.8 mm of a reading by a second examiner. For abnormal kidneys in this series the intraobserver variability was similar to normal kidneys but interobserver variability was greater. Observer error in the measurement of renal length is equivalent to between 2 and 3 years normal growth for children older than 1 year.     

MDCT interpretation of the ascending aorta with semiautomated measurement software: Improved reproducibility compared with manual techniques

BackgroundTreatment decisions for ascending aortic aneurysms are guided by measurements from CT angiograms.ObjectiveThe aim was to evaluate the reproducibility of these measurements by using manual techniques and advanced imaging software.MethodsTwo radiologists measured maximal ascending aorta diameter on CT angiograms in 30 subjects at 4 separate reading sessions—2 with manual techniques and 2 with semiautomated software analysis. Interobserver and intraobserver variabilities were assessed with Bland-Altman plots and Spearman correlation coefficients.ResultsInterobserver variability was smaller for the software-assisted method. Limits of agreement for the manual method were −4.2 mm and 9.2 mm compared with −4.0 mm and 4.6 mm for the software-assisted method; coefficients of repeatability were 6.8 mm and 4.3 mm. Intraobserver variability was inconsistent between readers. Strong correlation was found between observers who used both methods (R² = 0.8078–0.9881; P < .05 for all).ConclusionThe use of an advanced imaging software for measurement of ascending aortic aneurysm reduces interobserver variability.     

Automated quantification of aortoaortic and aortoiliac angulation for computed tomographic angiography of abdominal aortic aneurysms before endovascular repair: preliminary study

The degree of angulation of abdominal aortic aneurysms (AAAs) has emerged as an important factor in assessing eligibility for endovascular aneurysm repair (EVAR). The authors developed an automatic algorithm that reduces variability of measurement of aortoiliac angulation. For highly structured manual methods, intraobserver variability was 8.2 degrees ± 5.0 (31% ± 20) and interobserver variability was 5.6 degrees ± 2.5 (20% ± 9.1) compared with 0.6 degrees ± 0.8 (2.2% ± 3.6) (intraobserver) and 0.4 degrees ± 0.4 (1.4% ± 1.9) (interobserver) for the automatic algorithm (P < .01). In phantoms, the automatically measured angles were equivalent to reference values (P < .05). This algorithm was also faster than manual methods and has the potential to enhance the clinical utility and reliability of computed tomographic angiography for preoperative assessment for EVAR.     

电子束CT血管造影及三维重建在主动脉病变诊断中的临床应用

目的建立电子束ＣＴ血管造影（ＥＢＣＴ－Ａｎｇｉｏｇｒａｐｈｙ）常规扫描及三维重建方法，探讨其临床应用价值。材料与方法回顾分析了自１９９５年７月至１９９６年１２月经ＥＢＣＴ诊断的各种主动脉病变共１８９例，男１５２例，女３７例，其中６８例与手术结果作了对照。胸主动脉扫描采用单层增强扫描方法（ＳＳＭ），心电门控采像；腹主动脉扫描采用连续容积扫描方法（ＣＶＳ），无心电门控。三维重建方法采用表面阴影显示法（ＳＳＤ）、多层面或曲面重建法（ＭＰＲ／ＣＰＲ）及最大密度投影法（ＭＩＰ）。结果１８９例主动脉病变包括各型夹层动脉瘤９７例，真性动脉瘤２６例，假性动脉瘤８例，马凡综合征３９例，大动脉炎５例，各种先天性主动脉发育异常１４例。６８例与手术对照，ＥＢＣＴ诊断符合率为９７％。结论ＥＢＣＴ血管造影图像时间分辨率高，消除了呼吸及运动伪影，可以明确诊断各种主动脉病变；三维重建图像利于整体直观地显示病变，帮助明确诊断并指导手术；在主动脉病变的诊断方面，可望取代有创的常规血管造影。     

The Effect of Registration Surrogate and Patient Factors on the Interobserver Variability of Electronic Portal Image Guidance During Prostate Radiotherapy

Intraprostatic fiducial markers (IPM) and electronic portal imaging (EPI) are commonly used to identify and correct for prostate motion during radiotherapy. However, little data is available on the precision of this image-guidance technique. This study quantified impact of different registration surrogates and patient factors on the interobserver variability of manual EPI alignment during prostate radiotherapy. For 50 prostate radiotherapy patients previously implanted with 3 IPM, five observers manually aligned 150 pairs of orthogonal EPI to the reference digital reconstructed radiograph using Varian Vision EPI analysis software. Images were aligned using: Bony anatomy (BA), single mid-prostate IPM (SM); and 2 strategies using 3 IPM: center of mass (COM) and rotate & translate (R&T). Intraclass correlation coefficients (ICCs) were calculated to quantify interobserver variability. The absolute displacements measured using SM and R&T were compared with those using COM. The impact of patients' pelvic diameter and adjuvant hormone therapy on interobserver variability were also evaluated. Twelve thousand displacement values were collected for analysis. The maximum discrepancy between the 5 observers was >2 mm in 47% of measurements using BA, 5% using SM, 4% using R&T, and 3% using COM. Both of the 3 IPM alignment strategies demonstrated lower interobserver variability than the single IPM strategy (ICC 0.94–0.97 vs. 0.82–0.94). BA had the highest interobserver variability (ICC = 0.43–0.90). Pelvic diameter and hormone therapy had no discernible impact on interobserver variability. Compared with COM, the absolute displacements measured using the other IPM strategies were statistically different (p < 0.001), but 95% of the absolute magnitude of differences between the strategies were ≤1 mm. The high reproducibility among the observers demonstrated the precision of prostate localization using multiple IPM and EPI, which was not influenced by the patient factors studied. Bony anatomy displayed the highest interobserver variability of the 4 alignment, likely because of the limited EPI field-of-view. Alignment using more than one IPM is recommended to minimize interobserver variability.     

Magnetization-transfer histogram analysis of the cervical cord in patients with multiple sclerosis

BACKGROUND AND PURPOSE: Previous studies have failed to show significant correlations between the number and extent of T2 spinal cord lesions and the clinical status of multiple sclerosis (MS) patients. We evaluated 1) whether it is feasible to create magnetization transfer-ratio (MTR) histograms of the cervical cord in patients with MS by using two different acquisition schemes, and 2) whether cervical cord MTR histogram metrics were different from those of healthy control subjects and between MS patients with and without locomotor disability. METHODS: We obtained two sets of gradient-echo sequences with and without a saturation pulse from 90 MS patients and 20 sex- and age-matched healthy control subjects. One set consisted of 20 axial, contiguous slices with a thickness equal to 5 mm. The other set consisted of 17 sagittal slices with a thickness equal to 3 mm and an interslice gap equal to 0.3 mm. After image coregistration and removal of tissues around the cervical cord, MTR histograms were created. The average MTR, the peak height, and the peak position of the histograms were measured. All of these measurements were from the whole of the cervical cord, thus including both MS lesions and normal-appearing tissue. RESULTS: When comparing the MTR histograms obtained using axial, contiguous, 5-mm-thick slices, MS patients had significantly lower average cervical cord MTR and peak height than did control subjects. When comparing the MTR histograms obtained using sagittal, 3-mm-thick slices, MS patients also had significantly lower average cervical cord MTR and peak location than did control subjects. Patients with locomotor disability had significantly lower average cord MTR and peak location than those without. CONCLUSION: This study shows that it is feasible to obtain MTR histograms of the cervical cord from MS patients by using different acquisition schemes. Our results also suggest that the assessment of MS cervical cord damage, achieved using MTR histograms, may lead to a better understanding of the clinical manifestations of the disease.     

多层螺旋CT诊断主动脉瘤的价值探讨

目的:探讨多层螺旋CT及后处理技术诊断主动脉瘤的价值。方法:使用美国GElightspeed QX/I型多层螺旋CT(MSCT)对疑有或有主动脉疾病的21例患者行轴位容积扫描,扫描条件:120 kV、300 mA,5 mm准直,7.5 mm/sec进床速度,HQ或HS扫描模式。重建层厚2.5 mm,重建间隔1.25 mm。用MEDRAD ENVISION高压注射器,经静脉团注非离子型造影剂100 ml,注射流率为2.8-3.5 ml/s。将横断面图像传至GE advantagewindows 4.0工作站进行二维和三维重建,包括多平面重建(MPR)、最大密度投影(MIP)、表面遮盖法重建(SSD)、容积再现(VR)、CT、仿真内窥镜重建(CTVE)及电影分析成像。结果:21例中主动脉瘤6例,主动脉夹层13例,其中Ⅰ型4例,Ⅱ型1例,Ⅲ型8例,马凡氏综合征2例。13例主动脉夹层在轴位图像均可见高密度的真腔和假腔,真腔小而密度略高于假腔,真假两腔之间的低密度弧型影为撕破的内膜。MIP、CTVE重建发现6例主动脉夹层破口,附壁血栓6例,发现主动脉外壁溃疡破口2例,主动脉内膜钙化并内移>5 mm7例。结论:MSCT成像技术作为一种非创伤性的血管成像方法,具有安全、可靠的优越性。