Comparison of volume and diameter measurement in assessing small abdominal aortic aneurysm expansion examined using computed tomographic angiography

Aim

First we aimed to assess the reproducibility of a computer tomography angiography (CTA) based technique for measuring infra-renal aortic volume and diameter. Second we sought to investigate whether changes in aortic volume and diameter were similar during follow-up.

Materials and methods

A prospective series of 57 patients, with aortic diameter initially measuring between 25 and 55 mm, were assessed with 2 CTAs a median of 14 months apart. Aortic volume and maximum diameter (both axial and orthogonal) were measured by a semi-automated workstation protocol based on previously defined techniques. Intra- and inter-observer reproducibility were assessed by repeat assessment of the initial CTA images of the first 33 patients included in the study, in order to estimate the 95% limits of agreements. Changes in aortic dimensions between the first and follow-up CTA, were defined for volume and diameter separately as changes greater than their respective 95% limits of agreement.

Results

Reproducibility of aortic volume and diameter was excellent with an average coefficient of variation <4%. The median (inter-quartile range) increases in total volume, orthogonal and axial diameters were 4.9 cm³ (0.01-14.18), 1.2 mm (0.40-3.50) and 1.4 mm (−0.15 to 3.55) respectively. Forty-two percent of patients who had increased aortic volume above the 95% limit of agreement did not display corresponding axial or orthogonal diameter changes.

Conclusions

Infra-renal total aortic volume, axial and orthogonal diameter can all be measured reproducibly from CTA. Aortic volume changes are not always reflected by similar changes in diameter and therefore provide complementary information when assessing AAA expansion over time.     

On the effect of computed tomography resolution to distinguish between abdominal aortic aneurysm wall tissue and calcification: A proof of concept

PurposeThe purpose of this study is to determine the optimal target CT spatial resolution for accurately imaging abdominal aortic aneurysm (AAA) wall characteristics, distinguishing between tissue and calcification components, for an accurate assessment of rupture risk.Materials and methodsRuptured and non-ruptured AAA-wall samples were acquired from eight patients undergoing open surgical aneurysm repair upon institutional review board approval and informed consent was obtained from all patients. Physical measurements of AAA-wall cross-section were made using scanning electron microscopy. Samples were scanned using high resolution micro-CT scanning. A resolution range of 15.5–155 μm was used to quantify the influence of decreasing resolution on wall area measurements, in terms of tissue and calcification. A statistical comparison between the reference resolution (15.5 μm) and multi-detector CT resolution (744 μm) was also made.ResultsElectron microscopy examination of ruptured AAAs revealed extremely thin outer tissue structure <200 μm in radial distribution which is supporting the aneurysm wall along with large areas of adjacent medial calcifications far greater in area than the tissue layer. The spatial resolution of 155 μm is a significant predictor of the reference AAA-wall tissue and calcification area measurements (r = 0.850; p < 0.001; r = 0.999; p < 0.001 respectively). The tissue and calcification area at 155 μm is correct within 8.8% ± 1.86 and 26.13% ± 9.40 respectively with sensitivity of 87.17% when compared to the reference.ConclusionThe inclusion of AAA-wall measurements, through the use of high resolution-CT will elucidate the variations in AAA-wall tissue and calcification distributions across the wall which may help to leverage an improved assessment of AAA rupture risk.     

Utility of screening computed tomography of chest, abdomen and pelvis in patients after heart transplantation

Introduction

Malignancy is a late cause of mortality in heart transplant recipients. It is unknown if screening computed tomography scan would lead to early detection of such malignancies or serious vascular anomalies post heart transplantation.

Methods

This is a single center observational study of patients undergoing surveillance computed tomography of chest, abdomen and pelvis atleast 5 years after transplantation. Abnormal findings, included pulmonary nodules, lymphadenopathy and intra-thoracic and intra-abdominal masses and vascular anomalies such as abdominal aortic aneurysm. The clinical follow up of each of these major abnormal findings is summarized.

Results

A total of 63 patients underwent computed tomography scan of chest, abdomen and pelvis at least 5 years after transplantation. Of these, 54 (86%) were male and 9 (14%) were female. Mean age was 52 ± 9.2 years. Computed tomography revealed 1 lung cancer (squamous cell) only. Non specific pulmonary nodules were seen in 6 patients (9.5%). The most common incidental finding was abdominal aortic aneurysms (N = 6 (9.5%)), which necessitated follow up computed tomography (N = 5) or surgery (N = 1). Mean time to detection of abdominal aortic aneurysms from transplantation was 14.6 ± 4.2 years. Mean age at the time of detection of abdominal aortic aneurysms was 74.5 ± 3.2 years.

Conclusion

Screening computed tomography scan in patients 5 years from transplantation revealed only one malignancy but lead to increased detection of abdominal aortic aneurysms. Thus the utility is low in terms of detection of malignancy. Based on this study we do not recommend routine computed tomography post heart transplantation.     

Multi-detector computed tomography of acute abdomen

Acute abdominal pain is one of the most common causes for referrals to the emergency department. The sudden onset of severe abdominal pain characterising the acute abdomen requires rapid and accurate identification of a potentially life-threatening abdominal pathology to provide a timely referral to the appropriate physician. While the physical examination and laboratory investigations are often non-specific, computed tomography (CT) has evolved as the first-line imaging modality in patients with an acute abdomen. Because the new multi-detector CT (MDCT) scanner generations provide increased speed, greater volume coverage and thinner slices, the acceptance of CT for abdominal imaging has increased rapidly. The goal of this article is to discuss the role of MDCT in the diagnostic work-up of acute abdominal pain.     

Long-term computed tomography follow-up after open surgical repair of abdominal aortic aneurysms

Purpose: To describe the findings on computed tomography (CT) of the aortic sac (AS) in patients operated on for abdominal aortic aneurysm (AAA) with insertion of a coated Dacron prosthesis.

Material and Methods: A prospective study of 36 consecutive patients operated on for AAA over 2 years and followed longitudinally with CT for up to 10 years.

Results: All patients had a fluid-filled AS on CT 7-10 days postoperatively. At 6 months, the AS had decreased in most patients, mainly in the antero-posterior diameter, and in two had disappeared completely. In five patients with complications, the AS increased in size. The AS disappeared completely at 10 years' follow-up in 13 patients. When present, a retroperitoneal hematoma always disappeared after 6 months.

Conclusion: These data indicate that the AS after graft implantation will diminish gradually but will persist for at least 6 months. Usually the transverse diameter is bigger than the antero-posterior diameter. If the AS enlarges and becomes rounded and distended with an inhomogeneous interior, it might be a sign of graft infection. In these cases an ultrasound-guided or CT-guided puncture is recommended.     

Radiologic features and anatomic basis of atypical clinical presentations of ruptured abdominal aortic aneurysms

Ruptured abdominal aortic aneurysms (AAAs) occasionally manifest with atypical clinical presentations and can be initially misdiagnosed. Symptoms are attributable either to local mass effect from the aneurysm or a contained rupture, or to the particular cavity or anatomic space into which an aneurysm bleeds. Radiologic studies obtained in this patient population often will demonstrate signs of the ruptured AAA, and these signs should be actively searched for when a ruptured AAA can be in the differential diagnosis. Emergent computed tomographic examination is indicated to confirm any clinical or radiologic suspicion of a ruptured abdominal aortic aneurysm, provided that the patient remains hemodynamically stable. The anatomic basis for a ruptured AAA presenting clinically as renal colic is discussed and illustrated, and the spectrum of clinical presentations of ruptured AAAs is reviewed.     

国产覆膜支架介入治疗腹主动脉瘤的实验研究

 目的建立10只犬腹主动脉瘤模型,以介入法置入国产覆膜支架,观察其改变.方法10只实验动物建立模型;国产覆膜支架治疗后,CT进行影像学复查;最后取病理检查.结果两只发生并发症,余犬治疗后管腔通畅,但局部管腔有狭窄,病理电镜示覆膜支架内有内皮细胞生长.结论国产覆膜支架介入治疗腹主动脉瘤安全、有效.     

Measurement and determinants of infrarenal aortic thrombus volume

Intra-luminal thrombus has been suggested to play a role in the progression of abdominal aortic aneurysm (AAA). The aims of this study were twofold. Firstly, to assess the reproducibility of a computer tomography (CT)-based technique for measurement of aortic thrombus volume. Secondly, to examine the determinants of infrarenal aortic thrombus volume in a cohort of patients with aortic dilatation. A consecutive series of 75 patients assessed by CT angiography with maximum aortic diameter >/=25 mm were recruited. Intra-luminal thrombus volume was measured by a semi-automated workstation protocol based on a previously defined technique to quantitate aortic calcification. Intra- and inter-observer reproducibility were assessed using correlation coefficients, coefficient of variation and Bland-Altman plots. Infrarenal aortic thrombus volume percentage was related to clinical, anatomical and blood characteristics of the patients using univariate and multivariate tests. Infrarenal aortic thrombus volume was related to the severity of aortic dilatation assessed by total aortic volume (r = 0.87, P < 0.0001) or maximum aortic diameter (r = 0.74, P < 0.0001). We therefore examined the clinical determinates of aortic thrombus expressed as a percentage of total aortic volume. Aortic thrombus percentage was negatively correlated with serum high density lipoprotein (HDL, r = -0.31). By ordinal multiple logistic regression analysis serum HDL below median (相似文献   

Multi-detector computed tomography in the diagnosis and management of acute aortic syndromes

Acute aortic syndrome (AAS) is a spectrum of conditions, which may ultimately progress to potentially life-threatening aortic rupture. This syndrome encompasses aortic dissection (AD), intramural haematoma, penetrating atherosclerotic ulcer and unstable thoracic aortic aneurysms. Multi-detector CT (MDCT) is crucial for the diagnosis of AAS, especially in the emergency setting due to its speed, accuracy and ready availability. This review attends to the value of appropriate imaging protocols in obtaining good quality images that can permit a confident diagnosis of AAS. AD is the most commonly encountered AAS and also the one with maximum potential to cause catastrophic outcome if not diagnosed and managed promptly. Hence, this review briefly addresses certain relevant clinical perspectives on this condition. Differentiating the false from the true lumen in AD is often essential; a spectrum of CT findings, e.g., “beak sign”, aortic “cobwebs” that allows such differentiation have been described with explicit illustrations. The value of non enhanced CT scans, especially useful in the diagnosis of an intramural hematoma has also been illustrated. Overlap in the clinical and imaging features of the various conditions presenting as AAS is not unusual. However, on most instances MDCT enables the right diagnosis. On select occasions MRI or trans-esophageal echocardiography may be required as a problem solving tool.     

Percutaneous drainage of psoas abscess under real-time computed tomography fluoroscopic guidance

Objectives  The goal of our study was to determine the usefulness of percutaneous abscess drainage under guidance of computed tomography (CT) fluoroscopy. Materials and methods  Our subjects were 21 patients (seven women, 14 men; mean age 64 years; age range 30–87 years) who had undergone percutaneous drainage of 26 psoas abscess lesions under CT fluoroscopic guidance between May 2001 and January 2008. Drainage methods involved a needle puncture, insertion of a guidewire, serial dilations, and the exchange of the needle with a drainage tube. The procedures were guided by use of a helical CT scanner that provided real-time fluoroscopic reconstruction. Results  Percutaneous drainage under real-time CT fluoroscopic guidance was successfully performed in every procedure. Use of real-time CT fluoroscopy allowed rapid assessment of needle, guidewire, and catheter placement. No patient had serious complications related to the drainage procedure. The mean procedure time required to drain one lesion was 35.6 ± 13.6 min. Mean period after the drainage procedure until complete disappearance of the abscess as confirmed by CT was 12.4 ± 10.0 days (range 3–46 days). Conclusion  CT fluoroscopy is useful in achieving accurate and safe drainage of abnormal psoas fluid collections.     

Intraperitoneal tuberculous abscess: Computed tomography features

AIM: To evaluate the computed tomography (CT) features of intraperitoneal tuberculous abscess (IPTA). METHODS: Eight patients with IPTA confirmed by pathology were analyzed retrospectively. The clinical symptoms, medical images, and surgical findings were evaluated. Involvement of the intestine, peritoneum, viscera, and lymph nodes was also assessed. RESULTS: All 8 patients had a history of abdominal discomfort for 1 to 6 mo. Physical examination revealed a palpable abdominal mass in 6 patients. Three patients had no evidence of pulmonary tuberculosis (TB). All IPTAs (11 abscesses) were seen as a multiseptated, peripherally enhanced, hypodense mass with enlarged, rim-enhanced lymph nodes. The largest abscess diameter ranged from 4.5 cm to 12.2 cm. CT showed 2 types of IPTA: Lymph node fusion and encapsulation. Of the 8 patients, one had liver tuberculosis and one had splenic and ovarian tuberculosis. Two cases showed involvement of the terminal ileum and ileocecal junction. Ascites were found in 4 cases. Three patients had peritonitis and mesenteritis. Three patients showed involvement of the omentum. Three patients had histological evidence of caseating granuloma, and 5 had histological evidence of acid-fast bacilli. CONCLUSION: CT is crucial in the detection and characterization of IPTA. Certain CT findings are necessary for correct diagnosis.     

Utility of computed tomography in the diagnosis of thoracic aneurysm in childhood

For an unusual case of saccular aneurysm of the thoracic aorta in a child, the computed tomographic demonstration of a totally vascular mass led directly to the definitive diagnosis by angiocardiography and eliminated the need for many additional imaging or chemical tests. This case illustrates how computed tomography can be beneficial in the potentially difficult diagnostic evaluation of pediatric medistinal masses.     

Advances in determining abdominal aortic aneurysm size and growth

Abdominal aortic aneurysm is a common pathology in the aging population of the developed world which carries a significant mortality in excess of 80% in case of rupture. Aneurysmal disease probably represents the only surgical condition in which size is such a critical determinant of the need for intervention and therefore the ability to accurately and reproducibly record aneurysm size and growth over time is of outmost importance. In the same time that imaging techniques may be limited by intra- and inter-observer variability and there may be inconsistencies due to different modalities [ultrasound, computed tomography (CT)], rapid technologic advancement have taken aortic imaging to the next level. Digital imaging, multi-detector scanners, thin slice CT and most- importantly the ability to perform 3-dimensional reconstruction and image post-processing have currently become widely available rendering most of the imaging modalities used in the past out of date. The aim of the current article is to report on various imaging methods and current state of the art techniques used to record aneurysm size and growth. Moreover we aim to emphasize on the future research directions and report on techniques which probably will be widely used and incorporated in clinical practice in the near future.     

Giant congenital intrapericardial left atrial aneurysm diagnosed by contrast-enhanced computed tomography

A left atrial aneurysm is a rare cardiac anomaly. The etiology is usually congenital, but it can also occur as an acquired pathology secondary to mitral valve disease or a degenerative process. We report a case which, on routine PA chest radiography, presented as cardiomegaly with a bulge on the left cardiac contour. Further evaluation by contrast-enhanced computed tomography proved it to be caused by a large left atrial aneurysm.     

Assessment of sub-milli-sievert abdominal computed tomography with iterative reconstruction techniques of different vendors

AIM: To assess diagnostic image quality of reduced dose (RD) abdominal computed tomography (CT) with 9 iterative reconstruction techniques (IRTs) from 4 different vendors to the standard of care (SD) CT. METHODS: In an Institutional Review Board approved study, 66 patients (mean age 60 ± 13 years, 44 men, and 22 women) undergoing routine abdomen CT on multi-detector CT (MDCT) scanners from vendors A, B, and C (≥ 64 row CT scanners) (22 patients each) gave written informed consent for acquisition of an additional RD CT series. Sinogram data of RD CT was reconstructed with two vendor-specific and a vendor-neutral IRTs (A-1, A-2, A-3; B-1, B-2, B-3; and C-1, C-2, C-3) and SD CT series with filtered back projection. Subjective image evaluation was performed by two radiologists for each SD and RD CT series blinded and independently. All RD CT series (198) were assessed first followed by SD CT series (66). Objective image noise was measured for SD and RD CT series. Data were analyzed by Wilcoxon signed rank, kappa, and analysis of variance tests. RESULTS: There were 13/50, 18/57 and 9/40 missed lesions (size 2-7 mm) on RD CT for vendor A, B, and C, respectively. Missed lesions includes liver cysts, kidney cysts and stone, gall stone, fatty liver, and pancreatitis. There were also 5, 4, and 4 pseudo lesions (size 2-3 mm) on RD CT for vendor A, B, and C, respectively. Lesions conspicuity was sufficient for clinical diagnostic performance for 6/24 (RD-A-1), 10/24 (RD-A-2), and 7/24 (RD-A-3) lesions for vendor A; 5/26 (RD-B-1), 6/26 (RD-B-2), and 7/26 (RD-B-3) lesions for vendor B; and 4/20 (RD-C-1) 6/20 (RD-C-2), and 10/20 (RD-C-3) lesions for vendor C (P = 0.9). Mean objective image noise in liver was significantly lower for RD A-1 compared to both RD A-2 and RD A-3 images (P < 0.001). Similarly, mean objective image noise lower for RD B-2 (compared to RD B-1, RD B-3) and RD C-3 (compared to RD C-1 and C-2) (P = 0.016). CONCLUSION: Regardless of IRTs and MDCT vendors, abdominal CT acquired at mean CT dose index volume 1.3 mGy is not sufficient to retain clinical diagnostic performance.     

Discrepancies in determination of abdominal aortic aneurysms maximum diameter and growth rate,using axial and orhtogonal computed tomography measurements

Purpose

Maximum diameter and growth rate of abdominal aortic aneurysms (AAAs) which are currently used as the only variables to set the indication for elective repair are recorded through computed tomography (CT) measurements on an axial plane or on an orthogonal plane that is perpendicular to vessel centerline, interchangeably. We will attempt to record possible discrepancies between the two methods, identify whether such differences could influence therapeutic decisions and determine in which cases this should be expected.

Materials and methods

We retrospectively reviewed sixty CT-scans performed in thirty-nine patients. Three-dimensional reconstruction of AAAs has been performed and differences in maximum diameter measured on axial and orthogonal planes were recorded. A measure for asymmetry was introduced termed ShapeIndex defined as the value of section minor over major axis and was related with differences in maximum diameter recordings. Growth rates were also determined using both axial and orthogonal measurements.

Results

Axial measurements overestimate maximum diameter by 2 ± 2.7 mm (P < 0.001) with a range of 0–12.3 mm. Overall, 20% of the CTs had an axial maximum diameter >5.5 cm indicating the need for intervention whereas, orthogonal diameter was below that threshold. Asymmetry of the axial sections with ShapeIndex ≤ 0.8 was found to be related to an overestimation of maximum diameter by >5 mm. There were no significant differences in growth rates when determined using orthogonal or axial measurements in both examinations (median growth rate: 2.3 mm and 3.3 mm respectively P = 0.2). However there were significant differences when orthogonal measurements were used at initial and axial measurements used at follow-up examination or vice versa (median growth rate: 4.9 mm and 0.9 mm respectively P < 0.001).

Conclusions

Although the mean difference between measurements is low there is a wide range among cases, mainly observed in asymmetrical AAAs. ShapeIndex may identify those which are more likely to be misestimated. CT measurements performed to establish AAA growth rates should consistently use either the axial or orthogonal technique to avoid inaccuracies from occurring.     

The role of computed tomography in the diagnosis and management of clinically occult post-traumatic small bowel perforation

PurposeTo evaluate the use of computed tomography [CT] in the diagnosis of occult post-traumatic small bowel perforation and to discuss the role of CT in the management of this patient group.MethodThis review includes three patients who presented with mild abdominal symptoms following minor blunt abdominal trauma. Initial radiographs and laboratory investigations were unremarkable but their symptoms failed to resolve and contrast-enhanced CT was performed for further evaluation.ResultsIn each case the CT appearances were indicative of localised small bowel perforation, with no evidence of other visceral injury. In two patients pockets of free intraperitoneal air were present closely related to the second part of the duodenum suggesting injury at this site. In the third case, a thickened proximal jejunal loop was demonstrated with free air and fluid in the adjacent mesentery consistent with a focal perforation. These CT findings were subsequently confirmed at laparotomy.ConclusionCT is an accurate diagnostic tool in the assessment of clinically and radiologically occult traumatic small bowel injury. The use of CT should be considered in patients who have unresolving abdominal symptoms even after apparently insignificant abdominal trauma.     

Endovascular stent graft repair of abdominal aortic aneurysms: Current status and future directions

Endovascular stent graft repair of abdominal aortic aneurysm (AAA) has undergone rapid developments since it was introduced in the early 1990s. Two main types of aortic stent grafts have been developed and are currently being used in clinical practice to deal with patients with complicated or unsuitable aneurysm necks, namely, suprarenal and fenestrated stent grafts. Helical computed tomography angiography has been widely recognized as the method of choice for both pre-operative planning and post-operative follow-up of endovascular repair (EVAR). In addition to 2D axial images, a number of 2D and 3D reconstructions are generated to provide additional information about imaging of the stent grafts in relation to the aortic aneurysm diameter and extent, encroachment of stent wires to the renal artery ostium and position of the fenestrated vessel stents. The purpose of this article is to provide an overview of applications of EVAR of AAA and diagnostic applications of 2D and 3D image visualizations in the assessment of treatment outcomes of EVAR. Interference of stent wires with renal blood flow from the hemodynamic point of view will also be discussed, and future directions explored.